>akachyan wrote:
>
> ...
>
>> I use DFT filters to track frequency. FFT doesn't work in my case
because
>> I need precise frequency tracking.
>
>FFT is an efficient way to do DFT. If different ways to do DFT give
>different results, at least one of them is wrong.

I use single-bin DFT filter. FFT may be used. But for narrow bin,
calculation can be brutal. :-)

>
>> Furthermore, the off signal may have different frquency, i.e on freq
is
>> 15.65 Mhz and off freq is 16.59 Mhz. In this case, I have to track
15.65
>> Mhz freq. of course it has on/off switches.
>
>If the off freq is 16.59 MHz, what does "off" really mean? Do you have a

>form of FSK?

It is interesting problem.

For example, there is a switch. When it is ON, signal has 15.65MHz, when
OFF, 16.59MHz. Presumely, system doesn't know the frequency beforehand.
Now the system has to track the frequency,15.65Mhz when switch is ON. But
switch is frequenctly on and off. So, I collected the signal when switch is
on.
The collected signal has same frequency, but a lot of phase discontinuity.
It makes me hard to track the frequency. It is the problem.


>
> ...
>
>Jerry
>--
>Engineering is the art of making what you want from things you can get.
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