Chapter 8 417
IF Section
Automatic IF Adjustment
3. Crystal Bandwidths
a. The cal oscillator sweep rate is measured against the 100 kHz
resolution bandwidth filter skirt. This result is used in
compensating the sweeps used for adjusting the crystal
bandwidths.
b. 10 kHz resolution bandwidth
1. Center frequency of LC tank that loads the crystal
2. Symmetry adjustment to cancel crystal case capacitance
3. Bandwidth
c. 3 kHz resolution bandwidth: center frequency of LC tank and
bandwidth of resolution bandwidth
d. 1 kHz resolution bandwidth: bandwidth
e. 300 Hz resolution bandwidth: bandwidth
f. Gain of all resolution bandwidth relative to the 300 kHz RES BW
4. Digital Bandwidths (1 Hz through 100 Hz; 10 Hz through 100 Hz if
Option 103)
a. VCXO (final LO) tuned to align digital bandwidths with crystal
bandwidth center frequency
b. Overall gain
c. Gain variation with input frequency
Requirements
For the Automatic IF Adjustment routine to work, the spectrum
analyzer must provide the following basic functions:
• Power supplies
• Control signals
• ADC
• 10 MHz Frequency Reference to the A4 log amp/cal oscillator
• A15 RF Assembly isolation from the RF signal during IF adjustment
A15 RF assembly isolation is a function of the REDIR signal in the A15
Flatness Compensation Control block.
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