Digital Signal Processing, New technology, Telecomunications, Wireless

How digital TV works?

In this post I will talk about digital TV. How it works and the advantages over digital TV. I will give an introduction to analog TV before talk about the digital one.

Analog TV

The analog TV works on the following way: A video camera take 30 pictures per second, each picture is divided in pixels and each pixel have information about the color and brightness of the picture. These informations are codified and transmitted. Arriving in the TV’s antenna, the signal pass by a demodulator filter to separate the audio and videos signals. The video’s signal has the pixel’s informations which go to the circuits: synchrony separator and signal video amplifier. Here is a television’s video signal seen be the oscilloscope showing the horizontal and vertical sync pulses.

The TV uses a technique called signal synchronization signal, consist in synchronize the deflection electronic circuits horizontal and vertical to show the image in the screen. Here is the TV receiver’s flowchart. Modern televisions don’t use flyback transformer.

Here shows how the image were formed in a analog TV’s screen.

How the digital TV works?

In a digital TV, the pixels have information about color, brightness and position screen in binary code. In the converter the analog signal from the antenna is sampled, quantized and divided in digital signals of video, audio and data. After is send to video and audio channels. The external converter is called Set-Top box.

This converter has the PAL-M encoder and output to connect to analog television. Also has the HDMI output to modern LED and LCD TVs without converter. The Middleware has the function to receive the user’s command and control the RF tuner (to change the channel), the decoder (language, censor, subtitles, etc), modem and display. This is the block diagram of the converter embedded in the TV.

To receive the digital signal, it is necessary have a converter, which can be integrated in the TV.

An UHF (Ultra High Frequency) antenna.

And a television which can have 1080p resolution.

Advantages over analog TV

  • The digital TV has a much higher resolution than the analog. While the analog TV has a average resolution of 480p (horizontal lines), the digital has 1080p.
  • No noise and interference;
  • Better sound quality due to the digitalization;
  • Bigger band width means interactivity to obtain informations about the programming.



About Pedro Ney Stroski

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