EE194-EE290C28nmSoCforIoT

Ref:RFMicroelectronicsbyBehzadRazavi.SecondEdiFon

Terminology

f

In-Band Blocker Levels Out-of-Band Blocker Levels

Edge ofBand

DesiredChannel

-43 dBm

-70 dBm

-30 dBm

-23 dBm

0 dBm

RFFilteringFilteringrequirementsimpacttheRFdesignofthetransceiver.

BPF

TransmittedChannel

AdjacentChannel

BPF

PA

LNA

fDesiredChannel

AlternateChannel

AdjacentChannel

BPF

RFFiltering•  Receivechainprecedingchannel-selecFonfilteringmustbesufficientlylinear.•  ChannelselecFonfilteringisextremelydifficultattheRFfrequencies.

f

DesiredChannel

ReceiveBand

BPF

LNA

f

DesiredChannel

QBPF ≈foBW

=2450MHz/1MHz=2450

In-Bandinterferersaretypicallyremovedneartheendofthereceivechain.

RxArchitectureHeterodyneReceiver

RFInput

f

LO

IFOutput

Mixer

fRF ± fLO

ARF cos 2π fRFt +φRF( ) ALO cos 2π fLOt +φLO( )*

f

DesiredChannel

fRFfIF=RF-LO fRF+LO

ImageProblemHeterodyneReceivers

AIF cos 2π fIFt( ) = AIF cos 2π fRF − fLO( ) t{ }AIF cos 2π fIFt( ) = AIF cos 2π fLO − fRF( ) t{ }

f

DesiredChannel

fLOfRF fimage

fIF fIF

ffIF

ImageRejecFon

ffRF fimage

2fIF

Image Reject Filter

ImageRejecFon

ffRF fimage

2fIF

Image Reject Filter

ffIF

Channel Select Filter

ImageRejecFon

ffRFfimage

2fIF

Image Reject Filter

ffIF

Channel Select Filter

RxArchitectureHomodyneReceiver

BPF

LNA LPF

LPF

I

Q

cosωLOt

sinωLOt

Symmetricvs.AsymmetricSpectra

f0

ffLO

ffLO

xBB(t)

t

VCO

ffLO

Symmetricvs.AsymmetricSpectra

ffLO

f0OverlapofsignalsidebandsaWerdown-conversion

QuadratureDownconversion

LPF

LPF

I

Q

cosωLOt

sinωLOt

Twoversionsofthedownconvertedsignalthathaveaphasedifferenceof90o

CanreconstructtheoriginalinformaFon.

RxArchitectureDirect-conversionreceiver(Homodyne)

BPF

LNA LPF

LPF

I

Q

cosωLOt

sinωLOt•  DCoffset•  LOLeakage•  1/fnoise

LOLeakage

LNAPad

LOSubstrate

LNAPad

LO

DCOffsets

LNAPad

LO

VRF+kVLO

VIF+VDC

LNA

LO

A1

Vb

R1

C1

f0

BasebandSignal

HPF

DCOffsets

LNA

LO

A1

Vb

R1

C1

ffRF ffRF

LowFreq.DeviaFon LargeFreq.DeviaFon

f1 =1

2πR1C1<

Rs1000

•  For802.11b@20Mb/s,f1=20KHz•  Slowresponsetotransientinputs.

-  LOfrequencyisswitchedtoanotherchannel,hencechangingtheLOleakage.-  ThegainoftheLNAisswitched,thuschangingthereverseisolaFonoftheLNA.

RxArchitectureLow-IFReceiver

ffRF f0 If

Less1/fnoisepenaltyOn-chiphigh-passfilteringbecomesfeasible.

RxArchitectureRejectImagewithoutfiltering.Quadraturedownconversionasa90ophaseshiWer.

cosωLOt

sinωLOt

I

Q

VRF

ffRF fLO fImage

ffRF

fLO

fImage

-j/2

HartleyArchitecture

cosωLOt

sinωLOt

I

QVRF

LPF

LPF

90o

IF

RxArchitecture

x(t) = Asig cos ωsigt +φsig( )+ Aimage cos ωimaget +φimage( )

xI (t) =Asig2cos ωsig −ωLO( ) t +φsig⎡⎣ ⎤⎦+

Aimage2

cos ωimage −ωLO( ) t +φimage⎡⎣ ⎤⎦

xQ (t) = −Asig2sin ωsig −ωLO( ) t +φsig⎡⎣ ⎤⎦−

Aimage2

sin ωimage −ωLO( ) t +φimage⎡⎣ ⎤⎦

x(t) =Aimage2

sin ωLO −ωimage( ) t −φimage⎡⎣ ⎤⎦

RxArchitecture

x(t) = −Aimage2

cos ωLO −ωimage( ) t −φimage⎡⎣ ⎤⎦

x90 (t) = −Aimage2

cos ωimage −ωLO( ) t +φimage⎡⎣ ⎤⎦

RxArchitecturecosωLOt

sinωLOt

I

QVRF

LPF

LPF

90o

IF

ADC

ADC