Abstract: To reduce radar cells and to improve the detection of a radar system, particularly a high-frequency surface wave radar (HFSWR), the broadcast system (SEM) is capable of broadcasting basic orthogonal signals two by two and each orthogonal to itself, temporally shifted to form, respectively, broadcast radiation patterns, each including main radiation lobes (LP1, LPN) alternating with secondary lobes, the main lobes associated with the basic signals being substantially juxtaposed in space. The receiving system (SRE) is capable of forming as many reception patterns in a monitored receiving area (ZR) as cells (CESn'm) contained in the receiving area that are covered by main radiation lobes (LPn) from one of the broadcast radiation patterns and located at a bistatic distance from the broadcast and receiving systems.

Abstract: To reduce radar cells and to improve the detection of a radar system, particularly a high-frequency surface wave radar (HFSWR), the broadcast system (SEM) is capable of broadcasting basic orthogonal signals two by two and each orthogonal to itself, temporally shifted to form, respectively, broadcast radiation patterns, each including main radiation lobes (L1 , LPN) alternating with secondary lobes, the main lobes associated with the basic signals being substantially juxtaposed in space. The receiving system (SRE) is capable of forming as many reception patterns in a monitored receiving area (ZR) as cells (CESn'm) contained in the receiving area that are covered by main radiation lobes (LPn) from one of the broadcast radiation patterns and located at a bistatic distance from the broadcast and receiving systems.

Abstract: A device provides, with passive circuits only, an output voltage in which ch spectral component is phase-shifted and attenuated by programmable values in relation to the spectral component of same frequency of an input signal. An adapter circuit (CA) applies the input signal V.sub.E onto two transfer channels (VT1 and VT2) which generate two signals with quadrature spectral components and with amplitudes multiplied by a coefficient of -1-+1. These signals are added in an adder circuit (CAD) which provides the output signal. The driver circuit (CC) receives the required phase-shifting and attenuation commands and corrects, if need be, the defects of the assembly through the control signals of the transfer channels (VT1 and VT2).

Abstract: To reduce emission power, the sounding of a channel comprises a space-of-change transformation of M columns with N initial samples having equal time ranks in the last N impulse responses of a sounding signal received via the channel to produce a transformed matrix, an association with the transformed matrix a matrix of binary elements depending on respective moduli of the samples in the transformed matrix in comparison with a threshold, a spatial filtering of the matrix of binary elements to produce a filtered matrix in which each binary element represents the presence or the absence of the sounding signal in the associated initial sample, and a calculation of an impulse response on the basis only of transformed samples associated with binary elements from the filtered matrix having states representative of the presence of the sounding signal.