Abstract: The invention relates to a device for the linearization of a frequency modulation ramp comprising a voltage controlled oscillator associated with a phase locked-loop. The device comprises a digitally controlled oscillator of which only the most heavily weighted bit is used, and a digital phase comparator receiving, on the one hand, said most heavily weighted bit and, on the other hand, a signal supplied by the voltage controlled oscillator. Application to very high linearity and very high accuracy radio altimeters.

Abstract: Device for continuous phase modulation, produced from a frequency synthesizer including a variable oscillator and a phase-locked loop with, in series, a frequency division circuit, a phase comparator and a low-pass filter. In order to reduce modulation in the loop, the modulation is applied not only to the input of the synthesizer but also, in compensation, in the loop. In order to eliminate the modulation residue in the loop, a control signal for the oscillator is derived by a circuit which performs a correlation between the residue of the modulation and the output signal from a filter producing the same filtering effect as the loop, and which receives the modulation signal from the input of the synthesizer.

Abstract: An information transmission arrangement comprising transceiver units (1, 2) located in a propagation medium (10) whose attentuation varies as a function of frequency. At least one unit (1) comprise a meter (67) for measuring the level of the received signal in order to influence the frequency variation control (32) of the control oscillator (28) in the send circuit (26, 28) of the other unit (2). This arrangement profits from a monotonic attenuation gradient of the propagation medium (10) having a zone (Z1) in the 50-60 GHz band to control the send level in a simple and effective manner.

Abstract: A control circuit (10) controls a voltage controlled oscillator (15) to cause the signal at the output of the oscillator to have slopes of frequency variation in accordance with biphase encoded data to be transmitted. The control circuit (10) limits abrupt frequency shifts in the oscillator output signal by inverting a sign multiplying the slope of frequency variation, utilizing an amplifier (50) with a controllable inversion state, in response to whether the state of the data to be transmitted, and a state, indicative of whether a frequency control voltage exceeds a zero threshold at sampling instants synchronous with the biphase data, are the same or different.