HP (Hewlett-Packard) HP 85660B ユーザーズマニュアル

functions to mix the output of A10A4 (160.15 to 166 MHz) with the LO output from

(200 to 300 MHz). T he output of this assembly is the difference frequency suitably

filtered and amplified to about -10

The LO amplifier consists of common-emitter amplifiers

and Q2. CR1 and CR2 provide

limiting to prevent overdriving

near 200 MHz where

has more gain.

The double-balanced mixer

operates with about

LO drive and with -30

RF signal input. The IF output is about -36

and covers 30 MHz to 140 MHz. The

185 MHz Low-Pass Filter attenuates the harmonics of the RF signal input. The 10

pad

reduces the RF signal input from -20

to -30

The IF input amplifier has an input filter to partially filter the RF and LO signals from the
mixer. The amplifier Q3 has emitter degeneration R17 to reduce distortion.

The 140 MHz Low-Pass Filter is a modified elliptic filter which must pass 140 MHz while
rejecting 160 to 166 MHz by at least 60

The three adjustable coils optimize the

by providing nulls at the frequencies shown on the schematic. This filter also rejects the LO

frequencies (200 to 300 MHz).

The IF output amplifier consists of two common-emitter stages and an output low-pass filter.
The two stages are coupled by Cl4 and L17 which provide high frequency peaking.