In this thesis, we present the definition, the construction and the tests of a new V.H.F. multifrequency and multipolarization radar.This system called M.O.S.A.R., radar for the analysis of target resonance (in french : Maquette Orientée pour un Système d'Analyse de Résonances) deals with the aircraft Radar Cross Section measurements in the low V.H.F. frequency band (20 - 100 MHz).At first, we present the basic characteristics of this project such as the pulse width, the pulse rate, the number of frequency, ... . In a second part, we describe the M.O.S.A.R. system. It consists of a coherent, pulsed, monostatic radar controled by a computer, which is able to measure and record the aircraft backscattered signals. Two different antenna arrays are used for the transmitter and the receiver, each of them constitued by four log-periodic antennas. Then, target parameters (magnitude, phase and Doppler frequency) are obtained by processing methods based on autoregressive spectrum analysis algorithms using forward and backward linear prediction.Finally, we characterise the behavior and the limitations of this radar and we present several experimental results which confirm the theoretical developments.
