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LECTURE 5-6. receivers OF RADIO and TV broadcastING systems. GENERAL INFORMATION ABOUT RECEIVERS OF RADIO AND TV BROADCASTING SYSTEMS MAIN TYPES OF BROADCASTING RECEIVERS RECEIVER NOISE FACTOR AND SENSITIVITY (SENSEPTIBLITY) MAIN ELEMENTS OF RECEIVERS SOFTWARE DEFINED RADIO (SDR).

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lecture 5 6 receivers of radio and tv broadcasting systems
LECTURE 5-6. receivers OF RADIOand TV broadcastING systems
  • GENERAL INFORMATION ABOUT RECEIVERS OF RADIO AND TV BROADCASTING SYSTEMS
  • MAIN TYPES OF BROADCASTING RECEIVERS
  • RECEIVER NOISE FACTOR AND SENSITIVITY (SENSEPTIBLITY)
  • MAIN ELEMENTS OF RECEIVERS
  • SOFTWARE DEFINED RADIO (SDR)
slide2

1. GENERAL INFORMATION ABOUT RECEIVERS OF RADIO AND TV BROADCASTING SYSTEMS

RS

RS+interference

Оконечное устройство

Soundand(or)image transducer

TX

RX

Interference

The general block diagram of radio channel of thebroadcast and TV systems

A sound or image, is transformed in voltage or current, modulates a high-frequency carrier. As a result the output radio signal (RS) of TX can be amplitude, phase or frequency modulated

  • Interference. At propagation radio signal in free space and feed lines it take place distortions, which are conditioned:
  • by irregularity of propagation medium;
  • by the artificial and natural restriction ;
  • byinternalnoisesofantennaandreceiveranditsimperfection
  • Radio receiver(RX) intended for transformation input signals with the purpose of extraction of useful information.
  • RX must contain units, necessary for realization of the followings operations:
  • selection from all of aggregate of electric vibrations, pointed in aerial the external electromagnetic fields, signal from a necessary radio transmitter;
  • amplfication of high-frequency signals;
  • demodulation signals;
  • strengthening of prorectifying signal.
slide3

The radioreceivers is designed to extraction of useful signals received from the receiving antenna, its amplification and conversion to the form required for the normal operation of terminals (loudspeaker, monitor, etc.)

By apointment: radio broadcasting, TV broadcasting, wireless communication, navigation, radiolocation, radio control, etc.

By type of signal:analog or digital

By the method of signal processing:

- with filter processing;- with correlation-filter processing.

By frequency band:LF, MF, SF, VHF, UHF, SHF, et cetera

The main functions of radio receivers: the selectivity (separation of the useful signal); amplification (to the level required for normal working terminal); conversion (to increase selectivity and stable amplification); automatic gain control (for widening dynamic rang) ; demodulation (selection of modulation law) or measure the signal parameters.

slide4

Sensitivity - the minimum power or voltage at the input RX, which provide a given quality of signal processing

Peak (noise-limited) sensitivity - the minimum power Psmin or voltage Uc minat the receiver input at which the SNR at the output of the linear part RX equal to one (Ps / Pn = 1 or Uc / Un = 1); Real (actual or threshold) sensitivity - minimum power or voltage at the receiver input at which the predetermined reception quality (given the SNR at the output of the linear part RX).       At wavelength > 1 m, when the resonans circuits RX can be considered as systems with lumped parameters, the sensitivity is taken in units of voltage - microvolts or millivoltsUc min. If  <1 m - in terms of power Pc min. Real sensitivity radio receiver is in the range of 50 ... 300 μV, depending on the quality class. Sensitivity of satellite TV receiver can be up 10-14 ... 10-15 W.

For broadcast receivers with ferrite antenna uses the concept of sensitivity in field strength. It has a value from 0.3 to 5 mV/m.

slide5

U c

f

p

УВЧ

УНЧ

СМ

U

гр

f

p

f

= f

г

р

Гетеродин

Block diagram of the receiver of direct amplification

. The block diagram of a superheterodyne receiver

2. MAIN TYPES OF BROADCASTING RECEIVERS

Frequency Converter

Block diagram of direct conversion receivers

SDR RX

slide6

Parameters of the radio receivers

Frequency range - the entire band of frequencies, which can receive signals

Dynamic range RX describes its ability to receive signals without distortion

Pвых

D,дБ=10 lg(Pinmax/Pinmin)

Selectivity: by the frequency (on the next channel, the image channel) by the waveform, by the polarization

у

slide7

Quantitative estimation of noises

Thermal (heat) noise

Stored energy

Nyquist formula

Shot noise

Power rating (nominal power)

Shottky formula

– noise power at matched load

slide8

3. RECEIVER NOISE FACTOR (figure, ratio)

INPUT.

UNIT

LNA

MIX

IFA

Detector

G

IfКрIN ≈1

slide10

RECEIVERS SENCITIVITY

Noise power output

Power output noise, converted to the input

Rs=RaRL=Rin

Nyquist formula

k=1,38·10-23W/Hz grad

slide11

4. MAIN ELEMENTS OF RECEIVERS

Low-nose amplifier

Balanced frequency converter

slide12

С

>>

С

bl

F

D

U

U LFout

intm

R

R

F

L

С

F

HF

Demodulators (detectors)

— AM

— FM

— PM

Amplitude detectors

LF

slide13

Demodulation of ASK signal

а

б

в

Demodulation of PM signal

slide14

Phase detector

Ud1= U0 + Us /2; Ud2= U0 - Us /2.

m << 1

Us/U0 = m

m = 1

Synchronous detector

Output voltage phase detector for in-phase input and reference signals φ =0

is proportional to the input signal Us, and the phase detector is converted in the synchronous detector. These detectors, due to their high linearity, are widely used in analog TV for demodulation of the image signals and in digital TV for demodulating PSK signals.

slide16

compression

expansion

slide17

BHF

BIF

AGC

BD

BLF (BDP)

LNA

MIX

PreIFA

Matched filter –Main IFA

АD

LFA

f IF= |f1 – fs |

_

X

Main IFA

PD

ADC

DSP

f2

PD

ADC

f1

o

DAC

FS

90

Block diagram of the analog – digital receiver

slide18

ADC have not affected on RX noise factor

If only

For ADC 1107ПВ2

L=8

L FT , MHz D, dB

For ADC AD9260 L=16

slide19

The twentieth century saw the explosion of hardware defined radio (HDR) as a means of communicating all forms of audible; visual, and machine-generated information over vast distances.

Most radios are hardware defined with little or no software control; they are fixed in function for mostly consumer items for broadcast reception. They have a short life and are designed to be discarded and replaced.

Software defined radio (SDR) uses programmable digital devices to perform the signal processing necessary to transmit and receive baseband information at radio frequency. Devices such as digital signal processors (DSPs) and field programmable gate arrays (FPGAs) use software to provide them with the required signal processing functionality. This technology offers greater flexibility and potentially longer product life, since the radio can be upgraded very cost effectively with software.

slide20

Software Defined Radio (SDR)

SDRequipment - these are elements of the wireless network which operating modes and parameters can be changed or expanded after the elements are made using the software.

slide21

Modulated signal

can to present by sum of two quadrature component

slide22

Zero IF Quadrature Product Detector

One cycle Sine Wave at Sampled Frequency Fo