DSSS Based Radar Altimeter

Abstract: The basic functions of a radar altimeter is to provide accurate altitude measurements above the Earth surface with a high degree of accuracy and integrity during the approach, landing, and climb phases of aircraft operation. In this paper a design of Direct Sequence Ranging System useful for the development of spread spectrum based radar altimeter is proposed. Radar altimeter measures altitude more directly, using the time taken for a radio signal to reflect from the surface back to space vehicle. In Spread Spectrum technique the spectrum of the modulated signal is spread to cover a wider range of frequency spectrum. It offers features like resistance to jamming, transparency to unfriendly receiver, high resolution ranging etc.
Basic building blocks of a direct sequence spread spectrum based delay measurement system are simulated using Matlab. From the measured delay, the range is estimated and the accuracy /resolution o f the ranging s ys t e m is analysed from the results.

Keywords: Spread spectrum, Direct Sequence Spread Spectrum, PN sequence, Gold sequence, Radar altimeter