Hi Bob!
I'm not a native english speaker, thats why I maybe not understand what you
ment?!
>From what I know is:
- you need (normally) double sampling rate from that frequency that you want
to sample (Nyquist, 60 MHz sampling rate for 30 mhz frequency)
- in addition to the above said for a I/Q mixer you need two VCO frequencys
of the same frequency with a 90 degree shift.
(this is sometimes created by taking a frequency 4 times high than the rx
frequency and put it into a johnson counter to get, but there are sure
different ways of doing this, 2 DDS outputs with the shift , ... )
- you can do a trick in order if you haven't got a that high going frequency
clock that fits the nyquist frequency: take a single balanced mixer which
doen't attenuate lower harmonics that much and use the rx for that
frequencies. the problem is that in this case you are loosing some
information from the real signal because you are sampling only every second
time of the sine wave.
Stephan
