Base band Signal Format

-
Different formats posse the base band signal information in different ways. So you may ask what the information in base band signal is. The signal information and their tasks are as follows.
Chrominance information: The chrominance portion of the base band signal is the collection of the colour/ hue information. This portion of base band signal says what will be the ratio of red-green-blue colour at certain position of television screen.
Luminance information: The luminance portion of the base band signal commands the brightness information of certain position of television screen.
Audio: The audio portion of the base band signal is actually the audio information of corresponding video signal.
Sync pulse: This portion of the baseband signal posses various types of synchronizing pulses for different purpose. Such as for audio-video synchronization, synchronization for scanning sequence (for horizontal and vertical scanning in television receiver), frame/field synchronization etc.

Colour coding information: There are three colour coding technology in the world. They are NTSC (National Television System Committee), PAL(Phase Alternation Line) & SECAM (Sequential Colour with Memory).
Aspect ratio information: For a particular frame of the television picture aspect ratio is width divided by the height of that frame. This may be 4:3 or 16:9 depending on the technology.
Different formats (such as SD, HD, composite) actually posse the above information of base band signals in different ways. These ways provides some special features that ensure the quality of base band signal

Comments

Post a Comment

Popular posts from this blog

Symbol rate, Bandwidth and Bit rate Calculation

-
In satellite communication bandwidth (BW), symbol rate and bit rate are the most vital fact for proper signal transmission. There are many commercial software for BW, Symbol rate and bit rate calculation for TV signal transmission. But the equations of these parameter calculation are as follows. BW= (1+Roll of factor)* Symbol rate In general Roll of factor is 35% Symbol Rate =BW / (1+Roll of factor) and Bit Rate = Symbol rate * Modulation* FEC* (188/204)                                     [when 188 is encoder packet length] or Bit Rate = Symbol rate * Modulation* FEC* (204/188)                                     [when 204 is encoder packet length] Here, FEC = Forward Error Correction. In general FEC is in the range from 1/2 to 7/8. 188/204 = constant Unit ** BW= Hz, KHz, MHz, GHZ ** Symbol Rate= sps or baud, Ksps or Kbaud, Msps or Mbaud, Gsps or Gbaud ** Bit Rate= bps, Kbps, Mbps, Gbps Baud: U nit of signalling speed Baud rate: N umber of symbols transm
Read more

Terminology: EIRP, G/T, Input Back-Off, Output Back-Off

-
  EIRP:   Used to indicate the power transmitted from an antenna. EIRP=Power +Antenna Gain, Both EIRP and Power is expressed in dBW and Gain in dBi. G/T:   It is the figure of merit for an earth station and is expressed as dB/K (dB per K). G/T= Antenna Gain-10*Log (System Noise Temperature) The higher the better-G/T can be raised by using a higher gain antenna or a lower temperature LNA. The earth station G/T determines the received carrier to noise ration. Increasing station G/T will increase the C/N of the received carrier. Input Back-Off (IPBO):   The level of a signal at the input of an amplifier relative to that level at the input that would result in the maximum possible output level. For example, if an input level of -20dBm causes max output and the actual input level is -25dBm, the IPBO is 5dB. Both IPBO and OPBO are commonly used to determine the operating levels in a satellite transponder TWTA. Output Back-Off (OPBO)   The level of a signal at the output
Read more

Bit Error Rate (BER) and Roll Off Factor

-
Image
Roll Off  Factor W hen a digital signal is modulated the output would be a waveform with the shape of sin(x)/x. Now this has an infinite bandwidth. So in order to be able to transmit this signal over satellite we need to filter it to reduce the occupied bandwidth. This is done by applying a "raised cosine roll-off filter". This filter is present both at the modulator output stage and at the input of the demodulator (I believe one says these filters are then matched). The steepness and the resulting occupied bandwidth can be set by the parameter roll-off factor. In DVB-S2 it can be 0.20 (20%); 0.25 (25%) or 0.35 (35%) where the  Occupied bandwidth = symbol rate x (1 + roll-off factor). Figure: Occupied bandwidth, Roll off factor and symbol rate 
Read more

Followers