Anritsu MG3702xA Series Maintenance Manual Download

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2-2 Major Subsystems

Chapter 2 — Functional Description

2-4

PN: 10370-10372 Rev. B

MG3702xA MM

Front Panel Assembly

This circuit subsystem shown in

Figure 2-2 on page 2-12

consists of the front panel, the front panel rotary data

knob, the front panel control PCB, and the liquid crystal display (LCD). The subsystem interfaces the front
panel LCD, light emitting diodes (LEDs), and keys to the CPU via the dedicated data and address bus. The
front panel rotary data knob is also linked to the CPU via the data and address bus.
The front panel PCB contains the keyboard matrix conductive rubber switches. It has circuits to control the
LCD, turn the front panel LEDs on and off, and convert keyboard switch matrix signals to parallel key code. It
also contains the standby/operate line switch and the optical encoder for the rotary data knob.

Frequency Synthesis

The frequency synthesis subsystem shown in

Figure 2-3 on page 2-13

consists of the A7 Reference/Coarse Loop

and A9 Oscillator PCB’s. The RF Output of the MG3702xA synthesizer originates from a 2.5 GHz to 4 GHz
voltage controlled oscillator (VCO) within the A9 PCB. By multiplying and dividing this signal, any frequency
between 2 GHz and 20 GHz is obtained. The VCO located on the A9 PCB is controlled directly and indirectly by
4 phase-locked loops:

•

100 MHz Reference Loop

•

Steering Loop

•

Coarse Loop

•

Fine Loop

The A9 PCB also houses the steering loop, the fine loop, and the frequency multiplication section.
The A7 PCB contains:

•

100MHz oscillator

•

Coarse loop

•

100MHz reference loop

•

10 MHz reference

Refer to

Section 2-3

for a functional overview of the frequency synthesis subsystem.

ALC/Pulse Modulator

This ALC circuit subsystem shown in

Figure 2-4 on page 2-14

consists of the A6 ALC PCB and the A4

Auxiliary Control PCB. It provides the following:

•

Level control of the RF output power.

•

Current drive signals to the PIN switches located in the switched filter assembly (SWF).

•

Drive signals for the step attenuator (Option 2).

•

Pulse modulation control (option 26)

Refer to

Section 2-4

for a functional overview of the ALC subsystem.

RF Level Control Assembly (A6 ALC PCB)

This assembly controls the automatic level control (ALC) for the MG3702xA Synthesizer. The A6 selects
appropriate frequency paths via PIN diode based switches and is the control block in the feedback loop
that provides the user with desired output power levels. It contains the internal and external pulse
modulation control (Option 26) and PIN switch drivers for the switched filter. The drivers for the
optional step attenuator and diplexer are also included.
Other components providing level controls within the ALC loop are the switched filter, the optional
digital down converter, and the leveling coupler.
The A6 ALC PCB connects to the CPU module via the 32-bit data bus. The A6 on-board FPGA provides
all programmed control signals and sends status information back to the CPU module.