rf circuits, systems, and wireless communications standards

1

RF Circuits, Systems, and Wireless Communications Standards

Prof. Jenshan LinUniversity of Florida

[email protected] or [email protected]://www.rfsoc.ece.ufl.edu/

About the Instructor

• Joined UF in July 2003.• Worked in industry for 9 years.

– AT&T/Lucent Bell Labs (1994-2001)– Agere Systems (2001-2003)

• RF/high-speed circuit/system design for wireless and broadband communications.– antennas, transceivers, standards, system

specifications, …– Using different technologies from silicon to III-V

2

Professional Activities

• Senior Member, IEEE Microwave Theory and Techniques Society, Solid State Circuits Society, Communications Society, Engineering in Medicine and Biology Society, Standards Association.

• MTT Administrative Committee, elected voting member 2006-2008.

• Members of several conference committees– RFIC TPC Chair 2007 (Hawaii)– RFIC General Chair 2008 (Atlanta)– RWS Finance Chair 2007-2008 (Long Beach, Orlando)– IMS 2007 (Hawaii) Exhibitors Liaison for Taiwan

RWS: Radio and Wireless Symposium. Co-sponsored by MTT and COMSOC.IMS: International Microwave Symposium. Large annual event with exhibition.

Research Projects

• High-Density 3-D Packaging Technology for RF Devices (Air Force Research Lab)

• Hydrogen Sensors and System (NASA)• Wireless Power Transmission (NASA)• Remote Non-contact Cardiopulmonary

Monitoring (Vital Signs Sensing) (NSF)• Bandwidth-Efficient Modulation for High

Speed Interconnect (ITRI)• Low Power Phase Shift Modulator for RF

Subsystem Research (DARPA)

3

Workshop Objectives

• Overall picture of RF/wireless systems• The importance of RF design for system

integration• How to determine RF component-level

specifications from wireless communication standards

Workshop Outline

• Demo of FM Radio Interference• RF Overview• Antenna and Radio Propagation• Wireless Communication Standards• RF Specifications from Standards• RF Transceiver Architectures• Reference Transceiver Design Example• Answers to the FM Radio Interference

4

What is RF?

Radio Frequency Bands - IEEE

• IEEE: (A) The frequency in the portion of the electromagnetic spectrum that is between the audio-frequency portion and the infrared portion. (B) A frequency useful for radio transmission. Within this frequency range electromagnetic radiation may be detected and amplified as an electric current at the wave frequency.(loosely defined)

5

Radio Frequency Bands - FCC

FCC: The radio spectrum is the part of the natural spectrum of electromagnetic radiation lying between the frequency limits of 9 kHz and 300 GHz.

Military Radar Bands(IEEE Standard 521-1984)

75-110 GHzW

40-75 GHzV

27-40 GHzKa

18-27 GHzK

12-18 GHzKu

8-12 GHzX

4-8 GHzC

2-4 GHzS

1-2 GHzL

300-1000 MHzUHF

30-300 MHzVHF

3-30 MHzHF

FrequencyRadar Band

6

ITU Bands

Millimeter-wave(mm-wave)

ITU: International Telecommunication Union, headquartered in Geneva, Switzerland is an international organization within the United Nations System where governments and the private sector coordinate global telecom networks and services.

Definition of Microwave

• American Heritage Dictionary:A high-frequency electromagnetic wave, one millimeter to one meter in wavelength, intermediate between infrared and short-wave radio wavelengths. 300MHz to 300GHz

• IEEE Standard Dictionary: A term used rather loosely to signify radio waves in the frequency range from about 1GHz upwards.

• NTIA (National Telecommunications and Information Administration): Loosely, an electromagnetic wave having a wavelength from 300 mm to 10 mm (1 GHz to 30 GHz).

7

So, what is RF?What is Microwave?

What is Millimeter-wave?

Household Electronics

L1: 1,575.42MHz, L2: 1,227.60MHzGPS

~2.45GHzMicrowave Oven

~2.45, ~5.2GHzWireless LAN

800-900MHz, 1.8-2 GHzCellular phone

46, 49, 900MHz, 2.45GHzCordless phone

54-890 MHzTV/Cable Ch. 2-83

88-108 MHzFM radio

3-30 MHzShort Wave (SW) radio

535-1605 kHzAM radio

Frequency RangeEquipment

8

Why use RF?

Baseband transmission v.s. RF transmission

• Through the wire: no problem, as long as the signal bandwidth does not exceed the wire’s bandwidth limit.

• Through the air: How? Need antenna. How big is the antenna? Hint: dipole antenna’s length is usually ½ λ.

• Need to modulate on to a high frequency carrier. • Frequency ↑ Antenna size ↓

9

Why use Microwave?Why use Millimeter-wave?

Why use integrated circuits?

10

RF component evolution

• Waveguide component• Connectorized module• RFIC package

Acronyms

• RFIC: Radio Frequency Integrated Circuit• MMIC: Monolithic Microwave Integrated Circuit• MIC: Microwave Integrated Circuit

Integrate microwave transistors, passive elements, and transmission lines on a microwave substrate. A departure from old microwave waveguide components.

11

Who control RF spectrum?(Spectrum Regulation)

Federal Communications Commission (FCC)

• FCC is an independent United States government agency, directly responsible to Congress. The FCC was established by the Communications Act of 1934 and is charged with regulating interstate and international communications by radio, television, wire, satellite and cable. The FCC's jurisdiction covers the 50 states, the District of Columbia, and U.S. possessions.

• http://www.fcc.gov

12

FCC Organizations

• Five Commissioners appointed by the President and confirmed by the Senate for 5-year terms, except when filling an unexpired term.

• The Commission staff is organized by function. There are six operating Bureaus and ten Staff Offices. The Bureaus’responsibilities include: processing applications for licenses and other filings; analyzing complaints; conducting investigations; developing and implementing regulatory programs; and taking part in hearings. The Offices provide support services.

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FCC Wireless Telecommunications Bureau

• The Wireless Telecommunications Bureau (WTB) handles nearly all FCC domestic wireless telecommunications programs and policies. Wireless communications services include Amateur, Cellular, Paging, Broadband PCS, Public Safety, and more.

Cellular and Broadband PCS

• Cellular band: 824-849 MHz and 869-894 MHz.• PCS band: 1850-1990 MHz.

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FCC Radio Spectrum

• In the United States, regulatory responsibility for the radio spectrum is divided between the FCC and the National Telecommunications and Information Administration (NTIA). FCC, administers spectrum for non-Federal government use and the NTIA, which is an operating unit of the Department of Commerce, administers spectrum for Federal government use. Within the FCC, the Office of Engineering and Technology (OET) provides advice on technical and policy issues pertaining to spectrum allocation and use. OET also maintains the FCC's Table of Frequency Allocations.

• http://www.fcc.gov/oet/spectrum/

FCC and ITU

• The International Telecommunication Union (ITU), headquartered in Geneva, Switzerland is the international organization within which governments coordinate global telecom networks and services. TheUnited States is a member of the ITU. The ITU maintains the [International] Table of Frequency Allocations, which is reproduced in columns 1-3 of the FCC's Table of Frequency Allocations. The FCC and the NTIA assist the Department of State in developing U.S. proposals to revise the ITU's Table of Frequency Allocations.

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FCC Rules – CFR 47

• FCC rules are located in Title 47 of the Code of Federal Regulations. Although the Office of Engineering and Technology (OET) is responsible for the maintenance of FCC rules located inParts 2, 5, 15, and 18 of the Title, the official rules are published and maintained in the Federal Register.

• http://wireless.fcc.gov/rules.html• Part 2: Frequency allocations and radio treaty matters; general

rules and regulations • Part 5: Experimental radio service (other than broadcast) • Part 15: Radio frequency devices• Part 18: Industrial, scientific, and medical equipment

ISM Bands

§ 18.107 Definitions. (c) Industrial, scientific, and medical (ISM) equipment. Equipment or appliances designed to generate and use locally RF energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunication.

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FCC Safety

• FCC is required by the National Environmental Policy Act of 1969 to evaluate the effect of emissions from FCC-regulated transmitters on the quality of the human environment. At the present time there is no federally-mandated radio frequency (RF) exposure standard. However, several non-government organizations, such as the American National Standards Institute (ANSI), the Institute of Electrical and Electronics Engineers, Inc. (IEEE), and the National Council on Radiation Protection and Measurements (NCRP) have issued recommendations for human exposure to RF electromagnetic fields.

RF Safety Guidelines (old)

INIRC: International Non-Ionizing Radiation Committee

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IEEE RF Safety Guideline (new)

Controlled Environment ≈ industryUncontrolled Environment ≈ publicReference: http://www.arrl.org/news/rfsafety/hbkrf.html

RF Safety – some numbers

• Sets limit from 3kHz to 300GHz.• In general, controlled environment allows higher power

than uncontrolled environment (public) except for >12GHz and <20MHz(H-field) or <1.2MHz(E-field).

• Above 100MHz, safety limit for E-field and H-field radiation are the same.

• Below 100MHz, E-field radiation has lower power density limit than H-field radiation.

• Most stringent limit is 0.2mW/cm2 between 30MHz-100MHz, in public environment.

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RF Safety – low frequency

• At 10MHz, the limit is 2mW/cm2 for E-field and 100mW/cm2 for H-field.

• At 1MHz, the limit is 100mW/cm2 for E-field and 10W/cm2

for H-field.• For inductive coupling, e.g., RFID, H-field is dominant.• The RF penetration depth (field intensity drops 50% from

boundary) of muscle tissue is ~15cm@10MHz, ~5cm@100MHz.

Questions:

• How to do the conversion between field intensity and power density?

• Why the RF safety sets the lowest limit for 30MHz-300MHz?

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Antenna

What is an antenna?

• An antenna is a device for radiating or receiving radio waves.

• A transitional structure between free space and a guiding device.

• It converts radiated waves into guided waves, or vice versa.

Antenna

Circuit

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Antenna examples

• Dipole antenna• Monopole antenna• Patch antenna• Horn antenna• Reflector antenna (dish, parabolic)• Yagi-Uda Antenna (VHF, UHF TV)• Phase array antenna

Important notes about antenna

• Antenna is reciprocal. – An antenna can be used for either transmitting or

receiving. – Therefore, in general, only one antenna is needed for

the wireless transceiver (cellular phone, WLAN…), if the transmit and receive frequencies are close enough and within antenna bandwidth.

21

Antenna radiation pattern

• A graphical representation of the radiation intensity of the antenna as a function of space coordinates, in most cases, directional coordinates (angle).

3-D radiation pattern

22

Isotropic antenna

• A hypotheticalantenna having equal radiation in all directions.

• However, in system design and calculation, isotropic antenna is usually used.

Directional antenna

• Having the property of radiating or receiving signal more effectively in some directions than in others.

• Non-isotropic.

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Omnidirectional antenna

• Having a non-directional pattern in azimuth and a directional pattern in elevation.

• Example: Dipole

E-plane and H-plane patterns

• E-plane pattern=the plane containing the electric-field vector and the direction of maximum radiation.

• H-plane pattern= the plane containing the magnetic-field vector and the direction of maximum radiation.

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E-plane and H-plane patterns

x

y

z

E-plane H-plane

y

z

x

y

Polarization

• Polarization of an antenna=the polarization of the radiated wave, when the antenna is excited.– Linear polarization– Circular polarization

• RHCP (right-hand circular polarization)• LHCP (left-hand circular polarization)

– Elliptical polarization

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Far-field and Near-field Regions

D

R

Near-field regionFar-field region

R > 2D2/λ

D = largest dimension of the antenna

Far-Field Region:Angular field distribution (antenna pattern) is essentially independentof the distance from the antenna.

for D >> λ

R >> D for D ~ λ

Radiation Intensity

– U = radiation intensity (W/unit solid angle)– Wrad = radiation density (W/m2)– Radiation intensity of an isotropic source

ππ 44 22

0radrad P

rPrU =

××=

r

Prad

radWrUEIRP

××=×=

244ππ

Effective Isotropic Radiated Power

radWrU ×= 2

π4EIRPU =

26

Directivity

• Directivity Gain=the ratio of the radiation intensity in that direction to the radiation intensity of an isotropic antenna

• Directivity=the maximum directivity gainradrad

g PEIRP

PU

UUD ),(),(4),(),(

0

φθφθπφθφθ =×

==

radPU

UUD max

0max 4 ×

==π

Antenna gain and efficiency

• Antenna gain=the ratio of EIRP to the input power

• Antenna efficiency=the ratio of total radiated power to the input power

inin PU

PEIRPG ),(4 φθπ ×

==

),(),(4),( φθφθπφθ grad

DePUeG ×=

××=

inradP

Pe =

27

Dipole Antenna

Transmission line

Directivity = 1.5 for short dipole

Directivity = 1.64 for ½λ dipole

(1.76 dB)

(2.15 dB)

Antenna Efficiency

• Loss– Reflection due to mismatch between transmission

line and antenna– I2R loss (conduction and dielectric)

• Total overall efficiency:

cddcrt eeeee ×Γ−=××= )1( 2

Reflection Conduction dielectricConduction-Dielectric efficiency

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Antenna input impedance

• The impedance measured at the input port of the antenna.

RL

Rr

XA

cde

Antenna reactance

Radiation resistance

loss

ALrA jRRZ Χ++=

=+

=Lr

rcd RR

Re Power delivered to Rr

Power delivered to Rr and RL

Radiation resistance of dipole

Infinitesimal dipole L<λ/50

L

Short dipole L<λ/3

½ λ dipole L=λ/2

222 )(790)(80λλ

π LLRr ×=××=

222 )(197)(20λλ

π LLRr ×=××=

Ω= 73rR

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Antenna aperture

• Effective aperture. Could be much larger than the actual physical aperture.

• The ratio of the power delivered to the load to the incident power density.

iTT

iT

e WRI

WPA

2/2==ZT

TTT jRZ Χ+=

RL

Rr

XA

+VTRT

XT

IT

AntennaLoad

30

⎥⎥⎦

⎤

⎢⎢⎣

⎡

++++= 22

2

)()(2 TATLr

Ti

Te

XXRRRR

WV

A

Under conditions of maximum power transfer (conjugate matching):

TLr RRR =+ TA XX −=

⎥⎦

⎤⎢⎣

⎡+

=⎥⎥⎦

⎤

⎢⎢⎣

⎡

+=

rLiT

rL

Ti

Tem RRW

V

RRR

WV

A 18)(8

2

2

2Maximum effective aperture

⎥⎦

⎤⎢⎣

⎡=

riT

em RWV

A 18

2

Maximum effective aperture of an infinitesimal dipolewith RL=0

dipole is very short LEVT ×=

Induced voltage E-field of incident wave

Antenna length

Incident power densityη×

=2

2EWi Ω= 377ηL

Lπλ

λπη 83

)/80)(2/(8)( 2

2222

2==

LEELAem

(120π)

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Antenna 2

RX

Antenna 1

TX

R

mA1 mA21D 2D

00

),(WW

UUD i

g ==φθ

rememberiW Radiation density (W/m2)

Isotropic

rPtP

21

104 R

DPDWW gt

giπ

=×=

221

4 R

ADPAWP gt

rirπ

=×=

)4( 221 R

PPAD

tr

g π=

1A 1gD 2A 2gD

Antenna 1

RX

Antenna 2

TX

R

mA1mA2 1D2D

Switch Antenna 1 and Antenna 2 tW Radiation density (W/m2)

rPtP

22

204 R

DPDWW gt

giπ

=×=

212

4 R

ADPAWP gt

rirπ

=×=

)4( 212 R

PPAD

tr

g π=

1A 1gD2A 2gD

Notes:1. Antenna is reciprocal.2. Transmission medium is linear and passive.

32

)4( 221 R

PPAD

tr

g π=

)4( 212 R

PPAD

tr

g π=

2

2

1

1A

DA

D gg =

mm AD

AD

22

11 =

If antenna 1 is isotropic, 11 =D2

21 D

AA mm =

If antenna 2 is infinitesimal dipole, πλ

83 2

2 =mA 5.12 =D

πλ4

21 =mA DAem π

λ4

2=

(Maximum) effective aperture of isotropic antenna

for any antenna

Antenna 2

RX

Antenna 1

TX

R

tW Radiation density (W/m2)

rPtP

24 RAGPAWP rmtt

rtrπ

=×=

rtrtrmt

tr GG

RG

RG

RAG

PP 2

2

22 )4

()4

()4()4( π

λπ

λ

ππ===

Consider the loss (antenna efficiency)DeG ×=

tG rG

GeDAem πλ

πλ

44

22==

If maximum directivity aligned:

rttr GG

RPP 2)

4(

πλ

= Friis Transmission Equation

Free Space Path Loss Equation

33

Don’t forget the IM part!

A closer look at finite length dipole

Dipole’s radiation pattern, directivity, and radiation resistance

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Cellular Base Station Antenna

Why the antennas were designed this way?

Antenna Array

• Radiation pattern from a single antenna is relatively wide.

• Notice that directivity increases as antenna size (electrical size) increases.

Dipole antenna

2L

L ↑

35

Antenna Array

• Another way to increase antenna size is to repeat single elements – array.

Far-fieldFar-field

Antenna Array

Radiation Pattern ?

x

y

z

36

Cell Sectors

12

3

120°

120°

120°

Advantages of Antenna Array

• Higher directivity (higher gain).• Control the phase to steer the beam – phased

array.• Control the phase and amplitude – beam forming

array.

37

RF Propagation

RF Propagation

• Free space path loss equation:Relates the power received to the power transmitted between two antennas separated by a distance R>2D2/λ (far field)

• Sometimes called Line of Sight (LOS)• Reflection, Diffraction, Scattering will change the

propagation loss – complicated models.• Either higher or lower loss is possible.

rttr GG

RPP 2)

4(

πλ

=

38

Free Space Path Loss

2

2

2

4

44

⎟⎠⎞

⎜⎝⎛⋅⋅⋅=

⋅⋅⋅=

RGGP

GGR

PP

rtt

rtt

r

πλ

πλ

π

( ) ( ) ( ) ( )2

4log10 ⎟

⎠⎞

⎜⎝⎛+++=

RGGPP dBrdBtdBmtdBmr π

λ

04

log102

<⎟⎠⎞

⎜⎝⎛

Rπλ

Far-field

04log204log102

>⎟⎠⎞

⎜⎝⎛=⎟

⎠⎞

⎜⎝⎛≡

λπ

λπ RR

Free Space Path Loss

RF attenuation

dB/km

Notice the peak and dip of O2 curve at 60GHz and100GHz, respectively.

39

dB

94GHz

Attenuation due to rain

Problem at high frequency,e.g., satellite TV.

40

Ground Reflection

Assuming d>> h

d1

d2

dhh

dhhdhhdd

rt

rtrt2

)()( 222212

≅∆

+−−++=−=∆

∆== ∆∆ λ

πωθ 2ccPhase difference due to time delay:

41

ηπ 2

2

4 2EGW tr

Pi

t ==

rdE

rE tttt GP

rGP 00

242 1

2 ≡== πη

πη

)(

200)(

100 21

cd

ccd

c tjtjtotal e

ddEe

ddEE −− Γ+= ωω

]1[ )()(00 211c

dcd

ccd

c jtjtotal ee

ddEE −− Γ+= ωω

]1[ )()(00 1ccc

dc jtj

total eeddEE

∆−− Γ+= ωω

)]sin(cos1[)(00 1

∆∆− −Γ+= θθω je

ddEE c

dc tj

total

21

])sin()cos1[( 2200∆∆ Γ+Γ+= θθ

ddEEtotal

21

])sin()cos1[( 2200∆∆ Γ+Γ+= θθ

ddEEtotal

])sin()cos1[(42

222

2∆∆ Γ+Γ+== θθ

πη dGPE

W tttotali

)cos21(42

22

2Γ+Γ+== ∆θ

πη dGPE

W tttotali

1=Γ

1−=Γ

)(cos22

)cos1(2 2

222

∆=+= ∆θ

πθ

π dGP

dGPW tttt

i

)(sin22

)cos1(2 2

222

∆=−= ∆θ

πθ

π dGP

dGPW tttt

i

42

1=Γ )(cos 22

2∆= θ

πdGPW tt

i

2dGPW tt

iπ

≅Assuming d>> h

22

2 )2

(4 d

GGPGdGPAWP rttr

ttemir π

λπ

λ

π===

1−=Γ )(sin 22

2∆= θ

πdGPW tt

i

Assuming d>> h

24

22

24 )(4

)(4rt

rttrrt

ttemir hh

dGGPGhh

dGPAWP ===

πλ

λ

π

244

222

222 )()()( 2

2

rtttrttttt

i hhdGP

dhh

dGP

dGPW

λπ

λπθ

πππ==≅ ∆

40dB/decade

λ disappearedHigher path loss than free spaceIndependent of frequency at large d

4 times offree space

Building a radio system…

RX

Very weak signal. To process the signal at baseband, we need large signal whiletrying to maintain the best signal to noise ratio.

Channel

TX

43

Wireless Communication Standards

Wireless v.s. Wire

Media

RF Wireless

Twisted Pair(Wire)

Optical Fiber

Bandwidth Example

Cable(Wire)

kHz, MHz, GHz

kHz

GHz

MHz

Cellular, WLAN, UWB

phone, ISDN

Very high speed data

analog video, digital

MHz DSL, Ethernet

44

Wireless Communication Standards

• Mobile Communication – licensed bands• Wireless LAN – unlicensed bands• Bluetooth - unlicensed bands• Fixed Wireless Link (MMDS, LMDS) – licensed bands• UWB (Ultra Wide Band) – unlicensed band• Others

Wireless Communications StandardsAnalog Cellular Telephones

Standard AMPS/NAMPSNarrow Band AdvancedMobile Phone System

TACSTotal Access

Communication System

NMTNordic Mobile

TelephoneMobile Frequency

Range (MHz)Rx: 869-894Tx:: 824-849

ETACS:Rx: 916-949Tx: 871-904

NTACS:Rx: 860-870Tx: 915-925

NMT-450:Rx: 463-468Tx: 453-458NMT-900

Rx: 935-960Tx:: 890-915

Multiple AccessMethod

FDMA FDMA FDMA

Duplex Method FDD FDD FDD

Number ofChannels

AMPS: 832NAMPS: 2496

ETACS: 1240NTACS: 400

NMT-450: 200NMT-900: 1999

Channel Spacing AMPS: 30 kHzNAMPS: 10 kHz

ETACS: 25 kHzNTACS: 12.5 kHz

NMT-450: 25 kHzNMT-900: 12.5 kHz

Modulation FM FM FM

Channel Bit Rate n/a n/a n/a

Downlink/Uplink

45

Wireless Communications StandardsDigital Cellular Telephones

TDMAIS-54/136 Time Division

Multiple Access

CDMAIS-95 Code Division

Multiple Access

GSMGlobal System for

Mobile Communications

DCS 1800Digital Communication

System

PDCPersonal Digital

CellularRx: 869-894Tx:: 824-849

Rx: 869-894Tx:: 824-849

Rx: 935-960Tx:: 890-915

Rx: 1805-1880Tx:: 1710-1785

Rx: 810-826Tx:: 940-956

Rx: 1429-1453Tx:: 1477-1501

TDMA/FDM CDMA/FDM TDMA/FDM TDMA/FDM TDMA/FDM

FDD FDD FDD FDD FDD

832(3 users/channel)





30 kHz 1250 kHz 200 kHz 200 kHz 25 kHz

π/4 DQPSK QPSK/OQPSK GMSK(0.3 Gaussian Filter)

GMSK(0.3 Gaussian Filter)

π/4 DQPSK

48.6 kb/s 1.2288 Mb/s 270.833 kb/s 270.833 kb/s 42 kb/s

Multiple access/Multiplexing

Wireless Communications StandardsPersonal Communication Systems

PCS

Rx: 1930-1990 Tx: 1850-1910 PCS TDMA

(based on IS-136 cellular)

PCS CDMA (based on IS-95 cellular)

PCS 1900

(based on GSM cellular)

Wideband CDMA

46

Downlink and Uplink

Downlink

Uplink

Downlink: mobile RX, base station TXUplink: mobile TX, base station RXRX: receiveTX: transmit

Multiple Access v.s. MultiplexingMultiple Access:Frequency Division Multiple Access (FDMA)Time Division Multiple Access (TDMA)Code Division Multiple Access (CDMA)Space Division Multiple Access (SDMA), Polarization Division Multiple Access (PDMA)Carrier Sense Multiple Access (CSMA)

Remote sharing of a communication resource, e.g. satellite, base station.

Multiplexing:Frequency Division Multiplexing (FDM)Time Division Multiplexing (TDM)

Sharing a communication resource at a local site, e.g. circuit board, antenna.

47

Example: GSM

TDMA - 8 users/channel

BTS (Basestation Transceiver System)

Mobile

Multiple Access:sharing a dynamically changedcommunication resource.

Multiplexing:sharing a fixed or slowly changed communication resource.

Ch. nCh. 2Ch. 1

935.2 MHz890.2 MHz

935.4 MHz890.4 MHz

Each transmit/receive unit carries one channel

FDM

0.577mS

4.615mSBTS

Simplex: Provide only one-way communication.Half Duplex:Provide two-way communication by using the same radio channel for both transmission and reception, but the ‘user’ can only either transmit or receive at a time. An example is the two-way radio you can buy from Radio Shack.Full Duplex:Simultaneous two-way communication, and the ‘user’ can transmit and receive at the same time. An example is the cellular phone.Typically on two different channels (FDD) but some new digital systems are using TDD in which transmission and reception share a single radio channel.FDD: Frequency Division Duplexing, TDD: Time Division Duplexing

How does a TDD work in Full Duplex?When radio channel’s data rate is much higher than user’s data rate, digital radio can store information bursts in-time to appear like full duplex to end user. Sensitive to timing, so only for in-door or small area applications like cordless or wireless LAN.

Duplex

48

FDD v.s. TDD

Duplexer

Switch

Receiver

Receiver

Transmitter

Transmitter

FDD

TDD

Wireless Communications StandardsAnalog Cordless Telephones

CT0 Cordless Telephone 0

JCT Japanese Cordless Telephone

CT1/CT1+ Cordless Telephone 1

2/48 (U.K.), 26/41 (France) 30/39 (Australia)

31/40 (The Netherlands, Spain) 46/49 (China, S. Korea, Taiwan, USA)

48/74, 45/48 (China)

254/380 CT1: 914/960 CT1+: 885/932

FDMA FDMA FDMA

FDD FDD FDD

10, 12, 15, 20 or 25 89 CT1: 40 CT1+: 80

1.7, 20, 25 or 40 kHz 12.5 kHz 25 kHz

FM FM FM

n/a n/a n/a

49

Wireless Communications StandardsDigital Cordless Telephones

CT2/CT2+Cordless Telephone 2

DECTDigital European Cordless Telephone

PHSPersonal Handy Phone System

CT2: 864/868CT2+: 944/948

1880-1900 1895-1918

TDMA/FDM TDMA/FDM TDMA/FDM

TDD TDD TDD

40 10(12 users/channel)


100 kHz 1.728 MHz 300 kHz

GFSK(0.5 Gaussian Filter)


π/4 DQPSK

72 kb/s 1.152 Mb/s 384 kb/s

Mobile Communication Standards

50

3G Standard(s)

North AmericaEurope Asia/Pacific

Digital Modulation

51

Amplitude Shift Keying (ASK)

Frequency Shift Keying (FSK)

Phase Shift Keying (PSK)

Digital Modulation

(analog counterpart: AM)

(analog counterpart : FM)

(analog counterpart : PM)

QPSK Modulator

I channel

Q channel

52

How QPSK data is encoded

I channel

Q channel

Reference: Sklar, Digital Communications

Signal Space Diagram (Constellation)

(-1,1)(-1,-1)

(1,-1) (1,1)

(dI, dQ)I

Q


53

How OQPSK data is encoded

Also called staggered QPSK (SQPSK)

I channel

Q channel


Non-constant envelope

No transition through zero

QPSK

OQPSK

QPSK and OQPSK waveforms


54

How MSK data is encoded – I


How MSK data is encoded – Q

Combined I and Q waveform:

No discontinuous phase transition!Reference: Sklar, Digital Communications

55

Impact on Power amplifier

• Linear PA is needed for non-constant envelope modulation. • Nonlinear PA can be used for constant envelope modulation.• Nonlinear PA has higher efficiency. • Higher efficiency lower DC power consumption

TX

PA Pou

t (dB

m)

Pin (dBm)

SaturationNonlinear

Comparison of QPSK, OQPSK, and MSK spectra

Normalized frequency offset from carrier, (f-fc)/R (Hz/bit/s)

Nor

mal

ized

pow

er s

pect

ral d

ensi

ty G

(f)

(dB)

MSK is spectrally more efficient than QPSK/OQPSK.


56

Modulator

Baseband

RF


DQPSK (Differential QPSK)

• DPSK: Differentially coherent detection of differentially encoded PSK.• In coherent detection of PSK, signal is compared to a reference

synchronized in phase. Phase has to be aligned. • DPSK is differentially coherent detection – does not require phase

synchronization, but compare to previous phase.• DPSK requires higher bit energy noise ratio than PSK to keep the

same error rate (~3dB higher for 10-1, ~+2dB higher for 10-2 – 10-3, ~1dB higher for < 10-5).

• Reference: – Sklar, Digital Communications, p.149, p.160.– Couch, Digital and Analog Communication systems, p.344.

57

Reference: Couch, Digital and Analog Communication Systems, 6th ed.


Bit Error Rate (BER) Performance

58

FSK

• FSK can be non-coherently detected, in addition to coherent detection.

• No phase synchronization in any kind is needed for non-coherent detection.

• Non-coherent detection FSK receiver is easy to implement – lower complexity, lower cost, lower power.

• Reference: – Sklar, Digital Communications, p. 151.– Couch, Digital and Analog Communication systems, p. 352.


59

QAM (Quadrature Amplitude Modulation)

• APK (Amplitude Phase Keying) – combination of ASK and PSK,

• QASK (Quadrature Amplitude Shift Keying) – ASK in 2-D

Σ

)cos( 0tω

)sin( 0tω

x

y

x

y±1, ±3

±1, ±3

Pulse Shaping and Baseband filter

• Reduce Inter-Symbol Interference (ISI)• Where does it come from?

Reference: Couch, Digital and Analog Communication Systems, 6th ed.

60

Raised Cosine Filter

Wireless LAN Standards

61

Wireless Communications StandardsWireless Data (WAN/LAN)

CDPDCellular Digital Packet Data

(WAN)

RAM - Mobitex (WAN) Ardis - RD - LAP(WAN)

IEEE 802.11Wireless LAN

Rx: 869-894Tx: 824-849

(North America)Rx: 935-941Tx: 869-902

(European/Asia)403-470

Rx: 851-869Tx: 806-824

(North America/Europe)2400-2483

(Japan)2470-2499

FDMA TDMA/FDM TDMA/FDM CSMA

FDD FDD FDD TDD

832 480 720 FHSS: 79DSSS: 11

30 kHz 12.5 kHz 25 kHz FHSS: 1 MHzDSSS: 11 MHz

GMSK(0.5 Gaussian Filter)


FSK(2 and 4 level)

FHSS: GFSK(0.5 Gaussian Filter)

DSSS: DBPSK (1Mb/sDQPSK (2 Mb/s)

19.2 kb/s 8 kb/s 19.2 kb/s 1 or 2 Mb/s

Evolved into a, b, g

Wireless LAN Standards

Standard

Frequency Range(GHz)

Multiple Access

Duplex

Channel Spacing (MHz)

Modulation

Data Rate(Mb/s)

Web site

IEEE 802.11b

2.4-2.4835 (US, Canada, Europe)2.471-2.497 (Japan), 2.4465-2.4835 (France), 2.445-2.475 (Spain)*

CSMA/CA

TDD

5

BPSK, QPSK, CCK

1, 2, 5.5, 11

http://standards.ieee.org/getieee802/802.11.html

IEEE 802.11a

US U-NII5.15-5.35, 5.725-5.825 (300MHz)

CSMA/CA

TDD

20

OFDM/BPSK, QPSK,

16QAM, 64QAM

6, 9, 12, 18, 24, 36, 48, 54

http://standards.ieee.org/getieee802/802.11.html

ETSI HIPERLAN/2

5.15-5.35, 5.470-5.725 (455MHz)

TDMA (centrally scheduled)

TDD

20

OFDM/BPSK, QPSK, 16QAM, 64QAM

6, 9, 12, 18, 27, 36, 54

http://www.etsi.org/technicalactiv/hiperlan2.htm

Japan MMAC

(100MHz)

http://www.arib.or.jp/mmac/

62

History of Wireless LAN

• Research and standardization activities started in late 80’s, blossomed in late 90’s.

• IEEE Workshop on Wireless LANs began in 1991. – the oldest IEEE workshop in wireless broadband local and ad-hoc

networks.

• AT&T WaveLAN and Motorola Altair were the first two commercial wireless LAN products.– AT&T WaveLAN was the first one capable of 2Mb/s

Hollemans and Verschoor, “Performance study of WaveLAN and Altair radio-LANs”Personal, Indoor and Mobile Radio Communications, 1994. Wireless Networks -Catching the Mobile Future. 5th IEEE International Symposium on , Volume: 3 , 18-23 Sep 1994, Page(s): 831 -837 vol.3

63

IEEE 802.11 standards

• IEEE:– Institute of Electrical and Electronics Engineers

• 802.11:– Family of standards by the IEEE to define the

specifications for wireless LANs– Defines:

• Medium Access Control (MAC)• Physical Layer (PHY) Specifications

IEEE 802.11 and the ISO Protocol stack

64

IEEE 802.11b

• ‘b’ in IEEE 802.11b– “High Rate” amendment by the IEEE in September

1999.– Affects the physical layer, basic architecture is the

same• Added two higher speeds

– 5.5 and 11 Mbps• More robust connectivity

• 802.11b has been more popular than 802.11a– also known as Wi-Fi (Wireless Fidelity)

IEEE 802.11b

• Uses Direct Sequence Spread Spectrum (DSSS) or Frequency Hopping Spread Spectrum (FHSS) technology

• Operates in unlicensed 2.4 GHz unlicensed band

• 2.4 GHz to 2.4835 GHz for North America

65

IEEE 802.11b

• Supported data rates and distances– 1, 2, 5.5, 11 Mbps at distances of 150-2000 feet

without special antenna– Greater distances can be achieved by using special

antennas– Distance (or signal strength) greatly depends on

obstructions such as buildings and other objects– Maximum data rate obtained depends on signal

strength

IEEE 802.11a

• Date rate of up to 54 Mbps• 5 GHz (U-NII band) instead of 2.4 GHz

– Unlicensed National Information Infrastructure

• OFDM instead of DSSS for encoding– Orthogonal Frequency Division Multiplexing

66

IEEE 802.11a

• Advantages– higher data rate– less RF interference than 2.4 GHz

• 2.4 GHz used by Bluetooth, cordless/cellular phones, microwave ovens, other unlicensed radios, etc.

• Disadvantages– shorter range, need to increase Access Point (AP)

density or power to compensate the higher free space path loss (same antenna gain as 2.4 GHz).

IEEE 802.11g

• Another high data rate standard but still works at 2.4 GHz

• Moving 802.11a into 2.4 GHz band• Data rate of up to 54 Mbps• Advantages

– RF compatible with 802.11b– better range than 802.11a

• Eventually, 802.11b/g devices dominate.

67

References

• References for WLAN history are posted on the website. Most of them you can download from IEEE website.

• Except Tuch, “Development of WaveLAN, an ISM band wireless LAN”, AT&T Technical Journal, July/August 1993.

• Wireless LAN standards are also posted on class website.

Wireless LAN Physical Layer

68

IEEE 802.11b Physical Layer

• Spread Spectrum– spreads the transmitted signal over a wide range of

spectrum– After de-spreading, interferences are suppressed. – 2 major approaches to spread spectrum:

• FHSS: Frequency Hopping Spread Spectrum• DSSS: Direct Sequence Spread Spectrum


• FHSS– hop to other frequencies at a fixed time interval

using a predetermined sequence– “hopping” allows the system to avoid interferences

• DSSS– a different approach: artificially broaden the

bandwidth needed to transmit a signal by modulating the data with a spreading code

– allows for error detection

69

Spread Spectrum (IS-95)


• 1Mb/s and 2Mb/s– modules the data with an 11-bit sequence called

the Barker code• 10110111000

– modulated sequence is a series of data objects called chips

– chips are sent out by the wireless radio• wireless radio modulates a 2.4 GHz carrier• modulation techniques: DBPSK, DQPSK• 22MHz BW (DSB, null-to-null)

70

10

1 10

1 1 10 0 0

10

1 10

1 1 10 0 0

10

10

1 10

1 1 10 0 0 0

10 0

10 0 0

1 1 1

1 Mb/sInformation

11 Mb/sBarkerCode

SpreadSignal

80211b1.MCD

IEEE 802.11b Physical LayerData

Chips

71


• 5.5Mb/s and 11Mb/s– Use CCK (Complimentary Code Keying) modulation– Spreading code length is 8-complex-chip, not 11-bit– The 8-complex-chip code word pattern changes as data

pattern changes. – The encoding is based on QPSK. Essentially a rotating pattern

on QPSK constellation – just like turning the combination lock on safe.

– At 5.5Mb/s, each “symbol” (each 8-complex-chip code word) contains 4 bits of data.

– At 11Mb/s, each “symbol” (each 8-complex-chip code word) contains 8 bits of data.

– The chip rate is always 11Mchips/s, producing 22MHz RF BW null-to-null.

CCK

73

IEEE 802.11b

FCC: USIC: CanadaETSI: Europe

74

IEEE 802.11b Channel Agility OptionFrequency Hopping Channels for High Rate 5.5Mb/s and 11Mb/s

Half-overlapping: enable interoperability with 1Mb/s and 2Mb/s FH systems

Non-overlapping:

IEEE 802.11b

75

The measurements shall be made using a 100 kHz RBW and 100kHz VBW

IEEE 802.11b

OFDM ConceptOrthogonal Frequency Division Multiplexing

• A special case of multi-carrier transmission.• Split a high-rate datastream into a number of lower rate

streams that are transmitted simultaneously over a number of subcarriers.

• Subcarrier frequencies are “orthogonal.”• Can be viewed as either a modulation technique or a

multiplexing technique.• Robustness against frequency selective fading.• Used in IEEE 802.11 wireless LAN a and g versions.• Use PSK or QAM on each subcarrier.• Reference: Van Nee and Prasad, “OFDM For Wireless Multimedia

Communications”

76

IEEE 802.11a

77

IEEE 802.11a

IEEE 802.11a

78

HIPERLAN/2

79

Same as 802.11aDSSS DBPSK (1 Mb/s)DSSS DQPSK (2 Mb/s)Complimentary code keying (CCK): QPSK (5.5 and 11 Mb/s)

OFDM: QPSK, QAM (0.5 Gaussian filter)OFDM: BPSK (5.5 Mb/s)OFDM: 16QAM, (24, 26 Mb/s)OFDM: 64 QAM (54 Mb/s)

Modulation

Same as 802.11aUS 25 MHz non overlapping (3 channels), 10 MHz, overlapping (6 channels)Europe 30 MHz non overlapping (3 channels), 10 MHz, overlapping (6 channels)

OFDM: 20 MHzChannel Spacing

Same as 802.11a127127Users per Channel

Same as 802.11aTDDTDDDuplex Method

Same as 802.11aCSMA/CACSMA/CAMultiple Access Method

Same band as 802.11b

2.41-2.462 GHz (N. America, 11 channels 1000 mW Power Allowance)2.412-2.472 GHz (Europe, 13 channels 100 mW Power Allowance)Japan: 2.484 GHz (1 channel 10mW/MHz Power Allowance)

5.150– 5.250 GHz(USA U-NII Lower band, channels 36,40,44, and 4825 mW/MHz Max. Tx5.250– 5.350 GHz(USA U-NII Middle band, channels 52, 56, 60,and 6412.5 mW/MHz, Max. Tx5.725– 5.825 GHz(USA U-NII Upper band, channels 149,153,157,16150 mW/MHz Max Tx

Mobile Frequency Range

802.11g802.11b802.11aStandard

BluetoothA wireless connectivity at 2.4 GHz

• Mobile phone with headset

• Mobile phone with PDA

• Mobile phone with computer• Keyboard and mouse

with computer• Computer with printer

• Automobile with mobile phone

80

Bluetooth Radio

Frequency

Output Power

Bluetooth Radio

Modulation: GFSK (Gaussian Frequency Shift Keying)

1

0 <20ppm

81

Receiver Sensitivity: -70dBm with 0.1% BER (Bit Error Rate)

References:http://www.bluetooth.com/http://www.bluetooth.org/

Spurious Emission

The Trend of Wireless Communications

• Voice• Mobility• Wireless

Cellular Internet

Broadband Mobile Internet

• Data• Broadband• High Speed Connection

+ other functions• Bluetooth• GPS• IrDA• Remote controller (TV, VCR)•…

82

RF System Specifications and Parameters

Channel

Propagating medium or electromagnetic path connectingtransmitter and receiver

83

Building a transmitter

Large signal. Cannot interfere with other radio systems!

TX Tx output

Other radio

For transmitter design, a clean output spectrum is the key.

RX

Of course, need to meet output power requirement andget the efficiency as high as possible.

Building a receiver

RX

Very weak signal at RX antenna. To process the signal at baseband, we need large signal while trying to maintain the best signal-to-noise ratio.

Channel

TX

Noise signal

through RF receiver

For receiver design, S/N or S/(N+I)is the key.

What’s wrong here?

84

SNR (Signal-to-noise ratio)

power noisepowersignalSNR =≡

NS S

N• Power ratio

SNR will be degraded due to• Signal loss• Noise increase• InterferenceDegradation is measured by Noise Figure (NF)

outin

SNRSNR

outputat SNRinputat SNRNF =≡

An example of RF system

LO(Synthesizer,PLO, DRO)

BPF BPF

BPF BPFMixer

MixerLNA AGC

IF AMP

IF and/orBase-band

DriverHPA

Duplexer

Antenna

Notes: Duplexer can be two filters back-to-back, a switch, or a circulator…Diplexer refers to a diplex filter separating two frequency bands.

85

An ideal receiverAssuming we have transceivers with perfect components

noiseless linear amplifiers (NF=0dB, IIP3=infinity),noiseless mixers which generate the mixing product you want and no image, no spurs.Perfect frequency source without phase noise or jitter.Lossless filters with infinite out-of-band rejection and extremely sharp roll-off.Of course, they drain no power from battery or power supply.Also, cost nothing and so small.

Then, designing a system would be so easy!

These are the wish list from system engineers.

Unfortunately, none of them is true.

That’s why we need so many RFIC designers in the world.

Non-Ideal RF Componentnoisy and nonlinear

Pin Pout

Pin (dBm)

Pou

t (dB

m) fA, fB

slope

=1

1dB

P1dB

NF

Input noise floor = kTB

Output noise floor

k: Boltzmann’s constant = 1.38x10-23 J/K

T: absolute temperature

B: bandwidth

P1dB, in

P1dB, out

Gain compression

86

3rd Order Intermodulation

fA fB 2fB - fA fB + fA2fA - fBfB - fA

Filter Bandwidth

2nd order2nd order

3rd order3rd order

nonlinear ampfA fB

?1st order

IP3noisy and nonlinear

Pin Pout

Pin (dBm)

Pou

t (dB

m) fA, fB

2fA-fB , 2fB-fA

IP33rd orderIntercept Point

slope

=1

slop

e=3

NF


Output noise floor

IIP3

OIP3

87

How to measure OIP3

Pin (dBm)

Pou

t (dB

m) fA, fB

2fA-fB , 2fB-fA

OIP3

slope

=1

slop

e=3

receiver noise floor

PIM3

Plin

OIP PP P

linlin IM3

23= +

− in dB

Make sure the slope is 3 before you apply this equation!

System Specifications

Now, you have built a non-ideal radio with non-idealcomponents, how do you know if it works?(meets the spec?)

Where did the spec come from?

System specifications came from standards documents.Documents were developed and published by standards organizations.

For example: ITU (International Telecommunication Union)ETSI (European Telecommunications Standards Institute)TIA (Telecommunications Industry Association)(US)

88

System Specifications Example: GSM

Receiver sensitivity

* Published by ETSI

System Specifications Example: GSM

Transmitter output spectrum

* Published by ETSI

30kHz RBW

100kHz RBW

89

System Specifications Example: CDMA IS-95


* Published by TIA

* Published by TIA

Transmitter output spectrum

System Specifications Example: CDMA IS-95

fc Fc+900kHz Fc+1.98MHz

0dBc

-42dBc

-54dBc

Measured in 30kHz RBW

90

System Specifications Example: DECT

Specifications: From system to component

System Component

Reference sensitivity level Rx NF

Reference interference level Rx LO phase noise

Receiver blocking characteristics Rx LO phase noise, Rx spur frommixer

Receiver intermodulationcharacteristics Rx 3rd order intermod

Receiver spurious emissions Rx radiated spur

Transmitter output power Power amplifier output

Output RF spectrum Modulator, Filter, PA

Spurious emissions Tx spur from mixer

91

Receiver Spurious Emissions

• Remember the FM radio demo? The FM receiver did cause interference!

• In GSM Standard (GSM0505), 5.4 defines the receiver spurious emissions.

Circuit Challenges

Rx LNA NF(sensitivity), IP3(intermod)

Rx Mixer IP3(intermod), Spur(blocking)

Rx VCO Phase noise(blocking), jitter(timing)

Tx Modulator Noise floor(output spectrum), Signal balance(I&Q)

Tx Mixer Spur(spurious emission)

Tx AGC Gain control(output power level)

Tx PA Linearity(output spectrum), efficiency

Duplexer Insertion Loss(sensitivity), Rejection(spurious emission)

Transceiver Integration

Isolation/cross-talk, DC Power, Optimized Partition.

Specifications: Circuit Design Issues

92

Link Budget

Link Budget is a term used to determine the necessary parameters for a successful transmission of a signal from a transmitter to a receiver through space.

Includes Tx PA output, gain and loss throughout the systemand link, and the S/N level required at receiver for desiredbit error rate(BER) or detection.

The most simple, basic system specifications analysis to begin with – only gain, loss, noise (linear characteristics).

Link Budget Analysis Example

http://www.ardentech.com/ Download trial version or Lite-version

93

EIPR and ERPEffective Isotropic Radiated Power, or Equivalent Isotropic Radiated Power

EIRP = (power delivered to the antenna) X (antenna gain)

in a given direction

ERP = Effective Radiated Power= (power delivered to the antenna) X

(relative antenna gain with respect to maximum directivity of half-wavelength dipole)

ERP (dB) = EIRP (dB) – 2.15dB

Same EIRP

Link Margin

Difference in dB between (Eb/N0) received and (Eb/N0) required

Bit energy Noise power spectral densityNoise power per Hertz (noise energy)

dBrequired,0

dBreceived,0

dB )()(NE

NEM bb −=

• Varies from one system design to another• Depends on modulation, coding schemes.

94

Bit Error Rate

000

, For PPxNE

Eb ≤≥

0NEb0x

EP

0P

0.5

-1.6dB

0

Shannon Limit of error-free communication

BER BER

Eb/N0 (dB)

OrthogonalModulation

M-PSK

M=2k

M-aryM symbolson signal space

e.g., FSK

BW ↑

BW ↓

95

BR

NE

BNTE

NS bb ×=

×=

00

Hertzin bandwidth

ratebit 1bitper duration time

Hertzper power noise bitper energy signal

power noise powersignal

0

=

==

=====

BT

R

TNENS

b

Bit Energy to Noise Ratio and Signal to Noise Ratio

RB

NS

BNTS

NEb ×=

×=

/0

Energy

RFDigital baseband

Sensitivity

BR

NE

NS b

0=

)(1010)(1010)/( 0 BLogRLogNESNR dBbdB −+=

)(1010)/(/174)(1010/174

)(1010)()(

,0

,

,/

,

RLogNENFHzdBmSNRBLogNFHzdBm

SNRBLogNFkTSNRNFkTBySensitivit

reqddBbdB

reqddBdB

reqddBdBHzdBm

reqddBdBdBmdBm

+++−=+++−=

+++=++=

ySensitivit)()( requiredrequired0

→→NS

NEb

At T = 290K, kT = -174dBm/Hz

96

RF System Specifications

nonlinear system

Pin Pout

Pin (dBm)

Pou

t (dB

m) fA, fB

2fA-fB , 2fB-fA


slope

=1

slop

e=3

1dBP1dB

NF


Output noise floorSNR required

SensitivityMDS = Minimum Discernible Signal

Dynamic Range (DR)

Pin (dBm)

P out

(dB

m)

IP3P1dB

IM3 = MDSNF

MDSOutput noise floor

SNR required

Sensitivity

3rd-order IM SFDR

Input noise floor

Usable DR

Max. IM3 allowed

There are many definitions for DR:

97

OIP3: 3rd-order Output Intercept Point

IIP3: 3rd-order Input Intercept Point

OIP3(dBm) = IIP3(dBm) + Gain(dB)

IMD: Inter-Modulation Distortion

IM3: 3rd-order Inter-Modulation product(dBm)

OIP3(dBm) = Pout + (Pout - IM3)/2

Glossary Summary

SFDR: Spurious Free Dynamic Range

NF: Noise Figure

SNR: Signal Noise Ratio

Noise

98

Major Noises• Thermal Noise: most basic type of noise. Caused by

thermal vibration of charges. Also called Johnson or Nyquist noise. Present in every resistor or resistance in circuits.

• Shot Noise: happens when DC current flows through a potential barrier, e.g., a PN diode junction. a.k.a. Schottky noise.

• Flicker Noise: a.k.a. 1/f noise. Caused by charge trapped due to surface defects and impurities. BJT is better than FET. Important to VCO and direct conversion receiver.

Noise Figure / Noise Factor

noisy amplifier

Nin Nout

Sin Sout

GA NA

AinA

AinAAin

inin

outoutinin

GNN

GSNGN

NS

NSNSNF

×+=

×+×

×== 1//

Ainout

GNNNF

×=

NF>1, NF(dB)>0dB

SourceInput todue NoiseOutput PowerNoiseOutput Total

≡NF

T∝If not specifically mentioned, T=290K

99

Thermal Noise and Temperature

Random voltage generated by a noisy resistor at T>0K.v(t) has a zero average value, but a nonzero RMS value

14)( /

2−

== kThfne

hfBRtvv

h=6.546x10-34 J-sec (Planck’s constant)

k=1.38x10-23 J/K (Boltzmann’s constant)

f : center frequency (Hz)B : Bandwidth (Hz)R: Resistance value (Ω)

Black body radiation law

14)( /

2−

== kThfne

hfBRtvv

If hf << kT, e.g., f=300GHz and T=290K,hf=1.96x10-22 J << kT=4.0x10-21 J

kThfe kThf ≅−1/ kTBRvn 4=

• Not valid at very high frequency or very low temperature• noise power independent of frequency (white noise source)• noise power proportional to the bandwidth• These white noise sources are independent Gaussian distributedrandom variables, they are additive. AWGN =Additive White Gaussian Noise

100

Available noise power = maximum noise power delivered to load resistor

kTBR

vRR

vP nnn ===

4)

2(

22

nP

• Smaller bandwidth collects less noise power• Cooler devices and components generate less noise power• Impedance has to be matched

Equivalent Noise TemperatureAn alternative way of describing noise contribution of anoisy network (a source or an amplifier)

Thermal noise floor at 290K = kTB, Te=290K

Ps: noise power from source

kBPT s

e =

Assume a matched R at input with temperature Te

BkTPP ens ==

101

AAio NNGPP =+×=

BGkTN eA =

Contribution of noise from amplifier is modeled as an equivalent noise source at input

0=iP

BkTP ei = BGkTNGPP eAio =+×=0=AN

00111

TT

BGkTBGkT

GNNNF eein

A +=+=×

+=

K2900 =T

BTTGkBGkTBGkTN eeout )( 00 +=+=

Total output noise power:

eT The temperature increase at source resistance to producesame amount of noise power at output when modeling theamplifier as noiseless.

102

Some textbooks use F for Noise Factor (linear) and NF for Noise Figure (in dB), but some others do it the other way. Some treat Noise Factor and Noise Figure the same, and can be in either linear scale or dB. As long as you know whetherit’s in linear scale or dB, doesn’t matter what symbol and term you use.

Example from Lee, TheDesign of CMOS RFIC

Nin Nout

Sin Sout

NF1 NF2 NFn

G1 G2 Gn

121213

12

1111

−

−++

−+

−+=

nn

cas GGGNF

GGNF

GNFNFNF

LL

Cascaded Gain and NF

ncas GGGGG ++++= L321 in dB

not in dB

ncas GGGGG ××××= L321 not in dB

12121

3

1

21

−++++=

n

eneeGGG

TGG

TGT

ecas TTL

L not in dB

103

NF of a passive lossy network

L=1/G: Loss

addedout NGkTBkTBN +==

kTBL

NBGkT addede )11( −==

TLTe )1( −=

00)1(11TTL

TTNF e −+=+=

If T= T0 LNF =

Reference to T0

Terminate with a resistor R at same temperature T

sky noise temperatureAntenna collects noise from galactic, solar, and terrestrial sources.

104

Antenna temperature from sky noise

Typical numbers: ground ~300K, sky at zenith ~5K,sky at horizon ~100-150K

Brightness Temperature of objects

Why 5K? 3K background radiation + noise due to atmospheric absorption

Why use T0=290K?

• K = 1.38x10-23 J/K• KT0

= 1.38x10-23 J/K x 290K = 4x10-21 J= 4x10-21 W/Hz = -174dBm/Hz

105

Linearity

Pin

fA, fB

2fA-fB , 2fB-fA

OIP3

slope

=1

slop

e=3

receiver noise floor

PIM3

Pout

22 OIP3 3 ∆

++=−

+= GPPPP inIMout

out

in dB!

Input

Output

2 IIP3 ∆

+= inP

106

Cascaded IP3

Not in dB!Output:

Input:

n

n

total IIPGGG

IIPGG

IIPG

IIPIIP 33331

31 121

3

21

2

1

1

−++++= LL

IP31 IP32 IP3n

G1 G2 Gn

12211 31

31

31

31

31

OIPGGOIPGGOIPGOIPOIP nnnnnnntotal LL++++=

−−−

IP3total

Gtotal

1−∆

+=n

PIIPn in nth-order intercept point

IPn

2/)1(21

2/)1(21

2/)1(1

2/)1(2/)1(

)(

)(

)(

nM

nMMM

nMM

nM

ntotal

GGOIPn

OIPnGG

OIPnG

OIPnOIPn

−

−−−

−−

−−

++

+

+

=

LL

Cascaded OIPn

1−∆

+=n

POIPn out in dB!

107

IP31 IP32 IP3n

Summary of Noise and IP3 in Cascaded System

G1 G2 Gn

NF1 NF2 NFn

• Noise dominated by first stage.(noise floor amplified by first stage gain and NFn all refer to 290K)

• IP3 dominated by last stage.(large signal easily gets into saturation)

Nonlinearity

nonlinear system

Pin Pout

Pin (dBm)

Pou

t (dB

m)

fA, fB

2fA-fB , 2fB-fA


slope

=1

1dBP1dB

• Where does gain compression come from?• IP3 is usually ~10dB higher than P1dB, why?

108

nonlinear ampfS

nonlinear ampfS fB

G=?

G=?

Gain Compression: Two Scenarios

Large signal inputNo blocker or weak blocker

Small signal inputBut, large in-band blocker

Scenario 1

Scenario 2

Signal at ω1, Blocker at ω2.

Consider up to 3rd order term:

Gain Compression: Mathematical Model

Nonlinear behavior of a component

109

Scenario 1, large signal input at ω1, no blocker or very weak blocker

02 =V

L

L

+=

++=

tVa

tVVaaVo

111

112

131

cos'

cos)43(

ω

ω

1)431log(20 2

113 −=+ V

aa

To have gain compression, 013 <

aa

1dB compression point

Scenario 2, small signal input at ω1, large blocker at ω2.

12 VV >>

L

L

+=

++=

tVa

tVVaaVo

111

112231

cos'

cos)23(

ω

ω

110

Blocker Power (dBm)

Gain (dB)

P1dB

1dB

Signal at ω1

1dB compression point due to blocker is 3dB lower than due to signal itself.

)(3)269.0381.0log(20)log(20

21 dB

VV

==

Comparison of Two Scenarios

nonlinear ampfS nonlinear ampfS

nonlinear ampfS fB nonlinear ampfS fB

1dB compression point:scenario:

111

1)431log(20 2

113 −=+ V

aa

1dB Compression Point in dBm

At IP3, 331 4

3V

aVa =

312

34

aa

V =

IP3: Mathematical Model

112

IP31 IP32 IP3n

Summary of Noise and IP3 in Cascaded System

G1 G2 Gn

NF1 NF2 NFn

• Noise dominated by first stage.(noise floor amplified by first stage gain and NFn all refer to 290K)

• IP3 dominated by last stage.(large signal easily gets into saturation)

Transceiver Architectures

113

LO1

BPF SAWMixerLNA IF Amp

DuplexerTo Antenna

From Transmitter

90°

LO2

I Q

Receiver – Heterodyne

ADC ADC

DEMOD

• Single conversion or dual conversion • Channel selection by SAW filter• IF frequency planning• Need at least two LO sources• Integration level is low due to filters

LPF LPF

LO1

BPF IF1 SAW1st

MixerLNA IF Amp

DuplexerTo Antenna

From Transmitter

LO2

Receiver - 2nd IF Sampling

ADC

2ndMixer

• Faster ADC • Digital IQ demodulation• Need IF2 filter (LO2≠IF1). Why not make IF2=0?• Still need two LO sources• Integration level not much higher

IF2Filter

114

LO


DuplexerTo Antenna

From Transmitter

Receiver - Direct IF Sampling

ADC

• Very fast ADC• Single LO source• Digital IQ demodulation• Channel selection by SAW

LO

DEMOD

LNA

DuplexerTo Antenna

From Transmitter

Receiver - Direct-Conversion Zero-IF

90°

LPF

LPF

ADC

ADC

• Very high level integration• No image frequency (single carrier)• No SAW. Channel selection by baseband LPF• Adjustable channel BW by baseband LPF• Problem: DC offset and IM2 (IP2)• Problem: 1/f noise (CMOS)• LO pulling by in-band interferer (injection locking)• AC coupling can be used in broadband system

115

LO

DEMOD

LNA

DuplexerTo Antenna

From Transmitter

Receiver - Direct-Conversion Low-IF

90°

• Channel selection by BPF• Image rejection by image-reject architecture • DC offset handled by AC coupling• 1/f noise is not so critical as Zero-IF

ADC

ADC

Image Rejection and BPF near DC

LO1

BPF SAWMixerPA IF Amp

DuplexerTo Antenna

To Receiver

90°

LO2

I Q

Transmitter - Indirect Up-Conversion

DAC DAC

MOD

VGA

• SAW filter cleans up modulator noise• Need two LO sources

116

Transmitter - Direct Up-ConversionBPFPA

DuplexerTo Antenna

To Receiver

90°

LO

I Q

DAC DAC

MOD

VGA

• No SAW filter• High level integration - only one LO needed• Modulator noise floor must be low enough• LO pulling

Details on Receiver Architectures

117

Typical duplexer frequency response

DuplexerAntenna

From Transmitter

To Receiver

Frequency

S21

e.g., PCS 1850-1910 MHz 1930-1990 MHz

PA leakage affects LNA

• Affects the sensitivity – desensitization.• Problem in FDD with high power transmitter.

? W? dBw? dBm

Gain Compression G1NFtotal

G1

118

Rejecting out-of-band interferers (band selection)

Band: the entire spectrum in which users of a standard can use. Examples: GSM downlink 935-960 MHz, FM 88-108 MHz

Channel: a portion in the band that one user occupies. Examples: GSM/FM channel bandwidth=200kHz

• A 900MHz phone receives 30kHz channel while rejectinginterfering channels 60kHz away.• If the BPF needs to provide 60dB rejection at 45kHz away,the Q would be very high! (~107 for 2nd order LC filter)• Hard to do channel selection at RF.

Rejecting in-band interferers (channel selection)

119

Interference in wireless communications

• Where do those interferers come from?

Transmitter

Receiver

T-MobileGSM1900

SprintPCS CDMA

CDMA phone

GSM phone

Co-existence of wireless Systems

Which phone suffers the worst interference problem?

1930-1990 MHz

1930-1990 MHz

RX

RX

120

How does IMD3 affect the signal?

3rd-order intermodulation products

Image problem in heterodyne system

mirror

ωLO - ω1 = ωIF = ωim - ωLO

])cos()[cos(21coscos 111 tttt LOLOLO ωωωωωω ++−=×

])cos()[cos(21coscos tttt LOimLOimLOim ωωωωωω ++−=×

121

Image rejection by filter

IRF

• IRF also rejects large output noise of LNA.• An alternative is to use Image Reject Receiver

– to be discussed later.

Channel selection by another filter

Important: IP3 is not an issue after channel select filter.

122

Channel Select Filter – SAW

Channel Select Filter – Crystal

123

Channel Select Filter – Ceramic

Problem of Half-IF Interferer

In-band interferer/blocker

To solve the problem:1. Minimize the 2nd order distortion.2. IF frequency > 2 x (RX Bandwidth)

RX Bandwidth for different systems:EGSM: 35MHz, DCS1800: 75MHz, PCS1900: 60MHzAMPS/TDMA/CDMA(800MHz band) and GSM: 25MHz

124

Tradeoff between image rejection and channel selection

High IF

Low IF

Image Reject – GoodChannel Select – Bad

Image Reject – BadChannel Select – Good

Dual-IF ArchitectureIP3

Relaxed Q

125

Quadrature Downconversion

The last stage before ADC in most digital communication systems

]sin)(cos)([21 θθ tbta +

]cos)(sin)([21 θθ tbta −−

Direct-conversion Zero-IF (Homodyne)

AM, ASK OK, butFM, FSK or QPSK not good

fRF = fLO

No image!

No need to have 50 ohm

No IRF

monolithic integration

126

Direct-conversion Zero-IF ReceiverChannel Selection

LPF: linear & low noiseAmp: can be nonlinear

LPF: noise not criticalAmp: linear & low noise

Filtering in digital domainADC: high linearity

IP3

DC Offset

Self-mixing due to LO

Self-mixing due to Interferer

f t

• Due to self-mixing

127

DC Offset Cancellation

• High pass filtering.– Affect BER performance.– Need large capacitors.

• DC-free coding – encode the signal to reduce DC energy.

• Calibration when not transmitting signal.• DC offset may not be constant. Could vary in time.

– Makes the DC offset cancellation more difficult.

f

Quadrature Generation

Quadrature in RF Quadrature in LO

Difficult for broadband signalsVery narrowband

(Single-tone)

128

Quadrature Generation

RC-CR network

I/Q Mismatch

129

I/Q Mismatch

Gain error Phase error

I/Q MismatchIn time domain:

Gain error Phase error

I/Q mismatch in heterodyne is less a problem:1. I/Q balance at low frequency is easier.

• Less sensitive to mismatches in parasitics• Large devices can be used to improve matching

2. Homodyne has I/Q separation before filtering (linearity). Heterodyne has gain and filtering before I/Q separation.

3. Heterodyne can have digital I/Q separation. Homodynecan only do analog I/Q separation.

130

Even-order distortion

Example: IP2 (second-order)

And, nonlinearity of mixer also contribute!

Reference Design Example –RF Specifications Case Study

131

GSM ReceiverTask: Define RF specifications for a GSM handset receiver front end

and design an RFIC architecture that meets the specifications.

Documents: 1. GSM 05.05 version 5.5.1 (ETS 300 910) January 1998.Radio transmission and reception.

2. GSM 11.10-1 version 5.6.1 (EN 300 607-1) December 1998Mobile station conformance specification.

3. GSM 01.04 version 5.0.0 March 1996Abbreviations and acronyms.

4. GSM 05.10 version 5.1.1 (ETS 300 912) May 1997Radio subsystem synchronization.

Tools: 1. SysCalc.2. Lecture notes.3. Hand calculation or calculator.

Why GSM?

• The most popular cellular phone standard worldwide.

• Its standard documents are the most well organized and the requirements are the most well defined.

• Its famous blocker requirement gives the most stringent phase noise specifications for VCO.

132

GSM 05.05 version 5.5.1

Scope

134

Mobile Station Power Class

135

Mobile Station Power Control

Base Station Power Class

43 dBm46 dBm49 dBm52 dBm55 dBm58 dBm

136

Output RF Spectrum Mask

Comparison of QPSK, OQPSK, and MSK spectra

Normalized frequency offset from carrier, (f-fc)/R (Hz/bit/s)

Nor

mal

ized

pow

er s

pect

ral d

ensi

ty G

(f)

(dB)

MSK is spectrally more efficient than QPSK/OQPSK.But, has wider main lobe.

137

2)22sin(2)(

ftfTPTfG

ππ

=

222

16 )161

2cos()( 2Tf

fTfG PT−

=π

π

For QPSK and OQPSK:

For MSK:

Equations for Power Spectral Density

P: Average power in modulated waveformT: Bit period = 1/R

First Null

5.0== RffT

43

== RffT

20012.20343833.270 ≈=×

Baseband!

138

In RX band

139

Mixer Spur/Intermod Table Base Station RFIC

140

Figure

9.752dBdB)354.1398.8(200

833.270log10dB398.80

=+=+=⋅=BR

NE

NS b

dB398.80

=NEb

Note: B=Bandwidth, either in baseband or RF

141


S/N ratio

142

dB588.90

=NEb 11dBdB942.01dB)354.1588.9( ≈=+=

NS

TU50: Typical Urban 50 km/h RA250: Rural Area 250 km/h

HT100: Hilly Terrain 100 km/hFH: Frequency Hopping

Control Channel

TCH: Traffic Channel

143

SID: Silence Descriptor.

144

A Receiver Front End for GSM Mobile Station

VCO


AD6459

DuplexerTo Antenna

Synthesizer

From Transmitter

http://www.analog.com/product/selection_guides.html

145

http://www.murata.com/develop/index.htm

Find a Duplexer

146

Dielectric DuplexerFor GSM 900

http://www.murata.com/develop/index.htm

Find a Dielectric Filter for Image Rejection

147

Find a SAW Filter

http://www.sawtek.com/products/catalog/gsm.html

> 50 MHz(2x Receiver BW)

Receiver Specifications

Pin Pout

Pin (dBm)

Pou

t (dB

m)

IP3

slope

=1

slop

e=3

P1dB

NF

Input noise floor = kTB = -174dBm/Hz x 10 log(200000)= -121dBm

Output noise floorSNRmin= 9 dB

Sensitivity = MDS + 9

MDS = KTB + NF

Rx

Gain=Pout-Pin

148

SNR Required

• In digital radios like GSM, sensitivity level is actually related to BER, FER or RBER under different channels and propagation conditions, not a simple SNR.

• We use the most stringent BER requirement of 10-5 in Data TrafficChannel to estimate SNR ~ 11dB.

• Frequency Hopping reduces the SNR requirement from 11dB to9dB, (An introduction to GSM, Artech House, 1995, p. 142.)

• 9dB SNR also ensures meeting Co-Channel Interference requirement –C/I=9dB. Signal is at 20dB above sensitivity level.

• Advanced proprietary coding may further reduce SNR requirement.• For now, let’s use 9dB for SNR requirement.

Sensitivity = -121dBm + NF + 9 < -102dBm

Reference Sensitivity → NF

NF < 121dBm - 9 -102dBm = 10 dB

149

-49dBm

-99dBm-99dBm-9dB= -108dBm

(Refer to input)

Intermodulation Characteristics → IP3Assume noise power is much lower than IMD3 power.

IP3

5.192

)108(49493 −=−−−

+−=IIP

Intermodulation Characteristics → IP3

-49dBm

-108dBm

224

2)99(49493 general,In SNRSNRIIP +−=

−−−−+−=

150

GSM MS Receiver

GSM MS Receiver

NF (dB)Gain (dB)IIP3 (dBm)

Po (dBm)NF+ (dB)IP3+ (dBm)

Duplexer

3.20-3.20

100.00

-105.201.090.00

LNA

2.5015.00

-10.00

-90.201.740.56

Image Rejection

Filter

2.60-2.60

100.00

-92.80

0.00

Mixer

10.008.000.00

-84.801.081.03

IF Amp

5.0015.003.00

-69.800.044.78

71 MHz SAW

6.50-6.50

100.00

-76.30

0.00

AD6459

10.0079.00

100.00

2.700.020.00

Input Pwr (dBm) -102.00 System Temp (K) 290.00

Total

6.92104.70-15.96

Modulation: MSK, CoherentSystem BW (MHz) 0.20 MDS (dBm) -114.05 Input IP3 (dBm) -15.96BER (Req'd) 33.63e-6 Eb/No (dB, Req'd) 9.00 Output IP3 (dBm) 88.74Eb/No (dB, Actual) 12.05 Es/Eb (dB) N/A OIM3 (dBm) -169.39Srce Temp (K) 290.00 Sens. Losses (dB) 0.00 ORR3 (dB) 172.09Te Eff. (K) 1136.53 Sensitivity (dBm) -105.05 IRR3 (dB) 57.36

G/T (dB/K) -21.54 SFDR3 (dB) 65.39

SysCalc Calculation

GSM MS Receiver

GSM MS Receiver



Duplexer

3.20-3.20

100.00

-43.201.090.00

LNA

2.5015.00

-10.00

-28.201.740.56

Image Rejection

Filter

2.60-2.60

100.00

-30.80

0.00

Mixer

10.008.000.00

-22.801.081.03

IF Amp

5.0015.003.00

-7.800.044.78

71 MHz SAW

6.50-6.50

100.00

-14.30

0.00

AD6459

10.001.00

100.00

-13.300.020.00


Total

6.9226.70

-15.96


G/T (dB/K) -21.54 SFDR3 (dB) 65.39

SysCalc Calculation

151

GSM MS Receiver

GSM MS Receiver



Duplexer

3.20-3.20

100.00

-52.201.090.00

LNA

2.5015.00

-10.00

-37.201.740.56

Image Rejection

Filter

2.60-2.60

100.00

-39.80

0.00

Mixer

10.008.000.00

-31.801.081.03

IF Amp

5.0015.003.00

-16.800.044.78

71 MHz SAW

6.50-6.50

100.00

-23.30

0.00

AD6459

10.0025.00

100.00

1.700.020.00


Total

6.9250.70

-15.96


G/T (dB/K) -21.54 SFDR3 (dB) 65.39

IIM3 (input IMD3)=-64.39-50.70=-115.09<-108

SysCalc Calculation

Blocking Characteristics → VCO Phase Noise

RF

Blocker

LO

RF = -99dBm

Blocker = -43dBm

600KHz 600KHz

IF = -99dBm + Gain

LO - Blocker = -43 dBm + Gain

-43 dBm + Gain + x dBc/Hz + 10 log(200kHz) < -108dBm + Gain

x dBc/Hzx dBc/Hz< -108 + 43 - 53= -118 dBc/Hz

152

Offset Phase Noise(dBc/Hz)

Blocker level(dBm)

600 kHz -118 -43800 kHz -118 -431.6 MHz -128 -333 MHz -138 -23

Blocking Characteristics → VCO Phase Noise

Reference Interference Level → VCO Phase Noise In GSM 05.05 6.3, adjacent channel interference also affect VCO phase noise.

RF

Interference

LO

RF = -82dBm

Interference = -33dBm

600KHz 600KHz

IF = -82dBm + Gain

-33 dBm + Gain

-33 dBm + Gain + x dBc/Hz + 10 log(200kHz) < -82dBm + Gain - 9dB

x dBc/Hzx dBc/Hz< -91 + 33 - 53= -111 dBc/Hz

153

Reference Interference Level → VCO Phase Noise


InterferenceC/I (dB)

200 kHz -71 -9400 kHz -103 -41600 kHz -111 -49

Combined VCO Phase Noise Requirement


200 kHz -71400 kHz -103600 kHz -118800 kHz -1181.6 MHz -1283 MHz -138

154

Offset@kHz

1. DCS 1800MS

2. GSM 900small MS(<=2W)

3. DCS 1800Micro BTS

4. DCS 1800Normal BTS

5. GSM 900Micro BTS

6. GSM 900Normal BTS

600 -116 -118 -121 -128 -130 -137800 -116 -118 -131 -138 -140 -147

1600 -126 -128 -131 -138 -140 -1473000 -133 -138 -131 -138 -140 -150

GSM Receivers Phase Noise Requirements

-160

-150

-140

-130

-120

-110

-100

100 1000 10000

Offset Frequency (kHz)

Phas

e N

oise

(dB

c/H

z)

123456

• Assume C/I=9dB

A Comparison

Which offset frequency is most critical?

DCS 1800 MS

GSM 900 small MS

DCS 1800 Micro BTS

-20dB/decadeor

-30dB/decade

MS: 600kHz and 3MHz, BTS: 800kHz

155

RFIC Design Issues

Impedance Matching

S11

S22

NFmin

MAG

A typical transistor (FET) on Smith Chart

Transistor’s in/outusually capacitive

Match to 50 Ω

156

Impedance (Ω)

Why 50 Ω ?

A compromise of 77Ω(minimumattenuation for air dielectric) and30Ω(maximum power capability)

CATV uses 75Ω.

Note: 50Ω was not optimized for Integrated Circuit(IC) environment.

Reference: T. S. Laverghetta, Microwave Measurements and Techniques

DUT

S21

S12

S11 S22

S parameters

(input return loss) (output return loss)

(gain or insertion loss)

(isolation)

a1

b1

a2

b2

S11 = a1

b1

a2 = 0

S21 = a1

b2

a2 = 0

S12 = a2

b1

a1 = 0

S22 = a2

b2

a1 = 0

S-matrix =

157

VSWR v.s. Return Loss v.s. Mismatch Loss

VSWR Return Loss Mismatch Loss

2.5:1 7.4 dB 19%(0.89dB)

2:1 9.6 dB 11%(0.52dB)

1.5:1 14 dB 4%(0.18dB)

1.22:1 20 dB 1%(0.045dB)

1:1 ? ?

VSWR and Return Loss

• Reflection Coefficient

• Voltage Standing Wave Ratio

• Return Loss

VSWR 1 + |1 - |

=ΓΓ

||

111

1 S- = || log 20- = ab log 10- = RL Γ

ab =

1

1Γ

158

Power Gain

Transducer Power Gain

Available Power Gain

Operating Power Gain

DUTSource Load

⎥⎦

⎤⎢⎣

⎡

2221

1211

SSSS

INPAVSP LPAVNP

LΓOUTΓINΓSΓ

222

22

212

2

1

1

1

1source from availablepower load todeliveredpower

L

L

SIN

S

AVS

LT

SS

PPG

Γ−

Γ−

ΓΓ−

Γ−===

22

21211

2

11

1

1source from availablepower DUT from availablepower

OUTS

S

AVS

AVNA S

SPPG

Γ−Γ−

Γ−===

222

22

212 1

1

11

DUT input topower load todeliveredpower

L

L

ININ

LP

SS

PPG

Γ−

Γ−

Γ−===

Power Gain

221S

PPGAVS

LT ==

22

211

1

OUTAVS

AVNA S

PPG

Γ−==

22121

1 SPPG

ININ

LP

Γ−==

For 50 Ω source and load:

Note:* when SININAVS PP Γ=Γ=* when OUTLLAVN PP Γ=Γ=

L

LIN S

SSSΓ−Γ

+=Γ22

211211 1

S

SOUT S

SSSΓ−Γ

+=Γ11

211222 1

Most commonly used

159

Power GainNow, if the DUT is matched to non-50 Ω , but equipment source and load are still 50 Ω , how do we get real DUT gain in non- 50 Ω?

Hint: is measured.

2

)50(22

22

50212

2

1

1

1

1

L

L

SIN

ST

SSG

Γ−

Γ−

ΓΓ−

Γ−=

Ω

Ω

Ω⎥⎦

⎤⎢⎣

⎡

502221

1211

SSSS

5050

+−

=ΓS

SS Z

Z5050

+−

=ΓL

LL Z

Z

0 and 0 )(Z22)(Z11)(5012 LS=== ΩΩΩ SSSIf

SS

SIN Z

ZS Γ=+−

==Γ Ω 5050

)50(11

(Input/Output matched to )LS ZZ /

LL

LOUT Z

ZS Γ=+−

==Γ Ω 5050

)50(22

504)50(

504)50(

11

11

1

1

1

1 22

5021

2

22

5021222

22

502122

2

⋅⋅+

⋅⋅+

=Γ−Γ−

=Γ−

Γ−

Γ−

Γ−=

ΩΩΩL

L

S

S

LSL

L

S

ST Z

ZSZ

ZSSG

Power Gain

dB 36.0)()042.1(504)50(

504)50(

)50(212

50212

22

5021

22

7521 +⇒=⋅⋅

+⋅⋅

+== ΩΩΩΩ

SdBSZ

ZSZ

ZSGL

L

S

ST

Example 1 : You have an amplifier designed for 75Ω system but canonly measure S21 in 50Ω system. What is the S21 in 75Ωsystem? Also assume that you did a perfect job to match input and output to 75Ω.

⎟⎟⎠

⎞⎜⎜⎝

⎛===

⋅⋅+

=⋅⋅

+=

⋅⋅+ dB 18.0042.1

15000)125(

50754)5075(

504)50(

504)50( 2222

L

L

S

S

ZZ

ZZ

Example 2 : You have an amplifier designed for 500Ω in/out matching. How do you determine its gain from 50Ω measurement? Again assume that you did a perfect job in 500Ω matching.

dB 81.4025.3100000

)550(505004)50500(

504)50(

504)50( 2222

===⋅⋅

+=

⋅⋅+

=⋅⋅

+

L

L

S

S

ZZ

ZZ

dB 62.9)()( )50(21)500(21 += ΩΩ SdBSdB

160

Interference due to Cross-Talk

• Capacitive coupling could be reduced by ground plane.

• Inductive couplingcould be reduced by proper design

• Common ground couplingdue to finite ground impedance (conductive substrate or ground inductance)

• Power supply line couplingdue to finite impedance looked into power supply could be reduced by de-coupling capacitor

• Radiationcould be reduced by proper shielding

Major causes of cross-talk:

• Single-ended circuit without good ground is liable to interference due toall links of corss-talks.

• Differential circuit has common mode rejection. It reduces common ground coupling and power supply line coupling,but still liable to capacitive coupling, inductive coupling, and radiationcoupling.

• Single-ended circuit with good ground and good de-coupled power linesmay be better than differential circuit since ground plane reduces capacitivecoupling.

• Inductive coupling seems to be the most difficult one.Suggestion: use high impedance in your circuit to reduce current flow on interconnections.Watch the voltage swing on active devices.

Single-ended v.s. Differential