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What is Block Diagram of TV Communication?

by Sonali

The block diagram of a TV communication system consists of a TV transmitter and a receiver. In this section we will understand the working of block diagram of TV communication completely.

The below figure shows the TV broadcast  transmitter. 

  • There are two sections of the transmitter unit.
  • One unit is responsible for generation of video signals. This unit receives pictures and based on them it generates the video signals.
  • This video signal then helps to modulate the Radio frequency signal. The antenna further transmits this signal. 
  • The other unit generates an audio signal which contains information in the form of sound. This signal then modulates another RF signal.
  • We use only one antenna for both transmission and reception of signals.
  • Now there mixing of these two video and audio signals.
  • We require an amplifier to amplify these audio and video signals before they could modulate their respective RF carriers.
  • The audio and video amplifiers help in amplification.
  • We use an AM transmitter for Amplitude Modulation of video signals.
  • Whereas we use FM modulators for frequency modulation of sound information.
  • The scanning of electron beam from the actual picture through a scanning circuit which produces corresponding video signals.
  • At the receiving end also the same process is used. 
  • Hence, we need synchronizing circuits at both transmitting as well as receiving ends,

TV transmitter

TV Transmitter
  • The transmission section of the broadcast unit is has two main sections.
  • One which modulates the amplitude (video) and another which modulates frequency (audio).
  • For generating RF signal frequency we use Master oscillator. This master oscillator generates sub multiple carriers.
  • These carriers then drive frequency multipliers for obtaining the correct value of carriers. 
  • The Class C tuned amplifiers are harmonic generators. 
  • A buffer exists between the master oscillator and harmonic generator.
  • The carrier of the video transmitter is fed to AM and also to FM in the audio transmitter.
  • As the amplification is of low level, linear amplifiers amplify these modulating signals. 
  • The video and audio signals are separately produced. They are combined and then fed to the transmitting antenna.

TV Receiver

  • The receiver end produces back the images from the amplified signals received at the receiving antenna.
  • The receiver circuit amplifies and converts video and audio RF signals into visual images with their audios.
  • The images generated can be colored or black and white. 
  • To fulfil this purpose the superheterodyne receivers which simultaneously amplifies and converts audio and video RF signals.
  • The tuner picks up the required signal and then converts it to a lower frequency.
  • This frequency is in between the intermediate frequency pass band.
  • An amplitude detector, video amplifier and intermediate frequency amplifier forms a signal processing unit.
  • There is a color processing circuit for chrominance signals.
  • The control electrodes of the kinescope receive a brightness signal and color difference signals.
  • The extraction and decoding of chrominance signals is in color processing circuits.
  • The horizontal and vertical scanning circuits form a scanning generator unit.
  • For exciting purposes, an electron gun kinescope interface has static and dynamic white balance controls. They also regulate the focusing beam.
  • There are different amplifiers for amplifying frequency in the audio section.
  • The power supply section will convert the main supply voltage into the supply voltage for the TV set.

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