Abstract: The present invention is a system 10 for charging a plurality of remote computers that includes a plurality of switch members 12, each switch member 12 being connected to a predetermined quantity of remote computers via power lines 21 such that each switch member 12 has substantially the same quantity of remote computers connected thereto, a charge bank select member 13 for sequentially connecting each of the switch members 12 to a battery charger 18 such that the battery charger 18 simultaneously charges all remote computers connected to the switch member 12 that is connected to the battery charger 18, and a timer 20 that sets the time period that each switch member 12 is connected to the battery charger 18.

Abstract: In a radiotelephone (30), a channel estimator (39) receives a time division multiple access (TDMA) information signal (31) including a synchronous codeword (44), formed of a first subset of seven sequential symbols (47) followed by a second subset of seven sequential symbols (48), followed by a data sequence (45) formed of multiple sequential symbols. The channel estimator (39) uses the first subset (47) to train, via initializing (51) and updating (52), the channel estimator to stabilize the channel estimate. The channel estimator (39) uses the second subset (48) to train, via initializing (53) and updating (54), the predictor to improve the future accuracy of the channel estimate. The channel estimator (39) then tracks (55) the channel estimate over the data sequence (45) by updating the channel estimator and the predictor over the data sequence (45), without substantially affecting the stability of the channel estimate or the future accuracy of the channel estimate.

Abstract: A voice recognition system (204, 206, 207, 208) generates a variable rejection strictness as a function of at least one background noise level measured during training and noise signal measurements made during an input utterance made during recognition mode of operation. A word entrance penalty is assigned as a function of the variable rejection strictness.

Abstract: A rectangular to phase converter (201) includes a first converter circuit (201B) which limits signals to a predetermined level. A phase selector (259) selects a relative phase from the limited signals. According to one aspect of the invention, input rectangular coordinate signals are mapped to the first quadrant in a first quadrant mapping circuit (201A) before the first quadrant signals are limited and the relative phase signal is returned to the original quadrant by an original quadrant mapping circuit (260).

Abstract: A complex constellation point multiplier (600) multiplies a complex number by a point in a digital modulation constellation. The desired constellation point is mapped to a digital control word. The complex number is connected to multiplicand input nodes (610, 615) and the digital control word is connected to control input nodes (620, 623, 626). Via logic gates (602, 603, 605, 606, 607, 609), the control word controls switches (651-658) and simple arithmetic blocks, such as accumulators (650, 659), scaler blocks (663, 665), and negation blocks (643, 646), to generate an output complex number that is the product of the input complex number and the constellation point. This complex constellation point multiplier provides a lower size and lower power-consumption alternative to traditional complex number multipliers.

Abstract: A diversity receiver (200) recovers clock information from different versions (301, 302) of a transmitted signal (106). The diversity receiver (200) receives the different versions (301, 302), converts the versions (301, 302) into samples (307, 317) via a common sampling clock (309). The receiver (200) then correlates the samples (307, 317) with like synchronization patterns and uses clock information from the received version (307 or 317) which gives the greatest correlation output signal (504, 506) for data detection in one of two detectors (323, 326). The choice of detectors (323, 326) is determined by the diversity receiver (200) by counting the total number of bit-differences output by detectors (323, 326) over a predetermined time period and comparing the total bit-differences with a number represented by a threshold signal (330).

Abstract: In a communications device, two coherent detection algorithms (102 and 103), one of which has a decision feedback equalizer (103), and a detector selection algorithm (104) are used to dynamically select a detector depending on whether delay spread distortion is present. First the correlation of the detector without the equalizer (102) is measured. If this correlation is greater than a predetermined threshold, the data from that detector (102) is used by the communications device. If the correlation is less than the threshold, the correlation of the detector with the equalizer (103) is measured. If this is less than the correlation of the detector without the equalizer (102), the data from the detector without the equalizer (102) is used, otherwise the data is taken from the equalizer (103). In any case, if the detector without the equalizer is used, the detector with the equalizer is turned off.

Abstract: A complex signal correlator (106) and method therefor for correlating, at the multiple points in time, complex sampled (111) and reference (112) signals to produce a complex correlation signal (113). A relationship between the location of the reference signal (112) relative to the real and imaginary axes (301 and 302) is determined. The sampled signal (111) is processed responsive to the determined location, relative to the axes (301 and 302), of the reference signal (112) to produce real and imaginary processed components (210 and 211). The complex correlation signal (113) is produced responsive to adding (202-205) combinations of the real and imaginary processed components (210 and 211). Substituting adders (202-205) in the present invention for multipliers in the prior art complex signal correlators along with processing the sampled signal ( 111) significantly reduces the complexity of the complex signal correlator (106).

Abstract: In a receiver an apparatus and method substantially reduces time dispersion and multipath distortion in a received signal. An equalizer (109), including taps having gain coefficients, produces an equalized signal (110) responsive to the received signal (107) and an adaptive process signal (137), wherein the gain coefficients are adjusted responsive to the adaptive process signal (137). A first mixer (111) mixes the equalized signal (110) and a reference carrier signal (115) to produce a recovered modulated signal (119). A detector (112) detects an estimate signal (129) responsive to the recovered modulated signal (119). An error signal generator (139) generates an error signal (141) responsive to a difference between the recovered modulated signal (119) and the estimate signal (129). A second mixer (147) mixes the error signal (141) and the reference carrier signal (115) to produce the adaptive process signal (137).

Abstract: The present invention presents an apparatus and method for recovering symbols in a data packet (101) transmitted to a receiver from a remote signal source (204) in a time-varying channel using multiple sampling points. In a digital cellular radiotelephone TDMA system, the receiver (202) performs a complex correlation on the desired slot sync word (DSSW) and the coded digital verification color code (CDVCC) in the data packet (101), and on the adjacent slot sync word (ASSW) in an adjacent data packet (102) to produce a first, second and third optimum sampling point, respectively. The data packet (101) is divided into four regions (A, B, C and D). The symbols in each region (A, B, C and D) are serially recovered using one or more of the multiple sampling points depending on the quality of the sampling point adjacent to each region (A, B, C and D).

Abstract: In a communications device, two coherent detection algorithms (102 and 103), one of which has a decision feedback equalizer (103), and a detector selection algorithm (104) are used to dynamically select a detector depending on whether delay spread distortion is present. First the correlation of the detector without the equalizer (102) is measured. If this correlation is greater than a predetermined threshold, the data from that detector (102) is used by the communications device. If the correlation is less than the threshold, the correlation of the detector with the equalizer (103) is measured. If this is less than the correlation of the detector without the equalizer (102), the data from the detector without the equalizer (102) is used, otherwise the data is taken from the equalizer (103).

Abstract: A differential quadrature PSK receiver (100) recovers serial data in a forward and reverse direction in time using a forward and reverse mode PLL (232) and decoder switch (108). The DQPSK receiver (100) is particularly useful for recovering a packet of serial data (Rx) having a time-varying signal level and a relatively long duration. Sync words in the packet (Rx) or adjacent packets (Ry) provide starting points from which the data is recovered. The direction in time of data recovery is dependent on the quality of the time-varying signal level in the packet (Rx).

Abstract: An improved method and apparatus for demodulators for MSK signals. Demodulation of the MSK signals is performed at base-band other than at IF frequencies. A digital signal processor is preferably used.

Abstract: The .pi./4-QPSK coherent detector of the present invention has a vector input and an output comprising recovered data in bit pair form. The .pi./4-QPSK coherent detector recovers bursts of data, in a TDMA system, that has been encoded in an amplitude modulated vector's phase angle. The .pi./4-QPSK coherent detector detects the .pi./4-QPSK constellation of the incoming modulated signal and outputs the recovered data stream.

Abstract: The .pi./4-QPSK coherent detector of the present invention has a vector input and an output comprising recovered data in bit pair form. The .pi./4-QPSK coherent detector recovers data that has been encoded in an amplitude modulated vector's phase angle. The .pi./4-QPSK coherent detector detects the .pi./4-QPSK constellation of the incoming modulated signal and outputs the recovered data stream.

Abstract: An antenna switch control circuit for use in achieving antenna selection diversity in TDM RF receivers. RSSI for at least one antenna is monitored during time slots containing information not of interest. This information can then be compared with other antenna performance information to allow a selection to be made such that the receiver generally operates with the antenna receiving the strongest signal. In one embodiment, all possible antennas are monitored during a time slot containing information not of interest. In another embodiment, RSSI for the selected antenna can be monitored during the time slot of interest, such that antenna selection can again be varied should the selected antenna diminish in performance.

Abstract: The transmission and reception of burst analog signals, such a voice signal, over a TDM system is improved according to the present invention by minimizing discontinuities between the signal at the end of its time slot in one frame relative to the beginning signal at its next time slot in the following TDM frame. In the TDM transmitter, stored digital information transmitted during its time slot is reprocessed during the preceding time slot in the next frame in order to maintain magnitude continuity. In the TDM receiver, the feedback signal to an analog to digital conversion circuit is switched during non-active time slots to follow data being clocked out of a digital storage element at a frame rate such that the data clocked out preceding the next active time slot will correspond to the data present at the end of the preceding active time slot.

Abstract: A clock recovery device suitable for implementation in a DSP functions to correct a signal that includes the clock information for carrier frequency offsets, prior to extraction of the clock signal.

Abstract: A time division multiplexed (TDM) communication device controller is disclosed, which controls all signalling, synchronization and supervisory functions. In one embodiment, the invention operates to control a remote communication device having a vo-coder and buffering means. The remote communication device is enabled to operate as a dispatch, full duplex or a combination dispatch/full duplex communication device. In another embodiment, a primary station (repeater) is controlled to operate as a single frequency repeater (SFR) or as a multi-frequency TDM repeater.

Abstract: A shortened wideband decoupled sleeve dipole antenna is disclosed in which a helically wound upper radiating element and an inductively loaded lower radiating sleeve element reduce the linear size of the antenna. Substantial decoupling is provided by a helically wound feed coaxial transmission line within the sleeve element. A matching network at the antenna feed point provides capacitive reactance above the antenna resonant frequency and inductive reactance below the antenna resonant frequency such that an impedance match between the feed coaxial transmission line is obtained at frequencies above and below the resonant frequency and dual-band performance may be obtained.