Broadband Frequency Response; Directivity (Includes Source Match, Test Port Match, And Re Ection Tracking) - Agilent Technologies 8711C Service Manual

Broadband Frequency Response

his test checks the broadband frequency response of the B* input at a nominal
to the analyzer. he RF output of the analyzer is sent to the input of a power splitter. One
output of the splitter is sent to the RF input of the analyzer while a power sensor is connected
to the other output. he analyzer is stepped through a cycle of CW frequencies while the
analyzer's source power and the corrected power meter reading are noted. Once this has
been done, the two connections to the outputs of the power splitter are swapped, and the
process is repeated. his eliminates any di erences within the power splitter. he two readings
for each frequency point are averaged and the averaged analyzer data is compared to the
averaged power meter data. Both sets of data are subtracted from a 30 MHz reference point.
Variations in response are then relative to this point. For 75 analyzers the power splitter and
sensor must also have a 75 input impedance. Adapters are generally required for this test. If
necessary, three-way power splitters can be substituted for two-way power splitters, as long as
the unused port is terminated in its characteristic impedance. Power dividers or splitters can be
used interchangeably with minimal measurement degradation.
If This Test Fails
Repeat the test after verifying that all connections are secure. here is no corresponding
adjustment for this test. Verify that the A5 receiver assembly's detector diodes are functioning
properly. See \ roubleshooting the A5 Receiver Assembly" in the \ roubleshooting and Block
Diagrams" chapter for more information.
Directivity (includes source match, test port match, and re ection tracking)
hese tests require an HP 85032B calibration kit (standard or Option 001) for a 50 analyzer or
an HP 85036B calibration kit for a 75 analyzer.
Note
he standard economy (E) versions of these kits do
components to perform this procedure.
Directivity is measured by presetting the analyzer, then attaching a known-good load to the
RF output and performing a re ection measurement. his measures the default re ection
calibration of the analyzer. his value is characteristically 30 dB. A user calibration will
provide 40 dB of directivity, but for this test, we are testing only the quality of the default
calibration. he typical speci cation is 30 dB. he program prompts you through all portions of
the test and displays the results on the screen of the analyzer.
Source match is measured at the same time as directivity. his test can be performed manually
with the following steps:
1. o disable correction, press
Meas Cal Options Meas Cal on OFF
2. Perform a one-port re ection calibration.
3. o view the source match array, press
(Raw directivity can also be viewed by selecting
the default directivity above; raw directivity will be much lower.)
Input port match is measured by performing a one-port calibration at the end of a type-N cable
using the female standards contained in the cal kit. For this reason, the economy version of the
cal kits cannot be used since they do not contain female standards. Once the user calibration is
completed, the cable is attached to the RF input port and the input match is measured. Please
note that when the female open is called for during this user calibration, the extender pin must
be placed over the center conductor of the cable.
1-24 Performance T ests
ervice
SYSTEM OPTIONS
5
.
View Array Master
not
provide the necessary
ervice Utilities
ource Match
. Do not confuse this with
Directivity
0
6 dBm input
.