1. A transmission frequency diversity radar system comprising an oscillator that is tunable over a frequency band to produce a signal for radar transmission, means for tuning said oscillator randomly on a random frequency basis, and means for frequency tracking the signal being transmitted including a variable frequency local oscillator, means to sweep the local oscillator over a range of frequencies within the pulse width time of the radar transmitted signal but after said transmission oscillat...

In a diversity signal combiner, the weaker of the two signals is attenuated an amount that varies as a function of the phase angle between the two signals. When the phase angle is small, the attenuation is small and the two signals add together. As the phase angle increases, the attenuation of the smaller of the two signals increases. For phase angles between 90 and 270 degrees, the contribution of the smaller signal is negligible. In digital systems, improvements in the bit error rate can be re...

The benefits of space diversity combining in the presence of interference has been found to depend upon the signal-to-interference ratios at the two antennas. For optimum results, the signal-to-interference ratios should not differ by more than .+-.3 dB. If they do, an attenuator (12) is included in the antenna circuit (10) having the poorer signal-to-interference ratio so as to reduce the signal contribution from that antenna. Optimum signal conditions are disclosed.

A radio receiver capable of receiving signals on at least two different frequencies at the same time is described. A hetrodyne frequency is selected midway between the frequencies and an intermediate frequency is selected at a frequency equal to one half of the difference of the frequencies to be received.

This invention comprises sn inexpensive, flush-mounted microstrip antenna e polarization of which is easily changed from vertical linear to horizontal linear, left-circular, right-circular or any desired elliptical sense. This enables the designer to select the polarization by selecting the proper location of shorting posts in the antenna. The use of rf switching diodes in place of conventional shorting posts provides a means of electronically switching the polarization.

A circuit and technique for directing an adaptable antenna system is described. The invention is coupled to the output of an RF receiver configured to provide a data signal output, and evaluates the quality of the receiver data signal. The invention switches antennas when the signal quality deteriorates below a predetermined level.

A diversity reception radio receiver has a two-receiver system incorporating first and second receivers. A wave envelope detector is provided for each receiver to generate an output voltage corresponding to the strength of the electromagnetic signal wave which is picked up by the receiver. A hysteresis comparator compares the outputs of the two wave envelope detectors and generates a switching control signal. A switching device responds to the switching control signal by selecting between the si...

An electrical connector includes a male electrical connector (2) having a plurality of male contact terminals (16, 18) and a plurality of male antennas connection terminals (22); a female electrical connector (3) having a plurality of female contact terminals (53) for contact with said male contact terminals and a plurality of female antennas connection terminals (65) for contact with said male antennas connection terminals; a terminal support portion (40) provided on front end of said terminal ...

In a wireless local area network, predetermined interference-detection sequences of signal points, known at both the transmitter and receiver, are transmitted over a plurality of hopping frequencies along with a sequence of data signal points taken from a modulated code exhibiting built-in diversity. In the receiver, the extent to which there are errors in the received interference-detection signal points is used as a mechanism for identifying the likely occurrence of strong interference. If the...

A combined diversity receiving apparatus comprises first mixers for mixing receiving signals from plural antennas with a signal from a feedback circuit, band-pass filters connected to outputs of the first mixers and having a band width to pass a random phase component due to fading and a main component of a modulation signal among received signals, second mixers for mixing output signals of the band-pass filters with the received signals, a coupler for combining outputs of the second mixers, and...