Agilent Technologies 8590 Series Service Manual page 361

RF and LO Section for 8590L, 8591E, and 8591C Spectrum Analyzers
5. Changes the amplitude of the 21.4 MHz IF signal to calibrate the
analyzer during the
• The amplitude of the detected 21.4 MHz IF signal is measured on
the A16 processor/video assembly.
• The A7 analog interface assembly adjusts the gain of the IF
calibration amplifier based on the A16 amplitude measurement.
• The
CAL AMPTD
IF calibration amplifier for a displayed amplitude of −20 dBm at
300 MHz. The analyzer is set for a reference level of −20 dBm and
a center frequency of 300 MHz. (The calibration routine uses the
CAL OUT signal.)
10 MHz Frequency Reference
Note that this section applies to all 8591C, 8591E, and 8590L
analyzers.
The 10 MHz frequency reference is used to phase-lock the 600 MHz
oscillator on the A9 third converter. There are two frequency references
available:
• The standard 10 MHz room temperature crystal oscillator (RTXO).
• The precision frequency reference (PFR), A22, is a 10 MHz
oven-controlled crystal oscillator (OCXO).
A25 Counterlock
The A25 counterlock assembly performs four main functions:
• Phase-locks the 600 MHz SAW oscillator on the A9 third converter to
the 10 MHz reference.
• Counts the first LO frequency.
• Provides discriminator output, DISCRIM, to the A7 analog interface
assembly.
• Counts the 21.4 MHz IF.
Refer to Figure 9-5, at the end of this chapter for details about the
operation of the A25 counterlock assembly.
On the A9 third converter, the output of the 600 MHz oscillator is
divided by two and the resulting 300 MHz signal is routed to the A25
counterlock assembly. The A25 counterlock assembly divides the
300 MHz signal by 40 to generate a 7.5 MHz reference for the sampling
oscillator, stabilizer, and frequency counter. The 7.5 MHz reference and
the 10 MHz reference are divided further and compared in a
phase-frequency detector. The output of the phase-frequency detector,
VTO_TUNE, is fed back to A9 to tune the 600 MHz oscillator.
Chapter 9
Assembly Descriptions and Block Diagrams
self-calibration routine.
CAL AMPTD
adjustment routine adjusts the output of the A9
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