Agilent Technologies 856290216 service manual Sampler and Sampler if

Sampler and Sampler IF

The A15UlOO sampler creates and mixes harmonics of the sampling oscillator with the first LO. The resulting sampler IF (60 MHz to 96 MHz) is used to phase-lock the YTO. The sampler IF filters unwanted products from the output of A15UlOO and amplifies the IF to a level sufficient to drive the YTO loop. When the IF is between 78 and 87 MHz, PIN diodes switch a 120 MHz notch filter in the sampler IF section.

1. Set the spectrum analyzer to the following settings:

Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .300 MHz Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz

2.Disconnect W32 from A15JlOl.

3.Connect the input of a power splitter to A15JlOl. Connect W32 to one of the splitter outputs. Connect the other splitter output to the input of another spectrum analyzer.

4.If a 66.7 MHz signal, greater than -15 dBm, is not displayed on the other spectrum analyzer, set a microwave source to the following settings:

Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2107GHz Amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5 dBm

5.Connect the microwave source to A15UlOOJl. A 66.7 MHz signal at approximately 0 dBm should be displayed on the other spectrum analyzer.

6.Use an active probe/spectrum analyzer combination to measure the signal at the following test points:

A15TPlOl	66.7 MHz, -8 dBm
A15TP201	296 MHz, +9 dBm

7.If a correct signal is seen at A15TP201 but the signal at A15TPlOl is wrong, proceed as follows:

Use an oscilloscope to measure the signals at the following test points:

A15J400 pin 1+0.8 Vdc to +1.6 Vdc (SO.5 Vp-p variation)

A15J400 pin 3-0.8 Vdc to -1.6 Vdc (SO.5 Vp-p variation)

If these levels are wrong, perform the “Power and Sampler Match Adjustments” in the sampler oscillator adjustment procedure. Refer to Chapter 2, “Adjustment Procedures.” If adjusting the sampler match does not bring the signal at A15TPlOl within specification when the signal at A15TP201 is correct, the A15UlOO sampler is defective.

8.The sampler IF signal at A15JlOl is 60 MHz to 96 MHz at -10 dBm to +5 dBm. If the signal at A15TPlOl is correct, but the signal at A15JlOl is wrong, the fault lies in the sampler IF circuitry. Continue with the following steps.

9.Set the HP 85633 to the following settings:

Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..300MHz Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OHz

Synthesizer Section 11-45