The range resolution capability of the aircraft altimeter is one of the key parameters during the precise height measurements. During the landing of the rotary-wing aircraft, it is vital to detect the obstacles such as power cables, especially in poor visibility conditions like snow (White-out) and dust clouds (Brown-out) to assist a safe landing.

For lower height measurements, Frequency Modulated Continuous Wave (FMCW) radars are used to achieve a better resolution with the aid of higher bandwidth. However, this comes with two challenges: (1) the design complexity of the Radio Frequency Integrated Circuit (RFIC) (2) the high rate of atmospheric attenuation caused by the gases and aerosols.

Using the frequencies in the neighbourhood of 94 GHz for the transmission significantly reduces the atmospheric attenuation and provides an atmospheric transparency window.

In this paper, the W Band FMCW altimeter radar developed by ARRALIS is described. ARRALIS comes with the solution of both integrated circuits and modules used in a transmitter/receiver chain designed for the W Band. This provides a complete FMCW radar system working in the frequency range of 92-96 GHz with the aid of commercial off the shelf analog to digital converters and Digital Signal Processing (DSP) evaluation boards. Thus, by achieving a 4 GHz bandwidth at the centre of 94 GHz, a theoretical range resolution of 3.75 cm is achieved, which is then degraded by the windowing function factor during converting the signal into the frequency domain. The FMCW radar system uses a triangular waveform by default, which then can be converted to other waveforms as well.