CN107809256A - A kind of shortwave suppressing method under arrowband interference - Google Patents

Abstract

The invention discloses a method for suppressing shortwave under narrowband interference, which comprises the following steps: adopting the DV algorithm to initially estimate the pilot signal of the shortwave channel, performing noise filtering on the initial estimated value in the time domain for the first time, and receiving For the pulse ultra-wideband signal of the wireless channel, the waveform of the pilot symbol and the waveform of the load symbol are observed separately, and the threshold λ is introduced to filter the initial value for the second time to obtain the estimated value of the pilot signal, which is transformed by DFT discrete Fourier transform. Estimates for the entire channel. The invention performs noise filtering on the initial estimation of the channel twice, which makes up for the problem of incomplete noise filtering of the DFT (Discrete Fourier Transform) channel estimation algorithm. Using compressed sensing and reconstruction algorithms to adaptively detect random narrowband interference and suppress it, the accuracy of receiver correlation template estimation is improved; by accurately estimating and suppressing high-power narrowband interference superimposed in ultra-wideband signals, the detection of receivers is improved reliability.

Description

A Shortwave Suppression Method Under Narrowband Interference

technical field

The invention relates to the technical field of communication, in particular to a short-wave suppression method under narrow-band interference.

Background technique

The CDMA signal is a pseudo-random signal, and the power spectrum spreads to the entire baseband bandwidth. Removing narrowband interference (NarrowBand Interference) will only slightly damage the CDMA signal. Therefore, CDMA signals have a certain anti-narrowband interference performance. For example, the Global Navigation Satellite System (GNSS) signal itself can resist interference with a 30dB interference-to-signal ratio. Signals are handled correctly.

Narrowband strong interference is a common interference in practical applications, and its suppression can be done in time domain or frequency domain. The time-domain method uses the correlation of narrow-band interference to perform least mean square (Least Mean Squares, LMS) algorithm or recursive least squares (Recursive Least Squares, RLS) algorithm adaptive filtering. Time domain filtering has high hardware implementation complexity and slow convergence time. And the disadvantages such as group delay change; the frequency domain method uses Fast Fourier Transformation (FastFourierTransformation, FFT) or Fast Fourier Transformation (InverseFourierTransformation, IFFT) to zero the frequency point where the interference is located to eliminate interference. Among them, the frequency domain algorithm has been widely used because it can use FFT/IFFT fast algorithm to reduce the amount of calculation, and can guarantee the linear phase of the interference suppression system. At present, there are two common ways of frequency domain filtering:

The first method is a simple FFT/IFFT-based interference suppression technology, which outputs the data after windowing processing, FFT calculation, NBI filtering processing, and IFFT calculation. Although this method can remove narrowband interference, windowing processing reduces FFT When the frequency spectrum leakage prevents the interference from spreading to other frequency points, it also has the disadvantage of causing distortion of the input signal and resulting in a loss of the signal-to-noise ratio of the output signal.

In the second way, in order to reduce the SNR loss caused by windowing, an interference suppression technology based on Overlapped Fast Fourier Transform (OFFT, Overlapped Fast Fourier Transform,) is proposed. The basic idea is to copy the input data and shift windowing, get two windowed data together with the original windowed data, perform FFT transformation, and filter in the frequency domain, after filtering, perform IFFT to obtain the time domain data that removes interference, and finally Align and merge the two paths of data to get the final output. The shortcomings of this method mainly include the following points: First, interference does not always exist, but the interference canceller is always working, which increases unnecessary system power consumption; second, the length of FFT/IFFT is fixed, and the detection sensitivity for narrowband interference is limited. The third is that the window function is fixed, which is not conducive to the filtering of large dynamic range interference; the fourth is that the method of delaying data in the existing OFFT interference suppression method is generally to add a module for delaying data before adding a window, which is used for all the way The input data is buffered so that it can be output together with another channel of original data for windowing processing, and after frequency domain filtering, it is also necessary to add a delay data module to delay the data that is not delayed so that it can be compared with The data that has been delayed before can be aligned for subsequent merged output. This method has the problems of high resource overhead and high design complexity.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a short-wave suppression method under narrow-band interference. The interference detection is performed on the input signal through the interference detector to obtain the interference detection information, and it is output to the narrow-band interference canceller. , the narrowband interference canceller performs narrowband interference suppression on another input signal according to the interference detection information, so as to solve the problems of high system power consumption, limited detection sensitivity, fixed window function and high design complexity existing in the prior art .

The present invention solves the above technical problems through the following technical solutions:

A short-wave suppression method under narrow-band interference, comprising the steps of:

S1. Under narrow-band interference, after receiving the signal, the receiving end uses the DV algorithm to initially estimate the pilot signal of the short-wave channel to obtain the initial estimated value in the frequency domain, and then IDFT the initial estimated value in the frequency domain. The inverse transformation is transformed to obtain the initial estimated value in the time domain;

S 2. According to the principle of the DFT discrete Fourier transform channel estimation algorithm, that is, the length of the channel impulse response is less than the length of the cyclic prefix code Ng, that is, the estimated value greater than the length of the cyclic prefix code Ng is noise, and the initial estimated value in the time domain Perform the first noise filtering;

S 3. Receive the pulsed ultra-wideband signal from the wireless channel, and send the signal to the receiving filter module to filter out-of-band noise and interference for the pulsed ultra-wideband signal;

S 4. Observe the pilot symbol waveform and the load symbol waveform respectively, and send the pilot observation sequence to the pilot observation storage module, and send the load observation sequence to the load observation storage module, and temporarily store the observations of each pilot symbol waveform sequence, and send it to the narrowband interference estimation module and the subtractor module; use the OMP algorithm to estimate the narrowband interference, and send the narrowband interference contained in the estimated pilot symbol waveform to the pilot narrowband interference observation module, and the estimated load signal waveform The narrowband interference contained in is sent to the load narrowband interference suppression module;

S 5. Introduce the threshold λ to perform second noise filtering on the initial value and obtain the estimated value of the pilot signal: perform noise filtering on hDFT(n) with 0≤n≤Ng-1, that is, when the amplitude of the hDFT(n) signal is less than When λ, the signal is considered to be noise and set to 0. When the amplitude of the hDFT(n) signal is greater than λ, the signal is regarded as a useful signal and remains unchanged, and then the channel estimated by the noise and the pilot The probability density function of the magnitude of the impulse response is used to obtain the optimal threshold λbest, and the final estimated value of the pilot is obtained according to the optimal threshold λbest;

S 6. Perform interpolation on the pilot estimate according to the interpolation method and pilot structure, and then perform DFT discrete Fourier transform on it to obtain an estimate of the entire channel.

Further, step S7 is also included:

Observing the pilot symbol narrowband interference estimated by the narrowband interference estimation module respectively, and sending the observed narrowband interference observation sequence to the narrowband interference observation storage module; temporarily storing the narrowband interference observation sequence, and sending it to the subtractor module; The subtractor subtracts its corresponding narrowband interference observation sequence from each pilot observation sequence to obtain a pilot observation sequence that suppresses narrowband interference; sums and averages the pilot observation sequences that suppress narrowband interference obtained in the subtractor module The operation obtains the average pilot observation sequence to reduce the influence of additive Gaussian white noise, and sends it to the signal correlation template generation module; the signal correlation template generation module: according to the average pilot observation sequence obtained by the vector average module, the OMP algorithm is used Reconstruct the signal correlation template and send it to the correlation demodulation module.

Optionally, in step S1, the shortwave channel adopts the ITS shortwave channel transmission model.

Further, the step S7 includes the following steps:

Step S71: Properly delay the load signal and send it to the load narrowband interference suppression module;

Step S72: Temporarily store the load observation sequence obtained by the observation module, and send the observation sequence of each load signal to the narrowband interference estimation module in turn;

Step S73: Using a subtractor to subtract the narrowband interference contained in the load signal estimated by the narrowband interference estimation module from each load signal waveform, and send the load signal after the narrowband interference is suppressed to the relevant demodulation module;

Step S74: Using the signal template generated by the signal correlation template generation module as a correlation template, correlator and decision unit are used to correlate and demodulate the load signal output by the load narrowband interference suppression module after narrowband interference suppression.

The short-wave suppression method under narrow-band interference of the present invention performs noise filtering on the initial estimation of the channel twice, which makes up for the incomplete noise filtering problem of the DFT (Discrete Fourier Transform) channel estimation algorithm. And without increasing the complexity of channel estimation and without the need for statistical information of the channel, the narrowband interference caused by traditional narrowband shortwave signals less than 3kHz is effectively filtered out by introducing a threshold, and the performance of channel estimation is improved. At the same time, the pilot frequency of the present invention adopts a comb structure, which effectively suppresses the fast fading of short-wave signals. The sampling rate is greatly reduced through compressed sensing, which breaks through the technical bottleneck faced by the traditional sampling theory, which is beneficial to control the cost and power consumption of the receiver; the compressed sensing and reconstruction algorithm is used to adaptively detect and suppress random narrow-band interference, which improves the reception Machine-related template estimation accuracy; by accurately estimating and suppressing the high-power narrow-band interference superimposed on the ultra-wideband signal, the detection reliability of the receiver is improved.

The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable , below in conjunction with the preferred embodiment, and with the accompanying drawings, the detailed description is as follows.

Description of drawings

Fig. 1 is a schematic flow chart of the short-wave suppression method under narrow-band interference of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings. As a part of this description, the principle of the present invention will be described through embodiments. Other aspects, features and advantages of the present invention will become clear at a glance through the detailed description. In the figures referred to, the same or similar components in different figures are denoted by the same reference numerals.

As shown in Figure 1, a shortwave suppression method under narrowband interference provided by an embodiment of the present invention includes the following steps:

Under narrow-band interference, after receiving the signal, the receiving end uses the DV algorithm to initially estimate the pilot signal of the short-wave channel to obtain the initial estimated value in the frequency domain, and then IDFT the inverse discrete Fourier transform of the initial estimated value in the frequency domain Transform to get the initial estimate in the time domain.

According to the principle of the DFT discrete Fourier transform channel estimation algorithm, that is, the length of the channel impulse response is smaller than the cyclic prefix code Ng, that is, the estimated value greater than the length Ng of the cyclic prefix code is noise, and the initial estimated value in the time domain is firstly evaluated. noise filtering.

The pulse ultra-wideband signal from the wireless channel is received, and the signal is sent to the receiving filter module, and the out-of-band noise and interference are filtered out for the pulse ultra-wideband signal.

Observing the pilot symbol waveform and the load symbol waveform respectively, sending the pilot observation sequence to the pilot observation storage module, sending the load observation sequence to the load observation storage module, temporarily storing the observation sequence of each pilot symbol waveform, and Send it to the narrowband interference estimation module and the subtractor module; Utilize the OMP algorithm to estimate the narrowband interference, send the narrowband interference contained in the estimated pilot symbol waveform to the pilot narrowband interference observation module, and use the estimated load signal waveform to contain the narrowband interference The narrowband interference is sent to the load narrowband interference suppression module.

Introduce the threshold λ to filter the initial value for the second time and obtain the estimated value of the pilot signal: filter the hDFT(n) with 0≤n≤Ng-1, that is, when the amplitude of the hDFT(n) signal is less than λ, Consider this signal as noise and set it to 0. When the amplitude of the hDFT(n) signal is greater than λ, treat this signal as a useful signal and keep it unchanged, and then use the channel impulse response estimated by the noise and the pilot The probability density function of the amplitude obtains the optimal threshold λbest, and the final estimated value of the pilot is obtained according to the optimal threshold λbest.

Interpolate the pilot frequency estimation according to the interpolation method and the pilot frequency structure, and then perform DFT discrete Fourier transform on it to obtain the estimation of the whole channel.

Observing the pilot symbol narrowband interference estimated by the narrowband interference estimation module respectively, and sending the observed narrowband interference observation sequence to the narrowband interference observation storage module; temporarily storing the narrowband interference observation sequence, and sending it to the subtractor module; The subtractor subtracts its corresponding narrowband interference observation sequence from each pilot observation sequence to obtain a pilot observation sequence that suppresses narrowband interference; sums and averages the pilot observation sequences that suppress narrowband interference obtained in the subtractor module The operation obtains the average pilot observation sequence to reduce the influence of additive Gaussian white noise, and sends it to the signal correlation template generation module; the signal correlation template generation module: according to the average pilot observation sequence obtained by the vector average module, the OMP algorithm is used Reconstruct the signal correlation template and send it to the correlation demodulation module.

In step S1, the shortwave channel adopts the ITS shortwave channel transmission model.

Described step S7 comprises the following steps:

Properly delay the load signal and send it to the load narrowband interference suppression module;

Temporarily store the load observation sequence obtained by the observation module, and send the observation sequence of each load signal to the narrowband interference estimation module in turn;

Using a subtractor to subtract the narrowband interference contained in the load signal estimated by the narrowband interference estimation module from each load signal waveform, and send the load signal after the narrowband interference is suppressed to the relevant demodulation module;

The signal template generated by the signal correlation template generation module is used as a correlation template, and the correlator and the decision device are used to correlate and demodulate the load signal output by the load narrowband interference suppression module after the narrowband interference is suppressed.

The short-wave suppression method under narrow-band interference of the present invention performs noise filtering on the initial estimation of the channel twice, which makes up for the incomplete noise filtering problem of the DFT (Discrete Fourier Transform) channel estimation algorithm. And without increasing the complexity of channel estimation and without the need for statistical information of the channel, the narrowband interference caused by traditional narrowband shortwave signals less than 3kHz is effectively filtered out by introducing a threshold, and the performance of channel estimation is improved. At the same time, the pilot frequency of the present invention adopts a comb structure, which effectively suppresses the fast fading of short-wave signals. The sampling rate is greatly reduced through compressed sensing, which breaks through the technical bottleneck faced by the traditional sampling theory, which is beneficial to control the cost and power consumption of the receiver; the compressed sensing and reconstruction algorithm is used to adaptively detect and suppress random narrow-band interference, which improves the reception Machine-related template estimation accuracy; by accurately estimating and suppressing the high-power narrow-band interference superimposed on the ultra-wideband signal, the detection reliability of the receiver is improved.

The above description is a preferred embodiment of the present invention, and it should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also considered Be the protection scope of the present invention.

Claims (4)

1. a kind of shortwave suppressing method under arrowband interference, it is characterised in that comprise the following steps：

S1, under being disturbed in arrowband, after receiving terminal receives signal, the pilot signal of short wave channel is initially estimated using DV algorithms Meter obtains the initial estimate under frequency domain, then converts to obtain by the initial estimate IDFT inverse discrete fourier transforms under frequency domain Initial estimate under time domain；

S2, cyclic prefix is less than according to DFT discrete Fourier transform channel estimation method principles, the i.e. length of channel impulse response Code Ng, i.e. the estimate more than the length Ng of cyclic prefix code is all noise, and the initial estimate under time domain is carried out for the first time Filter is made an uproar；

S3, the impulse ultra-wideband signal from wireless channel is received, and the signal is sent into receiving filter module, pulse is surpassed Broadband signal filters out out-of-band noise and interference；

S4, frequency pilot sign waveform and load signs waveform are observed respectively, and pilot observations sequence is sent to pilot observations Memory module, load observation sequence is sent to load observation memory module, keeps in the observation sequence of each frequency pilot sign waveform, and will It is sent to arrowband interference estimation block and subtracter block；Using OMP algorithms estimation arrowband interference, by the frequency pilot sign ripple of estimation Pilot narrow-band disturbance-observer module is sent in the arrowband interference contained in shape, and the arrowband contained in the load signal waveform of estimation is done Disturb and be sent to load Suppression of narrow band interference module；

S5, introducing threshold value λ carry out filtering for the second time to initial value makes an uproar and obtains pilot signal estimate：To 0≤n≤Ng-1 hDFT (n) carry out filter to make an uproar, i.e., when the amplitude of hDFT (n) signals is less than λ, being considered as this signal is noise and is set to 0, works as hDFT (n) when the amplitude of signal is more than λ, this signal as useful signal and is just kept constant, then estimated by noise and pilot tone The probability density function of amplitude of channel impulse response obtain optimal threshold λ best, and drawn and led according to optimal threshold λ best The final estimate of frequency；

S6, according to interpolation method and pilot configuration pilot tone is estimated, into row interpolation, then to carry out DFT discrete Fourier transforms to it Become the estimation for getting whole channel in return.

2. the shortwave suppressing method according to claim 1 under arrowband interference, it is characterised in that：Also include step S7：

The frequency pilot sign arrowband interference that arrowband interference estimation block is estimated is observed respectively, and the arrowband that observation is obtained is done Disturb observation sequence and be sent to arrowband disturbance-observer memory module；Temporary arrowband disturbance-observer sequence, and it is sent to subtracter block； Using subtracter, its corresponding arrowband disturbance-observer sequence is subtracted from each pilot observations sequence, obtains and suppresses arrowband interference Pilot observations sequence；The pilot observations sequence disturbed the suppression arrowband obtained in subtracter block carries out summation and takes average behaviour Make to obtain average pilot observation sequence, to reduce the influence of additive white Gaussian noise, and be sent to the generation of signal correlate template Module；Signal correlate template generation module：The average pilot observation sequence obtained according to vectorial averaging module, utilizes OMP algorithms Reconstruction signal correlate template, and it is sent to correlation demodulation module.

3. the shortwave suppressing method according to claim 1 under arrowband interference, it is characterised in that：In step sl, it is short Ripple channel uses ITS short wave channel modes.

4. the shortwave suppressing method according to claim 2 under arrowband interference, it is characterised in that the step S7 includes Following steps：

Step S71：Load signal is suitably postponed, and is sent to load Suppression of narrow band interference module；

Step S72：The temporary load observation sequence obtained by observation module, and the observation sequence of each load signal is given successively Toward arrowband interference estimation block；

Step S73：The load estimated by arrowband interference estimation block is subtracted from each load signal waveform using subtracter to believe The arrowband interference included in number, and it is sent to correlation demodulation module by the load signal after arrowband disturbs is suppressed；

Step S74：, as correlate template, correlator and decision device are utilized using signal templates caused by signal correlate template generation module Correlation demodulation is carried out to the load signal after arrowband disturbs that suppresses of load Suppression of narrow band interference module output.