A space diversity system for transmitting digital microwaves is disclosed. Each of two antennas receives a direct wave and an interference wave. The output phase of one of the two antennas is controlled to combine an output thereof with that of the other antenna, so that the interference waves cancel each other and a vector sum of the direct waves is produced as a combined output. Even if the two antenna inputs are so much alike, the combined output level and thereby the signal-to-noise ratio is...

A plurality of signals to be separated in time as well as in frequency are imultaneously applied to the input of a power amplifier whose output is applied to the input of a fast-tuned filter. The filter is capable of being almost-instantaneously tuned to any of the frequencies of the input signals to control the output at any given time or combinations of times. The filter is in the form of a coaxial section with an input to the inner conductor of the coaxial section and the output taken from a ...

A diversity system using a phase control circuit for combining respective outputs of a plurality of routes of different path lengths transferring the same analog signal. An analog variable delay circuit, which is capable of controlling its amount of delay by varying the repetition frequency of clock pulses, and a low-pass filter connected to the output of the analog variable delay circuit are inserted in each route other than a reference one of the plurality of receiving routes. A phase differen...

1. A frequency diversity radar transmission system comprising a source of curring periodic pulses, a magnetron type oscillator adapted to be voltage tuned for generating continuous waves of radio-frequency energy, means responsive to said pulses for voltage tuning said magnetron whereby the continuous wave output frequency of the magnetron is instantaneously shifted to successive discrete frequencies by successive pulses and the respective discrete frequencies are maintained constant for the per...

A space diversity system capable of operating accurately over a wide range of received input electric field strengths. With a middle or high received electric field strength, a search operation for the antenna with the highest strength is commenced in response to noise detected in the output of the antenna presently selected. With a low received electric field strength, the search operation is carried out in response to noise such as white noise at all times.

A space diversity communication system is presented in which the effects of signal fading are reduced through the cooperative receipt by closely spaced antenna sensor elements and the processing in a hybrid network of signals originally transmitted as a single intelligence-modulated carrier, though susceptible of multiple path propagation. Sum and difference signals are developed for analysis in a novel diversity signal selector or combiner. In one form, the latter may develop signals for electr...

An alarm system incorporating radio links between a plurality of remotely located alarm condition sensing units and a central receiving station. Each alarm condition sensing unit is comprised of at least one sensing means which is comprised of an alarm sensing element in combination with a frequency diversity radio transmitter means. The transmitter means of all of the sensing units transmit frequency diversity carrier signals having the same carrier frequencies but the carrier signals associate...

A diversity combining arrangement for combining signals on at least two paths, each path comprising, a muting circuit and means for detecting a pilot frequency signal on the path, control means being provided, responsive to a loss of pilot frequency on the path for rendering the associated muted circuit operative, the control means for each path being interdependent such that upon a loss of pilot frequency on more than one path all of the control means are inhibited from rendering the muting cir...

1. An anti-jamming radar system, comprising; a voltage tunable magnetron, means for controlling the output frequency of said voltage tunable magnetron, a low frequency oscillator, means for modulating said voltage tunable magnetron output with the output frequency of said oscillator, said last-named means including means for suppressing the voltage tunable magnetron frequency, means for pulsing said modulating means to add pulse information to the output signal of said modulating means, a travel...

This relates to a predetection maximal ratio digital diversity combiner for a phase shift keyed digital data signal propagating on N different paths through a dispersive medium, where N is an integer greater than one. Each of N signal channels respond to the data signal propagated on a different one of the N different paths. Each of the channels include an arrangement to separate the data signal into an inphase component and a quadrature component and also a pair of analog-to-digital converters ...