CN103516922B - Repeater echo cancelling device and method based on shift of frequency spectrum - Google Patents

Abstract

The invention provides a repeater echo cancellation device and method based on frequency spectrum shifting. The echo cancellation device includes a receiving module, a digital down-conversion module, a digital signal processing module, a small signal generation module, an addition module, a digital up-conversion module, a power amplifier module and a transmitting module. The present invention uses the method of spectrum shifting to generate small signals, and adds the small signals to the spectrum holes of the base station transmission signals, and realizes echo cancellation by using the characteristics that the small signals and transmission signals only have different frequency point positions and amplitudes. After the error is This method can realize echo cancellation without estimating the channel, and has strong practicability under fast time-varying channel conditions. The invention has low computational complexity, good real-time performance, simple hardware implementation, small error, and no need to estimate the channel, and there is no gradual convergence process of the error signal after offsetting.

Description

A Repeater Echo Cancellation Device and Method Based on Spectrum Shifting

technical field

The invention relates to an echo canceling method, in particular to a repeater echo canceling device and method based on frequency spectrum shifting.

Background technique

Most of the existing digital repeaters use the following technical principles to cancel the echo: by processing the transmitted signal and the received mixed signal containing echo noise, the characteristic parameters of the echo channel are estimated, and the An analog echo signal is generated internally in the repeater, which is subtracted from the received mixed signal to achieve echo cancellation. Since the echo channel is usually unknown and time-varying, an adaptive filter is generally used to estimate the echo channel. Among them, the adaptive filter based on the principle of minimum mean square error is the most widely used.

The principle of echo cancellation technology based on adaptive filter is: the transmitted signal is fed back to the internal adaptive estimator and internal filter while transmitting, and the adaptive estimator uses the signal and the error signal obtained after echo cancellation processing The external echo channel is estimated, and the estimated result is assigned to the filter. When the filter is equivalent to the external echo channel, the echo signal formed by the transmission signal coupled to the receiving antenna through the external echo channel is equal to the estimated echo signal output by the filter. After the subtraction operation, the two cancel each other out , so that the error signal only contains the donor signal (without considering the influence of channel noise).

The echo cancellation effect based on the above principle mainly depends on the estimation accuracy (or error) of the external echo channel by the adaptive estimator. For a time-varying channel, the speed of the approximation depends on the step size of the adaptive algorithm. The longer the step size, the faster the approximation speed, but the larger the error (that is, the lower precision); otherwise, the shorter the step size, the faster the approximation speed. Slower, but less error (i.e. higher precision). For mobile communication channels with strong time-varying characteristics, it is necessary to perform adaptive estimation on the echo channel in real time, which has certain requirements on the approximation speed, and because the approximation speed and error are a pair of unsolvable contradictions, so this In this case, it will inevitably lead to a large error in estimating the echo channel.

Contents of the invention

One of the purposes of the present invention is to provide a repeater echo canceling device based on frequency spectrum shifting, to solve the problem that the existing repeater echo canceling device needs to perform real-time self-correction of the echo channel under the fast time-varying channel condition. Adaptive estimation leads to the problem of large estimation error.

The second purpose of the present invention is to provide a repeater echo cancellation method based on frequency spectrum shifting, to solve the problem that the existing echo cancellation method based on adaptive filter makes the approximation speed and accuracy impossible under fast time-varying channel conditions. balance issue.

One of purpose of the present invention is achieved like this: a kind of repeater echo cancellation device based on frequency spectrum shifting, comprises:

The receiving module is connected with the digital down-conversion module, and is used to receive the base station signal and the echo signal formed by transmitting the signal through the echo channel, and send the received base station signal and the echo signal to the digital down-conversion module frequency conversion module;

The digital down-conversion module is respectively connected with the receiving module and the digital signal processing module, and is used for mixing the base station signal and the echo signal and converting it into a baseband signal, and then outputting the baseband signal to the digital Signal processing module;

The digital signal processing module is respectively connected with the digital down-conversion module, the small signal generation module and the addition module, and is used to pass through two filters whose center frequencies are respectively the first frequency ω ₁ and the second frequency ω ₂ . The baseband signal is filtered, and the signal formed after filtering by the filter whose center frequency is the first frequency ω ₁ contains the base station signal, and the second frequency ω ₂ is at the spectral hole of the base station signal frequency; the signal formed by the filter whose center frequency is the first frequency ω ₁ is denoted as the first branch signal s ₁ (t), and the signal formed by the filter whose center frequency is the second frequency ω ₂ is denoted by is the second branch signal s ₂ (t); the frequency spectrum of the second branch signal s ₂ (t) is shifted to the first frequency ω ₁ , and its amplitude is amplified by 1/k ₁ times, k _{1 <} 0.1, the signal to be canceled s _n (t) is formed; the signal to be canceled s n (t) is subtracted from the first branch signal s ₁ (t) to obtain the echo-cancelled signal s′( t), sending the echo-cancelled signal s'(t) to the small signal generation module and the addition module respectively;

The small signal generating module is respectively connected with the digital signal processing module and the adding module, and is used to receive the echo-cancelled signal s'(t) output by the digital signal processing module, and cancel the echo The spectrum of the rear signal s'(t) is shifted to the second frequency _ω2 , and then its amplitude is reduced to ₁ times of the original k to obtain a small signal y(t), and then the small signal y(t) output to the addition module;

The addition module is respectively connected with the digital signal processing module, the small signal generation module and the digital up-conversion module, and is used to make the echo cancelled signal s'(t) and the small signal y(t ) are added together to obtain a signal to be transmitted, and the signal to be transmitted is sent to a digital up-conversion module;

A digital up-conversion module is connected to the adding module and the power amplifier module respectively, and is used to process the signal to be transmitted to obtain a radio frequency signal with a higher frequency;

A power amplifier module is connected to the digital up-conversion module and the transmitting module respectively, and is used to amplify the power of the radio frequency signal and output it to the transmitting module; and

The transmitting module is connected with the power amplifier module and is used to transmit the amplified radio frequency signal as a transmitting signal.

The digital signal processing module of the present invention comprises:

The first filter module, connected with the subtraction module, is used to filter the baseband signal through a filter whose center frequency is the first frequency _ω1 , and the formed signal after filtering includes the base station signal; the center frequency will be The signal formed after filtering by the filter of the first frequency ω ₁ is recorded as the first branch signal s ₁ (t), and the first branch signal s ₁ (t) is sent to the subtraction module;

The second filtering module is connected with the spectrum anti-moving module, and is used to filter the baseband signal through a filter whose center frequency is a second frequency _ω2 , and the second frequency _ω2 is the frequency spectrum of the base station signal The frequency at the hole; the signal formed after filtering by the filter whose center frequency is the second frequency ω ₂ is recorded as the second branch signal s ₂ (t), and the second branch signal s ₂ (t) Send to the spectrum anti-move module;

The spectrum anti-shifting module is respectively connected to the second filtering module and the amplification module, and is used to perform spectrum anti-shifting on the second branch signal s ₂ (t) to the first frequency ω ₁ , and The signal after spectrum de-shifting is sent to the amplification module;

The amplification module is respectively connected with the spectrum anti-shift module and the subtraction module, and is used to amplify the amplitude of the signal after the spectrum anti-shift by 1/k ₁ times, k ₁ <0.1, to form the signal to be canceled s _n (t ), and then send the signal to be canceled s _n (t) to the subtraction module; and

The subtraction module is respectively connected to the first filter module and the amplification module, and is used to subtract the signal to be canceled s _n (t) from the first branch signal s ₁ (t) to obtain a return Signal s'(t) after wave cancellation.

The small signal generating module of the present invention includes a spectrum shifting module and a reduction module; the spectrum shifting module is used to shift the spectrum of the echo-cancelled signal s'(t) to the second frequency _ω2 and output For the reduction module, the reduction module is configured to reduce the amplitude of the signal whose spectrum is shifted to the second frequency _ω2 to k ₁ times the amplitude of the echo-cancelled signal s(t), thereby forming Small signal y(t).

In the present invention, the power of the small signal y(t) is smaller than the power of the signal s'(t) after echo cancellation, and the difference between the two is greater than 20 dB.

The small signal generation module in the present invention generates a small signal through spectrum shifting and amplitude reduction, and adds the generated small signal to the spectrum hole of the base station transmission signal, and the added small signal will not affect the coverage area of the repeater. Mobile phone users cause interference; the digital signal processing module filters the baseband signal through two filters to form two branch signals; one of the branch signals (including the signal after the small signal passes through the echo channel) is subjected to spectrum inversion and amplitude Amplify, and then use another branch signal (including the base station signal) to subtract the branch signal that has undergone spectrum inverse shift and amplitude amplification, so as to realize echo cancellation. Therefore, the device provided by the present invention can realize echo cancellation without estimating the channel, and is especially suitable for fast time-varying channels, so as to solve the problem caused by the need for real-time adaptive estimation of the echo channel under the condition of fast time-varying channels. The problem of large estimation errors.

Two of the purpose of the present invention is achieved like this: a kind of repeater echo cancellation method based on frequency spectrum shifting comprises the steps:

a. Repeater initialization;

b. The receiving module receives the base station signal and the echo signal formed by transmitting the signal through the echo channel, and sends the received base station signal and the echo signal to the digital down-conversion module;

c. The digital down-conversion module mixes the base station signal and the echo signal and converts it into a baseband signal, and then outputs it to a digital signal processing module;

d. The digital signal processing module performs cancellation processing on the baseband signal to obtain a signal s'(t) after echo cancellation, and sends the processing result to the small signal generation module;

e. The small signal generation module shifts the spectrum of the signal s'(t) after echo cancellation and reduces its amplitude to obtain a small signal y(t);

f. Add the small signal y(t) to the echo-cancelled signal s'(t), then perform digital up-conversion and power amplification to obtain a transmission signal, and finally transmit the transmission signal by the transmission module go out.

Step d of the present invention specifically includes the following steps:

d1: the digital signal processing module first filters the baseband signal through two filters whose center frequencies are respectively the first frequency _ω1 and the second frequency _ω2 ; the filter whose center frequency is the first frequency _ω1 The signal formed after filtering includes the base station signal, and the second frequency ω ₂ is a frequency at the frequency spectrum hole of the base station signal; the signal formed after filtering by a filter whose center frequency is the first frequency ω ₁ Denoted as the first branch signal s ₁ (t), the signal formed after the center frequency is the filter filtering of the second frequency ω ₂ is denoted as the second branch signal s ₂ (t);

d2: De-shift the spectrum of the second branch signal s ₂ (t) to the first frequency ω ₁ , and amplify its amplitude by 1/k ₁ times, k ₁ <0.1, to form the signal to be canceled s _n (t);

d3: Subtracting the signal to be canceled s _n (t) from the first branch signal s ₁ (t) to obtain the signal s'(t) after echo cancellation;

d4: sending the signal s′(t) after echo cancellation to the small signal generation module.

The step e of the present invention specifically includes: the small signal generation module shifts the spectrum of the signal s'(t) after echo cancellation to the second frequency _ω2 , and then shifts the spectrum to the second The amplitude of the signal at frequency ω ₂ is reduced to k ₁ times the amplitude of the echo-cancelled signal s′(t), thereby obtaining a small signal y(t).

The repeater echo cancellation method based on spectrum shifting in the present invention uses the spectrum shifting method to generate a small signal under the frequency selective fading channel model of the COST207 standard, and adds the small signal to the spectrum hole of the base station transmission signal, using The small signal and the transmitted signal only have the characteristics of different frequency points and amplitudes to achieve echo cancellation. The error after echo cancellation is on the order of 10 ^-14 . This method can realize echo cancellation without estimating the channel. Strong practicability under changing channel conditions. The invention has low computational complexity, good real-time performance, simple hardware implementation, small error, and no need to estimate the channel, and there is no gradual convergence process of the error signal after offsetting.

Description of drawings

Fig. 1 is a structural block diagram of a repeater echo cancellation device based on spectrum shifting in the present invention.

Fig. 2 is a schematic diagram of downlink signal flow when the repeater works in baseband according to the present invention.

Fig. 3 is a flow chart of the repeater echo cancellation method based on spectrum shifting in the present invention.

Detailed ways

Example 1

As shown in Figure 1, the repeater echo cancellation device based on spectrum shifting in the present invention includes a receiving module 1, a digital down-conversion module 2, a digital signal processing module 3, a small signal generation module 4, an adding module 5, a digital up-conversion module module 6, power amplifier module 7 and transmitting module 8.

The output terminal of the receiving module 1 is connected to the input terminal of the digital down-conversion module 2, the output terminal of the digital down-conversion module 2 is connected to the input terminal of the digital signal processing module 3, and the output terminals of the digital signal processing module 3 are respectively connected to the small signal generation module 4 and the The input end of the addition module 5, the output end of the small signal generation module 4 is also connected to the input end of the addition module 5, the output end of the addition module 5 is connected to the input end of the digital up-conversion module 6, and the output of the digital up-conversion module 6 The terminal is connected to the input terminal of the power amplifier module 7 , and the output terminal of the power amplifier module 7 is connected to the input terminal of the transmitting module 8 .

Combined with Figure 2 (the processing process from radio frequency signal to baseband signal is omitted in the figure), the receiving module 1 receives the echo signal formed by receiving the base station signal s(t) and the transmitted signal x(t) through the echo channel (or spatial channel) x'(t), and send the received base station signal s(t) and echo signal x'(t) to the digital down-conversion module 2; the digital down-conversion module 2 converts the base station signal s(t) and the echo signal The signal x'(t) is converted into a baseband signal x _n (t) after being mixed, and then the baseband signal x _n (t) is processed by the digital signal processing module 3 .

The digital signal processing module 3 includes a first filter module, a second filter module, a spectrum inverse shift module, an amplification module and a subtraction module.

The first filtering module is used to filter the baseband signal x _n (t) through a filter whose center frequency is the first frequency ω ₁ , and the signal formed after filtering is denoted as the first branch signal s ₁ (t), and the first branch The channel signal s ₁ (t) includes the base station signal s(t), and the first branch signal s ₁ (t) is output from the first filtering module to the subtraction module.

The second filter module is used to filter the baseband signal x _n (t) by a filter whose center frequency is a second frequency ω ₂ , and the second frequency ω ₂ is a frequency at the frequency spectrum hole of the base station signal s (t); The signal formed after filtering by the filter whose center frequency is the second frequency ω ₂ is denoted as the second branch signal s ₂ (t), and the second branch signal s ₂ (t) is output by the second filtering module to the spectrum inverse shifting module.

The spectrum anti-shifting module performs spectrum anti-shifting on the second branch signal s ₂ (t) to the first frequency ω ₁ , and then the amplification module amplifies the amplitude of the signal after the spectrum anti-shifting by k ₂ times (k ₂ in the present invention =1/k ₁ , k ₁ <0.1), to form the signal to be canceled s _n (t), and the signal to be canceled s _n (t) is sent to the subtraction module.

The subtraction module is used to subtract the signal s _n (t) to be canceled from the first branch signal s ₁ (t), so as to obtain the signal s′(t) after echo cancellation. The subtraction module can be realized by an adder.

The small signal generation module 4 includes a spectrum shift module and a reduction module. The spectrum shifting module is used to shift the frequency spectrum of the signal s'(t) after the echo cancellation to the second frequency _ω2 , and the reduction module is used to reduce the amplitude of the signal whose spectrum is moved to the second frequency _ω2 to the echo cancellation k ₁ times the magnitude of the subsequent signal s'(t), thus forming a small signal y(t). In order to reduce the interference of the small signal y(t) to the transmitted signal, the present invention makes the power of the small signal y(t) smaller than the power of the signal s'(t) after echo cancellation, and the difference between the two is greater than 20dB.

The addition module 5 is used to add the signal s'(t) after echo cancellation and the small signal y(t) to obtain the signal to be transmitted, and the signal to be transmitted is processed by the digital up-conversion module 6 to obtain a higher frequency radio frequency signal, Afterwards, the power amplifier module 7 performs power amplification, and finally the transmitting module 8 transmits the power amplified radio frequency signal as a transmitting signal x(t).

The adding module 5 can be realized by an adder.

Example 2

With reference to Fig. 3, the repeater echo cancellation method based on frequency spectrum shifting of the present invention comprises the following steps:

a. Repeater initialization;

b. The receiving end performs echo cancellation processing;

c. A small signal is generated after the frequency spectrum is shifted and reduced;

d. The small signal is added to the signal after echo cancellation and then transmitted through the transmitting module.

After the above step d is completed, continue to repeat step a, that is: this echo cancellation method is a cyclic process. With the continuous transmission of the transmitted signal, the receiving end receives the base station signal and the echo signal and performs cancellation processing, and then the small signal generates The module generates a small signal through spectrum shift and amplitude reduction, and the generated small signal is added to the transmit signal and transmitted together with the transmit signal, and the small signal will not cause interference to mobile phone users in the coverage area of the repeater.

Since the above-mentioned echo cancellation method is a cyclic process, it is acceptable to start from any step in the middle, and the detailed description will be started from step c below.

In combination with Figure 2, the signal s'(t) after echo cancellation is spectrum shifted to the second frequency ω ₂ (the second frequency ω ₂ is the frequency at the spectrum hole of the base station signal), and its amplitude is reduced to The original k ₁ times (k ₁ <0.1), the signal after amplitude reduction is recorded as a small signal y(t); the small signal y(t) and the signal s′(t) after echo cancellation are combined to form a mixed signal x(t) is transmitted, that is, the signal actually transmitted by the antenna is:

$x\left(t\right)={\mathrm{the\; s}}^{\&prime;}\left(t\right)+\mathrm{the\; y}\left(t\right)={\mathrm{the\; s}}^{\&prime;}\left(t\right)+k_1\&Center\; Dot;[{\mathrm{the\; s}}^{\&prime;}\left(t\right)\&Center\; Dot;e^{j{\mathrm{\&omega;}}_{2}t}],$ where k ₁ <0.1 (1)

In order to reduce the interference of the small signal y(t) to the transmitted signal, the present invention makes the power of the small signal y(t) smaller than the power of the signal s'(t) after echo cancellation, and makes the difference between the two larger than 20dB.

The transmission time of the small signal y(t) should be when the repeater has been initialized and is in working condition.

The sampling frequency of the small signal y (t) should be consistent with the sampling rate in the digital signal processing process of the repeater; for this reason, two buffers are set in the present invention, wherein the buffer 1 is used for buffering the base station received by the receiving antenna signal, buffer 2 is used for buffering the echo-cancelled signal s'(t) after the digital signal processing of the repeater; the buffer space of buffer 1 is at least twice that of buffer 2, so as to ensure that the receiving antenna at the receiving end can Continuously receive signals from the base station.

The specific process of sampling the small signal y(t) is: open the enabling switch of the buffer 2; calculate the small signal y(t) from the moment when the enabling switch of the buffer 2 is turned on, and store the small signal y(t) in In the register REG0; when the number of data in the register REG0 reaches N, the enabling switch of the buffer 2 is turned off, where N is the number of sampling points of the small signal y(t).

Then add the small signal y(t) in the register REG0 and the signal s'(t) after the echo cancellation of the buffer 2, and the mixed signal after the addition is processed by digital up-conversion and power amplification, and finally by The transmitting module transmits the signal.

Let the impulse response of the echo channel passed by the signal s′(t) and the small signal y(t) after echo cancellation be h(t) and h′(t) respectively, since the small signal y(t) is the After wave cancellation, the signal s′(t) is shifted to the signal at the second frequency _ω2 after frequency mixing, in order to ensure the small signal y(t) and the echo channel passed by the echo cancellation signal s′(t) have the same characteristics, so that Then the echo signal after the transmitted signal x(t) passes through the echo channel is:

${\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CircleTimes;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&CircleTimes;</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; ]</span>$

The mixed signal received by the receiving antenna at the receiving end is:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CircleTimes;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&CircleTimes;</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</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">\; 3</span>}<span\; class="notranslate">\; )</span>$

In formula (3), the echo channel attenuates the signal s′(t) after echo cancellation and the small signal y(t) exactly the same, and the spectral characteristics of the signal s′(t) after echo cancellation after passing through the echo channel are different. will change, so the base station signal s(t) and the signal belong to the same frequency band; while the signal ' is the signal after the echo-cancelled signal s(t) is shifted to the second frequency _ω2 after passing through the echo channel through the frequency spectrum, and the echo-cancelled signal s'(t) does not belong to the same frequency band, so from In the frequency domain, the mixed signal x _n (t) is mainly distributed in two frequency bands. Ideally, the two parts of the signal can be filtered out by designing two bandpass filters with different center frequencies.

The present invention filters the mixed signal x _n (t) through two band-pass filters whose center frequency is respectively the first frequency ω ₁ and the second frequency ω ₂ ; the band-pass filter whose center frequency is the first frequency ω ₁ The signal formed after filtering is denoted as the first branch signal s ₁ (t), and the signal formed after filtering by the band-pass filter whose center frequency is the second frequency ω ₂ is denoted as the second branch signal s ₂ (t).

According to theoretical analysis, the first branch signal s ₁ (t) and the second branch signal s ₂ (t) are respectively:

${\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CircleTimes;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&CircleTimes;</span><span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

The spectrum of the second branch signal s ₂ (t) is de-shifted to the first frequency ω ₂ , and its amplitude is amplified by k ₂ times, thereby forming the signal to be canceled s _n (t);

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; t</span>}}\mathrm{<span\; class="notranslate">\; d\&tau;</span>}\\ <span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}^{<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&infin;</span>}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&tau;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CircleTimes;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Afterwards, through the adder, the first branch signal s ₁ (t) and the second branch signal s ₂ (t) are subtracted after spectrum inversion and amplitude amplification, and the formula (7) is obtained:

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</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">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CircleTimes;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CircleTimes;</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

It can be known from the formula (7): when k ₂ ·k ₁ =1, s′(t)=s(t), at this time the echo is completely canceled.

The present invention adopts an ideal band-pass filter, and the change rules of the echo channel to the transmitted signal and the added small signal are exactly the same.

Claims (7)

1., based on a repeater echo canceller for frequency spectrum shift, it is characterized in that, comprising:

Receiver module, connects with Digital Down Converter Module, for receiving base station signal and the echo-signal formed after echo channel that transmits, and received described base station signal and described echo-signal is sent to Digital Down Converter Module;

Digital Down Converter Module, connects with described receiver module and digital signal processing module respectively, is converted to baseband signal, afterwards described baseband signal is exported to digital signal processing module after described base station signal and described echo-signal are carried out mixing;

Digital signal processing module, connects with described Digital Down Converter Module, small-signal generation module and summation module respectively, for being respectively first frequency ω by centre frequency ₁with second frequency ω ₂two filters filtering is carried out to described baseband signal, be first frequency ω by centre frequency ₁filter filtering after include described base station signal, described second frequency ω in the signal that formed ₂for being in the frequency at the spectrum interposition place of described base station signal; To be first frequency ω by centre frequency ₁filter filtering after the signal that formed be designated as the first tributary signal s ₁t () will be second frequency ω by centre frequency ₂filter filtering after the signal that formed be designated as the second tributary signal s ₂(t); By described second tributary signal s ₂t () carries out that frequency spectrum is counter to be moved to described first frequency ω ₁place, and its amplitude is amplified 1/k ₁doubly, k ₁< 0.1, is formed and treats offseting signal s _n(t); With described first tributary signal s ₁t () treats offseting signal s described in deducting _nt () thus signal s ' (t) after obtaining Echo Cancellation, be sent to described small-signal generation module and summation module respectively by signal s ' (t) after described Echo Cancellation;

Small-signal generation module, connect with described digital signal processing module and summation module respectively, for receiving signal s ' (t) after the Echo Cancellation that exported by described digital signal processing module, and signal s ' (t) after described Echo Cancellation is carried out frequency spectrum shift to described second frequency ω ₂place, then its amplitude is narrowed down to original k ₁doubly, obtain small-signal y (t), export described small-signal y (t) to summation module afterwards;

Summation module, connect with described digital signal processing module, described small-signal generation module and Digital Up Convert module respectively, be added to obtain signal to be transmitted for signal s ' (t) after making described Echo Cancellation and described small-signal y (t), and described signal to be transmitted is sent to Digital Up Convert module;

Digital Up Convert module, connects with described summation module and power amplifier module respectively, for processing to obtain radiofrequency signal to described signal to be transmitted;

Power amplifier module, connects with described Digital Up Convert module and transmitter module respectively, after described radiofrequency signal is carried out power amplification, exports to transmitter module; And

Transmitter module, connects with described power amplifier module, for the radiofrequency signal after power amplification being launched as transmitting.

2. the repeater echo canceller based on frequency spectrum shift according to claim 1, it is characterized in that, described digital signal processing module comprises:

First filtration module, connects with subtraction module, for being first frequency ω by centre frequency ₁filter filtering is carried out to described baseband signal, comprise described base station signal in the signal formed after filtering; To be first frequency ω by centre frequency ₁filter filtering after the signal that formed be designated as the first tributary signal s ₁(t), and by described first tributary signal s ₁t () is sent to subtraction module;

Second filtration module, connects with the anti-module of moving of frequency spectrum, for being second frequency ω by centre frequency ₂filter filtering is carried out to described baseband signal, described second frequency ω ₂for being in the frequency at the spectrum interposition place of described base station signal; To be second frequency ω by centre frequency ₂filter filtering after the signal that formed be designated as the second tributary signal s ₂(t), and by described second tributary signal s ₂t () is sent to that frequency spectrum is counter moves module;

Frequency spectrum is counter moves module, connects respectively with described second filtration module and amplification module, for by described second tributary signal s ₂t () carries out that frequency spectrum is counter to be moved to described first frequency ω ₁place, and the signal after counter for frequency spectrum moving is sent to amplification module;

Amplification module, instead with described frequency spectrum respectively moves module and subtraction module connects, for the amplitude of the signal after counter for frequency spectrum moving is amplified 1/k ₁doubly, k ₁< 0.1, treats offseting signal s to be formed _nt (), treats offseting signal s by described afterwards _nt () is sent to subtraction module; And

Subtraction module, connects with described first filtration module and described amplification module respectively, for making described first tributary signal s ₁t () treats offseting signal s described in deducting _nt () is to obtain signal s ' (t) after Echo Cancellation.

3. the repeater echo canceller based on frequency spectrum shift according to claim 2, is characterized in that, described small-signal generation module comprises frequency spectrum shift module and reduces module; Described frequency spectrum shift module is used for signal s ' (t) after described Echo Cancellation being carried out frequency spectrum shift to described second frequency ω ₂place also reduces module described in exporting to, described in reduce module for by frequency spectrum shift to described second frequency ω ₂the amplitude of signal at place is contracted to the k of the amplitude of signal s ' (t) after described Echo Cancellation ₁times, thus form small-signal y (t).

4. the repeater echo canceller based on frequency spectrum shift according to any one of claims 1 to 3, it is characterized in that, the power of described small-signal y (t) is less than the power of signal s ' (t) after described Echo Cancellation, and both differences are greater than 20dB.

5., based on a repeater echo counteracting method for frequency spectrum shift, it is characterized in that, comprise the steps:

A, repeater initialization;

B, receiver module receive base station signal and the echo-signal formed after echo channel that transmits, and received described base station signal and described echo-signal are sent to Digital Down Converter Module;

C, described Digital Down Converter Module are converted to baseband signal after described base station signal and described echo-signal are carried out mixing, export to digital signal processing module afterwards;

D, described digital signal processing module carry out counteracting process to obtain signal s ' (t) after Echo Cancellation to described baseband signal, and result is sent to small-signal generation module;

Signal s ' (t) after described Echo Cancellation is carried out frequency spectrum shift and reduces its amplitude, to obtain small-signal y (t) by e, described small-signal generation module;

F, described small-signal y (t) to be added with signal s ' (t) after described Echo Cancellation, to carry out Digital Up Convert, power amplification afterwards to be transmitted, finally by transmitter module, described transmitting is launched.

6. the repeater echo counteracting method based on frequency spectrum shift according to claim 5, it is characterized in that, described steps d specifically comprises the steps:

D1: first described digital signal processing module is respectively first frequency ω by centre frequency ₁with second frequency ω ₂two filters filtering is carried out to described baseband signal; Be first frequency ω by centre frequency ₁filter filtering after comprise described base station signal, described second frequency ω in the signal that formed ₂for being in the frequency at the spectrum interposition place of described base station signal; To be first frequency ω by centre frequency ₁filter filtering after the signal that formed be designated as the first tributary signal s ₁t () will be second frequency ω by centre frequency ₂filter filtering after the signal that formed be designated as the second tributary signal s ₂(t);

D2: by described second tributary signal s ₂t () carries out that frequency spectrum is counter to be moved to described first frequency ω ₁place, and its amplitude is amplified 1/k ₁doubly, k ₁< 0.1, treats offseting signal s to be formed _n(t);

D3: with described first tributary signal s ₁t () treats offseting signal s described in deducting _n(t) thus signal s ' (t) after obtaining Echo Cancellation;

D4: signal s ' (t) after described Echo Cancellation is sent to small-signal generation module.

7. the repeater echo counteracting method based on frequency spectrum shift according to claim 6, it is characterized in that, described step e is specially: signal s ' (t) after described Echo Cancellation is carried out frequency spectrum shift to described second frequency ω by described small-signal generation module ₂place, afterwards by frequency spectrum shift extremely described second frequency ω ₂the amplitude of signal at place is contracted to the k of the amplitude of signal s ' (t) after described Echo Cancellation ₁times, thus obtain small-signal y (t).