Abstract: The frequency of a local clock in the receiving modem is selected to be one half of the sum of the frequency of the mark tone and the frequency of the space tone. The received tones are converted into digital words and the phase of each sample of a digital word is calculated relative to the modem clock. A predetermined number of the phase calculations are stored and the difference between one phase calculation and another phase calculation is made. The number of samples between the one and another is selected such that the difference calculation results in an approximately +90 degrees if the samples represent a mark tone and approximately -90 degrees if the samples represent a space tone. Thus, the sign of the phase difference calculation is determinative of the tone being received.

Abstract: An adjustable electronic filter apparatus is disclosed comprising a dielectric block having one or more through-holes and having a conformal conductive coating substantially over all outside surfaces as well as each through-hole therein. Each through-hole so plated forms a resonator from a transmission line which includes an open portion, for providing capacitive reactance at a first end, and a short-circuited end as a base, for providing an associated distributed inductance at a second end thereof. A unique method of tuning the adjustable electronic filter, whether a single resonator, a plurality of resonators, or a plurality of intercoupled multi-resonator filters, is disclosed that permits bi-directional tuning for at least one resonator in each of the above exemplary embodiments. By selectively adjusting an inductive portion of the plating at the base of each resonator so tuned, a resonator is quickly and accurately adjusted to a desired frequency.

Abstract: Modems such as type 201 modems are subject to pattern sensitivity problems caused primarily by different group delay characteristics for the patterns. The method of this invention minimizes such problems by determining different clock phase positions for group delayed patterns and uses same when such patterns are being received. A normal clock phase is determined during training and is used when patterns without substantial group delay are being received.

Abstract: A transparent film of material is deposited on a PLZT plate used in a light modulator. The film is substantially less resistive than the PLZT plate and prevents light leakage in the OFF state due to space-charge accumulation. Suitable materials include SiO.sub.2 and TiO.sub.2.

Abstract: The present invention minimizes noise pops due to Rayleigh fades by controlling receiver gain relative to the average received signal strength so that only a predetermined level of limiting occurs prior to the recovery of the audio information. The amount of limiting is selected so that a significant Rayleigh fade will cause the amplified IF signal to drop below the limiting level and enter the linear amplification region. During the fade the magnitude of the signal provided to the discriminator decreases thereby decreasing the discriminator's output and minimizing the magnitude of the audio pop. Additional minimization of the subject noise pops is achieved by utilizing a discriminator which has a square law transfer characteristic so that the recovered audio level will decrease 2 dB for every 1 dB decrease in input signal level.

Abstract: A leadless chip carrier for RF power transistors or the like is disclosed which includes a body of insulating material having two major surfaces and side walls joining the major surfaces. In a first embodiment, a pattern of conductive pads is deposited on one major surface. A pattern of conductive contact areas is deposited on the other major surface and distributed interconnecting portions of conductive material are deposited to connect the pads to the respective contact areas. In a second embodiment, larger pads and contact areas are provided on a beryllia substrate to provide a leadless chip carrier for RF transistors capable of handling 8 watts. In a third embodiment, a single slot is made conductive to provide the distributed interconnecting portion for one terminal, while in a fourth embodiment, the slot is changed to a plurality of small, tungsten-filled through holes to provide a virtually hermetically sealed leadless chip carrier for RF power transistors.

Abstract: A modem receiver circuit comprises one or more phase jitter canceling circuits for reducing sinusoidal components of phase jitter in a telecommunications channel. The receiver circuit automatically tracks multiple sinusoidal frequency components and jitter components varying slowly in amplitude and frequency. Each phase jitter canceling circuit is responsive to a phase angle error signal, which is scaled by an adaptive gain constant and appropriately signed. The corrected error signal is passed through a second order loop filter which contains an accumulator with a jitter frequency estimate. The output is integrated into an estimate of the phase of the sinusoidal jitter, which is converted into an estimate of the jitter angle by using a sine lookup table. The resulting estimated jitter component angle is added to the carrier loop phase angle estimate to derive a total receiver phase estimate. The circuit provides rapid acquisition of an accurate initial estimate for the jitter component.

Abstract: A method and means for filtering the quantization noise from the output of a 1-bit analog-to-digital converter (noise-shaping coder) is disclosed. The A/D utilizes oversampling of the analog input signal, and decimation of the digital output signal. The multiplierless low-pass filter is comprised of a coefficient ROM for storing the filter coefficients, a counter for addressing the memory, and a true/complement gate for selectively complementing the output of the memory in response to the 1-bit data stream from the noise-shaping coder. An accumulator sums the selectively complemented output words for all samples, and the accumulated output is then applied to the decimator. A second embodiment is also disclosed which utilizes an overlapping digital filter approach, wherein a plurality of digital multiplierless filters are overlapped to provide an arbitrary length filter capable of producing an arbitrary filter response.

Abstract: An improved arrangement and method for use in a radio communication system is disclosed which makes possible mobile radio channel assignments on narrower channel spacings with a minimum amount of adjacent channel interference or splatter occurring at an included base station receiver. In a first embodiment, the mobile radios modify at least one transmission parameter, such as maximum allowable deviation, a given amount of transmitter output power, and a modulation limiting bandwidth, if a processed value of receive signal strength exceeds at least one predetermined threshold value. The processed value of receive signal strength is taken from a plurality of sampled and stored receive signal strength values in the mobile radio. By determining that the processed value of receive signal strength exceeds a predetermined threshold value, the mobile radio is able to adaptively control the amount of splatter caused at the base station, thus keeping the amount of splatter within acceptable levels.

Abstract: A memory programming system which provides a method and apparatus for programming and reading an electronic device memory through its power source connections. Circuitry is provided for programming and reading internal EEPROM memory of a portable radio with information provided by an external programming apparatus through its existing battery terminals, wihout removing the EEPROM from the unit, and without the use of supplementary connectors. The radio battery is disabled and a substitute power source is connected to the existing battery terminals, the substitute power signal is encoded with program data by the programming apparatus circuitry and decoded by the radio circuitry, and a programming voltage is applied to the EEPROM such that the program data is programmed into the radio memory through the battery terminals. The program data can be verified by encoding the substitute power signal with verification data in the radio and decoding the signal externally to provide a visual indication for verification.

Abstract: A first layer of titanium or tin is vapor deposited upon opposing major surfaces on the ceramic sensor. A second layer consisting of platinum, palladium or ruthenium is deposited over the first layer. The structure is then preferably annealed in air in order to crystallize the external layer to roughen the exterior surface and enhance adhesion. Lead wires, preferably made of Nichrome, are attached to the opposing surfaces by applying a conductive paste to the wire and surface functions, and firing the structure. The conductive paste provides a relatively low resistance, strong, mechanical bond between the lead wires and the roughened external surfaces of the structure. The first layer facilitates bonding of the second layer to the ceramic. The first and second layers cooperate to protect the ceramic from the potentially harmful glass frit contained in the conductive paste.

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, tin oxide and silicon oxide, and having electrodes operably affixed to the surface thereof.

Abstract: A metal shield is dimensioned to enclose a portion of a portable radio having an internal antenna and a first transmission line. A transmission line mounted in the shield is positioned to be adjacent to the first transmission line when the shield engages the radio and permits energy to be coupled between the resonator and the first transmission line. The first transmission line and the shield are dimensioned so that the electrical length of the first transmission line increases to 2L when the shield engages the radio, where L is the electrical length of the first transmission line when the shield does not engage the radio. This electrical length transformation by an integral multiple of one half wavelength helps to maintain the input impedance to the internal antenna.

Abstract: An improved hands-free user-interactive control and dialing system is disclosed for use with a speech communications device. The control system (400) includes a dynamic noise suppressor (410), a speech recognizer (420) for implementing voice-control, a device controller (430) responsive to the speech recognizer for controlling operating parameters of the speech communications device (450) and for producing status information representing the operating status of the device, and a speech synthesizer (440) for providing reply information to the user as to the speech communications device operating status. In a mobile radiotelephone application, the spectral subtraction noise suppressor (414) is configured to improve the performance of the speech recognizer (424), the voice quality of the transmitted audio (417), and the audio switching operation of the vehicular speakerphone (460).

Abstract: A retractable antenna assembly is disclosed for tuning an antenna having a helical section to frequency by selectively positioning an appropriate tuning core within the helix. The antenna frequency can either be raised or lowered through the use of conductive or permeable tuning core compositions. The core positioning mechanism is implemented by affixing the tuning core to a portion of the antenna supporting rod slideably located within the helix. This helical antenna/tuning core configuration is readily adaptable to miniature portable radios by providing a helical antenna assembly which is retractable within the radio housing in the receive-only or standby mode, and which is outwardly extendible from the radio housing for use in the active transmit/receive mode. A unique barrel-cam latching mechanism is also described.

Abstract: An improved antenna configuration is disclosed for a fully duplex portable radiotelephone that is normally operated in the nearly horizontal position next to the user's ear and mouth. A notch antenna is provided in the bottom portion of the portable radio transceiver parallel to the major longitudinal axis of the housing. The notch aperture is cut in the conductive radio housing at a transverse angle to the major face plane of the radiotelephone to form a notch antenna which radiates predominately vertically polarized E-field waves when the transceiver is positioned such that the major longitudinal axis of the radio is approximately 30 degrees to the horizontal. The notch is an effective quarter-wavelength long and is dual-fed from a pair of coaxial cable transmission lines near the shorted end of the notch.

Abstract: An electronic apparatus comprises a housing having walls of an electrically conductive material and together defining an inner space. The walls of the housing comprise outer walls, and partition walls extending from one of the walls of the housing into the inner space of the housing dividing the inner space into different compartments. The apparatus further comprises an electronic circuit board having electronic components mounted thereon and is provided with apertures through which the partition walls extend. In order to shield the electronic circuits of the individual compartments in relation to each other a first shielding component is provided.

Abstract: An improved switched capacitor circuit configuration is disclosed which exhibits improved low voltage supply operation and improved charge injection cancellation performance. In the preferred embodiment of a switched capacitor integrator, the improvement is realized by the particular configuration of a switched tub switch on the input, single N-channel devices at the summing junction, skewing the analog ground V.sub.AG downward, and delaying the clock signals to turn off the switches at the summing junction before the charge injection of the switched tub switch is realized.

Abstract: A differential input circuit for a switched capacitor CMOS voltage comparator is provided which minimizes offset voltages by configuring the load devices to utilize a single switched capacitor biasing network initialized from internally-generated bias voltages, while configuring the initialization switches for the differential input devices to also utilize internally-generated bias voltages such that the offset voltages are stored on the input capacitors. The power supply rejection performance of the voltage comparator is also optimized by connecting parallel load devices of opposite switching topology such that the same input impedance is seen at both load terminals.

Abstract: A CMOS data clock oscillator circuit is disclosed which provides a simple, inexpensive, high-specification oscillator with an accurate duty cycle. The data clock oscillator 100 includes an oscillator stage 121 providing an AC output signal having an average DC value determined by an applied bias voltage, a limiting stage 124 having MOSFETs 102 and 103 configured to form a back-to-back limiter network to limit the amplitude of the AC output signal, a CMOS biasing stage 122 including complementary MOSFETs 104 and 105 configured to form an active resistor voltage divider network providing the bias voltage for the oscillator stage, and a CMOS buffer stage 123 including complementary MOSFETs 106 and 107 configured to form an inverting amplifier network having a predefined input switching threshold. Buffer stage MOSFETs 106 and 107 have conduction types, geometries, and device parameters matched to those of bias stage MOSFETs 104 and 105, respectively.