Hi,
I am currently trying to build a frequency detector for UHF. Until now, my design was somthing like:
Antenna -> HF filter -> Amp -> rest of the system (detector)
But actually, I was wondering why not using the superheterodyn principle to downgrade the frequency, because I am having a hard time trying to find filters for these frequencies (I found SAW filters...). I am not afraid of aliasing, because the signal that will be transmitted is around 9600bauds (and I probably won't use the signal). So the new design would be:
Antenna -> (Amp) -> mixer -> IF Filter
Nothing new here, this is just the usual theory, but to me it has only advantages:
Am I right ? The rising question is what should I use to generate a signal at around 300MHz ? I found VCOs having very wild frequency range, but actually I am fearing not being very precise with this kind of device. Also I have a dumb question: the signals (from antenna and from oscillator) going in the mixer must have the same amplitude, right ? so is this something do I have to care about ? Finally, would it be a good choice to have a chip doing (mixer + oscillator) all in one ?
Thank you
c0
I am currently trying to build a frequency detector for UHF. Until now, my design was somthing like:
Antenna -> HF filter -> Amp -> rest of the system (detector)
But actually, I was wondering why not using the superheterodyn principle to downgrade the frequency, because I am having a hard time trying to find filters for these frequencies (I found SAW filters...). I am not afraid of aliasing, because the signal that will be transmitted is around 9600bauds (and I probably won't use the signal). So the new design would be:
Antenna -> (Amp) -> mixer -> IF Filter
Nothing new here, this is just the usual theory, but to me it has only advantages:
- filters are easy to build / find for the lower frequency.
- No aliasing in case I want to use the signal.
- I can use a basic oscilloscope to view the signal.
Am I right ? The rising question is what should I use to generate a signal at around 300MHz ? I found VCOs having very wild frequency range, but actually I am fearing not being very precise with this kind of device. Also I have a dumb question: the signals (from antenna and from oscillator) going in the mixer must have the same amplitude, right ? so is this something do I have to care about ? Finally, would it be a good choice to have a chip doing (mixer + oscillator) all in one ?
Thank you
c0
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