I would like to understand the mean of sampling frequency and symbol rate in commsrc.patern command.

Dear Sir or Madam,

I have a question about commsrc.patern command.

I can't understand the maen of sampling frequency and symbolrate in commsrc.pattern command. Are there concept of sampling frequency and symbolrate in waveform generator?

So, please tell me the mean of this.

Sincerely,

Answer 1

[David Ding]

Hi Shunsuke,

I understand that you are looking to understand the meaning of "SamplingFrequency" and "SymbolRate" properties of the "commsrc.pattern" system object.

This system object holds information about a waveform specified by its properties, such that when you call the function "generate", such as:

x = generate(h, N);

Where "h" is the "commsrc.pattern" object and N is the number of symbols in the output, the waveform gets generated and stored into the variable "x" (where you can then plot "x", for example).

The object "h" can be defined for example as follows:

h = commsrc.pattern('SamplingFrequency', 10000, ...
                      'SamplesPerSymbol', 100, ...
                      'PulseType', 'NRZ', ...
                      'OutputLevels', [-1 1], ...
                      'RiseTime', 0, ...
                      'FallTime', 0, ...
                      'DataPattern', 'PRBS7', ...
                      'Jitter', commsrc.combinedjitter)

Now onto the properties "SamplingFrequency" and "Symbol Rate":

Consider the waveform vector "x": each data point of x is considered as a "sample". Thus, the sampling frequency determines how many of those points are generated each second. The "SamplesPerSymbol" property determines how many of those points, grouped together, is considered as a "symbol". Therefore, the "SymbolRate" property, which is read-only, determines the number of symbols in the pattern waveform generated each second. The relationship is as follows:

SymbolRate = SamplingFrequency / SamplesPerSymbol

For example, if I sample a signal at 100Hz (that is, for each second I create 100 points in the waveform vector "x"), and I consider 50 samples as a symbol, then my symbol rate is:

100 / 50 = 2 Symbols per second

Correspondingly, my symbol period, T_sim, is 1/SymbolRate = 0.5 seconds.

Full documentation of the "commsrc.pattern" system object is found below:

https://www.mathworks.com/help/releases/R2017b/comm/ref/commsrc.pattern.html

Thanks,

David