RU2562756C1 - Scanning antenna array, basic station, wireless communication network and method for formation of directivity pattern - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: number of feed channels of a scanning antenna array is less than the number of radiating elements and more than or equal to 2; with that, each channel has an individual constant power divider with fixed amplitude and phase distribution parameters. Weight coefficients are configured so that in total a cosecant directivity pattern of the antenna array can be formed. Scanning is performed by changing the phase at the inlet of at least one of the power dividers.

EFFECT: improving efficiency of scanning and formation of a multibeam directivity pattern in an antenna array already at availability of two radio-transmitting circuits.

14 cl, 10 dwg, 2 tbl

Description

FIELD OF THE INVENTION

The present invention relates to antenna technology, in particular to a scanning antenna array for spatial separation of channels in a wireless communication network, a base station, a wireless communication network, and a beamforming method.

State of the art

In modern mobile communication networks, there is a tendency to use antenna arrays containing many radiating elements. By controlling the phase and amplitude of the excitation at each radiating element, it is possible to dynamically control the direction of the emitted beam and the shape of the beam emitted by the array, or, in other words, to form a multi-beam radiation pattern (DD), which allows for multi-channel access to the network.

One of the typical solutions for multipath separation of communication channels is the so-called “smart” antenna (Smart Antenna), which is widely described in the literature, for example, in the “Antenna Theory analysis and design” third edition by Constantine A. Balanis, published by John Wiley & Sons 2005, pp. 949-954 (L1). A typical example of an “intelligent” antenna known in the art is shown in FIG. Such an antenna consists of a set of active transceiver elements A ₁ -A _n , which together constitute a single antenna array. The processor 25 of the base station "intellectually" controls the reception and transmission of signals in such a grid, due to which a large channel capacity is provided in the mobile communication network, as well as a large coverage area 26. However, the signal in each of the radiating elements is formed by the corresponding radio-frequency transceiver 24, and accordingly, with an increase in the number of radiating elements, the number of radio-frequency transceivers increases, which leads to a significant complication of the communication system, and as a result, it becomes more expensive in proportion to the number of radio channels.

The so-called adaptive antenna arrays are known in the art, in which only one radio frequency transceiver is used to generate signals in all radiating elements. One such solution is described, for example, in “Elevation radiation pattern shaping and control in broadband base station antenna arrays” by M. Barba, JE Page, JA Encinar, JR Montejo, ETSI Telecomunicación, Ciudad Universitaria s / n 28040 Madrid, SPAIN , Universidad Politécnica de Madrid, 12-14 Oct. 2005 (L2). The source of information L2 presents improved (in the frequency range and radiation pattern) planar antenna arrays designed to operate as part of mobile base stations in the GSM and UMTS bands (1710-2170 MHz). As shown in FIG. 5, an electronically controlled beamforming system according to L2 is formed by using a radio frequency power divider 29 having weight coefficients that make it possible to form a cosecant radiation pattern through the radiating elements 27. The signal from the divider 29 is transmitted to the emitters through switched phase shifters 28 Switchable phase shifters 28 are controlled by the processor of the base station 31 through a special control bus 30, which allows control iagrammoy orientation. As can be seen, with such a design, only one beam can be formed, which improves the energy ratio of the signal to noise, but due to the impossibility of forming a multi-beam radiation pattern, such a antenna array has a very limited channel capacity. In addition, despite the simplification of the communication system by reducing the number of radio frequency transceivers, for the sake of controlling the radiation pattern in such an adaptive antenna array, one has to use switchable phase shifters, which are also quite expensive and have relatively large losses for such high frequencies.

SUMMARY OF THE INVENTION

The objective of the present invention is to simplify the design of the base station while maintaining a high gain antenna array and multi-beam pattern without dips in the service area.

The above problem is solved by reducing the number of transceiver communication channels and the use of power dividers with fixed parameters for the distribution of amplitude and phase.

In accordance with one aspect of the present invention, there is provided a scanning antenna array in which the number of power channels is substantially less than the number of radiating elements and greater than or equal to 2, with each channel having a separate constant power divider with fixed amplitude and phase distribution parameters.

Scanning is performed by changing the phase at the input of at least one of the power dividers.

The weighting coefficients are configured so that in combination with the antenna array a cosecant radiation pattern is formed.

In one embodiment, the scanning antenna array is embodied on a printed circuit board.

In accordance with another aspect of the present invention, there is provided a base station comprising the antenna array described above.

In accordance with yet another aspect of the present invention, there is provided a wireless communication network comprising such a base station.

In accordance with a further aspect of the present invention, there is provided a beamforming method performed in the antenna array described above.

The present invention allows to significantly simplify the design of the base station and thereby reduce its cost and increase reliability.

Additionally, loss reduction is ensured and, as a result, energy efficiency is increased.

In addition, a relatively large channel capacitance, high gain, non-sagging DNs in the service area and a large scanning angle are provided.

The present invention offers an effective principle of forming an optimal antenna array radiation pattern with restrictions on the requirements for minimum amplification, uniformity of the coverage area, as well as a limited number of phased supply channels. Accordingly, the present invention makes it possible to upgrade legacy base stations with a small number of radio frequency channels by simply replacing the antenna.

In other words, the technical result is to increase the efficiency of scanning and the formation of a multi-beam radiation pattern in the antenna array even in the presence of two radio transmitting paths.

The above is a brief, non-limiting summary of the objectives, aspects, and advantages of the present invention. Additional features and advantages of the present invention will become apparent from the following detailed description of the invention.

Brief Description of the Drawings

Further, the present invention will be described in detail with reference to the accompanying drawings, in which:

1 is an illustration of a base station in a wireless communication network comprising an antenna array according to the present invention.

Figure 2a is a change in the radiation pattern of the antenna of the present invention with a common-mode and power-uniform distribution of weights.

Fig.2b is a change in the radiation pattern of the antenna presented in the present invention, with an uneven distribution of weight coefficients.

Figure 3 is an example of an optimal implementation of an antenna array.

4 is a block diagram illustrating the basic principle of construction and operation of a typical "smart" antenna.

5 is a block diagram illustrating the basic principle of the construction and operation of a typical phased array antenna with a controlled cosecant radiation pattern.

6a is an example of practical application of the antenna array according to the present invention.

Fig.6b is a simulation result showing the ratio of antenna gain and uniformity of coverage of the service area to the distance from the base station for the conventional antenna array and antenna of the present invention.

Fig. 7a is an example of a structural embodiment of an antenna array according to the present invention, consisting of 72 (8 × 9) printed microstrip antenna radiating elements, in which only two control channels are used for scanning in the vertical plane, and the vertical element of the linear antenna array consists of 2 sublattices with different numbers of radiating elements, 5 and 4.

Fig.7b is the result of the simulation of the radiation pattern in the vertical plane of the antenna proposed in the present invention and depicted in figa.

Detailed description

When developing the scanning antenna array proposed in the invention, preliminary modeling is necessary to determine its parameters depending on the required final characteristics of the antenna using well-known existing methods. Preliminary modeling includes the following steps.

In accordance with the required parameters of the antenna gain and the shape of the radiation pattern, based on the requirements of coverage of a certain service area, the required total number N of emitters is determined. Moreover, as a rule, the higher the required antenna gain, the greater the minimum required total number of emitters. On the other hand, the smaller the emitters, the antenna array as a whole is simpler and cheaper.

Then, based on the total number of emitters, antenna sublattices are formed, while the number of antenna sublattices can either be the minimum possible to provide the required radiation parameters (for example, amplification, radiation pattern), or can be predefined (for example, for the case of an inherited base station, already having a certain number of radio frequency channels (groups) of antenna power). As shown in the example of FIG. 1, two antenna sublattices 1 and 2 can be formed from N emitters, each of which contains n emitters. For example, n may be N / 2, and then the antenna sublattice 1 contains emitters A_eleven ... A_1n, and antenna sublattice 2 contains emitters A₂₁ ... A_2n.

Next, a suitable type of radiating elements A ₁₁ ... A _1n and A ₂₁ ... A _{2n of the} antenna array is selected for each of the antenna sublattices 1 and 2, depending on the requirements for the material and size of the antenna, for the operating frequency band, matching with the supply line to directionality, polarization, angle and plane of scanning. For example, a strip dipole emitter, a Vivaldi type emitter, or other radiating element known to a person skilled in the art can be selected as a suitable type. Preferably, the same type of emitter is selected for the entire antenna array.

After that, the size of the emitter is optimized. The size of the emitter can be inversely proportional to the operating frequency (or directly proportional to the wavelength). For example, in the case of a dipole radiator, the size can be approximately λ / 2, taking into account the shortening in the material.

Then, the arrangement of the selected radiating elements A ₁₁ ... A _1n and A ₂₁ ... A _{2n of the} antenna array as a single antenna array is optimized depending on the desired directivity, gain, side lobe level, polarization, angle and scanning plane.

Finally, based on the requirements for the coverage area and the requirements for the characteristics of the radiation and the scanning angle, we determine and optimize the weighting coefficients 3, 4 (W ₁₁ -W _1n and W ₂₁ -W _2n ) of the phase distribution and amplitude of each radiating element of each antenna sublattice in depending on the selected type of emitter and its place in the antenna array.

The preliminary modeling carried out in this way makes it possible to obtain an antenna array that meets the originally specified antenna requirements. That is, the antenna array is made of a certain number of sublattices in the sum of N emitters having certain parameters, and power dividers for powering the antenna sublattices are performed taking into account certain weighting factors.

Dynamic scanning in the antenna array obtained using this simulation is carried out by changing the amplitude and phase in at least one transceiver path by a value that is either determined at the stage of determining the weight coefficients, or due to the capabilities of existing equipment.

A basic block diagram illustrating a base station in a wireless communication network comprising an antenna array according to the present invention is shown in FIG.

The entire antenna array is divided into two completely independent antenna sublattices 1 and 2 with a relatively high own gain, for example, ≥12 dBi.

Both sublattices 1 and 2 are fed independently from each other using power dividers 5 and 6, taking into account the phase and amplitude weights 3 and 4 predefined as a result of modeling for each sublattice.

The radio frequency paths of the base station are similar to those used for "smart" antennas, and should be known to specialists in this field of technology, therefore, are not disclosed in detail in the present description. It should be noted that with the use of the proposed antenna array, it is sufficient to use only 2 transceiver radio paths. You can use more transceiver radio paths, but due to the fact that their number is significantly less than the total number of radiating elements in the antenna array (N _{RF ports} << N _ANTel ), the design of a base station with such an antenna is much simpler than with " intelligent "antennas.

Both power dividers 5 and 6 are connected to two independent transceiver channels, consisting of radio modules 7, 8 and digital modulators 9 and 10, respectively.

Dynamic scanning in the antenna array is carried out by changing the phase in at least one transceiver path by a predetermined value, as shown previously.

The entire digital base station as a whole is controlled through a single processor module 11, and a separate radio channel 13, 14 with a separately installed external antenna 12 is used to calibrate the emitted signal.

In this case, the power dividers according to the present invention are proposed to be performed using an uneven amplitude-phase distribution, since when implementing power dividers in accordance with the traditional approach based on uniform amplitude-phase distribution, a problem may arise that scan is very limited a small angle (figa), there is a high level of the side lobe, and the radiation pattern at the maximum angle simply splits into two parts, having at ohm stable deep zeros 17, which significantly reduces the service area.

A beam emitted along the normal 14 in FIG. 2a is formed when the weights are uniformly distributed in amplitude and phase. After a phase shift of one of the sublattices by 90 degrees, the beam is deflected (15) by only 5 degrees, and after a shift of 180 degrees, the maximum deviation (16) is obtained by 10 degrees, and the beam splits in two.

For uniform and similar distributions of amplitude-phase weight coefficients in the power supply circuit of the radiating elements, it is possible to achieve the maximum possible gain of the antenna array, but this results in a limited scanning angle, deep zeros 17 in the radiation pattern, and as the simulation shows, this directly affects the coverage of the zone signal service (explained below with reference to fig.6b).

Using the proper uneven distribution of the phases and amplitudes of the emitters, it is possible to obtain the necessary radiation pattern at various scanning angles. It should be noted that for antennas with low gain, the order of distribution of the weight coefficients does not matter much, since the directivity pattern of such antennas is wide. However, the higher the required antenna gain, the narrower its radiation pattern, which creates a serious problem for scanning at large angles in order to increase the coverage area, especially with a small number of power channels.

The task of selecting the weight coefficients so that with a small number of antenna supply channels (in order to simplify the design) simultaneously provide both high gain, a large channel capacity, a radiation pattern without dips in the service area, and a large scanning angle, is not trivial and requires significant efforts in finding the best solution.

The inventors have found that this problem can be solved by applying the amplitude-phase distribution, which allows you to get cosecant or close in shape to the pattern 18 (see fig.2b) so that the function is distributed simultaneously on two sublattices.

As a sample to demonstrate the effect of applying such a distribution, FIGS. 2a and 2b show radiation patterns obtained by simulating the same antenna array consisting of eight linearly mounted dipoles divided into 2 sublattices of 4 dipoles, but with two different settings weighting factors on each of the sublattices. As indicated above, scanning is carried out by changing the phase in one of the antenna sublattices.

For the above example of an array of eight elements (2 sub-arrays of 4 each), in one embodiment of the present invention, the following weight distribution can be applied:

Table 1
Weight distribution
for cosecant pattern Weight coefficient Amplitude Phase W ₁₄ 0.15 80 W ₁₃ 0.25 fifty W ₁₂ 0.5 45 W ₁₁ one 0 W ₂₁ one 0 W ₂₂ 0.5 -45 W ₂₃ 0.25 -fifty W ₂₄ 0.15 -80

In the above example, control is carried out in the sublattice 1 on one channel by changing the phase in the radio module 7 by a certain amount.

When a phase shift of −150 degrees is added to the first sublattice to the original cosecant radiation pattern 18 shown in FIG. 2b, the radiation pattern changes shape and deviates to the left (20), and to the right (19) with a phase shift of +150 degrees.

Figure 3 presents one of the possible embodiments of the design of the antenna array according to the present invention. Antenna array 21 is printed on a printed circuit board. Antenna array 21 contains two sublattices formed of eight radiating elements, four radiating elements in each sublattice. In addition, the antenna array 21 contains two constant power dividers 22 and 23, in which the amplitude-phase distribution of the weight coefficients 3 and 4 is shown in table 1. The phase distribution is realized by different lengths of the supply strips, and the amplitude distribution is realized by non-uniform strip dividers. At the input of each of the power dividers 22 and 23, a signal is received from the corresponding radio transmission path of the base station. When passing through the power dividers 22 and 23, the received signal is distributed and supplied to the respective radiating elements with the required amplitudes and phases, which correspond to the aforementioned predefined values. In this case, the antenna array as a whole forms a cosecant or close to cosecant radiation pattern.

When a phase-shift signal arrives from at least one transceiver path, the radiation pattern is rotated by a certain angle, whereby a scan is performed.

The result is a simple and cheap design with the ability to scan and requiring only two controllable power channels.

Thus, in the present invention, it is proposed to divide a single antenna array into two or more sublattices and to control them according to the “smart” antenna principle for implementing a multi-beam information transmission system. At the same time, despite the general similarity of the equipment disclosed in the present invention with the known devices of the prior art shown in FIGS. 4 and 5, the antenna array proposed in the present invention simplifies the design of the base station while maintaining a relatively large channel capacity.

It can be noted that the scanning principle according to the present invention makes it possible to replace conventional beam scanning by reconfiguring the radiation pattern with the main lobe moving and changing its width at half power level. Moreover, the structure and design of the base station is greatly simplified and, accordingly, its reliability is increased.

Also, as the inventors found, since the weight coefficients in amplitude and phase during the distribution according to the present invention are pre-fixed and different, it is possible not to optimize the distances between different pairs of elements (which, in essence, is also a fine tuning of the amplitude-phase distribution, but in small limits), but you can only lay the corresponding shifts of the amplitude and phase in the power dividers, so there is no need to make a non-equidistant antenna array, which further simplifies otsess development, and in some cases, the manufacture of the antenna.

In addition, according to the present invention, there is no need to use a large number of switchable phase shifters, which for high frequencies are quite expensive and have relatively large losses. That is, a reduction in losses is ensured and, as a result, energy efficiency is increased.

Moreover, this can significantly improve the distribution of multipath radiation over the coverage area of a mobile communication network using a limited number of radio communication channels (for example, two).

Additionally, the present invention allows to upgrade legacy base stations with a small number of radio frequency channels by simply replacing the antenna, thereby improving the efficiency of these base stations.

As a result of using the proposed constructive solution using, for example, the structure of the base station of FIG. 1, the network coverage area is divided into 3-4 sectors in which it is possible to independently serve a larger number of subscribers.

The antenna array according to the present invention can be used to form service areas both in the vertical plane and in the horizontal plane, depending on the design of the antenna array. It is most preferable to use it for elevation beam formation, as shown in figa and 6b.

6a shows a typical antenna installation of a base station 32 on a support mast 33.

The entire service area can be divided into three regions by elevation relative to the surface of the earth: near 34, central 35 and far 36 zones.

The simulation results of such an installation are shown in Fig.6b.

The following initial conditions were taken for simulation:

Mast Height 25 m

Antenna Tilt 10º

Total transmitter power in channels P _TX = 40 dBm

Transmitting antenna gain G _BSA = 10 dBi

Omni Directional Antenna Chart

Propagation of radio waves in free space without obstacles

The graph of FIG. 6b shows the signal strength received by the mobile device in dBm depending on the distance to the base station. The average level of the received signal is approximately -30 - -40 dBm, but in the case of a uniform amplitude-phase distribution of the weight coefficients of the antenna array, the power distribution 39 depending on the distance is very uneven, especially in the near zone 37, where the received signal decreases by more than 20 dB.

Moreover, when using the antenna array described in the present invention, the distribution 38 of the power of the received signal depending on the distance becomes essentially uniform, which significantly improves the operation of the communication network.

Another characteristic example of the design of the antenna array according to the present invention is shown in Fig. 7a, and Fig. 7b displays the result of a simulation of a change in the antenna pattern in the vertical plane. Position 40 in FIG. 7b is a radiation pattern without additional phase shifts between the upper and lower sublattices, position 41 displays the radiation pattern when the lower sublattice of four elements is shifted in phase relative to the upper one by -100 degrees, and position 42 displays the radiation pattern when shifting the upper sublattices relative to the bottom by -160 degrees.

The planar printed antenna array shown in Fig. 7a consists of 72 printed microstrip antenna radiating elements divided into 8 linear blocks of antenna sublattices to form narrow beams in the horizontal plane.

The antenna elements in the block are aligned and have the same polarization.

Each such linear antenna block consists of two asymmetric antenna sublattices with five and four radiating elements.

For the above example of an antenna array of nine elements (2 sublattices of 5 and 4, respectively), in this embodiment of the present invention, the following distribution of weights can be applied:

table 2
Distribution of weighting coefficients for obtaining a cosecant pattern in a linear antenna array consisting of two sublattices with 5 and 4 elements, respectively Weight coefficient Amplitude Phase W ₁₅ 0.1 90 W ₁₄ 0.15 80 W ₁₃ 0.25 fifty W ₁₂ 0.45 45 W ₁₁ one 0 W ₂₁ 0.75 -45 W ₂₂ 0.55 -fifty W ₂₃ 0.35 -80 W ₂₄ 0.3 -90

In the above example, control is carried out by changing the phase in the power channel of one of the sublattices relative to the other by a certain amount.

The use of two phased antenna sublattices with a different number of radiating elements and having an amplitude and phase distribution of weight coefficients in accordance with this invention in one antenna unit allows you to further increase the scanning area, as well as reduce the level of radiation of the parasitic side lobe.

Industrial applicability

The present invention can find the best application for antennas of base stations of the 4th and subsequent generations of mobile communication networks, which use technologies with multiple inputs and multiple outputs (MIMO) or multi-beam generation technology based on the principle of "smart" antenna.

Claims (14)

1. Antenna array containing:
M inputs
M sublattices formed sequentially from the total number N of radiating elements of the antenna array; and
M constant power dividers, each of which corresponds to a different one of M sublattices and a different one of M inputs, and is configured to
- receiving a signal from an input corresponding to this power divider, and
- distribution and supply of the received signal to the radiating elements contained in the sublattice corresponding to this power divider, with amplitudes and phases that correspond to predefined weight distribution coefficients of the amplitude and phase,
wherein M is an integer greater than or equal to 2,
N is an integer greater than M,
weight coefficients are configured so that in combination with the antenna array a cosecant or close to cosecant radiation pattern is formed, and
the input of at least one of the power dividers is further configured to receive a variable phase signal. 2. The antenna array according to claim 1, in which
M is 2
N is 8 and
weights are configured in accordance with
the following table:
Weight coefficient Amplitude Phase W ₁₄ 0.15 80 W ₁₃ 0.25 fifty W ₁₂ 0.5 45 W ₁₁ one 0 W ₂₁ one 0 W ₂₂ 0.5 -45 W ₂₃ 0.25 -fifty W ₂₄ 0.15 -80
where W _ij is the weight coefficient corresponding to the j-th radiating element in the i-th sublattice. 3. The antenna array according to claim 1, in which
M is 2
N is 9 and
weights are configured in accordance with the following table:
Weight coefficient Amplitude Phase W ₁₅ 0.1 90 W ₁₄ 0.15 80 W ₁₃ 0.25 fifty W ₁₂ 0.45 45 W ₁₁ one 0 W ₂₁ 0.75 -45 W ₂₂ 0.55 -fifty W ₂₃ 0.35 -80 W ₂₄ 0.3 -90 4. The antenna array according to claim 1, wherein the antenna array is made on a printed circuit board, and the radiating elements are dipole radiating elements. 5. The antenna array according to claim 1, wherein the antenna array has a linear configuration. 6. The antenna array according to claim 1, wherein the antenna array is intended for scanning along an elevation angle. 7. A base station in a wireless communication network containing an antenna array according to any one of paragraphs. 1-6. 8. A wireless communication network comprising a base station according to claim 7. 9. A method of forming a radiation pattern of an antenna array containing M inputs, M sublattices formed sequentially from the total number N of radiating elements of the antenna array, and M constant power dividers, each of which corresponds to a different one of M sublattices and to a different one of M inputs, containing stages in which:
receiving a signal in each of the M power dividers of the antenna array from the input corresponding to this power divider; and
distributing and supplying the received signal through each of the M power dividers of the antenna array to the radiating elements contained in the sublattice corresponding to this power divider, with amplitudes and phases that correspond to predefined weight distribution coefficients of the amplitude and phase,
wherein M is an integer greater than or equal to 2,
N is an integer greater than M,
weight coefficients are configured so that in combination with the antenna array a cosecant or close to cosecant radiation pattern is formed, and
in at least one of the power dividers, a variable phase signal is received. 10. The method according to p. 9, in which
M is 2
N is 8, and
weights are configured in accordance with the following table:
Weight coefficient Amplitude Phase W ₁₄ 0.15 80 W ₁₃ 0.25 fifty W ₁₂ 0.5 45 W ₁₁ one 0 W ₂₁ one 0 W ₂₂ 0.5 -45 W ₂₃ 0.25 -fifty W ₂₄ 0.15 -80
where W _ij is the weight coefficient corresponding to the j-th radiating element in the i-th sublattice. 11. The method according to p. 9, in which
M is 2
N is 9 and
weights are configured in accordance with the following table:
Weight coefficient Amplitude Phase W ₁₅ 0.1 90 W ₁₄ 0.15 80 W ₁₃ 0.25 fifty W ₁₂ 0.45 45 W ₁₁ one 0 W ₂₁ 0.75 -45 W ₂₂ 0.55 -fifty W ₂₃ 0.35 -80 W ₂₄ 0.3 -90 12. The method according to p. 9, in which the antenna array is made on a printed circuit board, and the radiating elements are dipole radiating elements. 13. The method according to p. 9, in which the antenna array has a linear configuration. 14. The method according to p. 9, and the method is designed to scan by elevation.

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