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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

    Come on Michael, thats a bit of a cop out image, I cant use pretty much any processor I like because of the 100Mhz problem, I reckon if you get a fast enough processor the actual system is not that difficult to program, high speed DACs might be however....

  • in reply to JohnDSiviter

    John - you haven't quite got my point - I don't know of ANY processor that can drive a DAC at 300MHz with reasonable jitter. A DAC that fast will probably have LVDS inputs  - an easy interface to an FPGA but not to any processors I know.  Since you will need an FPGA (or other custom logic) the processor doesn't have any demanding real time work to do - so it is not a performance driven decision (at least as far as the signal generation goes). This is the case in a great many real development projects.

     

    You haven't given anything like enough spec details to really drive the processor choice but if I were doing this (on the basis of the limited information) I would use an ARM Cortex, probably one of the STM32F parts, because I am familiar with them so the cost of development would be lower. If you are tooled up for a PIC32 or something else - that would probably do just as well.

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  • in reply to JohnDSiviter

    John - you haven't quite got my point - I don't know of ANY processor that can drive a DAC at 300MHz with reasonable jitter. A DAC that fast will probably have LVDS inputs  - an easy interface to an FPGA but not to any processors I know.  Since you will need an FPGA (or other custom logic) the processor doesn't have any demanding real time work to do - so it is not a performance driven decision (at least as far as the signal generation goes). This is the case in a great many real development projects.

     

    You haven't given anything like enough spec details to really drive the processor choice but if I were doing this (on the basis of the limited information) I would use an ARM Cortex, probably one of the STM32F parts, because I am familiar with them so the cost of development would be lower. If you are tooled up for a PIC32 or something else - that would probably do just as well.

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