fundamentals of rf systems

Fundamentals of RF Systems

조용희조용희

Fundamentals of RF Fundamentals of RF SystemsSystems

전자파연구실전자파연구실2

1. Microwave systems

Transmission

Information- Channel bandwidth- Base band- Inefficient wave radiation

Modulation – center frequency

Time domain Frequency domain

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Why’s modulation need?

Transmission efficiency- Multiplexing- Antenna length: wavelength- Wave radiation: comparison with DC

Battery: DCAntenna: AC




Microwave transmitter (Tx)

Up-conversion: frequency

)cos()cos(2

1)cos()cos( yxyxyx

BBf BBLO ff BBLO ff


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Microwave receiver (Rx)

Down-conversion: frequency

)cos()cos(2

1)cos()cos( yxyxyx

BBfBBIF ff BBLO ff

IFLO fff IFff


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Microwave transceiver

Duplexer: bandpass filter or switch- Loss, tx suppression, channel selection

IF: superheterodyneNo IF: direct conversion


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FDMA (FDM Access)


Resource: frequency Guard band Simple transceiver Interference



DS(Direct Sequence)-CDMA


QPSK: Quadrature Phase Shift Keying



Fundamentals

Antenna gain: anisotropic radiation (G > 1)isotropic radiation (G = 1)

Directivity and efficiency: Angular beamwidth: 3dB

Radiation pattern [dBi]: dB isotropic

2. Antennas

DG



2. Antennas

Dipole antenna

Simple but long structure Low efficiency

Microstrip type



Handy phone antenna

Helical antenna

2. Antennas

Complicated structure Medium efficiency



Antenna simulation

Ansoft: Ensemble

CST: MWS

Ansoft: HFSS

2. Antennas



Wave propagation

}Re{

}Re{

)cos(),()(

tjzjjo

ztjo

o

eeeV

eV

ztVtzV

3. Tx line theory



Distributed element

Lumped element: R, L, C

Distributed element: tx line

3. Tx line theory



Wave solution

Traveling wave solution- Voltage:

- Current:

zzs eVeVzV 00)(

zzs eIeIzI 00)(

)())(()(

2

2

zVCjGLjRdz

zVds

s

))(( CjGLjRj

3. Tx line theory



Characteristic impedance

Important parameter in tx line:

-

-

CjG

LjRZ

0

0

0

0

00 I

V

I

VZ

3. Tx line theory

0Z



Reflection coefficient

0

0

011 ||

ZZ

ZZ

V

Ve

L

Loj

Voltage wave continuity conditions Current wave continuity conditions

3. Tx line theory



Wave power

2

0

2

0* 12

Re2

1

Z

VVIP

3. Tx line theory



SWR (Standing Wave Ratio)

SWR: field theory VSWR (Voltage SWR): tx line theory

||1

||1min

max

V

Vs

Experiment

3. Tx line theory



Smith chart

Graphical method

Essential diagram for microwave engineering

P. Smith in 1939

3. Tx line theory



Induction of Smith chart

S-parameter: reflection coefficient

|S11| = 0: all transmission |S11| = 1: all reflection

3. Tx line theory



VNA (Vector Network Analyzer)

Measurement equipment

Reflection coefficients with frequency sweep

3. Tx line theory



Scattering matrix: Two-port network

Matrix definition: matched load

gain:

isolation:

reflection:, where

21

12

2211

2

1

2221

1211

2

1

S

S

SS

V

V

SS

SS

V

V

3. Tx line theory



Antenna impedance

Antenna impedance (not infinity) matching No reflection, power efficiency

Handy phone antenna

3. Tx line theory



Coaxial line

3. Tx line theory

Wide bandwidth (TEM) Characteristic impedance: 50 Ohms Shielding Conductor and dielectric loss Measurement RG (Radio Government) series

Coaxial line



Connector

BNC (Bayonet Neill Concelman) connector SMA (SubMiniature type A) connector Type N connector Type K connector APC (Amphenol Precision Connector)

3. Tx line theory



Microstrip line

3. Tx line theory

Quasi-TEM line Easy fabrication: etching Substrate Characteristic impedance



Substrate

Relative permittivity Thickness of a substrate: mil (inch/1000) Thickness of a metal: oz (almost 1.4 mils) Loss: loss tangent Temperature

3. Tx line theory

Power amplifier module



Etching: PCB (Printed Circuit Board)

FR4, RT/duroid 5880 (6010 …) Film Photoresist (PR) Toluene Ultraviolet Iron chloride

3. Tx line theory



Selection of active device

4. Amplifier

pHEMT amplifier with package

Gain [dB]

Bandwidth [Hz]

Stability: oscillation

Noise figure [dB]: LNA

P1dB [dBm]: PA

Characteristics of active device: bias

Bare chip



Wire bonding for bare chip

Wire bonding vs.soldering

4. Amplifier



Bias design

Assignment of AC and DC path

4. Amplifier



S2P file: S-parameter information

Input impedance: S11

Output impedance: S22

Gain: S21

Isolation: S12

4. Amplifier



Impedance matching

Lumped elements (L or C)

Stub matching

Conjugate matching: maximum power transfer

Noise matching: low noise

*LL ZZ

4. Amplifier



Block diagram of cellular phone

LNA (Low Noise Amplifier), PA (Power Amplifier), Mixer, VCO, switch

Filter, duplexer

4. Amplifier



Digital RF system

Transmitter and receiver

4. Amplifier



LNA (Low Noise Amplifier)

Noise figure: 2 dB Amplifier gain: 15 dB Return loss: 15 dB Reverse isolation: 20 dB Impedance matching: power and noise

4. Amplifier



SNR: signal to noise ratio Noiseless system: NF = 1 Noisy system: NF > 1 Ground

Noise figure (NF)

4. Amplifier

in

out

out

in

out

in

N

N

S

S

SNR

SNRNF



Simulation of LNA

PortOUTNum=2

PortINNum=1

CC2C=1.0 pF

CC1C=1.0 pF

LL3

R=L=1.0 nH

LL2

R=L=1.0 nH

TSMC_CM025RF_PMOS_RFPMOS_RF1

finger=16width=10 umlength=0.24 umType=2.5V twin-well

TSMC_CM025RF_NMOSNMOS2

Width=0.30 umLength=0.24 umType=2.5V_nom

LL1

R=L=1.0 nH

RR3R=50 Ohm

RR2R=50 OhmTSMC_CM025RF_NMOS

NMOS1

Width=0.30 umLength=0.24 umType=2.5V_nom

RR1R=50 Ohm

HP ADS (Advanced Design System)

AC and DC path

4. Amplifier



HPA (High Power Amplifier)

Output power (P1dB), power gain Linearity (OIP3) Efficiency (PAE) Temperature

Power amplifier scheme

4. Amplifier



Characteristics

5. Filter

2 port network: S parameters Pass band and stop band Return loss and insertion loss Ripple and selectivity (skirt) Pole and zero Group delay



Classification

LPF (Low Pass Filter) HPF (High Pass Filter) BPF (Band Pass Filter) BSF (Band Stop Filter): notch filter

Duplexer: 2 BPF Diplexer: LPF and HPF

5. Filter



Power divider

Division of power: scattering matrix Lossless system- - Scattering matrix: unitary matrix

3-port networks 5-port networks

222

22

2

lossy

11

1

10

S

** VVVVTT

5. Filter



T-junction power divider

Simple 3-port network Waveguide or microstrip line Lossless or all-port matched network

port at 021in YYYjBY

5. Filter

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Frequency conversion

Mixer VCO: Voltage Controlled Oscillator PLL: Phase Locked Loop TCXO: Temperature Compensated Crystal

Oscillator

6. IF conversion

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fundamentals of rf systems

Technology