Abstract: An improved excitation vector generation and search technique (FIG. 1) is described for a code-excited linear prediction (CELP) speech coder (100) using a codebook of excitation code vectors. A set of M basis vectors V.sub.m (n) are used along with the excitation signal codewords (i) to generate the codebook of excitation vectors u.sub.i (n) according to a "vector sum" technique (120) of converting the selector codewords into a plurality of interim data signals, multiplying the set of M basis vectors by the interim data signals, and summing the resultant vectors to produce the set of 2.sup.M codebook vectors. The entire codebook of 2.sup.M possible excitation vectors is efficiently searched by using the vector sum generation technique with the M basis vectors--without ever having to generate and evaluate each of the 2.sup.M code vectors themselves. Furthermore, only M basis vectors need to be stored in memory (114), as opposed to all 2.sup.M code vectors.

Abstract: A linear microwave attenuator has an absorbing element which is selectively shaped to provide reduced capacitive coupling and increased attenuation by segmenting the absorber into at least two members. The selective shaping reduces both the surface area and mass of the absorber while maximizing the attenuation of possible from the absorber. In this way, reduced size, linear performance, and increased attenuation over those of the prior art are provided by the present invention.

Abstract: An improved two-way radio communication system having a limited number of channels is disclosed which assigns calls in a max-minimum method, in a first embodiment according to the type of call and sector to be served. This disclosed first embodiment includes a method that ascertains the type of call, handoff or first assignment, and assigns a server with a given central controller to a channel frequency within the requestor sector that minimizes interference to present users. The method of the second embodiment controls requests for assignment to a limited number of channels to reduce adjacent channel interference to and from the requestor with respect to present users operating on a system by utilizing one or more thresholds to arrange channel assignments based upon progressively larger or smaller values of received signal strength.

Abstract: An improved radio receiver that maintains a stable predetermined IF frequency upon receipt of input carrier signals of differing frequencies. The IF signal (14) is processed through a signal demodulation unit (16) that includes a tangent processing unit (22) to yield a control signal that varies as a tangent function of both the demodulated IF signal and a reference signal from a reference oscillator (17). This control signal is used to control the frequency and phase of a reference signal (26) used by the IF stage (12) to center the IF signal with respect to the IF stage characteristics.

Abstract: An improved switching arrangement 10 for waveguide is disclosed which comprises, in combination, a coaxial switch 12 and a unified, multi-port, waveguide interface 14. The coaxial switch 12 has coaxial connectors of a first type (12a, 12b, 12c) mounted in a parallel pattern with a preestablished center-to-center spacing. The waveguide interface 14 includes flanges (14a, 14b, 14c), and is preferably formed as a waveguide housing having a transition plate portion and a cover plate portion. Each port of the unified waveguide interface includes internal waveguide-to-coax transitions for coupling to a respective external connector of a second type. The external coaxial connectors (16a, 16b, 16c) are configured in a parallel pattern with center-to-center spacings equal to the preestablished center-to-center spacings of the coaxial switch connectors (12a, 12b, 12c) such that these connectors mate directly with those of the unified waveguide interface.

Abstract: A priority channel scan for use in radios capable for receiving at least two channels, wherein one of the channels is a priority communications channel. The radio periodically interrupts communications on the non-priority channel for very brief moments to allow monitoring of the priority channel for the presence of digital code word segments. These digital code word segments are stored until the complete code word can be reconstructed and compared against stored code words. When a match occurs, the radio switches to the priority channel to allow reception of a priority message occurring thereon.

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 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: A linearized differential amplifier having two feedback paths. One of the feedback paths functions to linearize the output of the differential amplifier. The remaining feedback path functions to slightly limit the operating range of the differential amplifier to ensure the operational stability of the differential amplifier.

Abstract: A power driver including a switch (17) that connects between a power input terminal (12) and a power output terminal (13). A current sense unit (22) provides an over current sense signal if an over current condition should exist with respect to the switch (17). A reference signal unit (23) utilizes a control signal as introduced at a contol signal input (11) to provide a threshold current level signal. A comparator (21) compares the latter two signals and provides an enabling signal to a second switch (19) to disable the switch (17) upon detecting an over current condition. The comparator (21) is enabled by the control signal.

Abstract: A predistortion network preceding a continuous-time active MOSFET-C lowpass filter cancels the inherent distortion of the filter over a large portion of its passband. The lowpass filter has resistive feedback and input devices whose ratio controls its transfer function at DC and low frequencies. The predistortion network has resistive feedback and input devices that control its transfer function and that match the input and feedback devices, respectively, of the active filter. Cancellation of distortion results in low distortion operation for signals in the frequency range from DC to a substantial fraction of the passband. As the filter response rolls off at higher frequencies, imperfect cancellation results in distortion performance similar to that without predistortion. The invention reduces large signal distortion of active MOSFET-C filters, which enhances their use in monolithic system with switched capacitor circuits.

Abstract: An improved digital signal detector for indicating the presence of digital data used in a communication system. While attempting to detect valid data, the detector buffers an incoming signal in a first-in, first-out buffer and allows locally generated data, instead of the buffered signal, to be coupled to an output. After detecting valid data, the detector estimates where in the buffer valid data commenced and either releases data from that point or further delays the signal up to the maximum length of the buffer before releasing it to the output. The invention provides high sensitivity and rapid detection, reduces variation in detection time over previous methods, and allows locally generated data to be inserted into the signal path without loss of valid data.

Abstract: The transmitter in a digital communication system sends a synchronization sequence that uniquely identifies the polarity of the received data. From the received data, the receiver produces non-inverted and inverted polarity data streams that couple to like synchronization detectors. Only the detector to which the correct polarity data stream is coupled responds. Logic circuitry determines which detector responds and, accordingly, selects the polarity of received data to be further processed by the receiver.After polarity is established, both detectors monitor the received data stream of the selected polarity to determine whether synchronization shifts after having been initially established. Monitoring continues until terminated by other receiver circuits.

Abstract: A vehicle mounted mobile transceiver (11) communicates via a secondary mobile unit (51) with a short range portable unit (10). The portable unit (10) can be either a cordless microphone or a transceiver. The portable unit (10) allows a remotely positioned operator to transmit messages to a base station (13). To ensure security and reliable operation, the portable and vehicle mounted units use digitized codes for ID and instruction purposes. These codes are newly generated from time to time by the vehicle mounted unit and are imparted to the portable unit via a battery charging interface. An improved remote squelch detect is also provided. The improved remote squelch detect substitutes the normal input to the vehicle primary mounted mobile transceiver (11) squelch gate for an audio signal.

Abstract: A modulation and range shift device for use with a PLL frequency synthesizer VCO. The modulation signal is provided to the negative side of the tuning varactor (16) of the VCO (14). In addition, variable voltages can be applied to the negative side of the tuning varactor (16) to achieve range shift as desired. Component variations in the modulation section (18) need not be varied to accommodate changes in the loop filter (12 and 13) of the PLL circuit.

Abstract: An attenuator for use in attenuating an incoming signal. The attenuator includes a primary attenuation unit (12) and a dynamic reference signal unit (13) that provides a reference signal that substantially tracks a DC component associated with the attenuator. A comparison unit (14) subtracts the reference signal from the attenuated signal to provide an attenuated signal substantially free of unwanted signal components. In one embodiment of the invention, a variable impedance unit (101) can be provided to supplement the attenuation action of the attenuator (12) and effectively expand the attenuation range of the circuit and thereby provide greater freedom from distortion.

Abstract: A voltage controlled oscillator having a first feedback path and a second feedback path. The first feedback path may include a phase shift unit (13) as necessary to compensate for an inherent phase shift provided by the resonant circuit (11) used therewith. The second feedback path includes a steering network (17) that responds to an external control signal to cause the output signal to be selectively in either of two phase relations with respect to the incoming signal. The control signal can also control the magnitude of the output signal. By control of the phase relationship and the magnitude, the steering network (17) can effectively control the output frequency of the resonant circuit (11).