Abstract: A circuit for reducing the distortion in an FM quadrature demodulator. A non-linear circuit stage is connected after the quadrature demodulator, whose characteristic has an inverse curve form like the demodulator characteristic. If the FM quadrature demodulator uses a resonant circuit to generate a frequency-dependent phase shift and has two outputs in phase opposition, the non-linear circuit stage can be formed by two diode branches through which the output currents of the quadrature demodulator flow. The voltage difference at these two diode branches supplies the output signal with the non-linear distortions largely removed.

Abstract: A solid state oscillator circuit for operation at very high frequencies includes a field effect transistor having an input network connected between its gate and source electrodes and an output network connected between its drain and source electrodes, the input and output networks each including three discrete capacitors connected in a "pi" configuration, the input and output networks being connected in series with one another, and an inductor being connected in parallel with the series connected networks, the equivalent circuit impedance of the networks in series and the inductance determining the operating frequency of the oscillator circuit, and the relative ratio of impedance of the networks determining the amount of oscillator feedback.

Abstract: A projection exposure apparatus for projecting, onto a semiconductor wafer through a projection lens, an integrated circuit pattern formed on a mask or reticle. An alignment beam having a wavelength different from that for the exposure is used to achieve alignment between the mask and the wafer. A parallel flat plate is detachably disposed between the projection lens and the mask and/or the wafer to prevent a magnification error and/or a focus error of the projection lens which would otherwise be caused upon alignment due to the difference in wavelength.

Abstract: In a demodulator circuit for processing a frequency-modulated (fm) signal, two rectangular-wave signals of opposite phase are generated from the fm signal and separately processed in two similar circuit paths. Each circuit path includes an inverter that receives one of the rectangular-wave signals and a NOR gate that receives both the rectangular-wave signal and its inverted version from the inverter. By imparting a slight delay on positive-going transitions of the inverted signal, a pulse stream is produced by the NOR gate in coincidence with such transitions. The pulse streams from both paths are combined to obtain a resultant signal having a pulse repetition rate that is twice the frequency of the fm carrier. Temperature-caused pulse variations in one circuit path relative to the other . . . which will allow the fundamental carrier frequecy to reappear . . . are stabilized by having the inverters, and the NOR gates, in thermally-coupled packages.

Abstract: There is provided an indirect frequency synthesizer in the millimeter wave frequency range of 36 to 38.6 GHz. The synthesizer comprises a high performance frequency translation loop for operation in the microwave frequency range and contains a voltage-controlled oscillator, an automatic loop gain correction system and a sophisticated lock search system. The frequency translation loop is operable under a variety of conditions (temperature etc.) and overcomes the considerable difficulties which exist in this frequency range such as maintenance of constant optimum loop parameters, thus making it possible to utilize the entire frequency tuning range of the millimeter wave oscillator. As a result, the synthesizer has very satisfactory characteristics as regards noise and spurious frequencies products.

Abstract: A tracking phase locked loop circuit in which the frequency of an oscillator portion thereof is varied over a range of frequencies in search of an incoming carrier is disclosed. The varying frequency occurs at two different sweep rates. A faster rate is used until the frequency of the phase locked loop's oscillator nears the frequency of the incoming carrier, and a slower rate is used until the circuit locks onto the carrier. A filter couples between mixer and sweep control circuit portions of the phase locked loop to provide information concerning the difference between oscillator frequency and incoming carrier frequency. The sweep control circuit distinguishes between the carrier and noise and switches rates accordingly.

Abstract: A microwave cavity oscillator comprises a waveguide blocked at both ends, an active device enclosed in the waveguide and a dielectric powder or other fluid filling the remaining space in the waveguide. The microwave cavity oscillator is useful, for example, as in a discontinuity detector system.

Abstract: A variable frequency oscillator includes a RAM which stores a frequency setting data and provides a frequency control data, a VCO circuit which provides an oscillation output having a frequency which is defined by the contents of the frequency control data, a reference oscillator which provides a reference signal having a given frequency and phase, a phase comparator which detects the phase difference between the reference signal and a comparison signal corresponding to the oscillation output, and a logic circuit which combines the frequency control data with a phase data and provides the frequency setting data. The phase comparator provides the phase data whose contents indicate +1 if the phase of the comparison signal is delayed from the phase of the reference signal, indicate -1 if the phase of the comparison signal is advanced to the phase of the reference signal, and indicate 0 if the phase of the comparison signal matches with the phase of the reference signal.

Abstract: A portable low-output-level generator producing simultaneous audio, ultrasonic and RF noise for the test and demonstration of instruments designed to locate electrical interference, for demonstration of the broad frequency spectrum of electrical noise radiation, for antenna tests, to test the EMI susceptibility of electronic equipment, and to illustrate the effects of said noise on TV and radio receivers. This generator is enclosed in a housing and communicates audio and ultrasonic sounds to the observer via a vibrating diaphragm mounted on the face of the housing, with means provided to attenuate the audio sounds relative to the ultrasonic, and this generator radiates RF from a retractable antenna mounted on and extending outward from the housing.

Abstract: A phase synchronization circuit of a phase lock loop having a phase comparator, a loop filter or a low-pass filter and a voltage controlled oscillator controlled by output of said loop filter has been improved by a phase comparator having the hysterisis characteristics in which one of a pair of output levels is provided for each input phase difference according to phase error direction, except in the vicinity of a stable point of phase.

Abstract: An optical system transmits and reflects a laser beam along a common optical path between a laser generator and the target area on a workpiece. Illuminating light is transmitted along a portion of the optical path to the workpiece and is reflected therefrom to form an image of the target area projected onto a display screen. The reflected laser beam is focused at a detection point to monitor etch rate while the illuminating light is reflected adjacent thereto from the optical path to provide a visual indication of the laser beam locations on the workpiece corresponding to the image being simultaneously displayed.

Abstract: An electronic dither compensator for a ring laser gyroscope uses a velocity pickoff to eliminate the need for a differentiator following a displacement pick off in order to get a rate signal. The dither pickoff is converted, in a voltage to frequency converter, to a pulse train which is synchronized with the pulse train of the uncompensated input from the gyro detector. An automatic gain control with an amplitude control loop is provided. The pulses from the voltage-to-frequency converter and uncompensated inputs are synchronized and summed and differenced as selected by means of logic to produce gyro output pulses free from the effects of dither rate.

Abstract: A temperature-compensated oscillator avoids noise heretofore caused by unduly high signal level changes of a control voltage resulting from sensed temperature changes. This is done by reducing the high level changes into a plurality of relatively low level changes which produce a cumulative effect comparable to the high level effect. The many low level changes do not produce reactions which are abrupt enough to cause noise, especially a phase modulation or frequency modulation noise.

Abstract: An apparatus and method is disclosed that provides a random data generator that is less susceptible to error sources resulting from negative feedback biasing. This invention utilizes a shift register and a multiplexer, controlled by the shift register, to provide the feedback to an amplifier. This improves the correlation between the present data output bit and the following bit.

Abstract: The interior of a metal housing is divided by a dielectric substrate into two compartments. At least one of the compartments is kept air-tight. The substrate carries thereon a semiconductor active element chip for oscillation within the air-tight compartment and a dielectric resonator within the other compartment. The chip and the resonator, electromagnetically coupled with the chip, constitute a microwave oscillator whose oscillation frequency can be stabilized. A metal screw is threaded into that wall of the housing which defines the other compartment in a predetermined positional relationship to the resonator. The metal screw is rotatable to vary the distance between the screw and the resonator and, thereby, the oscillation frequency.

Abstract: Disclosed is a circuit providing a controllable effective resistance which comprises of transistor means that provides current at an input node responsive to an input voltage at the input node. The transistor means is coupled to a settable current source which operates to control the effective value of the controllable effective resistance. The invention also includes a filter which employs the controllable effective resistance to vary the breakpoint frequency of the filter. Also, a phase-locked loop apparatus employing the filter is disclosed.

Abstract: A quadrature detector circuit for demodulating frequency modulated information is provided that is particularly designed for use in television receive only (TVRO) satellite communication video receivers. The bandwidth restrictions of conventional quadrature detector circuits are eliminated by substituting a simple ferrite bead for the usual parallel capacitor, inductor, resistor combination heretofore required in quadrature detectors. The quadrature detector hereof produces a higher level of video output, improved linearity, and better selectivity, as compared to conventional quadrature detector circuits. Moreover, the quadrature detector hereof reduces circuit complexity, and decreases material costs and production time.

Abstract: A frequency modulation detection arrangement comprises an FM detector and an injection-locked frequency divider arranged for receiving a radio signal and for providing a frequency divided radio signal in response thereto. The FM detector is coupled with the injection-locked frequency divider for receiving the frequency divided radio signal therefrom and for producing a signal indicative of the information content of the modulating wave of the radio signal.

Abstract: A crystal oscillator circuit that is temperature compensated over a broad temperature range has a crystal oscillator, a reactance compensation circuit for providing temperature compensation at low temperatures, and a control voltage-generating circuit for providing temperature compensation at high temperatures. The reactance compensation circuit includes the parallel combination of a thermistor and a variable-capacitance diode, and this parallel combination is connected in series with the crystal oscillator. The control voltage-generating circuit includes a thermistor and transistors and applies a voltage corresponding to the ambient temperature to the variable-capacitance diode of the reactance compensation circuit.

Abstract: A receiver for receiving and demodulating FSK modulated data signals has improved sensitivity over substantial frequency offsets between the transmitter and receiver local oscillator, and low spurious electromagnetic radiation. A quadrature coupler splits the received signal into in-phase and quadrature phase signals which are then mixed down to baseband, filtered, and limited. An RC circuit at the output of a four flip flop demodulator averages the flip flop output signals. A voltage comparator outputs a logical 1 if the voltage at the output of the RC averaging circuit is greater than one-half the supply voltage; otherwise the comparator outputs a logical zero.