263 results about "Narrow band interference" patented technology

A method and device which dynamically detects, tracks and filters interfering signals with sufficient speed (i.e. within one IS-95 CDMA data frame period, or 20ms and fidelity to eliminate or greatly reduce the deleterious effects of narrow band interferor signals on a CDMA link. When inserted in an RF signal path an Adaptive Notch Filter (ANF) detects narrow band interferors above a threshold level within the CDMA signal. Detection is accomplished by continuous scanning of a preset excision band, e.g. a specified narrow band associated with an AMPS system. Detected interferors are then automatically acquired and suppressed. This is achieved by electronically placing a rejection notch at the frequency of the interferors. Multiple notch filters may be used to simultaneously suppress multiple interferors. In the absence of interferors a bypass mode is selected allowing the RF signal to bypass the notch. Upon detection of an interferor, a switch is made to a suppression mode where the interferor is steered through a first notch section and suppressed. Alternatively, an external control line may be used to select the bypass mode so that the signal is allowed to pass the notch section, regardless of interferer content.

A spread spectrum receiver and method having narrow-band interference rejection of narrow-band jamming signals using digital signal processing frequency domain techniques. The method performed in the receiver includes transforming the received signal to a frequency domain signal and identifying narrow-band interference components in the frequency domain signal; suppressing the identified narrow-band interference components by excising the identified narrow-band interference components from the frequency domain signal to produce an interference excised signal in the frequency domain, and storing in a memory frequencies corresponding to the identified narrow-band interference components; synchronizing a receiver code to a transmitter code in the frequency domain using the interference excised signal; generating coefficients for a time domain filter that includes notches at the frequencies corresponding to the excised narrow-band interference components and that jointly despreads and rejects narrow-band interference from the excised frequencies; applying the coefficients generated in the preceding step to the time domain filter, and despreading and filtering in real time in the time domain the received signal using the applied coefficients.

A method and device for eliminating narrow-band interference in spread spectrum system, wherein the method comprises the steps of: extracting N sampling points of the data to perform frequency spectrum transform each time and obtaining N points of data; getting the energy sum of individual data after M times of transform, obtaining N energy values, in which M≧1; removing partial excessive large values from N energy values and averaging the rest, then calculating the threshold value for interference determination based on the average value; obtaining the identification information of the points that have energy values exceeding the threshold value from N energy values and performing interference suppression for the data of corresponding points after frequency spectrum transform and finally outputting the data after frequency spectrum inverse transform. The device comprises a frequency spectrum transform unit, an interference elimination unit, an interference elimination control unit and a frequency spectrum inverse transform unit. The present invention could exactly distinguish interference data from non-interference data and effectively suppress narrow-band interference.

The invention discloses a signal channel training method based on a beacon frame, which includes: performing initial synchronous search for the beacon frame and computing initial estimation of frequency offset of a sampling clock after access terminal equipment is powered on; starting tracking estimation and compensation of frequency offset of the sampling clock based on initial estimation of frequency offset of the sampling clock; estimating in-band narrow-band interference and computing the coefficient of a notching filter according to the frequency point position of the in-band narrow-band interference; performing second power control processing for digital baseband signals processed by means of low-pass filtering and notching filtering; starting coarse carrier frequency offset estimation and compensation; starting fine carrier frequency offset estimation and compensation; starting signal channel frequency response estimation; and leading a receiver to enter a signal channel condition tracking state. The invention further discloses a signal channel training receiver device based on the beacon frame. The success probability of synchronous detection for the beacon frame can be increased, and signal channel estimation precision can also be improved.

The invention discloses a method for realizing a high anti-interference unmanned aerial vehicle remote control data link, which comprises two steps of data transmitting and data receiving, wherein the data transmitting comprises the steps of performing serial-parallel conversion, performing M-ary spread spectrum on parallel N-channel binary baseband information to obtain N-channel M-ary spread spectrum information, performing digital modulation, controlling a frequency hopping source to generate frequency hopping carriers by frequency hopping sequences and performing data sending; and the data receiving comprises the steps of receiving transmitted signals for bandpass filtering, synchronizing the system and dehopping, performing M-ary despreading, performing digital demodulation and performing serial-parallel conversion. The method adopts multi-channel M-ary spread frequency technology, and has higher information transmission efficiency compared with single-channel M-ary spread spectrum with high information transmission; the method adopts multi-channel M-ary spread spectrum, and each channel adopts frequency hopping sequences with different lengths and different code rules so that each channel has higher anti-interference ability; and the method adopts the combination of spread spectrum technology and frequency hopping technology, has the ability of resisting narrow-band interference and near-far effect of a frequency hopping communication mode, and meets the requirement of high interference resistance.

The invention discloses an LFM (linear frequency modulation) signal detecting method under a strong interference source environment, belonging to the technical field of the signal processing. The LFM signal detecting method comprises the following steps of: firstly, carrying out time domain separation on received multi-component signals and various interference source signals by employing a array receiving time domain complex blind separating technology, decomposing the signals into multiple paths of time domain receiving signals; then respectively judging the signal and the interference of each path of time domain receiving signals respectively; selecting a broadband Gaussian noise interference source signal according to the broadband receiving system of an electronic reconnaissance receiver and the signal spectrum width characteristic represented by a second-order central moment of the spectrum density function; extracting the similarity judgment of the signal spectrum sequence via a cloud model feature vector and selecting a co-frequency narrow-band interference source signal; and at last, carrying out detection and parameter estimation of the multi-component LFM signal on remaining time domain separating signals by Wigner-Hough conversion respectively. The method can be used for effectively extracting single-component linear frequency-modulating signals in the multi-component signals and performing the accurate parameter estimation on the single-component linear frequency-modulating signals.

The invention relates to systems for receiving a digital radio signal and, more particularly, to receivers of radio signals, coded with a pseudo-noise sequence, which are used in global positioning system GPS (USA) and GLONASS (Russia), allowing a compensation effect for the narrow-band interference by using a device, controlled by the processor, with an automatic gain control, multilevel analog-to-digital converter, and additional correlation channel for detection of sinusoidal interference consisting of the digital generator having quadrature mixers and accumulators. Information from output of the of accumulators is read by a processor, in which is detected the presence (or absence) of interference, and the amplitude is evaluated. Therefore, the processor generates control signal directing amplification in the device using an automatic gain control.

A received signal whose frequency band is spread in a spread spectrum system is subjected to fast Fourier transform processing to detect an interference signal, based on a result of the detection, a frequency characteristic of a frequency variable type notch filter for eliminating a narrow-band interference signal is controlled so that a narrow-band interference signal is eliminated from the received signal, whereby a spread spectrum communication system receiving device resistant to narrow-band interference can be provided by a simple configuration.

An OFDM receiver 1 receives an OFDM signal. The OFDM signal is composed of a useful symbol period for transmitting a signal relating to data and a guard interval period for transmitting a signal that is the same as part of the signal transmitted in the useful symbol period. An interference wave cancel circuit 18 cancels a narrow-band interference wave component relating to a narrow-band interference wave from the OFDM signal, and outputs the OFDM signal from which the narrow-band interference wave component has been canceled, as a cancel signal. The correlation detection circuit 20 calculates a correlation between a cancel signal output from the interference wave cancel circuit 18 and a cancel signal which has been delayed by the useful symbol period delay circuit 19 by the useful symbol period.

An Apparatus for non-linear per-bin adaptive equalization in orthogonal multi-carrier data transmission systems with the Nyquist sub-channel spectral shaping and T/2 staggering of in-phase and quadrature components is disclosed. A previously introduced linear equalization embodiments are augmented by up to three, or more decision feed-back filters, to improve performance in presence of narrow-band interference (NBI) in wire-line and wire-less data transmission systems, and to enable exploitation of implicit diversity of multi-path fading channels, both with and without transmitter-end pre-coding. Adaptation properties of per-bin DFE equalization are analyzed by computer simulation for an intermediate number of constituent sub-channels. BER performance comparison between the conventional Orthogonal Frequency Division Multiplication-(OFDM) and (Orthogonal Quadrature Amplitude Modulation (OQAM)-based multi-carrier systems of similar modulation/demodulation complexity and transmission latency is provided and the potential advantage of using spectrally well shaped orthogonal sub-channels in wireless applications is demonstrated.

The invention provides a CNN (convolutional neural network) based method for identifying communication interference signals at large dynamic SNR (signal to noise ratio), relates to the field of interference signal type identification and aims to solve the problems that the conventional interference signal type identification method is high in feature extraction difficulty, complex in form and low in accuracy of interference signal classification due to adoption of artificial extraction of features such as statistics, high-order cumulant and the like. With adoption of the method, totally 15 interference signals including 5 common interference signals and pairwise combinations of the 5 interference signals can be identified, the 5 interference signals include an audio interference signal, a same-frequency-band narrow-band interference signal, a sweeping interference signal, a rectangular pulse interference signal and a spread spectrum interference signal, and the feature that the interference signals have strong robustness at the large dynamic SNR is extracted by establishing a CNN model; SVM (support vector machine) classifiers for the 15 classes are constructed to classify the 15 interference signals and used for classifying the interference signals.

The invention discloses a space-time two-dimensional narrow band barrage jamming method aiming at phased array radar. The conventional phased array radar controls the narrow band jamming by self adaptation, firstly learns the jamming data received by a radar receiver, and then forms zero point in a jamming direction. Such a conventional self-adaptive treatment method easily generates signal counteraction and is not suitable for motion jamming and fast-varied interstitial jamming, and the zero point depth and width are seriously influenced by the array error. The method for using ultra-low side lobe antenna can effectively resist jamming. But under the prior art and technological level, excessive side lobe requirements on phased array radar are unpractical. The invention comprises the steps of firstly estimating jamming parameters by a spatial spectrum estimation technique so as to obtain the jamming azimuth and frequency parameters, using relative parameter information to construct a space-time two-dimensional barrage matrix, multiplying the space-time two-dimensional barrage matrix by the received data so as to block the narrow band jamming with a specific frequency in the specific azimuth, and finally realizing space-time two-dimensional narrow band barrage jamming. The advantages of the invention are that the invention can be used for the phased array radar for resisting specific side lobe jamming and main lobe jamming, has small operand, and is easily realized and popularized.

The method of detecting local discharge signal in electric power equipment includes the empirical mode dissociation of acquired original signal, the adaptive filtering treatment on the obtained inherent mode functions of different orders, and final signal reconstruction with the treated new inherent mode functions to obtain the useful local discharge signal with inhibited narrow band interference signal. The method has high adaptive filtering effect and easy parameter setting, and may be used widely in the denoising treatment of local discharge signal in large electric power equipment and similar equipment.

The invention relates to a narrow-band interference restrain method, which comprises: sampling the signal, and converting the sampled time domain signal into frequency domain signal; obtaining the middle value of said frequency domain, and damping the signal that higher than middle threshold value; converting the processed frequency domain signal into time domain signal, and recovering the signal. And the invention also discloses a device which comprises: a signal sample module, a time/frequency convert module, a narrow-band interference processing module, a frequency/time convert module and a signal reducing module; the narrow-band interference processing module obtains the middle value of frequency domain signal obtained by time/frequency conversation, and damps the signal higher than said middle threshold value, and obtain the signal that damp the narrow-band interference via frequency/time conversation and reduction. The invention can effectively restrain the narrow-band interference of signal.

Disclosed in the invention is a narrow-band interference prevention method. Coarse estimation of interference intensity is carried out on input signals and window functions are determined; according to the window functions, grouped windowing processing is carried out on the input signals, and N-point FFT conversion is carried out on each group of windowing input signals to obtain frequency-domain spectral lines of windowing input signals; a signal outputted after each N-point FFT conversion is used as a signal group, the signal groups are divided into a plurality of sub groups with the same point number, and an initial clamping value is determined based on signal amplitudes of all sub groups; an interference spectral line in the frequency-domain spectral lines is filtered by combining an adaptive variable threshold algorithm and the initial clamping value; IFFT conversion is carried out on signals after interference suppression to output time-domain signals; and the time-domain signals at all paths are combined and then are outputted, thereby completing narrow-band interference prevention of input signals. With the method, the interference spectral line can be filtered effectively and the link reliability can be improved.

The invention discloses a time-varying narrow-band interference suppression method based on complex empirical mode decomposition, which includes the following steps, (1), obtaining SAR return wave; (2), judging that whether time-varying narrow-band interference exists; (3), performing the complex empirical mode decomposition; (4), obtaining the range pulse pressure and performing the range walk correction, (5), performing parameter estimation; (6), performing motion compensation; (7), obtaining the orientation pulse pressure; and (8), performing multi-look processing. The narrow-band interference suppression method provided by the invention is suitable for range and orientation two-dimensional time-varying NBI, makes full use of the complex empirical mode decomposition method, sets the threshold suppression strong interference component, has better strong interference suppression ability, retains signals to the utmost extent, and has clearer SAR imaging.

The invention provides a method for detecting and processing a narrow-band interference of a DS (Direct Sequence)/FH (Frequency Hopping) hybrid spread spectrum communication system. According to the technical scheme, the method comprises the following steps: 1) calculating a frequency domain signal; 2) solving an initial threshold; 3) solving high and low thresholds; and 4) calculating a signal after being subjected to interference rejection. According to the technical scheme provided by the invention, the method belongs to a quick double-threshold algorithm. Besides, according to the method provided by the invention, the calculating speed for solving double thresholds is increased and the amount of the calculation is reduced, so that the consumption of resources is reduced and the practicability of the double-threshold algorithm is boosted.

The application discloses a method for detecting and eliminating narrow-band interference by a GNSS (Global Navigation Satellite System) receiver. The method comprises the steps as follows: firstly, the receiver converts received time-domain signals into frequency-domain signals through FFT (Fast Fourier Transform); secondly, frequency points of narrow-band interference signals are found in the frequency-domain signals and are set as a blocking frequency of a wave trapper; and finally, the receiver filters and eliminates the narrow-band interference signals from the received time-domain signals through the wave trapper. The application has the advantages of simplicity in implementing the technology, smaller calculated amount, high real-time performance and good flexibility.

The invention relates to a frequency-division duplexing transmission method for a wideband wireless communication system, belonging to the technical field of digital information transmission. The method comprises the following steps of: carrying out downlink multiple access at the transmitting end of a base station by adopting a time-domain and frequency-domain united orthogonal frequency division multiple access technology to obtain a downlink signal; carrying out uplink multiple access at the transmitting end of user equipment by adopting a time-domain and frequency-domain united single carrier multiple access technology to obtain an uplink signal; and carrying out duplexing transmission on the downlink signal and the uplink signal by adopting a frequency-division duplexing frame structure. A TFU-OFDMA (Time domain and Frequency domain United Orthogonal Frequency Division Multiple Access) technology provided by the invention can be used for solving the multiple access problem of modulation by adopting TFU-OFDM (Time domain and Frequency domain United Orthogonal Frequency Division Multiplexing) and has the advantages of flexibly allocating wireless resources, effectively resisting deep fading and narrow-band interference and the like; and by using a TFU-SCMA (Time domain and Frequency domain United-Single Carrier Multiple Access) technology provided by the invention, the multiple access problem of modulation by adopting the improved SC-FDE (Single Carrier-Frequency Domain Equalization) can be solved, the advantages that the transmitting end has low complexity and peak-to-average power ratio by the SC-FDE technology can be retained and the synchronization and channel estimation can be better carried out by the receiving end.

A blind self-adaptive filtering method, an apparatus and a broadband transmission system for eliminating narrowband interference are provided. The self-adaptive filtering apparatus includes: a self-adaptive filter, for filtering the current input signal and then outputting it, a first delay unit, for delaying the signal output from the self-adaptive filter with a first time delay length, and an error calculation unit, for implementing correlation operation on the signal output from the self-adaptive filter and the delay signal of the output signal to obtain error information. The self-adaptive filter adjusts the filter parameter according to the feedback error information to eliminate the interference in the latter input signal. As applying the output signal to implement correlation operation with the delay signal of the output signal, thus, the apparatus is used widely, for example, it can be applicable to broadband receiver, it also can be applicable to the case that there are a plurality of strong narrowband interferences, and it also can counteract a plurality of strong narrowband interferences whose swept rate is decades of milliseconds.

The invention discloses a narrow-band interference detecting method and device in an MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system. The method comprises the follow steps of: a pilot-frequency sub-carrier group composed of two pilot frequencies is selected in each time-frequency unit, and the two pilot frequencies in the pilot-frequency sub-carrier group are on different frequency positions of different OFDM signs; and the channel response values of two sub-carriers in the pilot-frequency sub-carrier group minus the signal power sum of the pilot-frequency sub-carrier group obtain the interference noise power value of the pilot-frequency sub-carrier group, so that the interference noise power value of each sub-carrier of the time-frequency unit is determined. The device comprises a pilot-frequency sub-carrier group selecting module and an interference noise power value determining module. The method and the device can accurately estimate the narrow-band interference information and can accurately detect the narrow-band interference position and power even if the narrow-band interference is weaker.

The invention discloses an anti-interference method. The anti-interference method particularly comprises the following steps: conducting frequency domain anti-interference processing to processed signals and then conducting space domain anti-interference processing to the processed signals. The frequency domain anti-interference processing is capable of restraining strong narrow-band interference. After the space domain anti-interference processing is conducted, broadband interference signals entering a receiver can be filtered. According to cascading frequency domain anti-interference and the space domain anti-interference, labor division of the frequency domain anti-interference and the space domain anti-interference are enabled to be clear, frequency domain trapped wave anti-interference is mainly used for restraining of narrow band interference, the number of interference entering the space domain anti-interference is reduced, the space domain anti-interference is enabled to be provided with more freedom degree to restrain the narrow band interference, and a good interference restraining effect is achieved.

The embodiment of the invention relates to the signal processing field, in particular to a method for removing narrow-band interference and a self-adapting filter, aiming to solve the problems of processing time delay and poor real-time for removal of interference by a fixity coefficient filter in the prior art. The method provided by the embodiment of the invention comprises the steps that: the self-adapting filter can determine a weight corresponding to the current sampling time, a cancellation signal corresponding to the current sampling time according to the determined weight and a reference signal sampled at the current sampling time, wherein the reference signal is generated based on a centre frequency of the narrow-band interference; then the self-adapting filter filters a band signal sampled at the current sampling time according to the determined cancellation signal corresponding to the current sampling time, and finally the band signal with narrow-band interference being removed is obtained. The embodiment of the invention can reduce the processing time delay, improve the real time, and perfect an interference cancellation effect.

The invention discloses a laser flasher with big diameter for measuring the structure constant of atmospheric refractivity as well as the method for that. The laser flasher comprises two opposite-arranged reflecting telescopes and lasers on the lens cones. The incident lights reach to the secondary plane mirror after being reflected by a main parabolic mirror in the lens cones, pass the openings, attenuating pieces and narrow-band interference filters on the lens cones, and then are converged on a photoelectric detector. At transmission test, two arrangements are placed at the two ends of the transmission path; the emitting system at one end of the path gives out modulated laser signals, after being transmitted by a turbulent atmosphere, the light signals are collected by the telescope at anther end, and go through photoelectric conversion by the photoelectric multiplier near to the focus; then the electric signals enter into a built-in control system for demodulation, sampling, processing, saving and displaying. The invention is of high accuracy and improves the accuracy in the measurements.

The invention relates to a narrow-band interference suppression method and a narrow-band interference suppression device. The device comprises an adaptive filter module, a fast Fourier transformation module, a narrow-band interference suppression module and a fast inverse Fourier transformation module. The method comprises the following steps of: 1) forecasting a dispersion sequence obtained through sampling to obtain a narrow-band interference forecast signal according to an adaptive algorithm; 2) multiplying the narrow-band interference forecast signal by a factor K to obtain a forecast factor signal, and subtracting the forecast factor signal from a received signal to obtain a first signal; 3) transforming the first signal to a frequency domain, and performing frequency domain wave trapping processing on the first signal in the frequency domain; and 4) converting the first signal subjected to frequency domain wave trapping into a second signal in a time domain, and inputting the second signal into a spread spectrum signal demodulator to finish narrow-band interference suppression. By the method, the shortcoming that a time domain adaptive filter cannot completely suppress the interference is overcome; and energy leakage in a frequency domain wave trapper is reduced.