User's Manual

1.3.2.11.10 System Configuration Inputs
In order to reduce the amount of effort required to program various modules within the DME/TACAN for
the proper configuration, there are eight logic signals that are sent from the RMS to each module to specify
the system configuration.
1.3.2.12 High Power Amplifier Theory
Refer to Figure 1-18 for a block diagram of the High Power Amplifier module. The 030804-0001 High
Power Module has three major assemblies. The Modulator CCA, which is also the module’s input/output
path, processes the control signals from the RTC (Receiver Transmitter Controller) to properly control the
desired output RF pulse shape and amplitude. The Power Supply CCA contains the DC/DC converters and
transmitter energy storage capacitors. The third assembly is the RF amplifier/transmitter portion of the
module. It receives a square wave pulsed RF signal from the Low Power Amplifier Module and provides
the necessary amplification and pulse shaping to obtain the desired output performance. Analog control
signals from the RTC are routed via high speed differential analog paths through the high power backplane
to the High Power Amplifier. Differential analog signals are used to suppress the effects of common mode
noise on the signal paths and to maintain the integrity of the analog control signals. Similarly, the detected
video outputs of the High Power Amplifier assembly are routed through similar high speed differential
analog paths back to the RTC, for the same reasons.
The High Power Module is used in both the 2170 High Power DME systems and TACAN systems with the
differences between the DME and TACAN versions noted below. Only minor changes are required for it
to be able to be used in either system.
1.3.2.12.1 High Power Modulator CCA Block Diagram Theory
The Modulator CCA sends and receives control signals to the RTC (Receiver Transmitter Controller) in the
DME/TACAN systems. In a dual equipment configuration, both the system 1 RTC and the system 2 RTC
provide control signals to the High Power Amplifier module via the Modulator CCA. These input signals
are routed through analog switches on the Modulator CCA. These switches are controlled by a
main/secondary switch control input from the DME system, which tells the High Power Amplifier which
set of input signals to respond to. In the single equipment configuration DME / TACAN stations, this
main/secondary switch is always configured to the “main” state, and the amplifiers will respond to signals
from the only RTC. In a dual 2170 High Power DME configuration station, with two separate high power
amplifier modules, these input signals are configured to the “main” selection for system 1, and the
“secondary” selection for system 2. The high power amplifier associated with system 1 will respond to
signals from RTC1, while the high power amplifier associated with system 2 will respond to signals only
from RTC2. In the dual TACAN configuration, where there is a common bank of 5 high power amplifier
modules combined to make the final high power output, this main/secondary select input will be set to
“main” when system 1 is on the antenna, and to “secondary” when system 2 is on the antenna. The
detected forward RF video from the output directional coupler within the High Power Amplifier assembly
is routed via two high-speed differential analog buffers to RTC1 and RTC2 simultaneously.
The modulator CCA controls the voltage to the RF amplifying transistors to obtain the proper transmitter
power and shape. The transmitter gate signal, supplied by the RTC, is applied to the first one (two in the
DME configuration of the amplifier) RF amplifier stage(s) through a high side MOSFET switch. Each
transistor has an individual modulation MOSFET. The modulating transistor switches are controlled at two
different voltage levels for a 6 dB transmitter power level change. The final amplifying stage consists of
four transistor operating in parallel and each is controlled by a high side MOSFET. Each one of the
transistors is linear modulated with the signal from the RTC that is Gaussian shaped. This determines the
output pulse modulation shape and amplitude. The forward and reverse detected RF video outputs signals
are sent from the Output CCA (012189) to the Modulator CCA where the signals are used to determine the
RF pulse shape and level. These detected signals are also monitored on the Modulator CCA for excessive
pulse width and high VSWR conditions. The output of the high pulse width and high VSWR monitor
circuits are stretched and sent to the RTC for monitoring. In addition, in the event there is a detected pulse
width fault or a high VSWR fault, the stretched outputs of these detectors will disable the High Power
Amplifier RF output for protection against damage. The forward detected video signal is also routed to the