We now consider a more realistic two antenna system
(Fig. 5.2), which includes two frequency conversions:
e.g. one in the SIS mixer, and one to move the IF band to baseband
for numerical sampling and digital correlation. This again is a
simplification, but includes all the important effects. The PdB
system has in fact 4 frequency conversions (see below).
Let us first consider the effect on phase of a simple frequency conversion.
