5-10 Service Guide E8364-90038
Theory of Operation PNA Series Microwave Network Analyzers
Source Group Operation E8362C, E8363C, E8364C
Rear-Panel Interconnects
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 3ï€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.
10 MHz REF. INPUT 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.
10 MHz REF. OUTPUT 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.
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