5815results about "Phase-modulated carrier systems" patented technology

Embodiments of the present invention are directed to processing an incoming signal by using a demodulation signal, while controlling the phase of the demodulation signal in relation to the incoming signal. The incoming signal can be processed by being mixed with the modulation signal at a mixer. The mixing may thus cause various beneficial modifications of the incoming signal, such as noise suppression of the incoming signal, rectification of the incoming signal, demodulation of the incoming signal, etc.

A cellular radio communication system is provided for transmitting data over a plurality of transmission links. The system includes means for generating a modulated signal by applying a constant amplitude envelope modulation scheme to data to be transmitted across poor quality transmission links and amplifier means for non-linearly amplifying the modulated signal. The system can additionally include means for generating a second modulated signal by applying an amplitude dependent modulation scheme to data to be transmitted across higher quality transmission links and amplifier means for linearly amplifying the second modulated signal. Using a constant amplitude envelope modulation scheme, such as GMSK or MLCAM for poorer quality links means that for these links signals can be amplifier non-linearly at higher gains.

A method for communicating a plurality of data streams between a transmitting device with multiple transmit antennas and a receiving device, is disclosed. The method comprises determining a set of power weightings, efficiently quantizing the power weightings, and providing the set of power weightings the transmitting device. Another aspect of the invention comprises the transmitter implicitly signaling the number of data streams which the receiver should feedback information for through the amount of feedback requested. An additional aspect of the invention is a means of determining the best codebook weights by combining the maximum power and maximum capacity criteria.

An adaptive transmission scheme provides multiple levels of adaptation. At a first level, a selection is made between a limited feedback or open loop scheme and a rich feedback or closed loop scheme. At a second level of adaptation, a diversity mode is selected. Additional levels of adaptation could be employed.

A base station capable of performing precoding in a wireless communication system is provided. The base station includes a plurality of codebooks and a codebook selector. Each codebook comprises a plurality of composite precoding matrices that are generated based on a corresponding diversity precoding matrix. The codebook selector is operable to select one of the codebooks for use in a communication session with a subscriber station.

The present invention is related to a method for multi-user wireless transmission of data signals in a communication system having at least one base station and at least one terminal. It comprises, for a plurality of users, the following steps: adding robustness to frequency-selective fading to the data to be transmitted. performing spreading and scrambling of at least a portion of a block of data, obtainable by grouping data symbols by demultiplexing using a serial-to-parallel operation, combining (summing) spread and scrambled portions of the blocks of at least two users, adding transmit redundancy to the combined spread and scrambled portions, and transmitting the combined spread and scrambled portions with transmit redundancy.

A DC offset correction loop (200, 300) utilizes a peak estimator (218, 322) to determine peaks associated with a digital signal (238, 338). The peak estimator (218, 322) averages the peaks in order to estimate the DC offset. A summer (216, 326) sums the DC offset (242, 350) with the digital signal to produce a corrected output.

Determining a compensated phase matrix for a multi-stimulus demodulation process is provided. A first drive line of a multi-stimulus sensing system is selected, and a stimulation signal is transmitted on the selected drive line. A channel gain resulting from the stimulation signal is measured from a received sense signal resulting from the stimulation signal. The measured channel gain is compared with a known channel gain to obtain an individual phase compensation for the selected drive line. A compensated phase matrix is formed of the individual phase compensation values for multiple drive lines.

An efficient decoding of vector signaling codes is obtained using a circuit that ranks received signal levels, designates ranked values as representing particular code elements, and translates those particular code elements into a decoded result. An optimized ranking circuit combines analog crossbar switching of signal values with comparators that provide digital results. These elements may be repetitively tiled into processing arrays capable of larger ranking operations, or iteratively applied to selected portions of the data set under control of a sequencer or controller.

A synchronization signal detection circuit and method of a digital TV (DTV) receiver are provided. The synchronization signal detection circuit determines a precise main path by determining powers in consideration of the influence of multiple paths near signals located at a peak value location and guarantees a stable operation of an equalizer by using error values output from a decoder to generate a synchronization locking control signal. A power signal based on the correlation of the received signal with a PN511 sequence is filtered to compensate for a dynamic multipath distortion (e.g., due to other multipath signals near signals located at a peak value location). The magnitude of the filtered power signal is then compared (e.g., with a predetermined threshold value) to determine the position of the main path (e.g., at the peak value location, or at a pre or post multipath signal location).

A phase-shift based pre-coding scheme used in a transmitting side and a receiving side that has less complexity than those of a space-time coding scheme, that can support various spatial multiplexing rates while maintaining the advantages of the phase-shift diversity scheme, that has less channel sensitivity than that of the pre-coding scheme, and that only requires a low capacity codebook is provided.

A method and spread spectrum transceiver for demodulating a spread spectrum signal is disclosed. A spread spectrum phase shift keyed (PSK) modulated information signal is received within a demodulator of a spread spectrum receiver on a signal channel. The information signal includes a sequence of data symbols formed from a plurality of high rate mode chips. A precursor portion of the signal channel is Viterbi detected. A multi-state trellis is formed having a predetermined number of states. A post-cursor portion of the signal channel is feedback equalized with a finite impulse response filter having feedback taps operatively connected to a chip detection circuit that tracks high rate mode chips and a carrier loop circuit for phase and frequency tracking. The information signal is despread within a spread spectrum code function correlator.

A digital VSB transmission system in disclosed. The system is compatible with the existing ATSC 8T-VSB receiver and able to transmit additional supplemental data as well as MPEG image/sound data. It initially encodes the information bit of the supplemental data with a ½ encoding rate in order to produce a parity bit and sends the parity bit together with the information bit. Therefore, both of the MPEG image/sound data and the supplemental data can be transmitted properly even through a channel having a high ghost and/or noise level. Particularly, it can significantly improve performances of the slicer predictor and trellis decoder of the VSB receiver.

A power calculating and amplitude limitation judging portion 13 calculates the power value x of the digital quadrature baseband signal I, Q from a transmission data generator 1, and compares the power value x with a power threshold value y set by a threshold value setting portion 14 to judge whether amplitude limitation is needed or not. An amplitude maximum limiting portion 12 subjects the quadrature baseband signal from the transmission data generator 1 to the amplitude maximum value limitation based on the judgment result in the power calculating and amplitude limitation judging portion 13. Thereafter, the digital quadrature baseband signal which has been subjected to the amplitude maximum value limitation by the amplitude maximum value limiting portion 12 is subjected to the distortion compensation using complex multiplication based on the distortion compensation data by a non-linear distortion compensation calculator 2.

A digital receiver, that may be used to receive VSB/QAM digital television signals, includes an adaptive fine carrier recovery circuit that compensates for deviations in the carrier frequency or phase. The carrier recovery circuit de-rotates a signal including phase errors. Estimations of phase errors are filtered using a filter whose gain and bandwidth are adjusted adaptively. This allows the carrier recovery circuit to track phase/frequency offset without introducing significant jitter. In one embodiment, the receiver includes a DFE, and the adaptive carrier recovery circuit mitigates instability that might be associated with the DFE.

A smart radio incorporating Parascan® varactors embodied within an intelligent adaptive RF front end. More specifically, this is provided for by a smart radio incorporating Parascan® varactors embodied within an intelligent adaptive RF front end that comprises at least one tunable antenna; at least one antenna null steering facility associated with said at least on tunable antenna; at least one tunable duplexer receiving the output from and providing input to said at least one antenna null steering facility; a first tunable RF filter receiving the output from said at least one tunable duplexer and providing the input to an analog to digital converter, said analog to digital converter providing the input to a digital signal processor, the output of which is input for a digital to analog converter; a second tunable RF filter receiving the analog output of said digital to analog converter and providing an input to said at least one tunable duplexer.

A digital receiver for a burst-mode wireless communication system, such as a Bluetooth system comprises a radio frequency input stage for receiving an input signal and an analogue-to-digital converter for converting the input signal from an analogue signal to a digital signal. A switch is coupled to the analogue-to-digital converter and a first signal processor is coupled to the switch and is arranged to demodulate signals modulated according to a first modulation process, such as a GFSK modulation process. A second signal processor is also coupled to the switch and is arranged to demodulate signals modulated according to a second modulation process, such as π/4DQPSK modulation process or an 8DPSK modulation process. The switch is arranged to switch the digital signal between the first and second signal processors to recover signals from the first and/or the second modulation process. A method for processing received signals in a burst-mode wireless communication system is also disclosed.