Abstract: A relatively small directional loop antenna adapted for use in an airborne automatic direction finder (ADF) is made to perform like a physically larger loop while being broadly tuned to a mean operating frequency. The total input equivalent noise source is kept low by coupling the loop into an impedance comprised of an active circuit. The active circuit is designed in conjunction with an active feedback circuit into which the ADF sense antenna is fed to maintain a relatively constant phase difference between the ADF loop and sense signals.

Abstract: In a non-storage CRT display system having a reiteration memory wherein video information is received in a .rho..theta. coordinate system and displayed on an XY raster the input coordinates are transformed as received digitized video information is transferred from an input buffer to the reiteration memory so that information previously stored in .rho..theta. format in the input buffer is subsequently stored in an XY format in the reiteration memory. The coordinate transformation is accomplished by calculating, at the completion of the read-out for display of a given horizontal line of data, the X and .rho. addresses of the reiteration memory cells to be up-dated from the input buffer during read-out of the subsequent horizontal line of data read-out. When the calculated X and horizontal X addresses correspond the reiteration memory is up-dated with calculated .rho. values.

Abstract: An integrity monitor includes means at the ground station for periodically transmitting an integrity test signal comprising a coded first portion which identifies the signal and a coded second portion which is equivalent to a predetermined quantity. The airborne station includes a decoder which determines the type of test signal received and decodes the second portion to obtain a number which, if the system is operating properly, will compare favorably with a fixed reference. If the comparison is unfavorable, an alarm is sounded.

Abstract: A coherent demodulator for recovering the phase modulation from an input intermediate frequency signal includes a phase locked loop having switchable frequency and phase detectors. During initial acquisition the phase locked loop frequency is adjusted to be equal to the input intermediate frequency by comparing the loop frequency with the input frequency in the frequency detector and using the resulting error signal to adjust the loop frequency. After acquisition the phase detector maintains the loop frequency phase locked to the input frequency by now using the resulting error signal to adjust loop frequency phase, the error signal from the phase detector being the recovered phase modulation. A second control loop includes a narrow pass filter tuned to the desired frequency of the loop frequency. The error signal from the second loop is summed with the first mentioned error signal to precisely maintain loop frequency.

Abstract: A protected aircraft having a discrete address beacon transponder includes a ground base air traffic control radar beacon system (ATCRBS) interrogator, a collocated discrete address beacon system (DABS) transponder and a directional antenna on the protected aircraft. The protected aircraft synchronizes a local clock with the pulse repetition frequency (PRF) and scan rate of the ATCRBS interrogating his field of interest from which information the protected aircraft can calculate the azimuth angle of responding intruder aircraft with respect to the ground station. By means of his directional antenna the protected aircraft also determines the azimuth of the intruder with respect to itself. Interrogation by the protected aircraft of a collocated ground DABS transponder or a DME or other suitable means of measuring range provides a data base which together with the aforementioned azimuth angles permits the protected aircraft to calculate instantaneous position of the intruder relative to his own.

Abstract: The output of a fast frequency hopping VCO is mixed with the output of a conventional slow acquisition frequency synthesizer to produce an IF which is applied to a frequency discriminator where the IF is compared with a reference IF to provide an error signal which is digitized and stored in a memory. Subsequently, the error signal is applied together with a command signal to the VCO to obtain the desired frequency output.

Abstract: A read-out system for a portable noise dosimeter uses light coupled signals to obtain a noise level read-out display. The light signals are coded to effectively prevent extraneous light signals from causing read-out.

Abstract: The positive portion of the differentiated negative envelope of a detected radar return signal is divided into range cells. The first range cell is taken and doubled to provide a first and succeeding range cell to comprise a Doublet. The Doublets are integrated in a sliding window detector and beam split to supply the target coordinates.

Abstract: In a microwave lens of the Rotman type for a scanning beam antenna a plurality of radiating feed probes are spaced along the focal arc. An illumination function is then commutated around the focal arc by energizing groups of the feed probes simultaneously in accordance with weighting functions to thereby cause the resulting radiated beam to scan in small equally spaced increments while the array factor remains essentially constant. Methods of calculating the weighting functions and feed probe spacing are shown.

Abstract: In a microwave lens antenna of the parallel plate type for scanning a beam wherein a plurality of feed probes spaced along the focal arc are simultaneously excited in groups in accordance with weighting functions, the phases of the feed probes are optimized by predetermination of the lengths of the coaxial cables supplying energy to the feed probes.

Abstract: A linear driving circuit includes a full bridge drive circuit across which a d.c. motor is connected. Each side of the bridge circuit is controlled by an associated complementary transistor loop, each of which is in turn controlled by an associated control operational amplifier. Each control operational amplifier is referred at one-half the voltage across the bridge circuit by a common voltage divider. The currents through each half of the bridge circuit are compared to provide current feedback.

Abstract: An integrated airport terminal area surveillance system, including a plurality of spaced apart interrogating and receiving stations and central equipment for controlling the stations operates in search and track modes by transmitting interrogation messages and receiving resulting replies. In the search mode the stations interrogate by directional beams all aircraft operating within the entire terminal area and enrolling the position and identification of replying aircraft into a system memory. In the track mode those aircraft enrolled in the system memory are individually interrogated. A system map is divided into memory cells corresponding to predetermined geographical cells. The means by which an aircraft is interrogated is determined by the geographical cell in which the aircraft is located.

Abstract: A multi-mode radar includes a local oscillator referenced to the radar magnetron and includes logic provided to side step the local oscillator during the latter portion of the radar interpulse period so as to permit adjustment of the receiver gain during this period without interference from distant targets. In addition, IF amplifiers are selectable in accordance with the operational radar mode selected.

Abstract: A broadband concentric power combiner or divider for use with microwave frequency signals is in the form of a multi-section folded transmission line. The folded transmission line is comprised of a plurality of concentric cylinders wherein the outer conductor of one section comprises the inner conductor of an adjacent section, the various cylinders being the various conductors.

Abstract: A beam scanning through a receiver is detected at the receiver deriving a threshold level from the peak of the received beam, the threshold being used to detect the received beam envelope as delayed by an analog delay circuit.

Abstract: In a radar display system wherein radar return signals are received at a first rate and displayed at a second, usually higher rate, each radar return signal is digitized and used to update a main memory comprised of a random access memory so that the main memory contains information related to a plurality of radar return signals arranged therein in a logical order. The main memory information is continuously clocked out for display by an address counter which counts through two complete cycles in a first stage before incrementing a second stage so that the stored information related to each radar return signal is read out for display twice consecutively before the stored information related to the next radar return signal is read out for display.

Abstract: A high speed a.c. voltage regulator comprises a transformer having a plurality of switchable primary windings across which an unregulated voltage is impressed and which control the regulated voltage, and a secondary winding across which the regulated voltage is generated. During a regulation period, which comprises one cycle of the unregulated voltage frequency, peak unregulated input voltage is compared against an upward ramping reference voltage to control a source of clock pulses, where the instantaneous level of the reference voltage is related to the number of clock pulses generated during a regulation period. The number of clock pulses generated during a regulation period controls the switchable windings.

Abstract: A thermomechanical vacuum regulator adapted for use in automatic temperature control systems includes a bimetal strip which flexes in accordance with the temperature of air stream whose temperature is to be controlled. The bimetal strip positions a whiffle tree beam which carries a vacuum valve for communicating a source of vacuum with a chamber within which vacuum is regulated, and a vent valve for communicating the chamber with a source of ambient air. The vent valve seat is located on a floating diaphragm which forms one wall of the chamber. In alternative embodiments, one of the valves is replaced by an orifice and column.

Abstract: An antenna and scanning means therefor particularly useful in an aircraft landing system operating in the microwave frequency range. The antenna is of the line phased array type which includes digitally controlled phase shifters for each of the radiating elements of the array. The beam formed by the antenna is steered by incrementing the phase shift applied at each of the array radiating elements by an amount of phase which is dependent in part upon the position of the radiating element in the array. Phase increments sufficient to shift the beam position by one coarse step (0.1.degree.) are applied to symmetrically located radiating element pairs, pair by pair, until all elements have been incremented. The beam is thereby caused to move through one coarse step in a number of fine steps equaling the number of pairs of elements in the array. An additional feature of the scanning means is the application of phase increment to the array elements in a pseudo-random sequence.

Abstract: A pressure responsive diaphragm is attached to a substrate carrying a thick film metallic coating covered by a dielectric glass coating so that the diaphragm and thick film coating comprise a pressure variable capacitor. Changes in pressure difference across the diaphragm force the diaphragm to roll against the glass to vary the area of diaphragm in contact with the glass, thus changing the capacity.