Abstract: The present invention is a liquid crystal display with an improved backlighting system. A light source in the backlighting system radiates light in a first non-preferred direction. An optical apparatus coupled to the light source receives the light radiated by the light source in the first non-preferred direction and refracts it into a first preferred direction.

Abstract: A method for automatically managing the communication channel resources between two nodes having neighboring nodes in a network of transceiver nodes, wherein each node communicates during specific time slots and uses multiple frequencies on a time division multiple access basis includes the steps of storing a table of possible communication frequencies and time slots between nodes; and announcing and transmitting during a specific time slot, a selected transmit frequency and slot from a first node to a second node and all neighboring nodes of the first node. The announced frequency and slot have certain constraints on reuse within two hops of the transmitting node to thereby establish contention free communication on that frequency and slot between the first and second nodes.

Abstract: A system for receiving, correlating and interpreting secured wireless transmissions, periodic or otherwise, including multiplexed receivers, robust correlator design, a state machine device for controlling the receivers and correlation function, and the ability to determine signal spatial diversity via switched antenna signal processing. The correlator is constructed to include a synchronization scheme adaptive to any variety of input signals from the coupled receiver tuned frequencies.

Abstract: A monitor for measuring physical parameters of a slurry, utilizing microwave propagation within a waveguide, either in conduit or a storage facility. Switching circuitry and specially constructed waveguides are provided, which operate in combination to provide rapid, accurate measurement of such parameters as flow rate, and concentration of the slurry.

Abstract: A system for self-calibrating a clock of a communication terminal for use with communication systems in which a central communication node generates time base correction signals for the terminal clock includes a terminal oscillator which generates an oscillator frequency that includes an error amount. An oscillator calibration filter generates a frequency error estimate amount. Circuitry is provided for subtracting the frequency error estimate amount generated by the calibration filter from the oscillator frequency error amount. Circuitry is provided for applying the time base correction signals to the calibration filter to thereby modify the frequency error estimate amount generated by the calibration filter based upon the time base correction signals generated by the communication central node.

Abstract: A composite signal recognizer, separator, and FM demodulator apparatus for processing received radio signals. The receiver utilizes N demodulators to process a received signal, where N is equal to or greater than the number of co-channel signals or perceived interference. Detailed in both cross-coupled and cascaded fashion, the receiver first tracks to a predominant (stronger) signal, and regeneratively improves track on other (weaker) signals by subtracting the predominant signal or the predominant noise portion from the input of further demodulation stages.

Abstract: A method of managing communication on an unstable error-prone channel is disclosed, having particular applicability to transceiver nodes in a high frequency radio network. The method achieves highly reliable, efficient communication through the exchange of headers within control frames in accordance with a selected suite of protocols. An orderly link establishment is achieved by the exchange of headers indicating specific link establishment states of the nodes. One node having message data to transmit to another sends a herald header, and if the data is to be accepted by the other node, it responds with a herald acknowledgment header. The herald conveys parameters of the proposed transmission to the receiving node, permitting the parameters to be varied by the transmitting node for changing channel conditions. The issuance of a herald acknowledgment depends on message priorities exchanged by the nodes, so that higher priority messages can preempt lower priority ones.

Abstract: An apparatus having a distortion cancelling feedback signal that suppresses undesired signal components. One embodiment of the present invention is comprised of a balanced mixer coupled to a common-mode detector, a filter and having a resulting feedback signal that suppresses the common-mode component of the mixer output signal while allowing the differential component of the mixer output signal to pass on to additional processing.

Abstract: A system for actively monitoring and controlling the effective ambient temperature in an application utilizing a fluorescent tube as the source of illumination. The system is the combination of a fluorescent tube, which may be thermally bonded to a reflector plate that is in physical contact with thermal electric cooler units and a heat sink. A temperature sensor in conjunction with drive circuitry and a power source, directs a magnitude and direction of current flow through the thermal electric cooler units thereby controlling the ambient operating temperature of the fluorescent tube.

Abstract: An enhanced differential amplifier circuit includes an injected inverted signal to the differential amplifier. As the AGC amplifier attenuates, the inverted signal becomes increasingly significant in the total gain ratio, thereby extending its operating range. Both a single current source and dual source implementation are disclosed.

Abstract: A start-up and compression technique for transmitting data. A process is provided which utilizes the calculated difference between individual pixel values of subsequent video frames to the current displayed data in order to update. Additionally, techniques are provided for restarting on-going transmissions and for system initialization based on a variations or suspension of the described interframe compression technique.

Abstract: In a skywave communication setting, a number of independent measurement techniques can be employed simultaneously and their results combined to yield a metric representative of the channel quality during a particular reception. This sample can then be combined with previous samples taken using the same frequency (or same frequency hop set in a frequency hopping system) to serve as a basis for selecting the best operating frequencies.

Abstract: A radio receiver in which the received signal is spread and subsequently despread in order to identify unwanted signals. One embodiment of the present invention is comprised of a frequency-hopping spreading synthesizer that operates in synchronization with a despreader synthesizer such that unwanted signals are effectively suppressed based upon different spreading characteristics of the desired and undesired signals. Use of a logic device, in one case a digital signal processor, in combination with a state-level monitor allows for the reconfiguring of the receiver such that a state containing a large interferer can be removed from further signal processing.

Abstract: An electro-magnetic device for use in applications requiring low-profile components. The device includes a magnetic substrate with a scheme of through-holes in association with a first and second winding, plated or wired, integral to the substrate and wound orthogonal to each other. The first winding comprises the AC inductor/transformer permeability. The second winding in association with an applied DC bias current causes the permeability to vary over a wide controlled operating range.

Abstract: A bandwidth-enhanced antenna system for operating on one of a plurality of selected frequency bands includes a whip or wire antenna element having band selection wires and a contiguous set of inductors arranged in series, each of the inductors being sufficiently separated from one another and being arranged such that the resonant frequency of any of said inductors is greater than the highest operating frequency of the plurality of frequency bands. Selector means is included provide a band select signal, and a plurality of switches each having a first terminal connected to a corresponding one of the inductors and a second terminal connected to the feed-end of the antenna element. The switches are responsive to the bandwidth select signal to allow communication using a selected one of the plurality of the frequency bands. An impedance matching network may be used for coupling an external receiver or transmitter to the feed-end of the antenna element.

Abstract: A synthesizer based upon direct-digital frequency synthesizer techniques of simplistic design and minimized spurious signal levels. The output signals of two frequency hopped direct-digital frequency synthesizers are combined with the resultant signal having a greatly suppressed spurious signal level due to the channel spacing variation of the spur. Alternate embodiments concern the number and functional location of digital-to-analog converters, varying the clock signal and the use of high-pass filters.

Abstract: A multiband direction finding antenna comprised of numerous antenna elements, of coplanar location. The antenna elements associated with lower band frequencies are provided with chokes, so that unchoked sections do not exceed one-quarter wavelength of the high-band, highest frequency.

Abstract: An apparatus and a method for cancelling distortion in a direct conversion receiver, such distortion created by the mixing of the desired signal with the output signal of an local oscillator. Subsequent to filtering the mixer output signal, the even mode distortion component is extracted, phase shifted, amplified and recombined with the mixed signal in such manner as to suppress even order distortion.

Abstract: A feedback control loop having a variable attenuator controlled by oscillation detector means and overshoot detector means to better track the input signal. The oscillation detector means utilizes an estimated signal value compared to a subsequent measured value with the absolute difference of the two compared to predetermined threshold values. Should the calculated difference exceed predetermined threshold values, the variable attenuator value is adjusted and the process repeated after a brief disabling period to allow settling.In addition to the oscillation detector, an overshoot detector means may also be used alone or in combination with oscillator detector means to control the variable attenuator setting.

Abstract: An apparatus and method for performing spatial nulling in antenna electronics that provides an integrated solution of signal attenuation and bi-phase modulation. One implementation is comprised of load resistors and field-effect-transistors in a gallium arsenide component configured in such fashion as to provide attenuation and bi-phase capability in response to coupled control signals.