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Frequency Offset Menu
If
you
press
[=I
~~~~~~~~~~’
~~~~~~~~~,“‘~~~
,
the
andyzer
flows
phase-locked
operation with a frequency offset between the internal source and receiver. This feature is
used in swept RF mixer measurements and has an upper frequency limit equal to that of the
analyzer being used.
This feature allows you to set the RF source to a
tied
offset frequency above or below the
receiver (as required in a mixer test, using a swept RF/IF and fixed LO). Then you can input a
signal to a device over one frequency range and view its response over a different frequency
range. The maximum delay between the RF source and the R input is 0.3 microseconds. The
analyzer will show a signal that is a composite of the desired RF signal, image response, and
spurious signals,
You can use the frequency offset in any sweep type in network analyzer mode. The two
user-defined variables in this mode are receiver frequency and offset frequency
(LC).
The
analyzer automatically sets the source frequency equal to IF +
Lo
or IF
-
Lo.
Mixer measurements and frequency offset mode applications are explained in application note
8753-2, “RF Component Measurements Mixer Measurements using the HP 8753B Network
Analyzer,” HP part number 5956-4362. This application note was written for the HP
8753B
but
also applies to the HP 8753E. Also see product note
8753-2A,
HP part number 5952-2771.
Primary Applications
Frequency offset mode is useful for the following types of measurements on frequency-
translating device:
w
conversion loss
w
conversion compression
n
amplitude and phase tracking
T&pical
Test
Setup
Figure 6-60 shows a typical test setup using frequency offset mode. Instructions are provided
in Chapter 3, “Making Mixer Measurements.
n
The attenuators shown reduce mismatch
uncertainties. The low pass
filter
keeps unwanted mixing products out of the sampler.
6-120
ApplicationandOperationConcepts