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Amplitude variation of chirp waveform(Using AD9910)

Question asked by llu102585@163.com on Nov 29, 2015
Latest reply on Nov 30, 2015 by KennyG

Dear all,

I have a question about the amplitude of DDS chirp waveform.

 

In my application I am using AD9910 DRG mode to generate chirp waveform with frequency from 100MHz to 390MHz, but the signal amplitude has obvious variation. The amplitude variation and some information  @described below:

1. The amplitude increasing with frequency increasing, and the inverse Sinc filter can not change the trend whether it enable or not.

2. Peak to peak value: Vpp≈500mV(f≈100MHz),  Vpp≈610mV(f≈390MHz);

3. I have attached a test waveform.

 

my question:

1. Generally the amplitude decreasing with frequency increasing(without using inverse SINC), is  my test waveform correct? If not corrent, what reason maybe cause the problem?

2. I expect the variation of amplitude as little as possible with frequency varied(constant is better), is it possible? If possible, what measure can be took?

Thanks!!

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