Abstract: This circuit compensates for phase variation introduced by the delay element in a PSK (phase shift keyed) demodulator. The signal to be demodulated is split. One portion is delayed while the other portion is fed to a variable phase shifter and then to a hybrid splitter. The delayed signal and quadrature output of the hybrid splitter are fed to a phase detector which recovers the information. The delayed signal and inphase output of the hybrid splitter are fed to a phase tracking circuit. This phase tracker controls the variable phase shifter in a manner which maximizes the detected signal by compensating for phase variations introduced by the delay element. The fixed component of difference in phase between the delayed signal and the shifted signal is either a multiple of 180.degree. or an odd multiple of 90.degree. , depending upon the coding system employed.

Abstract: A radiation sensitive detector employed with a thermal radiation scanning system to receive images that are scanned across said detector at predetermined velocities. The detector is sensitive to these scanned images and generates minority photocarriers that drift along the length of the detector in the opposite direction as a majority carrier flow caused by an applied biasing field. The cross-section of the detector is non-uniform along its length direction so that the density and velocity of the photocarrier packets may be appropriately controlled over the length of the detector.

Abstract: A partly analog partly digital bit synchronizer capable of acquisition and operation over an arbitrarily broad range of data rates is disclosed. A second order phase lock loop (PLL) is employed providing both phase and frequency correction to a voltage controlled oscillator (VCO). The phase detector consists of a binary counter whose most significant bit (MSB) is defined to be the recovered clock. The desired data transition points are defined as coinciding with the falling edge of the counter's MSB. At each data transition, the least significant bits within the counter are used to set the duration of phase and frequency correction pulses proportional to the phase error, which pulses are then fed to the VCO. An acquisition circuit diverts the frequency correction pulses in order to sweep the VCO within a selected half octave. Lock is recognized when a preselected number of data transitions with phase error below a preset maximum occur consecutively.

Abstract: A differentially coherent signal detector capable of detecting arbitrary-even-ordered phase shift keyed signals, such as quadraphase (QSK), hex (HSK), octo (OSK), etc. In the case of QSK, the signal to be demodulated is split. One portion is delayed while the other portion is fed to a variable phase shifter and then to a hybrid splitter. The delayed signal and quadrature output of the hybrid splitter are fed to a quadraphase detector which recovers the information. The delayed signal and inphase output of the hybrid splitter are each fed to a phase tracking circuit via frequency doublers. The phase tracker controls the variable phase shifter in a manner which maximizes the detected signal by compensating for phase variations introduced by the delay element.

Abstract: An antenna system is disclosed comprising a lens and a feed array having several substantially identical feed elements. The antenna produces a coverage pattern of transmitted radiation in the form of a shaped beam. The present invention permits the use of a smaller number of feed elements for a given size of the lens' aperture by means of attenuating the sinusoidal ripple that is present in the shaped beam radiation pattern and caused by the size of the feed elements. A plurality of disks is placed in the focal plane of the lens. The disks are selective with respect to one spatial frequency of the emitted radiation (which is at a constant electromagnetic frequency). The disks may be fabricated of a material which reflects the radiation, a material which absorbs the radiation, or a dielectric material of a certain thickness stipulated herein which changes the phase of the radiation by 90.degree.. By this technique, ripples are substantially removed from the beam pattern.

Abstract: Statistical properties of a signal are used to distinguish between a voice signal and an "on hook" indication on a low bandwidth digital data link. Noise is intentionally added to the voice signal to guarantee a minimum power level, while not disrupting normal demodulation. A digital signal, having a known maximum power level upon demodulation, is used to represent the "on hook" condition. Upon demodulation, the minimum power level of the noise-colored voice signal is greater than the maximum power level of the "on-hook" signal, and the two signals can be distinguished by a power level threshold detector. This apparatus and technique is particularly well-suited to under-sampled, such as CVSD (continuously variable slope delta), data links, which are usually noisy and distorted. It alleviates the need for direct access to the digital link and simplifies the required hardware and retrofit modifications.

Abstract: A buffer amplifier is disclosed which has the ability to retain a high voltage from input to output and is capable of coupling to highly capacitive loads. The input impedance can be tailored up to several hundred thousand ohms. The frequency range is from 0.5 Hz to 6 KHz for highly capacitive loads. The amplifier comprises, in combination, an input impedance matching stage and a first and a second amplification stage. The input impedance matching stage consists solely of passive components. The first amplification stage comprises an operational amplifier in series with a high voltage transistor. Circuitry associated with the transistor provides separate controllable AC and DC gains. The AC gain is fed back through a feedback loop to the op amp and does not contribute much to the overall AC gain of the stage, which is determined by two resistors.

Abstract: A tape deck which incorporates a take-up reel rotation sensing switch and associated sensing circuit for enabling the capstan and take-up reel drive mechanism includes a sensing switch which only rotates with the take-up reel when it is driven in the take-up direction. If the take-up reel changes direction, due to tape windup on the capstan, the switch does not rotate and the sensing circuit disables the drive mechanism to prevent excessive tape windup on the capstan.

Abstract: The tracking signals of a monopulse satellite tracking system are optimized by aligning the phases of the azimuth and elevation channels (the "difference" channels) with the reference (or "sum") channel using an autophase controller and a simulated far field source in the near field. The autophase controller monitors the output of the tracking receiver and adjusts phase shifters along the transmission paths of the azimuth and elevation channels, in a manner to maximize the outputs of the receiver. The simulated far field source provides an alignment signal for the autophase controller. The simulated far field source consists of a signal generator, a near field probe, and near field phase compensators. The probe is positioned to avoid any nulls in the simulated tracking signal for the frequencies of interest. The probe is also positioned to limit the range of the phase shifts introduced by near field placement, for the frequencies of interest.

Abstract: The antenna system employs a parabolic reflector fed by an offset feed array of circular wave guides located substantially at the focus of the parabolic reflector, but offset from the axis thereof. A plurality of aperture tuning mechanisms disposed at the mouths of the circular waveguides of the waveguide feed array, and having physical lengths much shorter than one wavelength at the frequencies involved, are provided to reduce cross-polarization and mutual coupling between adjacent feeds. The short resonant length of these tuning mechanisms, and their shape which is chosen to generate the TM.sub.11 mode E-field contour line ensures that they are effective over a broad bandwidth of as much as 20% or more. Within this bandwidth, they act as inductive suppressors to control both cross-polarization and mutual coupling between adjacent feeds.

Abstract: An antenna system is disclosed comprising a paraboloidal reflector and a feed array having several substantially identical feed elements. The antenna produces a coverage pattern of transmitted radiation in the form of a shaped beam. The present invention permits the use of a smaller number of feed elements for a given size of the reflector's aperture by means of attenuating the sinusoidal ripple that is present in the shaped beam radiation pattern and caused by the size of the feed elements. A plurality of disks is placed in the focal plane of the paraboloidal reflector. The disks are selective with respect to one spatial frequency of the emitted radiation (which is at a constant electromagnetic frequency). The disks may be fabricated of a material which reflects the radiation, a material which absorbs the radiation, or a dielectric material of a certain thickness stipulated herein which changes the phase of the radiation by 90.degree..

Abstract: A single microwave-reflective antenna "dish" can be used in combination with a plurality of multiple-beam microwave feed arrays to generate or receive multiple-beam-path microwave radiation in several different frequency bands. Each of the feed arrays may operate in a discrete band of frequencies, with the combined radiations of all the arrays illuminating the reflector along a single axis. The optical system is based on the Newtonian model, such that the radiations from several arrays located off the principal axis may be combined by corresponding frequency-sensitive reflective surfaces located on the principal axis. Each of these reflective surfaces serves to direct the radiations from a single feed array toward the reflective antenna, and reciprocally, to direct radiation from the antenna to the associated feed array.

Abstract: A solar converter is disclosed which has particular applicability at the focal point of a parabolic concentrator. The converter absorbs solar thermal radiation in a cavity type receiver and transports the heat via a secondary fluid to a heat exchanger which contains a primary (i.e., working) fluid used for process heating or to power a heat engine employing either Stirling, Rankine, or Brayton thermodynamic cycles. The secondary fluid is boiled within the receiver by the trapped solar radiation and the released vapor rises along an elevated path to the heat exchanger. The vapor condenses on the surfaces of the heat exchanger, thereby transferring heat to the engine working fluid. The condensed liquid then flows by means of gravity back to the solar receiver. The walls of the cavity receiver are typically comprised of two concentric cylinders joined at one end in a half toroid and at the other end in concentric half spheres.

Abstract: An impedance transforming coupler is disclosed which may be used as a power divider or power combiner at microwave frequencies. The power division or power combination ratio is arbitrary, and the impedance transformation ratio is arbitrary. These couplers may be used in a circuit to power-combine amplifiers. The insertion loss of the circuit is low and the bandwidth is improved by an order of two to one over prior art systems which had separate circuits for matching the impedance and providing power combining. The coupler is optimally a branch line coupler having four curved branches a quarter wavelength long at the center frequency. The output ports are 90.degree. out of phase. Simple formulas are given relating the desired admittances of each of the four branches to k, the desired power coupling ratio, and Y, the desired admittance transformation ratio.

Abstract: This multiplexer and demultiplexer features two transmission lines, one for conveying the data and a second for timing. The timing line controls both the shifting of data in the demultiplexer and the signaling for the beginning and end of data words. Synchronization of the bit shifting clock with the word shifting signal is accomplished by means of phase lock loop circuitry incorporated into the demultiplexer. The disclosed circuit uses low power CMOS design, directly interfaces with contact closure commands, and directly drives relay or lamp type loads. The demultiplexer contains a power-up delay circuit to avoid start-up ambiguities and false data transmission.

Abstract: A high bandwidth transversal filter is described having an input impedance matching network, a tapped delay line, a plurality of weighting amplifiers, a distributed summing circuit, and an output impedance matching network. The delay line is implemented with a transmission line. The input impedance of this transversal filter depends on the inductance and capacitance of the transmission line and the capacitance of the inputs of each of the FET's used as weighting amplifiers. The gates of the FET's provide high impedance low loss taps of the delay line. The weighting is accomplished by either varying the drain current of the FET's or by using capacitive voltage dividers to apportion the tapped signals. The resulting weighted signals are applied to a distributed summing circuit which provides both high bandwidth summing and additional delays. This summer is also implemented with a tapped transmission line.

Abstract: An apparatus for joining a composite material shaft, such as a graphite epoxy or fiber glass driveshaft, to a metal end member is disclosed, wherein said joint is capable of withstanding large ranges of temperature and humidity, can handle high torque and has high resistance to fatigue. The design of parallel grooves on the end of a metallic sleeve concentrically aligned within the shaft is amenable to mass production. The first layer of fibers of the composite material shaft is preferably wound perpendicular to the orientation of the grooves. On the other end of the metallic sleeve is carved a scalloped pattern which facilitates concentric alignment of the sleeve on the tooling mandrel and helps to reduce shear stress between the sleeve and shaft. A method for mass production of shafts with metallic end joints attached employs an elongated spinning mandrel and pre-preg tape wound at high speed.

Abstract: This device generates clock pulses which are synchronized with the bit data rate of an input antipodal bit pattern. The device can be used with multiple input data channels whenever such channels are synchronized, i.e., the periodicity of each channel is the same and the phase relationship between channels is fixed. For example, it can be used with QPSK modulation with two input basebands; or with biphase shift keying, frequency shift keying, or other types of modulation with only one baseband input. The circuit uses a form of delay lock loop which estimates the mean zero crossing instant of the input data stream. It compares the zero crossings with early and late gates which are generated on the basis of prior analysis of the input stream. A multiple transition detector circuit is employed when the operating environment is very noisy to inhibit the counting of multiple zero crossings during a combined early gate/late gate period.

Abstract: Described herein is a microwave radar system which employs heterodyned swept frequency at approximately two millisecond sweep intervals. The power source is a reliable solid state, low power device such as a Gunn diode. The heterodyned difference frequency signals are converted to digital form, transformed into the frequency domain by means of a Fourier power transform, and then averaged by computer processing. Performing the Fourier power transform before averaging enables the processing of quasi-incoherent data whereby signal-to-noise ratio improvement is a function of the square root of the average number of samples taken. High-speed processing is used to off-set the loss of statistical averaging of phase-coherent data which cannot be preserved because of target motion. Thus, the sequence of the power transform allows phase-less averaging over the entire collection period.

Abstract: A mechanism for preventing endless loop type cartridges from entering a cartridge type tape deck when the cartridge is in an orientation other than the single prescribed orientation. The embodiment is a lever mounted in the deck biased towards the insertion path of the cartridge to engage a notch in the side of the cartridge when the cartridge is inserted upside down.