Measurement Considerations; Minimizing Source And Load Mismatches - Agilent Technologies 8753ET User Manual
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Making Mixer Measurements
Measurement Considerations
Measurement Considerations
In mixer transmission measurements, you have RF and LO inputs and an IF output. Also emanating from the
IF port are several other mixing products of the RF and LO signals. In mixer measurements, leakage signals
from one mixer port propagate and appear at the other two mixer ports. These unwanted mixing products or
leakage signals can cause distortion by mixing with a harmonic of the analyzer's first down-conversion
stage.
To ensure successful mixer measurements, the following measurement challenges must be taken into
consideration:
• Mixer Considerations
❏
"Minimizing Source and Load Mismatches"
❏
"Reducing the Effect of Spurious Responses" on page 2-5
❏
"Eliminating Unwanted Mixing and Leakage Signals" on page 2-5
• Analyzer Operation
❏
"How RF and IF Are Defined" on page 2-7
❏
"Frequency Offset Mode Operation" on page 2-10
❏
"LO Frequency Accuracy and Stability" on page 2-10
❏
❏
"Power Meter Calibration" on page 2-12
Minimizing Source and Load Mismatches
When characterizing linear devices, you can use vector accuracy enhancement to mathematically remove
all systematic errors, including source and load mismatches, from your measurement. This is difficult when
the device you are characterizing is a mixer where the input and output signals are at different frequencies.
Therefore, source and load mismatches are not corrected for and will add to overall measurement
uncertainty.
You should place attenuators at all of the test ports to reduce the measurement errors associated with the
interaction between mixer port matches and system port matches. To avoid overdriving the receiver, you
should give extra care to selecting the attenuator located at the mixer's IF port to avoid overdriving the
receiver. For best results, you should choose the attenuator value so that the power incident on the analyzer
R channel input is less than 10 dBm and greater than 35 dBm.
2-4
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