Abstract: A method and apparatus for eliminating multiple-time echoes from the output signal train of random PRF pulse Doppler radar system. A multiple-time echo is recognized by calculation of the absolute value of the difference between the last two phase pulses received in each range gate (bin). That absolute value is compared to the average of the preceding N absolute value. A multiple-time echo is present if the last absolute value is higher by a predetermined amount than the average of the preceding N absolute values. A logical switch provides automatic switching to substitute a previous phase pulse in a corresponding range gate when the phase pulse of a range gate is determined to be altered by presence of a multiple-time (non-coherent) echo signal.

Abstract: A null pattern technique for reducing the effect of an undesired interfering signal in a data link channel, using an accepted monopulse tracking arrangement in a novel mode, such that the source of such interfering signal can be caused to be placed at the null of the antenna pattern used, thus greatly increasing the desired-signal-to-interfering-signal ratio without necessitating a physically large antenna.

Abstract: 1. In passive detection and tracking apparatus, in combination, a plurality of directional signal obtaining means for obtaining from radiant energy received from the same source a plurality of signals which vary in predetermined manners with variations in the direction from the passive detection and tracking apparatus to said source, gating means operatively connected to said plurality of signal obtaining means, and indicator means operatively connected to said gating means, said gating means being constructed and arranged to pass to the indicator means certain signals only while said plurality of signals have preselected relative characteristics with respect to each other, said indicator means being constructed and arranged to utilize the passed signals to provide an indication of the direction to said source.

Abstract: This detection system of the radar type transmits a sawtooth-shaped frequency-modulated centimeter wave. The wave reflected by an obstacle, if any, is received by two fixed receiving antennas, each of these receiving antennas being connected to a circuit for processing the received signal. The phase shift between the waves is a measure for the angle .theta. formed between the path of flight of the aircraft and the straight line which connects the aircraft with the obstacle. Said phase shift is analyzed in an output circuit of the detection device which also comprises a control loop for controlling the amplitude of the beat-frequency signal between the transmitted signal and the received signal, a synthesizing circuit for a signal fan creating a range window by demodulation of the beat-frequency signal by means of the synthesized signal, a Doppler effect tracking loop and a circuit for analyzing the leading edge of the Doppler effect in the demodulated and filtered signal.

Abstract: A sky wave DF antenna system is disclosed. It is able to respond to an incoming transmitted signal and define the direction of the transmitter. It utilizes six or more simple loops connected and arranged to form a spaced loop antenna system which indicates the incoming direction of the transmitted signal without regard to the polarization or the elevational angle of the sky wave.

Abstract: A navigational-aid apparatus and method involving the use, on a target station or a craft station, of at least two transmitters, separated by a base-line distance, of distinguishable sonic signals and a transmitter of radio or other electromagnetic signals and, on the craft station or the target station respectively, of three receivers for the sonic signals and a receiver for the electromagnetic signals, the receivers for the sonic signals being in two positions separated by a base-line distance, there being two receivers, one for each sonic signal, in one said position and a receiver for one of the said sonic signals in the other position, while the station having the said receivers is provided with timing means for determining the elapsed times between the reception of the electromagnetic signal and the reception of the respective sonic signals.

Abstract: 15. In a secure communication system a transmitter comprising first means to modulate a carrier wave with a sub-carrier wave and a desired signal, a code generator synchronized to said sub-carrier wave, second means to modulate the output of said first modulating means with the output of said code generator, and means to transmit the output of said second modulating means to a distant receiver.

Abstract: Thermoelectric generator assembly accommodating differential thermal expansion between thermoelectric elements by means of a cylindrical split follower forming a slot and having internal spring loaded wedges that permit the split follower to open and close across the slot.

Abstract: An intermediate frequency sidelobe canceller with provision for controlling the saturation level of the cancellation loop. Such control is provided by interposition of limiter means at a particular point in the cancellation loop, and it enables the setting or programming of the loop cancellation time constant as desired. It significantly enhances performance and reduces cost of the canceller loop by reducing substantially the signal power levels within the loop and by making the loop transient response essentially constant over a wide range of input power level.

Abstract: The disclosure relates to radar methods and systems for directionally selective detection of objects and determination of the distances to the objects. A rectangular-wave frequency-shifted radar signal is employed. This radar signal may be generated by inducing a directionally dependent Doppler shift which permits directionally selective detection. Higher and lower frequency portions of the returned radar signal are separately frequency converted and phase compared to determine range. In a preferred embodiment, a collision avoidance system for automobiles is provided.

Abstract: A doubly-ridged waveguide device acts an an electrical-length equalizer or hase compensator for a pair of horn antennas of different physical length and/or aperture size. The phase compensator comprises a central doubly-ridged waveguide section with a uniform cross-sectional area and two similar doubly-ridged tapered waveguide transmission lines with cross-sections and ridge depth that continuously vary, located at either end of the central section. The width of the ridge is constant along the entire length of the structure. The device is connected in the standard waveguide transmission line of the smaller of the two horns.

Abstract: A fixed array of three identical directional receivers, each having a carid directional pattern, are arranged in a symmetrical configuration with each receiver having its principal axis of maximum sensitivity oriented 120.degree. from the corresponding axes of its neighbors. By comparing the relative magnitudes of the voltages generated in each of the three cardioid receivers upon receiving a signal, the bearing of the signal source is automatically determined and displayed. The tri-cardioid receiving array overcomes the prior art need for large-sized directional receiving transducers, and also overcomes the need for mechanically rotating or electronically scanning the receiving array to find the bearing of the signal source.

Abstract: An orientation system adapted to be mounted within a vehicle, comprising a display including a rotational heading indicating compass card fabricated from an image retaining electronic display panel responsive to bearing data signals.

Abstract: Disclosed is an electronic signal processing system for an alternating voltage input signal. A phase-locked loop network has an input adapted to receive the signal and produce an intermediate signal comprising a substantially noise free sine wave with a phase equal to the average phase of the input signal. The intermediate signal is applied to an input of a variable gain amplifier which produces an output signal proportional to the intermediate signal, and an amplitude averaging loop network has the input signal and the output signal as its inputs and produces a biasing signal which is applied to a control input of the variable gain amplifier to maintain the output signal equal in amplitude to the average amplitude of said input signal. The system can be used in a Watson-Watt type radio direction finder to eliminate noise.

Abstract: A correlation receiver for detecting and measuring the angle-of-arrival of adio frequency signals, including two antennas, a correlation processor, and a CRT display.

Abstract: A pulse radar device had pulsed storage devices which are arranged in the signal analysis component and comprise, in particular, shift registers. The clock frequency for the shift registers is derived from a reference frequency. Within the radar period duration, a first time zone is defined as the actual analysis zone and signal processing is carried out with the clock frequency predetermined by the requisite range resolution, and a second time zone is defined (dead zone) in which a different clock frequency is selected.

Abstract: An electronic navigation system ground station, which may be either an omni-range beacon (such as VOR) or a passive direction finder. A circular array of antenna elements has a feed arrangement which includes switched programming of at least one discrete set of phase shifters to effect successively changed phase-rotation fields for minimizing the adverse effects of multipath signals between the ground station and a remote station, aboard an aircraft for example.

Abstract: A collision avoidance system using on-board B-CAS equipment having an object to minimize interference with the ground SSR stations and to effect precise tracking or distance-altitude measurement when necessary. Normally passive surveillance is made to detect the presence of other aircraft in the B-CAS range. Active surveillance is added when required. In the active surveillance mode, initiated on locating an intruder aircraft, the power and interrogation signal are varied when the intruder aircraft becomes a threat aircraft to minimize interference with the ground SSR stations and aircraft outside the threat zone while maintaining accuracy of detection and tracking of the threat aircraft at a high level.

Abstract: A Loran-C antenna and coupling circuit therefor are disposed at a given site, the antenna and coupling circuit therefor being capable of both transmitting and receiving. A first circuit is disposed at the given site coupled to the antenna coupling circuit to detect far-field remote signals and a second circuit is disposed at the given site coupled to the antenna coupling circuit to detect far-field local signals.

Abstract: A series coupled inductance and active current conducting device are coupled in parallel with a winding of an output transformer of a horizontal deflection generator. Flyback pulses integrated in sawtooth waveforms are combined with a vertical rate parabolic waveform derived from a vertical deflection generator and coupled to a control electrode of the active device for controlling its conduction during each flyback interval at a vertical rate for loading the output transformer and thereby altering the horizontal scanning current in a manner to correct for side pincushion distortion.