Abstract: A system for switching resources of a computer among a plurality of programs is provided, including a processor for executing programs for the computer. The system further includes a set of register banks coupled to the processor for storing information for the plurality of programs, where each register bank includes a plurality of program information registers in correspondence with the plurality of programs, the set of register banks having a selection input for selecting a current program for the processor to execute. A status register is coupled to the processor for storing in a prioritized order a status bit corresponding to each program, where each status bit has a status bit address and indicates a status of the corresponding program as being one of active and inactive. Each location of the status register is connected to a program determination logic circuit for determining the status bit address of a highest priority active program.

Abstract: Systems and methods for increasing the efficiency of direct current (DC) power to radio frequency (RF) power include a harmonic matching network that inhibits harmonic current flow for a number of harmonic frequencies. The matching network includes a number of sections, where each section generates an impedance that resonates with the output capacitance at a harmonic frequency. Each section of the matching network also creates a high impedance to the amplifier at the respective odd harmonic frequency.

Abstract: A combined filter and digital-to-analog converter (DAC) provides an integrated apparatus for converting a digital data stream into a filtered analog signal. The combined filter/DAC implements an N-tap digital filter using a serial shift register whose register output taps interconnect with a resistive ladder network. Each input to the resistive ladder has a specific signal attenuation (weighting factor) with respect to a ladder output node. Each ladder input's weighting factor corresponds to one of the digital filter tap coefficients. Shift register output taps interconnect with ladder network inputs in an arrangement that matches each output tap to its required weighting factor. With the resistive ladder, very small weighting factors can be realized without using large-value individual resistors that are problematic in high-bandwidth circuits. The filtered analog signal is taken from the ladder's output node and represents the weighted summation of tap outputs.

Abstract: An improved satellite communications system allows for greater spectral efficiency by requiring just two frequencies for wireless communications between a first ground-based station and a second ground-based station via a satellite. Both the first station and the second station use the first frequency to transmit signals to the satellite; the satellite transponds the signals it receives on the first frequency to the second frequency and transmits the signals to the first and second stations on the second frequency. Use of two frequencies in such a manner results in some own-signal interference. The first station preferably stores its outgoing signals in memory and then subtracts out these stored signals to eliminate the its own-signal interference. The second station may likewise store and subtract out its transmissions, but this is not required.

Abstract: An adjustable matching network is provided for a wireless communications device transmitting and receiving signals in multiple frequency bands via an antenna. The adjustable matching network selectively connecting the antenna to a select power amplifier corresponding to a selected transmit frequency band and automatically matching the impedance of the antenna to the select power amplifier. The adjustable matching network also selectively connecting the antenna to a select bandpass filter corresponding to a selected receive frequency band and automatically matching the impedance of the antenna to the select bandpass filter.

Abstract: A method for determining the position of a mobile radio telephone in a satellite communication system includes a mobile radio telephone scanning a plurality of paging channels and measuring the signal strength of the paging channels. The mobile radio telephone then selects the paging channel with the strongest signal strength and decodes the information broadcasted on the selected channel. The information contained in the paging channel can include frequencies or timeslots of paging channels in surrounding spot beams. The mobile station then measures the signal strength of paging channels in surrounding spot beams and quantizes the measurements to determine a coarse position of the mobile radio telephone.

Abstract: A portable wireless communications device is largely controlled in its internal operation and in its interaction with the mobile phone network by a ROM-stored control program written in the JAVA language. The wireless communications device includes a transmitter and a receiver for communicating data via a wireless network control station via radiowaves, a man-machine interface (MMI) for displaying information to the human user and providing interaction with the human user, and a control processor for controlling interaction between the MMI, the operation of the transmitter, the operation of the receiver, and the wireless network station. The control processor is controlled by a stored control program comprising ROM-stored JAVA bytecodes that are interpretively executed by a ROM-stored JAVA interpreter.

Abstract: A method and apparatus for improving the reception characteristics for lower-power portable telephone units at a base station site is disclosed. A normal three-sector antenna site is divided into a plurality of sectors each having a central line of focus. The frequency channels assigned to the base station site are divided among the sectors, and an antenna within each sector radiates the assigned frequencies along the central line of focus for each of the sectors.

Abstract: A method and system for transmitting short data messages in a control station-based TDMA radiocommunication system. Selected TDMA frames are assigned as message frames, and one or more data slots from each message frame are assigned to transmitter/receivers. Data messages can be encoded and transmitted multiple times, at an increased power level, from a control station to a transmitter/receiver over the appropriate data slots in each message frame. The selected TDMA frames are preferably slow associated control channel frames. Also, short alphanumeric messages can be transmitted over the broadcast control channel of a digital radiocommunication link, or another communication channel consisting of one or more slots from successive frames in a TDMA communication link. An increase in transmission power is used in combination with repetition to increase effective signal margin without complications in the mobile unit design, significant delay, or co-channel interference.

Abstract: A transmitter is provided for simultaneously transmitting a plurality of signals in a plurality of directive beams to corresponding destination stations, each destination station located in a separate fan within a service area. The transmitter includes a plurality of beamformers, each beamformer receiving one of the signals to be transmitted to an associated fan, each of the beamformers having a plurality of outputs for each different signal to be transmitted. A plurality of Butler matrices each receive one of the plurality of outputs from the plurality of beamformers for each different signal to be transmitted, each Butler matrix having a plurality of outputs in phased relationship to one another, wherein each of the signals to be transmitted is simultaneously provided across the outputs of each Butler matrix in a phased relationship.

Abstract: A stream of complex numbers is converted into polar form, including an amplitude-representative part and a phase-representative part. The amplitude-representative part of each of the converted complex numbers is represented as a plurality of digits of decreasing numerical significance. The phase-representative part of each of the converted complex numbers is phase-modulated at the radio carrier frequency to produce a phase-modulated drive signal. The phase-modulated drive signal is amplified in a plurality of power amplifiers. A respective one of the power amplifiers provides a maximum output power level at a respective amplifier output that is related to a respective one of the decreasing numerical significance. The output amplitude of a respective one of the plurality of power amplifiers is controlled by applying a respective one of the plurality of digits of decreasing numerical significance to a respective one of the plurality of power amplifiers.

Abstract: A radio base station having a plurality of directional sector antennas for providing communications with outstations lying at different azimuth angles to the base station is disclosed in which the antennas transmit signals using one or both of two orthogonal polarizations such as left hand or right hand circular antennas and polarization and which also measures interference levels on different frequency channels that are used for allocating an optimum channel and polarization for connecting a call. Each of the outstations comprise at least one antenna of selectable polarization.

Abstract: A matched filter computes complex correlations between a sequence of complex input values and a complex code. The matched filter includes a set of N changeover switches having a first input connected to receive real parts of the input sample values and a second input connected to receive imaginary parts of the input sample values. The switches further include a control input for receiving a control signal in first and second states. When the control signal in the first state is applied, a first output of the changeover switch contains the real value part of the input sample values and a second input contains the imaginary part of the input sample values. When the control signal is in the second state the first input contains the imaginary value part of the input sample values and the second input contains the real value part of the input sample values.

Abstract: A method for processing a signal modulated with information symbols to account for an additive offset and slope is disclosed. First, an initial estimate of offset and slope is made and hypotheses of all possible values of a sequence of one or more information symbols are then made. For each of said hypotheses, the associated data symbol sequence is used to make an improved estimate of offset and slope and the improved estimate of offset and slope are stored against each of the hypotheses. For each hypothesis, the improved estimate of offset and slope is used in calculating an expected signal value and a mismatch between a sample of the modulated signal and the expected value is computed.

Abstract: A digital beamforming network for transmitting a first number of digital information signal using a second number of antenna array elements is disclosed. Assemblers are used for assembling one information bit selected from each of the information signals into a bit vector. Digital processors have an input for the bit vector and a number of outputs equal to the second number of antenna elements and process the bit vector. Finally, modulation waveform generators coupled to each of the second number of outputs generate a signal for transmission by each antenna element.

Abstract: A radiocommunication system and method using a combination of a geostationary (GEO) and a plurality of medium earth orbit (MEO) satellites are disclosed. First, a GEO satellite is launched to provide initial system capacity. Next, MEO satellites are successively launched into positions where they can supplement the coverage of the GEO satellite during peak traffic hours. Finally, when a sufficient number of MEO satellites are in place, the GEO satellite can provide the supplementary capacity.

Abstract: A system and method to prevent the inadvertent disclosure of a password. A valid password input request results in a password entry screen being displayed to a user that includes authentication indicia known to the user. Failure to see the authentication indicia causes the user to know that the request is a spoof. The invention may further include a method and system of limiting the applications that operate after a password input request is received. Only the applications necessary for inputting the password operate, as the other applications are set as inoperable until the password has been input. This prevents a remote source from obtaining the password through fraudulent means such as a screen capture or trojan horse program.

Abstract: A transmitter is provided for simultaneously transmitting a plurality of signals in a plurality of directive beams to corresponding destination stations, each destination station located in a separate fan within a service area. The transmitter includes a plurality of beamformers, each beamformer receiving one of the signals to be transmitted to an associated fan, each of the beamformers having a plurality of outputs for each different signal to be transmitted. A plurality of Butler matrices each receive one of the plurality of outputs from the plurality of beamformers for each different signal to be transmitted, each Butler matrix having a plurality of outputs in phased relationship to one another, wherein each of the signals to be transmitted is simultaneously provided across the outputs of each Butler matrix in a phased relationship.

Abstract: A transmitter is provided for simultaneously transmitting a plurality of signals in a plurality of directive beams to corresponding destination stations, each destination station located in a separate fan within a service area. The transmitter includes a plurality of beamformers, each beamformer receiving one of the signals to be transmitted to an associated fan, each of the beamformers having a plurality of outputs for each different signal to be transmitted. A plurality of Butler matrices each receive one of the plurality of outputs from the plurality of beamformers for each different signal to be transmitted, each Butler matrix having a plurality of outputs in phased relationship to one another, wherein each of the signals to be transmitted is simultaneously provided across the outputs of each Butler matrix in a phased relationship.

Abstract: Methods of demodulating a received signal are disclosed in which an interference map containing information regarding a plurality of candidate co-channel interference sources is provided. The information in the interference map regarding the plurality of candidate interference sources may be used to identify any of the candidate co-channel interference sources that comprise a dominant interference source. The received signal may then be demodulated in a manner that cancels at least part of the contribution of any identified dominant interference source by using the information regarding any such interference source contained in the interference map.