When antenna received signal,antenna generate voltage,then SDR convert voltage to I=amplitude*cos(t)and I=amplitude*sin(t).

When antenna receive 10k and 100k signal individually,how does voltage changed accordingly?


1 Answer 1


This question would be a better fit for the electronics stackexchange. I'll try to take a systems approach and ignore polarization, etc. You can think of the antenna as a resonant system; in other words, as a bandpass filter. The filter's center frequency, cutoff frequencies, and other characteristics depend on the antenna itself, its size and and its shape.

So, short answer: the antenna response to different frequencies depends on its physical properties.

  • $\begingroup$ Does it means antenna+SDR CANNOT recognize different frequency? $\endgroup$
    – kittygirl
    Mar 15, 2022 at 17:03
  • $\begingroup$ No, it does not mean that at all. It means that the ability of the antenna to pick up energy at each frequency is (possibly) different. So, signals at the antenna with the same energy but different frequencies will not necessarily produce the same voltages at the input of the ADC (even ignoring the frequency response of the front-end). In other words, the antenna acts like a bandpass filter. $\endgroup$
    – MBaz
    Mar 15, 2022 at 17:59

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