Lief, There is an interesting mathematical treatment of these matters (sinewave at least) in:
"Balanced Mixer Noise Considerations", John Shigemoto, The Microwave Journal, October 1967. Henry. Leif Asbrink wrote: > Hi Henry, > > >> Why is it only schottky mixers that have the problem - won't any high >> level passive mixer have the same problem? >> > Yes, I would think so, but I have not tried any other passive mixer > than the standard schottky mixers that are so populer for home- > brewing these days. Surely unbalanced mixers sould be much worse... > > I would also think the problem is the same for MOS switching mixers > of various kinds. Maybe the AM sideband noise can be removed by > the conversion of the LO from sinewave to squarewave but I am not > so sure that would help because AM modulation would probably cause > a varying mark to space ratio instead. By carefully designing the > stage that converts from sine to square one should be able to avoid it, > (make a test by putting 5% AM modulation on the LO and see whether > the tone comes out of the mixer when there is no RF signal.) > > Any mixer including switching mixers is an FM detector to some degree. > Apply FM modulation at e.g. 1 kHz modulation frequency to the LO without > any signal to the RF port. Increase the frequency swing until there > is noticeable 1 kHz audio in the mixer output. > > 73 > > Leif / SM5BSZ > > > > ------------------------------------ > > Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
