[sdiy] Weaver frequency shifter
brianw at audiobanshee.com
Thu Apr 28 02:41:15 CEST 2022
Do these tuner stages at the beginning and end of the Weaver signal chain end up shifting the frequency band of the content? Would this help keep all signals within the sample rate? Are these questions moot because of the potentials of under sampling?
On Apr 27, 2022, at 08:43, Eric Brombaugh wrote:
> I've done a fair bit of work in this area, both in synths and in communications for the day job. It's interesting to note that most quadrature tuning approaches are mathematically equivalent - the main differences being that you're just re-arranging the order of operations. Weavers method isn't doing anything fundamentally different from the Hilbert or phase-shift but it does put a tuner at the beginning of the process which has to be removed at the end.
> The advantage of doing this by the Hilbert approach is that a lot of the operations become constants you can roll into the Hilbert filter coefficients. The result is collapsing the number of DSP operations required and thus reducing the CPU load over what you'd need to do with Weavers.
> On 4/27/22 03:00, rburnett at richieburnett.co.uk wrote:
>> Has anyone tried building a Frequency shifter using Weaver's method? Either analogue or digital.
>> I'm asking out of interest, rather than any immediate intention to build anything.
>> All of the synth related designs I've seen seem to be based around the phasing method, using either an analogue dome filter or digital Hilbert transform to impart the 90 degree phase difference. I was looking at Weaver's or "the third method" of SSB generation relating to an SDR discussion at work the other day, and it looks like a good candidate for a modern DSP implementation.
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