Table of Contents
Advertisement
amplifier bias/control lines. The amplifier bias lines have a one pole roll-off
at 10 kHz, followed by two more poles at about 1 MHz.
The five dB gain steps are provided by a switchable 5 dB attenuator. The
attenuator is located between stages 4 and 5.
The 6 dB sloped gain attenuator is also located between stages 4 and 5. The
attenuator provides 6 dB of attenuation from DC to 100 MHz, and decreases
to less than 0.5 dB of attenuation at 2.0 GHz.
The step gain amplifier selection is designed to provide minimum amplifier
noise figure and maximum dynamic range without gain compression. The
noise figure is typically 4.3 dB for a gain of +20 dB or greater and 5.0 dB
noise figure for a gain of +10 dB or +15 dB, which are the lowest gain
settings used in normal downconverter operation. The amplifier vs gain
settings are as follows.
Table 13-21
Step Gain Amplifier Selection
GAIN
–5dB
Attn
–10 dB
IN
–5 dB
OUT
–0 dB
IN
+5 dB
OUT
+10 dB
IN
+15 dB
OUT
+20 dB
IN
+25 dB
OUT
+30 dB
IN
+35 dB
OUT
+40 dB
IN
+45 dB
OUT
IF Output Amplifiers
The step gain amplifier selection output is split into two output paths. Each
path is amplified by a 12 dB gain, +16 dBm output, thin film amplifier. One
output amplifier drives the AM detector and IF output peak detector. The
other amplifier drives the IF Output Switching.
The RF output must be well isolated from the +15 volt power supply. The
amplifier bias networks are made from several L-C and R-C sections,
producing a pole at 100 kHz, and several poles at 800 kHz.
HP 70427A Intermediate Frequency (IF) Amplifier
Stage 5
Stage 2
Amp
Amp
OUT
OUT
OUT
OUT
IN
OUT
IN
OUT
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
HP 70427A/HP 70428A User's Guide 13-57
Block Diagram
Stage 1
Stage 3
Amp
Amp
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
IN
OUT
IN
OUT
IN
IN
IN
IN
IN
IN
IN
IN
Stage 4
Amp
OUT
0UT
OUT
0UT
OUT
0UT
OUT
0UT
OUT
0UT
IN
IN
Advertisement
Table of Contents
