Signal Loss While Working With A Mixer; Rf Output - Keysight Technologies N5171B EXG User Manual

Signal Loss While Working with a Mixer

To avoid damaging or degrading the performance of the signal generator,
do not exceed 33 dBm (2W)
input. See also
www.keysight.com
To fix signal loss at the signal generator's RF output during low–amplitude coupled operation with
a mixer, add attenuation and increase the RF output amplitude.
The figure at right shows a
configuration in which the signal
generator provides a low
amplitude signal to a mixer.
The internally leveled signal
generator RF output (and ALC
level) is
–8 dBm. The mixer is driven with
an LO of +10 dBm and has an LO–
to–RF isolation of 15 dB. The
resulting
–5 dBm LO feedthrough enters the
signal generator's RF output
connector and arrives at the internal detector.
Depending on frequency, it is possible for most of this LO feedthrough energy to enter the detector.
Because the detector responds to its total input power regardless of frequency, this excess energy
causes the ALC to reduce the RF output. In this example, the reverse power across the detector is
actually greater than the ALC level, which can result in loss of signal at the RF output.
Keysight EXG and MXG X-Series Signal Generators User's Guide
maximum
Tips for Preventing Signal Generator Damage
.
Effects of Reverse Power on
Signal Generator
Output Control
ALC
Level =
−8 dBm
RF
Level
Detector
Detector
measures
measures
−5 dBm
−8 dBm
reverse
ALC level
power
of reverse power levels at the RF
on
RF
Output
= −8
LO
Feedthru
= −5 dBm
Troubleshooting

RF Output

Mixer
LO
LO Level
= +10 dBm
IF
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