Simplified Transceiver Architecture

Role of a Transmitter 0 90 A D A D HPMX-2007 The lkhefw wlkhq wilehr wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q The lkhefw wlkhq wilehr wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw The lkhefw wlkhq wilehr wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. Power Supply Power Amplifier Mixer Oscillator Baseband Processor Modulator bias I Data Q Data 1. create carrier 2. add data to carrier 4. amplify to broadcast 3. shift to high frequency Information Antenna bias uP/ DSP Transceiver

Role of a Receiver 0 90 A D A D HPMX-2007 The lkhefw wlkhq wilehr wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q The lkhefw wlkhq wilehr wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw The lkhefw wlkhq wilehr wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. esjlkh qwh wlh lihewrw wklhjr qlih qilh q q3wih q wejklh wajkhrqwilu wae. Power Supply uP/ DSP Low Noise Amplifier Mixer Oscillator Baseband Processor De-Modulator bias I Data Q Data 1. amplify received signal with min. added noise 2. shift to lower frequency (cost and/or performance) 3. LO for down conversion 4. discard carrier and recover data Information bias Antenna

Mixer = Multiplying  up/down conversion Frequency translation device Ideal mixer: –Doesn’t “mix”; it multiplies A B AB

Image problem converting to IF A 1 cos( w RF t) A has desired signal at  IF plus an interference at  IM A 2 cos( w IM t) B is at  LO And:  RF -  LO =  LO -  IM =  IF Both converted to IF, Can ’ t be cleaned once corrupted

Image Problem

Problem of Image Signal

Solution: Image Rejection Filter

Problem of Half IF Second order harmonic

Superheterodyne Receiver

Multi IF Stage Receivers Received RF signal is down converted stage by stage until the desired final IF is obtained Frequency conversion ratio of each stage is usually kept lower than 10. –For example, RF 1800 MHz  IF1 450 MHz, then  IF2 90 MHz, and finally  IF3 18 MHz. –Corresponding ratios are: 4; 5; 5; total 100. Each stage has it’s own image problem Each stage requires demanding filtering –Typically done off chip or using SAW –Complicated, bulky, expensive

IF and LO frequency selection Fixed RF filter before LNA for band selection –One for each standard –Off-chip, high quality, no freedom IF frequency is selected at design –Fixed for each product LO frequency is tuned in real time –|RF–LO|=IF –Actual RF freq depends on which channel is assigned to device –LO tuning range must cover RF bandwidth

Superheterodyne Receiver(cont.)

Selection of IF If IF is large, –better separation between RF and image –better image rejection –easier image rejection filter design –More stages of down conversion Other IF selection criteria –Select IF so that image freq is outside of RF band –  IF >= (RF BW)/2 Sometime may not be possible, if (RF BW)/2 is within RF Band

For each channel assignment, there are two choices of LO freq that meets the requirement |RF–LO|=IF. Q: should LO > RF, or LO < RF??

Example: AM Radio AM radio band: 530 to 1610 KHz BW/2 = ( )/2=1080/2=540, in band IF has to be lower. Commonly: 455kHz Image can be in AM band If LO is on low side, LO tuning range is: –(530 to 1610) – 455 = (75 to 1155) –LO lowest to highest is a factor of 15.4 If LO is on high side, LO tuning range is: –(530 to 1610) = (985 to 2065) –LO lowest to highest is a factor of 2.01

Direct Conversion Receiver No image problem

Direct Conversion Receiver LO is at same frequency as RF 1/f noise here can end up in channel Self mixing cause DC problem + Eliminate IF SAW, IF PLL and image filtering + Integration + Avoids image problem - Quadrature RF down conversion required - DC problem - Typically requires offset or 2x LO to avoid coupling

DC Offset (Self-mixing) A D  c a LO (t)=A LO cos(  c +  ) 0 A D  c 0 capacitive coupling substrate coupling bondwire coupling Saturates the following stages

DC Offset (Self-mixing) level DC Offset + - t

DC Offset Cancellation Capacitive Coupling –Requires a large capacitor Negative Feedback –Nonlinear TDMA Offset Cancellation –Requires a large capacitor -A

1/f noise effect CMOS transistors has significant 1/f noise at low to DC frequency Significantly noise performance of direct conversion receivers Receive signal 1/f noise f

Even-Order Distortion Direct feed through

Mirror Signal Upper sideband and lower sideband are identical

Mirror Signal Upper sideband and lower sideband are not identical

Mirror Signal Suppression A D 0 90 A D a(t) u i (t) u q (t) v i (t) v q (t) Quadrature Down Conversion I Q

Quadrature Conversion

Quadrature Down Conversion

I/Q Mismatch 0 90 I Q Phase & Gain Error a(t)

I/Q Mismatch due to LO errors

Phase error Gain error Effect of gain mismatch Effect of phase mismatch

Use of I/Q down conversion recovers the nonsymmetrical receive signal spectrum But port isolation becomes more challenging Selfmixing and even order distortion may affect both channels and affect each other, causing additional I/Q mismatch

0 90 a(t) A/D Base Band DSP Phase and gain mismatch compensation DC and 1/f cancellation

Summary of Direct Conversion Receiver No need for imager reject filter Suitable for monolithic integration with baseband DC offsets due to crosstalk of input ports of mixer Even order IM direct feed through to baseband Quadrature down conversion suppresses mirror I/Q mismatch due to mismatches in parasitics Low power consumption attributes to less hardware

Low IF receiver - Quadrature RF down conversion required - Require higher performance ADC -Additional mixer -Slower RF PLL settling -Even order distortion still problem -Low freq IF filters require large chip area + Eliminate IF SAW, IF PLL and image filtering + Integration + Relaxes image rejection requirements + Avoids DC problems, relaxes 1/f noise problem

Low-IF Down Conversion Complex BPF Mirror signal, needs removal

Mirror Signal Suppression (1) Complex Bandpass Filter I Q I Q LO1 LO2

Mirror Signal Suppression (2) I Q I Q LO1 LO2 Both schemes used in heterodyne receivers for image rejection Mathematical analysis very similar

Image rejection architectures Use additional hardware (LO’s, mixers, and filters) Use I/Q channels which process + or – frequencies differently Two steps of I/Q to solve both image and mirror problems Effects limited by I/Q channel/filter matching accuracies

Image Reject Receiver Hartley Architecture -90° 0 90 RF input IF output A B C  LO

Hartley Architecture xcos xsin

IQ error effect Ideal IQ: image completely rejected If signal and image not single tone, 90 o shift is not exact Local oscillator’s sine and cosine not matched in magnitude and phase 90 o phase shifter may have both gain and phase error All lead to incomplete image rejection

IPR Evaluation and IRR – LO error

Input image power ratio

Image Reject Receiver Hartley Architecture with simple 90 deg phase shiftor

Gain Mismatch due to R, C errors At w = 1/RC:

Weaver Architecture

Digital IF? To avoid 0-IF or low-IF issues, IF frequencies can’t be too low Recall: RF-IF ratio within 10 Typical RF freq is in 1 to 5 GHz,  IF needs to be more than 100 to 500 MHz But dynamic range requirements requires >= 14 bit resolution No such ADC’s are available But signal bandwidth much smaller,  Subsampling Receivers

Example: 1.8 GHz GSM Specifications: IF carrier frequency = 246 MHz, Channel BW = 200 KHz, Input Dynamic Range = 90 dB. 2 digital low frequency mixers, no noise and distortion. Easier I&Q matching. No DC offset and 1/f noise. More digital means easier integration on a CMOS process. xSNR degradation due to noise folding xADC & SH have to run at high clock to minimize noise folding.

Noise folding problem IF White noise 0 … …… … fs 2fs IF 0 … …… … Baseband noise increased by IF/fs factor

The aliased noise, once happened, cannot be removed in the digital domain Band pass filtering of IF before sampling can reduce the noise in lower frequency –Requires expensive IF filters –Against the spirit of moving more things to digital Reduce IF frequency and increase fs frequency so that IF/fs ratio is not large –More stringent requirement on RF filtering and image rejection –Requires faster ADC

Example UMTS/DCS1800 Specifications Frequency Band Channel BW System Sensitivity BER Blocking Characteristics Adjacent Channel Interference DCS MHz 200 kHz -102 dBm 1e kHz: -43 dBm kHz: -43 dBm kHz: -33 dBm > 3000 kHz: -26 dBm Cochannel: -9 dBc 200 kHz: 9 dBc 400 kHz: 41 dBc 600 kHz: 49 dBc UMTS MHz 5 MHz e MHz: -56 dBm MHz: -44 dBm MHz: -30 dBm > 85 MHz: -15 dBm 5 MHz: -52 dBm

Sensitivity Adjacent Channel Interference Co-Channel Interference Desired Channel Adjacent Channel MHz

Multi-Channel, Multi-Mode Dynamic Range, DCS1800

PB = 13 dBm, Px = -60 dBm PB:Px = 73 dB If want FS:1LSB > 73 dB  >12 bit resolution If want digital channel selection + filtering,  fs >= 2BW  fs >= 150MHz If want noise floor 20 dB below wanted signal  SFDR >= 13 – (-60) + 20 = 93 dB Type of ADC needed: 150 MSPS, bit, dB SFDR

Sensitivity Receiver Thermal Noise Receiver Added Noise Desired Signal

Sensitivity ERP = +50 dBm Power to Antenna: +40 dBm TX. Antenna Gain: +10 dB Frequency: 10 GHz Bandwidth: 100MHz Rcvr. Antenna Gain: +60 dB Transmitter: ERP Path Losses Rcvr. Ant. Gain Power to Receiver Receiver: Noise 290K Noise in 100 MHz BW Receiver N.F. Receiver Sensitivity Margin: 4 dB + 50 dBm -200 dB 60 dB -80 dBm dBm/Hz + 80 dB +10 dB -84 dBm How to increase Margin by 3dB ? Path Losses: 200 dB

Selectivity Ch 1 Ch 2 Ch n Ch 3 RF Filter freq f RF Ch 1 Ch 2 Ch n Ch 3 freq f IF IF Filter freq f LO

Selectivity RF Filter IF Filter IF filter rejection at the adjacent channel LO spurious in IF bandwidth Phase noise of LO Receiver Added Noise Receiver Thermal Noise

Noise Figure Calculation receiver Baseband RF input

17! E s /N o or E b /N o =?

IP3 Calculation

Image Rejection Calculation SNR min f IF IR required f RF f LO P desired P Image (all in dB ’ s)

Transmitter Architecture Direct Conversion Transmitter Two-step Conversion Transmitter Offset PLL Transmitter

Transmit Specifications Transmit spectrum mask

Receiver Specifications Adjacent channel alternate adjacent channel

Direct-conversion transmitter 0 90 I Q  LO Pros: less spurious synthesized Cons: more LO pulling

Direct-conversion transmitter with offset LO 0 90 I Q  LO 11 22 Pros: less LO pulling Cons: more spurious synthesized

Two-step transmitter 0 90 I Q cos  1 t cos  2 t 1212 Pros: less LO pulling superior IQ matching Cons: required high-Q bandpass filter

Offset PLL transmitter 0 90 I Q cos  1 t PD/LPF VCO 1/N

Weaver Architecture

Wideband IF Architecture