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  1. #1
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    Looking for a Noise Generator in Verilog

    Iím looking for a Noise Generator (Random Number Generator) in Verilog, VHDL or math functions in MATLAB/SIMULINK. Has anyone seen this?
    I would all so like to set the amplitude (2^12, 2^14 etc..).

    I just got the MATLAB/SIMULINK with the Altera DSP Builder. Seems pretty nice.
    Alan

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  2. #2
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    digital uniform distribution noise generator

    Do you need gaussian noise or uniform noise.

    Do you need white noise or other type of spectral density.

    Matlab has a basic random function with uniform distribution, which is rand().



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  3. #3
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    predictable noise generator

    I need Gaussian and uniform noise. I canít use a function because I need to put it in a FPGA so I need to make it out of basic math (+, -, * etc..). Iíve used the MATLAB noise generators and they work great.



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  4. #4
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    matlab noise generation

    Quote Originally Posted by alanj@signalcrafters.com
    I need Gaussian and uniform noise. I can’t use a function because I need to put it in a FPGA so I need to make it out of basic math (+, -, * etc..). I’ve used the MATLAB noise generators and they work great.
    You can use LFSR (Linear Feedback Shift Register) to produce noise in certain band. For LFSR app. notes visit Xilinx site and search for LFSR.

    See this link for LSFR AHDL/VHDL/Verilog Generator
    http://www.logiccell.com/~jean/LFSR/



  5. #5
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    vhdl random number with lsfr

    Thanks Black Jack for pointing me in the right direction. Noise Generator up and running.



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  6. #6
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    matlab noise generator

    Note that there are areas where this is usefull, and where it is not.

    It is not a random noise gererator, as the output is repetitive and predictable. So, it is not to be used where security is involved (crypto systems for example).

    However, it is very usefull a noise generator for audio applications. Also, it is used a lot in telecom, for 2 reasons.

    First, as a way to test the quality of a digital transmission line. A pattern using this generator is sent over the line, and at the other end, using the same noise generator configuration, you can verify that the data is correctly transported. This is used as a pseudo-random data generator, to 'simulate' randomness.

    It is also used to scramble transmitted signal. This is usefull because many transmission technologies, like SONET/SDH, need a constant number of '1' and '0' in the transmitted stream. If the data to be transmitted is all-zero (or all ones), this would de-sync the receiver. By scrambling the signal, you simply XOR the output bits with the pseudo-random pattern. This ensure a constant number of transitions in the signal. Note that this scrambling is not for obscurtion purpous (i.e. the goal is not to 'encrypt' the output stream), but rather just to make sure that a constant number of 1 and zero get transmitted, even if the input data is mostly zeros or ones.



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