Frequency Shifters

[Chris MacDonald]

Grant Richter wrote:
> ...
> In both cases, the problem seems to be non-linearity in the multipliers
> causing second and third harmonic distortion, which appears as side band
> bleed thru and isn't nulled by simple phase cancellation

It seems possible that harmonics in the sine waves used for shifting
would cause this kind of distortion as well, true?  

The quadrature sinewave oscillator circuit I posted a while back has a
second harmonic around 40dB down from the fundamental (according to a
CoolEdit frequency analysis).  I would expect these harmonics to get
multiplied through and appear in the output of a shifter.

In the Bode BFO setup, it seems like any second harmonic content present
in the fixed oscillator signal would be multiplied by any second
harmonic content in the variable oscillator and appear at the output of
the BFO as a second harmonic of the output fundamental as well.  Is this
true?  Perhaps the low pass filter at the output of the fixed oscillator
reduces the generation of these harmonics to insignificant levels
though.

-Chris M.