56 results about "Multipath mitigation" patented technology

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 front end circuit for selectively coupling a first antenna and a second antenna to a transmit chain and a receive chain of a radio frequency (RF) transceiver is disclosed. There is a first power amplifier having an input connectible to the transmit chain of the RF transceiver, a first low noise amplifier having an output connectible to the receive chain of the RF transceiver, and a second low noise amplifier with an input connectible to the second antenna, as well as an output connectible to the receive chain of the RF transceiver. A first matching and switch network is connected to the first antenna, the output of the first power amplifier, and the input of the first low noise amplifier. Transmit signals from the first power amplifier and receive signals from the first antenna are selectively passed to the first antenna and the first low noise amplifier.

A receiver utilizes an array of complex accumulation registers to form an image of the average chip shape or, as appropriate, chip edge shape, of the received signal over a specified period of time as a time series of complex power measurements. The receiver divides the length of the chip into a plurality of ranges, or “bins, and, as appropriate, extends the bins to cover additional chips or portions thereof.” When a sample is taken, the receiver enables the respective registers that are associated with the corresponding bin or bins, and the respective registers then accumulates the associated power measurement. The receiver uses the accumulated measurements from selected registers and/or selected groups of registers, to produce the correlation values that are needed to perform one or more correlation techniques and/or one or more multipath mitigation techniques. As appropriate, the sizes and/or starting points of the bins, and/or the selections of the bins for the various groupings may be altered, to change the spacings, locations, and so forth to which correlation values correspond.

A multipath mitigation method consists of locating a multipath-invariant (MPI) point of an ideal autocorrelation function and measuring the distance between the MPI point and DLL. The same MPI point is located in a received correlation function, and the distance between the point and the DLL, now affected by multipath, is measured. The difference between the ideal distance and the actual distance is the code tracking error resulting from multipath. The error is subtracted from the computed pseudorange or used to control the DLL. The method can be used to reduce the effects of all types of tracking error sources, such as signal transmission failure or code noise.

Methods for determining a LOB of one or more user equipment (UE) in a wireless system employing Time Difference of Arrival (TDOA) is described. TDOA techniques are based on estimating the difference in the arrival times of reference signals from multiple receivers or from multiple emitters to a receiver. A particular value of the time difference estimate defines a hyperbola between the two receivers on which the handset may exist. When the distance between the receiving antennas is small relative to the distance of the emitter source (the handset) being located, then the TDOA is equivalent to the angle between the baseline of the sensors (receivers antennas) and the incident RF energy from the emitter. If the angle between the baseline and true North is known, then the line of bearing (LOB) and/ or angle of arrival (AoA), can be utilized to determine the location of the UE.

Systems and methods for receiving ADS-B messages in environments where multipath propagation corrupts the messages or blocks the reception of the messages. An exemplary system combines RF signal processing and digital signal processing techniques to make it possible to receive ADS-B messages in the presence of multipath reflections from nearby structures and/or farther out structures. The system uses an array of horizontally spaced antennas. The RF signals from the antennas are combined by the receiver so as to form a set of beams with different azimuth antenna patterns to increase the probability that the multipath does not combine destructively with the line-of-sight path in at least one of the beams. This effectively removes multipath reflections where the delay of the multipath relative to the line-of-sight path is less than 100-200 nanoseconds. The system is also configured to remove multipath reflections with greater delays relative to the line-of-sight path.

Disclosed is a method and apparatus for multipath mitigation using an antenna array. An antenna array made up of a plurality of antennas is used to receive satellite signals from satellites. Various configurations of antenna arrays is disclosed, including a linear vertical antenna array and a horizontal antenna array in which the antenna elements are located in a horizontal plane. A switch sequentially connects each of the antenna outputs to a single processing path to generate a common additive signal. The common additive signal is provided to satellite channel processors, each of which processes the signals from an associated satellite. A phase shift correction signal associated with each of the antennas is generated and synchronously applied to a carrier phase reference signal. A blocking signal may be applied to the satellite channel processors in order to block the processing of signals from an unwanted satellite.

A method and system for determining a position of a mobile device in an indoor environment by an access point is provided. The method includes obtaining identity information of the mobile device. The method includes extracting signal characteristics of the mobile device corresponding to the identity information. Further, the method includes determining the position of the mobile device based on the signal characteristics of the mobile device. The position of the mobile device is determined based on the signal characteristics of the mobile device received from a plurality of access points along with the information of the plurality of access points such as location information and identity information of the access points. The determined position is sent to the mobile device. The access point implements robust multipath mitigation algorithms while determining the position of the mobile device as there is no battery power limitation at the access point.

A method for mitigating the effects of multipath errors in GNSS devices is provided. Signals from GNSS satellites are received. Image data from an image sensor is received. Orientation data from an orientation sensor is received. The orientation data describes the orientation of the image sensor. Obstruction data is determined based on the image data. The obstruction data includes an obstruction region that indicates the sky in that region is obstructed by a structure. Based on the orientation data, obstruction data, and GNSS satellite location data, the position of GNSS satellites with respect to the obstruction region is determined. The location of the GNSS device is determined based on signals from some of the GNSS satellites and the position of GNSS satellites with respect to the obstruction region.

The invention relates to a method and a system for modeling I-UWB (Impulse-Ultra Wide Band) signal multipath transmission characteristics in an indoor visual range environment. The method comprises the following steps: dividing the I-UWB multipath signals into two confirmed clusters, each of which is provided with random arrival multipath rays; inputting the confirmed parameter which includes a multipath gain Alpha 0,0 of the initial ray of the first cluster, a multipath gain Alpha 0,1 of the initial ray of the second cluster, and the relative time delay Tm of the first and the second clusters; inputting the statistical parameters which includes the multipath arrival factor Lambada, the damped exponential Gamma of the multipath mean power and the logarithmic normal distribution standard deviation Sigma of the multipath gain of all the multipath rays which arrive subsequently in each cluster; initializing the functions of logarithmic normal distribution and exponential distribution; generating the first cluster and the second cluster; sorting the arrived multipath rays by the time sequence; and outputting the channel impulse response. The invention realizes the simplified I-UWB signal multipath transmission model, which has higher forecasting accuracy and is suitable for the indoor visual range environment without a plurality of environment topological data.

An improved GNSS or GPS receiver with a code-tracking loop comprising a plurality of correlators, arranged to extract a plurality of samples of the autocorrelation function of the C/A code, and a discriminator performing linear regression on both sides of the autocorrelation peak, to determine the autocorrelation peak position at the crossing point of two straight lines. The lines are independently adapted to the sides of the correlation peak and, therefore, the receiver can handle well multipath situations, in which the correlation peaks are distorted.

A filter circuit is provided having multipath interference mitigation. The filter includes a signal path extending from an input to an output. The signal path includes a conductive path and a ground. A pass band filter is disposed along the signal path between the input and the output. The pass band filter passes a first frequency spectrum in a provider bandwidth, and attenuates a second frequency spectrum in a home network bandwidth. The filter circuit further includes a multipath interference mitigation leg operatively branched from the signal path. The multipath interference mitigation leg increases a return loss of the home network bandwidth. A frequency response of the filter circuit is characterized by an insertion loss characteristic between the input and the output being less than 3 dB in the provider bandwidth, and more than 20 dB in the home network bandwidth. The frequency response is further characterized by a return loss characteristic at the output being more than 10 dB in the provider bandwidth and home network bandwidth.

This FDsmooth™ frequency domain code multipath mitigation technique for real-time application. Firstly, a multipath spectral estimation technique is used to provide multipath frequency spectrum analysis, which was used to bound the frequency domain region for mitigation; either a multipath model or spectral estimation on the GNSS observable data can be accomplished Secondly, a code-minus-carrier (CmC) analysis exposes the major code multipath error and its frequency spectrum, which was the basis for operation; Thirdly, a code multipath correction was formed and applied to mitigate the multipath error in the GNSS code measurement. Both the multipath mitigated code measurement and the carrier phase measurement can be utilized for the user solution, which improves performance. The technique is well suited for ground-based applications where the multipath fading frequency can be well predicted, as well as, for mobile user applications where this multipath frequency can be estimated using a spectral estimation technique.

A system and method for optimally combining multi-path signals is presented. A first signal is received that traveled a first path from a transmitter to a receiving location and a second signal is received that traveled a different second path from the transmitter to the same receiving location. The paths are different so that the first and second signals contain the same signal data but the first signal has a first distortion that is different than a second distortion in the second signal. According to an objective function, the method adaptively generates a first weight value and a second weight value. The first and second weight values are applied to the respective first and second signals to produce respective first and second weighted signals. The first and second weighted signals are linearly combined producing a combined signal with a combined signal degradation.

An apparatus for receiving positioning signals comprises an antenna configured to output a plurality of antenna signals and a multipath compensation module for detecting multipath interference, and if multipath interference is detected, selecting one or more of the antenna signals and combining the selected one or more antenna signals to obtain a compensated signal. The antenna is arranged to distinguish between ones of the positioning signals received at different incident angles, and each antenna signal includes ones of the positioning signals received in a predetermined range of incident angles. The multipath compensation module may determine whether multipath interference is present in each antenna signal, and may not select any antenna signals which include interference when selecting the antenna signals to be combined. The gain of each antenna signal may be adjusted before the signals are combined, to maintain the noise power of each antenna signal below a predetermined limit. The phase of each antenna signal may be adjusted before the signals are combined, to reduce phase differences between the antenna signals.

A GNSS receiver includes a RF front end for receiving GNSS ranging signals, a navigation processor for calculating location from the ranging signals, and a repository of static data. The navigation processor includes the static data in the location calculation. Examples of static data include a digital elevation map, coordinates of tunnel entrances for use when the receiver resumes reception of the signals upon exiting a tunnel, and descriptions of structures in sufficient detail to enable multipath mitigation.

A method of, and apparatus for, determining position, comprises a receiver ( 14 ) receiving a signal from a remote transmitter ( 22 ) whose position has to be determined. The Fourier transform of a power spectrum density of the received signal is determined and a check is made to see if a line-of-sight (LOS) signal is present. If so, a multipath mitigation technique is implemented to identify the LOS signal and once identified the position of the remote transmitter is determined by deriving the propagation time of the LOS signal. Current can be saved by inhibiting the multipath mitigation technique in the absence of detecting a LOS signal. In one embodiment the presence or absence of the LOS signal is determined by dividing the magnitude of the peak at zero frequency by the maximum magnitude of all the other peaks and if the answer is less than unity, LOS is not present.