Subharmonic Mixers, aside from requiring an LO at half the normal frequency, can achieve ultra-high (-55 to -60 dB) rejection of the LO leakage out of the RF port relative to the input power. This means an input isolator can often be eliminated, but more important, for linear upconverter or modulation requirements, the carrier rejection can be maintained at high levels.
Some customers employ pairs of I/Q even harmonic up- and downconverter mixers for lower cost data links. The principle disadvantage of the even harmonic mixer are slightly higher (2 dB) conversion loss, more LO power sensitivity, and doubling of the LO phase noise. | |
