HP 8753E manual Conversion Loss, Isolation, LOFeedthru/LOtoRFLedage

Conversion Loss

fl F= fRF-fLO iL0 ’ RF fl F= fRF+ fLO

FREQUENCY

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Figure 6-95.

Example Spectrum of RF, LO, and IF Signals Present in a Conversion Loss Measurement

Conversion loss is a measure of how efliciently a mixer converts energy from one frequency to another. It is the ratio of the sideband output power to input signal power and is usually expressed in dB.

Since the frequency response of the test system gets measured with the mixer’s response, you can perform a frequency response calibration to remove this group of errors.

Isolation

F e e d t h r o u g h

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Figure 6-96. Main Isolation ‘lkrms

Isolation is the amount of attenuation provided when a signal is applied to one port of a mixer and measured at another port. Figure 6-96 shows the three main isolation terms.

LOFeedthru/LOtoRFLedage

LO feedthru, or LO-to-IF isolation, is the amount the Lo signal that is attenuated when it reaches the IF port.

LO to RF isolation is the amount the LO power is attenuated when it appears directly at the RF port.

Roth of these LO isolation terms are small for single and double balanced mixers. The RF signal level applied to the mixer will have an affect on this measurement. For this reason, these terms are usually measured with the RF port of the mixer terminated in a matched state.

6-l 64 Application and Operation Concepts