Measurement Considerations

To ensure successful mixer measurements, the following measurement challenges must be taken into consideration:

w Mixer Considerations

. . . .

q Muummmg Source and Load Mismatches

q Reducing the Effect of Spurious Responses

q Eliminating Unwanted Mixing and Leakage Signals n Analyzer Operation

q How RF and IF Are Defined

q Frequency Offset Mode Operation

q Differences Between Internal and External R channel Inputs q Rower Meter Calibration

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 not possible when the device you are characterizing is a mixer operating over multiple frequency ranges. 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 ‘lb avoid overdriving the receiver, you should give extra care to selecting the attenuator located at the mixer’s IF port. 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.

Reducing the Effect of Spurious Responses

By choosing test frequencies (frequency list mode), you can reduce the effect of spurious responses on measurements by avoiding frequencies that produce IF signal path distortion.

Eliminating Unwanted Mixing and Leakage Signals

By placing Wers between the mixer’s IF port and the receiver’s input port, you can eliminate unwanted mixing and leakage signals from entering the analyzer’s receiver. Filtering is required in both tied and broadband measurements Therefore, when configuring broad-band (swept) measurements, you may need to trade some measurement bandwidth for the ability to more selectively filter signals entering the analyzer receiver.

How RF and IF Are Defined

In standard mixer measurements, the input of the mixer is always connected to the analyzer’s RF source, and the output of the mixer always produces the IF frequencies that are received by the analyzer’s receiver.

However, the ports labeled RF and IF on most mixers are not consistently connected to the analyzer’s source and receiver ports, respectively. These mixer ports are switched, depending on whether a down converter or an up converter measurement is being performed.

It is important to keep in mind that in the setup diagrams of the frequency offset mode, the analyzer’s source and receiver ports are labeled according to the mixer port that they are connected to.

3-2 Making Mixer Measurements

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HP 8753E Measurement Considerations, Minimizing Source and Load Mismatches, Reducing the Effect of Spurious Responses