Technical Manual

380-520 MHz Power Amplifier
Appendix A - UHF Circuit Descriptions
A-
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ATLAS 4500 Multimode Station Technical Manual July 2021
IC48 regulates +5 V supply down to +3.3 VDC.
A.3 380-520 MHz Power Amplifier
This section contains information on the following Power Amplifier components:
• Attenuator
• Driver Module
• Output Power Amp
• Power Coupler
• Power Detector
• Harmonic Filter
• PTT Power Control
• Auxiliary Circuits
A.3.1 General Description
The PA contains the following components
• Variable attenuator
• Driver module
• Main power amp
• Cooling system and heat sensor
• Coupler for DPD system.
• Power detector
• Low pass filter
• PTT switch
• Serial flash memory and regulator
A.3.2 Schematic Description
A.3.2.1 General
The RF from the Exciter passes via a coaxial cable to the input of the PA Module,
CN1 at ≥12 dBm enters attenuator IC1, this provides attenuation steps of 0.25 dB.
This is used by the main Controller PCB for power control via CN2 pins 3, 4, 5
lines. The control lines are protected from ESD and RF. The RF signal then enters a
Driver Module. From the Driver Module it then matched by a broadband network to
drive the low input impedance associated with the final transmit (FET) power
amplifier transistor. The transistor's low Drain impedance is then also matched back
to 50 ohms by two broadband PCB matching network covering a very wide