Abstract: An optical waveguide interferometer arrangement includes a single-mode optical waveguide device which diverges into two waveguide branches of identical optical length which converge into another single waveguide. The optical properties of the two branches are variable by electrical fields applied via adjacent electrodes, which are energized with a composite waveform comprising (for example) a symmetrical ramp superimposed on a square wave of the same period. The two component waveforms are in phase but of different amplitudes such that the output light is intensity modulated at a frequency which is some multiple of that of the input waveforms. Adjustment of the square wave amplitude provides the means to phase shift the optical output signal.

Abstract: In a Doppler VOR, the phase of the carrier wave of the carrier signal must lie symmetrically between the phases of the carrier waves of the sideband signals. To monitor these phase relationships, the carrier signal received by the sideband antennas (1) is applied to two mixers (14, 15) which are also fed with fractional signals of the upper and lower sidebands, respectively. The mixer output signals are applied to a phase comparator (16) whose output signal has a predetermined value corresponding to the prescribed phase relationships. The output signal of the phase comparator (16) is compared with a reference value in a monitoring facility (19).

Abstract: A phased array radar system, such as may be used in a low-angle tracking radar or direction finding equipment, includes a multi-channel digital filter to remove unwanted multipath signals. The R.F. signals from the array are first converted to zero I.F. and digitized. After n-channel Doppler filtering (13) the digital signals are subjected to filtering (14) either to effect band-pass spatial filtering, thereby attenuating generally all signals arriving outside preset angular limits, or notch filtering which heavily attenuates signals arriving from one particular angle. In one embodiment spatial filtering is followed by notch filtering. The filtered signals are then beam-formed (15) before being applied to further digital processing, such as beam peak tracking (16).

Abstract: An end-play adjusting device including a molded thermoplastic sleeve-like member about the shaft of an electric motor armature, or the like. The sleeve is applied in a maximum axial length and subsequently compressed to reduce its axial length to whatever provides the desired end-play to the bearings or other support structure.

Abstract: An annular rotary RF coupler for installation about a vertical support structure, such as the mast of a ship. Two annuli are divided into circumferential increments providing a cellular structure of individual waveguide cross-sections. A lower annulus (stator) remains fixed, the individual waveguide sections therein being fed from a power-divided, equal-phase, feed configuration. The oppositely facing upper annulus (rotor) rotates with respect to the lower one about the common mechanical center of rotation of a mechanically rotating antenna system. Connection to the rotating waveguide sections may be through power combiner/divider means, or individual subarrays may be discretely connected to one or more waveguide sections in the rotating annulus. For power tapering across an antenna array aperture, the waveguide section dimensions in the circumferential direction within the rotating annulus are appropriately tailored.

Abstract: An annular rotary RF coupler for installation about a vertical support structure, particularly the mast of a ship. Two annular volumes are regularly divided into circumferential increments providing a cellular structure of individual waveguide cross-sections. A first annulus (stator) remains fixed, the individual waveguide sections therein being fed in equal phase from individual solid-state transmit/receive modules. The oppositely facing annulus (rotor) rotates with respect to the first annulus about the common mechanical center of rotation both share with a mechanically rotating antenna system. Connection to the rotating waveguide sections may be through power combiner/divider means (more than one rotor cell per antenna element or subarray), or individual antenna elements or subarrays may be discretely connected to corresponding waveguide sections in the rotor.

Abstract: Located adjacent to runways, taxiways, and approach ramps are secondary radar interrogators which radiate the P1 and P3 pulses and the P2 pulse via different directional patterns into sectors to be monitored which are individually assigned to each interrogator. Direction finders at different locations determine the directions of arrival of SSR reply signals radiated by an airborne SSR transponder in a sector to be monitored. From the directions of arrival and the locations of the direction finders, the respective transponder position is determined. The interrogators require no central control. Alternatively, the arrival times of the SSR reply signals are measured at several points; an evaluating device forms the differences in arrival time, and the intersection of the hyperbolic lines of position determined in the evaluating device is the position of the transponder.

Abstract: Two STC configurations for precision control of RF attenuators, each configuration utilizing a log-scale electronic attenuator, are disclosed. The first configuration includes a D/A converter/linear-to-log module combination to provide a log range ramp; the second configuration utilizes a log table ROM/D-A converter to provide a precision log range ramp, the range so generated controlling the log-scale electronic attenuator utilized in the radio frequency receiver.

Abstract: A monitor located about 100 m from the ILS localizer determines whether the DDM alarm threshold was exceeded due to an equipment error or to an error caused by an overflying aircraft. To accomplish this, either the maximum of the frequency spectrum of the variation with time of the differentiated DDM signal is located, or the frequency spectrum of the variation with time of the DDM signal or of the differentiated DDM signal is compared with one or a plurality of spectra typical of equipment errors or of errors caused by overflying aircraft.

Abstract: A modulator for RF class C amplifiers particularly suitable for transistor power stages employing FAIL-SOFT. Automatic modulation control operates to independently adjust the gains of a pair of controllable amplifiers whose outputs are then combined, filtered and applied to a class C stage. The output of the class C stage is sampled, linearly detected and processed to produce gain control time-voltage functions which compensate for class C pulse distortion so that a preserved amplified waveshape can be obtained.

Abstract: A directive antenna feed arrangement providing for multiple selectable beam locations and with the ability to provide multiple and independently locatable nulls in specific angular directions in the sidelobe structure of the radiation pattern. An antenna having a plurality of independent antenna elements linearly deployed is coupled to a beam-forming network such as a Rotman lens feed. Main beam directivity is controlled by selection of the Rotman lens ports corresponding to the desired beam direction. Other angles corresponding to the directions of unwanted signals, especially those received on the major sidelobes, are effectively nulled by a phasing network discretely connected to the Rotman lens port at the appropriate angle, the phase control receive signals being mixed with the main beam signal energy. Angle tracking and beam-steering circuits are depicted and described for control of the main beam angle and positioning of the nulls generated.

Abstract: A continuous wave pseudonoise radar system which employs a large word rate to avoid spillover and other noise. Spillover is the electromagnetic energy that is transmitted from the transmitting antenna directly to the receiving antenna. In other words, the spillover is not reflected from the target. The word frequency is thus made higher than the highest expected doppler. The high word rate would normally cause an ambiguous range indication because the word wavelength would be less than twice the maximum expected target range. However, this problem is solved by the use of coarse and fine range indicators. It is an outstanding feature of this invention that the coarse range is obtained by changing the transmitter bit rate. The difference between transmitter and receiver bit frequencies is then integrated over a selected period. The definite integral is directly proportional to range. However, the range turns out to be a function of the transmitter bit frequency only at the integral limits.

Abstract: An electronic navigation beacon, particularly for coastal navigation, in which an unmodulated carrier f.sub.c is transmitted from the first antenna of a pair of antennas, and a periodically modulated sideband f.sub.c .+-.f.sub.a is transmitted from both antennas, where f.sub.a is in the audio frequency domain. A cyclical RF phase variation is imposed on the sideband signal transmitted from the second antenna. The effect in space is that of a rotating radial having an audio frequency null, the periodic modulation providing the listener at a remote point with timing information enabling determination bearing as a function of the time of passage of the radial through the remote point relative to the start of rotation of the radial.

Abstract: The radar radiates, alternately or according to a given code, left-hand and right-hand circularly or elliptically polarized signals. At the receiving end, the two orthogonal polarized components of the received signal are processed separately, and the phase shift between the two components is measured. It is determined whether this phase shift is similar to that existing at the instant of transmission between the two orthogonally polarized components which are mixed to produce the circularly or elliptically polarized signal. The similarity check is made by correlation.A desired target is indicated if there is a given similarity. Coherent signal processing is not necessary (but possible).

Abstract: A pseudo-noise radar system in which a maximal length binary pulse code of amplitude zero or A amplitude modulates a carrier wave and reverses the phase thereof 180 degrees in synchronism. Either one of the amplitude modulated or phase reversed waves is transmitted. The received wave is then passed through a multiplicative mixer that receives the other wave as an input. The mixer output is then effectively (L + 1)/2 when correlated and effectively zero when phase shifted one bit to one bit less than a word, where L is the word length. Signals not correlated are thus attenuated to an extreme degree. The above-described pseudo-noise radar system may be used with any other conventional equipment for fire control, missile range and/or velocity tracking or otherwise.

Abstract: A Doppler Radio Navigation beacon with multi-element reference and main commutated arrays. The reference signal is programmed among the reference array elements irregularly to provide spatial diversity to the reference signal to eliminate or substantially reduce reference masking effects in certain multi-path situations (as observed at a remote receiving station such as on an aircraft on landing approach deriving angle information from said beacon). A similar irregular element excitation program is imposed on the normal array preserving coherence in the relative radiator movement (during commutation) between reference and main arrays.

Abstract: An instantaneous gain controlling system particularly for coherent (MTI) radar systems. A gain controllable intermediate frequency amplifier, a COHO, and a phase detector are shown along with an MTI canceller which itself includes a delay device and a differencer are shown. The delay device provides a full pulse repetition period of delay, and the differencer operates to subtract the coherent video at the phase detector output from the same signal train, one pulse repetition interval earlier, to provide MTI cancellation. The delayed video train is full wave rectified, passed through a threshold circuit and an adjustable gain video amplifier and used as a pulse-by-pulse gain controlling signal for the intermediate frequency amplifier. Large signal blocks are thus prevented from overloading the receiver channel with consequent spectral spreading and MTI cancellation degradation.

Abstract: A Doppler navigation system with tracking filter for reducing suceptibility to multipath signals. For acquisition of a Doppler ILS angle representing a signal within a spectrum also containing multipath signals, a self-tracking variable-Q filter arrangement is used, with wide band acquisition (low Q) followed by progressive steering of the filter center frequency to the desired signal frequency, together with decrease of the filter bandwidth to an equivalent of 2 beamwidths (high Q) at final balance.

Abstract: A method of determining, at the site of a radio beacon, the location of any beacon signal reflecting objects, in which method the beacon is caused to transmit a directionally coded signal over a given service sector, in which during said signal transmission a radio receiver is moved towards said beacon along a predetermined path in said sector, in which during said movement all beacon-derived signals received by the receiver are recorded in a form such as to be coded at least in respect of beacon related bearings and in which said recorded signals are individually isolated in such a manner as to permit identification and location of any of said reflecting objects.