A4 Receiver Board - Agilent Technologies E4991A Service Manual

Theory of Operation
Analog Section
Table 5-2 VCO and measurement frequencies for each band
Band1
Band2
Band3
Band4
The filtered signal goes through an attenuator variable from 0 dB to 35 dB in 5 dB steps,
and is output to RF Out port. Attenuation is controlled depending on the output power
setting as shown in Table 5-3.
Table 5-3 Output Attenuator
Nominal Setting of
Output Power Level
7.9 dBm ~ +1 dBm
12.9 dBm ~ 8 dBm
17.9 dBm ~ 13 dBm
22.9 dBm ~ 18 dBm
27.9 dBm ~ 23 dBm
32.9 dBm ~ 28 dBm
37.9 dBm ~ 33 dBm
40 dBm ~ 38 dBm
The A3 VCO signal is also mixed with RF1 signal which is supplied to A4 receiver board.

A4 Receiver Board

A4 receiver board receives the Vch and Ich signals from the A6 test head through PORT1
and PORT2, mixes down them into 12.5 KHz IF signals, and converts the analog signals to
digital data. The receiver has two signal flow to measure Vch and Ich signals.
The input attenuators on A4 board are controlled to optimize the receiver input signal
levels(the signal to noise ratios) for accurate measurements. These attenuators are set
depending on the output power setting as shown in Table 5-4.
228
Measurement Frequency
1 MHz  1739.9 MHz
1740 MHz  2259.9 MHz
2260 MHz  2679.9 MHz
2680 MHz  3000 MHz
Output Attenuator
on A3
0 dB
5 dB
10 dB
15 dB
20 dB
25 dB
30 dB
35 dB
VCO Frequency
2305 MHz  4043.9 MHz
2892 MHz  3411.9 MHz
3412 MHz  3831.9 MHz
3832 MHz  4152 MHz
Chapter 5