CN1622490A - Method and apparatus for implementing omnidirectional coverage of array antennas - Google Patents

Abstract

The invention relates to a method and device for realizing omnidirectional coverage of public channels in a smart antenna communication system. Utilizes all the existing antenna elements in the antenna array instead of selecting one or adding another antenna element, so there is no need to use high-power power amplifiers and high-gain antenna elements, thereby simplifying the structure and saving system costs. The device includes a common channel beamforming weight coefficient generator and M weight coefficient adjusters. Divide the transmission time of the common channel signal into time slots; N weight vectors are autonomously generated by the common channel beamforming weight coefficient generator; in each transmission time slot of continuous common channel signal transmission time slots, the N weight vectors are cyclically A weight vector is selected from the vector, and the M weight coefficient adjusters use the M weight coefficients in the weight vector to perform weighting corresponding to the common channel signals in the M transmission channels, and then correspondingly send M antenna elements for transmission. Both M and N are positive integers greater than 1.

Description

Method and device for realizing omni-directional coverage of array antenna

technical field

The present invention relates to the technical field of mobile communication, and more specifically relates to a method and a device for realizing omnidirectional coverage of public channels based on smart antennas.

Background technique

The array signal processing technology first appeared in the adaptive antenna combination technology. After that, the array antenna was first used in the military communication system. With the development of microcomputer and digital signal processing technology in recent years, it has also begun to be used in the civilian cellular mobile communication system. array antenna.

In the array antenna system, the system adaptively performs beamforming on the mobile user signal to track the user's movement, so the array antenna is also called a smart antenna array. In the Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system of the third generation mobile communication system, the smart antenna technology is treated as a key technology.

Referring to FIG. 1 , a schematic diagram of a steering vector of a smart antenna array. Assume that a smart antenna array for narrowband signals contains M>1 antenna elements, m is one of the M antenna elements, and the steering vector of the antenna array is a(θ), which is an M-dimensional column vector, given by The arrangement of the antenna elements is uniquely determined. If the first antenna element is taken as the reference point, the steering vector a(θ) of the antenna array can be expressed as (capital letters in bold represent matrix, lowercase letters in bold represent column vectors, ordinary letters represent scalars, the same below):

$\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\left[\begin{array}{cccc}\mathrm{<span\; class="notranslate">\; 1</span>}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; jr</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; k</span>}}& <span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>& {\mathrm{<span\; class="notranslate">\; e</span>}}^{{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; jr</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; k</span>}}\end{array}\right]}^{\mathrm{<span\; class="notranslate">\; T</span>}}$

In the figure, r _m is the distance vector from the mth antenna element to the reference point (m=2,...,M), k is the wave number vector in the direction of the θ angle, |k|=ω/c=2π/λ , ω is the carrier angular frequency, c is the speed of light, λ is the wavelength, where T is the transposition symbol.

Referring to Fig. 2, it shows a typical smart antenna system structure. The M receiving antennas correspond to the M receiving channels, and the M transmitting channels correspond to the M transmitting antennas.

For a specific user, the direction of arrival estimation module (DOA estimation) 21 estimates the direction of arrival information of the specific user according to the received signals on the M antenna elements. Adaptive beamforming weight coefficient generator 22 adjusts the weight vector according to the direction of arrival information of the specific user (adaptive beamforming weight coefficient generator 22 generates a weighting coefficient for each transmission channel, and the weight coefficient of each channel is adjusted The device 23 adjusts (multiplies) the dedicated channel signal s(t) with the weighting coefficient of its own channel, and the weighting coefficients w ₁ , w ₂ ... w _M of the M antenna array elements form a weight vector w, so that the specific user Form a pointing beam and adaptively track the user's movement. In the figure, * is a conjugate symbol.

After adopting the smart antenna technology, the interference of the system can be effectively reduced, the capacity of the system can be increased, and the spectral efficiency can be improved.

In the smart antenna system shown in Figure 2, the transmission channel of each antenna element is weighted by a weight coefficient (the weight coefficient is equal to the weight value), expressed as a weight vector:

w＝[w ₁ w ₂ ...w _M ] ^T

The direction coefficient of the antenna array in each direction is:

g(θ)=w ^H a(θ)

In the formula, H is the conjugate transposition symbol.

In a wireless communication system, in addition to dedicated channels for individual user communication, public channels such as broadcast channels and paging channels are also required. Public channels and dedicated channels have different requirements for antenna coverage: dedicated channels require the formation of beams that are as narrow as possible, while public channels require coverage of the entire cell, that is, omnidirectional coverage of public channels is required, so that all users can receive signals from the public channel. Disseminated public information. Therefore, after using the smart antenna in the mobile communication system, the antenna array has directivity, but appropriate technical measures need to be taken to meet the omnidirectional coverage requirement of the public channel.

One technique to achieve omnidirectional coverage of public channels is to use a single antenna array element to transmit. The specific method includes: selecting an antenna element in the array antenna to realize the omnidirectional coverage of the public channel; or adding another antenna element outside the antenna array, which is specially used to realize the omnidirectional coverage of the public channel.

In a smart antenna, due to the use of multiple antenna elements, the gain of the antenna can be reduced and the requirements for the power amplifier can be reduced. The much higher transmit power of the antenna elements (using high-power power amplifiers and high-gain antenna elements), thus increasing the system cost.

Contents of the invention

The object of the present invention is to design a method and device for omnidirectional coverage of array antennas. In a smart antenna communication system, the method and device for realizing omnidirectional coverage of public channels utilize all existing antenna array elements in the antenna array instead of One or another antenna element is selected, so there is no need to use a high-power power amplifier and a high-gain antenna element, thereby simplifying the system structure and saving system cost.

The object of the present invention is achieved through the following technical solutions:

A method for array antennas to achieve omnidirectional coverage, characterized in that it comprises the following processing steps:

A. Generate N weight vectors, denoted as w ₁ , w ₂ ...w _N , each weight vector is composed of M weighting coefficients, denoted as w ₁ , w ₂ ...w _M , M weighting coefficients correspond to M transmission channels, M transmission channels correspond to M antenna array elements, M and N are positive integers greater than 1;

B. Dividing the transmission time of the common channel signal into time slots;

C. Repeat this step, select a weight vector from N weight vectors w ₁ , w ₂ ... w _N in each transmission time slot of continuous public channel signal transmission time slots, and use the The _M weighting coefficients w ₁ , w ₂ .

The purpose of the present invention is also achieved through the following technical solutions:

A device for realizing omnidirectional coverage of an array antenna, the array antenna includes M antenna elements and M transmission channels corresponding to the M antenna elements, and is characterized in that:

Including a common channel beamforming weight coefficient generator and M weight coefficient adjusters;

The common channel beamforming weight coefficient generator generates N weight vectors, denoted as w ₁ , w ₂ ... w _N , and each weight vector includes M weight coefficients, denoted as w ₁ , w ₂ ... w _M ; In each transmission time slot of the continuous common channel signal transmission time, the common channel beamforming weight coefficient generator selects a weight vector from N weight vectors, and uses M weight coefficients in the weight vector to correspond to M For the transmission channel, the common channel signals in the M transmission channels are weighted by M weight coefficient adjusters, where M and N are positive integers greater than 1.

The present invention uses a common channel beamforming coefficient generator to generate N weight vectors (N is greater than 1); the signal transmission time for the common channel is divided into time slots; in each time slot, one is selected from the N weight vectors Weight vector, use the M weights (weighting coefficients) in the weight vector to correspond to the M transmission channels, and use the M weights in the M weight coefficient regulators to weight the M transmission channels respectively; use N weights cyclically Each weight vector in the vector.

Given a weight vector, that is, given a set of weighting coefficients, the pattern of the antenna array has a corresponding directivity, which is related to the arrangement of the antenna array and the weighting coefficients. At different times, each transmitting channel is weighted with different weighting coefficients, so that the pattern of the antenna array changes continuously. In a specific direction, the antenna gain exhibits strength changes over time, which is equivalent to a fast fading of a channel, and this fast fading can be overcome by channel coding and other technologies. From the perspective of the average effect, the gain of the antenna in each direction is basically the same, which is equivalent to an isotropic antenna array, thereby achieving the purpose of the present invention, that is, using all the antenna elements in the antenna array to realize the whole community of the common channel. to cover.

Compared with the single-antenna element transmission of the public channel, the technical solution of the present invention does not need to use a high-power power amplifier and a high-gain antenna element, thereby reducing system cost and simplifying the system structure.

Description of drawings

Fig. 1 is a schematic diagram of a steering vector of a smart antenna array;

FIG. 2 is a schematic structural diagram of a typical smart antenna system;

Fig. 3 is a device structure diagram and a flow chart of a method for realizing the omnidirectional coverage of a common channel by the array antenna of the present invention;

Fig. 4 is a schematic diagram of the expression pattern of the linear antenna array;

Fig. 5 is an effect diagram of the antenna array pattern after using the method and device of the present invention.

Detailed ways

Referring to FIG. 3 , the device for realizing omnidirectional coverage of an array antenna according to the present invention includes a common channel beamforming weight coefficient generator 31 and M weight coefficient adjusters 32 . Common channel beamforming weight coefficient generator 31 autonomously generates N weight vectors (N greater than 1), denoted as w ₁ , w ₂ , ..., w _N , each weight vector includes M weight coefficients, denoted as w ₁ , w _{2 ,} .

The transmission time of the common channel signal s(t) is divided into time slots, and in each transmission time slot, a weight vector is selected from N weight vectors. In consecutive transmission time slots, the N weight vectors are used in turn, that is, in each transmission time slot, each transmission channel is weighted by one weighting coefficient. The design of M weights in each of the N weight vectors makes the average gain of the antenna array pattern weighted by the N sets of weights be isotropic. Generally speaking, the above purpose can be achieved by selecting two weight vectors (N=2), that is, two sets of weight values.

The present invention realizes omnidirectional coverage of public channels by designing each weight vector and a group of weighting coefficients in each weight vector, and using all antenna array elements in the array antenna.

The present invention will be further described below by taking a linear array as an example.

See Figure 4, for a linear array, the expression of its pattern is: $g\left(\mathrm{\&theta;}\right)=\underset{m=1}{\overset{m}{\mathrm{\&Sigma;}}}{w}_m^{*}{e}^{-j\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}(m-1)d\sin \mathrm{\&theta;}},$

In the formula, d is the spacing between antenna array elements, as shown in Figure 4.

If the antenna array has 8 antenna elements, M=8, and the distance d between the antenna elements is half a wavelength λ/2, two weight vectors (N=2), that is, two sets of weight coefficients, are selected as:

w ₁ =[1 1 1 -1 1 -1 1 1]

w ₂ =[1 i -1 i 1 -i -1 -i]

These two weight vectors are automatically generated by the common channel beamforming weight coefficient generator, and each weight vector includes 8 weight coefficients. The direction diagrams of the two weight vectors are required to be complementary, that is, the average value of the direction diagrams of the two weight vectors is approximately isotropic. As long as the generation principle is in place, the public channel beamforming weight coefficient generator generates weight vectors according to the principle, and there may be various implementation techniques, which will not be listed here.

The transmission time of the common channel signal is divided into time slots. In the first transmission time slot, select a weight vector from these two weight vectors, such as w ₁ =[1 1 1 -1 1 -1 1 1], use the corresponding weight coefficient in the 8 weight coefficient adjusters Weight the common channel signal s(t), that is, use 1 to weight the common channel signal s(t) in the transmission channel 1, and use 1 to weight the common channel signal s(t) in the transmission channel 2, .. ., use -1 to weight the common channel signal s(t) in transmission channel 4, ..., use 1 to weight the common channel signal s(t) in transmission channel 8. In the second transmission time slot, select another weight vector from these two weight vectors, w ₂ =[1 i -1 i 1 -i -1 -i], use corresponding The weighting coefficient of the common channel signal s(t) is weighted, that is, the common channel signal s(t) in the transmission channel 1 is weighted by 1, and the common channel signal s(t) in the transmission channel 2 is weighted by i , use -1 to weight the common channel signal s(t) in the transmission channel 3, ..., use -i to weight the common channel signal s(t) in the transmission channel 8 (i is an imaginary number unit). In the third transmission time slot, the common channel signal s(t) is weighted by w ₁ =[1 1 1 -1 1 -1 1 1]. . . .

The two weight vectors, that is, the direction diagrams of the two groups of weight coefficients are complementary. In any direction, the direction diagram gain of one group of weight coefficients is weak, and the direction diagram gain of the other group of weight coefficients is strong, forming a complementarity, as shown in Figure 5 Superposition of the two orientation patterns shown.

In Figure 5, the solid line is the direction diagram when the weight vector w ₁ is used, and the gain is the strongest in the directions of 0°, 90°, 180°, and 270°, and the gain is the strongest in the directions of 60°, 120°, 240°, and 300°. Weak; the dotted line is the direction diagram using the weight vector w ₂ , the gain is the strongest in the directions of 60°, 120°, 240°, and 300°, and the gain is the weakest in the directions of 0°, 90°, 180°, and 270°. Therefore, omnidirectional coverage can be achieved by using these two weight vectors and two sets of weighting coefficients alternately.

The technical scheme of the present invention makes full use of the transmission power of all antenna elements in the antenna array, avoiding the use of high-power power amplifiers and high-gain antennas in order to achieve omnidirectional coverage of public channels in the smart antenna system, making the system Simplified and cost saved.

Claims (6)

1. an array antenna is realized the method that omnidirectional covers, and it is characterized in that comprising following treatment step:

A. produce N weight vector, be designated as w ₁, w ₂... w _N, each weight vector is made of M weight coefficient, is designated as w ₁, w ₂... w _M, M corresponding M transmission channel of weight coefficient, M corresponding M bay of transmission channel, M, N are the positive integers greater than 1;

B. launch time of common channel signal is divided into time slot;

C. repeat this step, at each transmission time slot of continuous common channel signal transmission time slot, from N weight vector w ₁, w ₂... w _NIn choose a weight vector, with the M in this weight vector weight coefficient w ₁, w ₂... w _M, the common channel signal in the corresponding M transmission channel is weighted, and correspondence is sent M bay emission.

2. array antenna according to claim 1 is realized the method that omnidirectional covers, and it is characterized in that: described common signal channel wave beam forming weight coefficient generator shows as N weight vector of near-isotropic generation by the mean value of the directional diagram of N weight vector.

3. array antenna according to claim 1 is realized the method that omnidirectional covers, and it is characterized in that: among the described step C, describedly choosing a weight vector, is according to weight vector w ₁, w ₂... w _NSequence number, choose each weight vector in proper order at continuous transmission time slot.

4. an array antenna is realized the device that omnidirectional covers, array antenna comprise M bay and with M M the transmission channel that bay is corresponding, it is characterized in that:

Comprise a common signal channel wave beam forming weight coefficient generator and M weight coefficient adjuster;

Common signal channel wave beam forming weight coefficient generator produces N weight vector, is designated as w ₁, w ₂... w _N, each weight vector comprises M weight coefficient, is designated as w ₁, w ₂... w _MAt continuous common channel signal each transmission time slot of launch time, common signal channel wave beam forming weight coefficient generator is chosen a weight vector from N weight vector, with the weight coefficient of the M in this weight vector, corresponding M transmission channel, by M weight coefficient adjuster the common channel signal in M the transmission channel is weighted, M, N are the positive integers greater than 1.

5. array antenna according to claim 4 is realized the device that omnidirectional covers, and it is characterized in that:

N the weight vector that described common signal channel wave beam forming weight coefficient generator circulation produces, the mean value of the directional diagram of N weight vector shows as near-isotropic.

6. array antenna as claimed in claim 4 is realized the device that omnidirectional covers, and it is characterized in that:

Described common signal channel wave beam forming weight coefficient generator is chosen a weight vector from N weight vector, be according to weight vector w ₁, w ₂... w _NNumeric order choose each weight vector, described common channel signal is weighted.

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