principles of radio transmitters and receivers 2

8/22/2019 Principles of Radio Transmitters and Receivers 2

http://slidepdf.com/reader/full/principles-of-radio-transmitters-and-receivers-2 1/92

1

Principles of radio transmittersand receivers

Dr Ding JiaXinEngineer of Radio Monitoring Division

State Radio Monitoring Center

[email protected]+8610-68312933

Radio Monitoring and Spectrum Management Training

(China,23-31,May,2005)



2

Contents:

1. Introduction

2. Basic concepts

3. Radio transceiver architectures4. Amplifiers

5. Mixers

6. Oscillators7. Modulation and Demodulation



3

Position of oscillator:

BPFIF RF

HPA

Antenna

Amplifier

LO

Mixer

BPF: Band-Pass Filter HPA: High-Power Amplifier

LO : Local Oscillator

radio transmitter architecture

BPFRF IF

Amplifier

Antenna

LNA

LO

BPF

Mixer

BPF: Band-Pass Filter

LNA: Low-Noise Amplifier


radio receiver architecture



4

Function of oscillator:

Generate a periodic output

Provide stable and accuratefrequencies for mixer



5

Classification of oscillators:

Feedback oscillator

Negative resistance oscillator



6

Principle of feedback oscillator:

H(f)X(f)VX VY

VF

VIY(f)

• Overall transfer function

•Loop gain:

)(1

)(

)(

)(

f H

f H

f X

f Y

I

F

V

V T



7

Barkhausen’s criteria

The loop gain must be equal to unity

The total phase shift around the loopmust be equal to zero



8

Frequency selective network:

H(f)X(f) Y(f)

Frequency selective

network

• Resonator



9

Oscillator characteristics:

Accuracy

Stability



10

Definition of accuracy:

f x: actual frequency

f 0: nominal frequency

00

0

f

f

f

f f x

＝



11

Stability of oscillator:

The ability to remain at a fixedfrequency

Long-term

Short-term



12

Phase noise:

t f At v c 2cos)(

• Ideal output:

• Actual output:

• Phase noise:

t f t At f A

t t f t a At v

cnc

nc

2sin)(2cos

)](2cos()](1[)(

)(t n



13

Output spectrum of oscillator：

f f c f f c

Ideal oscillator Actual oscillator



14

Effect of phase noise (I):

On the transmitting path

f f 1 f 2

Transmitted signal Adjacent

channel



15

Effect of phase noise (II):

On the receiving path

f f LO

LO output Wanted

signal

Interferer

f Downconverted

signals



16

Single side-band phase noise:

Describe frequency stability infrequency domain

PSSB: noise power in unit bandwidth

Pc: carrier power

Unit: dBc/Hz

C

SSB

P

P f L log10)(

Describe frequency stability infrequency domain

PSSB: noise power in unit bandwidth

Pc: carrier power

Unit: dBc/Hz

C

SSB

P

P f L log10)(



17

Example:

f f c f

Carrier average power:-2dBm

Noise power: -70dBm

Bandwidth: 1 kHz

:1MHz f



18

Typical value of SSB phase noise:

=10KHz

typical value: -80~-110 dBc/Hz

f



19

Summary:

Function of oscillator

Classification of oscillator

Principle of feedback oscillator

Characteristics of oscillator

Phase noiseSSB phase noise



20

Contents:

1. Introduction

2. Basic concepts


5. Mixers




21

Modulation & Demodulation:

General considerations

Basic concepts & Classification

Analog modulation

Digital modulation



22




Analog modulation

Digital modulation



23

Where is modulator ?

BPFIF RF

HPA

Antenna

Amplifier

LO

Mixer


HPA: High-Power Amplifier





24

Where is demodulator ?

BPFRF IF

Amplifier

Antenna

LNA

LO

BPF

Mixer


LNA: Low-Noise Amplifier LO : Local Oscillator




25

What is modulation?

f 0 f RFf IF• Baseband signal

• Passband signal

• The process of converting a baseband

signal to a passband counterpart



26

Why convert ?

For antenna design easy

For frequency multiplex

For efficiently transmit



27

Modulation & Up-conversion (I):

Modulation

Baseband => IF

Linear or nonlinear conversion

Up-conversion

IF => RF Linear conversion



28

Modulation & Up-conversion (II):

May occur in the same circuit

Matching

Network＋

Power

amplifier

Baseband

I

Baseband

Q

t f c 2cos

t f c 2sin

antenna

Direct-conversion transmitter architecture



29

Demodulation (detection):

The inverse of modulation

The process of extracting the originalbaseband signal from the passbandcounterpart with minimum noise,

distortion, etc



30

Modulator & Demodulator:

A device that can perform modulation

A device that can perform demodulation

Modem



31

Where is modulator?

BPFIF RF

HPA

Antenna

Amplifier

LO

Mixer


HPA: High-Power Amplifier LO : Local Oscillator


modulator IF

Baseband

signal



32

Where is demodulator:

BPFRF IF

Amplifier

Antenna

LNA

LO

BPF

Mixer


LNA: Low-Noise Amplifier



demodulator IF Baseband

signal



33

Summary:

Definition of modulation & demodulation

The reasons for modulation

Modulation & up-conversion

Modem



34




Analog modulation

Digital modulation



35

Some basic concepts:

Baseband signal

Carrier

Sinusoidal wave

Pulse train

Modulated signal



36

Classification of baseband signal:

Analog basebandsignal

Digital basebandsignal

t

A

t

A



37

Classification of modulation (I):



38

Classification of modulation (II):



39

Classification of modulation (III):



40

Classification of modulation (IV):

Linear modulation

AM, ASK, …

Nonlinear modulation

FM, PM, FSK, …



41

Modulation characteristics:

The “quality” of the output of thedetector

Spectral efficiency



42

Summary:

Some basic concepts

Classification

Modulation characteristics



43




Analog modulation

Digital modulation



44

Train of thought:

Mathematics model

Waveform in time domain

Spectrum/ Signal constellations

Implementation of modulation

The method of demodulation



45

Basic parameters:

Carrier

Baseband signal

xBB(t)

)2cos()( t f At c c



46

Amplitude modulation (AM)

Double-sideband amplitude modulation(DSB-AM)

)2cos()()( t f t Axt x c BB AM DSB



47

AM in time domain:

t

tt



48

AM in frequency domain:

f 0 0 f c-f c f * 0 f c-f c f



49

Implementation of AM:

BPF

xBB(t)

)2cos( t f c

x AM(t)



50

Demodulation of AM signal:

LPFxBB(t)

)2cos( t f c

x AM(t)



51

Basic parameters:

Carrier

:total phase

:excess phase

:total frequency:excess frequency

)](2cos[)( t t f At c c

)(2 t t f c

)(t

dt d f c

/2

dt d /



52

Frequency modulation (FM):

The excess frequency is linearlyproportional to the baseband signal

t

BBc FM dt t xmt f At x ])(2cos[)(



53

FM in time domain:

XBB(t)

Carrier

FM signal



54

Implementation of FM:

VCO

xBB(t) xFM(t)

VCO: Voltage-ControlledOscillator



55

Demodulation of FM signal:

FMD

xBB(t)xFM(t)

FMD: Frequency Modulation

Discriminator



56

Summary:

DSB-AM

FM



57




Analog modulation Digital modulation



58

Why digital?

Advantages

Process easily

Reproduce easily

Encrypt easily

Disadvantages

Synchronization

Wide bandwidth



59

Binary & M-ary signaling

Binary data

4-Level data

t

0 1

01

10

00

11

01

10

0 1



60

Basis functions:

A digital modulated waveform can berepresented by a linear combination of

orthogonal basis functions

where

)()()()( 2211 t t t t x N N

S T

k m dt t t 0

0)()(



61

Signal constellations:

A

A

1

2 ),)(,(

)()()(

2121

2211

t t t X

A 1 0



62

Correlation detector:

S 0(t )

S 1(t )

S m-1(t )

r(t)

bT

0

bT

0

bT

0

T b

T b

T b

D

es

i

o

n

Baseband

signal



63

Binary detector:

S 1(t )

S 2 (t )

bT

0

bT

0

T b

T br(t) +

-

Baseband

signal

S 1(t )-S 2(t )

bT

0

T b

r(t) Basebandsignal

(a)

(b)



64

Coherent & Noncoherent detection:

Coherent

need phase synchronization

Noncoherent

Don’t need phase synchronization



65

Binary Amplitude Shift Keying

(BASK):

t f t AX t X c BB BASK 2cos)()(

XBB(t)

XBASK(t)

carrier

K



66

BASK in time domain:

XBB(t)

XBASK(t)

1 0 0 1

• ASK is rarely used in RF applications



67

Binary phase shift keying (BPSK):

where

)2cos()( t f At X c BPSK

or 0



68

BPSK in time domain:

XBB(t)

XBPSK(t)

1

00

1

0



69

BPSK constellation:

A 1 0-A



70

Implementation of BPSK:

XBB(t)

XBPSK(t)

carrier

K

Phase

shift

0



71

Coherent BPSK detector:

bT

0

T b

XBPSK(t) Basebandsignal

t f A c 2cos2



72

Binary frequency shift keying

(BFSK):

where

t f t f t X BFSK 2211 2cos2cos)(

]0[]0[][ 21 Aor A



73

BFSK in time domain:

XBB(t)

XBFSK(t)

1 0 0 1

f 1 f 2 f 2 f 1



74

BFSK constellation:

A

A

1

2



75

Implementation of BFSK:

XBB(t)

XBFSK(t)Kf 1

f 2



76

Coherent BFSK detector:

bT

0

bT

0

T b

T bXBFSK(t) +

-t f 12cos

t f 22cos



77

Quadrature PSK (QPSK):

t f Abt f Abt X cmcmQPSK 2sin2cos)( 1

Where(bm,bm+1): (+1,+1), (+1,-1),

(-1,+1), (-1,-1)



78

QFSK constellation:

A 1 0-A

2

A

-A



79

Implementation of QPSK:

S/PCoverter

t f c

2cos

t f c 2sin

Binary

baseband

dataXQPSK(t)



80

Demodulation of QPSK signal:

bT

0

bT

0

T b

T b

XQPSK(t)

t f c 2cos

t f c 2sin

P/S

Coverter

Baseband

signal



81

Summary of digital modulation:

Binary & M-ary signaling

Signal constellations

Correlation detector Coherent & Noncoherent detection

BASK/BPSK/BFSK

QPSK



82

Summary :



Analog modulation Digital modulation



83

Summary(1):

1. Introduction

2. Basic concepts


5. Mixers




84

Summary (2):

Radio transceivers’ functions

RF and Baseband

RF signal

RF section is bottleneck



85

Summary (3)：

The concepts of memoryless,

Time-invariance, linearity

Effects of nonlinearity

Harmonics

Gain compression

Desensitization and Blocking

Intermodulation



86

Summary (4):

Basic blockings of transceivers

antenna

filter

mixer

oscillator

amplifier

Modem

Band & Channel



87

Summary (5):

Superheterodyne receiver

Image frequency

Direct-conversion receiver

Direct-conversion transmitter

LO pulling Two-step transmitter



88

Summary (6):

High-Power Amplifiers (HPA)

Low-Noise Amplifiers (LNA)

Other special amplifiers VGA



89

Summary (7):

Frequency translation

The core of all mixers is a multiplicationof two signals in the time domain

Implementation of mixer

Passive / Active mixer



90

Summary (8):



Analog modulation

Digital modulation



91

Question and Answer



Thank you !

principles of radio transmitters and receivers 2

Documents