CN101060354B - An intelligent antenna multi-channel calibration method under a strong interference condition - Google Patents

Abstract

The provided intelligent antenna multi-channel calibration method in strong-interference environment comprises: 1. a transistor sends the calibration signal to couple at least one signal, and a receiver receives the calibration signal; 2. the baseband process unit of the receiver processes the received signal and obtains the correlative result; 3. repeats (N) times for step 2, and calculates the result sum and average; 4. the process unit determines the correlation peak; ; and 5. the baseband process unit calibrates the channel according to its obtained correlation peak. This invention improves the calibration accuracy on strong-interference environment.

Description

A kind of intelligent antenna multi-channel calibration method under strong interference environment

Technical field

The present invention relates to a kind of intelligent antenna calibration method, relate in particular to a kind of intelligent antenna multi-channel calibration method under strong interference environment.

Background technology

At present, the wireless communication system operational environment is very complicated, and radio wave can be subjected to the electromagnetic interference of various electronics such as dissimilar radio transmitters or high pressure arc discharge, power equipment when free space is propagated.Disturbing the performance that can have a strong impact on wireless communication system under the more intense situation.

It has been generally acknowledged that,, think that promptly interference is arranged if instead surpass this thresholding if the low 9dB of the power ratio receiver sensitivity of unwanted signal in the receiver frequency band can think that so this signal does not disturb receiver.If unwanted signal has surpassed receiver sensitivity at receiver frequency band internal power, think that then having more intense interference, particularly interfering signal power to be higher than sensitivity 3dB will produce receiver performance when above and relatively seriously influence.

Can adopt intelligent antenna technology to solve above-mentioned unwanted signal interference problem at wireless communication field at present.Described intelligent antenna technology, be that wireless device uses antenna array, by calculate each subscriber signal aloft dissemination channel spatial signature vectors and with the received signal weighted sum of this spatial signature vectors and each antenna, thereby obtain than the more significant signal receiving gain of single antenna, i.e. " upper shaped gain "; Same wireless device is applied to spatial signature vectors in the down channel, also can obtain than the more significant signal receiving gain of single antenna, i.e. " downlink forming gain " in end.Owing to there is above-mentioned figuration gain, make wireless system can use less transmitting power to reach same coverage, reduced system cost effectively.

In order further to improve the performance of antenna system, also must calibrate it.A purpose of calibration is transmitting in the watt level unanimity of antenna opening of each sender of control, and phase place can accurately be controlled by the baseband processor of wireless device; Another purpose is the receiving sensitivity unanimity of each receiver of control.By the measurement to each transceiver, the adjustable gain controller of control receiver and transmitter radio frequency passage is so that carry out the calibration of power.In case calibrated the amplitude characteristic of each receiver and relative phase characteristic, just can the correct calculation spatial signature vectors, thus realize downlink forming gain.

Yet, in the wireless communication system that utilizes commonsense method that smart antenna is calibrated, still there is following problem: at first under strong interference environment, even the CDMA signal also can be suppressed by disturbed signal, directly rely on the spreading gain of CDMA signal to be not enough to suppress to disturb in this case; Secondly, the calibrating signal of wireless system might be flooded by disturbed signal, in this case, in order to guarantee the operate as normal of smart antenna, still needs each passage is calibrated.

Therefore, need design a kind of under strong interference environment the multi-channel calibration method of antenna system, improve the antijamming capability of wireless communication system.

Summary of the invention

The object of the present invention is to provide antenna system calibration steps under a kind of strong interference environment that can suppress to disturb, improve performance in wireless communication systems effectively.

Of the present invention under strong interference environment intelligent antenna multi-channel calibration method may further comprise the steps:

(1) one sender sends calibrating signal, and this calibrating signal is coupled at least one receiver through the smart antenna coupler, and described receiver receives described calibrating signal;

(2) thus the baseband processing unit of described receiver carries out relevant treatment to the calibrating signal that receives obtains the relevant treatment result one time;

(3) repeated execution of steps (2) is N time, and the baseband processing unit of described receiver adds up to the N correlations result that obtains and asks the mean value of this accumulation result;

(4) baseband processing unit of described receiver is determined relevant peaks according to the mean value that obtains;

(5) baseband processing unit of described receiver is determined the amplitude of passage to be calibrated and lag characteristic by the relevant peaks that obtains and described passage to be calibrated is calibrated.

Wherein, when receive path is calibrated, described sender is the calibrated channel sender, and described receiver is equipment receiver to be calibrated and described step (1) and then may further comprise the steps: a calibrated channel baseband processing unit is controlled described calibrated channel sender and sent calibrating signal.And when transmission channel was calibrated, described sender was an equipment sender to be calibrated, and described receiver is the calibrated channel receiver.

Preferably, when calibrating signal that described receiver receives was signal under the strong jamming condition, the baseband processing unit of described receiver carried out relevant treatment to this signal, is specially:

$r_{\mathrm{sy}}\left(\mathrm{\τ}\right)=\mathrm{\α}\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)s(t-\mathrm{\ζ}-\mathrm{\τ})\mathrm{dt}+\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)n(t-\mathrm{\τ})\mathrm{dt}$

Wherein, s (t) is a calibrating signal, and n (t) is an interference signal.

Preferably, the baseband processing unit of described receiver adds up to the N correlations result that obtains and asks the mean value of this accumulation result, is specially:

Order $\mathrm{\ϵ}\left(t\right)=\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)n(t-\mathrm{\τ})\mathrm{dt},$

$=\frac{1}{N}\mathrm{\Σa}\stackrel{+\∞}{\∫}s\left(t\right)s(t-\mathrm{\ζ}-\mathrm{\τ})\mathrm{dt}+\frac{1}{N}\mathrm{\Σ\ϵ}\left(\mathrm{\τ}\right)$

When τ=-during ζ, $E\left[r_{\mathrm{sy}}\left(\mathrm{\τ}\right)\right]=\mathrm{\α}\·P_s+\frac{1}{N}E\left[\mathrm{\Σ}\right[\mathrm{\ϵ}\left(\mathrm{\τ}\right)\left]\right]$

Wherein, P _sPower for calibrating signal.

Preferably, the baseband processing unit of described receiver is determined relevant peaks according to the mean value that obtains, and comprising:

Select the N value, when the N value is bigger, make

$\frac{1}{N}e\left[\mathrm{\Σ}\right[\mathrm{\ϵ}\left(\mathrm{\τ}\right)\left]\right]\≈\frac{{\mathrm{\σ}}_n}{\sqrt{N}}$

Wherein, б _nBe the power of interference and noise signal, when selected N value makes that the influence of interference signal can be ignored, can be from E[r _Sy(τ)] obtain the position of relevant peaks.

Preferably, determine the numerical value of N according to desired signal to noise ratio.

By using according to calibration steps of the present invention, can be so that calibrating signal obtain the gain higher than interference signal, thus suppress interference signal, improve the signal to noise ratio of calibrating signal.In addition, can obtain the characteristic vector of the calibrated channel of antenna system under the strong interference environment, thereby guarantee the correct spatial signature vectors that is used to calibrate of adjusting of antenna system, guarantee the stability of antenna system performance by the present invention.

Description of drawings

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described in further detail, wherein

Fig. 1 illustrates the system block diagram that adopts the inventive method antenna system to be carried out the receive path calibration;

Fig. 2 illustrates the flow chart that adopts the inventive method antenna system to be carried out the receive path calibration.

Embodiment

Wireless communication system generally includes smart antenna self radio receiver and a sender and an independent cover calibrated channel, and this calibrated channel also has receiver and the sender of oneself.When antenna system being carried out the receive path calibration, need the receiver of supporting use smart antenna and the sender of calibrated channel; Otherwise when antenna system being carried out the transmission channel calibration, need the sender of supporting use smart antenna and the receiver of calibrated channel.

The system block diagram that adopts the inventive method antenna system to be carried out the receive path calibration has been shown among Fig. 1.If calibrating signal is s (t), calibrating signal is promptly made a start from the calibrated channel sender that comprises the calibrated channel baseband processing unit and is sent, be coupled to receiving end by antenna coupler, described receiving end comprises the equipment receiver to be calibrated of at least one Gain Adjustable joint, is provided with equipment baseband processing unit to be calibrated in the described receiver to be calibrated.Be to be understood that and making a start and receiving end is provided with corresponding feeder line and A/D converter and D/A converter respectively according to the actual disposition situation of smart antenna.

Calibration must guarantee that calibrating signal can be by equipment reliable reception to be calibrated, the response of coupler must be linearly to become when non-, therefore the described calibrating signal that receives be y (t) its have only the loss of time-delay and amplitude with respect to s (t), therefore can be expressed as y (t)=α s (t-ζ), what α and ζ characterized is exactly the amplitude and delay (phase place) characteristic of calibrated channel.

Formula below described receiving end adopts carries out relevant treatment to the signal of receiving,

$r_{\mathrm{sy}}\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)y(t-\mathrm{\τ})\mathrm{dt}=\mathrm{\α}\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)\·s(t-\mathrm{\ζ}-\mathrm{\τ})\mathrm{dt}\≤\mathrm{\α}\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)\·s\left(t\right)\mathrm{dt}=\mathrm{\α}\·P_s$

Following formula is the correlation function of the received signal y (t) of calibrating signal s (t) and receiving end, and it characterizes the similarity degree (correlation) between these two signals, P _sBe the power of calibrating signal, when τ=-equal sign is set up during ζ, therefore finding relevant peaks (is r _SyMaximum (τ)) just can determine the amplitude and the lag characteristic of passage to be calibrated.

Under the strong jamming condition, establishing interference signal is n (t), y (t)=α s (t-ζ)+n (t) then,

$r_{\mathrm{sy}}\left(\mathrm{\τ}\right)=\mathrm{\α}\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)s(t-\mathrm{\ζ}-\mathrm{\τ})\mathrm{dt}+\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)n(t-\mathrm{\τ})\mathrm{dt}$

Order $\mathrm{\ϵ}\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)n(t-\mathrm{\τ})\mathrm{dt},$ Following formula is got N time average

$=\frac{1}{N}\mathrm{\Σ\α}\stackrel{+}{\∫}s\left(t\right)s(t-\mathrm{\ζ}-\mathrm{\τ})\mathrm{dt}+\frac{1}{N}\mathrm{\ϵ}\left(\mathrm{\τ}\right)$

Equally when τ=-during ζ, $E\left[r_{\mathrm{sy}}\left(\mathrm{\τ}\right)\right]=\mathrm{\α}\·P_s+\frac{1}{N}E\left[\mathrm{\Σ}\right[\mathrm{\ϵ}\left(\mathrm{\τ}\right)\left]\right],$

Wherein uncorrelated with calibrating signal owing to interference signal, when N is bigger, $\frac{1}{N}E\left[\mathrm{\Σ}\right[\mathrm{\ϵ}\left(\mathrm{\τ}\right)\left]\right]\≈\frac{{\mathrm{\σ}}_n}{\sqrt{N}},$ б _nBe the power of interference and noise signal, therefore, after N accumulation processing, the signal to noise ratio of the calibrating signal that receives can improve approximately

Doubly, and along with the increase of N, the influence of interference signal is more and more fainter, and after it reached a certain thresholding, the influence of interference signal can be ignored, at this moment from E[r _Sy(τ)] just can obtain the position of relevant peaks, thereby obtain calibrated channel amplitude and lag characteristic, also just obtain the characteristic vector of calibrated channel.

The target of calibration is gain and the phase characteristic that obtains passage to be calibrated, and relevant peaks peak value size has reflected the intensity of channel receiving signal to be calibrated, lag characteristic (being the position of relevant peaks) has then reflected the phase characteristic of passage to be calibrated, and calibrated channel enforcement calibration just can be treated in the peak value size and the position that therefore obtain relevant peaks.

The target of gain calibration is to make the received signal intensity of passage to be calibrated reach design objective, therefore the result to the N correlations adds up and the average signal strength signal intensity that has just obtained passage to be calibrated under a certain gain, make that by the gain of adjusting passage receiver to be calibrated its received signal intensity is consistent with design objective, gain calibration has just been finished.Under this gain, calculate the relevant average peak of N frame, obtain the lag characteristic of passage to be calibrated, just obtained the phase characteristic of passage to be calibrated.

By top analysis as can be known, according to the present invention, the principle of under strong interference environment antenna system being calibrated is mainly utilized incoherent feature between correlation properties between the calibrating signal and calibrating signal and the interference signal.Because calibrating signal all has correlation each other for a long time, therefore long-time cumulative mean makes calibrating signal strengthen, and interference signal and calibrating signal are uncorrelated, interference signal does not strengthen after the therefore long-time cumulative mean, so just make calibrating signal obtain the gain higher, thereby reach the effect that suppresses interference and improve the signal to noise ratio of calibrating signal than interference signal.

The flow chart that adopts the inventive method that the antenna system receive path is calibrated has been shown among Fig. 2.As shown in the figure, when the receive path of antenna system is calibrated, calibrated channel baseband processing unit control calibrated channel sender transmitting calibration signal, described calibrating signal receives by each receiver that antenna coupler is coupled to equipment to be calibrated, the quantity of receiver determines that when system design calibration need be calibrated all receivers; Each receiver links to each other with a baseband processing unit by method synthetic or that select, be that each receiver links to each other with baseband processing unit by a synthesizer or baseband processing unit selects a receiver to calibrate from a plurality of receivers, the hardware configuration of passage to be calibrated is depended in concrete method of attachment.This moment, described receiver might be received external interference signal simultaneously, and what therefore equipment receiver to be calibrated was received is the superposed signal of external interference signal and calibrating signal.The baseband processing unit of each receiver of equipment to be calibrated adopts the method for aforementioned calculating correlation function that original calibrated signal and calibrating signal that receive, the interference signal that superposeed are carried out relevant treatment.Each receiver receives N calibrating signal and also does relevant treatment, and the described equipment baseband processing unit that is calibrated is accumulated an above-mentioned N correlated results and accumulation results is averaged; The baseband processing unit of described receiver is determined relevant peaks according to the mean value that obtains.After determining relevant peaks, the baseband processing unit of described receiver is further determined the amplitude and the lag characteristic of passage to be calibrated according to relevant peaks.

Similar with above-mentioned employing the inventive method to the process that antenna system carries out the receive path calibration, can also adopt the inventive method that antenna system is carried out the transmission channel calibration.When carrying out the transmission channel calibration, each sender transmitting calibration signal of equipment to be calibrated, by the antenna coupler coupling, the calibrated channel receiver receives the calibrating signal of equipment emission to be calibrated; This moment, the calibrated channel receiver might be received external interference signal simultaneously, so the calibrated channel receiver receives is the stack of external interference signal and calibrating signal; The calibrated channel receiver carries out relevant treatment to calibrating signal that receive, the interference signal that superposeed; Calibrated channel receiver baseband processing unit is averaged after the result of N correlations is added up, and then above-mentioned mean value is sought relevant peaks; Determine the amplitude and the lag characteristic of passage to be calibrated by relevant peaks.

In above-mentioned two kinds of calibration processes, the times N that receiver receives calibrating signal all depends on desired signal to noise ratio.To different systems, the value of N can be different, for example is the cdma system of M for spread spectrum coefficient, and (signal to noise ratio improves because M spreading gain is doubly just arranged itself

Doubly), add the gain of N accumulation, the signal to noise ratio of then handling output promotes than input signal-to-noise ratio

Doubly, according to the needed signal to noise ratio of system, can calculate the numerical value of N.For the SCDMA system, M=32 when SNR 〉=16dB, can think that interference signal to not influence of calibration, therefore can get N=8.

It is also understood that calibration steps according to the present invention can be suitable for for various antenna systems, be not subjected to the smart antenna array form with and the antenna element limited in number that comprises.And this method not only can be used in the TDD wireless communication system and can also use in other wireless communication systems, and described calibrating signal also is not limited to the CDMA signal and can is various signals of communication simultaneously.

By using according to calibration steps of the present invention, can be so that calibrating signal obtain the gain higher than interference signal, thus suppress interference signal, improve the signal to noise ratio of calibrating signal.In addition, can obtain the characteristic vector of the calibrated channel of antenna system under the strong interference environment, thereby guarantee the correct spatial signature vectors that is used to calibrate of adjusting of antenna system, guarantee the stability of antenna system performance by the present invention.

Claims (6)

1. an intelligent antenna multi-channel Calibration Method under strong interference environment is characterized in that, said method comprising the steps of:

(1) one sender sends calibrating signal, and this calibrating signal is coupled at least one receiver through the smart antenna coupler, and described receiver receives described calibrating signal;

(2) thus the received signal that the baseband processing unit of described receiver receives calibrating signal carry out relevant treatment and obtain the relevant treatment result one time;

(3) each receiver execution in step (2) is N time, and the baseband processing unit of described receiver adds up to the N correlations result that obtains and asks the mean value of this accumulation result;

(4) baseband processing unit of described receiver is determined the relevant peaks of received signal and calibrating signal according to the mean value that obtains;

(5) baseband processing unit of described receiver is determined the amplitude of passage to be calibrated and lag characteristic by the relevant peaks that obtains and described passage to be calibrated is calibrated;

When receive path was calibrated, described sender was the calibrated channel sender, and described receiver is an equipment receiver to be calibrated; When transmission channel was calibrated, described sender was an equipment sender to be calibrated, and described receiver is the calibrated channel receiver.

2. method according to claim 1 is characterized in that, when receive path was calibrated, described step (1) and then may further comprise the steps: a calibrated channel baseband processing unit was controlled described calibrated channel sender and sent calibrating signal.

3. according to the described method of aforementioned claim 1, it is characterized in that, in the described step (2), when calibrating signal that described receiver receives is signal under the strong jamming condition, the baseband processing unit of described receiver carries out relevant treatment to this signal, is specially:

$r_{\mathrm{sy}}\left(\mathrm{\τ}\right)=\mathrm{\α}\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)s(t-\mathrm{\ζ}-\mathrm{\τ})\mathrm{dt}+\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)n(t-\mathrm{\τ})\mathrm{dt}$

Wherein, s (t) is a calibrating signal, and n (t) is an interference signal, and α and ζ represent the amplitude and the lag characteristic of calibrated channel respectively.

4. according to the described method of aforementioned claim 1, it is characterized in that in the described step (3), the baseband processing unit of described receiver adds up to the N correlations result that obtains and asks the mean value of this accumulation result, is specially:

Order $\mathrm{\ϵ}\left(\mathrm{\τ}\right)=\underset{-\∞}{\overset{+\∞}{\∫}}s\left(t\right)n(t-\mathrm{\τ})\mathrm{dt},$

When τ=-during ζ, $E\left[r_{\mathrm{sy}}\left(\mathrm{\τ}\right)\right]=\mathrm{\α}\·P_s+\frac{1}{N}E\left[\mathrm{\Σ}\right[\mathrm{\ϵ}\left(\mathrm{\τ}\right)\left]\right]$

Wherein, P _sBe the power of calibrating signal, s (t) is a calibrating signal, and n (t) is an interference signal, and α and ζ represent the amplitude and the lag characteristic of calibrated channel respectively.

5. according to the described method of aforementioned claim 1, it is characterized in that in the described step (4), the baseband processing unit of described receiver is determined relevant peaks according to the mean value that obtains, and comprising:

Select the N value, make

$\frac{1}{N}E\left[\mathrm{\Σ}\right[\mathrm{\ϵ}\left(\mathrm{\τ}\right)\left]\right]\≈\frac{{\mathrm{\σ}}_n}{\sqrt{N}}$

Wherein, б _nBe the power of interference and noise signal, when selected N value makes that the influence of interference signal can be ignored, can be from E[r _Sy(τ)] obtain the position of relevant peaks.

6. according to the described method of one of claim 1-5, it is characterized in that, determine the numerical value of N according to desired signal to noise ratio.

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