TRP1000-4450 Troposcatter C-Band Outdoor Amplifier
Revision 0
Introduction
1–5
MN-TRP1000-OD
1.4.2
SSPA Module
The amplifier module performs the core function of the unit. An isolator is at the RF input to
ensure good voltage standing wave ratio (VSWR). The RF signal then passes through the input
power monitor and on to an electronically controlled attenuator that adjusts the overall attenuation
according to the user input. This attenuator is automatically controlled via a look-up table to
maintain the amplifier gain at a constant level over temperature variations.
The RF signal is then amplified by a multi-stage design that utilizes proprietary low-load
combining techniques to meet the rated power requirements. The output circuitry contains a
coupler to provide a sampled signal for monitoring purposes. A forward power detector circuit
also is included and the reading can be accessed via remote communication. A high power
circulator and load is located at the output to provide good VSWR and protection from external
mismatch. A reverse power detector will shut down and protect the unit in case of excessive
reflected power. A low pass filter provides harmonic rejection.
1.4.3
Power Supply
The SSPA features a power supply that is power factor corrected. It supplies several voltages
necessary for the unit to operate:
The 10V and 40V power supplies output states are controlled by circuitry within the RF module. If
the RF module does not have the –5.8V supply for any reason, it will not allow the 10/40V power
supplies to turn on. This protects the power transistors within the RF module from failure due to
improper power supply sequencing.
The +24V output powers the cooling fans and the M&C circuitry.
1.4.4
Monitor and Control (M&C)
The TRP1000-4450 includes a microprocessor-based system that provides monitoring and
control of the essential parameters of the unit. The user interfaces with the unit through the M&C
system via the remote control/discrete communications port. The unit is capable of EIA-232, EIA-
485, or Ethernet remote communication. A discrete mute control and relay status output is also
available.
The M&C system monitors and controls the fan speeds, unit temperature, all power supply
voltages, power transistor currents, output power, etc. Should a critical monitored parameter fail,
the unit will mute the RF signal and report a fault. The details of the fault can be accessed via
remote communication.
1.4.5
Cooling System
The SSPA contains a robust and proprietary heat sink and thermal design to maintain a low
operating temperature. There are three larger fans dedicated to the radio frequency (RF) heat
sink, and three smaller fans dedicated to keeping the power supply cool. Each of the fans are
monitored and speed controlled by the M&C board. The fans draw cool outside air in across the
power supply and specialized RF heat sink.
The amplifier module temperature is monitored and, if for any reason the amplifier temperature
exceeds a safe preset limit, the amplifier module supply is shut down to protect the unit from
thermal failure.
