Abstract: A surface wave directional detection system for determining the direction in which an electromagnetic wave propagating along a metallic surface is travelling includes a first loop probe and a second loop probe positioned in close proximity to the metallic surface so that the electromagnetic wave induces a signal in each of the loop probes. The two loop probes are separated by a quarter wavelength so that the two signals induced in the probes are out of phase. The first and second loop probes are connected by equal length transmission lines to a quadrature hybrid which generates two output signals that vary in magnitude in correspondence with the direction of travel of the electromagnetic surface wave. The two output signals from the quadrature hybrid are provided to RF detectors, which generate output voltage signals that vary in proportion to the magnitude of the output signals from the quadrature hybrid.

Abstract: Adaptive apparatus for eliminating interference from a received signal provided on a transmission line caused by radio transceivers includes a plurality of frequency tunable filters tuned to the operating frequency of a corresponding transmitter. The transmitter signal of each transmitter is provided to a corresponding filter. The filter eliminates the non-essential transmission of harmonics, intermodulation and wideband noise of the transmission signal. The adaptive apparatus includes a plurality of cancellation devices wherein each cancellation device receives a sample of each filtered transmission signal and the received signal. The received signal includes an error portion generated by the transmitters and a non-error portion corresponding to the signal received by the antenna. Each cancellation device compares the corresponding sampled transmission signal with the sample of the received signal.

Abstract: A radio system and interference cancellation system for use with the radio system include a receiving radio and a transmitting radio which are coupled to a common antenna. A reference coupler provides a reference signal in response to the signal transmitted by the transmitting radio and provides the reference signal to a vector modulator and a synchronous detector. A receiver coupler is responsive to the transmitted signal which is reflected by the antenna and to the signal which is desired to be received and provides a received signal containing an interfering signal component and a desired signal component. An error coupler samples the received signal which includes any residual interfering signal component after cancellation, and provides an error signal to the synchronous detector. The synchronous detector compares the reference signal with the error signal and provides a detector output to the vector modulator.

Abstract: An interference cancellation system employing a polar vector modulator obtains a reference signal and a received signal. The received signal has a desired signal component and an interfering signal component. The reference and received signals as well as an auxiliary signal of known frequency and amplitude, are provided to a signal correlator circuit which compares and correlates the reference and received signals and generates an adjusted auxiliary signal which corresponds to the auxiliary signal adjusted in phase and amplitude. A phase detector detects the difference in phase between the auxiliary signal and the adjusted auxiliary signal and generates a phase control signal in response. Likewise, an amplitude detector measures the amplitude of the adjusted auxiliary signal and generates an amplitude control signal in response. The phase and amplitude control signals and the reference signal are provided to a polar vector modulator having a 360.degree.

Abstract: A low current vector modulator for continuously varying the amplitude and polarity of an RF signal includes first and second hybrid couplers electrically connected at their input ports to an RF source. The characteristic impedance of the hybrid couplers is twice the impedance of the RF source. First and second PIN diodes are electrically coupled to 0.degree. and 90.degree. phase ports of the first hybrid coupler, respectively, and third and fourth PIN diodes are electrically coupled to 0.degree. and 90.degree. phase ports of the second hybrid coupler, respectively. The first and second PIN diodes and the third and fourth PIN diodes also are electrically connected respectively to first and second biasing sources. Varying the biasing provided by the first and second biasing sources varies the amplitude and phase of first and second output signals generated by the first and second hybrid couplers.

Abstract: A radio receiver having a narrow effective beamwidth includes a receiver antenna, a receiver and a receiver transmission line interconnecting the two, and an interference cancellation system having an auxiliary antenna, a first directional coupler connected to the auxiliary antenna, a second directional coupler connected to the receiver transmission line, a synchronous detector connected to the first and second directional couplers, a signal controller and a subtractor connected to the signal controller and to the receiver transmission line. The receiver antenna is selected to exhibit an omni-directional antenna pattern, while the auxiliary antenna is selected to exhibit a null in its antenna pattern.

Abstract: An adaptive feed-forward cancelling system obtains a reference signal and a sample signal from an amplifier by directional couplers. The sample signal essentially consists of an undistorted input signal component and a noise and distortion component. The reference and sample signals are provided to an adaptive interference canceller which performs an adaptive cancellation process. The interference canceller provides a cancellation signal essentially consisting of the signal component which is common to both the reference signal and the sample signal. The cancellation signal is injected into a transmission line which carries the sample signal so that only an error signal remains which essentially consists of the noise distortion component of the amplifier output signal. The error signal is then amplitude and phase adjusted to have substantially the same amplitude and to be substantially 180.degree. out of phase with the amplifier output signal.

Abstract: An interference cancellation system for cancelling at least two interfering signals received simultaneously and which is adapted to be connected to a radio receiver system having a receiver antenna, a receiver and a receiver transmission line interconnecting the receiver antenna and the receiver includes an auxiliary antenna, a first directional coupler connected to the auxiliary antenna, a second directional coupler connected to the receiver transmission line, a synchronous detector connected to the first and second directional couplers, a signal controller connected the synchronous detector and a subtractor connected to the receiver transmission line and to the signal controller. The auxiliary antenna has a non-zero phase relationship for the two interferring signals relative to the receiver antenna.

Abstract: An interference cancelling system for cancelling or minimizing multiple signal components of a received signal in a radio receiver caused by an interfering signal from a radio transmitter which interfering signal follows multiple paths to the radio receiver includes a directional coupler which samples the interfering signal transmitted from the radio transmitter and provides a primary sample signal, a transmission link which defines a primary sample signal path from the radio transmitter to the radio receiver, a power splitter for dividing a portion of the primary sample signal path into a plurality of secondary sample signal paths, a power combiner for combining the plurality of secondary sample signal paths back into the primary signal path, and a 180.degree. hybrid coupled to the primary sample signal path and to the radio receiver. The secondary sample signal paths include delay lines and attenuator pads.

Abstract: Tuning varactor circuitry is disclosed for a dielectric resonator stabilized oscillator (2). A varactor diode (22) is electrically connected in a loop (24) with an RF bypass capacitor (26), and the voltage across the diode is varied. In a first embodiment, first and second dielectric substrates (36, 38) face each other along the plane of the loop (24), with the loop (24) therebetween. In another embodiment, the loop (24) is around a peripheral side wall (52) of the dielectric resonator substrate (46). In another embodiment, the loop (24) is formed on the same surface (54) of a microstrip circuit substrate (56) with a transmission line (10).