
Enhanced Tuning Range Using a Calibrated DC FM
Source
Enhanced Tuning Range is a method to increase the PTR by using the
total available tuning range of the VCO. The VCO must have a calibrated
DC FM output accurate within to 5% of the indicated rate, and can except
input voltages exceeding the calibrated voltage range without damage.
The Enhanced Tuning Range can be used to decrease the systems noise
floor when using DC FM. By allowing a larger PTR with the minimum
VCO Tuning Constant (Peak Deviation) the system can phase lock a drifty
source without increasing the peak deviation. Enhanced Tuning Range
increases the PTR thereby increasing the Drift Tracking Range and Capture
Range without changing the VCO Tuning Constant (Peak Deviation) .
This feature allows you to measure a noisy or drifty source, that would
normally exceed the phase lock loops ability to maintain phase lock,
without increasing the VCO's Tuning sensitivity. The noise floor is limited
by sensitivity of the VCO Tune
1
Port, (refer to 12 HP 3048A Noise Floor
Limits Due to Peak Tuning Range in Chapter 7, Quick Reference, to see the
graphic relationship of noise floor to PTR).
NOTE
You cannot use this feature on a VCO that does not have
a known Tuning Constant (within ± 5%) or if the VCO
could be damaged by applying voltages (Typically ±10
volts) that exceed the Tune Port requirements.
instr. Params: $N w/PLL 2-27
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