QM1004-8-12-100 Combined RF Upconverter/Downconverter
User Manual
RF Up Stage mixer simply passes the 2x IF directly to the output. Because this signal is "in-band", there
is no amount of filtering that can get rid of this spur without changing the frequency plan, including the
IF1 filter and fixed LO2. The only way this spur may be reduced in the current design is by either lowering
the input IF signal power, by lowering the LO2 power (consult factory for details), or by adjusting the RF
tunable filter in the RF Up Stage (consult factory).
The second source of spurs in the upconversion is the direct LO1 leakage in the RF output. Due to the
fact that the LO1 power is typically much higher than the IF1 input, direct leakage of LO1 through the RF
Up Stage mixer is unavoidable. Fortunately, the LO1 leakage is out of band, and may be filtered with an
external lowpass or bandpass filter.
Harmonics of the RF upconversion output are also present. Fortunately, these also are out of band, and
may be filtered out.
Quonset Microwave
Revision 2.0.0
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