Abstract: Is disclosed a method and a relative circuit adapted to transfer to a microwave transmission carrier the angle modulation of an intermediate frequency signal. The conveyor of angle modulation is a PLL (100) which VCO (2) generates the microwave carrier (RF) modulated like the intermediate frequency signal (S4), taken as reference for the phase comparator (10) of the PLL. The comparator receives moreover a copy of the signal generated by the VCO, converted at intermediate frequency (S3) by means of a subharmonic mixer, and it generates an error signal (S5). The PLL comprises further a regulator circuit (101) which maintains automatically constant relation K between the locked band of the PLL and the bandwidth of the reference signal (S4), the lanter being a signal susceptible of band width variations, generally due to the choice of different transmission speeds.

Abstract: A voltage controlled oscillator formed as a first layout with metallized areas by a planar technique is located on a high dielectric loss substrate. A second layout formed of metallized area for control circuits of the voltage controlled oscillator is formed on a high loss dielectric substrate is also formed by the same technique as the first layout. A ground plane for the controlling oscillator is formed on an opposite side of the dielectric substrate on which the voltage controlled oscillator is formed.

Abstract: There are described a procedure and circuit for adaptive compensation of the gain distortions caused by thermal drift, ageing, etc., in microwave amplifiers connected to predistortion linearizers. The procedure concerns digitally modulated signals, e.g., QAM, in which the peak to average power signal ratio is constant. Since this ratio remains constant after amplification only if the amplifier is linear, it is measured at the amplifier output, to change the AM/FM distortion characteristic of the linearizer/amplifier chain and hold the ratio on the output equal to that on the input.

Abstract: A microwave oscillator has a cavity which is excited with an active element. The phase noise characteristic of the oscillator is improved in that a frequency discriminator utilizes the same oscillator cavity. The waves transmitted and reflected by the cavity are measured, combined and detected by a pair of low noise diodes. The signals obtained are compared to produce a control signal for a phase shifter which is connected between the active element and the cavity. The cavity is preferably a dielectric resonator.

Abstract: A predistortion linearizer for microwave power amplifiers wherein a single transistor, e.g. of the GaAsFET type, is subpolarized near the pinch-off condition, and carries out the functions both of a gain expander amplifier for recovery of amplitude distortion of the power amplifier and as a command signal generator for a dephaser element for recovery of the phase distortion of the power amplifier.

Abstract: The structure includes a conductive path and a ground plane applied to opposite faces of an insulating support. The ground plane has parallel slots placed under the conductive path and transversely thereto.

Abstract: A linearizer circuit is described having a main radio frequency or intermediate frequency network and secondary baseband frequency network. The main network includes a directional coupler, a delay line, a phase modulator and an amplitude modulator. The secondary network includes means for amplitude detecting and filtering an input signal and a pair of adjustable-gain amplifiers which receive the amplitude detected signal and on the basis of the gain adjustment act on the two modulators as to give them nonlinear response curves so as to compensate for the nonlinearity of the power amplifier placed downstream from the linearizer.

Abstract: A microwave resonating cavity including a hollow cylindrical body shaped in the form of a parallelepiped and consisting of a dielectric material coated by a metallic layer, said dielectric material having a high dielectric constant having a value greater than 30, and wherein said hollow body includes an upper base, a lower base, an external surface and an internal surface, and further includes a non-metallized area defining a metallized coupling line onto the external surface of the said hollow cylinder and wherein said hollow cylinder has an inner diameter ranging between 3 and 5 mm, an outer diameter ranging between 6 and 15 mm and a height ranging between 5 and 10 mm, and further including a metallic cap welded to the upper base of said hollow body, and further including an adjusting screw for fine adjustment of the resonating frequency.

Abstract: A directional coupler of the 3 DB and 90 degree branchline type with four ports. Four pairs of coupled lines of microstrip construction provide the connections between the ports. The first and third ports are opposite each other as are the second and fourth ports, with the first and third ports connected to associated circuits and the second and fourth ports unconnected.