Apparatus for accomplishing phase equalization between two signal components derived from a common source includes circuitry for generating the sum and the difference of the two signal components and for deriving an error signal from the envelopes of the sum and difference. The error signal is mixed in a first mixer with the envelope of the sum signal and mixed in a second mixer with an envelope of an original signal from which the two input signal components to be phase equalized are derived. T...

Apparatus for canceling interference suitable for use in conjunction with stationary phased array antennas or transducer arrays designed for satellite or other communication systems employing N-phase PSK (Phase Shift Keying) modulation is disclosed. The techniques used in the apparatus involves processing of signals received by a main array and an auxiliary array of a phased array antenna so that an error signal is derived which is fed back to circuitry which modifies at least one signal receive...

The present invention relates to a method for use in a communcation system of providing efficient access by low traffic stations while keeping the buffering requirements for high traffic stations at a minimum. The method provides a TDMA architecture which includes a plurality of different frame rates which is dependent on the traffic requirements between station pairs. In operation, a sequence of a plurality of s switching frames are used to form a super frame and each communication burst of a s...

A multiplex radio transmission system is provided with facilities for initiating protective switching from a working channel to an idle channel of the system when the signal to interference ratio on the working channel falls below a predetermined threshold value. A precise square-law detector derives, from the separate information and interference components of a signal on the working channel, a DC component and a difference-beat AC component which are processed to yield a quantity indicative of...

The present invention relates to a technique for efficient spectrum utilization in mobile radio systems divided into a plurality of geometrically-shaped cells (10-21). Mobiles (24) in each cell are served by at least one base station (30-40) comprising a directional antenna having a beamwidth corresponding to the overall area of the associated cell. Each base station communicates with mobiles within the associated cell using separate primary channels (C.sub.p) within a first portion of the syste...

The present invention relates to a cooperating arrangement for a pair of space diversity stations (30 and 40) interconnected by a communication link (20) wherein each station normally communicates independently with a remote point (12) of the system while handling traffic related to a separate service region (32 and 42) or separate portion of an overall service region. At the occurrence of a fade condition at one of the two stations, the fading station alerts the other station of the pair of suc...

The present invention relates to a space diversity combiner which includes two branches wherein separate multipath signals received from a remote source are propagated. The branch signals are combined and the combiner output signal is used for obtaining noncoherent spectrum measurements which are in turn used to account for both dispersion and noise in controlling the relative amplitudes and phases of the two branch signals to provide a maximum performance measure for the combiner.

The present invention relates to a satellite communication system which uses a separate up-link and down-link fixed spot beam for communication with each of a plurality of, for example, spaced-apart high traffic demand ground areas and an up-link and a down-link scanning spot beam for communication with a plurality of, for example, spaced-apart low traffic demand ground areas on a time division multiple access (TDMA) basis. More particularly, a satellite repeater is disclosed for accomplishing t...

The present invention relates to a method of cophasing the feed elements of a transmitting or a receiving phased array antenna. To cophase a transmitting antenna, the method entails transmitting a lower sideband and an upper sideband signal from a first and a second one of the feed elements, respectively, while transmitting a carrier signal used to generate the sideband signals on all other feed elements of the array. At each receiver the reference phase angle between the received sideband signa...

An improved twister includes a base frame, a rocker, a hydraulic cylinder, a link and a rotatable disk. The base frame is provided with a pivot seat and two upright bars, the pivot seat being pivotally mounted on the rotatable disk and the upright bars being pivotally connected to the rocker. The rocker is connected to a grip link at a top end and two substantially C-shaped frame at a bottom side. The hydraulic cylinder is pivotally mounted on the base frame and has a shaft with a pivot head piv...