Honeywell International Inc. DMA-37B2 Manuel D’Utilisation

Page 19

10 Oct 2007

DMA-37B DME System

© Honeywell International Inc. Do not copy without express permission of Honeywell.

(4) Video Processor

(a) This module contains a field programmable gate array (FPGA) which is the control 

center for the video processor. The video processor provides the following 

operations:
• Converts tuning commands from CPU to serial data to tune the transmit/receive 

frequency synthesizer

• Generates the corresponding receiver preselector tuning voltage
• Generates the corresponding X or Y pulse modulation for the interrogation
• Generates the output mutual suppression pulse for an interrogation
• Detects the input mutual suppression pulse and inhibits reception and video 

processing

• Determines the log IF noise threshold setting
• Starts the range (distance) counter when an interrogation is transmitted
• Digitizes the video signals from the receiver log IF amplifier
• Validates the amplitude, spacing, and width of the digitized video pulse pairs
• Stores the range counter value in a FIFO when each valid pulse pair is decoded
• Analog-to-digital converter devices to process the received signals and BITE 

test point voltages

• Generates the audio tone for the Morse code station identity aural output
• Provides for integrity testing.

(5) Power Supply Assembly

(a) This module is a self-contained, high-efficiency power supply that converts the 

115 V ac, 400 Hz AC power into the required DC operating voltages. It includes an 

EMI filter to reduce electromagnetic interference from being radiated from the power 

lines.

(b) The power supply for the -1101 and -1212 units can operate in accordance with the 

DO-160E VF 360 Hz to 800 Hz mode and has harmonic content (power factor) 

correction.

(6) HIRF/Rear Interconnect

(a) The rear connector assembly provides the interwiring from the aircraft interface to 

the internal modules. A combination of series resistors, transorb devices, and ferrite 

pin filters provide HIRF and lightning protection.

(b) For the -0101, -0202, and -0303 units only, to prevent High Intensity Radiation 

Fields (HIRF) or lightning from affecting operation by entering through rear 

connector cables, an HIRF compartment is formed in the rear of the DMA-37B. The 

signal and power cables are filtered by using discrete and distributed filter elements 

and limiting devices on the rear interconnect module located inside this HIRF 

compartment. The filtered lines are then fed to the appropriate points in the 

DMA-37B. The DMA-37B is packaged in an aluminum casting. This seamless main 

frame ensures HIRF cannot enter the unit through structural seams. The slots 

formed by the removable side covers are sealed against HIRF with protective 

gaskets and metal covers.