230 results about "Carrier-to-noise ratio" patented technology

A receiver for continuous carrier phase tracking of low carrier-to-noise ratio (“CNR”) signals from a plurality of radio navigation satellites while the receiver is mobile. The receiver may have: a radio frequency (RF) front-end that provides satellite data corresponding to signals received from the plurality of radio navigation satellites; an inertial measurement unit (IMU) that provides inertial data; and a processor circuit in circuit communication with the RF front end and the IMU, the processor circuit being capable of using satellite data from the RF front-end and inertial data from the IMU to perform continuous carrier phase tracking of low CNR radio navigation satellite signals having a CNR of about 20 dB-Hz, while the receiver is mobile. The receiver may be a GPS receiver for continuous carrier phase tracking of low-CNR GPS signals.

Techniques for measuring the carrier to noise ratio (CNR) in a received digital signal are disclosed. The methods can operate on a received digital signal, such as a layered modulation signal used in a satellite television system. The CNR measurement can be made at the output of a carrier recovery loop or a timing recovery loop in a demodulator. Alternately, the CNR measurement can be made when the received signal is digitized in an analog to digital (A/D) converter at base-band by the demodulator.

The invention discloses a new method for RAIM (receiver autonomous integrity monitoring) based on a satellite selecting algorithm in a multimode satellite navigation system. The method comprises the steps of first determining space position information of satellites according to a navigation message and eliminating satellites with a small elevation angle according to a shielding angle; determining an observation matrix including only one clock correction item according to clock correction conversion factors in the navigation message; selecting p satellites from N visible satellites so as to be used for positioning calculation of a receiver, acquiring a satellite combination, which enables the GDOP (geometric dilution of precision) to be minimum, through the satellite selecting algorithm to act as calculating satellites, and determining a weight matrix in WLS (weighted least squares) according to parameters such as the carrier-to-noise ratio, the loop bandwidth, pre-check integral time and the like of satellite signals; carrying out RAIM availability detection according to a false alarm rate and a missed alarm rate which are preset by the receiver, and calculating a pseudo-range residual error threshold value after positioning according to the false alarm rate and a degree of freedom in Chi-squared distribution; carrying out global detection at first, then carrying out local monitoring in a circumstance that a fault satellite exists, determining calculation satellites again through satellite selection, and finally carrying out positioning calculation through selecting satellite combinations within the threshold value. The method disclosed by the invention is simple, high in fault recognition rate, not only applicable to multi-mode and multi-fault satellite navigation systems, but also applicable to single-mode and multi-fault satellite navigation systems, thereby providing new ideas for carrying out RAIM by a modern GNSS (global navigation satellite system).

The invention discloses a satellite signal vector tracking method based on SINS/GPS deep integration data fusion. In the method, compensation is carried out on inertia element errors through channel filter information fusion, SINS/GPS deep integration navigation data fusion and an SINS system based on an SINS/GPS deep integration navigation system; and position and speed parameters of a current computation period are corrected to obtain accurate navigation parameters and generate local inference signals as well as keep the tracking for all visual GPS satellite signals; and a loop formed by channel filters and a main filter is utilized to complete the vector tracking and integration navigation information processing to the GPS satellite signals. The invention has excellent noise inhibitioncapacity and dynamic tracking performance, can ensure the navigation accuracy and the reliability of an integration system during the temporary interruption of the GPS satellite signals, and can maintain better pseudo code phase and carrier frequency tracking property in an environment with low carrier-to-noise ratio.

A system and method for determining the attitude of a platform is provided. The method includes: (a) Searching and scanning for one or more GPS satellite(s) to determine initial platform position; wherein a single directionally steered antenna scans for the GPS/GNSS satellite; (b) pointing and scanning the antenna to GPS/GNSS satellite to determine a first angular measurement of a direction of a GPS/GNSS signal; (c) measuring carrier to noise ratio of the GPS/GNSS satellite; (d) dithering the single directionally steered antenna to obtain an angular measurement relative to an antenna pattern bore-sight reference; (e) repeating steps (b)-(d) to determine a second angular measurement of the direction of a second GPS signal; (f) determining the attitude error of the platform using the first and second angular measurements; (g) updating the platform position and attitude.

A method and apparatus for matching compressed video data under a wireless fading environment are disclosed. The apparatus includes an encoder for encoding and outputting the video data as a compressed bit stream, a channel error measurement unit for measuring Signal-to-Noise Ratio (SNR) or Carrier-to-Noise Ratio (CNR) of a wireless channel, and an encoder optimization module for determining if the current fading is slow fading or fast fading. A control signal is output to reduce a frame transmission ratio or to change the quality of the vide data if it is determined that the current fading is slow fading. Another control signal is output to adjust the size of a data output buffer of the wireless channel if it is determined that the current fading is fast fading. The apparatus also includes a temporal Scalable Video Coding (SVC) selector 24 and an SNR SVC selector 22 for selecting the frame transmission ratio or the bit rate according to the control signal output from the encoder optimization module, to provide a frame selection signal or a bit rate selection signal to the encoder.

An optical transmission system and method may control optical signal transmission in an optical network, such as a passive optical network (PON), to reduce degradation of one or more optical signals traveling over the same optical waveguide. In particular, optical signal transmission may be controlled to reduce carrier to noise ratio (CNR) degradation of an optical signal (e.g., a multichannel video signal) resulting from the effects of stimulated Raman scattering (SRS) and/or double Rayleigh backscattering (DRBS). The CNR degradation may be reduced by controlling transmission of one or more of a plurality of optical signals in the optical network based on various parameters affecting the contribution to CNR degradation by SRS and/or DRBS and affecting the performance of the optical transmission system. The optical signal transmission may be controlled by adjusting a preemphasis and/or transmitted power of the optical signal(s).

The invention discloses a GNSS carrier loop circuit tracking method based on a stochastic resonance algorithm. According to the invention, the signal to noise ratio of receiving signals is increased by integral accumulation and multiplication feedback treatment on input signals; rough tracking of frequency of the receiving signals is performed by utilizing a second-order frequency locking loop; and precise tracking is performed on the signals subjected to rough tracking by adopting a third-order phase locking loop. Therefore, precise carrier loop circuit tracking on the GNSS signals is realized in a low carrier-to-noise ratio. According to the invention, an advantage of the stochastic resonance algorithm in an aspect of improving the signal to noise ratio and an advantage of anti-interference and robustness of the cooperation of the second order frequency locking loop and the third-order phase locking loop are integrated effectively. The method is simple in hardware implementation and stable in signal tracking, and can realize stable and reliable tracking of highly dynamic satellite signals by a receiver in a severe environment.

A method for detecting observed quantity validity in a navigation receiver mainly includes: S1. calculating a carrier-to-noise ratio of a signal; S2. judging stability of carrier tracking; S3. Extracting carrier Doppler frequency observed quantity of a carrier tracking loop and pseudo-range observed quantity of a code tracking loop in each epoch; S4. utilizing the two kinds of observed quantity to calculate a pseudo-range difference of corresponding two successive epoch respectively; S5. calculating a difference value of the pseudo-range differences and comparing with a threshold, thereby judging whether pseudo-range observed quantity of the current epoch is correct; S6. summing a difference of delta pseudo ranges of the current epoch and differences of delta pseudo ranges of n previous epochs, comparing with a threshold, and judging whether pseudo range observed quantity is correct; and S7. performing the abovementioned steps on each satellite which keeps tracking, collecting all signals of satellites whose observed quantity is judged to be correct, and inputting the signals to a positioning resolving module. The method provided by the invention does not need redundant information, and solves the problem of positioning stability of a receiver in complex environment with a relatively small calculated amount.

A satellite interference canceling system cancels the interference between two or more signals received by a satellite receiver. The signals can be two signals experiencing cross polarization interference or signals that experience interference from other satellite signals. Gain and phase are applied to the received signals and then combined with the other signals to result in cancellation by subtraction. The gain and phase values needed to cancel the interference are derived from measurements of carrier-to-noise ratio (C/N) as an indication of the interference level. The C/N can be measured in the set-top box indoor unit. Coherency restoration is performed in receivers that downconvert the signals before performing interference cancellation.

A read-only recording medium for achieving a carrier-to-noise ratio (CNR) using a super-resolution near-field structure (Super-RENS) on which information has been prerecorded includes a substrate having the information recorded on its surface, a reflective layer formed from a phase change material on the substrate, a first dielectric layer formed on the reflective layer, and a mask layer formed from metal oxide or nanoparticles on the first dielectric layer.

The invention discloses a code pseudo-range/Doppler combined speed measurement method based on robust variance assembly estimation, which comprises the following steps: firstly, respectively establishing a speed measurement function model and a random model by adopting observation information such as code pseudo-range, Doppler, carrier-to-noise ratio, satellite altitude angle and the like, then adopting a least square robust estimation method to obtain a robust random model capable of inhibiting the influence of gross error, and finally combining a speed measurement function model of code pseudo-range and Doppler with the robust random model to form a combined speed measurement model. According to the method, the limitation that the conventional single-frequency satellite receiver only uses single information to measure the speed can be broken through, the influence of observation gross error can be inhibited, and the robustness, the unbiased property and the stability of the combinedspeed measurement method can be obviously improved.

An object is to provide a method of extracting sound-source information, which method enables the characteristics of fixed points of mapping from filter center frequency to output instantaneous frequency to be detected from instantaneous data, as a value which can be interpreted quantitatively. In a method of extracting sound-source information by use of fixed points of mapping from frequency to instantaneous frequency, instantaneous frequency of each filter (2), (9) is partial-differentiated with respect to frequency by an instantaneous-frequency frequency differentiation circuit (3), (10) to thereby obtain a first value; output of each filter is partial-differentiated with respect to frequency and then with respect to time by an instantaneous-frequency time-frequency differentiation circuit (4), (11) to thereby obtain a second value; and proper weights are imparted to the first and second values and short-time weighted integration with respect to time is performed by a carrier-to-noise-ratio calculation circuit (5), (12) to estimate a carrier-to-noise ratio of each filter. Thus, a carrier-to-noise ratio is obtained, and an estimated value of evaluation value is obtained.

In a spread spectrum transmitter, a number of spread spectrum channel signals are multiplexed into a digital amplitude signal by a multiplexer, and the time-average power of the digital amplitude signal is determined by an average calculator. The digital amplitude signal is interpolated by an interpolator, scaled according to a first scale factor by a bit shifter and converted to an analog amplitude signal by a D/A converter. The analog amplitude signal is then scaled according to a second scale factor in a gain controlled amplifier. The first and second scale factors are complementarily varied by a control circuit according to the output of the average calculator so that the carrier-to-noise ratio of the transmitter is maintained substantially constant regardless of the varying power level of the multiplexed signals.

It is becoming increasingly important to improve data throughput in wireless networks. By transmitting data simultaneously at different modulation amplitudes and/or using different code strengths, terminals having different carrier to noise ratios are able to decode the different amplitude levels with varying degrees of success. This allows distant terminals to receive low data rate transmissions at high modulation levels or code rates while nearer terminals can use additional capacity in the transmission by receiving lower level modulation signals or code rates. In this way, distant terminals do not degrade overall network performance. By arranging for terminals to acknowledge receipt of data, re-transmission at different modulation levels or code rates may be carried out by the base station in order to improve performance in the presence of noise without a priori knowledge of the carrier to noise ratio for a particular terminal.

The invention relates to a high precision GNSS receiver, which comprises a levorotatory and dextrorotary circular polarization antenna, a first radio frequency front end module and a second radio frequency front end module with a local clock, a signal following module and a CPU. The signal following module comprises a satellite capturing unit, a first satellite following unit, a second satellite following unit and an interface unit. A capturing control module, a text demodulation module, two loop following modules, two initial data measuring modules, an availability choosing module, a position resolving module and an interface protocol module are arranged in the CPU. The availability choosing module obtains the pseudo range and the carrier-to-noise ratio data of levorotatory signals and dextrorotary signals, analyzes and chooses the weak initial data of multipath signals and transmits to the position resolving module for final position resolving. The invention compares and analyzes the levorotatory signals and the dextrorotary signals, alleviates the multipath influence on data source, ensures the GNSS receiver obtains high position precision, can improve the multipath influence alleviating effect based on the traditional multipath alleviating technology, has strong structural expansibility and can realize flexible framework configuration.

Disclosed is a technique that can provide one or more countermeasures against spoofers. A beamformer can control an antenna pattern of a CRPA to generate a survey beam. The survey beam is swept across space to determine a characteristic signature based on carrier-to-noise ratios (C/No) for particular space vehicle signals. Matching C/No signatures can be used to identify the existence of spoofers and invoke a countermeasure, such as nulling.

A differential method of improving the carrier to noise ratio of optically transmitted amplitude modulated signals without affecting the fidelity of the transmitted signals is disclosed. The disclosed method improves over prior art methods by utilizing a single transmission fiber transmitting two wavelengths that are modulated out of phase by a single Mach Zehnder type modulator. The received light is separated into two components at two wavelengths and each wavelength is received by a photodetector. The two photodetector outputs are differentially combined to produce an output with improved signal to noise ratio resulting in improved bit error rates in digital transmissions. The invention is also useful in fiber optic analog transmission systems such as those used to distribute AM-VSB Cable Television programming, wherein the differential method improves the carrier to noise ratio without increasing the nonlinear components in the signal.

The invention discloses a repeater deception type jamming system and a jamming method thereof. The repeater deception type jamming system comprises reconnaissance receivers, a digital analog converter, a frequency converter, a combiner, a power amplifier, a transmission system, a jammer delayer and a jamming transmitter, wherein the frequency converter comprises an up-converter and a down converter; the combiner comprises an upper combiner and a lower combiner; eight reconnaissance receivers are provided, and each reconnaissance receiver comprises a large-diameter reflector antenna and an automatic tracking system; the transmission system adopts a wire transmission mode or a wireless transmission mode; the jammer delayer is a fixed tapped delayer with a plurality of tap positions, and a delay array is composed by a CPLD (Complex Programmable Logic Device) for each jammer delayer. The repeater deception type jamming system and the jamming method have the advantages that the jammer is small in interference emission size and light in weight, the large-diameter reflector antennas are adopted to obtain the high gain, the carrier to noise ratio of a GPS signal is improved, despreading is not needed, a sending part and a receiving part are insulated and connected by the transmission system, the insulation difficulty of the sending and the receiving is avoided, the remote transmission effect is also achieved, and a far effective jamming distance can be realized.

The invention discloses a compatibility capturing method of a multi-mode GNSS (Global Navigation Satellite System) combination receiver. The capturing method comprises the following steps of: carrying out corresponding capture process on a satellite signal within coherent integration accumulation time and non-coherent integration accumulation time; adopting a fuzzy logic algorithm in the capture process, dynamically adjusting the coherent integration accumulation time and the non-coherent integration accumulation times according to a carrier-to-noise ratio and a carrier speed; and within the coherent integration accumulation time, carrying out the secondary sampling on a middle frequency signal of the acquired satellite signal, i.e. all data are decomposed into a plurality of groups, and the data points in each group are at one pseudo-random code element, and subsequently the Fourier transform, the Fourier inversion, the DCT (Discrete Cosine Transformation), the IDCT (Inverse Discrete Cosine Transform), the mode value square and threshold judgment process are carried out. With the adoption of the capturing method, the defects that signals cannot be captured as an existing capturing method is low in sensitivity and likely to be interfered are overcome, and satellite signals can be captured normally when a GNSS signal is shielded and strong environment noise exists.

A laser bias preconditioning methodology is provided, and an implementation of that methodology, that improves the carrier-to-noise ratio of analog CATV signals sent over an optical transmission medium. The bias preconditioning methodology causes the laser bias current to be continuously varied to track an envelope of the carrier signal.