Measurement Considerations; Minimizing Source And Load Mismatches - Agilent Technologies 8719ES User Manual

Making Mixer Measurements (Option 089 Only)

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 2-6
• Analyzer Operation
"How RF and IF Are Defined" on page 2-7
"Frequency Offset Mode Operation" on page 2-9
"LO Frequency Accuracy and Stability" on page 2-10
"Differences Between Internal and External R Channel Inputs" 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.
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