kequency Selection

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.

LO Frequency Accuracy and Stability

The analyzer source is phaselocked to its receiver through a reference loop. In the frequency offset mode, the mixer under test is inserted in this loop. lb ensure that the analyzer phaselocks correctly, it is important that you use an LO source that has frequency accuracy better than f 1 MHz and residual FM < 20 kHz RMS.

Up-Conversion and Down-Conversion Defhition

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men you choose between ~~~:;;,~~~~~~~ and ~~~:~~~~~-,i,~~,in.,,.,,., .;,/the frequency offset menus, the analyzer

.._........

determines which direction the internal source must sweep in order to achieve the requested IF frequency. For example, to measure the lower sideband of a mixer, where the RF signal is below the LO (RF < Lo), the internal source must sweep backwards. See the examples in

Figure 6-92.

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..

Example of an Upconverter with RF<LO

Figure 6-92.Examples of Up Converters and Down Converters

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 upconverter measurement is being performed.

‘Applisation and Operation Concepts 6-161

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HP 8753E manual Examples of Up Converters and Down Converters