CN103248595B - A kind of self adaptation is with location interference cancellation method and device - Google Patents

Abstract

The invention discloses an adaptive co-site interference cancellation method and device, which adopts multiple reference input signals, and divides the filtering process into two stages to process the signals, so as to suppress multiple co-site interference signals. The present invention can effectively suppress co-site interference generated by multiple devices, and only needs to collect data at the receiving antenna without coupling and collecting devices for interference signals, thereby simplifying the self-adaptive interference cancellation module and being more suitable for real-time narrow working environments.

Description

A method and device for adaptive co-site interference cancellation

technical field

The present invention relates to the field of wireless communication, in particular to an adaptive co-site interference cancellation method and device.

Background technique

In vehicle-mounted, ship-borne and airborne wireless communications, it is often necessary to arrange multiple radio stations on one communication platform. A single transmitter usually couples into signals from a large number of nearby transmitters, which is known as co-site interference. When the transmission signal power of a nearby transmitter is very high, the strong interference level generated generally exceeds the dynamic range of the neighboring receiver, causing the receiver to be blocked and causing communication interruption. Therefore, how to effectively suppress co-site interference has attracted great attention.

At present, the method of solving co-site interference is mainly carried out from two aspects of hardware and software. On the hardware, the design and process method of the entire communication system and circuit technology are optimized to improve the performance of electronic equipment, reduce the level of interference sources, and increase The attenuation of the interference source on the propagation path and the improvement of the anti-interference ability of the equipment, etc. The main purpose of the software is to reasonably allocate the spatial location and frequency spectrum of each communication device to reduce co-site interference. These methods have certain limitations. When the interference level is too large, the suppression effect will be seriously deteriorated.

In order to further cancel the interference signal, the adaptive interference cancellation technology has become the research direction of people. An adaptive signal processing module is introduced between the antenna and the receiver to perform adaptive interference cancellation processing on the received signal. Eliminate high-power interference signals to a large extent without affecting the normal operation of the receiver behind. Most of the commonly used adaptive interference cancellation algorithms are based on the adaptive LMS algorithm. Aiming at the strong power and time-varying characteristics of co-site interference signals, many improved variable-step-size LMS algorithms have been born, with small calculations, fast convergence speed, and change The self-adaptive algorithm of the filter structure, as well as improving the correlation of the signal to increase the cancellation degree of the interference signal, these methods have a good effect on dealing with the co-site interference signal, but when the number of co-site interference sources increases, it is necessary to Coupling and collecting interference signals at each interference transmitting antenna complicates the interference signal acquisition equipment of the adaptive interference cancellation module and increases the burden on the limited working space.

Contents of the invention

The technical problem to be solved by the present invention is to provide an adaptive co-site interference cancellation method and device, which can effectively suppress the co-site interference generated by multiple devices, and only need to collect data at the receiving antenna without coupling and collecting interference signals The device simplifies the adaptive interference cancellation module and is more suitable for real-time narrow working environments.

In order to solve the above problems, the present invention is achieved through the following schemes:

A method for adaptive co-site interference cancellation, comprising the steps of:

In the first step, the signal received by the antenna at the receiving end is oversampled and extracted into N signals, where the oversampling rate is f _s , and the equivalent sampling rate of each channel after extraction is f _es , f _s =Nf _es , and The sampling theorem requires that f _es >=2f _max should be satisfied between f _es and the received signal, and f _max is the highest frequency of the received signal;

In the second step, in the pure interference stage, that is, before the transceiver station receives the call sign, the communication link is not established; at this time, the signal received by the receiving antenna only contains the co-site interference signal and noise, so that the oversampled and extracted N The signals of the channels are x ₁ , x ₂ ,...,x _N , select any one of the N channels of signals as the main channel signal x ₁ , and the other N-1 channels of signals are used as the reference channel signals x ₂ , x ₃ ,..., _xN ;

The third step is to input x ₂ , x ₃ ,..., x _N total of N-1 reference channel signals into the first-stage filter, and adjust the first-stage filter coefficients to make the first-stage filter output The power of the error signal obtained by subtracting the signal from the main channel signal x ₁ is the smallest;

The fourth step, in the stage containing the useful signal, that is, the stage after the call sign and handshake between the transmitting and receiving stations, and the communication link between the two parties is established; at this time, the signal received by the receiving antenna is the useful signal s, co-site interference signal and noise, so that at this time The oversampled and extracted N-channel signals are x ₁ +s ₁ ,x ₂ +s ₂ ,...,x _N +s _n , and any one of these N-channel signals is selected as the main channel signal, that is, x ₁ +s ₁ , the other N-1 signals are used as reference channel signals, namely x ₂ +s ₂ , x ₃ +s ₃ ,...,x _N +s _n ;

In the fifth step, input x ₂ +s ₂ , x ₃ +s ₃ ,...,x _N +s _n total N-1 reference channel signals into the first-stage filter, and keep the first-stage filter The coefficient remains unchanged, and the error signal after subtracting the output signal of the first-stage filter from the main channel signal x ₁ +s ₁ is used as the input of the second-stage filter;

The sixth step is to adjust the coefficients of the second-stage filter so that the power of the error signal obtained by subtracting the output signal of the second-stage filter from the main channel signal x ₁ +s ₁ is the smallest, and the output signal of the second-stage filter is useful signal for recovery.

In the above method, the received signal is sampled and extracted into N-channel signals. The larger the value of N, the better the performance of the algorithm, but the higher the required sampling rate, the more difficult the hardware implementation is. Comprehensive consideration is desirable. The value of N is between 2 and 8.

Both the first-stage filter and the second-stage filter are adaptive filters.

An adaptive co-site interference cancellation device capable of implementing the above method, mainly composed of a decimator, a first-stage filter and a second-stage filter; wherein the input end of the decimator is coupled to the receiving antenna; the N decimator One of the main channel output terminals in the output terminal is connected to the control terminal of the first-stage filter and the second-stage filter, and the N-1 reference channel output terminals are connected to the input terminal of the first-stage filter; the first-stage filter The output end of the filter is connected to the input end of the second-stage filter, and the output end of the second-stage filter is coupled to the input end of the receiver.

The number N of output terminals of the decimator is between 2 and 8.

Both the first-stage filter and the second-stage filter are adaptive filters.

Compared with the traditional co-site interference cancellation algorithm, the present invention has the following advantages:

(1) No signal coupling acquisition device is required. The traditional adaptive co-site interference cancellation method needs to couple and extract the interference signal from the interference antenna as a related signal for adaptive interference cancellation. This method obtains the related signal by extracting the received signal into N signals.

(2) It can effectively suppress the interference of multiple devices. When the number of interference signals is too large, the traditional adaptive interference cancellation method needs to lead out the interference and cancel the interference signals one by one through the adaptive interference cancellation method, while the interference cancellation process of this method is not affected by the number of interferences.

(3) More suitable for narrow working environment. The method only needs to couple the signal from the receiving end to perform adaptive interference cancellation processing, and uses the frequency difference between the useful signal and other interference signals to cancel the interference signal and restore the useful signal.

Description of drawings

Fig. 1 is a schematic block diagram of the application of the co-site interference cancellation device.

Figure 2 is a schematic diagram of the two-stage filter noise cancellation algorithm.

Figure 3(a) Curve of bit error rate changing with N.

Fig. 3 (b) BER change curve with f _es .

Figure 4 is a comparison of the power spectrum diagrams of the multi-reference input co-site interference cancellation algorithm and the traditional co-site interference cancellation algorithm in the case of multiple interference sources.

Figure 5 is a comparison of the bit error rate between the multi-reference input co-site interference cancellation algorithm and the traditional co-site interference cancellation algorithm under the Ricean multipath channel under the condition of multiple interference sources.

detailed description

The application principle of a new multi-reference input co-site interference cancellation device proposed by the present invention is shown in Figure 1. The self-adaptive co-site interference cancellation device shown in the figure is mainly composed of a decimator and a first-stage filter and the second stage filter. Wherein the input end of the decimator is coupled with the receiving antenna. One of the main channel output terminals of the N output terminals of the decimator is connected to the control terminals of the first-stage filter and the second-stage filter, and the N-1 reference channel output terminals are connected to the input terminals of the first-stage filter . The output end of the first stage filter is connected to the input end of the second stage filter, and the output end of the second stage filter is coupled to the input end of the receiver. In the present invention, the larger the number N of output ends of the decimator is, the better the performance of the algorithm is, but the higher the required sampling rate is, the more difficult the hardware implementation is. After comprehensive consideration, in a preferred embodiment of the present invention, the number N of output terminals of the decimator is between 2 and 8. The first-stage filter and the second-stage filter are both adaptive filters.

Transmitter 1 to transmitter n are n communication devices in the same workspace as receiver s, and receiver s receives signals sent by transmitters in another workspace. Due to the distance between receiver s and n transmitters in the same workspace Very close, the signal sent by the transmitter 1 to the transmitter n is easily received by the front end of the receiver s, causing interference to the useful signal received by the receiver s, so the signal received by the front end of the receiver is a mixture of multiple interference signals and useful signals signal, the mixed signal Y is Y=I ₁ +I ₂ +...+I _{n +} R _s , where I ₁ , I ₂ ,...,In are interference signals, and R _s is a useful receiving signal.

The received mixed signal is oversampled and extracted into multiple signals to obtain multiple reference input signals, and according to the principle diagram of the two-stage filter noise cancellation algorithm shown in Figure 2, the filtering process is divided into two stages to adapt the signal Filter processing, based on the frequency difference between the useful signal and other interference signals, the weight coefficient of the filter tracking the useful signal is different from the weight coefficient of tracking the interference signal, so as to offset the interference and restore the useful signal.

An adaptive co-site interference cancellation method implemented by the above device includes the following steps:

In the first step, the signal received by the antenna at the receiving end is oversampled and extracted into N signals, where the oversampling rate is f _s , and the equivalent sampling rate of each channel after extraction is f _es , f _s =Nf _es , and The sampling theorem requires that f _es >=2f _max should be satisfied between f _es and the received signal, and f _max is the highest frequency of the received signal;

In the second step, in the pure interference stage, that is, before the station receives the call sign, the communication link is not established; at this time, the signal received by the receiving antenna only contains co-site interference signals and noise, so that the over-sampled and extracted N-channel The signal is x ₁ , x ₂ ,...,x _N , select any one of the N signals as the main channel signal x ₁ , and the other N-1 signals as the reference channel signal x ₂ , x ₃ , ..., _xN ;

The third step is to input x ₂ , x ₃ ,..., x _N total of N-1 reference channel signals into the first-stage filter, and adjust the first-stage filter coefficients to make the first-stage filter output The power of the error signal obtained by subtracting the signal from the main channel signal x ₁ is the smallest;

The fourth step, in the stage containing the useful signal, that is, the stage after the call sign and handshake between the transmitting and receiving stations, and the communication link between the two parties is established; at this time, the signal received by the receiving antenna is the useful signal s, co-site interference signal and noise, so that at this time The oversampled and extracted N-channel signals are x ₁ +s ₁ ,x ₂ +s ₂ ,...,x _N +s _n , and any one of these N-channel signals is selected as the main channel signal, that is, x ₁ +s ₁ , the other N-1 signals are used as reference channel signals, namely x ₂ +s ₂ , x ₃ +s ₃ ,...,x _N +s _n ;

In the fifth step, input x ₂ +s ₂ , x ₃ +s ₃ ,...,x _N +s _n total N-1 reference channel signals into the first-stage filter, and keep the first-stage filter The coefficient remains unchanged, and the error signal after subtracting the output signal of the first-stage filter from the main channel signal x ₁ +s ₁ is used as the input of the second-stage filter;

The sixth step is to adjust the coefficients of the second-stage filter so that the power of the error signal obtained by subtracting the output signal of the second-stage filter from the main channel signal x ₁ +s ₁ is the smallest, and the output signal of the second-stage filter is useful signal for recovery.

Whether it is in the pure interference stage or in the stage containing the useful signal, the received signal is extracted into 2~8 signals after being sampled. Both the first-stage filter and the second-stage filter are adaptive filters. The noise cancellation algorithm of the two-stage filter uses a two-stage adaptive filtering system for filtering. The whole filtering process includes two stages: (1) The pure interference signal stage (the mixed signal collected by the receiver does not contain useful signals, only contains multiple interference signal). (2) Contains the useful signal stage (the mixed signal collected by the receiver contains useful signals and multiple interference signals at the same time).

The received mixed signal Y is extracted into N channels of signals through the decimator. First, in the stage of pure interference signals, D ₁ channel of pure interference signals x ₁ is set as the main channel signal, and D ₂ D ₃ ... D _N channels of pure interference signals x ₂ x ₃ ... x _N is set as the reference channel signal, and the purpose of this stage is to offset the main channel signal x ₁ with the reference channel signal. See Figure 2.

The following is an example of a two-channel adaptive noise cancellation system (that is, the system has only one reference channel signal except the main channel signal). At this time, the mixed signal collected by the receiver is extracted by parity, and the single-channel signal becomes The two-way signal x ₁ x ₂ , x ₂ is used as the reference channel signal to input the first-stage filter to offset x ₁ , and adjust the first-stage filter coefficient to make the mean square of the difference between the first-stage filter output and the main channel signal value reaches a minimum, with

$\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; T</span>}}$

w ₂ =[w ₂₁ ,w ₂₂ ,...w _2L ]

Among them, L is the filter order, w ₂ is the filter coefficient, e is the prediction error of the signal x ₂ offsetting x ₁ , the size of the prediction error is directly related to the degree of interference cancellation, if the correlation between x ₂ and x ₁ is higher The larger the value, the better the interference cancellation effect, so the multi-channel reference channel signal x ₂ x ₃ ... x _N can be used to cancel x ₁ , there is

$\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; w</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; [</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; T</span>}}$ ${\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

w=[w ₂ ,w ₃ ,...,w _N ]

w _i =[w _i1 ,w _i2 ,...w _iL ]

Then, in the stage of containing the signal, the N-way mixed signal is obtained in the same way through the extractor. Since the signal transmission environment is basically unchanged in a short period of time, and in the actual working environment, the stations in the same space usually have to follow the frequency allocation plan Assign different working frequencies, that is, the frequency of the co-site interference signal is different from the frequency of the useful signal. Therefore, based on the frequency difference between the useful signal and other interference signals, the weight coefficient of the filter tracking the useful signal and the weight coefficient of tracking the interference signal are Differently, the first-stage filter can be used as a fixed filter to keep the coefficients of the first-stage filter unchanged to achieve the purpose of canceling the interference signal. At this time, the main channel signal is x ₁ +s ₁ , and the reference channel signal is x ₂ +s ₂ ,x ₃ +s ₃ ,...,x _N +s _N , so we have

${\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$ $\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; [</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}_{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; T</span>}}$

${\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

${\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{<span\; class="notranslate">\; *</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{<span\; class="notranslate">\; *</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$ $<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; w</span>}}^{<span\; class="notranslate">\; *</span>}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; e</span>}$

Among them, w ^* is the optimal filter coefficient, and e is the optimal prediction error obtained in the pure interference signal stage. At this time, e ₁ is the distorted signal of s ₁ , which is related to s _1. Take e ₁ as the input of the second-stage filter, and adjust the coefficient of the second-stage filter so that the output of the second-stage filter is consistent with the main channel signal The mean square value of the difference Reaching the minimum, the output signal of the second-stage filter is the useful signal after denoising. because,

e ₂ (n)=x ₁ (n)+s ₁ (n)-y ₂ (n)

${\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; ww</span>}$

$\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; T</span>}}$

ww=[ww ₁ ,ww ₂ ,...ww _L1 ]

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; \{</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \}</span>$

$<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; \{</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \}</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; \{</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \}</span>$

$<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \}</span>$

Among them, ww is the coefficient of filter B, and L1 is the order _of filter B. It can be seen from the formula that in order to achieve the minimum mean square error, it may be assumed that the interference signal is not correlated with the useful signal, so E{2x ₁ (n)[s ₁ (n)-y ₁ (n)]}=0, That is to minimize E[(s ₁ -y ₂ ) ² ], that is, y ₂ ≈s ₁ , that is, the output of the second-stage filter is the recovered useful signal.

The present invention is based on the co-site interference cancellation system model of direct spread spectrum, sets three interference signals and useful signals as direct spread signals, information code rate is 58kbps, spread spectrum code is a gold code with a length of 15, and adopts BPSK modulation. The useful signal frequency is 5MHz, and the three interference signal frequencies are 8MHz, 10MHz, and 12MHz. The co-site interference channel is a three-path Rice multipath channel, the signal-to-noise ratio is 25dB, 26dB, 28dB, the amplitude of the interference signal is 8, 9, and 10 times the amplitude of the useful signal, and the order of the first-stage filter is 6. The order of the second-stage filter is 2, the filter order of the traditional multi-reference input co-site interference cancellation method is 4, and f _es takes the multiple of the bandwidth of receiving useful signals as the unit.

The two curves of bit error rate simulation in Figure 3(a) are the bit error rate curves when f _es =40 and f _es =30 from top to bottom. When the number of channels extracted is the same, the smaller f _es is, That is, the fewer sampling points of each branch signal, the higher the bit error rate; when f _es is constant, that is, the sampling points of each branch signal are constant, the more channels are extracted, the lower the bit error rate. The two curves of bit error rate simulation in Figure 3(b) are the bit error rate curves when N=3 and N=4 from top to bottom. The simulation found that when the received signal is extracted into three channels, f _es >140 When the bit error rate is less than 10 ^-3 , it can meet the communication requirements; when the received signal is extracted into four channels, and f _es >120, the bit error rate is less than 10 ^-3 , which can meet the communication requirements.

In Figure 4, the first power spectral density shows the power distribution of the received mixed signal. It can be seen that the main channel signal is a mixed signal containing four frequency components, which are 5MHz useful signal and 8MHz, 10MHz, 12MHz interference signal, and the power of the interference signal is 100 times stronger than that of the useful signal. The second power spectral density shows the power distribution of the useful signal with a frequency of 5MHz. (N=2) and the multi-reference input co-site interference cancellation algorithm (N=3) suppress the power distribution of the useful signal recovered from the interference. It can be seen that in the power spectrum diagram of the co-site interference cancellation algorithm with multi-reference input, its energy distribution The situation is basically consistent with the useful signal, and the interference signals with frequencies of 8MHz, 10MHz, and 12MHz are also basically filtered out. However, it can be found in the power spectrum of the single-reference input co-site interference cancellation algorithm that there are still a small number of frequency components of interference signals that have not been detected. offset completely.

The two curves in Figure 5, from top to bottom, are the BER simulations of the single reference input co-site interference cancellation algorithm (N=2) and the multi-reference input co-site interference cancellation algorithm (N=3). The simulation results show that the multi-reference input co-site interference cancellation algorithm has significantly better bit error rate performance than the single-reference input co-site interference cancellation algorithm, and the multi-reference input co-site interference cancellation can achieve a signal-to-interference ratio of -20dB The bit error rate can still reach 10 ^-3 , which meets the communication requirements.

Aiming at the actual co-site interference cancellation system, the present invention uses only one received signal to extract multi-channel signals to obtain related signals for adaptive interference cancellation through a two-stage filtering process. When there are too many co-site interference signals, it can still have Excellent interference cancellation effect and simplified signal processing module, the essence is to increase the sampling rate in exchange for structural simplification. Compared with the traditional adaptive co-site interference cancellation algorithm, it is more suitable for multiple devices working together in a narrow space. In addition, when the co-site interference environment changes, the performance of the co-site interference cancellation algorithm will deteriorate, resulting in the interruption of the communication link. At this time, both the sending and receiving parties need to re-establish the link through the call sign handshake, and the multi-reference input adaptive co-site interference cancellation algorithm will repeat the above two stages, which is different from the fact that the adaptive algorithm needs a certain period of time to re-converge after the environmental conditions change. above is the same.

Claims (6)

1. A method for adaptive co-site interference cancellation, characterized in that it comprises the steps: In the first step, the signal received by the antenna at the receiving end is oversampled and then extracted into N channels of signals, wherein the oversampling rate is f _s , and the equivalent sampling rate of each channel after extraction is f _es , with f _s =Nf _es , and The sampling theorem requirement f _es >=2f _max should be satisfied between f _es and the received signal, where f _max is the highest frequency of the received signal; The second step is in the pure interference stage, that is, the stage before the transceiver station receives the call sign and the communication link is not established; at this time, the signal received by the receiving antenna only contains co-site interference signals and noise, so that the oversampled and extracted N The signals of the channels are x ₁ , x ₂ ,…,x _N , any one of the N channels of signals is selected as the main channel signal x ₁ , and the other N-1 channels of signals are used as the reference channel signals x ₂ , x ₃ ,… , x _N ; The third step is to input x ₂ , x ₃ ,…, x _N total of N-1 reference channel signals into the first-stage filter, and adjust the first-stage filter coefficients so that the output signal of the first-stage filter is the same as The power of the error signal obtained by subtracting the main channel signal x ₁ is the smallest; The fourth step, in the stage containing useful signals, that is, the stage after the call sign and handshake between the transmitting and receiving stations, and the communication link between the two parties are established; at this time, the signals received by the receiving antenna are useful signal s, co-site interference signal and noise, so that at this time The oversampled and extracted N-channel signals are x ₁ +s ₁ , x ₂ +s ₂ ,…,x _N +s _n , and any one of these N-channel signals is selected as the main channel signal, that is, x ₁ +s ₁ , and the others N-1 channel signals are used as reference channel signals, namely x ₂ +s ₂ , x ₃ +s ₃ ,…,x _N +s _n ; In the fifth step, input x ₂ +s ₂ , x ₃ +s ₃ ,…,x _N +s _n total N-1 reference channel signals into the first-stage filter, and keep the first-stage filter coefficients from Change, the error signal after subtracting the output signal of the first-stage filter and the main channel signal x ₁ +s ₁ is used as the input of the second-stage filter; The sixth step is to adjust the coefficients of the second-stage filter so that the power of the error signal obtained by subtracting the output signal of the second-stage filter from the main channel signal x ₁ +s ₁ is the smallest, and the output signal of the second-stage filter is useful signal for recovery. 2. An adaptive co-site interference cancellation method according to claim 1, wherein the received signal is sampled and then extracted into 2-8 signals, that is, the value of N is between 2-8. 3. The adaptive co-site interference cancellation method according to claim 1, wherein both the first-stage filter and the second-stage filter are adaptive filters. 4. A kind of adaptive co-site interference canceling device designed based on a kind of adaptive co-site interference canceling method described in claim 1, is characterized in that, mainly consists of decimator, first stage filter and second stage filter The input terminal of the decimator is coupled with the receiving antenna; one of the N output terminals of the decimator is connected to the control terminal of the first-stage filter and the control terminal of the second-stage filter, N-1 The output end of a reference channel is connected to the input end of the first-stage filter; the output end of the first-stage filter is connected to the input end of the second-stage filter, and the output end of the second-stage filter is coupled out to the input of the receiver end. 5 . The adaptive co-site interference cancellation device according to claim 4 , wherein the number N of output terminals of the decimator is between 2 and 8. 6 . 6. The adaptive co-site interference cancellation device according to claim 4, characterized in that, both the first-stage filter and the second-stage filter are adaptive filters.