Shift Phase of 100 kHz Signal 90 Degrees

[jim hardy]

Very first post said

For a school project I need to be able to shift the phase of a 100 kHz sine wave by 90 degrees (either positive or negative).

Has this been mentioned ? i wonder if a "bucket brigade" analog delay line device might be a useful mix of analog and digital technology for that task. Clock could be pll to a multiple of the incoming sinewave thereby avoiding frequency dependence of analog RC filters.

http://www.datasheetarchive.com/dl/Scans-091/DSAHI00040423.pdf

 

[Baluncore]

Then in post #7, the final application was specified.

Does you application demand the accuracy & stability of a crystal oscillator?

On that note, what is your application that it needs quadrature signals?

The end product will use a QAM signal to send two audio channels, and the device will need to be very small and low-powered so an LC oscillator would be too bulky. Other oscillators based on ceramic resonators could work, but the principal would be the same as a crystal oscillator I think, which is proving to be very difficult to design.

We do not know the exact wording of the original project specification.

 

[mheslep]

This has been a fun and interesting thread, but I have to confess that I haven't read all the posts in detail, so apologies if this solution has already been covered.

The way I've done this in the past is to use 2 ROMs with sine wave data in them that is offset by 90 degrees (for I and Q demod, but the technique works for encode as well). They are clocked together, and their outputs are driving R-2R ladder DACs with filter buffers. This gives you 2 very nice sine waves that are 90 degrees out of phase.

You can then use those waveforms for your 4QAM modulation circuit.

Works great with I and Q always separated 90deg even in unit number one million. The quantization noise is down 2^2b from the carrier power or, say, 48dB w 8 bits meaning, I think, that an analog osc is still required to realize very high SNR.