Installation Manual

THALES COMMUNICATIONS
OIM
AHV1600-SYSTEM
Page 1
July 16/09
GENERAL
1. AHV1600 RADAR ALTIMETER MAIN FUNCTION
The main function of the AHV1600 Radar Altimeter is to provide the height information, via an ARINC 429
digital bus, to the aircraft navigation system, in a range from 0 ft up to 5000 ft.
It uses the fact that the electromagnetic waves propagate through the air at a constant speed c, which is the
speed of the light.
The height information is defined as the shortest distance to the "terrain" (ground or sea).
2. AHV1600 BASIC PRINCIPLE
The AHV1600 Transceiver measures altitude above ground as a function of elapsed time from the transmis-
sion of the electromagnetic wave to its return after reflection from the ground. The transmission time is di-
rectly proportional to the height above ground level.
It measures the shortest delay o between the transmitted wave and the received wave, linked to the mini-
mum distance to the terrain

o by the formula:
TERRAIN (GROUND/SEA)
h
t=2
h/c
AIRCRAFT
The AHV1600 Transceiver principle of operation is the FM/CW (Frequency Modulation / Continuous Wave)
with variable slope modulation. The basic principle of this technique is to generate a saw tooth waveform with
a slope of modulation varying as a function of altitude as shown on the figure below. The transmitted wave is
linearly modulated in frequency by the saw tooth.
c
Ho
o
.2

