multiband transceivers - [chapter 7] multi-mode/multi-band gsm/gprs/tdma/amps system analysis

Multiband RF Transceiver SystemChapter 7

Multiband/Multi-modeGSM/GPRS/TDMA/AMPS

RF Transceiver System Analysis

Department of Electronic EngineeringNational Taipei University of Technology

Outline

• GSM/GPRS/TDMA/AMPS Transceiver Architecture

• Frequency Plan and Specifications

• Noise Figure Requirement Calculation

• Linearity Requirement Calculation

• Selectivity and Blocking Performance Evaluation

• Summary

Department of Electronic Engineering, NTUT2/38

Introduction

• A multimode and dual-band superheterodyne transceiverdesign, which actually covers the designs of GSM, TDMA,AMPS and GPRS mobile systems, is discussed.

• We’ll first take a look at the architecture of this multi-modetransceiver. Lately, the specifications of theses applicationswill be given with some tables.

• For the receiver, there are things to be done:

(1) Noise Figure: BER� Eb/N0 � CNR� Sensitivity� NF

(2) IIP3 : IMD requirement� CNR� Phase Noise/NF� IIP3

(3) Selectivity and Blocking


GSM/GPRS/TDMA/AMPS Transceiver

• Band: 800 MHz cellular and 1900 MHz PCS dual bands.LNA SW control

Cellular band

PCS band

LNA

LNA

Rx RFSAW

Rx RFSAW

GSMSAW

TMDA/AMPSSAW

IF VGA

I/Q downconverter

BBA

BBABB filter

BB filter

To BB

f/2VHF PLLAt 266.4/

268.04 MHz

Diplexer

Bia

s a

nd c

ont

rol

Ref. Clck

Rx chip

Tx chipCe

llula

r du

plex

er

PC

S d

uple

xer

From LoopLPF

1002– 1028.1MHz VCO

2063– 2124.1MHz VCO

PA

PA

Tx RF SAW

Tx RF SAW

Powerdetector

BB

Driver

Driver

PCS band

Cellular band

AFC VCTCXO

To VCOsLoop LPF

To BB

UHF synthesizer

Ref. Clock

Single side bandUp-converter

130.38 MHzOr

250.76 MHz

VHF PLLAt 521.52 (cell)Or 501.52 (PCS)

MHz

IFVGA

f/2

Σ To BB

Bia

s an

d co

ntr

ol

BB I

BB Q

To UHFsynthesizer

200 kHz

25 kHz

tunable


Frequency Plan (I)

• Half-duplex system: GSM, GPRS, and TDMAmode

• Full-duplex system: AMPS mode.

• 70 MHz span

• 1st IF > 70 MHz

� Choose 133.2 MHz for GSM and GPRS RX(200kHz ch spacing)

� Choose 134.04 MHz for TDAM and AMPS RX(30 kHz ch spacing)

• Common reference clockis used

• 19.2 MHz reference clockis popular used in mobilestations.

SystemUplink (MHz)

Downlink (MHz)

Separation(MHz)

Channel Spacing(kHz)

Cellular 824 – 849 869 – 894 20 30 (CDMA)

GSM 900 890 – 915 935 – 960 20 200

E-GSM 900 880 – 915 925 – 960 10 200

DCS 1800 1710 – 1785 1805 – 1889 20 200

PCS 1850 – 1910 1930 – 1990 20 50 (CDMA)

WCDMA 1920 – 1980 2110 – 2170 130 200

802.11b 2400 – 2484 2400 – 2484 – 13000

802.11a5150 – 5350 5725 – 5825

5150 – 53505725 – 5825

––

2000020000


Frequency Plan (II)

• UHF synthesizers frequency tuning range (high-side injection):

� 800 MHz cellular band:1002 to 1029 MHz

� 1900 MHz PCS band: 2063 to2125 MHz

GSM and GPRS TDMA and AMPS

VCTCXO 19.2 19.2

Receiver IF (MHz) 133.2 134.04

Transmitter IF (MHz) 178.2 179.04

UHF VCO Tuning (MHz) 2004 – 2058 2063 – 2125

Receiver VHF VCO (MHz) 266.4 268.08

Transmitter VHF VCO (MHz) 356.4 358.08

Use a single VCO with a tuning range 2004 to 2125 MHz and a divide-by-2divider. (2004 to 2125 MHz is about 6% of the VCO operating frequency,and this is a quite reasonable tuning range that still maintains good phasenoise performance)


Multi-Standard Specifications


GSM RX Specifications (I)

GSM & GPRS 800/1900 Specifications Note

Frequency Band 869~894 or 1930~1990 MHz

Modulation GMSK

Symbol rate 270.833 ksps

Sensitivity < −102 dBm RBER < 2%

800 MHz band GPRS sensitivity (packet data channel)

< −100 dBm BLER < 10%

1900 MHz band GPRS sensitivity (packet data channel)

< −102 dBm BLER < 10%

800 MHz dynamic range > −15 dBm RBER < 0.1%

1900 MHz dynamic range > −23 dBm RBER < 0.1%

Intermodulation spurious response attenuation > −49 dBmf1: ±800 kHz offset (CW)f2: ±1.6 MHz offset (Mod)

Table A

1

2

3


GSM RX Specifications (II)

GSM & GPRS 800/1900 Specifications Note

Adjacent channel selectivity > 9 dBc ±200kHz offset, 2% BER

Atl. adjacent channel selectivity > 41 dBc ±400kHz offset, 2% BER

Blocking characteristic > 49 dBc ±(600 kHz to 1.6MHz) offset, 2% BER

Blocking characteristic > 66 dBc ±(1.6 MHz to 3MHz) offset, 2% BER

800 MHz blocking characteristic > 76 dBc > 3 MHz offset, 2% BER

1900 MHz blocking characteristic > 73 dBc > 3 MHz offset, 2% BER

800 MHz spurious emission <−79 dBm/100 kHz In Receiver Band

1900 MHz spurious emission < −71 dBm/100 kHz In Receiver Band

Spurious emission < −36 dBm/100 kHz In Transmitter Band

Table B


TDMA RX Specifications

TDMA 800/1900 Specifications Note

Frequency band 869~894 or 1930~1990 MHz

Modulation π / 4 DQPSK

Symbol rate 24.3 ksps

Sensitivity < −110 dBm BER < 3%

Dynamic range > −25 dBm BER < 3%

Intermodulation spuriousresponse attenuation

> 62 dBcf1: ±120 kHz offset (CW)f2: ±240 kHz offset (CW)

Adjacent channel selectivity > 13 dBc ±30 kHz offset, 3% BER

Atl. Adj. channel selectivity > 42 dBc ±60 kHz offset, 3% BER

Spurious emission < −80 dBm In receiver band

Table C

1

2


AMPS RX Specifications

AMPS 800/1900 Specifications Note

Frequency Band 869 – 894 MHz

Modulation FM

Noise Bandwidth ~27 kHz

Sensitivity < −116 dBm SINAD = 12dB

Dynamic range > −25 dBm

Intermodulation spurious response attenuation > 65 dBcf1: ±60 kHz offset (CW)f2: ±120 kHz offset (CW)

Intermodulation spurious response attenuation > 70 dBcf1: ±330 kHz offset (CW)f2: ±660 kHz offset (CW)

Adjacent channel selectivity > 16 dBc ±200 kHz offset, 2% BER

Atl. Adjacent channel selectivity > 60 dBc ±400 kHz offset, 2% BER

Spurious emission < −80 dBm In receiver band

Table D

1

2

3


Noise Figure Requirement Calculation


CNR for GSM

• In the receiver systemdesign, we need to first determine thecarrier-to-noise ratio (CNR) for each operation mode at aspecified BER.

• RBER < 2% for GSM speech channel (TCH/FH Class II).

We use BT=0.25 here to evaluate(actually, GSM is 0.3), and get

Eb/N0 = 5 dB

Next step is to find the required CNR.

1(Table A )

Eb/N0 (dB)

Bit

Err

or

Rat

e


Impairments Consideration

• Consider impairments:Eb/N0 = 5.6 dB

• Bit rate = 271 kHz and the RXnoise BW = 182 kHz (thechannel selection filterBW), thus theCNR:

• We can useCNRGSM = 8 dB to reserve 0.7 dB margin

Item Specification Eb/N0 Degradation

Total integrated phase noise of two LOs < −25 dBc 0.1

Group delay distortion of channel filters < 2 µsec 0.4

I andQ imbalance in phase and magnitude < 5° and < 0.5 dB 0.1

0

27110log 5.6 10log 7.3 dB

182b b

GSM

E RCNR

N BW= + = + =

0.6 dB degradation from impairments

(see Ch3 slide-24)

�


Other Considerations

• However, when the speech channel with AMR (adaptivemultiple rate), the requiredCNR for the same sensitivity of−102 dBmwill be approximately 1.5 dB higher than that of theoriginal speech channels - i.e., (8 + 1.5) = 9.5 dB.

• The requirement on theCNR in the worst case is the channelTCH/AFS5.9 in HT100 propagation condition:

For a −102 dBm sensitivity 9.4 dB CNR is needed evenwithout AMR.


CNR for GPRS

• The correspondingCNR for a 10%block error rate (BLER) inpacket data channels (PDCH) is in general approximately8 dBas required by the GSMspeech channels, but in the worst case,it may rise to close to10 dB.

• However, the reference sensitivity of the GPRS in the worstcase (PDCH/CS-4 in 1800 MHz band, for example) is relaxedto −100 dBminstead of−102 dBm.

• For simplicity, the performance evaluation of the GSMandGPRS systemRF receivers later on will be based onCNRmin = 8 dB.

2(Table A )

In the practical system design we should leave enoughmargin to cover the performance in the worst caseincluding GSM speech channel with AMR.

�


CNR for TDMA (I)

• In a similar way, we can determine theCNR for performancecalculation of the TDMAreceiver where the signal isπ/4 -DQPSKmodulated.

1(Table C )

Eb/N0 (dB)

Bit

Err

or

Rat

e

Eb/N0 degradation due to ISI from IF (SAW + ceramic) filters

• Eb/N0 for a 3% BER isapproximately equal to 5dB in the case of ISI free.


CNR for TDMA (II)

• Assume that the channel filters have a total group delaydistortion 1.5 ps, which causes 0.3 dBEb/N0 increase to keepthe 3% BER, and the other factors such asI and Q channelmismatching and the phase noise of the LOs raiseEb/N0another 0.2 dB.

• Therefore, it needs total 5.5 dB to reach 3% BER.

• ConsideringRb/BW = 2 (2-bits/symbol) in the case ofπ/4-DQPSKmodulation, we obtainCNR to be

• Similar to the GSMsituation, we add 0.5 dB to the aboveCNRTDMA value for performance evaluation of the TDMAmobile receiver:CNRTDMA = 9 dB.

5.5 10log 2 8.5 dBTDMACNR ≅ + = (see Ch3 slide-24)

�


CNR for AMPS (Analog Wireless System)

• The SINAD is used in an analog AMPS (FM) to measure thesensitivity and other performance instead of BER.

• The SINAD value defined to measure AMPS receiverperformance is 12 dB, and we useCNRAMPS = 3.0 dB(approximately 0.5 dB higher than the readCNR value).

( )10log dBS N D

SINADN D

+ +=+

( )( )

( ) ( ) ( )

( )

2

2 2

2

32

1 123

11

oC N

C N

f BWC N

B BS NBW f

C N e C NB BW

eπ

−

−

∆ =

∆ + +

−

( ) ( )10log 10log poSNR S N S N G= = +

(Not SNDR)1(Table D )

CNRAMPS (dB)

SIN

AD

(d

B)

�

( )

( )

6 2 20 10

6 2 20 10

1 10 1010log

10 10

p

p

SNR G SNR SNR

SNR G SNR SNRSINAD

− − + − −

− − + − −

+ +=+


Required Noise Figure

• The receiver static sensitivity is determined by the noisebandwidth, noise figure, andCNR.

Usually we would like to have a 4 dB margin in the typical case and a 1.5 dBmargin in the worst case.

( )3174 106 10log 182 10 8 7.4 dBGSMNF = − − × − ≅

( )3174 114 10log 27 10 9 6.7 dBTDMANF = − − × − ≅

( )3174 120 10log 27 10 3 6.7 dBAMPSNF = − − × − ≅

(see Ch4 slide-8, we didn’t consider digitalprocessing improvement here)

The NF of this multimode receivershall be 6.7 dB or lower. Themaximum NF should be 9.2 dB orless, and thus the sensitivity still has1.5 dB margin in the worst case.

Spec. GSM/GPRS TDMA AMPS

Noise Floor −174 dBm/Hz −174 dBm/Hz −174 dBm/Hz

Sensitivity (Spec.) −102 dBm −110 dBm −116 dBm

Margin 4 dB 4 dB 4 dB

Sensitivity (Target ) −106 dBm −114 dBm −120 dBm

Noise Figure Requirement 7.4 dB 6.7 dB 6.7 dB


Linearity Requirement Calculation


Linearity and IIP3

• Receiver linearity is usually measured by theIIP3.

• The linearity requirement is more complicated to determinethan the receiver noise figure.

• The requirement on the overallIIP3 of a wireless mobilereceiver is dominated by the allowed intermodulationdistortion (IMD) or formally referred to as intermodulationspurious attenuation and the phase noise of UHF synthesizerLO.


IMD Performance Requirements

• GSM: Desired signal −99 dBm (−102+3)

Minimum interferers −49 dBm

Tone/modulated interferer, offset frequency ±800/±1600 kHz

• TDMA: Desired signal−107 dBm (−110+3)

Minimum interferers 62 dBc higher;

Tone/tone interferer, offset frequency ±120/±240 kHz

• AMPS: Desired signal −−−−113 dBm (−116+3)

Minimum close-spaced interferers 65 dBc higher

Close-spaced tone/tone interferer, offset ±120/±240 kHz

Minimum wide spaced interferers 70 dBc higher

Wide-spaced tone/tone interferer, offset±330/±660 kHz.

3(Table A )

2(Table C )

2(Table D )

3(Table D )


You may like to evaluate the desired signal power with thesensitivity (target), e.g., −106 dBm, calculated in slide-20.

Calculate IIP3 by Ignoring Other Influence

• If ignoring other factor influence to the intermodulation:

( )3,min , ,min , min

13

2d i in d iIIP S I S CNR = + − + , min_ 3 dBd i refS S= + : Receiver input desired signal

,mininI : Minimum input interference strength

min_refS

, mind iS CNR−

min3IIP,mininI

( )

( )

,min , minmin , min

, ,min , min

3 32

1 3

2

in d id i

d i in d i

I S CNRIIP S CNR

S I S CNR

− += ⋅ + −

= + − +

3 dB

,d iS

input@Iout,min reaches

minCNR

minCNR,minoutI


Estimated IIP3

• If ignoring other factor influence to the intermodulation:

( )3,min , ,min , min

13

2d i in d iIIP S I S CNR = + − +

[ ]3,min

199 3 49 8 21.5 dBm

2GSMIIP = − + × + = −

[ ]3,min

1107 3 62 9 9.5 dBm

2TDMAIIP = − + × + = −

[ ]3,min

1113 3 65 3 14 dBm for close-spaced

2AMPSIIP = − + × + = −

[ ]3,min

1113 3 70 3 6.5 dBm for wide-spaced

2AMPSIIP = − + × + = −

Spec. GSM/GPRS TDMA AMPS

Desired signal −99 dBm −107 dBm −113 dBm

Spurious ResponseAttenuation

49 dBc 62 dBcclose wide

65 dBc 70 dBc

CNRmin 8 dB 9 dB 3 dB 3 dB

Required IIP3 −21.5 dBm −9.5 dBm −14 dBm −6.5 dBm


Consider Other Influence

• LO phase noise, spurious, and the receiver noisefigure will also impact the IMDperformance:

The LO phase noise and spurious level, especially at the offset frequenciesequal to those frequencies where the intermodulation test interferers arelocated, should be low enough to ensure that the requested receiver IIP3 forcertain IMD performance is reasonable and feasible.

• The VHF LOphase noise and spurious:Generally have a negligible impact on the IMD performance if the IF channelfilter has good rejection to the interferers.

max, 2 2 2 210 10

3,min ,min , , , ,1 1 1 1

13 10log 10 10

2

nfin ND

in phn j k spu j kj k j k

IIP I P P= = = =

= − − − −

∑∑ ∑∑


LO Phase Noise

Cellular Band Synthesizer PCS Band Synthesizer

Frequency Offset (kHz)

Phase Noise (dBc/Hz)

Spurs (dBc)Phase Noise

(dBc/Hz)Spurs (dBc)

±30 kHz −105 −60 −103 −60±60 kHz −117 −85 −114 −85±120 kHz −125 −90 −122 −90±240 kHz −131 −95 −128 −95±330 kHz −134 −95 −131 −95±660 kHz −140 −95 −137 −95±3000 kHz −144 −95 −142 −95

800 MHz Band 1900 MHz Band

Frequency Offset (kHz)

Phase Noise (dBc/Hz)

Spurs (dBc)Phase Noise

(dBc/Hz)Spurs (dBc)

±200 kHz −118 −60 −114 −60±400 kHz −124 −65 −120 −65±600 kHz −127 −70 −123 −70±800 kHz −130 −78 −126 −78±1600 kHz −136 −85 −132 −85

> |3200 k| Hz −141 −90 −137 −90

The phase noise may vary a couple of dB with temperature from room to hot (60°C) or to cold (-30°C).

For

TD

MA

and

AM

PS

For

GS

M

3(Table A )

Table E

Table F


Required IIP3 Estimation (I)

• The required IIP3 of 800 MHz band GSMreceiver iscalculated by using phase noise for GSMas

• The required IIP3 of 1900 MHz band GSMreceiver is

• In a similar way, we can obtain IIP3 for other modes andbands based on phase noise and spurious for TDMA/AMPSLO as follows.

3, _1900 14.8 dBmGSMIIP = −

3, _1900 2.8 dBmTDMAIIP = −

3, _800 3.4 dBmTDMAIIP = − 3, _ 12.6 dBmAMPS closeIIP = −

3, _ 9.3 dBmAMPS wideIIP = −

( )3 3 3 85 49 3

1099 8 174 7.4 10log182 10 130 10log182 10 49 3 136 10log182 10 49 3 78 49 3

10 10 10 10 103, _ 800

13 49 3 10log 10 10 10 10 10 10 15 dBm

2GSMIIP− − +− − − + + ⋅ − + ⋅ − + − + ⋅ − + − − +

= − + − − − − − − = −

3(Table A )

3 dB margin

PN@800 kHz PN@1600 kHz

Spurious@800 kHz Spurious@1600 kHz

Use NF=7.4 for GSM


Required IIP3 Estimation (II)

• Fromthese results we can conclude that:

TDMA receiver requires the highest linearity, and the receiver operating in the1900 MHz band needs higher IIP3 than when it is running in the 800 MHz bandsince the phase noise of the PCS band LO is worse than that of the cellular bandLO.

• The linearity design of the receiver common path for differentmodes should bebased on the TDMA requirement, but in thecircuit design we should also consider adjustable bias circuitryto change the device bias based on operation modes to save thecurrent consumption.


Selectivity and Blocking Performance


Selectivity and Blocking Performance

• Receiver selectivity and blocking performance are mainlydetermined by :

� Channel filters

� LO phase noise

� Spurious

• The LO phase noise/spurious requirements is also partiallydetermined by the IMDperformance, and therefore we havealready had a basic idea what level phase noise/spurious canbe used in our receiver systemdesign.


Channel Selection Filtering

• The channel filter characteristics affect not only the receiverselectivity and blocking performance but also the IMDperformance.

Since no matter what the adjacent/alternate channel interferers are, distanceblocking signals, or intermodulation interference tones/modulated signals will besignificantly attenuated when they pass through the channel filters.

• It is a trial and error procedure to make a tradeoff betweenfiltering requirements and feasibility of implementation.

• Examples of channel filter characteristics for the GSMreceiver and for the TDMAor the AMPS receiver arepresented in Table next slide.


Channel Filter Characteristics

GSM Channel Filter TDMA/AMPS Channel Filter

Insertion Loss (dB) Insertion Loss (dB)

Typical Worst Typical Worst

In-band 4.5 5.5 In-band 3.5 4.5

Rejection (dB) Rejection (dB)

Offset frequency

Typical WorstOffset

frequencyTypical Worst

±200 kHz 4 0 ±30 kHz 3 0

±400 kHz 17 12 ±60 kHz 24 20

±600 kHz 27 22 ±120 kHz 40 35

±800 kHz 31 25 ±240 kHz 50 40

±1600 kHz 40 30 ±330 kHz 45 40

±3000 k Hz 40 30 ±660 kHz 43 35

Table G


Calculate Selectivity and Blocking

• Utilizing

• GSM adjacent channel selectivity:

,

,1 ,2 ,1 ,2

174 10log

10 10

/ / / / , ,10log 10log

10 10 10 10

10 1010log

10 10 10 10

d i

phn phn IF spu spu IF

S CNR BW NF

adj alt block adj alt block d i d iN BW N R BW N N RS I S S

− − + +

+ −∆ + −∆

− ∆ = − = −

+ + +

3

3 3

99 8 174 10log182 10 7.4

10 10

118 10log182 10 108 4 10log182 10 60 55 4

10 10 10 10

10 1010log 99 46.8 dB

10 10 10 10adjS

− − − + ⋅ +

− + ⋅ − − + ⋅ − − −

− ∆ = + =

+ + + Rejeciton@200 kHz (adjacent ch.)Spurious@200 kHzPN@200 kHz

VHF LO, IF rejection (LO performance not shown here)

UHF LO


AMPS Adjacent Channel Selectivity

• The AMPS adjacent channel selectivity is calculated in asimilar way:

In the above selectivity calculations, it is assumed that the VHF LO phase noise atthe corresponding adjacent channel is 10 dB worse than the UHF LO phase noiseand the spurious is 5 dB worse.

• The results showmargins over 37 and 29 dB, respectively, forGSM and AMPS cases.(GSM > 9 dBc, Table B; AMPS > 16 dBc, Table D)

3

3 3

117 3 174 10log27 10 6.710 10

105 10log27 10 95 10log27 10 3 60 55 3

10 10 10 10

10 1010log 120 45.1 dB

10 10 10 10adjS

− − − + ⋅ +

− + ⋅ − + ⋅ − − − −

− ∆ = + =

+ + + Rejeciton@30 kHz (adjacent ch.)Spurious@30 kHzPN@30 kHz

VHF LO, IF rejection (LO performance not shown here)

UHF LO


Selectivity and Blocking Performance (I)

• The adjacent/alternate channel selectivity andblocking performance can be estimated with theformula given in previous slide.

• Estimated GSMperformance:


GSM mobile receiverLoose LO(Table F)

MarginTight LO(Table E)

MarginLoose LO(Table F)

MarginTight LO(Table E)

Margin

Adjacent channel (dBc) 45.8 36.8 49.4 40.4 45.7 36.7 50.3 41.3

Alternate channel (dBc) 54.0 13.0 56.2 15.2 54.0 13.0 55.9 14.9

Block 0.6 – 1.6 MHz (dB) 59.9 3.9 61.1 5.1 58.3 2.3 60.9 4.9

Block 1.6 – 3.0 MHz (dB) 72.4 6.4 74.9 8.9 69.5 3.5 74.2 8.2

Blocking > 3 MHz 79.4 3.4 82.0 6.0 75.4 2.4 80.1 4.1


Selectivity and Blocking Performance (II)


TDMA mobile receiver Tight LO Margin Tight LO Margin

Adjacent channel (dBc) 41.2 28.2 40.9 27.9

Alternate channel (dBc) 62.4 20.4 59.6 17.6

AMPS mobile receiver Tight LO Margin Tight LO Margin

Adjacent channel (dBc) 45.1 29.1 NA NA

Alternate channel (dBc) 66.2 6.2 NA NA

• Estimated TDMA/AMPS performance:


Summary

• To estimate the required receiver noise figure, onecan start fromthe BERand sensitivity specifications.

BER � Eb/N0 � CNR � Sensitivity � NF

• One can start fromthe IMD requirement, and utilizethe determinedCNR and noise figure to estimate IIP3requirement.

IMD requirement � CNR � Phase Noise/NF � IIP3

• Selectivity and blocking performance needs someinformation, such as filter responses and 1st LO/2nd

LO performance, and sometimes it requires tedious“trial and error” analysis.
