Technical data

12-30 Chapter 12
Theory of Operation
Receiver Theory
The Mixer Circuit
The 1st IF and the 2nd LO are combined in the mixer circuit. The resulting difference
frequency (the 2nd IF) is a constant 4 kHz in both bands, as shown in Table 12-4.
A10 Digital IF
The three 4 kHz 2nd IF signals from the sampler/mixer assemblies are input to the A10
digital IF assembly. These signals are sampled at a 16 kHz rate. A fourth input is the
analog bus, which can monitor either an external input at the rear panel AUX IN
connector, or one of 31 internal nodes. A multiplexer sequentially directs each of the
signals to the ADC (analog-to-digital converter). Here they are converted to digital form
and sent to the A9 CPU assembly for processing. Refer to “Digital Control Theory” on
page 12-9 for more information on signal processing.
Table 12-4 Mixer Frequencies
Band 1st IF 2nd LO 2nd IF
Super Low
a
a. Analyzers with Option 006 only.
0.010 to 0.300 MHz 0.014 to 0.304 MHz 4.0 kHz
Low 0.300 to 16.0 MHz 0.304 to 16.004 MHz 4.0 kHz
High 1.000 MHz 0.996 MHz 4.0 kHz