A11 Phase Lock Board - Agilent Technologies PNA Series Service Manual

Theory of Operation
Source Group Operation
The 20 MHz reference is sent through a divide-by-5 circuit to produce the 4 MHz signal
sent to the A35 receiver motherboard to produce the 1 MHz 2nd LO signal for band 0.
The 100 MHz reference signal is sent through either a:
• divide-by-12 circuit to produce the 8.3333 MHz phase lock reference signal for bands
1-26, or a
• divide-by-96 circuit to produce the 1.0416 MHz phase lock reference signal for band 0.
One of these is selected to be sent to the A11 phase lock board.
Rear-Panel Interconnects
10 MHz REF. INPUT
10 MHz REF. OUTPUT

A11 Phase Lock Board

The A11 phase lock board compares the phase lock IF signal from the A35 receiver
motherboard with the phase lock reference signal from the A10 frequency reference board
to generate the tuning voltage for the A12 source 20 YIG-tuned oscillator (YTO). In
addition, various digital-to-analog converters (DACs) on this assembly are set by the A6
SPAM board to inject offset and delay voltages for the various source bands and
measurement sweep rates.
A12 Source 20
The A12 source 20 consists of:
• Source 10
• Multiplier/Amplifier 20 (MA 20)
• ALC Circuitry
Source 10
The A12 source 20 contains a 3−10 GHz YIG-tuned oscillator (YTO) and a fixed frequency
3.8 GHz permanent-magnet YIG oscillator (PMYO).
The YTO has a main coil and an FM coil. These are analogous to the woofer and the
tweeter in a stereo speaker: the woofer reproduces low frequencies and the tweeter
reproduces high frequencies. Similarly in the YTO, the main coil allows large, slow
changes in frequency but cannot respond to high frequency deviations, which are sent to
the faster-acting FM coil.
5-10
A BNC connector that allows an external frequency reference
signal to be used to phase lock the analyzer for increased
frequency accuracy.
The analyzer automatically enables the external frequency
reference feature when a signal is connected to this input. When
the signal is removed, the analyzer automatically switches back to
its internal frequency reference.
A BNC connector that allows a 10 MHz reference signal, produced
by the A10 frequency reference board, to be output for use in
phase locking external test equipment.
PNA Series Microwave Network Analyzers
Service Guide E8361-90001
E8361A