Abstract: Apparatus for the observation and identification of helicopters by means of an FM-CW radar apparatus provided with transmitter means (1), antenna means (2) and receiver means (3). Blade flashes caused by the rotor blades are digitized by A/D converter (4) and processed by Fourier analysis means (5) and processor (6) in order to determine the range from a helicopter to the radar apparatus and the rotor symmetry characteristics. These symmetry characteristics, together with the blade flash repetition frequency yield a substantially unambiguous indication of the helicopter type.

Abstract: Moving target indication unit provided with a doppler filter bank (1) with n output channels A.sub.i (i=0, 1, 2, . . . , n-1), several threshold circuits (24.i) connected to the output channels, a detection and registration unit (7, 14, 18, 23) provided with means (7, 14, 18) for the determination and registration, per azimuth cell, of a parameter for the amount of clutter in an azimuth cell. The said means are further suitable for determining, based on the output signals of the filter bank (1), k (k.gtoreq.2) parameters per azimuth cell and processing per azimuth cell the combination of k parameters to obtain n threshold values, used to set the n threshold circuits.

Abstract: A pulse radar apparatus is provided with a coherent transmitting and receiving unit (1) for the transmission of radar pulses, the reception of echo signals, and the conversion of the echo signals into signals of an intermediate frequency f.sub.if, which may be shifted through a Doppler frequency f.sub.d. The echo signals with frequency f.sub.if +f.sub.d are fed to a detector (7) for the coherent phase detection with a frequency f.sub.if +f.sub.c. The detected signals are fed to an analog-to-digital converter (10), which operates at a frequency of approximately 4f.sub.c. The pulse radar apparatus further includes accumulators (12, 13), alternately fed with the output signals of the analog-to-digital converter (10) each time for a given period, after which period the output signals of the accumulators (12, 13) are representative of the orthogonally detected components of the echo signals.

Abstract: A pulse radar apparatus is provided with a coherent transmitting and receiving unit with N juxtaposed receiving antennas and N receivers for the reception of echo signals and the processing thereof into two orthogonally phase-detected and digitized video signal components i.sub.r and q.sub.r, where r=0, 1, 2, . . . , N-1. A beamformer is provided to derive from these components the orthogonal components I.sub.k and Q.sub.k of the video signal determined jointly by the N receivers in accordance with a receiving beam pattern k corresponding with a specific elevation interval, where l=0, 1, 2, . . . ,N-1. The orthogonal components I.sub.n, Q.sub.n and I.sub.n+1, Q.sub.n+1 supplied through two adjoining beamformer output channels n and n+1, and derived from the video signals P.sub.n, P.sub.n+1 from echo signals of maximum amplitude received from moving targets, are used for determining the deviation (.DELTA..alpha.) of the elevation value .alpha.

Abstract: Search radar apparatus containing an MTI video processing unit provided with: a canceller for generating video signals of moving targets; a zero-velocity filter for generating clutter video signals; a conditional circuit connected to the canceller and the filter for generating per range quant of each radar scan a clutter switching signal if for the rang quant the signal value obtained with filter is greater than the signal value obtained with the canceller; a combination circuit connected to said filter and the conditional circuit for selecting the clutter video signals present with the clutter switching signals and for determining therefrom a temporary clutter level in each clutter cell and each antenna revolution period; and clutter level indication means connected to the combination circuit for determining a standard clutter level per range-azimuth clutter cell of the radar range with the application of clutter video signals.

Abstract: In a pulse radar apparatus target returns are detected, sampled, digitized per range quant and frequency analyzed. The apparatus includes a cell classification unit (5) for deriving from the spectrum of the target returns a cell classification signal, whose logical values indicate whether the target returns within a radar cell are classified to be from a moving target or from a fixed target. In a microprocessor (15) the cells, which cluster, while a signal represenmtative of the target covered by the collectively cover one single target, are combined to form a cluster is determined. In the microprocessor (15) a cluster classification signal is derived, whose logical values indicate whether the target returns within the cluster are classified to be from a moving target or from a fixed target. The signal representative of the target covered by the cluster is read out if it is derived from target returns classified to be from moving targets.

Abstract: In a pulse radar apparatus target returns are detected, sampled, digitized per range quant and frequency analyzed. The apparatus includes a cell classification unit (5) for deriving from the spectrum range of the target returns a cell classification signal, whose logical values indicate that the target returns within a radar cell are classified, in the first instance, as first trip and multiple trip signals. In a microprocessor (12) the cells, which collectively cover one single target, are combined to form a cluster, while a signal representative of the target covered by the cluster is determined. Furthermore in the microprocessor (12) a cluster classification signal is derived, whose logical values indicate that the target returns within the cluster are classified as first trip and multiple trip signals. The signal representative of the target covered by the cluster is read out if it is derived from target returns classified as first trip echoes.