Patents Assigned to Novatel Communications Ltd.
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Patent number: 6061024Abstract: An antenna for use with portable duplex radio transceivers, such as those found in hand-held cellular telephones, which includes a pair of co-planar radiating patch elements elevated above a conductive surface by a conductive bar. The surface and bar define a reference ground plane which inherently isolates the patches. The patches are shaped so that they operate in a desired frequency band as well as band-pass filters--one of the patches is tuned to the transmit band and serves a transmit structure, and the other patch is tuned to the receive band and serves as a receive structure. Switching devices such as positive-intrinsic negative (PIN) diodes can be disposed along the space between the patches and the ground plane to allow each structure to be tuned. The antenna is efficient, because of inherent isolation between the receive and transmit patches, and eases the front end filtering functions traditionally performed by a duplexer. It can be completely enclosed within the chassis of a hand-held telephone.Type: GrantFiled: November 30, 1992Date of Patent: May 9, 2000Assignee: Novatel Communications Ltd.Inventors: Andrew E. McGirr, Paul L. Camwell, John G. McRory
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Patent number: 5644311Abstract: A system uses a charge storage unit to produce shaped pulses in response to an incoming digital signal. The system detects transitions or patterns in the digital signal and produces a charging waveform that controls the charge maintained in the charge storage unit, and thus, the instantaneous value of an output voltage produced by the unit. The charging waveform is, in turn, controlled by transition characteristics or counts that are stored, respectively, in transition memories. In the case of a binary transmission the memories contain rising and falling characteristics. These memories are addressed by addresses generated in response to the detection of a pattern, or as appropriate, a transition in the incoming digital signal. The charging waveform may be a series of pulses with varying widths, a signal that has a variable duty cycle, or a varying pulse count. The charging waveform controls the charging of capacitors in the charge storage unit, which consists essentially of cascaded low pass filters.Type: GrantFiled: July 7, 1995Date of Patent: July 1, 1997Assignee: NovAtel Communications, Ltd.Inventors: Ashfaq Choudhury, Humphrey Gordon
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Patent number: 5621769Abstract: A diversity receiver employing maximum-likelihood-sequence estimation employs a separate channel estimator (44-1, . . . , 44-L) for each of a plurality of diversity channels. Each channel estimator (44-1, . . . , 44-L) produces channel-model parameters ([f.sub.1 ], . . . , [f.sub.L ]) that characterize their respective channels. A weighting-and-accumulation circuit (56) computes the responses of the thus-represented models to candidate symbol sequences, and metrics indicating the likelihoods that respective candidate sequences were the sequences actually sent are determined by comparing the model output with the received signal in a comparison circuit (58) and squaring the magnitudes of the results in a squaring circuit (60). The receiver then employs a Viterbi algorithm (62) to determine which sequence is the one most likely to have been sent.Type: GrantFiled: June 8, 1992Date of Patent: April 15, 1997Assignee: NovAtel Communications Ltd.Inventors: Yongbing Wan, Qingli Liu
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Patent number: 5615232Abstract: A method and device for processing a signal are described, wherein an estimate of a multipath-induced contribution to a demodulated navigation signal is calculated and subtracted from said demodulated navigation signal to obtain an estimated line of sight contribution to said demodulated navigation signal, and a propagation time .tau..sub.0 is calculated from the thus calculated line of sight contribution to said demodulated navigation signal, such that a very accurate propagation time .tau..sub.0 of said navigation signal can be calculated.Type: GrantFiled: November 24, 1993Date of Patent: March 25, 1997Assignee: NovAtel Communications Ltd.Inventor: D. J. R. Van Nee
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Patent number: 5526403Abstract: A wireline interface permitting a cellular telephone transceiver to originate and receive calls using both cellular and wireline services. The invention permits a subscriber unit to operate as a standard cellular telephone when it is disconnected from a land-based telephone line, and as both a full-featured telephone and a full-featured cellular telephone when it is connected to a wireline. A wireline interface circuit provides on/off hook, calling identification, and audio signal conversion functions on the wireline signals. A duplexed audio switch permits the audio signals provided to and from a cellular-type handset to be connected either to the cellular transceiver or to the wireline interface adapter, under control of the user. As a result, any handset-provided functions such as speed dialing or hands-free operation are available for use when operating on a wireline circuit as well as when operating on a cellular radio link.Type: GrantFiled: February 24, 1995Date of Patent: June 11, 1996Assignee: Novatel Communications Ltd.Inventor: Ambrose W.C. Tam
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Patent number: 5495499Abstract: A receiver for pseudorandom noise (PRN) encoded signals consisting of a sampling circuit, multiple carrier and code synchronizing circuits, and multiple digital autocorrelators. The sampling circuit provides digital samples of a received composite signal to each of the several receiver channel circuits. The synchronizing circuits are preferably non-coherent, in the sense that they track any phase shifts in the received signal and adjust the frequency and phase of a locally generated carrier reference signal accordingly, even in the presence of Doppler or ionospheric distortion. The autocorrelators in each channel form a delay lock loop (DLL) which correlates the digital samples of the composite signal with locally generated PRN code values to produce a plurality of (early, late), or (punctual, early-minus-late) correlation signals.Type: GrantFiled: February 3, 1995Date of Patent: February 27, 1996Assignee: NovAtel Communications, Ltd.Inventors: Patrick Fenton, Albert J. Van Dierendonck
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Patent number: 5471518Abstract: A cellular telephone (10) stores both the programming for its processor (18) and certain changing parameters in the same flash-memory device (36). The device is sectored so that the changeable parameters can be erased without erasing the program contents, and they are stored and fetched in an associative manner so that erasures are required only infrequently.Type: GrantFiled: August 10, 1993Date of Patent: November 28, 1995Assignee: NovAtel Communications Ltd.Inventors: Douglas K. Barber, Stephan W. Hortensius
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Patent number: 5438683Abstract: An automatic level control circuit for cellular telephone transmitters which is compatible with both existing analog cellular service and expected next generation digital TDMA service. The circuit automatically and dynamically changes modes to maintain communication when a mobile subscriber moves from one type of service to another. In a first mode of operation, which is compatible with existing analog cellular service, the circuit provides a closed loop negative feedback circuit which produces a control signal for continuously controlling the output power level of the transmitter amplifier. In a second mode of operation, which is compatible with proposed digital TDMA service, the circuit operates to alternately close the negative feedback loop during the periods when the transmitter is permitted to transmit (assigned TDMA frames) and open the loop during other periods when the transmitter is turned off. When the loop is opened, the invention temporarily stores the magnitude of the control signal.Type: GrantFiled: September 19, 1994Date of Patent: August 1, 1995Assignee: NovAtel Communications, Ltd.Inventors: Willem G. Durtler, Kiomars Anvari, Chih C. Tsien
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Patent number: 5432803Abstract: A maximum likelihood decoding system includes a branch metric processor which calculates only one of four branch metrics associated with branches leading to two consecutive states S.sub.j and S.sub.+1, where j is even. The system determines the remaining three metrics by producing a second branch metric by manipulating the first branch metric using simple binary operations and assigns the first and second metrics to the second and first branches, respectively, leading to the odd state. The system next retrieves associated path metrics from a path metric memory which stores the information in locations accessed by addresses related to identifiers associated with the branch initial states. After the system selects a surviving path for each end state, it stores in a path memory location associated with the end state information identifying the previous state on the surviving path.Type: GrantFiled: April 30, 1992Date of Patent: July 11, 1995Assignee: NovAtel Communications, Ltd.Inventors: Qingli Liu, Xiangyang Chen, Lise Vanterpool, Andrew Sendyk
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Patent number: 5432859Abstract: A noise-suppression circuit (10) divides the signal from a microphone (12) into a plurality of frequency sub-bands by means of a noise-band divider (18) and a subtraction circuit (36). By means of gain circuits (32) and (34), it applies separate gains to the separate bands and then recombines them in a signal combiner (38) to generate an output signal in which the noise has been suppressed. Separate gains are applied only to the lower subbands in the voice spectrum. Accordingly, the noise-band divider (18) is required to compute spectral components for only those bands. By employing a sliding-discrete-Fourier-transform method, the noise-band divider (18) computes the spectral components on a sample-by-sample basis, and circuitry (50, 52) for determining the individual gains can therefore update them on a sample-by-sample basis, too.Type: GrantFiled: February 23, 1993Date of Patent: July 11, 1995Assignee: NovAtel Communications Ltd.Inventors: Jin Yang, Andrew Sendyk
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Patent number: 5428666Abstract: A mobile radio-telephones having a plurality of number assignment modules ("NAM's") selects automatically one of the NAM's for use for communication. In a preferred embodiment, the mobile radio-telephone attempts to match system identification data in received control signals with system identification data stored in the NAM's, and, on encountering a match, will use the NAM containing the matched system identification for telephone communication.Type: GrantFiled: August 16, 1994Date of Patent: June 27, 1995Assignee: NovAtel Communications, Ltd.Inventors: Kipling W. Fyfe, Susan McIntyre
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Patent number: 5422917Abstract: A receiver (10) for extracting complex values by reference to a local frequency reference determines the frequency offset between a local oscillator (16) and the carrier by employing a circuit (40) for determining a "phase rotation." When a record of the input signal is determined to have resulted from a predetermined reference sequence of complex values, the phase-rotation circuit (40) compares the phases of complex values extracted from this record with corresponding symbols of the reference sequence. By comparing this difference for one part of the sequence with that for another, circuitry (38, 50, 52, 53, 54) in the receiver infers the frequency offset between the transmitter reference and the receiver reference, and a complex multiplier (34) compensates for this offset by multiplying the successive complex-valued samples by a complex exponential whose frequency is the negative of the frequency offset.Type: GrantFiled: January 4, 1993Date of Patent: June 6, 1995Assignee: NovAtel Communications Ltd.Inventor: Kenneth E. Scott
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Patent number: 5414729Abstract: A receiver for pseudorandom noise (PRN) encoded signals consisting of a sampling circuit, multiple carrier and code synchronizing circuits, and multiple digital correlators. The sampling circuit provides digital samples of a received composite signal to each of the several receiver channel circuits. The synchronizing circuits are preferably non-coherent, in the sense that they track any phase shifts in the received signal and adjust the frequency and phase of a locally generated carrier reference signal accordingly, even in the presence of Doppler or ionospheric distortion. The multiple correlators in each channel correlates the digital samples with locally generated PRN codes having multiple offsets, to produce a plurality of correlation signals. The plurality of correlation signals are fed to a parameter estimator, from which the delay and phase parameters of the direct path signal, as well as any multipath signals, may be estimated, and from which a range measurement may be corrected.Type: GrantFiled: November 29, 1993Date of Patent: May 9, 1995Assignee: NovAtel Communications Ltd.Inventor: Patrick Fenton
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Patent number: 5396539Abstract: A cellular telephone system includes a packet-switched digital data communication subsystem overlaying a circuit-switched (e.g., voice) communication subsystem, with voice and data services sharing the same voice channels. The voice communication subsystem provides voice services independently of the operation of the data communication subsystem. On the other hand, the data communication subsystem monitors use of the voice channels for voice communication, and, in response thereto, temporarily allocates one or more of the available voice channels for data service. In a preferred embodiment, each data basestation transmits, from time to time, an available-channel signature to identify those, if any, of the data-allocated channels that are not then being used to transmit voice or data.Type: GrantFiled: December 3, 1993Date of Patent: March 7, 1995Assignee: NovAtel Communications, Ltd.Inventors: Arunas G. Slekys, William A. Gage, William E. Andrietz, Duane Sharman
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Patent number: 5390207Abstract: A receiver for pseudorandom noise (PRN) encoded signals consisting of a sampling circuit, multiple carrier and code synchronizing circuits, and multiple digital autocorrelators. The sampling circuit provides digital samples of a received composite signal to each of the several receiver channel circuits. The synchronizing circuits are preferably non-coherent, in the sense that they track any phase shifts in the received signal and adjust the frequency and phase of a locally generated carrier reference signal accordingly, even in the presence of Doppler or ionospheric distortion. The autocorrelators in each channel form a delay lock loop (DLL) which correlates the digital samples of the composite signal with locally generated PRN code values to produce a plurality of (early, late), or (punctual, early-minus-late) correlation signals. Thus, during an initial acquisition mode, the delay spacing is relatively wide, on the order of approximately one PRN code chip time.Type: GrantFiled: March 24, 1994Date of Patent: February 14, 1995Assignee: NovAtel Communications Ltd.Inventors: Patrick Fenton, Albert J. Van Dierendonck
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Patent number: 5309482Abstract: A radio receiver's digital matched filter (52') is intended to match a pulse-shaping filter (23) in the transmitter whose signals it receives. However, the clock signal on which the matched filter's timing is based is generated by a receiver clock (58') that is independent of the transmitter clock (56) and that is subjected to no timing adjustment to bring the two clock signals into synchronism. So as to ensure that the matched and pulse-shaping filters work together as a Nyquist filter, therefore, a timing-recovery circuit (60') senses the timing offset in the matched filter's output, and a coefficient generator (80) adjusts the matched filter's coefficients in such a manner that the filter itself imposes the delay needed for the required timing relationship between the filters.Type: GrantFiled: March 30, 1992Date of Patent: May 3, 1994Assignee: NovAtel Communications Ltd.Inventors: Andrew S. Wright, Theodorus J. Smit, Martin C. Alcock
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Patent number: 5282228Abstract: A technique for correcting the sampling time and carrier frequency error in a receiver for digitally modulated signals. Discrete-time, complex-valued samples of the incoming signal are fed to a pair of non-linear operators such as correlators. The first correlator provides a signal having a first phase component related to the symbol timing error and a second phase component related to the carrier frequency error. The second correlator provides a signal having a first phase component related to the symbol timing error and a second phase component related to the negative of the carrier frequency error. The phase components are then separated and detected to extract an estimate of the symbol timing error and the carrier frequency error. In the preferred embodiment, the complex-valued samples are frequency-shifted, before being fed to the correlators, so that the phase components of interest appear at zero frequency.Type: GrantFiled: December 9, 1991Date of Patent: January 25, 1994Assignee: NovAtel Communications Ltd.Inventors: Kenneth E. Scott, Michael Kaube, Kiomars Anvari
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Patent number: 5268930Abstract: An improved decision feedback equalizer for use with digital communications. The equalizer includes an error detector, a process controller, a parameter selector and a data buffer for temporarily storing a digital data signal received from a communication channel. The error detector determines whether the equalizer is accurately tracking changes in the communication channel's characteristics or is lost. When the error detector determines that the equalizer is lost, the process controller responsively generates control signals for initiating an optimal retraining/recovery method for the prevailing conditions. In some retraining/recovery methods, data is temporarily stored in the buffer. The stored data is later retrieved and processed once the equalizer is retrained. Retraining is performed using a retraining signal received via the communication channel or, if available, a portion of the data signal which is suitable for retraining, thereby permitting more rapid resumption of data reception.Type: GrantFiled: December 19, 1991Date of Patent: December 7, 1993Assignee: NovAtel Communications Ltd.Inventors: Andrew M. Sendyk, Yongbing Wan
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Patent number: 5263053Abstract: The channel-impulse-response estimator (44') in a maximum-likelihood-sequence-estimation receiver produces channel-model parameters for a model that produces outputs not only for symbol times but also for intermediate times between the symbol times. A symbol-sequence-derivation circuit (42') determines the most-likely sequence on the basis of metrics computed from the differences between the received signal and the responses of the model to candidate sequences not only at the symbol times but also at the intermediate times. An interpolator (100) receives the symbol decisions from the symbol-sequence-derivation circuit (42') and generates intermediate values from them by simulating the Nyquist filter formed by the concatenation of pulse-shaping filters (22 and 24) in the transmitter and matched filters (36 and 37) in the receiver. The channel-impulse-response estimator (44') uses these values together with the derived-symbol values as inputs to its updating process to maintain the model.Type: GrantFiled: March 24, 1992Date of Patent: November 16, 1993Assignee: NovAtel Communications Ltd.Inventors: Yongbing Wan, Qingli Liu, Andrew Sendyk
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Patent number: 5231407Abstract: An antenna for use with portable duplex radio transceivers, such as those found in hand-held cellular telephones, which includes a pair of co-planar radiating patch elements elevated above a conductive surface by a conductive bar. The surface and bar define a reference ground plane which inherently isolates the patches. The patches are shaped so that they operate in a desired frequency band as well as band-pass filters--one of the patches is tuned to the transmit band and serves a transmit structure, and the other patch is tuned to the receive band and serves as a receive structure. Switching devices such as positive-intrinsic negative (PIN) diodes can be disposed along the space between the patches and the ground plane to allow each structure to be tuned. The antenna is efficient, because of inherent isolation between the receive and transmit patches, and eases the front end filtering functions traditionally performed by a duplexer. It can be completely enclosed within the chassis of a hand-held telephone.Type: GrantFiled: June 25, 1991Date of Patent: July 27, 1993Assignee: NovAtel Communications, Ltd.Inventors: Andrew E. McGirr, Paul M. Camwell, John G. McRory