Abstract: The invention concerns a method of transmitting data reliably over N normal channels (3), where N.gtoreq.1, and over at least one back-up channel (4), between a transmit end station (1) and a receive end station (2), the data transmitted comprising both traffic data and supervisory data. According to the invention, the following successive steps are performed in said transmit end station (1): the traffic data and the supervisory data applied to each of the N pairs of inputs are multiplexed on a respective one of the N normal channels; then, the multiplexed data from a "backed-up" one of the N normal channels is switched to the back-up channel.

Abstract: Apparatus for correcting quadrature error in a quadrature modulator and/or in a demodulator for a signal having a plurality of phase states, or of amplitude and phase states. The correction apparatus comprises a processor (51) which, when the apparatus is used to correct quadrature error in a demodulator, transforms the levels P and Q of the digital signals output by the demodulation stage into corrected levels P' and Q' that satisfy any one of the following eight relationships: ##STR1## These corrected levels are then applied to decision element (72), optionally after their maximum levels have equalized. The apparatus combines correction accuracy with cheapness, and it enables any quadrature error to be corrected.

Abstract: The transmitter uses a synthesized oscillator (1A) whose reference (24) is provided by the clock (H) of the data (P, Q). The demodulation oscillator (13A) of the receiver is a synthesizer which is functionally identical to that (1A) of the transmitter, and its reference (23) is provided by the clock (H, 36) recovered from the received data.

Abstract: The invention provides a digital radio link receiving device consisting of a microwave frequency part with a device for signal downconversion to an intermediate frequency, an intermediate frequency part limited to direct demodulation of the signal at intermediate frequency, and a baseband part responsible for processing the signal.

Abstract: A microwave frequency group delay corrector operates by reflecting the microwave on a correcting complex impedance (jx). It makes use of a power divider (13), of the Wilkinson type. The complex impedance (20) is connected to the port (14) which is normally the inlet port to the power divider (13). The microwave (E) is applied to one of the other two ports (15), and the remaining other port (16) is used as the port from which the phase corrected outlet microwave (S) is taken.

Abstract: A microwave filter comprising linear resonators makes use of proximity-coupled conductors situated on the first surface of a substrate of dielectric material, whose second surface parallel to the first surface is metallized to form a ground plane, in order to form the resonators. The extremities of each conductor are connected to the earth plane and the center of each conductor is equally connected to the earth plane via at least one capacitor.

Abstract: A band-pass filter comprising n principal linear resonators open at both their extremities, has integrated therewith a band suppressor function by means of p auxiliary linear resonators (p being an integer comprised between 0 and n+1), tuned to a frequency which is to be rejected and respectively connected to p resonators of the n principal resonators at a point situated close to the middle of the principal resonator in question.