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The resolution of sin wave

Medya

 Hi

I do fft(using dft with N=1024 and set the input freq=100M*17/1024 ,strobperiode=10ns and simulation time>10240ns) on the output of the sin wave,and see that the noise floor is about -100db i repeat it for variuos step(strobperiode) and simtime but the noise floor doesn't vary more,I'm so confused that how can test the high resulotion adc with this low resolution wave,is the way to solve this problem

thanks

Parents
  • Andrew Beckett

    If I simulate this simple netlist:

    //
    v1 (sinout 0) vsource type=sine freq=100M*17/1024 ampl=1
    r1 (sinout 0) resistor r=1M

    tran tran stop=10240n strobeperiod=10n

    Then I get the attached picture (which as you can see has very low numerical noise floor). If you're simulating a more complicated circuit, it may be the simulator accuracy that is limiting you - have you set errpreset on the tran analysis? Have you set reltol? Without knowing quite what you're doing, it's hard to be sure.

    Andrew.

Reply
  • Andrew Beckett

    If I simulate this simple netlist:

    //
    v1 (sinout 0) vsource type=sine freq=100M*17/1024 ampl=1
    r1 (sinout 0) resistor r=1M

    tran tran stop=10240n strobeperiod=10n

    Then I get the attached picture (which as you can see has very low numerical noise floor). If you're simulating a more complicated circuit, it may be the simulator accuracy that is limiting you - have you set errpreset on the tran analysis? Have you set reltol? Without knowing quite what you're doing, it's hard to be sure.

    Andrew.

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