[time-nuts] Microstepper

[Magnus Danielson]

Hi,

I realize that I lack a microstepper. Consider that I have a stable and
low-noise 5 or 10 MHz but I want to resynthesize to correct frequency
and do phase-steps, and doing so without too much loss of noise.

This has traditionally been done using a variation of techniques, but if
we would use some of the things that happened lately, pretty OK
performance should be possible to achieve without too much hardware.

OK, so after a discussion with Bob, here is one sketch for a
possibility, just to toss one proposal to crush into pieces and propose
improvements or better versions.

So, consider using a modern Silabs chip clocked from an oscillator,
producing a offset generator with I/Q and then do an I/Q mixdown to a
beat frequency, which is digitized by a pair of ADCs. A pair of DACs
produces I/Q which is used to mixed to produce the output signal using
the signals from the Silab. The ADCs/DACs can be either be fed to some
CPU platform or FPGA. With this platform one can choose to servo the
reference oscillator, or just modify the beat received. Maybe use a
Raspberry Pi as platform. Rotating the vector and steering the rate of
rotation should not be extremely hard to do. The input vector can be
added internally or used to steer the oscillator. Either way, the in
loop noise from the Silabs will be fairly well suppressed since it only
acts as a transfer oscillator.

So, suggestions, thoughts and improvements?

God Jul and Merry Christmas!

Cheers,
Magnus