
Radio-frequenci; circuits 207
conducting heavily: the diodes (which are selected
for close matching, or are monolithic) are in fact
used simply as switches. The ring DBM is double
balanced, produces the sum and difference fre-
quencies, and exhibits about half as many spurious
responses as an unbalanced mixer. The conversion
loss (ratio of IF output power to RF input power) is
about 7 dB; this is attributable to several different
causes. Half of the input RF energy will contribute
to the sum output and half to the difference: as
only one of these is required there is an inherent
3 dB conversion loss, the other 3 or 4 dB being due
to resistiv ...