U.S. Philips Corporation

Roland Allezard

Serge Paturel

Jean-Luc Degouy

The radar system of the FM/CW type transmits a wave which has a virtually linear frequency, between two frequencies f.sub.1 and f.sub.2 and supplies a first beat signal (Fb.sub.1) between transmitted and received waves; it is suitable for measuring the altitude h by measuring the overall phase rotation. According to the invention the radar supplies a second beat signal (Fb.sub.2) in quadrature with the first signal; the signals Fb.sub.1 and Fb.sub.2 are digitized (23 to 26) and comparing means (36) compare the consecutive samples of Fb.sub.1 and Fb.sub.2, then calculating means (37) derive therefrom by means of successive increments/decrements the number of zero crossings of the phase plane in a predetermined direction minus the number of zero crossings in the opposite direction (result m). The calculated altitude h is proportional to m.

Frequency-modulated continuous-wave radar altimeter system

The sensor (1), of the FM-CW type, comprises a transceiver aerial (2) which is rigidly attached to the support of the sensor and is of the frequency scanned beam steering type. The sensor radiates a frequency F of several GHz according to a sawtooth pattern which is nearly linear, generates a beat signal (F.sub.b) between a transmitted wave and a received wave an comprises an analog processing circuit (17) for the signal F.sub.b, digitizing means for F.sub.b (22), memories for time-division samples (28) and frequency-division samples (33), and digital processing means (31) transforming sequences (SU) of time-division samples into sequences (SV) of frequency-division samples. The order number of each sequence is representative of a strip of pixels of the map and the order number of a sample in a sequence is representative of a distance of a pixel on the map.

Radar apparatus for realizing a radio map of a site

The radar comprises in known manner a transmitter (1), a transmitting antenna (E.sub.1), two receiving antennas (R.sub.1,R.sub.2), mixers (6,7) and means for processing the subtractive beat signals supplied by the mixers for effecting detection of the bearing of a target (10) and of the range and/or the relative velocity of the target. According to the invention, a target simulator is provided to correct the phase errors of electrical and mechanical origins. The simulator comprises a transmission circuit including a modulator (11) and a simulated target echo transmission antenna (E.sub.2) which transmits towards the receiving antenna. The radar also includes means for processing a beat signal derived from the simulated echo and for effecting detection of the simulated target bearing and means for correcting phase errors.

Monopulse FM-CW radar system with improved axis stability

This detection system of the radar type transmits a sawtooth-shaped frequency-modulated centimeter wave. The wave reflected by an obstacle, if any, is received by two fixed receiving antennas, each of these receiving antennas being connected to a circuit for processing the received signal. The phase shift between the waves is a measure for the angle .theta. formed between the path of flight of the aircraft and the straight line which connects the aircraft with the obstacle. Said phase shift is analyzed in an output circuit of the detection device which also comprises a control loop for controlling the amplitude of the beat-frequency signal between the transmitted signal and the received signal, a synthesizing circuit for a signal fan creating a range window by demodulation of the beat-frequency signal by means of the synthesized signal, a Doppler effect tracking loop and a circuit for analyzing the leading edge of the Doppler effect in the demodulated and filtered signal. In the case of an obstacle which is substantially directly in the direction of flight, last-mentioned circuit produces an information which possibly evaluates the information with respect to the angle .theta. and which is already present in the output circuit, in response whereto an alarm circuit becomes operative.

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Verrieres le Buisson, France

Roland Allezard