Abstract: A method and ALU for implementing logarithmic arithmetic in a multi-stage pipeline is described herein. According to one embodiment, a master function is decomposed into two or more sub-functions. Memory associated with the pipeline stores a look-up table for each stage of the pipeline, where each table represents function values generated based on the corresponding sub-function, and where the look-up table associated with one stage differs from the look-up table(s) associated with at least one other stage. Each stage computes a stage output based on the stage input and the corresponding look-up table. By combining the stage outputs, the multi-stage pipeline outputs the logarithmic arithmetic output.

Abstract: A method and apparatus for using the same multiplexed radio resource to simultaneously transmit a pilot sequence and an information signal is described herein. After traveling through a multi-path propagation channel, a receiver receives the transmitted pilot and information signals, correlates the received signal with the known pilot sequence to determine one or more correlation values, and estimates the multi-path propagation channel based on the correlation values. The receiver uses the channel estimates to process the received signal to remove the pilot sequence from the information signal. By using the same multiplexed radio resource to transmit both the pilot sequence and the user information signal, the present invention enables more radio resources to be allocated to the information signal without compromising pilot-based channel estimation, and provides more regular access to the transmitted pilot sequence at the receiver.

Abstract: The present invention describes a method and apparatus for performing logarithmic arithmetic with real and/or complex numbers represented in a logarithmic format. In one exemplary embodiment, an ALU implements logarithmic arithmetic on complex numbers represented in a logpolar format. According to this embodiment, memory in the ALU stores a look-up table used to determine logarithms of complex numbers, while a processor in the ALU generates an output logarithm based on complex input operands represented in logpolar format using the stored look-up table. In another exemplary embodiment, the ALU performs logarithmic arithmetic on real and complex numbers represented in logarithmic format.

Abstract: The method and apparatus described herein generates realistic audio for a virtual reality simulation based on the position (location and orientation) of a participant's head. The audio may be generated based on independent and dependent audio profiles. The independent audio profile represents the participant-independent propagation of sound from a virtual source to each of one or more virtual objects in the simulation. The dependent audio profile represents the propagation of the sound from each of the one or more virtual objects to the head or ears of the participant based on a position of the participant's head or ears. An audio processor generates the desired audio signal at the head of the participant by combining the dependent and independent audio profiles to determine a total audio profile for the virtual source, and filtering an audio wave corresponding to the virtual source based on the total audio profile.

Abstract: Circuits and methods are disclosed for compensating for received signal distortion caused by non-linearities in the receiver circuitry. An exemplary receiver circuit includes a distortion waveform generator configured to approximate one or more non-linear response characteristics of a downconverter circuit used to downconvert the received radio frequency signal. The estimated distortion waveform thus produced is filtered, using a filter or filters substantially similar to those used for filtering an intermediate frequency signal that includes the desired signal and non-linear distortion products caused by strong interfering signals. The filtered estimated distortion waveform and the intermediate frequency are sampled, to obtain a sampled distortion signal and a sampled signal of interest. The sampled distortion signal is scaled, and subtracted from the sampled signal of interest to obtain reduced-interference signal samples.

Abstract: Circuits and methods are disclosed for reducing interference from transmitter leakage in a radio transceiver. An exemplary method for reducing interference from transmitter leakage in a radio transceiver comprises downconverting, filtering, and sampling a radio frequency signal comprising a desired signal and a transmitter leakage signal to obtain a sampled signal of interest. The method further comprises generating a sampled distortion signal estimate that estimates one or more distortion products of the transmitter leakage signal, such as a squared amplitude obtained from a square-law device or corresponding digital function. Finally, the method comprises combining the sampled distortion signal estimate with the sampled signal of interest to obtain interference-reduced signal samples.

Abstract: Methods and apparatus are disclosed for automatically adjusting antenna impedance match in a wireless transceiver employing phase-amplitude modulation. According to some embodiments of the invention, a wireless transceiver comprises a transmitter circuit and a receiver circuit connected to the antenna by a transmit/receive duplexer. An electronically adjustable matching network is located between the transmitter output and the antenna. To control the adjustable matching network, a directional coupler is located between the transmitter output and the matching network to separate transmit signals reflected from the antenna system, including the antenna, the matching network and the T/R duplexer. The reflected transmit signals are routed to the receiver circuit, which digitizes the reflected signal and determines an antenna reflection coefficient based on the digitized reflected signal and the modulation signal used to create the transmit signal.

Abstract: A method and apparatus for compensating for ISI is described herein. A transmitter and receiver work together to develop pulse shaped OFDM symbols with reduced inter-channel ISI between pulse-shaped OFDM symbols transmitted on different sub-carriers at the same time, and inter-block ISI between pulse-shaped OFDM symbols transmitted on the same sub-carrier at different times. In addition, a pre-compensation element in the transmitter and/or a post-compensation element in the receiver compensate for diagonal ISI occurring between pulse-shaped OFDM symbols transmitted on different sub-carriers at different times.

Abstract: Where two or more multi-valued digital data symbols are modulated so that they overlap after passing through a channel, forming a combined signal, a receiver receives the combined signal and forms detection statistics to attempt to recover the symbols. Where forming detection statistics does not completely separate the symbols, each statistic comprises a different mix of the symbols. A receiver determines the symbols which, when mixed in the same way, reproduce or explain the statistics most closely. For example, the receiver hypothesizes all but one of the symbols and subtracts the effect of the hypothesized symbols from the mixed statistics. The remainders are combined and quantized to the nearest value of the remaining symbol. For each hypothesis, the remaining symbol is determined. A metric is then computed for each symbol hypothesis including the so-determined remaining symbol, and the symbol set producing the best metric is chosen as the decoded symbols.

Abstract: A frequency synthesizer according to the present invention digitally controls an analog oscillator to generate an analog output signal at a desired frequency. A digitizing circuit converts a feedback signal derived from the oscillator output signal to a digitized multi-phase feedback signal. A comparator compares the digitized multi-phase feedback signal to a reference signal generated by the reference signal generator to generate an error signal indicative of the phase error in the output signal. A control circuit generates a control signal based on the error signal to control the frequency of the oscillator output signal.

Abstract: The coupling circuit described herein comprises passive analog components for coupling a transceiver to an antenna, such as an antenna array. The coupling circuit transforms an input signal into an appropriate format for each element of the antenna array. The coupling circuit comprises a coupling network having a plurality of inputs and a plurality of outputs. The inputs provide quadriphase versions of at least one input signal. In one embodiment, the coupling circuit performs a Discrete Fourier Transform (DFT) on the input signal. In another embodiment, the coupling circuit performs a Fast Fourier Transform (FFT) on the input signal. In still another embodiment, the FFT performed by the coupling circuit implements a Butler matrix.

Abstract: A modulator described herein provides digital modulation and direct digital-to-analog conversion capable of achieving 12-bit resolution or higher for high frequency signals. The modulator comprises a digital modulator, conversion circuit, and multiplexer. The digital modulator generates a plurality of sample streams at a plurality of different sample phases that collectively represent a desired modulated digital carrier waveform modulated by a digital input signal. The conversion circuit converts the sample streams into a plurality of continuous analog signals. The multiplexer multiplexes the analog signals together to generate a modulated analog carrier signal representative of the desired modulated digital carrier waveform.

Abstract: A method and apparatus for determining a mobile station's location using an antenna beam that traverses a scan pattern is described herein. In one embodiment, a device transmits/receives a signal as a position of a transmission/reception antenna beam traverses the scan pattern in a non-sequential order. A strength of the received signal is measured at a plurality of the beam positions. After reordering the signal strength measurements, the mobile station location relative to a nominal center of the beam is determined based on the reordered signal strength measurements. Another embodiment uses signals having different frequency components that are transmitted or received in beams executed in different scan patterns. In this embodiment, signal strength measurements associated with different frequency components are jointly processed to determine a combined correlation. The relative mobile station location is determined based on the combined correlation.

Abstract: A modulator described herein provides digital modulation and direct digital-to-analog conversion capable of achieving 12-bit resolution or higher for high frequency signals. The modulator comprises a digital modulator, conversion circuit, and multiplexer. The digital modulator generates a plurality of sample streams at a plurality of different sample phases that collectively represent a desired modulated digital carrier waveform modulated by a digital input signal. The conversion circuit converts the sample streams into a plurality of continuous analog signals. The multiplexer multiplexes the analog signals together to generate a modulated analog carrier signal representative of the desired modulated digital carrier waveform.

Abstract: A fast, high resolution digital-to-analog converter (DAC) is described herein. The DAC comprises a pulse generator, decay circuit, controller, and sample circuit. The pulse generator serially outputs pulses representing digits of a digital word least significant digit first. Each pulse generates a response in the decay circuit that decays over time according to a known decay response. One exemplary decay circuit comprises an RC circuit having an exponential decay response. The controller controls the timing of the pulses output by the pulse generator such that the period of each pulse relates to a predetermined decay amount. The sample circuit samples an output of the decay circuit at a sample time after the decay circuit receives the pulse for the most significant digit. The sampled output represents the analog value corresponding to the input digital word. The digital word may have any length, radix, or format.

Abstract: A method and apparatus described herein uses a mobility server to supplement the mobility management operations of a conventional mobile switching circuit (MSC). The mobility server receives mobility messages from a wireless terminal, and updates a location register associated with the MSC responsive to the received mobility messages. According to one exemplary embodiment, the mobility server has a pre-determined network address, such as a phone number, IP address, etc. The wireless terminal sends the mobility messages as user-plane messages to the pre-determined network address over a traffic data channel. In one exemplary embodiment, the mobility messages indicate the imminent loss of usable base station signals at an identified wireless terminal. For this embodiment, the mobility server may identify a satellite beam associated with the wireless terminal's location based on the received mobility messages, and update the location register accordingly.

Abstract: A frequency synthesizer according to the present invention digitally controls an analog oscillator to generate an analog output signal at a desired frequency. A digitizing circuit converts a feedback signal derived from the oscillator output signal to a digitized multi-phase feedback signal. A comparator compares the digitized multi-phase feedback signal to a reference signal generated by the reference signal generator to generate an error signal indicative of the phase error in the output signal. A control circuit generates a control signal based on the error signal to control the frequency of the oscillator output signal.

Abstract: A fast, high resolution digital-to-analog converter (DAC) is described herein. The DAC comprises a pulse generator, decay circuit, controller, and sample circuit. The pulse generator serially outputs pulses representing digits of a digital word least significant digit first. Each pulse generates a response in the decay circuit that decays over time according to a known decay response. One exemplary decay circuit comprises an RC circuit having an exponential decay response. The controller controls the timing of the pulses output by the pulse generator such that the period of each pulse relates to a predetermined decay amount. The sample circuit samples an output of the decay circuit at a sample time after the decay circuit receives the pulse for the most significant digit. The sampled output represents the analog value corresponding to the input digital word. The digital word may have any length, radix, or format.

Abstract: A mobile station assists the wireless network with handover from a first base station to a second base station. The mobile station receives transmissions from the first base station using a first spreading code corresponding to the first base station while receiving signals from at least one other base station. The mobile station determines the relative signal strengths of the signals received from the other base stations and reports the relative signal strengths to the first base station to support handover determinations by the wireless network.

Abstract: A method and system for facilitating handover in mobile radio communication systems are illustrated. The mobile unit assists in making handover decisions by monitoring the signal strength of control channels transmitted by base stations in neighboring cells. During the handover, the mobile station can receive the same information from and/or transmit the same information to a plurality of base stations to provide diversity combination and improve transmission quality.