86results about How to "Reduce multipath effects" patented technology

A particle detection system (100), such as an active video smoke detection system, includes at least one illumination means (102) for directing a beam (106) of radiation through at least part of the air volume being monitored (110), an image sensor (104) is positioned to capture images of at least part of a beam (106) from illumination means (102); and means to analyse (107) the captured images to detect the presence of particles within the volume. At least 29 different aspects are described for improving the sensitivity, usability, and robustness of particle detection. These include, for example, configuring illumination means (102) to create a curtain of light or a rapidly-scanned beam across the air volume (110), and configuring a reflector to steer or change direction of a beam reflected from illumination means (102).

A multi-protocol, multi-band array antenna system may be used in Radio Frequency Identification (RFID) system reader and sensory networks. The antenna array may include array elements with an integrated low noise amplifier. The system may employ digital beam forming techniques for transmission and steering of a beam to a specific sensor tag or group of tags in an cell. The receive beam forming network is optimized for detecting signals from each sensor tag. Narrow and wideband interferences may be excised by an interference nulling algorithm. Space division multiplexing may be used by the antenna system to enhance system processing capacity.

An antenna assembly includes at least two active or main radiating omni-directional antenna elements arranged with at least one beam control or passive antenna element used as a reflector. The beam control antenna element(s) may have multiple reactance elements that can electrically terminate it to adjust the input or output beam pattern(s) produced by the combination of the active antenna elements and the beam control antenna element(s). More specifically, the beam control antenna element(s) may be coupled to different terminating reactances to change beam characteristics, such as the directivity and angular beamwidth. Processing may be employed to select which terminating reactance to use. Consequently, the radiator pattern of the antenna can be more easily directed towards a specific target receiver/transmitter, reduce signal-to-noise interference levels, and/or increase gain by using Radio Frequency (RF), Intermediate Frequency (IF), or baseband processing. A Multiple-Input, Multiple-Output (MIMO) processing technique may be employed to operate the antenna assembly with simultaneous beam patterns.

A method and apparatus for mitigating multipath effects in a satellite signal receiver is described. In one example, measured pseudoranges are obtained from the satellite signal receiver to a plurality of satellites. For each measured pseudorange: an expected pseudorange is derived from a sequential estimation filter in the satellite signal receiver. The measured pseudorange and the expected pseudorange are differenced to compute a pseudorange residual. The measured pseudorange is applied to the sequential estimation filter only if the pseudorange residual is within a window.

System and method to determine the location of a receiver in a multipath environment are provided. The received signal is correlated with the reference signals associated with the transmitting sources. Each correlation function is processed to derive various types of signal constraints, such as probability densities and uncertainty regions or intervals. In some embodiments, these constraints are for the code-phases and the Doppler frequencies. These signal constraints are transformed into constraints on the receiver variables and then fused together into a unified receiver constraint. A-priori constraints, such as constraints on the location of the receiver or the timestamp, may be incorporated into the unified receiver constraint. Some embodiments estimate a location based also on the estimated Doppler frequency. The constraints used by the invention are based on models of multipath effects and are geared towards mitigating these effects. In one of these models, a probability density for code-phase is obtained by convolving a gaussian distribution with an exponential distribution that describes the extra delay introduced by multipath. Another approach is based on identifying outliers in the set of code-phases. In other approaches, uncertainty region constraints and probability densities are combined. The present invention achieves faster and more sensitive signal acquisition and higher location accuracy in multipath environment, without compromising performance in other environments.

The embodiment of the invention discloses a physical-layer-based method and device for realizing indoor positioning of a wireless network. The method comprises the steps of: acquiring the channel state information of a plurality of subcarriers of a target node based on an OFDM (Orthogonal Frequency Division Multiplexing) platform of a physical layer; calculating signal intensity according to the channel state information of the plurality of subcarriers; optimizing a propagation path loss model of an indoor environment according to the signal intensity; calculating the distance between each sending party and each receiving party according to the optimized propagation path loss model; and positioning the target node according to the signal intensity and the distances. In the embodiment of the invention, under the condition that an indoor environment multipath effect is ubiquitous, the precise channel state information is utilized to calculate the signal intensity in the wireless local area network so as to further realize the indoor positioning, the frequency diversity of the channel state information is utilized to reduce multipath attenuation and reduce the influences of the indoor environment multipath effect and frequency selective attenuation, and thus, the position information of the target node can be calculated more precisely and the positioning precision is increased.

A receiver operating with satellite navigation signals estimates its position by means of a multiplicity of signals each transmitted by another satellite. A subset of satellites is used to calculate the position estimation and checking the pseudoranges of all received satellite signals that did not contribute to this particular estimate with respect to their consensus with this estimate. The subset with the best consensus is determined by combining the subsets with respect to the consensus with all ranging sources in view. Consensus in this context refers to pseudoranges that coincide in a position solution in a consistent way. The satellites with a bias in pseudorange higher than a threshold are identified as faulty satellites, after knowing all consistent satellites. This identifying information is then used to exclude the faulty satellites for the determination of position, velocity, and time in the receiver.

The invention discloses an underwater sound communication device and a method based on time reversal and orthogonal frequency division multiplexing (OFDM) combined treatment. The underwater sound communication device comprises a signal transmitter, a power amplifier, a transmitting transducer, a receiving hydrophone array, a signal receiver and a signal processor, wherein the signal processor comprises a broadband Doppler estimation and compensation module, a time reversal processing module, an OFDM demodulation module, a channel estimation and compensation module and a frequency deviation estimation and compensation module. In the underwater sound communication device, the space time focusing characteristics of the time reversal are utilized to eliminate the multipath influence of the channel; a pulse channel response length can be shortened by the time reversal so as to reduce the length of an OFDM symbol guard interval and improve the communication efficiency; and because the guard interval is reduced, the length of the OFDM symbol can be shortened so as to enlarge a subcarrier frequency interval. With the method disclosed by the invention, interference among subcarriers can be reduced, and the available rate of the OFDM underwater sound communication is further improved.

A receiver for receiving a navigation signal comprising a carrier modulated by a code modulation function of a given code rate and further modulated by a composite sub-carrier modulation function having first and second components with two different rates both of which arc different to the code rate, the receiver comprising processing means arranged to: generate a first estimate of delay based on the code modulation only; generate a second estimate of delay based on the first component of the sub-carrier modulation only; and generate a third estimate of delay based on the second component of the sub-carrier modulation only; and determine a further delay estimate from the first second and third delay estimates.

The invention discloses a lip language recognition method. The lip language recognition method comprises the steps of transmitting wireless signals directionally so that the wireless signals cover the face of a user; receiving wireless signals reflected by the face of the user, filtering the reflected wireless signals, and obtaining reflected signals of the mouth during the user's mouth motion; segmenting the reflected signals of the mouth, obtaining segmented signals, and obtaining waveform characteristic patterns of the segmented signals; enabling the segmented signals to be reflected signals each time a voice event is sent; comparing the similarity of the waveform characteristic patterns of the segmented signals with all mouth motion characteristic patterns sampled in advance, and reading the voice event corresponding to the mouth motion characteristic pattern highest in similarity. Correspondingly, an embodiment of the invention further provides a lip language recognition system. By the adoption of the lip language recognition method and system, the user's mouth motion can be detected through the wireless signals to achieve lip language recognition, and recognition efficiency and the accurate rate are improved.

Provided is a miniature unmanned plane RTK relative positioning method based on difference air pressure height constraints, comprising: installing GNSS receivers of a same model, antennas, barometric leveling sensors and radio stations both on a reference station and a mobile station; transmitting the GNSS original observed value of the mobile station to the reference station, and performing difference recursion treatment on the original observed value of the reference station; employing an LAMBDA algorithm to determine N baseline vector residence values, respectively calculating the difference vector with a baseline vector floating point solution, and performing ordering again according to the absolute value sum of north and east components; transmitting the barometric height of the mobile station to the reference station through the radio stations, and performing difference with the barometric height of the reference station to obtain a difference height; and successively examining the sky direction component of a baseline vector fixed solution, and determining a relative position if meeting difference height constrains. The miniature unmanned plane RTK relative positioning method can utilize the difference height information of the reference station and the mobile station to discriminate a correct baseline vector fixed solution, does not need to use a measurement type receiver with a multi-path inhibition function, and can be used for low cost RTK application.

A GPS receiver system determines the presence of trackable signals at code delays less than the prompt delay being tracked for a particular, signal and changes the prompt delay to correspond to the smallest code delay having a trackable signal. Trackable signals at large code delays are multipath signals and may be separately tracked to aid in dead reckoning. The trackable signals at code delays not adjacent to the current tracked prompt delay may be tracked in the same channel as the prompt delay so that all satellite channels are continuously evaluated for multipath signals being tracked or a non-satellite specific channel may be used to sequentially step through the satellite signals to evaluate multipath on a satellite by satellite basis.

The architecture of the present invention is premised upon an algorithm involving integration of oblique correlators and RAKE filtering to null interference from other spread spectrum signals. The oblique correlator is based on the non-orthogonal projections that are optimum for nulling structured signals such as spread spectrum signals. In one configuration, space spanned by a first signal associated with a first emitter is orthogonal to an interference space associated with one or more signals of one or more other emitters. RAKE filtering is used to rapidly steer the beam of the multi-antenna system and to mitigate the effects of multipath.

An RFID reader comprises a receiver section for receiving an RF signal and a transmitter section for transmitting an RF signal. The reader is a multicarrier RFID reader and both the transmitted RF signal and the received RF signal comprise at least two frequencies.

The invention relates to the bridge field, especially to a method for pretreating bridge monitoring signals. The method includes pretreating bridge monitoring signals with an EMD decomposition method with added Kriging interpolation, wherein particle swarm optimization (PSO) is employed to optimize related model parameter theta involved in a K-EMD process. PSO has overall optimization capability, prevents signal processing from being optimized partially, and ensures the value is overall optimal.

The invention discloses a signal separation estimation theory-based satellite navigation signal multipath interference suppression method, which mainly relates to a time delay estimation algorithm and a frequency estimation algorithm of a diameter signal and a multipath signal of a satellite navigation system. The method comprises the following steps of: estimating a satellite signal frequency which includes Doppler under the condition that a time delay is unknown, eliminating a fuzzy frequency according to the intermediate frequency value of the satellite signal and prior information in which a Doppler frequency shift range is known, and estimating the time delays of the diameter signal and the multipath signal respectively by using the signal separation estimation theory. By the signal separation estimation theory-based satellite navigation signal multipath interference suppression method, the time delay information and the frequency information of the diameter signal can be directly estimated and the aim of eliminating multipath signal influence can be fulfilled in a multipath environment.

The invention discloses a high-frequency epoch-by-epoch phase difference method for single-frequency GNSS phase stability monitoring, comprising the following steps: using a single-frequency GNSS receiver to perform high-frequency observation on a station point, and calculating the phase difference between adjacent epochs; using the least squares method to detect a station 3D (NEU) coordinate correction number time series within the interval of adjacent epochs under continuous epochs; getting the mean and standard deviation of the NEU coordinate through statistical analysis of the time series; and calculating the anomaly ratio. The phase observation stability of the single-frequency GNSS receiver is evaluated by calculating the continuous observation anomaly ratio using the method. Single-point real-time high-frequency GNSS phase data quality monitoring is carried out based on single-frequency GNSS data. The GNSS phase stability can be evaluated without the need for high-precision clock difference or model correction.