SRK Electronics FMA501, Руководство пользователя

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SRK Electronics FMA501 manual
 2007 SRK Electronics Pty Ltd 19
6 CIRCUIT DESCRIPTION
6.1
Equipment Overview
The FMA501 consists of the following sub-assemblies:
•
Power Supply
•
Control board
• Amplifier palette
•
Output directional coupler
These assemblies are interconnected as per “FMA501 wiring diagram”.
Please refer to fig 6.1 for the physical location of each sub-assembly.
The power supply provides a nominal 50V DC for the RF transistors.
The control board contains all metering and protection functions.
The amplifier palette contains most RF functions.
The output directional coupler allows accurate metering of forward and reflected power.
6.2
Power Supply and Metering board
The power supply is an OEM unit, manufactured by Meanwell, p/n RFP-1500-48. Full
specifications can be found at
www.meanwell.com .
Apart from the mains input and DC output, the control connector is used to switch the unit off
and on and to reduce the output voltage whilst PSU cut is enabled.
Energising the diode between pins 1 and 2 of CN2 switches the PSU off. A variable
resistance between pins 3 and 4 allows the output voltage to be reduced.
6.3
Control Board
The control board is responsible for all measurement and protection functions. Refer to the
appropriate schematic.
The heart of the controller board is U1, a micro-controller unit. This performs the following
functions:
The analogue voltages representing the forward and reverse powers are digitised on pins 40
and 39. These values are then squared internally to allow the forward and reflected power to
be read on the front panel and via telemetry.
Due to the limited number of pins, all other analogue voltages to be read (input power,
amplifier currents, amplifier temperatures and DC supply voltage) are routed through an
external MUX (U6) into pin 38. Thus allowing these parameters to be measured.
Pin 36 provides a digital signal that is used to assert the PSU cut function. This is done by
energising RL1, via Q1. VR16 sets the actual voltage in the PSU cut state.