Abstract: A collision avoidance system for sea navigation comprises, for each equipped ship, a transmitter that repeatedly transmits the geographic coordinates, course and speed of its own ship and a receiver that sends a display device similar data received from other ships. These received data are displayed, mostly in the form of symbols, on the panoramic screen of the display device.

Abstract: An IFF system interrogating station comprises an IFF interrogator which has its transmission antenna joined to the infra-red camera of a field observation device. Each friendly vehicle is fitted with an IFF receiver antenna and an infra-red laser transmitter transmitting a laser pulse at each IFF interrogation.

Abstract: In asynchronous mode transmission for multiple-service networks with a wide range of throughput rates, it is stipulated that the digital data will be conveyed in standard cells having a header and a data field, with fixed lengths. For the low throughput rate services, which are penalized by this type of transmission as regards their transmission efficiency, the method disclosed provides for the transmission, while performing all the switching operations on the standardized cells, of microcells on those trunk lines where this type of transmission occupies a major place. These microcells result from the cutting up of the standardized cells, preventing the transmission of unnecessary data field lengths.

Abstract: A radar, notably for the correction of artillery fire, comprises means for an antenna scan, in bearing, in a limited zone .DELTA.G around a central position coinciding with the objective in that, and means to compare the received signals with a set of reference signals representing the responses awaited from virtual targets that are evenly spaced out, in bearing, within the monitored space .DELTA.G.

Abstract: A method and device are provided for the automatic recognition of targets from "Doppler" echoes. The method consists in comparing sequentially the spectra of the "Doppler" signal retransmitted by each target with successions of spectra corresponding to known targets stored in a dictionary memory and indicating the type of target when the spectra of the signal retransmitted by the target have been recognized.

Abstract: The network of the invention comprises, in the transmitter, a "marker" generator which inserts bits of a cyclical sequence into the binary data flow and, in the receiver, a marker processing circuit by which it is possible to identify the start of the marker cycle in order to re-justify the useful data signal in accordance with the detection of this start of a cycle.

Abstract: The process for limiting traffic according to the invention comprises an AND input gate receiving the incident pulses representative of the interrogations of the system, its output being connected to an authorization output as well as to a counter which is itself connected to an adder and to a counter, the adder receiving from a memory criteria values, and its output being connected via a reference values memory to the comparator, the output of which is connected via a memory to the said AND gate.

Abstract: To increase the dynamic ratio of an amplifier, it is preceded by a switchable attenuator which is switched on when the output voltage of the amplifier exceeds a threshold, this output voltage being added to a shifting voltage.

Abstract: Device for eliminating the noise in 1/f from a Doppler radar comprising in the HF emitting system, a phase coder introducing, at frequency PRF/2 a phase shift of 0 and .pi. alternately, and in the receiving system, after the receiver, a decoder, or gain inverter progrmmable between -1 and +1, acting, in the same manner as the coder, upon the receiving signal and comprising a low-pass filter downstream from the decoder for eliminating the noise in 1/f, that appears at PRF/2, the device being applied to a ground surveying radar.

Abstract: The invention concerns beacons associated to radars.It consists in modulating the re-emitted signal, in phase by the frequency of a vocal signal, and in amplitude by the envelope of this signal.It allows vocal transmission between such a signal and a Doppler radar.

Abstract: The decoding circuit of the invention comprises essentially a digital filter 16, a pulse-width recognition circuit 17 a pulse peak amplitude selection circuit 23 and a circuit for decoding MLS boosted scanning pulse pairs 32 to 38. This decoding circuit makes it possible to eliminate parasite pulses from a clutter source whose width is incorrect when compared to the width of useful pulses and also to eliminate pulse pairs that have the right width but do not have the right interval.

Abstract: The invention relates to Doppler radar making it possible to subject the ground to surveillance.It consists of providing a conventional Doppler radar having a transmitter, a receiver, processing means making it possible to supply a binary signal indicating the presence or absence of a moving target in the given distance gate series and a display screen with means making it possible to take account of certain relative danger criteria, as a function of the distance at which the targets are located and as a function of the speed at which they are moving. These means make it possible to control the screen, in order that the relative danger is displayed in the form of an overbrightness for the targets considered dangerous.It makes it possible to improve the display conditions of ground surveillance Doppler radars.

Abstract: A process for protecting radars against jamming, in which a pseudo signal is transmitted simultaneously with the useful signal and is formed from pulses synchronous with those of the useful signal. The amplitude of the pseudo signal is higher than that of the useful signal in order that a countermeasure device hooks onto this pseudo signal and ignores the useful signal. The frequency of the pseudo signal differs sufficiently from that of the useful signal to ensure that the jamming signals, retransmitted by the countermeasure device on the pseudo frequency, are rejected in the intermediate frequency amplifier of the radar receiver.

Abstract: A coherent radar including separate transmitting and receiving chains. The transmitting chain includes a master oscillator providing a signal at frequency F0. A multiplier multiplies F0 by a predetermined amount to produce a signal at a frequency F1. A second multiplier multiplies the signal at frequency F1 to produce a signal at frequency F2, F1 and F2 being coherent with F0. A first mixer mixes F1 with F0 and a second mixer mixes F2 with the product of the first mixer to produce a transmission signal. In the receiving chain, a received signal is amplified and filtered and then mixed in a third mixer with the second signal at frequency F2 from the transmitting chain. The mixing product of the third mixer is amplified and filtered and mixed in a fourth mixer with the first signal. The fourth mixer product is then coupled to a processor for producing a radar display.

Abstract: In a microwave preamplifier of a Doppler radar system used for Earth observation, three pre-matched and self-biassed field effect microwave transistors are provided. By supplying these transistors by means of a voltage regulator, whose output voltage varies under the action of a control circuit, the gain of this pre-amplifier may be varied without modifying the standing wave ratio, thereby obtaining modulation of the microwave signal amplified by the amplifier. Thus, additional modulation may be obtained, speech modulation for example, on the transmission signal of an Earth observation Doppler radar system.

Abstract: In a microwave power transmitter for Doppler radars for terrestrial surveillance, use is made of four stages in series comprising first and second preamplifiers, and first and second power amplifiers. These stages are supplied by a group of separate voltage regulators. These regulators are controlled by a control circuit which makes it possible to cut off the stabilized voltage between instants of transmission, that is to say between microwave pulses of a radar signal. A feedback device makes it possible to stabilize the output level by causing variation of the gain of the first preamplifier by means of its supply voltage.

Abstract: In a radiotelephone system comprising a ground central station and a plurality of peripheral stations having access to a geostationary satellite, demand-assignment multiple-access (DAMA) conversations are established by single-span transmission between subscribers of the peripheral stations. In order to prevent conflicts arising from two simultaneous call demands, a rectangular-wave synchronization signal is transmitted by the central station to the peripheral stations in a specialized channel and the demands are caused to coincide with the active wavefronts of the synchronization signal.

Abstract: A mixer comprising two microstrip plates, each having an earth plane, a dielectric layer and an etched layer. One of the etched layers carries the mixer ring and input guides. The outer etched layer carries the output guide and the tuning members. The plate are joined by their earth planes and the mixer diodes are placed in the holes connecting the two etched faces.