Abstract: The device comprises, in a control loop of the subtractive beat frequency fb between transmitted waves and waves received as an echo, a pursuit discriminator (11) establishing the frequency fb at f.sub.0 and a pursuit validation circuit (12). This device is characterized by the combination of a contrast discrimination set (CDS (15 to 18) and a VSE discrimination set (21 to 25) for detecting energy in a guard band situated at the upper end of the frequency bands of the CDS, the latter comprising a contrast discriminator (15), a first attenuator (16) and controlling the pursuit validation circuit (12). The VSE discrimination set is arranged for controlling the gain of the first attenuator (16).

Abstract: The invention relates to C-W radar responders, having a carrier of some gigahertz whose amplitude is modulated between some dozens and some hundreds of kilohertz. Such a responder comprises means for sampling the signal it receives in such a manner that the sampling theorem is satisfied with respect to the amplitude-modulation frequency. The responder comprises at least an aerial, a radio-frequency amplifier, a delay line, a clock generator, an input, an output and two switches connected to the input and to the output, respectively, of the amplifier. The operating sequence of the switches, controlled by the clock generator, is such that each sample of the received signal passes through the amplifier more than once before it is re-transmitted.

Abstract: A radio range measuring apparatus having a controlled modulation slope in order to keep the beat frequency between the transmitted signal and the received signal constant. The apparatus also measures the speed at which a mobile target approaches or recedes by means of a generator of a fixed frequency which, after frequency division, maintains the duration between the start of two consecutive sawtooth modulation signals fixed. A particular spectral line of the beat signal is demodulated by this fixed frequency via a mixer whose output is filtered by a passband filter. The signal at the output of the filter has a frequency which is equal to the Doppler frequency, proportional to the speed.

Abstract: Disclosed is a system for locating a transmitter arranged for transmitting frequency-modulated signals. The system supplies data about the angular deviation between the direction of the transmitter considered from a reference point and a reference axis passing through that point and comprises two antennas disposed on the reference axis symmetrically relative to the reference point, and a receiver having two mixers which receive, on the one hand, the respective signals from the two antennas through time delay elements and, on the other hand, the signal from one of the antennas through a circuit which provides, during a given period of time, a linear phase shift. The beat frequencies at the mixer outputs are measured by frequency meters during said time period and the desired information is given by the relative deviation between the output signals of the two frequency meters.

Abstract: The disclosed system is intended to supply angular and range data regarding the position of an object to be located in a reference system. The system comprises an interrogator which transmits a linearly frequency-modulated signal to a transponder disposed on the object. The transponder is provided with means for shifting the frequency of the received signal in one direction by a predetermined amount characteristic of that transponder and means for retransmitting the received signal. The interrogator further includes a pair of receiving antennas whose signals are used for forming beat signals with the transmitted signal. The interrogator is also provided with means for shifting the frequency of the beat signals in the other direction by the same amount. At least one of the shifted beat signals is applied to a frequency discriminator whose output signal is utilized for controlling the slope of the modulation signal in order to keep the frequency of the shifted beat signal constant.

Abstract: A range measuring apparatus of the linear frequency modulation type is disclosed which comprises a measuring control loop for rendering the beat frequency between the transmitted and received frequencies equal to a fixed frequency. The apparatus further includes means for forming a permanent second beat signal between two signals derived from the generator supplying the frequency modulated signal, one of these signals being delayed by means of the delay line. A phase detector receives this second pulsed signal and the signal of a controlled frequency oscillator and supplies a signal which controls the slope of the frequency modulation. The error signal of the measuring control loop controls the frequency of the signal from the oscillator. This arrangement results in an increased precision in the range measurements.