Abstract: A device for monitoring humidity as a function of electrical resistance comprises a humidity-sensitive resistor formed of a ceramic including lanthanum chromite, with or without a dopant selected from titanium oxide, silicon oxide and tin oxide, and having electrodes operably affixed to the surface thereof.

Abstract: This dual input antenna system has a first input which provides an impedance match over a first range of frequencies and a second input which provides an impedance match over a second range of frequencies. This effectively enables a narrow band antenna to operate and provide a matched condition at two separate frequency ranges. First and second longitudinal radiating elements are connected at respective ends by an approximate 1/2 wavelength transmission line. The other end of each radiating element is connected by transmission lines to a receive filter and transmit filter, respectively. The receive and transmit filters provide a substantial reactance outside of the respective passbands. The wavelengths of the first and second transmission lines are selected to transform the reactance of each filter into a value which will provide a match condition for the other transmission line at the respective frequency ranges.

Abstract: The invention provides a clock recovery circuit for deriving a recovered clock signal from the band limited multi-level digital signal. The multi-level digital signal is compared with a number of reference levels in a bank of comparators whose outputs are combined to provide a marking signal indicative of threshold crossings by the multi-level signal. The marking signal consists of groups of transition markers separated by eye intervals. A signal source provides clock pulses and window pulses with the window pulses being synchronized with the eye intervals to provide a recovered clock signal.The invention may be implemented entirely in digital form and is particularly suitable for use in partial response signalling in which band limited multi-level digital signals are transmitted without additional clock signals. Performance may be further enhanced by utilizing a smoothing phase locked loop to provide a smoothed clock signal.

Abstract: A device for monitoring temperature as a function of electrical resistivity comprises a sensing element formed of a ceramic including lanthanum chromite with a dopant selected from magnesium oxide, aluminum oxide, titanium oxide and silicon oxide, and having electrodes operably affixed to the surface thereof.

Abstract: An improved method and apparatus is disclosed for perpendicularly mounting an AT-strip resonator on its longitudinal edge. The crystal blank is secured to the base at two or more mounting points via conductive cement which provides both electrical connection and mechanical support. A mounting cavity or slot permits proper positioning and self-fixturing during manufacture. The edge-mounting configuration promotes ease of manufacture, improved shock performance, minimized motional resistance degradation, and high packing density.

Abstract: A piezoelectric device package consists of a base and a cover which are sealed together to hermetically seal a piezoelectric device such as a quartz crystal therebetween. A recess in the cover receives the quartz crystal. Feedthrough holes in the base, or the cover, or both, which have electrostatic seals formed over them provide a means for making electrical connections with the quartz wafer while still maintaining the hermetic seal.

Abstract: An improved electrooptic ceramic reflective display is depicted utilizing polished plates of PLZT ceramic materials in a specific arrangement of dual polarizers, PLZT plate, dual transparent electrode patterns deposited on each major surface in precise alignment of the PLZT plate, and a reflecting surface. The display achieves an optimum effect of high contrast of the associated characters, good brightness, wide viewing angle, and minimum operating voltage requirements. When no voltage is applied, the display has a uniform brightness with no characters shown. When a segment, character, or group of characters is activated by applying a selective voltage, a transverse electrooptic effect is electrically induced and a dark character on a light background is depicted. An elastomer Zebra type connector bar is slit and is utilized to facilitate the electrical connections to the top and bottom electrode pads of the PLZT plate as well as to the associated circuitry for the assembled display.

Abstract: In a delta modulator/demodulator incorporating continuously variable slope circuitry (8, 9, 10), the current passed to an integrator (3) to increase its gain, is squared by a squaring circuit (13) in order to increase the sensitivity of the modulator/demodulator to fast rising and falling waveforms and high frequencies.

Abstract: A helmholtz resonator is driven by a piezoelectric element and is suited for mounting to a printed circuit board. The resonator includes a resonant chamber defined by bottom, top, and side walls, and at least two ports that provide access to the chamber. The ports are contiguous to the bottom and side walls so that any liquid entering the chamber during the printed circuit board cleaning process can exit via the ports. This arrangement overcomes the contamination problem existing in prior art resonators having a single port.

Abstract: An automatic gain selector is disclosed for use with a noise suppression system which performs speech quality enhancement upon a noisy speech signal available at the input to generate a noise-suppressed speech signal at the output by spectral gain modification. The channel gain controller (240) of the present invention produces a modification signal (245), comprised of individual channel gain values, for application to a channel gain modifier (250). A particular gain table set is automatically selected from one of a plurality of gain tables (450) by a selector switch (470) and a noise level quantizer (440) in response to a multi-channel noise parameter, such as the overall average background noise level of the input signal. Then the individual channel gain values (455) are obtained from the particular gain table set in response to the individual channel signal-to-noise ratio estimate (235).

Abstract: An improved background noise estimator (320) is disclosed for use with a noise suppression system (300) for generating an estimate of the background noise power spectral density provided to noise suppressor (310), which performs speech quality enhancement upon the pre-processed speech-plus-noise signal available at the input to generate a clean post-processed speech signal at the output. Background noise estimator (320) utilizes an energy valley detector based upon post-processed speech to perform the speech/noise classification, and a noise spectral estimator based upon pre-processed speech to generate an estimate of the background noise power spectral density. As a result, the background noise estimate supplied to the noise suppressor is a more accurate measurement of the background noise energy, since it is performed during a more accurate determination of the occurrences of pauses in the speech.

Abstract: An electrooptic color display for displaying selectable indicia includes a ferroelectric ceramic element, such as a PLZT material, first and second polarizers on each side of the element, and a mechanism for selectively inducing a transverse electric field at selectable areas on the element, said areas corresponding to the indicia. The electric field can be produced by applying a voltage to transparent interleaved electrodes on one or both surfaces of the ceramic element. These areas produce spectrally selective phase retardation which causes the color of the indicia to be different from that of the background color. Preferably a separate retardation element which may be fixed, variable, or a combination of both, is disposed between the polarizers to provide a fixed color bias that determines the background color. This invention contemplates transmissive, reflective, and transflective color displays.

Abstract: The communications system may include wireless two-way communications equipment having selectable functions and various operational features. Control modules each include mechanisms for providing indicia representative of the status of the features of the communications equipment and mechanisms for generating data for controlling the functions to be selected on the communications equipment. A group of the control modules are coupled to a panel module which selectively communicates with each of the control modules in the group. An interface circuit is coupled to a plurality of the panel modules for selectively communicating with each; the interface circuit includes a microprocessor for writing indicia data to each of the selected control modules via the selected panel module and reads the control data generated by the control modules. The periodic scanning and reading of information is utilized to ascertain changes in the data.

Abstract: An improved noise suppression system (400) is disclosed which performs speech quality enhancement upon speech-plus-noise signal available at the input (205) to generate a clean speech signal at the output (265) by spectral gain modification. The noise suppression system of the present invention includes a background noise estimator (420) which generates and stores an estimate of the background noise power spectral density based upon pre-processed speech (215), as determined by the detected minima of the post-processed speech energy level. This post-processed speech (255) may be obtained directly from the output of the noise suppression system, or may be simulated by multiplying the pre-processed speech energy (225) by the channel gain values of the modification signal (245). This technique of implementing post-processed signal to generate the background noise estimate (325) provides a more accurate measurement of the background noise energy since it is based upon much cleaner speech signal.

Abstract: An embodiment of the invention includes a binary linear phase response filter having a plurality of weighted outputs and a summing circuit which sums groups of the weighted outputs. A polarity inverting mechanism is provided for selectively changing the polarity of the summed outputs from the summing circuit means. An encoding circuit controls the polarity selection in accordance with the logic rule for converting non-return to zero (NRZ) data into return to zero data. Another summing circuit sums the outputs of the polarity inverting mechanism and provides a filtered multilevel data output.

Abstract: A improved microwave dielectric oscillator module which is provided with a removable temperature compensated dielectric resonator channel element is described. The removable temperature compensated dielectric resonator channel element cooperates with an electrically shielded housing. A substrate is mounted within the housing. Microstrip or stripline conductive patterns deposited on the substrate couple energy from the removable dielectric resonator to the remainder of the oscillator circuitry. The oscillator achieves wideband operation utilizing a GaAs FET transistor as the oscillators active element in conjunction with an intergral trombone-line phase adjuster.

Abstract: An improved ceramic stripline filter assembly is disclosed which provides optimized performance characteristics by careful control of the gap thickness between the filter halves during the assembly process. The filter arrangement utilizes paddle leads which include central cavities or pocket holes to accept any excess solder during filter assemblage. Close tolerances are thereby obtained regarding the referenced gap thicknesses from filter to filter.The method of fabricating the stripline filter assembly contemplates the use of a leadframe with the leads extending laterally from a unitary support structure. The leads are then cut or otherwise separated from this integral support after attachment of the leads to the filter body connection points. They may be pre-formed to any predetermined pattern after such separation.

Abstract: An AFC circuit may include an oscillator having an output frequency responsive to a derived error signal, a mixer for mixing a received signal with the output of the oscillator to produce an intermediate frequency, and a signal recovery detector for recovering the information carried by the intermediate frequency. An integral loop filter and compensation circuit receives the recovered signal from the detector, provides a compensated recovery signal which is independent of the closed loop frequency response of the AFC circuit, and provides an error signal which controls the oscillator.

Abstract: A double-sided flexible electronic circuit module is provided having a flexible printed circuit board. The flexible circuit board has a plurality of conductive paths on each surface and a plurality of conductively plated-through apertures being connected to the conductive paths. One side of the flexible circuit board is adapted to carry components with leads; the other side of the flexible circuit board is adapted to receive components without leads. A carrier member, larger than the flexible circuit board and of a size and shape sufficient to accommodate the placement of at least one flexible circuit board, is also provided. The carrier member has a plurality of apertures which are in alignment with the apertures of the flexible circuit board, and a plurality of elongated slots in predetermined positions which extend the entire width of the flexible circuit board which is temporarily affixed onto the carrier member.

Abstract: A modulated elongate cavity oscillator with minimized modulation nonlinearities includes a first cavity having dimensions which determine the fundamental resonant frequency of the oscillator, a gain element disposed in said first cavity that provides amplification to sustain oscillation, and a varactor diode disposed in said first cavity for modulating the fundamental frequency. A first waveguide is coupled to the first cavity for absorbing modes higher than the mode of the fundamental frequency which have an electric field maxima concurrent with the longitudinal center line of the first cavity. A second waveguide is coupled to the first cavity for absorbing modes higher than the mode of fundamental frequency which have an electric field minima concurrent with the longitudinal center line of the first cavity, whereby the first and second waveguides provide effective attenuation of higher order modes such that modulation nonlinearities due to the existence of higher order modes are substantially eliminated.