HP 70908A, Service Manual

Page: 226 / 335

T est 09. Image Rejection
The purpose of this verication test is to measure the image responses of the rst and last
IFs in the W bands and the second and last IFs in 1H0 band. (Image responses are a pair of
frequencies separated by twice the IF frequency of the analyzer .)
This is a nal test.
Note
If this test fails in 1H0 band, repeat using a dierent HP 8340A synthesized
sweeper . (Some HP 8340A synthesized sweepers may have output spurious
levels that mix with the LO to produce a 0642.8 MHz response in the 1st IF .)
1. Connect the equipment as shown in the test setup illustration for this procedure .
2. Set the mainframe line switch to ON.
3. Load and run T est 09. Image Rejection. Refer to Chapter 2 for information about running
the software .
When performing this verication test, the full microwave source connects to the DUT RF
INPUT , and then steps through the image frequencies . At each step frequency the local
oscillator source tunes to center the signal. The calibrated spectrum analyzer measures the
amplitude of the 21.4 MHz OUT signal. The local oscillator source frequency is then oset by
0642.8 MHz to cause the input signal from the full microwave source to appear as an image
response of the DUT 321.4 MHz IF . The calibrated spectrum analyzer measures the amplitude of
this image response . Subtracting image response from the measured real response results in a
relative measurement, which a routine compares with test limits .
The test repeats in the 1H0, 1L0, 2L0, and 4L0 bands , and at the 1H0band last IF image
response (local oscillator source oset 042.8 MHz).
Module V erication T ests 8-21