Abstract: A two stage transmission notch filter characteristic is achieved with one stage of microwave circuitry. Elimination of the second stage is accomplished by reflecting the microwave power back through a single stage device. Structurally, the adjacent ports of two 3 dB directional couplers are directly connected by delay lines of unequal delay times. The opposite adjacent ports of one coupler comprise the device input and output while the opposite adjacent ports of the other coupler are terminated in a manner that reflects microwave power back through the device. A phase shifter is inserted into one delay line for tuning and a non-reciprocal phase element is used to prevent reflected signals from emerging from the input port.

Abstract: Noise induced hunting is eliminated in successive ranged digital/analog converter bias correction circuits by means of a digital hysteresis circuit. The digital hysteresis circuit comprehends a first up/down counter that counts to its extremums from a pre-set intermediate state in response to enable and up/down input signals. For each extremum count an enable output pulse and a reset pulse is generated at the counter output. The enable output pulses are counted by a second up/down counter the output of which drives a digital/analog converter. Each reset pulse resets the first up/down counter to its pre-set state.

Abstract: Increased bandwidth in a waveguide lens antenna is achieved by altering the geometry of the stepped antenna guide plates in a manner that causes the net contribution of the antenna phase dispersion sources to result in zero average aperture phase error. Design equations are included for the fabrication of waveguide lens antenna having any desired degree of phase compensation. In principle, the plate geometry is configured to effect a given relationship between the components of phase error due to guide plate dispersion and the component of phase error due to the guide plate steps. When these components are equal and opposite zero average aperture phase error (maximum bandwidth operation) is achieved.

Abstract: An automatic bias adjustment circuit for a successive ranged analog/digital converter (SRADC) that eliminates the need for manual bias adjustments and calibration inputs. The bias correction circuit comprehends dual flip flops that are triggered by selected comparators of the SRADC n bit parallel analog/digital converter. The flip flop output signals control up/down counters whose output bits drive digital/analog converter. The digital/analog converted signals are introduced back into the SRADC analog chain to zero bias errors in a particular sub-range. A disabling circuit prevents operation of the bias adjustment circuits for the first sub-range.

Abstract: High levels of R.F. power are controlled and switched by means of a hybrid switching network that employs an intermediate power level switch matrix in conjunction with a pair of 8.34 (nominal) directional couplers and a phasing network. The two directional couplers are connected in tandem by two equal length transmission lines to form a broadband quadrature 3dB hybrid. Switching is accomplished by selectively inserting a 180.degree. phase shift means into the lower power carrying transmission line. The phase shifting means can be a length of transmission line, a solid state device, or a Schiffman type phase shifter.

Abstract: A single blade proximity probe uses fiber optics to direct a laser output at turbine engine blades and to return the reflected light to an image intensifier probe which provides an output indicative of blade clearance. To enable the system to measure the clearance of a single blade tip on an operating turbine, a second light beam having a different wavelength from the laser output is directed over the laser light path to count the blades and to strobe the laser on the desired blade.

Abstract: Index of refraction measurements are made by means of an optical device in which a coherent light beam is divided into an object beam and a reference beam, each of which is directed through a separate path in a common light transmitting medium. The object beam is also transmitted en route through a test volume that accommodates a substance to be tested. It is subsequently recombined with the reference beam to form a single output beam. The output beam is received by a photo detector and its intensity is measured. The intensity of the detected output beam is related to any phase shift between the object and reference beams. The phase shift in turn is a measure of the index of refraction of the test substance. Information relating to density, temperature and pressure of the test substance can be derived from measured index of refraction values by using conventional conversion formulas.

Abstract: Multiple interference signals in an electromagnetic wave communication system are individually discriminated against by a beamport sidelobe canceller comprising a multichannel auxiliary system in which spatial filtering of the angular sectors of interest is performed prior to sidelobe cancellation. Each spatial filter of the auxiliary system has its own adaptive control and only those interfering signals appearing in its assigned sector are operated on by that loop. The output of the main communication system receiver is summed with the outputs of the auxiliary system channels to produce a system output and an adaptive control loop feedback signal. The feedback signal initiates the generation of a cancellation signal in any adaptive control loop in which correlation of interference signals occur in both the main communication system received signal and the signal received by the auxiliary system channel to which that loop is connected.

Abstract: A tracking radar error signal that is independent of pulse to pulse variations of amplitude of the received signal is derived by combining separately detected sum signal energy and difference signal energy in a manner that provides composite error signal pulses that are one-half sum signal energy and one-half sum plus difference signal energy. The pulse composition is realized by means of an RF switch that interrupts the difference signal during approximately one-half of each pulse period. The composite error signal is detected by an IF logarithmic detector and subsequently processed by two parallel box car generators. One box car generator is gated to process sum signal energy and the other is gated to process sum plus difference signal energy. The tracking error signal is obtained from a single pulse by feeding the outputs of the two box car generators to a differential amplifier and obtaining the difference voltage at its output.

Abstract: A waveguide lens having improved efficiency and bandwidth characteristics is realized by appropriately combining the waveguide element array configuration of a conventional zoned waveguide lens with the phase shifting means of a constant thickness variable phase shift type waveguide lens. The length of each waveguide element and the phase shift required of its phase shifting means are functions of the waveguide elements radial distance from the lens axis. Design equations for determining waveguide element length and phase shift values are developed using both single and double frequency design procedures.

Abstract: Passband distortion due to mass loading in withdrawal weighted surface acoustic wave transducers is substantially reduced by a thinning technique in which interdigital transducer electrodes are selectively withdrawn to synthesize a response function H.sub.o '(N). H.sub.o '(N) is a modified response function that has been scaled from a desired response function H.sub.o (N) by a thinning factor THIN. THIN is a positive, non-zero constant with a maximum value of unity. Thinned withdrawal weighted transducers fabricated in accordance with the technique have electrode weights that are normalized to less than unity and achieve mass loading reduction with a minimum amount of degradation of the desired response function.

Abstract: A portable multiband H.F. antenna that has minimum ground area requirements and that is capable of transmitting electromagnetic wave radiation with horizontal polarization, azimuth plane omnidirectional patterns and a null in the vertical beam pattern is realized by means of an easily erectable tower type radiator. The tower structure has adjacent conductive leg members that define an elongated antenna slot aperture the total length of which is resonant to the lowest operating frequency band. A microwave transmission line resides along one side of the slot and the slot aperture is fed by shorting the transmission line to the oposite side of the slot. Operation at higher frequency bands is achieved by shorting out sections of the slot aperture on both sides of the feed. An array of radiating slot apertures can be provided by shorting the full slot aperture into sections and feeding each slot section separately.

Abstract: Extremely sensitive velocity and position measurements are achieved with a surface acoustic wave (SAW) resonator device. A surface acoustic standing wave field is established on a movable SAW propagation surface by means of induced SAW pulses traveling on the propagation surface and their reflection from a SAW reflecting mechanism. Movement of the propagation surface causes periodic variations in the standing wave field amplitude. The frequency of the standing wave field amplitude variation is directly related to the SAW propagation surface velocity and its phase (i.e., total number of standing wave field amplitude variations from a reference point) indicates the SAW propagation surface position or how far it has moved from the reference point.One implementation comprises a rotatable aluminum cylinder on the surface of which SAWs are launched and detected by proximate but non-contacting transmitting and receiving electromagnetic transducers (EMTs).

Abstract: The generation of intense burst of high energy electrons and/or intense currents of positive ions is accomplished by compressing a magnetic field in the presence of a gas plasma. The gas plasma is contained in a metallic cylinder and the magnetic field is established by means of a capacitor bank driven current that flows in the axial direction on the metallic cylinder and returns through the gas plasma contained in the cylinder. Detonation of explosive material surrounding the metallic cylinder drives the cylinder walls inward effecting compression of the magnetic field and a concomitant increase in plasma current.

Abstract: Radar target back scattering is controlled by an impedance loading technique. The target is loaded with a variable impedance that is adjusted in response to the frequency of any incident radar signal to achieve optimum reflectivity for that particular frequency. Either radar target cross section reduction or enhancement is achieved over a broad band of frequencies by appropriate control of a voltage variable capacitance diode.

Abstract: Shielding from and the termination of high power infrared laser beams is accomplished by interception of the beam by one of two spaced, juxtaposed, ceramic sheet members. The beam intercepting member has a thickness to beam power density relationship that allows opaque to translucent conversion of the portion thereof illuminated by the beam. The translucent portion subsequently diffuses the beam. The diffused beam is then absorbed by the second ceramic sheet member.

Abstract: Doubly rotated propagation surface defining cuts of single crystal berlinite (AIPO.sub.4) are utilized to provide temperature compensated surface acoustic wave (SAW) substrates having high piezoelectric coupling factors and low diffraction losses. A preferred embodiment of the invention comprises a berlinite substrate member having a propagation surface that substantially coincides with a plane defined by Euler angles Lambda = 76.8.degree., mu = 90.0.degree., and Theta = 11.5.degree.. An alternative embodiment utilizes a propagation surface that substantially coincides with a plane defined by Euler angles Lambda = 79.7.degree., mu = 90.0.degree., and Theta = 15.5.degree..

Abstract: A singly rotated propagation surface defining cut of single crystal berlinite (AIPO.sub.4) is utilized to provide a temperature compensated surface acoustic wave (SAW) substrate having a high piezoelectric coupling factor. The preferred embodiment of the invention comprises a berlinite substrate member having a propagation surface that substantially coincides with a plane defined by Euler angles Lambda = 0.0.degree., mu = 80.4.degree., and Theta = 0.0.degree..

Abstract: MNOS memory circuit fabrication problems that result in leakage, memory device depletion mode switching and leakage paths at the edges of silicon islands are eliminated by a production process in which deposited and thermal oxides are used as a diffusion mask on the island edges, selective control of the threshold level of the memory device is achieved by ion implantation, and a thick oxide is grown on the silicon island edges to control charge injection.

Abstract: A low inductance, rapid response, heater for silicon photodetector and microcircuit applications is realized by depositing on a substrate surface a heater whose contact terminals and resistance element are configured to eliminate electrical noise due to the induced currents that commonly result from on-off switching action. The heater geometry utilizes a concentric ring configuration and consists of an inner disc-shaped contact terminal, a ring-shaped resistive heater element surrounding the disc-shaped contact terminal and an outer peripheral contact terminal surrounding the heater element. The heater is operated by means of an electrical current flowing in a radial direction through the circuit comprising the outer peripheral contact terminal, the annular resistive heater element and the inner contact terminal.