[sdiy] [synth-diy] Frequency shifter which rejects negative frequencies

[Gordon JC Pearce]

On Sun, Jan 26, 2014 at 04:55:29PM +0100, cheater00 . wrote:
> Hi guys,
> 
> In a parallel thread, I have explained what lock-in amplifiers are and
> how they work.
> I have asked myself: what if rejecting negative and positive
> frequencies, leaving only frequencies near DC, you could reject only
> negative frequencies?
> 
> I'm not sure, but I believe in the digital world you can do the
> four-quadrant multiplication and then take a Fourier transform of
> that. But I'm very hazy on the details. Can anyone confirm or deny?
> 
> Is there an analog process that allows you to do this?

Yes, that would be a single-sideband receiver.

-- 
Gordonjcp MM0YEQ