Abstract: Transmitted signals from plurality of mobile terminals are received at one or more base stations in a Code Division Multiple Access system. The base stations send the received signals to a central processor in the form of complex signal sample streams. The central processor determines the correlations between the spreading codes used by the mobile terminals and combines the interference correlations with channel estimates to form an interference matrix. The central processor uses the interference matrix to process the received signals reduce the interference between signals from different mobile terminals.

Abstract: A communication system from maintaining synchronization includes a communication signal comprising a carrier and a data signal that is sent from a transmitter to a receiver which includes a phase lock loop. The receiver compares the output of a Viterbi decoder with the output of a quick decision circuit. The Viterbi decoder, which incorporates traceback, determines the minimum aggregate Euclidean distance for multiple symbols. The quick decision circuit determines the minimum Euclidean distance for a single symbol without decoding the symbol. A delay circuit is placed in series with the quick decision circuit to compensate for the traceback delay in the Viterbi decoder. If the difference in the output signals of Viterbi decoder and the quick decision circuit is greater than a predetermined threshold, the phase error signal in the phase lock loop is prevented from updating the phase lock loop filter.

Abstract: A pulse width modulation controlling circuit for a power supply and method for controlling a switchmode power supply is disclosed. The present invention accomplishes control over the switching of the power supply by coarsely and then finely adjusting a time-length signal.

Abstract: In general, the invention facilitates searching for energy peaks in spread spectrum wireless communication systems with greater precision. More particularly, various embodiments of the invention may involve reporting not only an energy peak and its associated offset, but also the energy levels corresponding to one or more offsets occurring before and after the offset at which the energy peak occurs. Interpolation or extrapolation techniques may be used to predict the actual location of an energy peak based on the apparent location of the peak and the energy levels observed at surrounding offsets.

Abstract: Pre-distortion, whose magnitude—and preferably phase—are frequency-dependent, is applied to an input signal in order to reduce spurious emissions resulting from subsequent amplification of the signal. In preferred embodiments, the pre-distortion technique of the present invention is implemented in combination with the (frequency-independent) magnitude and phase pre-distortion technique described in U.S. patent application Ser. No. 09/395,490 (“the '490 application”), where the frequency-dependent pre-distortion corresponds to amplifier distortion that has a magnitude that is proportional to the frequency offset from the carrier frequency and a phase shift of ±90° on either side of the carrier frequency. Since these characteristics match those of a differentiator, a thorough correction of this part of the amplifier's distortion can be achieved using a differentiating filter. Embodiments of the present invention may be implemented in the baseband domain.

Abstract: According to the present invention, there is disclosed a frame synchronization device which detects a time point to start a data frame from a received signal. Here, the received signal is constituted by disposing the data frame following a preamble period constituted by repeatedly disposing a synchronization symbol. The device stores the synchronization symbol in a memory, and establishes correlation between the synchronization symbol stored in the memory and the received signal by the first correlation processor. The received signal is delayed by a time corresponding to a length of the synchronization symbol by a delay unit, correlation is established between signals before and after the delay by a second correlation processor, and the preamble period is detected from a correlation processing result. The start time point of the data frame is detected based on the correlation processing result of the first correlation processor obtained during the preamble period.

Abstract: A path storing circuit has path holding parts at a plurality of stages storing a survivor path and corresponding to times. A majority decision circuit receives output values of three delay circuits including the top and bottom delay circuits each receiving a selected output of a selector out of six delay circuits in the path holding part at the final stage and makes a decision by a majority.

Abstract: An adaptive pulse position modulated CDMA scheme for use in UWB communications systems is disclosed. A stream of input bits is encoded with spreading code sequence. The spreading code sequence consists of a number of code elements that may have one of two values. Each bit is encoded into a symbol consisting of a predefined number of chips, which are transmitted during a symbol period. Next, at least one code element is associated with each chip in the symbol. Then, an encoded pulse is generated in each chip. Each encoded pulse has a value determined by multiplying the data bit with the code value associated with the particular chip. The encoded pulse is then pulse position modulated by shifting the position of the pulse to a first position or a second position within the chip depending upon the encoded value of the pulse.

Abstract: Receiver is provided having an integrated clock phase detector for the detection of the clock phase deviation between desired sampling instants and the sampling instants of a reception signal which is transmitted from a transmitter (2) with a transmission filter via a transmission channel (3) to the receiver (1). The receiver has at least one matched filter (8) and at least one frequency matched filter (9). The magnitude of a first convolution product of the impulse response of the transmission filter, of the transmission channel (3) and of the matched filter (8), for the maximization of the signal/noise power ratio (SNR) of the reception signal, is maximal at the desired sampling instants.

Abstract: A method and apparatus for reducing the bit rate of multi-input systems that employ space-time coding by displacing in signal space the derivatives of a symbol. A mapped particular symbol is space-time coded to generate transmit-sequences having a phase-shifted version of the particular symbol, the phase-shifted version and the particular symbol differing in phase by an amount other than by 90°, 180°, and 270°. In one embodiment, the particular symbol represents a point in a first symbol constellation and the derivatives of the particular symbol represent points in a displaced symbol constellation. In another embodiment, the particular symbol and another symbol are space-time coded to form the transmit-sequences. The derivatives of the particular symbol represent points in a first symbol constellation and derivatives of the other symbol represent points of a second symbol constellation. The two constellations are displaced versions of each other.

Abstract: One embodiment of the present invention includes a control circuit, an increment register, and an accumulator. The control circuit generates a channel enable signal based on control information from a processor at a first clock signal having a first clock frequency. The channel enable signal selects a channel for a satellite in a global positioning system (GPS). The channel operates at a coarse/acquisition (C/A) clock signal having a second clock frequency. The increment register stores an increment value for the selected channel at the first clock signal. The accumulator generates a pseudo-random noise (PN) clock signal to a PN generator using the increment value.

Abstract: A power efficient and reduced electromagnetic interference (EMI) emissions multi-transmitter system for unshielded twisted pair (UTP) data communication applications. For each transmitter, digital transmit data is converted to a current-mode differential signal analog waveform by a digital-to-analog converter (DAC). The output current from each DAC is used to generate the required transmit voltage on the respective UTP line. Timing circuitry staggers the time base of each transmitter to reduce the aggregate EMI emissions of the multi-transmitter system.

Abstract: In an automatic phase alignment circuit for a Cartesian feedback amplifier, the phase error is regularly monitored. In various implementations, this approach is used to provide true and continuous phase alignment. Based on a relationship between the up-converted and down-converted signals, another implementation of the invention provides phase-alignment for quadrature-phase components of a baseband signal by arithmetically combining the quadrature-phase components and the feedback components continuously and, in response, continuously phase-adjusting signals in the feed-forward signal path. Another aspect of the present invention is directed to an approach for calculating phase error for that is caused by DC-offset interference which, in turn, manifest at the outputs of many analog functional blocks.

Abstract: A method is provided for detecting the data transmission rate of a USB controller by using a USB device having at least one program storage device. An IRQ signal of a timer is activated through a program. If the USB controller transmits a signal corresponding to a high-speed USB controller within a pre-determined period of time, the data transmission rate is set to a high-speed mode. If the signal is not detected, data transmission is set to a full-speed mode.

Abstract: The invention relates to a method and a device for transmitting information symbols using a plurality of carriers, wherein a first transmission symbol is produced (52, 54) on the basis of an information symbol. A second transmission symbol is also produced (52, 54) on the basis of the same information symbol, wherein the second transmission symbol differs from the first transmission symbol. The first and second transmission symbols are modulated (56) on a carrier and transmitted (62) at different intervals. The invention further relates to a method and a device for receiving information symbols represented by the first and second information symbols, wherein both transmission symbols received are used in order to extract the information symbol contained in both transmission symbols.

Abstract: One embodiment of the present invention includes a first memory, an address counter, and an adder. The first memory having KN locations stores K sums of mixer samples during an epoch interval. The mixer samples are generated at a first clock frequency from a mixer for N channels corresponding to N satellites in a global positioning system (GPS) receiver. The address counter generates an address modulo-KN corresponding to a first location in the memory at the first clock frequency. The adder adds one of the mixer samples to contents of the first location to generate a sum. The sum is written into the first location.

Abstract: Systems and methods for estimating and correcting a DC offset in a receiver in the presence of a carrier frequency offset. Samples corresponding to a transmitted signal are received. Each sample is corrected for a carrier frequency offset. An average value is computed for a training sequence of the corrected samples, where the training sequence has a known DC offset. The average value is adjusted using an adjustment factor that reflects an effect on the DC offset of the act of correcting for a carrier frequency offset, thereby generating a DC offset estimate.

Abstract: A method and apparatus for providing efficient and accurate electronic data transmission of information on a data bus in the presence of noise. Data signals are received on a plurality of input lines by a spacial derivative encoder. The spacial derivative encoder encodes the signals and transmits them to a receiver having a spacial derivative decoder. The spacial derivative decoder then decodes the signals. Minimal overhead is required as for n input lines only n+1 lines are needed to transmit each of the encoded signals.

Abstract: A phase-locked loop locks relatively quickly to a pilot tone of the stereo-multiplex signal when a new transmitter is tuned in. The stereo-multiplex signal may be multiplied in a multiplier by the quadrature component of the pilot tone generated by a digital oscillator. The result is a control signal that is provided to a low-pass filter, and the low-pass filtered control signal is provided as a control signal to an oscillator which may include a table of length N and a counter for addressing the table entries. The zero phase angle ?0 may be set by a counter offset n0 by incrementing or decrementing the counter. A table may be utilized having a virtual length N+ which is larger than the length N of the real table. To access the real table, however, the corresponding MSBs of the actual count n(k) are used which match the address space of the real table of length N.

Abstract: Method and apparatus are described for determining when a convolution decoder is out of synchronization. Normalizations from a convolutional decoder are counted to provide a normalization count, and errors from the convolutional decoder are counted to provide an error count. One of the normalization count and the error count is compared to a first threshold associated with the selected one of the normalization count and the error count. The other of the normalization count and the error count is compared to a second threshold in response to meeting the first threshold, such as bit errors per X normalizations or normalizations per Y bit errors. From this latter comparison, an indicator is generated as to whether the convolutional decoder is synchronized or not.