HP 70908A, Service Manual

Page: 193 / 335

A djustment 22. 2nd Converter Bandpass Filter Tune
Figure 7-47. Locations for A djustment 22. 2nd Converter Bandpass Filter Tune
The purpose of this adjustment procedure is to align the RF section 2nd-converter 3621.4 MHz
bandpass-lter shape . (The user adjusts amplitude , atness , and 3 dB bandwidth.) The test also
measures 42.8 MHz image rejection.
1. Set the mainframe line switch to OFF .
2. Remove the HP 70908A RF section from the mainframe .
3. Install the extender module in the mainframe and connect the HP 70908A RF section to the
extender cable .
4. Connect the equipment as shown in Figure 7-45.
5. Set the mainframe line switch to ON and allow at least 30 minutes initial warmup before
starting the adjustment.
6. Load and run A djustment 22. 2nd Converter Bandpass Filter Tune . Refer to Chapter 2 for
information about running the software .
The synthesized signal generator provides 300 MHz , 0 dBm, at the DUT INPUT . The full
microwave source through an isolator provides 3921.4 MHz, 8 dBm, at the DUT LO input. The
network analyzer channel-A detector connects to the DUT 321.4 MHz OUT . The user views
the network analyzer response while adjusting the three 2nd converter bandpass-lter tuning
screws and also the matching inductor on the A8 321.4 MHz matching network . The adjusted
parameters are maximum amplitude , atness , 3 dB bandwidth, and 42.8 MHz image rejection.
The response must satisfy the following limits: amplitude , 035 to 2 dBm; atness , 0.5 to 0.2 dB
relative to amplitude at 3621.4 MHz, 15 MHz on either side of center (a slight adjustment of
the 2nd converter bandpass lter input coupling connector is acceptable to improve atness);
3 dB bandwidth, 25 to 30 MHz; image rejection, equal to or greater than 23 dB relative to the
3621.4 MHz center frequency .
7-54 Adjustment Procedures