A11 Phase Lock Board - Agilent Technologies E8362A Service Manual

PNA Series Microwave Network Analyzers
E8362A, E8363A, E8364A
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 A16 test set
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.
The tune current from the A11 phase lock board splits into two paths. One path is low-pass
filtered, removing high frequency components, and goes to the YTO main coil; the other
path is highpass filtered, removing low frequency components, and goes to the YTO FM
coil. The filters are matched in stop-band response, such that one picks up where the other
leaves off.
The frequency of the PMYO is set by a voltage received from a DAC set by the A6 SPAM
board.
Service Guide E8364-90001
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.
Theory of Operation
Source Group Operation
5- 9