design techniques for multiband / multimode radios · 2015. 8. 19. · sat ham vhf hi tv10 mostly...

Design Techniques for Multiband / Multimode

Radios

June 5, 2008

Steve Ellingson

Bradley Dept. of Electrical and Computer Engineering

Virginia Polytechnic Institute & State University

[email protected]

2Multiband RadioEllingson Jun 5, 2008

About the Instructor

Antennas, Signal Processing, Instrumentation

Ph.D., The Ohio State University, 2000

Experience: Assistant Professor, VT since 2003 Research Scientist, OSU ElectroScience Laboratory Systems Engineer, Raytheon (aka E-Systems, ERA) Consultant, Booz-Allen & Hamilton U.S. Army Officer (Signal Corps)

Email: [email protected]

Web Site: http://www.ece.vt.edu/swe/

Phone: (540) 231-2978

Steve

Ellingson


Outline of this Course

Introduction to Multiband/Multimode Radio (MMR)

Radio Design Basics

Antennas

Digitization

Sensitivity, Gain, and Noise

Linearity

Selectivity & Preselection

Conversion Architectures

RF CMOS

Antenna-Transceiver Interfacing

VT Public Safety MMR

Summary

Acknowledgements

References


What is a Band? Multiband?

This word is very casually used!

Functional definition: A band is a portion of the RF spectrum with distinct propagation characteristics and/or requiring radios with distinct technological characteristics

Log-scale bands: e.g., HF (3-30 MHz), VHF (30-300 MHz), ...

Often subdivided or application-specific: e.g., VHF-low, L-band

Regulatory definition: A portion of the RF spectrum allocated for a specific purpose

Examples: ISM (multiple), Cellular, PCS, Television (muliple), ...

A radio which is multiband works in multiple bands with little or no modification


Bands of the Electromagnetic Spectrum


l Multiband radios need to deal with strong out-of-band signals!

l 406-950 MHz has similar issues, but generally dynamic range requirements decrease with increasing frequency

l TV becomes digital (or dark) in Feb 2009

Example: 3-270 MHz in Columbus, OH [E05b]

HF

VHF

Lo

TV4 TV6 FM Broadcast

Aero/

Sat

Ham

VHF

Hi

TV10

Mostly low-level

until ~400 MHz

l Sensitivity: -87 dB(mW/[30 kHz])

l Red: Max-hold, Blue: Mean, Green: Load


What is a Mode?

Fundamentally, a method of communication.

Sometimes, just a modulation (e.g., NBFM, QPSK)

More often, a standard (e.g., TIA-603, IS-95)

Often, a complete protocol, perhaps including families of standards and perhaps even MAC and higher OSI layers (e.g., APCO Project 25, IEEE 802.11)

The FCC defines bands and constrains the allowed modes (and often, the allowed users) in each band.

History:

Radios traditionally use a single mode, because they are typically used for just one thing

Proliferation of non-standard or (worse!) proprietary modes

Desire or requirement for interoperability has led to increasing interest in multimode radios


Why Multiband/Multimode Radio (MMR) ?

Military

Interoperability a perpetual problem, becoming particularly acute with the advent of rapid joint service ops in the 1980s

Primary instigators for software-defined radio (SDR), but the underlying motivation is to have multiband/multimode capabilities.

Public Safety

Analogous to military application, except interest in interoperable radio is much more recent and cost is much bigger issue

All-in-ones and personal digital assistants (PDAs)

Emerging now because it is becoming practical

Dynamic spectrum & new paradigms for spectrum management

Multiband/multimode radio is enabling technology for these things

However, white space seek/detect is a new application

Down the road: Cognitive radio


Public Safety MMR Concept

Audio

Sw

itch /

IP R

oute

r

Selected VoiceChannels

Selected Data Channel

Combine Many Radios into One*

At least 13 bands relevant to Public Safety x Many channels per band = A lot of radios!

(*Above figure is just a functional description.)

Frequency Bands:

VHF LO (25-50 MHz)

VHF (138-174 MHz)

220 MHz

UHF (406-512 MHz)

700 MHz P.S.

800 MHz P.S.

Cellular & PCS

2.4 GHz ISM

4.9 GHz P.S.

Goal: Seamless Interoperability

l Many agencies would be delighted just

to have a single mode with 2 bands!

l In most cases, 3-4 bands (VHF-Hi, UHF,

and 700/800 MHz) would be Nirvana

l The real issue: Cost.


All-in-Ones

Illustration is from the

web page of

Bitwave Semiconductor

http://www.bitwave.com

FEM = Front End Module

Note that even if the radioelectronics are tightly integrated, antennas remain a problem

Design imparitives:(1) Cost(2) Size(3) Power consumption


Existing MMR (1/2)

Commercial Mobile Telecommunications (Cellular/PCS)

Low-cost 3- and 4-band transceivers widely available, primarily to accommodate regional and international roaming

Low cost possible because

Each band individually has small tuning range and is limited to one mode or a family of very similar modes

Modest performance requirements

Extremely large production volumes

Amateur Radio

High-performance low-cost 3- and 4-band handheld transceivers are widely available [E06].

Possible because each band individually has small tuning range, and operation is limited to AM and FM modes


Existing MMR (2/2)

Military; e.g., JTRS (DOD SDR program)

E.g., 5W HTs with 30-512 MHz continuous tuning and ~5 modes: Harris AN/PRC-152, Thales AN/PRC-148

High cost and somewhat compromized performance primarily due to requirement for continuous tuning over very large (>10:1) bandwidth and SDR-type (SCA) mode flexibility [E06].

Public Safety (Very recently introduced) [J08]:

Thales Liberty: 138-896 MHz in 4 bands; TIA603 & APCO P25

Harris RF-1033M: 30-512 MHz continuous; TIA603 & APCO P25

Common issues:

Capabilities: RF performance, tuning range and mode flexibility; Constraints: Cost, size, power consumption

The %$#@! antenna.


Why This Short Course?

MMR is in growing demand

MMR design issues and techniques are not as widely understood as those for traditional single-band / single-mode radio

MMR applications tend to demand more than what can be achieved by simply squeezing more radios and antennas into a single enclosure

High performance MMR is no problem until you put constraints on cost, size and power consumption!

Recent technical developments seem to be opening the door to practical MMRs with reasonable performance at reduced cost


What this Course Does and Does Not Cover

What this course does not cover:

Basic electronics (suggestions: [R97] and [SS98])

Software defined radio (suggestions: [R02] and [K05])

Dynamic spectrum and cognitive radio (except tangentially)

Detailed discussions of modes or applications

Our focus will be on:

Design issues & tradeoffs

Existing design options and limitations

Emerging trends in MMR

Fair warning:

I assume you have some familiarity with radio design issues, but if something is unfamiliar please ask!

I will tend to emphasize receive over transmit.




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References


Anatomy of a (Traditional) Radio

Antenna

(matching)

Duplexer or

T/R switch

LNA

PA

Mod

Useror

App.

DemodA (A)DRF IF/BB

A (A)DRF IF/BB


What We Need from an Antenna (1/2)

Reasonable pattern.

For mobiles and portables, fair if not omnidirectional

Transmit match: Should be well-matched over the frequency ranges of interest, so as not to reflect or absorb power excessively.

VSWR of 2:1 is good; 3:1 or greater is often tolerated.

Reflected TX power causes performance problems for RX and TX

Reflected TX power is wasted power. Impacts range and battery life.

Receive match: As part of the receiver, deliver the required sensitivity.

Note! This is not the same as being as being well-matched.

It is not uncommon for a receiver to deliver the theoretical best possible sensitivity even with VSWR up to 10:1 or higher!


What We Need from an Antenna (1/2)

Constant impedance over bands of interest. Barring that, impedance characteristics that do not lead to excessive Q when interfaced to the electronics

High efficiency, independently of how well antenna is matched. (Power should be transduced, not stored or dissipated.)

Helpful if terminals are of the same mode (single-ended or differential) as the transceiver interface(s)

Modern mobile/portable antennas are nearly always single-ended, whereas increasingly the electronics interfaces are differential

Herein lies room for improvement...

Size and shape acceptable to user

For mobiles and portables, this typically means either monopole-like, conformal, or embedded.


Multiband Antennas

Some rules of thumb:

A good linear antenna needs to be at least λ/8 at the lowest frequency of operation and is then limited to have fractional impedance bandwidth ~ 10%

A good conformal or embedded antenna can be smaller, but is typically limited to fractional impedance bandwidth ~ 1%

These numbers can be exceeded by a factor of 5 or so by trading off radiation efficiency

Antennas can often be made to be simultaneously effective at two widely-separated frequencies simultaneously. This can be extended to 3, 4, 5 or more bands with increasing difficulty and decreasing fractional bandwidth and efficiency.

If this is not good enough, you can swap antennas. Of course, this irritates users and precludes simultaneous or agile multiband operation.

Another alternative is to integrate multiple antennas. Typically, handheld radios are limited to one protruding linear antenna and 2-3 emedded/conformal antennas. Gets complicated fast!


Effective Limits of Contiguous Antenna Bandwidth

For transmit, impedance matching is paramount, and the pattern typically does not vary much over the resulting (~10%) bandwidth

For receive, it is possible to get into trouble:

For an omnidirectional antenna, maximum dimension roughly 1.5 times first resonance (roughly λ/4 for a monopole) because pattern becomes funky as antenna becomes larger than this

VSWR becomes unacceptable (electrically short, matching entails excessive Q) for frequencies less than about ½ times resonance.

Therefore, the best possible usable antenna has bandwidth ~ 3:1.

The whole range can be used for receive, with only sensitivity degredation.

The whole range can be used for transmit but only about 1-10% BW can be used at any given time due to matching requirement.


Ooi (Motorola) (2005) [O05]

10%

Example: 700/800 MHz Monopole

New (hybrid) antennaλ/4 monopoleNormal-mode helical

5T

5 mm2.3 cm

14.6 cm

50 mm

x

130 mm

4 mmpolyurethane

sheath

VSWR

3:1

2:1

Freq [GHz]

Antenna is 0.43λ at 770 MHz, 0.35λ at 620 MHz

Traditional approaches are <2:1 in 790-880 MHz

New antenna is < 3:1 in 620-920 MHz

Tradeoff is apparent...


Example: Dual Band (Cellular/PCS) PIFA

Antenna is about 0.13λ at 900 MHz

About 6% bandwidth at 900 MHz

No problem to get two bands in a small conformal package, but:

Note radiation efficiency is only 50%-70%

Much recent activity in this area number of simultaneous bands up to 5, but always with tradeoffs...

Faraone et al. (Motorola) (2007) [F+07]


What About UWB Antennas?

UWB antennas will usually not be a reasonable alternative to traditional antennas

A common misconception is that UWB antennas are electrically small, where in fact the opposite is true: They tend to be relatively large because they require low reactance at lowest operational frequency.

Furthermore, antennas for UWB systems are properly designed for optimum transient response - Broadband nature is a result, not a requirement. Consequences are:

Relatively poor/volatile impedance characteristics over specified bandwidth

Awkward shapes




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References


Basics of A/D Conversion

Most modern high-speed ADCs encode full scale at ~1 Vpp @ 50Ω,

and therefore clip around PFS ~ +10 dBm

Quantization noise power for full scale input is usually just about -6Nb

dB relative to full scale power. (Actual value is -6.02Nb-1.76, but

analog imperfections result in an additional few dB noise generation)

Quantization noise is white only if input is white. Inputs containing lots of tones result in quantization tones as well as noise!

In addition, nonlinearity in the ADC transfer function results in intermodulation products. This often becomes the dominant problem as Nb is increased. Impact depends on application (e.g., modulation

of interest)


The A/D Conversion Nb-Fs Dilemma

Presently, A/Ds suitable for noise-limited coherent-sampling up to about 200 MSPS and 14 bits are commonly available. But....

In general, a quantization dynamic range bandwidth product which is achieved at a given sample rate Fs and Nb can also be achieved at a

higher Fs and lower Nb, through decimation.

When digitizing large bandwidths, A/D linearity is extremely important due to the profusion of narrowband signals. This tends to favor increasing Fs (and decimating) rather than increasing Nb.

Unfortunately, A/Ds can be major power hogs in any transceiver.

For any given ADC technology, power consumption is proportional to Fs * 10^(0.6Nb) [KA00].

By itself, this tends to favor increasing Nb rather than Fs


Sensitivity and Gain

The purpose of total gain G is to hoist the received signal over the quantization noise and IMD of the A/D (or, classically, over the detection threshold of an analog demodulator)

However, gain which introduces excessive additional noise defeats the purpose. This is traditionally quantified in terms of the noise figure, F, which in turn determines the minimum detectible signal (MDS):

MDS = δkTABsF (referenced to input), where

δ = minimum SNR considered a detectionk = Boltzmann's constant (1.38 x 10-23 J/K)TA = Antenna temperature: Often taken as 290 K, but

could be more or less than this (stay tuned...)BS = Detection bandwidth ( ~ modulation bandwidth)

In a well-designed receiver, F is nominally dominated by the first amplifier in the signal path since it can only be degraded, not improved. Hence, the low noise amplifier (LNA).


How to Specify F and G

Note we have three sources of noise: The environment (TA), the front

end (F), and ADC quantization.

Generally we prefer:

Environmental noise to dominate over front end noise if possible: This sets F (more on this later)

Environmental + front end noise to dominate over quantization noiseThis sets G (defined from antenna terminals to ADC input):

k T AB F GG P FS100.6N

b

r PFSPA

GG PFS10

0.6Nb

k T AB FBandwidth presented

to the ADC

Desired marginof dominance

Desired ADC headroom

Total power at antenna terminals(including signals)


Example Gain Specification (and MDS)

G=10dBPFS=10dBmN b=12bitsT A=290K

B=1 MHzF=6dB

r=10dBPA=40dBm

40dBG86dB

r PFSPA

GG PFS10

0.6Nb

k T AB F

Desireability of

variable gain and/or

AGC is apparent.

MDS=k T ABS F=121 dB

3 dB detection threshold,

25 kHz bandwidth


MDS Specification?

Procedure in previous slides presumes you are looking for the best possible sensitivity

More often, sensitivity (MDS) is specified, which then sets F.

Example: TIA-603C (NBFM) requires MDS at least -116 dBm

Manufacturers frequently have their own internal rules of thumb on how much better or worse than this they will strive for

Should note that arbitrarily requiring a certain MDS offers no guarantee that the resulting F is optimal in any sense, unless environmental noise is taken into account.

Further, F might be overspecified! This is surprisingly easy to do at VHF and below. The consequences are pretty severe, as we shall see.


External (Environmental) Noise

Standard deviation with respect to location

Compiled from [ITU03] and [E05a] by S.M. Shajedul Hasan

b

A afT

[K ]


External (Environmental) Noise

b

A afT

Mean antenna noise

temperature is well-

modeled as a power

law in frequency:


Optimum Noise Figure

Courtesy of S.M. Shajedul Hasan

This is the noise

figure required of an

amplifier attached to

an antenna if the

output is to be

dominated by

external noise by a

factor of 10 in 90%

of locations of the

indicated type.

Optimum in the

sense that any

lower noise figure

does not

significantly

increase sensitivity

(only cost).

These particular

results assume

lossless, perfectly

matched antenna

with no ground loss.


Amp Connected Directly to Antenna

AT

kT A f 12 G p

pTpG

kT p f G p

Antenna looses up to ~½

of available power into

ground

Amp Gain

Amp Noise Temp.

(typ. 10s to 100s of K)

Refl.

Coef.

Total Noise Power Delivered to Radio:

Ratio of (irreducible) external noise

to (reducible) amp noise: =TA

T p 12


Note that

acceptable noise

performance is

being achieved for

very large VSWR.

Note improving Ta

has no effect on

sensitivity once

is large save your

money!

Improving Tp does

improve bandwidth

over which is

large

=1

Referenced to

antenna terminals

From [E05a]

Large Mismatch is OK at VHF (for RX...)




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References


Linearity

Warning! Not completely general (tangent factor, memory [R98])

Single tone input: Compression plus harmonics

Two-tone input: Above plus ω1+/-ω2 (2nd order IMD)

plus ω1+/-2ω2, 2ω1+/-ω2 (3rd order IMD)

...

vout t =1 v in t 2 v in2 t 3 v in

3 t ...


Compression (P1)


Intermodulation (IP2, IP3)

While the IP3 concept is often useful, it can also be quite misleading!([C+05], [C07])

Useful trivia: Taylor series modelpredicts IP3/P1 = +9.6 dB,independent of coefficients.

Most wireless protocols requireinput IP3 (IIP3) in the range-5 dBm to -20 dBm


Sensitivity-Linearity Tradeoff

Typically, improvements in F and IIP3 (or any linearity parameter) are mutually exclusive.

Incidently, this is true even within the preamplifier (LNA)!


Implications for MMR

HF and VHF-Lo receivers need less G and can tolerate higher F because external noise is so very high. This is good because linearity is a huge problem.

VHF-Hi and UHF receivers need moderate G and F because external noise is moderate. However the linearity requirements can be as bad or worse than at HF.

At higher frequencies, it is relatively rare to be linearity-constrained (exception: PCS bands). This is good because high G and low F is required for outdoor mobile applications.

If our MMR is to span these bands, we have the additional demand of needing to simultaneously satisify these disparate requirements!

The answer is usually selectivity.


Selectivity

Selectivity is bandpass filtering: This is key to mitigating intermodulation effects and simplifying design problems in all kinds of receivers.

RF (front end) selectivity is desirable to exclude potential sources of compression, harmonics, and intermodulation

In superhets, IF band selectivity is desirable to suppress intermodulation at frequencies not of interest (to avoid reentrance later)

Useful primer on filter design in receiver context: [H+07]


Receiver Design Tradeoffs

Sensitivity

Linearity Selectivity

CostSize & Weight

Power


Preselection

Preselection refers to the implementation of selectivity before frequency conversion.

Typically not an issue for single-band radios operating over narrow fractional bandwidth a single RF filter is adequate

For multiband operation or operation over large frequency ranges, we typically need some way to exclude large signals not-of-interest

Fixed TuningMultiplexing

Band 1

Band 2

Band N

.

.

.


Park & Rebeiz (2008) [PR08]

Example: Compact Varactor Tuner

850-1400 MHz

BW ~ 5%

IL < 3 dB

IP3 > 11 dBm


Example: Compact Switched Capacitor TunerPaulsen & Spenser (2007) [PS07]

30-88 MHz

IL ~ 5 dB

256 states

PIN diode switches

Control logic in Multichip Module (MCM)

0.666 in2 footprint


Preselection using Diplexers

A diplexer is a passive bidirectional device that combines 2 spectrally-disjoint ports to a single controlled-impedance common port.

This is superior to power combining/splitting since insertion loss is minimized, return loss is frequency-independent, and you get selectivity essentially for free

Diplexers have many other uses in radio systems: duplexing, connecting a single radio to multiple antennas, and post-mixer absorbitive spurious suppression

Useful references: [MYJ80] (theory), [S99] (a useful design methodology)

Contiguous Band-Selective

Specifiedimpedance

vs. freq.(typically, Z0)

High-pass

Low-pass

Band 1

Band 2


RF Multiplexers

Diplexers are quite easy to design and implement as long as we stick with terminations that are:

Frequency-independent

Single-ended

real-valued impedances

More than two channels are possible; under the above conditions. This is called a multiplexer. Recently compact multiplexers with very large numbers of channels have become practical; see e.g., [G+08].

When the common port impedance is frequency-dependent and possibly reactive, things get interesting.

Becoming important because this is the case when we connect multiplexers directly to compact wideband/multiband antennas!

Recent thinking on this is described in [WM07].




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References



Receive (details in slides to follow):

Direct Sampling / Undersampling

Superheterodyne (Superhet)

Direct Conversion a.k.a Zero-IF

Low-IF

The Menagerie: Hartley, Weaver, Hybrids

Transmit:

Mirror image of receive in many cases. This simplifies frequency planning & reduces number of local oscillators (LOs)

Sometimes, modulation dependent: e.g., NBFM exciters

Our emphasis will be on receive, but we will try to address some of the transmit issues as well.


Direct Sampling

All the gain and selectivity is at RF. (When the backend is something other than a digitizer, this is Tuned RF.)

Digitization requires sample rate more (typically much more) than twice highest bandwidth of interest. ADCs (DACs) with sufficient speed and dynamic range typically do not exist, or are prohibitively power-hungry.

Sometimes feasible at HF and low VHF frequencies, but typically ruled out for mobile/portable use due to power consumption.

Even if high power consumption is acceptable, RF design is a challenge.

IM2 concerns may limit tuning range to be less than 2:1

LNA

A DRF RF

Preselect


Example: 20-80 MHz Direct Sampling Receiver

Prototype receiver for the Long Wavelength Array (LWA) radio telescope (http://lwa.unm.edu)

G ~ 71 dBTp ~ 300K (F ~ 3 dB)

>10 in 29-47 MHzP1dB(in) = -3 dBm

12b @ 200 MSPS400 mA @ 12V + ADC

Craig, Harun & Ellingson (2008) [CHE08]


Undersampling

Undersampling is direct sampling when the passband is in contained within a Nyquist zone other than the first. However, also useful in superhets...

Spectral reversal for odd-numbered Nyquist zones (not a problem unless you forget about it...)

Clock jitter becomes performance-limiting in higher Nyquist zones

Excellent example of undersampling used to simultaneously receive GPS and GLONASS: [A+99]

From [B03]


Superheterodyne (Superhet)

RF is shifted to an intermediate frequency (IF), which is normally (but not always) lower in frequency.

From there, signal is:

Digitized; in which case we have an IF sampling receiver, or

Directly detected (e.g., classical AM/FM receivers), or

Converted again, in which case the IF is used primarily to provide selectivity and gain not possible at RF or baseband

LNAPreselect(Image Reject)

LO

Reject undesiredproducts

ADC

AM/FM Detection

Another conversion

IF


Superhets: Low-Side vs. High-Side Injection

x t =s t cos R t

x t cos L t =s t cos R t cos L t

=s t [1

2cos R L t

1

2cos R L t ]

Low-Side Injection (LSI):

L R : L R I : R L= I

High-Side Injection (HSI):

L R : L R I : R L= I

RF signal:

IF signal: Rejected mixing product

I

Works because cos() is even;however complex modulations become spectrally-reversed


Superhets: Image Rejection

Image Reject Diplexer

IF

L= IAn image is a solution to

The desired solution:

= Rother than

R= L± ILSIHSI

The image solution: R

i = L ILSIHSI R

i= R2 I

LSIHSI

Example: Mixing RF at 138 MHz to IF at 10.7 MHz using LSI:

116.6138.0

127.3

10.7

265.3127.3RF

Image Reject Diplexer

IF

Example: Mixing RF at 138 MHz to IF at 10.7 MHz using HSI:

148.7

RF159.4

138.0

286.7148.7 10.7

Note that

tuning range

increases with

increasing IF


Superhets: Half-IF Problem

From [R97]

Half-IF problem: IM2 from out-of-band interferer after mixing blocks desired IF frequency (Shown for HSI; same thing happens in LSI)

Poses quite a dilemma:

Further limit tuning range to exclude interfering signal, or

Greatly increase mixer IP2 (increase LO level, increase power consumption and LO isolation problems)

Same for both LSI and HSI

Half-IF problem:


Superhets: Tuning Range for LSI (1/2)

Image Reject Filter Response Fractional bandwidth

R

i L ,max R ,min

b2 I / L ,max

2 I

I R ,min / 2/b1Requires

Ex: RF = 138 MHz, LSI, b=0.1 (10%BW): Lowest IF = 6.6 MHz, tuning range ~ 0

(Increase IF to increase TR)

Highest tunable frequency: Image rejection requires:

R ,max

i R ,minb L ,max

R ,max 1b R ,min2b I

after substitution & some algebra:


Superhets: Tuning Range for LSI (2/2)

Maximum tuning ratio:

bTR R,max

R , min

=1b R ,min2b I

R ,min

= 1b2b I

R ,min

Minimum IF to support a specified tuning ratio:

I bTR1b

2b R , min

Example:

f R, min=138, f R ,max=174,b=0.1 bTR=1.261, f I=23.8


Superhets: Tuning Range for HSI (1/2)

Image Reject Filter Response Fractional bandwidth

R

i L ,min R ,max

b=2 I / L ,min

2 I

I R ,max / 2 /b1Requires

Ex: RF = 138 MHz, HSI, b=0.1 (10%BW): Lowest IF = 7.3 MHz

RF = 174 MHz, HSI, b=0.1 (10%BW): Lowest IF = 9.1 MHz

Highest tunable frequency: Image rejection requires:

R ,max

i R ,maxb L ,min

R ,max 1bb

I

after substitution & some algebra:


Superhets: Tuning Range for HSI (2/2)

Maximum tuning ratio:

bTR R,max

R ,min

=

1bb

I

R ,min

=1b

b

I

R ,min

Minimum IF to support a specified tuning ratio:

I bTR R ,min

b

1bExample:

f R,min=138, f R,max=174,b=0.1 bTR=1.261, f I=19.4

For a given tuning range and image filter selectivity, HSI tends to

accommodate lower minimum IF frequencies. However, interference in the

image band should be considered before choosing HSI over LSI.


Divide-and-Conquer Superhet

Decompose the problem into narrower tuning ranges to allow the use of simpler, higher-performance superhets

Main design challenges are frequency planning, and integration

Method of choice for present-day multiband handheld MMR

Complex, put reasonable power since only portion of radio is in used


Up-Down Superhet

Removes tuning range limit (from image rejection) by placing IF above RF.

Tuning range still may be limited to be less than 2:1 in order to avoid IM2 at RF

Cons compared to down-down superhets:

Tuning LO is higher frequency (cost, performance)

Often requires at least one more LO than an functionally equivalent down-down superhet (power consumption)

Fairly common for full coverage (3-30 MHz) HF base (non-mobile) receivers

Preselect(IM2

mitigation)LO


IF2 (< RF)

LO


RF

IF1 (> RF)


Up-Down Superhet for 138-894 MHz Continuous Tuning

ERA-3SM ERA-3SM ERA-3SM ERA-3SM ERA-3SM

DIPLEXER

1250 MHz

DIPLEXER

78 MHz

LARK

1250 MHz

LARK

1250 MHz

78 MHz

ERA-6SM ERA-3SM

SYM-11 SYM-11

FROM LO-1 FROM LO-2

TO

ADC

FROM

PRESELECTOR

Tuning range covers all public safety bands VHF-Hi to 800 MHz + cellular

IF1=1250 MHz (uses stock filters)

IF2=78 MHz accomodates 40 MHz BW in 2nd Nyquist zone at 104 MSPS

Intended for an IF-sampling SDR

Hasan & Ellingson (2006) [HE06]


Divide & Conquer Superhet with Up-Down Path

for 400-2000 MHz Continuous Tuning Ranu & Ellingson (2002) [RE02]


Superhet Summary

The primary advantages of the superhet are the ability to put gain and selectivity at frequencies other than RF.

Splitting gain between stages mitigates many practical problems

Putting selectivity at IF means a single fixed filter can be used

Most limitations of the superhet can be overcome using a divide and conquer approach, using preselection to narrow tuning range.

Given that the tuning range can be covered, it is hard to beat a superhet in terms of overall performance.

But, performance comes at a cost:

Synthesizer for each LO/IF stage power consumption and cost

Complex; high parts count

In divide and conquer systems, these problems are replicated in each parallel RF path.


RF converted to complex baseband using a single, tuning LO.

In some sense, this is the obvious thing to do: Simple (=cheap)!

Output already in I/Q form, as required by complex modulations. Sample rate is minimized, which in turn minimizes power consumption

But traditionally shunned. Issues include:

Direct Conversion


LO

cos

sin

RF

BB-I

BB-Q


Direct Conversion Contraindications

Fundamental limitations [R97,LA02]:

Gain/phase imbalance at baseband

Limited rejection of undesired sideband (typically < 30 dB)

Degraded EVM

LO phase (1/f) noise ends up in band

DC offset creates tone jammer in center of band

Very high IP2 requirement at RF and at baseband

Additional practical difficulties:

IF is placed where the power supply noise is (i.e., near DC)

IM2s (as well as IM3s) are in-band

TX: LO reradiation (FCC doesn't like that...)

VCO pulling may require that LO be synthesized at a different frequency and divided down


Direct Conv. Limitations: Gain/Phase Imbalance

From [R+98]

Impact depends on modulation

I/Q correction straightforward, but usually awkward to implement

Test tones

Data-adaptive

Adaptive, low-if, no stimulus [GPO08]

From [LA02]


Direct Conv. Limitations: LO Phase Noise

Close-in phase noise (1/f noise) from the LO ends up in band

Extent of problem depends on bandwidth of signal-of-interest:

Huge problem for SSB

Major problem for GMSK (GSM)

Small or negligible problem for DSSS (as in CDMA or WiFi)

In fact, might even consider DC notch, which also mitigates of DC offset and power supply noise.

Possible solutions:

Improve LO: DDS! (becomes attractive especially in RF CMOS)

Chopping (again, particularly attractive in RF CMOS implementations)


Direct Conv. Limitations: DC Generation

Multiple causes

DC offset in either of the baseband paths creates tone jammer in center of band

Self-mixing i.e., LO feeding back into RF, puts tone at baseband

Effects

Unwelcome incursion on A/D dynamic range

Bigger problem for narrower modulations

Mitigation

Calibration (not so bad)

DC blocking caps (DC notch); also takes care of some power supply noise


Direct Conv. Limitations: High IP2 Required

Makes RF selectivity very important unfortunately one of the things that is awkward if wide tuning range is desired

Key to dealing with this as well as the self-mixing problem is common mode rejection.

This in turns screams out for differential-mode impementation:

From [BBH00]


Superhet with Direct Conversion Final Stage

Superhet contributes it's great selectivity and linearity characteristics

Maximum possible deference to ADC requirements; also convenient for I-Q modulated signals since signal is delivered in complex form

Probably most common approach currently for receivers doing anything other than analog modulations.


LO


LO

cos

sin

RF

IF

BB-I

BB-Q


Low IF Architecture

Same architecture as direct conversion except baseband center frequency is not zero.

Image sideband no longer overlaps; in fact selectivity is derived from the image rejection. This allows very wide tuning range if the I/Q balance is sufficiently good

Pros:

Avoid many of the problems of direct conversion / being near DC

Baseband IP2 can be less if IF is chosen to exclude in-band IM2

Cons:

ADC/DAC sample rates are increased by 2-3

DSP must subtract image sideband and retune signal

Very popular during 2G narrowband cellular development; now being eclipsed somewhat by new/improved direct conversion designs


Low-IF Wideband Transceiver for Ultra-High Field MRI

Application: Ultra-High Field (9T) Magnetic Resonance Imaging (MRI).

Tunes 10-400 MHz

Greater than 90 dB image rejection achieved through dynamic calibration NCOM

NCOM

A/D

A/D

DITHERGEN.

MRSIGNAL

LO

90°

BPF

BPF

DDFI

QDDF

90°

I

Q

DUC(NCOM)

I

Q

I

Q

DUC(NCOM)

I

Q

I

Q

D/A

D/A

2MSPS

32MSPS

LPF

LPF

LO

90°

16

16

32MSPS

Proof-of-concept testof receiver

Allows wide instantaneous bandwidth over a multiple-octave tuning range

Ellingson (2001) [E01]


So Where Do We Stand?

Other architectural options: Hartley, Weaver, combinations.

Emerging interest in improving RF performance by adaptive techniques:

Spectrum sensing and adaption to allow better performance with worse hardware [LD07]

Identifying and manipulating the performance-power tradeoff [T+07]

Summarizing: MMR is really no problem, as long as:

Cost is not an issue, or

Cost is an issue, but direct conversion class performance is OK

Since it is rare that either of the above are true, available solutions are typically dissapointing

Antenna limitations compound this problem




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References


Enter RF CMOS

Key idea: Implement RFICs using same dense, high-speed, inexpensive process used for modern digital circuitry

Useful background: [A04], [L04]

Key obstacles:

CMOS is fiendishly difficult to use for RF due to process variations and inaccurate design models

Very difficult to implement passive inductance

In recent years, these problems have been largely overcome by:

Learning to implement architectural approaches which are robust to process variations and inaccurate design models -- especially those using large numbers of small-valued capacitors

Exploiting availability to place dense logic to enable digitally-managed tweaking of chip as needed

Use of active inductors (gyrator = capacitor + impedance inverter) [L04]


Ways RF CMOS Changes the Problem

Very dense 90 nm now, 65 nm coming.

MMR can be implemented using multiple single-band transceivers on a single chip (whereas this would be very expensive to do with discrete transceivers)

Same substrate supports the digital logic which would otherwise be located elsewhere, allowing tight integration -- system on a chip: ADC/DAC, DDS-based LO synthesis, Baseband processing, Microcontroller and I/O functions

Reduced power requirements, especially since unused functions can be disabled

No free lunch: considerable tweaking may be required in circuit: Many parameters to be communicated over a low-speed serial port

Tight integration introduces a new problem noise mitigation. A key tool here (again) is differential signal transmission

Bottom line: Potential for acceptable performance at reduced cost


Importance of Differential-Mode Signals

Most of the sinful things that happen in RF CMOS (as well as other implementations!) are manifest as common mode signals

Undesired coupling (e.g., poor LO-to-RF isolation)

Noise from other (digital) processing on chip

IM2 generation

Fairly hopeless to deal with these when the desired signal is single-ended.

However, much can be done if the desired signal is differential [EST06].

Not a free ride though!

Antennas and external RF gadgets (like filters) are typically single-ended need balun

Differential performance depends on suppression of offsets, which can be a problem; can be addressed with feedback [A03]


The Balun Problem

Antennas and external RF gadgets (like filters) are typically single-ended need balun

A classical balun is a passive transformer which converts single-ended signals to differential form, possibly also converting impedance

Transformers have great linearity but finite bandwidth; 4:1 is typical

Space issue: A single SMT passive balun can have a footprint as large as the RFIC, and is roughly as high

Internal (CMOS) baluns are emerging... [GF08]

Challenging, because you can't use passive inductance!

As a result, these baluns are active

Pros: Tight integration, bandwidth

Cons: Linearity


Chopper Stabilization

fchop

fchop fchop fchop fchop

fchop

swap swap

Chopper stabilization [ET96], also known as dynamic matching [BBH00], is a effective method for mitigating effects of in-band 1/f noise, DC offset, and 2nd order IM

single-ended

differential


5 RX Paths (1 output) 90 nm CMOS 3 TX Paths (1 input) No inductors RX F ~ 5 dB QFP-128RX IIP2 ~ +60 dB < 400 mA @ 2.5V (RX+TX)

RX IIP3 ~ 5 dBm TX +10 dBm output

Tunes 100 - 2500 MHz (continuous)BW: 6.25 kHz 10 MHz (many steps)Sideband Rejection ~ 40 dB, up to 60 dBInternal DDSs for LO generationSSB phase noise ~ -123 dBc/Hz @ 25 kHz offsetExcellent mitigation of 1/f noise

Specs

Motorola Direct Conversion RFICCafaro et al. (2007) [C+07]


New Possibilities for MMR With Tiny RFICs

Blocking

Operation on concurrent

bands requires

frequency agility

.

.

.

RFIC BB

Non-Blocking

Ability to dwell on concurrent

bands

- DTV

- GPS (RX only)

- WLAN/WiFi

- Spectrum seeking (RX only)

.

.

.

RFIC BB

RFIC

RFIC

BB

BB

Low cost/power CMOS may make both

of these practical to implement


Other Examples of MMR-supportive RF CMOS

Inside-out SDR: Digital processing in analog domain (as opposed to analog processing in digital domain!)

Single-chip all-digital radios: Muhammad, Staszewski, and Leipold (2005) [MSL05]

800-6000 MHz, 200 kHz 20 MHz BW in 90 nm CMOSAbidi (2007) [A07]

Bitwave Semiconductor: 0.7 ~ 4.0 Ghz in 130 nm CMOS

http://www.bitwavesemiconductor.com/

Terocelo (formerly TechnoConcepts): 0.05 ~ 6 Ghz in 65 nm CMOS

http://www.technoconcepts.com/


Example: CMOS Dual-Band LNA

350 nm CMOS

2.45 / 5.25 GHz

15 dB Av

F: 2.3 / 4.5 dB

IIP3: 0 / 5.6 dBm

4 mA @ 2.5 V

Hashemi & Hajimiri (2002) [HH02]


LNA Research Trends

Perumana et al. (2008) [P+08]


Power Amplifier Research Trends

Chen, Yang & Yeh (2007) [CYY07]




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References


Duplexers and Duplexing

A duplexer is a device which interfaces a receiver and transmitter in a to a common antenna, permitting either full or half duplex operation

Duplexer typically consist of combinations of (see subsequent slides)

Circulators

Diplexers (or triplexers, or multiplexers with any number of channels)

Switches (TDD or PTT protocols)Technologies: PIN diodes, GaAs, pHEMT, (emerging) MEMS


Circulator Duplexing

Ideal from the perspective of simultaneous T/R over multiple bands

In practice, an extreme challenge to prevent receiver desense and other isolation-related problems

Used to be that compact wideband circulators were not available, but are recently becoming plausible:

From [K05] From [EST06]


From [GB05]

Diplexer-based FEMs

Industry lingo:

FEM = Front End Module

Traditional (constant-impedance) diplexers

Because receivers and transmitters are always connected, TX->RX isolation is a concern.

Receiver desense is a common problem

Necessary filtering can become expensive or intractible


Lucero et al. (2001) [L+01]

Example: Dual-Band (Cellular/PCS) Front End

GSM (900 MHz) and DCS (1800 MHz) are implemented as mostly separate transceivers

GSM and DCS are TDD protocols. Therefore, simplest to implement T/R by switching

A diplexer interfaces the two independent bands to a single (presumably dual band) antenna


From [GB05]

Triplexer-based FEM

Same as previous slide, except now GPS is accomodated by changing diplexer to a triplexer

And you thought RX desense was a problem before...;)


Tang & You (2006) [TY06]

Example: Compact Nearly-Contiguous Triplexer

Contiguous bands are more challenging due to interactions between channels


The Classical PIN Diode T/R Switch

Diode changes states in response to applied DC bias voltage

Old school but still common due to it's simple broadband effectiveness.

As always, receive desense a concern

Virtually everything that improves densense or reduces size limits bandwidth

Many enhancements possible

From [K05]

Transmission line can bereplaced by discretesbelow ~500 MHz


From [GB05]

ASM-based FEMs

Industry lingo:

ASM = Antenna Switch Module

GSM (800 MHz), DCS (1800 MHz), and PCS (1900 MHz) are all essentially the same TDD protocol, implemented at different frequencies

TDD makes multibanding through a single antenna relatively simple, except for the obvious hassle of replicated electronics and finding a suitable (triband) antenna!



For multiband operation, options are limited!

Use multiple antennas

Use one or more multiband antennas

Broadband antenna with active tuning

Perhaps someday: Non-foster matching

For additional information and background on this general topic: [E07]


Antenna Tuning

Sense Match

Characteristics

TransceiverVariable

Reactor(s)

0RZA

0R


Variable Reactors [SS98]

Switching of fixed reactances in banks

Electromechanical RF switches

PIN diodes; other semiconductors

RF Microelectromechanical Switches (RF MEMS)

Electronically-variable reactances

Motor-driven geometry changers (inductors or capacitors)

Varactor diodes (Voltage-variable capacitance)


Compact Wideband Antenna Tuner

Uses four MPV1965 Varactor Diodes, 0.5-6 pF each

Significantly improves match over about a 20% bandwidth around the tuned frequency

Of course, match is worse everywhere else...tuners can only decrease BW.

Zhou & Melde (2007) [ZM07]


Someday: RF MEMS

From [R02]

Example: MEMS tunable filter [ER05]Example: MEMS reconfigurable antenna [A+06]Nevertheless, not quite ready ... [A07b]




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References


138-174 MHz 220-222 MHz406-512 MHz764-900 MHz

Motorola RFIC Ver. 4 [C+07]

4 MSPS baseband ADC/DAC

Baseband completely implemented in FPGA

Three board stack integrates antenna, RF Mux, transceiver RFIC, ADC / DAC,ref. freq. synthesizer

Altera EP2S60 FPGA Board

Touchscreen

Ethernet

Battery underneath

Audio I/F

Off-the-shelf antenna

Virginia Tech Public Safety MMR[VTMMR]


I.M

. M

UX

1 3 8 - 1 7 4

2 2 0 - 2 2 2

4 0 6 - 5 1 2

7 6 4 - 8 6 2

4 . 9 G H z D o w n

U H F

V H F

4 . 9 G H z U p

~ 1 0 d B

( B P F )

L O

S h o r tW h i p

E x t .A n t .

~ 3 0 d B

A / D

A / D

D / A

D / A

F P G A

P

em

ula

tio

n

E m b e d d e dA n t e n n a s

8 0 0 M H z / P C S C e l l u l a r C h i p s e t

2 . 4 G H z W L A N C e l l u l a r C h i p s e t

CO

DE

CO

the

r I/

O

To

uc

hs

cre

en

Kn

ob

s

P T T

S P K RM I C

VT Tranceiver Board usingMotorola Direct Conv. RFIC100-2500 MHz, 6.25 kHz 10 MHz BW

VT Antenna-Tranceiver I/FRF Multiplexer

Baseband ADC/DAC(4 MSPS x 14/10 b) +Ref. Freq. Synthesizer

Baseband processing uses SoPC-centric approach; Currently100% Verilog HDL

VT Public Safety MMR[VTMMR]


4-Band Transceiver Board 40 mA (RX) + 40-90 mA (TX) + 80 mA/DDS @ 9V< 25 cm2 to implement on a 4-layer PCBAbout $100 in parts to implement, excluding PCB.

TR#22 for Fall 2007 version

ADC / DAC / LO Synthesizer BoardADC/DAC: 130 mA @ 9V, running 4 MSPS< 50 cm2 to implement on a 4-layer PCB

ADC ~ $21 (1k), DAC ~ $10 (1k)

These two boards stack vertically with the RFFE board using MMCX connectors (no RF cables)

VT Public Safety MMR[VTMMR]


Meeting selectivity specs is one of the big challenges for this architecture

Our approach: RF multiplexer optimized to antenna impedance with external noise dominance constraint

No antenna tuning!

Simultaneous access to

multiple bands

Transducer power gain for RF multiplexer optimized for a 20 cm long monopole antenna

External noise dominance inVHF-High and 220 MHz bands

VT Public Safety MMR: Antenna IntegrationHasan & Ellingson (2008) [HE08]

(above results are simulations)




Radio Design Basics

Antennas

Digitization


Linearity



RF CMOS



Summary

Acknowledgements

References


Summary Remarks

MMR is enabling technology for military-type SDR and frequency-agile cognitive radio. It also has applications independently of these application areas: All-in-ones, public safety, ...

MMR has always been possible... but big, hot, and expensive

What is fueling progress & enthusiasm about MMR now is the prospect for achieving acceptable RF performance at much lower cost and power consumption. Key techologies:

Continued improvements in direct conversion and digital RF transceivers in CMOS

Antenna multibanding, physical integration, electrical integration (e.g., self-diplexing) and other forms of codesign

MEMS for reconfigurable antennas, matching circuits, and filters

There is still much to do. The next few years will be very interesting!


Acknowledgements

Students:

S.M. Shajedul Hasan

M. Harun

K.H. Lee

The author gratefully acknowledges the assistance and material support of Motorola Laboratories, Plantation, FL. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Motorola Corp.

This material is based upon work supported in part by the National Institute of Justice, U.S. Dept. of Justice, under Grant No. 2005-IJ-CX-K018. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. Government.


References

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Solid State Circuits, Vol. 35, No. 12, Dec 2000, pp. 1934-1941.[C07] S. Cripps, The Intercept Point Deception, IEEE Microwave Mag., Feb 2007, pp. 44-50[CHE08] J. Craig, M. Harun, and S. Ellingson, On-the-Air Demonstration of a Prototype LWA Analog Signal Path, LWA Memo 130, Apr 2008. [online] http://www.phys.unm.edu/~lwa/memos [CYY07] Y.-J. E. Chen, L.-Y. Yang, and W.-C. Yeh, An Integrated Wideband Power Amplifier for Cognitive Radio, IEEE

Trans. Microwave Theory & Techniques, Vol. 55, No. 10, Oct 2007, pp. 2053-8.[C+05] C. Cho et al., IIP3 Estimation From the Gain Compression Curve, IEEE Trans. Microwave Theory &

Techniques, Vol. 53, No. 4, Apr 2005, pp. 1197-1202.[C+07] G. Cafero, A 100 MHz 2.5 Ghz Direct Conversion CMOS Transceiver for SDR Applications, 2007 IEEE RFIC

Symp., Jun 2007.[E01] S.W. Ellingson, "MRI Transceiver", U.S. Patent No. 6,259,253, July 2001.[E05a] S.W. Ellingson, "Antennas for the Next Generation of Low Frequency Radio Telescopes," IEEE Trans. Antennas and Propagation, Vol. 53, No. 8, August 2005, pp. 2480-9. [E05b] S.W. Ellingson, Spectral Occupancy at VHF: Implications for Frequency-Agile Cognitive Radios, IEEE Vehicular

Technology Conf., Vol. 2, Dallas TX, Sep 2005, pp. 1379-82.[E06] S.W. Ellingson, A Comparison of Some Existing Radios with Implications for Public Safety Interoperability, Virginia Tech Project Technical Report No. 4, Jun 2006. [on-line] http://www.ece.vt.edu/swe/chamrad.


References

[E07] S.W. Ellingson, Active Antennas (short course notes), 2007. Contact [email protected].[ER05] K. Entesari and G.M. Rebeiz, A Differential 4-bit 6.5-10 Ghz RF MEMS Tunable Filter, IEEE Trans. IEEE Microwave

Theory & Techniques, Vol. 53, No. 3, March 2005, pp. 1103-1110. [EST06] W.R. Eisenstadt, B. Stengle, B.M. Thompson, Microwave Differential Circuit Design using Mixed-Mode S-

Parameters, Artech House, 2006.[ET96] C.C. Enz and G.C. Temes, Circuit Techniques for Reducing the Effects of Op-Amp Imperfections: Autozeroing, Correlated Double Sampling, and Chopper Stabilization, Proc. IEEE, Vol. 84, No. 11, Nov 1996, pp. 1584-1614.[F+07] A. Faraone et al., Enabling Antenna Technologies for the Software Definable Radio, 2nd European Conf. Ant. & Prop.

(EuCAP2007), Nov 2007, pp. 1-6. [GB05] W.-C. A. Gu and B. Balut, Integration of Cellular Handset RF Front-End Modules, Microwave Product Digest, June 2005.[GF08] B. Godara and A. Fabre, A Highly Compact Active Wideband Balun With Impedance Transformation in SiGe BiCMOS, IEEE Trans. Microwave Theory and Techniques, Vol. 56, No. 1, Jan 2008, pp. 22-30.[GPO08] A. Gimeno-Martin, J.M. Pardo-Martin, and F.J. Ortega-Gonzalez, Adaptive Algorithm for Increasing Image Rejection Ratio in Low-IF Receivers, Electronics Letters, Vol. 44, No. 6, Mar 2008.[G+08] C.J. Galbraith et al., Cochlea-Based RF Channelizing Filters, IEEE Trans. Circuits & Systems I, Vol. 55, No. 4, May 2008, pp. 969-79.[H05] T. Hentshel, The Six-Port as a Communications Receiver, IEEE Trans. Microwave Theory & Techniques, Vol. 53, No. 3, Mar 2005, pp. 1039-1047.[HH02] H. Hashemi and A. Hajimiri, Concurrent Multiband Low-Noise Amplifiers Theory, Design, and Applications, IEEE

Journal of Solid-State Circuits, vol. 50, no. 1, Jan 2002, pp. 288-301.[HE06] S.M.S. Hasan & S.W. Ellingson, A Wideband RF Downconverter for the NIJ Public Safety Radio, Virginia Tech Project Technical Report No. 16, Dec 2006. [on-line] http://www.ece.vt.edu/swe/chamrad. [HE08] S.M.S. Hasan & S.W. Ellingson, Multiband Antenna-Receiver Integration using an RF Multiplexer with Sensitivity-Constrained Design, IEEE Int'l Symp. Ant. & Prop., San Diego, CA, July 2008. (Preprint available: see [VTMMR])[H+07] I. Hunter, Microwave Filter Design from a Systems Perspective, IEEE Microwave Mag., Oct 2007, pp. 71-7.[ITU03] ITU-R: Radio Noise, Rec. P.372-8, 2003. [J08] D. Jackson, A Corner Turned, MRT (magazine), May 2008, pp. 36-41.[K05] P.B. Kenington, RF and Baseband Techniques for Software Defined Radio, Artech House, 2005.


References

[[KA00] P.B. Kenington and L. Astier, Power Consumption of A/D Converters for Software Radio Applications, IEEE Trans.

Vehicular Technology, Vol. 49, No. 2, Mar 2000, pp. 643-50.[HC85] B.C. Henderson and J.A. Cook, Image-Reject and Single-Sideband Mixers, Watkins-Johnson Co. Tech-note, Vol. 12, No. 3, May/Jun 1985.[ITU03] ITU-R: Radio Noise, Rec. P.372-8, 2003. [J08] D. Jackson, A Corner Turned, MRT (magazine), May 2008, pp. 36-41.[K05] P.B. Kenington, RF and Baseband Techniques for Software Defined Radio, Artech House, 2005.[KA00] P.B. Kenington and L. Astier, Power Consumption of A/D Converters for Software Radio Applications, IEEE Trans.

Vehicular Technology, Vol. 49, No. 2, Mar 2000, pp. 643-50.[HC85] B.C. Henderson and J.A. Cook, Image-Reject and Single-Sideband Mixers, Watkins-Johnson Co. Tech-note, Vol. 12, No. 3, May/Jun 1985.[L04] T.H. Lee, The Design of CMOS Radio-Frequency Integrated Circuits, 2nd Ed., Cambridge University Press, 2004.[LA02] A. Loke and F. Ali, Direct Conversion Radio for Digital Mobile Phones Design Issues, Status, and Trends, IEEE

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Frequency Integrated Circuits Sym., 2001, pp. 213-6.[MSL05] K. Muhammad, R.B. Staszewski, and D. Leipold, Digital RF Processing: Toward Low-Cost Reconfigurable Radios, IEEE Communications Magazine, Aug 2005, pp. 105-113.[MYJ80] G. Matthaei, L. Young, E.M.T. Jones, Microwave Filters, Impedance-Matching Networks, and Coupling Structures, Artech House, 1980.[O05] S. Ooi, Wideband Monopole Antenna for Public Safety Radio, IEEE Int'l Symp. Ant. & Prop., Vol. 2A, Jul 2005, pp. 363-6.


References

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