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R  **ON A/C 051-060, 
R  A. Receiver 
R  (1) External description 
R  (Ref. Fig. 007A) 
R  The face of the receiver is fitted with a handle, two attaching 
R  parts, a TEST pushbutton switch and two LEDs. The LRU STATUS LED has 
R  two colors (red/green). 
R  The name, color and function of the two LEDs are as follows: 
R  - LRU STATUS (red) indicates that an internal fault is detected 
R  during the front panel self-test sequence 
R  - LRU STATUS (green) indicates that no internal fault is detected 
R  during the front panel self-test sequence 
R  - CONTROL FAIL (red) indicates that no control input is available 
R  during the test sequence. 
R  The back is equipped with one ARINC 600 size one connector, which 
R  includes three plugs: 
R  - Top Plug (TP): connection with the automatic test circuits 
R  - Middle Plug (MP): service interconnection 
R  - Bottom Plug (BP): connection with the power supply circuit, and the 
R  LOC and G/S coaxial interconnections. 
R  **ON A/C 001-004,
 (2) Internal description 
R  (Ref. Fig. 008)
 The ILS receiver includes:
 - an RF module,
 - a main processor board,
 - a monitor processor board,
 - a power supply assembly,
 - a rear interconnect module, 

R 1EFF : 001-004, 051-060, 1 34-36-00Page 16 1 1 Config-1 May 01/05 1 1 1CES 1

R  ILS Receiver 
R  Figure 007A 
R 1EFF :  051-060,  1  34-36-00 Page 17 
1  1  Config-1 May 01/05
 1  1
 1CES  1

 

 ILS Receiver - Block Diagram R Figure 008
 1EFF : 001-004, 1 34-36-00Page 18 1 1 Config-1 May 01/05 1 1 1CES 1

 -
a front panel display module,

 -
a memory card module.

 (a) RF module This module converts the RF signals received by the glide slope and localizer antennas into analog signals for processing by the Digital Signal Processor (DSP). The module consists of two RF sections, one for the UHF glide slope signals and one for the VHF localizer signals. The primary difference between the two sections is in the front end circuitry due to the frequencies involved. BITE circuitry is included to both test and continuously monitor various stages of each receiver.
 1_ Localizer receiver unit
 The receiver frequency and gain are controlled by the DSP
 section of the main processor board. The antenna input is
 coupled to the mixer through the preselector, which is tuned
 by the Local Oscillator (LO) input supplied by the frequency
 synthesizer. The frequency synthesizer is tuned by the DSP.
 The preselector, in conjunction with a balanced mixer,
 provides rejection of undesired signals and immunity to
 cross-modulation and inter-modulation effects. The localizer
 synthesizer controls the localizer VCO frequency ranging from
 89.9 to 99.85 MHz. The IF frequency for the localizer is 18.1
 MHz.
 The output of the mixer is filtered by a highly selective 21.4
 MHz crystal filter.
 The amplified signal is then buffered and passed through the
 detector to provide the composite audio output levels for
 processing. A carrier-proportional DC voltage is also provided
 for Automatic Gain Control (AGC).
 Functional test is accomplished by injecting a test oscillator
 signal into the receiver and modulating the signal by the
 BITE. During normal operation, signals from the LOs, the
 synthesizer and AGC are monitored by the DSP.
 2_ Glide slope receiver unit
 The glide slope receiver unit receives and detects the
 modulated glide slope signals, in the frequency range from
 329.15 to 335 MHz. Its architecture is similar to the one of
 the localizer receiver, except that the frequency values are
 different and that there is no audio identification decoded on
 the G/S signal.

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 (b) Main processor board The main processor board controls the ILS mode of operation, generates the audio and deviation outputs, controls the aircraft interfaces and performs the control and display functions for the front panel. In addition, it also performs the in-line monitoring (BIT) tasks. The board is divided into three major sections:
　
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