Re: Taylor detector

[Steve Hubbard]

Hi,

It's not clear to me why you would want to do this. As far as I can see, 
the purpose of a Tayloe detector is to mix a real-valued RF signal with 
a complex-valued local oscillator to arrive at an intermediate frequency 
at or near zero frequency that can be sampled using a sound card. If 
you're using GR the implication is that the signal has already been 
sampled.

An ideal hardware IQ mixer would be a pair of analogue multipliers with 
sine local oscillators. However, this is not practical if good linearity 
is required (linearity is desirable to avoid intermodulation distortion 
and other nasty things). This is why switches are used. The switches 
used to be diodes, and still are at higher frequencies, but at HF CMOS 
analogue switches work better. With a switch based mixer you are 
effectively multiplying by a square wave, which comes with the 
disadvantage that odd harmonics of the square local oscillator also 
convert signals and noise into the IF. This necessitates a filter in 
front of the mixer to suppress these spurious responses. When IQ mixing 
is required there are the added challenges of phase and amplitude 
balance. Sometimes things ain't pretty in the analogue world.

As has already been pointed out, in GR a complex multiplier is the usual 
way to go. An accurate multiplier can be fed with near perfect 
numerically generated sine waves with perfect amplitude and phase 
balance. Besides, even if you wanted to simulate a square wave local 
oscillator in DSP you'd have to approximate by only including the 
harmonics up to the Nyquist frequency.

On 13/8/22 03:08, david vanhorn wrote:
> Ive been wrestling with this for a while, and im not even seeing how 
> to get started implementing a Taylor detector in gr.
>
> Is it even possible?