Abstract: A method for validating detected code modulated signals transmitted by beacons of a positioning system and received by a receiver comprises as a first step performing measurements for the detected beacon signals. Then, at least one of the detected beacon signals is selected as a calibration signal. In a next step, at least one allowed range for results of measurements for detected beacon signals other than said calibration signal are determined based on measurements for the detected calibration signal and on an available reference position of the receiver. Finally, each detection of a beacon signal for which results of performed measurements are outside of an allowed range is rejected. The invention relates equally to a corresponding receiver, to an electronic device comprising such a receiver, to a device cooperating with such a receiver and to a corresponding positioning system.

Abstract: The invention relates to a method for determining the time of transmission of a signal part of a code modulated signal transmitted by a beacon of a positioning system and received by a receiver of the positioning system. In order to enable such a determination in weak signal conditions, it is proposed that measured subcomponents of the time of transmission of at least two signal parts are compared with corresponding predicted subcomponents in a way resulting in a combined difference for all signal parts. The comparison is performed for a plurality of assumed errors in the predicted subcomponent. The accurate time of transmission of a signal part is then determined based on the determined error value which results in the smallest combined difference. The invention relates equally to a corresponding receiver and to a corresponding positioning system.

Abstract: The invention relates to a method for determining the correlation between a signal transmitted by a beacon and tracked by a receiver and a reconstructed signal expected to be received at the receiver, wherein the received signal and the reconstructed signal are shifted against each other. In order to provide a possibility of compensating residual sinusoidal modulations in the tracked signal, it is proposed that at each shifting position, the samples of the received and the reconstructed signal are multiplied and integrated separately in a plurality of sections. The results are multiplied with a shifted and complex conjugated version of itself. The products resulting in this second multiplication are integrated to receive a single final value for each shifting position. Finally, the maximum final value resulting for the different shifting positions is determined, the shifting position with the maximum value being considered as the shifting position with the maximum correlation.

Abstract: A method for determining the code phase between a code modulated signal 21 received at a receiver and an available replica code sequence which reduces the complexity of time to frequency transform based correlations performs a multiplication (25) between a first vector (23) and a second vector (24) resulting in a third vector (26), which first vector (23) is generated based on the received signal (21) and which second vector (24) is generated based on the replica code sequence, both in an operation including a time to frequency transform. The method further comprises dividing the resulting vector (26) into sections (29) and summing (30) the samples in each section (29) to form a vector (31), upon which a frequency to time transform is performed. The invention relates equally to a corresponding receiver, to an electronic device comprising such a receiver, to a device cooperating with such a receiver and to a corresponding system.

Abstract: The invention relates to a method for determining the correlation phase between a signal received at a receiver and a replica sequence. A matched filter multiplies samples (21) of the received signal with samples (22) of the replica and sums the resulting products to obtain a correlation value for a specific correlation phase. The samples of the received signal and the replica are shifted relative to each other for each correlation phase that is to be checked. In order to reduce the computational load, it is proposed that results obtained in the correlation calculations for one correlation phase are used by the matched filter also for calculations for a subsequent correlation phase. The invention relates equally to a corresponding receiver, to an electronic device comprising such a receiver, to a device cooperating with such a receiver and to a corresponding system.

Abstract: A system for acquiring a received spread spectrum signal having a code component, the acquiring including matching the phase of a replica of the code component to the phase of the received code component and also determining a possible shift in the carrier frequency away from a nominal carrier frequency, the acquiring having an intrinsic bandwidth that is substantially the inverse of a predetermined fraction of a code period and also having a design bandwidth that is a fraction of the intrinsic bandwidth including possibly the entire intrinsic bandwidth, the system including means for performing various correlations over sections of a code period, the number of sections determining the intrinsic bandwidth, and adjusting the design bandwidth to be possibly less than the intrinsic bandwidth, so as to alter the characteristics of the acquisition.

Abstract: The invention relates to a method for determining the time of transmission of a signal part of a code modulated signal transmitted by a beacon of a positioning system and received by a receiver of the positioning system. In order to enable such a determination in weak signal conditions, it is proposed that measured subcomponents of the time of transmission of at least two signal parts are compared with corresponding predicted subcomponents in a way resulting in a combined difference for all signal parts. The comparison is performed for a plurality of assumed errors in the predicted subcomponent. The accurate time of transmission of a signal part is then determined based on the determined error value which results in the smallest combined difference. The invention relates equally to a corresponding receiver and to a corresponding positioning system.

Abstract: The invention relates to a method for determining the correlation between a signal transmitted by a beacon and tracked by a receiver and a reconstructed signal expected to be received at the receiver, wherein the received signal and the reconstructed signal are shifted against each other. In order to provide a possibility of compensating residual sinusoidal modulations in the tracked signal, it is proposed that at each shifting position, the samples of the received and the reconstructed signal are multiplied and integrated separately in a plurality of sections. The results are multiplied with a shifted and complex conjugated version of itself. The products resulting in this second multiplication are integrated to receive a single final value for each shifting position. Finally, the maximum final value resulting for the different shifting positions is determined, the shifting position with the maximum value being considered as the shifting position with the maximum correlation.

Abstract: The invention relates to a method and to devices for determining in a positioning system the time of reception of a beacon signal which was received and tracked by a receiver. In order to enable a re-acquisition of the system time based on a noisy received signal, it is proposed that the method comprises as a first step reconstructing a beacon signal for an interval based on available information. Then, a cross-correlation is performed between the reconstructed signal and the received signal at different relative positions to each other. Next, the time of transmission of the received signal is determined based on information for the reconstructed signal and on the relative position resulting in the maximum correlation value. Finally, a time of reception of said received signal is determined as the sum of the determined time of transmission of the received signal and of a calculated time of flight of the received signal.

Abstract: An N-clock system, for use for example in a ranging receiver using a Kalman filter. The clock system uses N clocks (to save power by using some clocks that consume less power) with a schedule for switching from one clock to another (so that only one clock is on at any instant of time). It uses an N-clock model that, in case of an application using clock 1 for time interval &Dgr;t1, clock 2 for time interval &Dgr;t2, . . . , and clock N for time interval &Dgr;tN, provides a state update equation for updating the N-clock system state (the state components being typically time and fractional frequency). The state update equation results from propagating the state of the assembly of N clocks (providing a single output, i.e. acting as a single clock) forward from interval to interval until the entire interval of &Dgr;t1+&Dgr;t2+ . . . +&Dgr;tN is covered.

Abstract: An N-clock system, for use for example in a ranging receiver using a Kalman filter. The clock system uses N clocks (to save power by using some clocks that consume less power) with a schedule for switching from one clock to another (so that only one clock is on at any instant of time). It uses an N-clock model that, in case of an application using clock 1 for time interval &Dgr;t1, clock 2 for time interval &Dgr;t2, . . . , and clock N for time interval &Dgr;tN, provides a state update equation for updating the N-clock system state (the state components being typically time and fractional frequency). The state update equation results from propagating the state of the assembly of N clocks (providing a single output, i.e. acting as a single clock) forward from interval to interval until the entire interval of &Dgr;t1+&Dgr;t2+ . . . +&Dgr;tN is covered.

Abstract: A method and corresponding apparatus for accurately determining the offset of the carrier frequency of a received signal from a nominal frequency (the offset due to for example Doppler shifting), such as is done in a ranging receiver when acquiring or tracking a signal transmitted by a beacon (such as a satellite) of a positioning system. The method amplifies a conventional correlation by performing a special noncoherent integration of the real and imaginary components of the output of a conventional (coherent) correlation calculation, resulting in a complex phasor having a phase that bears information about the offset of the carrier frequency from the nominal carrier frequency.

Abstract: Method for accounting for factors (such as temperature) causing systematic errors (time-varying or constant) in a clock, such as a clock used in a ranging receiver (for use with a positioning system such as the Global Positioning System), and a corresponding clock system (including a clock and a filter such as a Kalman filter) for providing clock time and error, used for example in a ranging receiver. The invention adds new state vector components to account for systematic error. The process update equation used in the navigation solution is accordingly extended to include the additional components of the state vector.

Abstract: A method and corresponding apparatus and system for solving for the position of a satellite positioning system receiver having a receiver clock with a receiver clock offset and responsive to ranging codes from some number of satellites, the ranging code from each satellite including a navigation component conveying information about the satellite and having a time of flight from the satellite, the method of use in signal conditions where the ranging codes can be baseband processed so that at least a repeating part of the pseudorange for each satellite can be determined. The method includes the system time at arrival, i.e. for example the time or arrival according to GPS time, as an independent variable of the pseudorange function for each of the ranging codes, an independent variable in addition to the receiver position, and solves simultaneously for the receiver position and the system time at arrival.

Abstract: A system, apparatus, and corresponding method for measuring a pseudorange from a ranging receiver to a beacon (such as a GPS satellite). It determines the time of transmission of a target ranging signal fragment (for which the difference in time between transmission and reception is essentially the pseudorange) even in poor signal conditions when the navigation data of the ranging signal cannot be accurately decoded by the ranging receiver. It is based on making either an estimate of the start time for the particular information element of the ranging signal (usually a navigation data bit) beginning just before the target ranging signal fragment (if the quality of the ranging signal allows such an estimate to be made), or (in any case) based on making an estimate of the time corresponding to the start of the code epoch of the ranging signal that just precedes the target ranging signal fragment.

Abstract: A method and apparatus for measuring time related to satellite navigation data messages used with a satellite-based global positioning systems (GPS). A first record of at least a portion of a satellite data message is received at an entity, which is typically a base station of a wireless communication system. The first record is compared with a second record of the same satellite data message (navigation message) received by a GPS receiver. From the comparison, a time is determined indicating when the satellite date message was transmitted (broadcast). The comparison is made in a way that accounts for the only approximate removal of all modulation of the satellite data message by the acquisition and tracking stages of the GPS receiver.

Abstract: A method, corresponding apparatus, and corresponding system for acquiring a received spread spectrum signal, the received signal having a carrier component at a carrier frequency, a code component having a code period, and a data component, the acquiring including matching the phase of a replica of the code component to the phase of the received code component and also determining any shift in the carrier frequency away from a transmitted carrier frequency, the method including the steps of: performing a first acquisition of the received signal so as to provide an approximately estimated carrier frequency and a phase of the replica and also so as to provide a code-wiped and an approximately carrier-wiped signal; and performing a second acquisition of the approximately carrier-wiped signal, the second acquisition including a substep of data wipe-off involving a squaring or similar operation on a signal derived from the approximately carrier-wiped signal; thereby providing a correction to the approximately esti

Abstract: The invention relates to a method for acquiring a receiver (1) into a code modulated spread spectrum signal received by the receiver (1). In the method at least one replica code (r) is used which corresponds to a code used with the modulation having a pre-determined number of chips, and an examination phase is performed, in which a frequency shift of the signal within a selected frequency area is examined, and a code phase of the code used with the modulation is examined. In the method the frequency shift examination is divided into a first estimation phase and a second estimation phase, wherein in the first estimation phase the selected frequency area is divided into a first set of frequencies, and in the second estimation phase a second set of frequencies is examined nearby each frequency of the first set of frequencies.