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Signal Generator

JohnDSiviter

I want to build a bench signal generator one day, 0-100MHz, sine, triangular, square, variable M/S ratio etc and want a single chip solution (except for maybe a few optoisolators/buffers), I was thinking about using a fast ARM processor and fast DAC/s, it would also need USB so I can use the PC to program waveforms, what processor would you choose and why?

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  • Use pretty much any processor you like - the cost will be dominated by the FPGA, clock generator/DDS, DAC, reconstruction filter etc.

    You can go out and buy signal generators like this and there is a reason they cost £2000 or more.

     

    To get 100MHz sine wave at reasonable noise and distortion you will need at least 3e8 samples per second, even fast processors can't do IO at that rate so you'll need the FPGA to work the DAC.

     

    Use a processor with the necessary features from the family you are most familiar with.

  • in reply to michaelkellett

    Oooh let me throw a spanner in the works.

    Who says you have to use FPGAs and DACs?

    Good quality signal generators have been around a lot longer than FPGAs and fast DACs.

     

    Here's my suggestion... think outside the box. Do you think there is anyway to generate, say, a 100Mhz sine wave with just a few low cost components? How about square wave? How about triangular?..... (Hint: analogue).

     

    Now, given your circuit which generates the signal, how would you modify the frequency? How about the amplitude?

     

    I bet you could do all that without a processor or DAC in sight....

     

    Now, how could you build that/those circuit(s) and have the frequency and amplitude modified by a micro under software control? (Hint: digital pots).

     

    Am I talking nonsense? Or do you think mixed-signal might be the way to go here?

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  • in reply to michaelkellett

    Oooh let me throw a spanner in the works.

    Who says you have to use FPGAs and DACs?

    Good quality signal generators have been around a lot longer than FPGAs and fast DACs.

     

    Here's my suggestion... think outside the box. Do you think there is anyway to generate, say, a 100Mhz sine wave with just a few low cost components? How about square wave? How about triangular?..... (Hint: analogue).

     

    Now, given your circuit which generates the signal, how would you modify the frequency? How about the amplitude?

     

    I bet you could do all that without a processor or DAC in sight....

     

    Now, how could you build that/those circuit(s) and have the frequency and amplitude modified by a micro under software control? (Hint: digital pots).

     

    Am I talking nonsense? Or do you think mixed-signal might be the way to go here?

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