Abstract: The signal to noise ratio performance of a RF communication system can be improved by providing resistance to transmitter self-jamming and eliminating or reducing the need for a transmit rejection filter or other measures such as limiters or blanking switches. An anti-jam low noise amplifier provides enough rejection and jamming immunity to reduce or eliminate the need for the transmit reject filter. Thus, the system noise performance is improved by eliminating the filter and the associated losses which cause signal to noise ratio performance degradation.

Abstract: Clear channel assessment (CCA) is a very important issue in Ultra-Wideband (UWB) systems. An effective CCA mechanism will have a large impact on the overall throughput of the communications system. It is disclosed methods and circuits to carry out CCA determinations exploiting the structure of the pulse signal either by using a moving average or by performing a cross-correlation with a locally generated signal.

Abstract: A signal acquisition method includes: performing a correlation operation for a received satellite signal, the satellite signal being transmitted from a positioning satellite; frequency-analyzing a result of the correlation operation over a predetermined time which is equal to or longer than a bit length of navigation message data carried by the satellite signal; extracting a power value in each frequency in which the power value satisfies a predetermined power condition, from a result of the frequency analysis; and acquiring the satellite signal using the extracted power value.

Abstract: A waveform reconstruction system and method for using the same are disclosed. The system includes an RF down-converter that receives a signal and outputs a down-converted signal. A demodulator demodulates the down-converted signal to generate a recovered digital data stream. A pattern detector detects a predetermined pattern in the recovered digital data stream. A delay generator delays the down-converted signal and outputs a delayed copy thereof. A signal processing circuit combines the delayed copy with previously received delayed copies of the down-converted signal to reconstruct an averaged waveform from the plurality of delayed copies having the predetermined pattern.

Abstract: A signal acquisition method includes: performing a correlation operation for a satellite signal received from a positioning satellite; frequency-analyzing a result of the correlation operation over a predetermined time which is equal to or longer than a bit length of navigation message data carried by the satellite signal; extracting a power value in a predetermined frequency which includes at least a specific frequency determined according to the bit length, from a result of the frequency analysis; and acquiring the satellite signal using the extracted power value.

Abstract: A User Equipment (UE) receives and samples communication signals, where the communication signals have a time frame format, a transmission chip rate and a synchronization code associated with a time slot that includes a midamble that indicates a modulation of the synchronization code where a specified modulation of received synchronization codes identifies the timing for a timeslot in which data is to be received. The UE preferably includes a synchronization code determination circuit, a midamble determination circuit, and a phase modulation sequence detection circuit operatively associated with the midamble determination circuit. The UE can be configured for use with the low chip rate option of the Third Generation Partnership Project (3GPP) Universal Mobile Telecommunication System (UMTS) standards that employ a predefined set of downlink SYNC codes that point to midambles which indicate SYNC code modulation sequence to enables reading of data in a subsequent Broadcast Channel (BCH) message.

Abstract: The present invention relates to a method for estimating a propagation channel in the presence of transmit beam-forming within a receiver, accounting for the structure of two logical channels referred as to a common channel and a dedicated physical channel (CPICH, DPCH) and based on a common structure of corresponding propagation channels, said DPCH channel comprising two sub-channels (DPDCH, DPCCH), said propagation channels being modeled as a linear superposition of a finite number of discrete multipath components following an uncorrelated-scattering wide-sense stationary model, a multipath component being characterized by a time-varying multipath complex coefficient and a delay. Use: RAKE Receiver.

Abstract: A signal compression method and apparatus for a base transceiver system (BTS) in a wireless communication network provides efficient transfer of compressed signal samples over serial data links in the system. For the uplink, an RF unit of the BTS compresses baseband signal samples resulting from analog to digital conversion of a received analog signal followed by digital downconversion. The compressed signal samples are transferred over the serial data link to the baseband processor then decompressed prior to normal signal processing. For the downlink, the baseband processor compresses baseband signal samples and transfers the compressed signal samples to the RF unit. The RF unit decompresses the compressed samples prior to digital upconversion and digital to analog conversion to form an analog signal for transmission over an antenna. Compression and decompression can be incorporated into operations of conventional base stations and distributed antenna systems, including OBSAI or CPRI compliant systems.

Abstract: A feedback control law steers a reference phase that tracks the phase of a received code sequence. The reference phase clocks a track-reference signal consisting of a series of correlation kernels, over which data is extracted and then summed in various combinations. The correlation kernels are designed in such a manner that errors caused by multipath are eliminated or substantially reduced. Furthermore, the areas of the correlation kernels are balanced across level-transitions of a code and non-transitions to eliminate phase biases when tracking specific satellites. Extra care must be taken to balance the correlation kernels in this manner due to a little known aspect of GPS C/A codes. Specifically, not all C/A codes have the same ratio of level-transitions to non-transitions as has been assumed in prior art.

Abstract: A detection unit is disclosed for the detection of data symbols contained in a demodulated signal, whereby band spreading occurs transmit-side with the use of first sequences, whose first chips each assume one of two different first values.

Abstract: The present invention provides systems and methods for implementing narrowly spaced correlators to mitigate multipath error, and systems and methods for adaptively changing the correlator spacing for varying multipath conditions. In an embodiment, two sets of correlators with the same code frequency but different code phases are used to implement an adjustable correlator spacing. The correlator spacing is determined by the code phase difference between the two sets of correlators, which can be adjusted, e.g., by adjusting the code phase values of Numerically Controlled Oscillators (NCOs). An advantage of embodiments of the present invention is that they can achieve much narrower correlator spacings than conventional techniques, e.g., by making the code phase difference between the two sets of correlators very small. Further, the correlator spacing can be adjusted for varying multipath conditions, whereas the correlator spacing in conventional techniques is fixed.

Abstract: An apparatus and method for receiving data in a communication system are provided. The method includes identifying first codewords, which have been used in transmission of data by a transmitter, in the data received from the transmitter, setting third codewords by adding second codewords to the identified first codewords, calculating correlation values of orthogonal vectors corresponding to the third codewords and detecting information included in the data based on the calculated correlation values. Accordingly, feedback information may be better received and detected.

Abstract: The present invention relates to methods and systems for enhanced signal acquisition through cross-ambiguity function (CAF) interpolation. In one aspect, the present invention provides methods and systems for CAF interpolation. In an embodiment, a first CAF generated using a low input sampling rate (e.g., 1 sample/chip) is interpolated to generate a second CAF having a higher sample per chip rate. By lowering the initial input sampling rate, cost and complexity of initial synchronization processing can be significantly reduced at the receiver. In another aspect, coherent and non-coherent interpolation methods and systems are provided for time and frequency CAF interpolation. Low cost and low complexity implementations of these methods and systems are also provided with associated CAF peak detection methods and systems.

Abstract: As taught herein channelization code power estimates are generated for a number of data channels in a received CDMA signal based on a joint determination process. Joint processing in this context yields improved estimation of data channel code powers and corresponding estimations of noise variance. These improvements arise from exploitation of joint processing of measured data value correlations across two or more data channel codes represented in the received signal. In one or more embodiments, joint determination of data channel code powers comprises forming a correlation matrix as a weighted average of correlations determined for a plurality of data channels. In one or more other embodiments, joint determination of data channel code powers comprises jointly fitting the correlation matrices for a plurality of data channels in a least squares error estimation process.

Abstract: A demodulator in a receiver includes a correlator (240) for de-spreading a spread-spectrum signal, and a decision module (250) for detecting a preamble and for synchronizing to data frames of the spread spectrum signal. The demodulator includes symbol timers (231 and 233) that allow the demodulator to correlate to two preamble symbols simultaneously, where the two preamble symbols occur one-half a symbol period apart. The correlator includes a correlator structure having taps that correct for any frequency offset of a carrier signal. The correlator correlates to each of the two preamble symbols a plurality of times through oversampling, where each correlation compensates for a different amount of frequency offset. By analyzing occurrence of peaks in magnitude of the correlations, the decision module detects the preamble and selects weights for the taps to de-spread data frames received after the preamble.

Abstract: The invention provides a Global Navigation Satellite System (GNSS) receiver. In one embodiment, the GNSS receiver comprises a memory, a buffer, a correlator, and a selector. The memory stores a memory code and outputs a portion of the memory code as a first code segment. The buffer comprises a plurality of component buffers and stores the first code segment into one of the component buffers in order. The selector selects a portion of the first code segments stored in the buffer as a second code segment output to the correlator according to the code phase selection signal, wherein the data length of the second code segment is equal to a correlation data length of the correlator. The correlator calculates a correlation between a received GNSS signal with the correlation data length and the second code segment.

Abstract: A system including a differential demodulation module that receives modulated signals from R antennas and that differentially demodulates the modulated signals to generate differentially demodulated signals, where R is an integer greater than or equal to 1. A summing module sums the differentially demodulated signals to generate a combined signal. A correlation module correlates the combined signal with derived preamble sequences and generates correlation values based on the correlation. The derived preamble sequences are derived from preamble sequences. Each bit of one of the derived preamble sequences has a first state when a corresponding bit and a bit adjacent to the corresponding bit in a corresponding one of the preamble sequences have opposite states. Each bit has a second state when the corresponding bit and the bit adjacent to the corresponding bit have the same state.

Abstract: A method for the synchronization of a radio receiver, comprising an estimation of the moment when a pulse (11, 17) is received (11, 17), performed from the moment when a previous pulse was received. The estimated moment is compared with the real moment when the pulse (21, 27) is received in order to validate an association of pulses with values of a code recorded in the receiver (31, 37). A moment for the beginning of transmission of a symbol is thus deduced, enabling the receiver to be synchronized in relation to the transmitted radio pulse sequence.

Abstract: The present invention relates to an apparatus and method of acquiring initial synchronization of a terminal in a mobile communication system. According to an exemplary embodiment of the present invention, one or more auto-correlation values of a preamble constituting a signal that is received from a base station are calculated. Averages of the calculated auto-correlation values according to samples are calculated, and then a peak value is detected among the calculated values. Then, a cell search is performed on the basis of the detected peak value, and a peak value from the result of the cell search is regularized. Then, the regularized peak value is compared with a predetermined reference value such that it is checked whether synchronization of a signal that has been searched is accurate or not.

Abstract: Delay estimation apparatus and method, comprising: a correlation step which a correlation function between a received signal and a supplied template waveform is generated, AD conversion step at which said correlation output generated at said correlation step is uniformly sampled into discrete samples; and arithmetic operation step at which a time delay estimate of the received signal based on said discrete samples generated at said AD conversion step is computed, wherein a selection criterion depending on the digital sampling frequency used at said AD conversion means is checked, if said selection criterion is satisfied, computes the time delay estimate based on the direct pick method, and if said selection criterion does not hold, computes the time delay estimate based on the simplified maximum likelihood (ML) method.

Abstract: A method and system for detecting the presence of narrowband transmitters utilizing frequencies also utilized by wider band communication systems. In some embodiments an ultrawideband transceiver detects signals at specific frequencies within a spectrum of frequencies, and analyzes the signals to determine if the signals indicate transmissions by a narrowband transmitter in a narrowband communication system. In further embodiments transmission circuitry reduces signal components at frequencies occupied by the narrowband transmitters.

Abstract: Communication devices and methods are disclosed, wherein a test signal is generated at a first frequency and a higher harmonic of said test signal is received and processed at a second frequency higher than said first frequency.

Abstract: The present invention relates to a symbol acquisition apparatus and a method thereof. The method includes: determining a first boundary according to a first preamble symbol and generating a first confidence value according to signal quality of the first preamble symbol; determining a second boundary according to a second preamble symbol and generating a second confidence value according to signal quality of the second preamble symbol; and determining a symbol boundary from the first and the second boundaries according to the first and the second confidence values.

Abstract: A power efficient technique is used to demodulate the coded overhead channels of a geosynchronous (GEO) satellite uplink. A coherent receiver used in a wireless communication system is able to determine the information conveyed in the overhead channel, by effecting channel estimates from codewords extracted from a pilot signal. A valid set of codewords is established. Pilot symbols are extracted from a pilot signal and a channel estimate is made from the pilot signal. Codewords in the set of valid codewords are correlated and a channel phase ambiguity in the signals is removed and a codeword with the largest correlation is chosen. The chosen codeword is used to create a revised channel estimate.

Abstract: Rake receivers in code division multiple access (CDMA) telecommunication comprise fingers (1,2,3) with each finger processing signal components for a particular transmission path to be able to better synchronize with a RF signal received via different paths, and a combiner (4) for combining the results originating from said fingers, and a compensator in the form of a controlled oscillator in a feedback loop. By locating a finger compensator (20-25) in a finger, said finger can handle complex situations, like Doppler shifts under high-speed conditions. Preferably, most or all fingers each comprise such a finger compensator, in which case said feedback loop can be avoided. Such a finger compensator can be hardware, software or a mixture of both when comprising a filter (21) plus an amplitude normalizer (22) between two arithmetical modules (20,25) for multiplying an input symbol signal with a conjugated previous input symbol signal and an output symbol signal with a previous output symbol signal.

Abstract: A method and device for adapting a signal is provided. The signal includes a number of recurring samples of data. In one example embodiment, the method receives recurring samples of data. Each of the samples of data includes a first number of elements. A second number of elements are selected from at least one of the recurring samples. The second number of elements is approximately less than the first number of elements. The selected second number of elements are substituted with respective phase altered elements. The subject matter also provides a method and device for identifying a signal property(ies) and a computer system for implementing these methods.

Abstract: A wireless communication device uses a time-invariant delay-Doppler channel response estimate for received signal demodulation. The device provides coherent signal demodulation by accounting for frequency and time selectivity in a land-based mobile communication environment, which arise mainly because of delay and Doppler shifts, respectively. In one embodiment, the wireless communication device includes a channel estimator that estimates channel response in a wireless communication network by estimating a delay-Doppler response of a wireless communication channel to obtain a delay-Doppler channel response estimate and converting the delay-Doppler channel response estimate to a time-varying channel response estimate, e.g., a time-varying frequency or impulse response. The delay-Doppler response may be estimated in a continuous or discrete domain.

Abstract: A circuit and algorithm are disclosed for a step2 search of a three step search of synchronization channels in a W-CDMA system. A mobile terminal of the CDMA system includes an RF downconverter for receiving I and Q signals. A searcher, responsive to the I and Q signals, includes a first correlator for correlating the I and Q signals with a primary synchronization code on a primary synchronization channel, and a second correlator for correlating I and Q signals with a secondary synchronization code on a secondary synchronization channel. The correlated I and Q signals are added for each of the secondary synchronization codes. An energy calculator and a maximum energy detector use the correlated I and Q signals of both the primary and secondary synchronization channels to detect the most likely scrambling code group of secondary synchronization codes.

Abstract: A modulation device includes: a spread code generation unit which generates a spread code having a predetermined cycle; an audio signal input unit to which an audio signal is input; a first modulation unit which phase-modulates the spread code in each cycle on the basis of a data code; and a combining unit which combines the audio signal with a modulation signal which has been generated on the basis of the phase-modulated spread code and distributed in a frequency range higher than a predetermined frequency to output a combined signal.

Abstract: A direct-sequence spread spectrum (DSSS) receiver may be operable to process signal samples in frequency domain utilizing a prime factor fast Fourier transform (FFT) circuit and a pseudorandom noise (PRN) code. The DSSS receiver may be operable to transform the signal samples into FFT signal samples using the prime factor FFT circuit, transform the PRN code into a FFT PRN code using the prime factor FFT circuit and multiply the FFT signal samples with the FFT PRN code using the prime factor FFT circuit. The DSSS receiver may be operable to inversely transform the multiplied FFT signal samples into correlated signal samples using a prime factor inverse FFT (IFFT) implemented by the prime factor FFT circuit. The prime factor FFT circuit may comprise a prime length FFT core, a FFT memory, a register bank, a switch, a multiplier and a FFT controller.

Abstract: A device for decoding a direct sequence spread spectrum-encoded binary message includes a sampler that captures at least one sequence of binary samples corresponding to one bit of the transmitted message. The captured sequence of samples are applied to a filter matched to the spreading code used, thus making it possible to delete the spreading applied to the original message. The device further includes, at the output of the sampler, an error correction block including a memory storing a plurality of binary sequences corresponding to all of the possible values for a captured sequence of samples. A replacement circuit replaces the captured sequence of samples with the stored sequence, thereby minimizing the number of samples different from the captured sequence of samples, and allowing the stored sequence to be applied to the matched filter.

Abstract: An apparatus and a method for estimating a Carrier to Interference and Noise Ratio (CINR) of an uplink channel in a wireless communication system are provided. The apparatus includes a subcarrier separator for separating subcarrier bundles from a received signal, a detector for calculating squares of correlation values acquired by correlating one or more codewords with signal streams of the separated subcarrier bundles, and a CINR estimator for estimating a CINR using a maximum value and an average value of the correlation value squares calculated at the detector. With the accurate CINR estimated, the channel information delivery and the stable system operation can be achieved.

Abstract: A system for determining the burst start timing of a signal includes logic configured to receive the signal, generate correlation moduli and generate a first timing output based on the correlation moduli. The logic may also be configured to receive operating mode information and timing information and generate search controls. The logic may further be configured to identify a maximum of the correlation moduli using the search controls and determine a second timing output associated with the maximum correlation modulus. The second timing output represents a more accurate approximation of a burst start time than the first timing output.

Abstract: Methods and apparatuses are provided for implementing a multiple-mode correlator within a receiver. The multiple-mode correlator may include at least one pre-multiplier portion and a plurality of correlation portions that selectively process multiply result signals from the pre-multiplier portion.

Abstract: A method for the acquisition of a radionavigation signal carrying a spreading code with a quasi-infinite period, where the signal is sampled in baseband on a delay line and correlated with a local spreading code replica, the sampled signal is shifted on the delay line from one correlation to the other, where in order to correlate the signal with the local replica of the code, a plurality of sequences of the spreading code are generated, the code sequences being of the same duration, equal to the duration of the signal sampled on the delay line, and associated with the consecutive time ranges in the temporal alignment search space, where each of the code sequences is correlated with the signal sampled in a respective correlation operation, the correlation operations being executed in parallel for the different sequences of code.

Abstract: Methods and apparatuses for acquiring a satellite signal includes generating a differential code using first, second and third segments of a satellite signal received from a positioning satellite, obtaining a correlation value by performing a correlation using the differential code and a replica of the spreading code, and acquiring the satellite signal using the correlation value. The differential code is generated by performing a differential operation on a spreading code from the positioning satellite.

Abstract: Provided is a synchronization error tracking device and method. The method and system estimates and corrects the synchronization error generated by time and frequency offsets during the data transmission interval and uses a module designed for initial synchronization or channel estimation without adding a new correlation operator. Further, a combining mark value and a synchronization position value acquired during the synchronization process are used.

Abstract: A variable code-tracking loop filter in a receiver having the ability to change its parameters multiple times in response to received signals. Parameters for the code-tracking loop filter may be varied based on phase and frequency errors from an error detector. In one implementation, the code-tracking loop filter is able to repeatedly vary a single parameter, such as its received bandwidth, based on the phase and frequency errors, while in another, the code-tracking loop filter may vary two or more parameters, such as the loop bandwidth and the natural frequency.

Abstract: Embodiments of the present general inventive concept relate to a transient signal compensator for apparatuses such as a transceiver or receiver used in a wire/wireless communication and/or a digital signal processor that may be used in the receiver and methods thereof. In one embodiment, a receiver can include an amplifier to amplify a received signal, a digital filter to filter a digital signal corresponding to an output signal of the amplifier, where the digital filter is configured to replace a corresponding value (e.g., stored in a memory) for the digital filter with a gain compensated value during a predetermined delay time after a gain of the amplifier is changed (e.g., from a first gain g1 to a different second gain g2). The gain compensated value to compensate for a transient signal (e.g., related to the change from the first gain g1 to the second gain g2).

Abstract: An interference reduction receiver is disclosed. The interference reduction receiver includes a weight generating unit for obtaining weights by multiplying a signal correlation matrix of an input signal and a channel response vector. The input signal is despread at two or more predetermined timings, the despread signals are multiplied by the weights, the weight-multiplied signals are added, and an original signal is obtained.

Abstract: An apparatus and method for determining feedback information detection in a broadband wireless communication system are provided. In the detection determining apparatus, a demodulator correlates each of tiles carrying received feedback information with an orthogonal vector including a pilot symbol in each possible codeword, each tile being a predetermined number of subcarriers, and calculates the squares of the absolute values of the correlations. A codeword correlation calculator sums the squares of the absolute value of the correlations of the tiles for each possible codeword. A detection decider determines whether to perform detection on the feedback information based on the maximum of the sums.

Abstract: A secure information transmission system includes one or more transmitters and one or more receivers. The transmission waveform employed includes highly randomized, independent stochastic processes, and is secured as a separate entity from the information it carries. The signal, using novel modulation methodology reducing impulse responses, has a paucity of spectral information and may be detected, acquired and demodulated only by communicants generating the necessary receiving algorithm coefficients. The physical area of signal reception is restricted to that of each intended communicant, reception areas following movements of mobile communicants. A unique instant in time is used as basis for communications keys to the securing algorithms dynamically generated on a one-time basis and never exchanged or stored by communicants.

Abstract: A Global Position System signal acquiring system and method is provided in this invention. Pluralities of counters are set, each corresponding to a code bin and a frequency bin of the signal. Subsequently, the signal corresponding to the counters is repeatedly received in a unit of time and the counters are accordingly updated for a pre-determined iteration. At last, a maximum value among the counters is found to acquire the signal corresponding to the counter having the maximum value.

Abstract: A method and a system for the acquisition and tracking of BOC(m,n) modulated codes, m/n equal to an integer, in which a correlation function is calculated of the BOC(m,n) modulated code received from a remote transmitter with a code wa locally generated at a receiver terminal according to one from the following the relationships: wa(?)=c(?n)?a·[prn(?n+Tc/2)?prn(?n?Tc/2)] wa(?)=c(?n)?a·[prn(?n+nTc/2m)?prn(?n?nTc/2m)] wa(?)=c(?n)?a·[prn(?n+nTc/4m)+prn(?n?nTc/4m)] wa(?)=c(?n)?a·[prn(?n+3nTc/4m)+prn(?n?3nTc/4m)] w(?)=[prn(?n+nTc/4m)+prn(?n?nTc/4m)] w(?)=[prn(?n+nTc/2m)?prn(?n?nTc/2m)] wherein c(?) is a local replica of the BOC modulated pseudo-random noise code with delay ?n, PRN(?) is a replica of the unmodulated pseudo-random noise code, and a is a predetermined weight coefficient, and the correlation function being at the base of an acquisition test function whereby a code acquisition is recognized for a value of the test function being higher than a predetermined threshold.

Abstract: An m-code GPS receiver receives m-code GPS communication signals having a multimodal autocorrelation, using an m-code mode identifier unambiguously determining a mode value of one of the m-code modal peaks coherently aligned to a coherent unimodal detected envelope, based on sequential probability estimation in an m-code envelope tracking filter using filter residual estimation or with a coherent m-code and c/a-code tracking filter also based on filter residual estimation, for generating m-code phase errors, for unambiguous and precise m-code code phase tracking in closed feedback loops, for preferred use in navigation systems.

Abstract: Systems and methods for avoiding non-linear behavior of conventional early-minus-late correlator-based code loop discriminators. The present invention provides a model of correlator behavior that takes into account whether both correlators are on the same side of the correlation peak or they straddle the peak. The result is a piecewise solution that can be stitched together quite readily to produce an extended range of linear response, thereby improving the pull-in capability of GPS code loops when closely spaced correlators are being used.

Abstract: A GNSS receiver and method using alternating “A” and “B” time segments for a reception time length of two or more data bits. The GNSS signal in an “A” time period comprising the “A” time segments is integrated for determining “A” magnitudes corresponding to code phase increments and the GNSS signal in a “B” time period comprising the “B” time segments is integrated for determining “B” magnitudes corresponding to code phase increments. A trial-and-error data bit search is performed for depolarizing data bit senses. The code phase increment showing the largest correlation level is used for acquisition of the GNSS signal and/or determination of the location where the GNSS is being received.

Abstract: A method is provided for processing a signal emanating from a multi-path transmission medium. Echoes of the signal that is received are detected, and a rejection processing is performed. The rejection processing includes estimating the cross-correlation between temporally neighboring echoes, and if this cross-correlation satisfies a test, rejecting the one of the two neighboring echoes that exhibits the lower energy. Also provided is a rake receiver that can perform such a method.

Abstract: A receiver (100) is provided for signals of different signal strengths and modulated with respective pseudorandom noise (PN) codes. The receiver (100) includes a correlator circuit (120) operable to correlate the signals with a selectable locally-issued PN code having a Doppler and a code lag to produce a peak, the correlator circuit (120) being subject to cross correlation with a distinct PN code carried by least one of the signals that can produce cross correlation; and a cross correlation circuit (370, 400) operable to generate a variable comparison value related to the cross correlation as a function of values representing a Doppler difference and a code lag difference between the locally-issued PN code and the distinct PN code, and to use the variable comparison value to reject the peak as invalid from cross correlation or to pass the peak as a valid received peak.

Abstract: A method and apparatus for receiving a signal from transmitters such as GPS satellites, for fixing the location of the receiver. Each of the transmitted signals includes a unique periodically-repeating sequence. A received signal is stored by the receiver for at least two repetitions of the periodically-repeating sequence. FFT operations are performed, and the resulting data frequency samples are pruned responsive to a hypothesized residual frequency, a procedure which significantly reduces the total number of subsequent calculations and therefore significantly reduces processing time. A correlation series is determined from the pruned samples and reference frequency samples corresponding to a hypothesized transmitter. If a match is found in the examination of this series, a code phase offset is determined; if not the process is repeated with another hypothesized residual frequency. Multiple correlation series similarly obtained may also be incoherently combined prior to this examination.