AR 10052381, Руководство по эксплуатации и обслуживанию

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Rev A 27
3. THEORY OF OPERATION
3.1 INTRODUCTION
The Model 125W1000A RF amplifier consists of a 80–1000 MHz RF amplifier assembly. The RF amplifier
assembly consists of a Pre-Amplifier (Pre-Amp) and one (1) Dual W-Module used as the final amplifier stage.
The power supply section consists of an AC input filter with fuses and a switch, three switching power supplies,
and a regulator circuit.
The control system consists of a Control/Fault Board, an Interface Board and remote interfaces for IEEE-488,
RS-232, USB, and Ethernet.
3.2 RF AMPLIFIER OPERATION
3.2.1 A1 Variable Gain Amplifier (Schematics 10033907, 10031968,
10035521)
The A1 variable gain amplifier consists of 3 subassemblies: the A1 Pre-Amplifier PWB Assembly, the A2 High
Isolation Switch Assembly, and the A3 Two-Watt Amplifier Assembly.
3.2.1.1 A1 Pre-Amplifier PWB Assembly (Schematic 10033907)
The Pre-Amplifier PWB Assembly consists of a stage of gain (U1), a variable attenuator (U2), a resistive splitter
(R3, R5, R4), another stage of gain (U3) an RF power detector (U9) and control circuitry. The overall gain of
the pre-amplifier assembly is approximately 17 dB at minimum attenuation. The power detector (U9) is used
to sense the input RF power and it increases the attenuation of U2 if an input overdrive condition is detected.
3.2.1.2 A2 High Isolation Switch (Schematic 10031968)
The High Isolation switch is normally in the thru mode. The switch can reduce the amplifier gain by more than
40 dB when the pulse input (E4) is pulled low.
3.2.1.3 A3 Two-Watt Amplifier (Schematic 10035521)
The Two-Watt Amplifier has a gain of approximately 16 to 18 dB. The Two-Watt Amplifier increases the
overall variable gain amplifier to approximately 31 to 32 dB of gain. The output RF power is approximately
30 dBm at the 1 dB compression point.