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1.4.1 SSPA Module
The amplifier module performs the core function of the unit. An isolator is at the RF input to
ensure good VSWR. The RF signal then passes through an input sample port and on to an
electronically controlled attenuator that adjusts the overall attenuation according to the user input.
After some amplification, a second 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 combining
techniques to meet the rated power requirements. The output circuitry contains a coupler to
provide a sampled signal for monitoring purposes. A power detector circuit also is included, and
the reading is accessible via remote communication. A high-power circulator and load is located
at the output to provide good VSWR and protection from external mismatch.
1.4.2 Power Supply
The SSPA features a removable power supply that is also power factor corrected. It connects to
the main chassis via a specialized connector capable of the required high current. It supplies
several voltages necessary for the unit to operate. The 10V output is capable of 2000W and
supplies current to the power transistors in the RF amplifier module via two paths, or cables (10V
A and 10V B). Circuitry within the RF module controls the output status of this power supply. If
the RF module does not have the –5V supply for any reason, it does not allow the 10V power
supply 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 is the source
of power for waveguide switching when the SSPA is used in redundancy configurations. The
+5V and +15V voltages are used to operate the M&C board and other overhead functions.
1.4.3 Cooling System
The SSPA unit contains a robust heat sink and thermal design to maintain a low operating
temperature. Two temperature-controlled fans, which are monitored by the M&C board, draw
cool outside air in across the power supply and specialized heat sink and exhaust the warmer air
out the bottom of the unit. 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.
1.4.4 Monitor and Control (M&C)
The unit 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
J6 | COM1 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 the fan speed, 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.
Introduction
HPOD C-, X-, Ku-Band High-Power Outdoor Amplifier
1–6
Revision 9
MN/HPOD.IOM
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