-the AGC voltages of the LOC and G/S receivers are checked for acceptacle range,
 -
both synthesizers (LOC and G/S) are tested for lock/unlock conditions,

 -
both anti-aliasing filters (LOC and G/S) are tested for

 frequency response. Localizer and Glide Slope failures detected during self-test remain latched until the same test passes on a subsequent self-test execution.
R (3) Not Applicable
 1EFF : 001-004, 1 34-36-00Page 24 1 1 Config-1 May 01/05 1 1 1CES 1

R  **ON A/C 051-060, 
R  (2) Internal description 
R  (Ref. Fig. 008A) 
R  The ILS receiver consists of five units: 
R  - the localizer receiver unit 
R  - the glide slope receiver unit 
R  - the I/O processor unit 
R  - the power supply unit 
R  - the BITE processor unit. 
R  (3) Operating principle 
R  (a) Localizer receiver unit 
R  The localizer receiver unit receives and detects the localizer 
R  modulated signals in the frequency range from 108.1 to 111.95 
R  MHz. 
R  In approach mode, the RF signal received through the dedicated 
R  antenna is the filtered by a low loss broadband filter, and then 
R  mixed with the output of the localizer synthesizer. This 
R  localizer synthesizer receives tuning information from the I/O 
R  processor, and provides an injection signal which is 20.05 MHz 
R  below the selected frequency. 
R  The 20.05 MHz Intermediate Frequency (IF) tuned signal obtained 
R  at the output of the mixer is applied to a 20.05 MHz crystal 
R  filter which provides the selectivity for the receiver. It is 
R  then amplified and mixed with a second injection frequency 20.505 
R  MHz to produce a 455 kHz signal. 
R  After 2 stages of amplification, this second IF signal is applied 
R  to an envelope detector. The output of the envelope detector, 
R  which only contains the baseband components of the second IF, is 
R  fed to: 
R  - the Automatic Gain Control (AGC) amplifier/filter, which 
R  controls the gain of the different IF amplifiers according to 
R  the amplitude of the IF output 
R  - the Input/Output (I/O) processor unit for audio identification 
R  decoding and localizer deviations computation. 
R  (b) Glide slope receiver unit 
R  The glide slope receiver unit receives and detects the modulated 
R  glide slope signals, in the frequency range from 329.15 to 335 
R  MHz. Its architecture is similar to the one of the localizer 
R  receiver, except that the frequency values are different, and 
R  that there is no audio identification encoded on the G/S signal. 

R 1EFF : 051-060, 1 34-36-00Page 25 1 1 Config-1 May 01/05 1 1 1CES 1R ILS Receiver - Block Diagram R Figure 008A

R 1EFF : 051-060, 1 34-36-00Page 26 1 1 Config-1 May 01/05 1 1 1CES 1

R  Additionally, the glide slope receiver unit includes a localizer 
R  and glide slope functional test oscillator/modulator (90 and 150 
R  Hz tones) which generates three functional test conditions: 
R  - centered signal condition 
R  - down/right signal condition 
R  - up/left signal condition. 
R  During the down/right and up/left sequence, a 1020 Hz signal is 
R  added to the localizer 90 and 150 Hz tones. 
R  The functional test oscillators are kept off except during 
R  functional tests to prevent possible interference with normal 
R  operation. 
R  (c) I/O processor unit 
R  The I/O processor unit comprises three separate processors: 
R  - the primary Digital Signal Processor (DSP) 
R  - the monitor Digital Signal Processor (DSP) 
R  - the system processor. 
R  1 DSPs_ 
R  The DSPs compute the deviation data from the analog outputs of 
R  the localizer and the glide slope receiver units. 
R  Each DSP, identically but separately: 
R  - receives, filters and digitizes data from the glide slope 
R  and localizer receiver units 
R  - processes these data and elaborates localizer and glide 
R  slope deviations (DDM) 
R  - determines the DC level of the glide slope and localizer 
　
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