CN114994592A - DOA estimation method for OAM communication - Google Patents
DOA estimation method for OAM communication Download PDFInfo
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- CN114994592A CN114994592A CN202210531451.2A CN202210531451A CN114994592A CN 114994592 A CN114994592 A CN 114994592A CN 202210531451 A CN202210531451 A CN 202210531451A CN 114994592 A CN114994592 A CN 114994592A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
- G01S3/14—Systems for determining direction or deviation from predetermined direction
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
- H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
- H04B7/046—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account
- H04B7/0469—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account taking special antenna structures, e.g. cross polarized antennas into account
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- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention discloses a DOA estimation method for OAM communication, which comprises the following steps: the transmitting end estimates the elevation angle theta by OAM wave beams with different radiuses and different modes 0 (ii) a Fixed elevation angle theta of transmitting end 0 Estimating the deflection angle phi by beams with different radii and 0 mode 0 (ii) a The transmitting end obtains the beam deflection angle (theta) 0 ，φ 0 ) And realizing DOA estimation of a transmitting end. According to the invention, DOA estimation is carried out in two stages, firstly, the theta angle is estimated by adopting OAM wave beams with different radiuses and different modes, and then the phi angle is estimated by utilizing 0-mode wave beams with different radiuses.
Description
Technical Field
The invention relates to the technical field of wireless communication, in particular to a DOA estimation method for OAM communication.
Background
Uniform circular loop antenna arrays (UCAs) are often used in Orbital Angular Momentum (OAM) multiplexing communication systems in the microwave and millimeter wave frequency bands due to their flexible modulation and multiplexing characteristics. OAM is related to the spatial distribution of wave functions, is a fundamental property of all "vortex electromagnetic waves" in that a beam has a helical isophase surface and propagates along a helix. OAM has infinite orthogonal modes, theoretically, infinite multipath information can be carried and multiplexed and transmitted at the same time, so that a new degree of freedom of information multiplexing independent of time, frequency and polarization is provided, and the network capacity, the frequency spectrum efficiency, the anti-interference and anti-interception capabilities of a wireless communication system are expected to be improved in multiples. In 2007, B.thide et al experimentally demonstrated: OAM may be generated by feeding UCAs with equal amplitude and equal phase difference signals. As shown. Current UCA-based OAM communication research is mostly focused on the scenario of transceiving UCAs coaxially. However, the coaxial is greatly limited in the application scenario of OAM communication, and therefore, it is necessary to study OAM communication in a non-coaxial scenario.
There is still less research currently directed to non-coaxial OAM communication scenarios. The CHENG W proposes a precoding-postprocessing coding scheme in a paper of "improving Practical OAM Based Wireless Communications with Misalified Transceiver" for a non-coaxial OAM communication scene, and can restore a channel to be an interference-free parallel sub-channel. However, when this method is adopted, UCA-based OAM communication is degraded to MIMO communication in a general sense, and the characteristics of OAM communication are lost. In order to maintain the Beam characteristics of OAM, CHEN R proposes an OAM Beam deflection method in the article "Beam Steering for the Misalignment in UCA-Based OAM Communication Systems", which implements Beam deflection by adding a deflection phase shift on the UCA array elements at the transmitting and receiving ends. The method only considers the deflection characteristic in a general sense, and does not consider the constraint of OAM beam generation on the geometry of the transmitting and receiving array elements. When using the method in the text, the deflected OAM beams are distorted as only the deflection phases are added to the array elements. When the beam deflection angle is large, the OAM beam distortion is increased, and the modal orthogonality is reduced. Such methods are not inherently efficient methods for OAM beam deflection. In response to the above problems, YU W comprehensively considers the OAM Beam deflection requirements for phase and antenna array geometry in the paper "UCA Based OAM Beam Steering with High Mode Isolation [ J ]. IEEE Wireless Communications Letters". Aiming at a specific deflection angle, firstly, the position of a transmitting and receiving array element is adjusted, an array element structure is adjusted into a specified elliptical array, and on the basis of the specific array element structure, a one-dimensional linear phase weighting method is provided for realizing OAM wave beam deflection. Simulation shows that the method can ensure orthogonality of each mode of OAM while realizing beam deflection. In order to realize universality, a Square Grid Array (SGA) is adopted to realize an elliptical array at any angle, and the elliptical arrays with different axial ratios are selected from the square grid array to carry out multi-angle OAM communication. However, the specific angle OAM communication is performed on the premise that the transmitting and receiving ends acquire the deflection angle of the other party with respect to itself.
The OAM beam deflection is premised on that a transmitting end and a receiving end can obtain a deflection angle of an opposite side relative to the transmitting end and the receiving end, so that a beam deflection method is implemented aiming at the known deflection angle. Therefore, the estimation of the direction of arrival (DOA) by the transceiver end is a precondition for OAM deflected beam communication. The current DOA estimation method is mainly directed to MIMO millimeter wave DOA estimation in general situations. DOA estimation is generally implemented at the base station, and the base station estimates the angle of each terminal according to its strong digital and analog processing capabilities, thereby implementing high-speed communication with the mobile terminal. The traditional DOA estimation method generally defines a function, and gives estimation of an arrival angle according to a relation between a maximum value and an angle of the function, the function is conventionally called pseudo spectrum, and the pseudo spectrum is defined by the following methods: buttlett's method, minimum variance distortionless response method, maximum entropy method, Pisarenko harmonic decomposition method, minimum norm method, multiple signal classification (MUSIC) method, etc. The method is applied to the antenna array in a general form and has higher complexity. Aiming at the OAM communication scene based on UCA, a more efficient DOA estimation method needs to be designed by combining the specific geometric structure of UCA. Currently, there is little research on this area and western electrical researchers have done some work in this area. CHEN R in the article "Multi-mode OAM Radio Waves: an OAM Arrival Angle Estimation method based on UCA is proposed in Generation, Angle of Arrival Estimation and Reception With UCAs', and DOA Estimation is carried out by utilizing a plurality of subcarriers of OFDM and a plurality of modes of OAM. The approach herein incorporates the UCA geometry, however, it has been mentioned previously that strict OAM beam deflection cannot be achieved with UCAs. Therefore, it is necessary to research an efficient OAM beam DOA estimation method based on the SGA so that the transceiver can adaptively realize OAM high-speed communication at any angle in real time.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the defect that strict OAM wave beam deflection can not be realized by adopting UCA in the prior art, the invention discloses a DOA estimation method for OAM communication, which carries out DOA estimation in two stages, firstly adopts OAM wave beams with different radiuses and different modes to estimate an theta angle, and then utilizes 0-mode wave beams with different radiuses to estimate a phi angle, and has simple implementation and low complexity.
The technical scheme is as follows: in order to achieve the technical purpose, the invention adopts the following technical scheme.
A DOA estimation method for OAM communication, comprising the steps of:
the transmitting end estimates the elevation angle theta by OAM wave beams with different radiuses and different modes 0 ；
Fixed elevation angle theta of transmitting end 0 Estimating the deflection angle phi by beams with different radii and 0 mode 0 ；
The transmitting end obtains the beam deflection angle (theta) 0 ，φ 0 ) And realizing DOA estimation of a transmitting end.
Preferably, the coordinates of the beam deflection angle are constructed as: the method comprises the following steps that a transmitting terminal antenna and a receiving terminal antenna both adopt square grid arrays, an SGA central point is selected as a coordinate original point o at a transmitting terminal, a plane where the SGA is located is taken as an xoy plane, an x axis and a y axis are respectively selected as straight lines parallel to vertical edges of two edges of the SGA, and the straight lines are all taken from the original point o to the SGA edge as a positive direction; the straight line which passes through the o point and is perpendicular to the plane of xoy is the z axis, the positive direction of the z axis is upward, and the beam deflection angle (theta) of the receiving end relative to the transmitting end 0 ，φ 0 ) The angle of a vector v formed by a connecting line of a central point of the receiving end SGA and a central point of the transmitting end SGA in a transmitting coordinate system z-xoy is defined, the direction of the vector v is from the transmitting central point to the receiving central point, and the elevation angle theta is 0 Is defined as the included angle between the vector v and the z axis; deflection angle phi 0 Defined as the angle of the projection line of the vector v on the xoy plane with the y-axis.
Preferably, the estimating an elevation angle by the transmitting end with the OAM beams of different radii and different modes specifically includes:
the transmitting end scans by OAM wave beams with different radiuses and different modes and sends a first scanning wave beam to the receiving end;
the transmitting terminal obtains the elevation angle theta fed back by the receiving terminal 0 The elevation angle theta 0 And the first scanning beam is obtained by the receiving end through calculation.
Preferably, the transmitting end scans with OAM beams of different radii and different modes and sends out a first scanning beam to the receiving end, which specifically includes:
at the transmitting end, the radius of a uniform circular antenna array (UCA) which can be supported by the SGA is assumed to be r from small to large 0 、r 1 ...r N-1 For a radius r n The UCA of (a), which can support an effective OAM modality of 0.. l n Let the radius index be n and the modal index be l;
selecting radius r n For the selected UCA, setting the phase offset of each array element of the UCA according to the feeding method of the mode l, and transmitting a first scanning beam by a transmitting end in the selected UCA and the appointed OAM mode; until l is completed 0 n All radii, all modes of OAM beam scanning of N-1.
Preferably, the elevation angle θ 0 The method is obtained by the receiving end through the calculation of the received first scanning beam, and comprises the following steps:
the receiving end receives the first scanning beam and records the signal-to-noise ratio of each measurement as s n，l And simultaneously recording the corresponding radius mode combination (r) of the transmitting end of the measurement n ，l)。
Comparing the recorded signal-to-noise ratios s at the receiving end n，l Selecting the radius mode combination corresponding to the maximum signal-to-noise ratio
By combination of radius modes
Calculating elevation angle theta 0 。
Preferably, the passing radius modal combinations
Calculating elevation angle theta 0 The calculation formula comprises:
wherein the content of the first and second substances,
is the wave number and λ is the wavelength.
Preferably, the transmitting end fixed elevation angle θ 0 Estimating the deflection angle phi by beams with different radii and 0 mode 0 The method specifically comprises the following steps:
fixed elevation angle theta of transmitting end 0 Scanning with beams with different radiuses and 0 mode, and sending a second scanning beam to a receiving end;
the transmitting end obtains the deflection angle phi fed back by the receiving end 0 Said angle of deflection phi 0 And the second scanning beam is obtained by the receiving end through calculation.
Preferably, the second scanning beam design process comprises:
the transmitting end selects UCA with a preset radius, calculates a configuration phase for each antenna array element in the UCA, sets a variable phi to traverse in a [0, 2 ] section according to a UCA directional diagram, and transmits a second scanning beam; the second scanning beam is a 0 mode OAM beam; the number of the second scanning beams is the number of segments of the direction angle phi;
the receiving end receives all the second scanning beams, records the signal-to-noise ratio corresponding to each second scanning beam, and selects a variable phi corresponding to the maximum signal-to-noise ratio as a direction angle phi 0 And feeding back to the transmitting end.
Preferably, the step of setting a variable phi to traverse in [0, 2 pi ] in a segmented manner according to the UCA pattern and transmitting the second scanning beam comprises:
coarse scanning: the transmitting end selects the minimum radius r 0 The UCA calculates the configuration phase of each antenna array element in the UCA, and sets a variable phi to be 0, 2 pi according to a UCA directional diagram]Inner segment traversalThe number of scanning segments of the coarse scanning is M, and the scanning step length is
Transmitting a second scanning beam;
the receiving end receives M second scanning beams in the coarse scanning process, records the signal-to-noise ratio corresponding to each second scanning beam, selects the maximum signal-to-noise ratio, and records the coarse scanning angle range corresponding to the maximum signal-to-noise ratio and feeds the coarse scanning angle range back to the transmitting end;
fine scanning: the maximum radius r is selected by the transmitting end N-1 The UCA calculates the configuration phase of each antenna array element in the UCA, sets phi in a coarse scanning angle range according to a UCA directional diagram for sectional traversal, the scanning section number of fine scanning is Q, and the scanning step length is delta φ Emitting a second scanning beam;
the receiving end receives Q second scanning beams in the fine scanning process, records the signal-to-noise ratio corresponding to each second scanning beam, and selects phi corresponding to the maximum signal-to-noise ratio as phi 0 And feeding back to the transmitting end.
Preferably, the configuration phase is calculated for each antenna element in the UCA, and the calculation formula includes:
αi＝kr 0 sinθ o cos(φ-φ i )
wherein alpha is i Is the phase of the ith antenna element and phi is a variable used to determine the azimuth angle.
Has the advantages that: the DOA estimation is carried out in two stages, firstly, the theta angle is estimated by adopting OAM wave beams with different radiuses and different modes, and then the phi angle is estimated by utilizing 0-mode wave beams with different radiuses.
Drawings
FIG. 1 is a general process flow diagram of the present invention;
fig. 2 is a schematic diagram of an SGA-based deflected beam OAM communication scenario in embodiment 1;
FIG. 3 is a diagram illustrating beam angles θ of different modes in example 1;
fig. 4 is a schematic diagram of an OAM non-0 mode ring beam in embodiment 1;
fig. 5 is a schematic view of a fixed θ angle 0 mode beam scanning in embodiment 1.
Detailed Description
A DOA estimation method for OAM communication according to the present invention will be further described and explained with reference to the accompanying drawings and embodiments.
Description of the basic terms: the antenna unit (or antenna, antenna array element) is a single antenna, a plurality of antenna units are uniformly arranged according to the shape of a circular ring to form UCA, so the UCA is called a uniform circular ring antenna array, the transmitting and receiving end adopts SGA in the invention, namely the antenna units of the transmitting and receiving end are all arranged on a square grid to form a Square Grid Array (SGA). The central array element refers to the antenna element in the center of the SGA, for example, assuming that the number of antenna elements of the SGA used in the present invention is odd, such as 5 × 5 SGA, the position of the central array element is (3, 3). In the invention, the central array element of the SGA is taken as the center of the UCA (namely the center of a circular ring) to select approximate UCA on the SGA.
Example 1:
as shown in fig. 2, fig. 2 is a schematic diagram of a deflected beam OAM communication scenario based on an SGA (square grid array) in an embodiment of the present invention, and if a deflected beam OAM communication is to be performed, a transceiver first needs to acquire a beam deflection angle (θ, Φ) of an opposite side with respect to itself.
The embodiment discloses a DOA estimation method for OAM communication, which comprises the following steps:
the transmitting end estimates the elevation angle theta by OAM wave beams with different radiuses and different modes 0 ；
Fixed elevation angle theta of transmitting end 0 Estimating the deflection angle phi by beams with different radii and 0 modes 0 ；
The transmitting end obtains the beam deflection angle (theta) 0 ，φ 0 ) And realizing DOA estimation of a transmitting end.
In the actual communication scene, the beam deflection angle is estimated independently by both the transmitting side and the receiving side, namely the transmitting side has the beam deflection angle relative to the receiving side, the receiving side also has the beam deflection angle relative to the transmitting side, and the estimation methods of the two are the same, so that the invention only uses the receiving side to estimate the beam deflection angle independentlyFor the analysis of the beam deflection angle of the transmitting end as an example, in order to facilitate the expression of variable differentiation, the beam deflection angle of the receiving end relative to the transmitting end is given by (θ) 0 ，φ 0 ) As shown in fig. 2, the coordinate system establishing method is: the transmitting terminal antenna and the receiving terminal antenna both adopt a Square Grid Array (SGA), and at the transmitting terminal, the SGA central point is selected as a coordinate original point o, the plane where the SGA is located is taken as an xoy plane, an x axis and a y axis are respectively selected as straight lines parallel to two edge vertical edges of the SGA, and the straight lines from the original point o to the SGA edge are taken as positive directions. The straight line passing through the o point and perpendicular to the plane of xoy is the z axis, the positive direction of the z axis is upward, and a specific coordinate system is shown in the attached figure 2.
Beam deflection angle (theta) of the receiving end relative to the transmitting end 0 ，φ 0 ) A vector v formed by a connecting line between the center point of the receiving terminal SGA and the center point of the transmitting terminal SGA is defined (the vector direction is: from the transmit center point to the receive center point) in the transmit coordinate system z-xoy. Theta 0 Is the elevation angle, defined as the angle between vector v and the z-axis. Phi is a unit of 0 And the angle is defined as the included angle between the projection line of the vector v on the xoy plane and the y axis.
The method for carrying out OAM communication by adopting SGA to select array elements is characterized in that a plurality of circles with different radiuses or ellipses with different long and short axial lengths can be selected to carry out multi-angle OAM deflection beam communication. Firstly, OAM wave beams with different radiuses and different modes are adopted to estimate an angle theta, and then 0 mode wave beams with different radiuses are used to estimate an angle phi. The method is simple to implement and low in complexity. The method is suitable for all SGA-based deflection OAM beam communication systems.
As shown in fig. 1, a DOA estimation method for OAM communication includes the following steps:
s1, the transmitting end scans by OAM wave beams in different modes and sends out a first scanning wave beam;
s2, the transmitting end obtains the elevation angle theta fed back by the receiving end 0 Said deflection angle θ 0 The first scanning beam received by the receiving end is obtained through calculation;
s3, fixing and deflecting angle theta of transmitting end 0 Scanning in phi direction with 0 mode beam and emittingA second scanning beam;
s4, the transmitting end obtains the deflection angle phi fed back by the receiving end 0 Determining an angle of arrival (θ) 0 ，φ 0 ) Completing DOA estimation of the receiving end relative to the transmitting end; said deflection angle phi 0 And calculating a second scanning beam received by the receiving end.
The transmitting end obtains the beam deflection angle (theta) 0 ，φ 0 ) Realizing DOA estimation of the transmitting end, the beam deflection angle (theta) 0 ，φ 0 ) Only one refers to the overall relative angle of the transceiving ends.
In this embodiment, the specific step of step S1 includes:
at the transmitting end, the radius of UCA (uniform circular array antenna) supported by SGA (square grid array) is assumed to be r from small to large 0 、r 1 ...r N-1 For a radius r n The UCA of (a), which can support an effective OAM (orbital angular momentum) mode of 0.. l n (since the patterns of the positive and negative OAM modes are the same, only the positive mode needs to be used to transmit data here). Let the radius index be n and the modality index be l.
Step S11, selecting radius r n For the selected UCA, the phase offset of each array element of the UCA is set according to the feeding method of the Mode l, wherein, the method for setting the OAM generated phase Based on the UCA is known in the art, and refer to the article "UCA Based OAM Beam Steering with High Mode Isolation [ J ] of YU W].IEEE Wireless Communications Letters”。
Step S12, the transmitting terminal transmits a first scanning beam by the UCA selected in the step S11 and the appointed OAM mode;
step S13, i 0.. l n N-1 repeats steps S11 and S12. Wherein N is determined by the number of UCAs that the SGA can support, l n Is determined by the number of antenna elements included in the nth UCA.
The specific step of step S2 includes:
step S21, the receiving end central array element receives the first scanning beam and records the signal-to-noise ratio of each measurement as S n，l Are combined with each otherRecording the radius mode combination (r) of the transmitting terminal corresponding to the measurement n L). One radius, one mode, i.e. once (r) n L) corresponds to one first scanning beam, each first scanning beam having a corresponding signal-to-noise ratio. Fixed at the same radius n The multiple adjustments correspond to multiple first scanning beams, resulting in multiple signal-to-noise ratios.
Step S22, the receiving end compares the recorded signal-to-noise ratios S n，l Selecting the radius mode combination corresponding to the maximum signal-to-noise ratio
By combination of radius modes
Calculating elevation angle theta 0 ；
By combination of radius modes
Calculating the deflection Angle θ 0 The calculation formula of (c) is:
wherein the content of the first and second substances,
the wave number is a wave number, which is a parameter of an electromagnetic wave used for OAM communication, the wave numbers of a receiving end and a transmitting end are the same and are independent of a first scanning beam, lambda is a wavelength, the wave number of the electromagnetic wave used for OAM communication is the same and is independent of the first scanning beam, l is an OAM mode, and r is a UCA radius. Here, the radius modes are combined
Substituting the formula (1) to calculate to obtain the deflection angle theta 0 。
OAM beams have two distinct features: the beam main lobe gain has symmetry in the phi direction, namely the gain at any phi angle position is the same at the same theta angle; in the case of fixed UCA, the OAM beam angle increases with increasing modality.
As can be seen from fig. 3, the opening angle θ of the OAM beam increases as the mode increases, so that beam scanning in the θ direction can be performed by adjusting the mode. Fig. 4 is a schematic diagram of an OAM three-dimensional ring beam, and it can be seen from the figure that since the non-0 mode OAM beam is a ring beam, the gain is the same at any phi angular position at the same theta. This property is also true for the 0 mode of the non-circular beam. In addition, the width of the OAM beam main lobe decreases as the UCA radius increases. The accuracy of the beam sweep can be further improved by adjusting the size of the UCA radius.
According to the principle, the transmitting terminal antenna array can select UCAs with different radiuses, pilot signals are transmitted in different OAM modes, the receiving terminal receives signals and calculates the signal-to-noise ratio, the OAM mode and the UCA radius corresponding to the wave beam with the maximum signal-to-noise ratio are selected, the mode and the radius value are substituted into the formula (1), and the calculated corresponding theta is the estimated theta 0 I.e. the elevation angle of the receiving array in the theta direction relative to the transmitting array.
Step S23, the receiving end calculates the obtained theta 0 And feeding back to the transmitting end.
The specific steps of step S3 and step S4 include: the transmitting end obtains the theta calculated in the above step 0 Then, scanning with 0 mode beam to determine phi 0 The angle, namely:
fixed elevation angle theta of transmitting end 0 Scanning with beams with different radiuses and 0 mode, and sending a second scanning beam to a receiving end; as shown in FIG. 2, the beams with different radii and 0 mode are scanned in the phi direction to determine phi 0 And the phi-direction is the azimuthal direction in the horizontal plane. The second 0-mode scanning beam scans a variable phi between 0 and 2 under the condition of determining the elevation angle, the actual scanning range is the fixed elevation angle, and the phi takes a ring of 0 to 2.
The transmitting end obtains the deflection angle phi fed back by the receiving end 0 Said angle of deflection phi 0 Second by reception at the receiving endAnd scanning beam calculation is carried out.
After determining the deflection angle theta 0 Then, at this time, the 0 mode can be adopted to further determine phi 0 And (4) an angle. The 0 mode beam is not diverged, and a main lobe with strongest gain is arranged in the direction of the deflected beam, so that the complete deflection angle information can be determined by utilizing the characteristic. The UCA directional pattern function is shown in equation (2):
where (θ, φ) is the beam deflection angle, α i Is the phase of the ith antenna element, and I is the number of antennas in the selected UCA. Phi's' i I is the azimuth angle of the I-th antenna element, I1. The azimuth angles of the transmitting and receiving terminals to the antenna elements of the respective SGA (UCA) are known, so that phi 'here' i Are known. In this case, the above-determined θ can be used 0 The angle is substituted into θ in the above equation, and then φ is not traversed from 0 to 2, and the main lobe of the 0-mode beam is also not scanned from 0 to 2, as shown in FIG. 5.
The second scanning beam design process includes:
the transmitting end selects UCAs with preset radiuses, calculates configuration phases for each antenna array element in the UCAs, sets a variable phi to traverse in [0, 2 pi ] in a segmented mode according to a UCA directional diagram, and transmits a second scanning beam; the second scanning beam is a 0 mode OAM beam; the number of the second scanning beams is the number of segments of the direction angle phi;
the receiving end receives all the second scanning beams, records the signal-to-noise ratio corresponding to each second scanning beam, and selects a variable phi corresponding to the maximum signal-to-noise ratio as a direction angle phi 0 And feeding back to the transmitting end.
The variable phi is in [0, 2 pi ]]During the internal segmentation traversal, if only one scanning traversal is needed, the number of the required scanning segments is high, and the time consumption is long in order to obtain a more accurate result. Furthermore, since the main lobe width decreases with increasing UCA radius, i.e., the larger the UCA radius, the smaller the main lobe width, the higher the complexity of the beam scan with the same number of scanning segments. Based on thisThe invention adopts the method of coarse scanning and fine scanning. Firstly, UCA with smaller radius is selected on SGA, the 0-mode main lobe of the UCA is wider, the 0-mode main lobe is used for scanning in the phi direction, the scanning step length can be larger at the moment, after the phi angle rough range is determined, the fine scanning is carried out in the obtained rough range by the maximum UCA which can be supported, and the beam scanning complexity can be greatly reduced by adopting the beam scanning method from rough to fine. Similar to the estimation of the theta angle, for the 0 mode scanning beams at different angles, the receiving end receives the signals and calculates the signal-to-noise ratio, and the phi angle corresponding to the maximum signal-to-noise ratio is used as the estimated phi 0 And (4) an angle.
Specifically, the method comprises the following steps:
step S31, selecting radius r 0 (minimum radius) UCA, the phase of the selected antenna element is configured with reference to the UCA pattern function of equation (2):
α i ＝kr 0 sinθ 0 coS(φ-φ′ i ) (3)
α i is the phase of the ith antenna element, phi' i Is the azimuth angle of the ith antenna element, I1. i Are known; the variable φ in equation (3) is set to
(M can be determined based on UCA radius, ensuring that the width of the main lobe in the phi direction is approximately equal to
M-1) is given as j ═ 0. M is the number of scanning segments, i.e. dividing 2 pi angle into M segments to scan, and setting the scanning step length to be M
All mode beams need to be phase-adjusted by all array elements of the selected UCA according to a formula (3), namely all array elements of the UCA jointly adjust the phase to send out scanning beams.
The beamwidth of the 0 mode can be determined From UCA (see Yu W article "analysis UCA Based OAM Communication From Spatial Correlation[J]IEEE Access "), assuming 0-mode beam width at radius r as B r Then, then
The transmitting end transmits a second scanning beam to the antenna array element of the UCA with the phase configured by formula 3, i.e., the phase configuration of the 0-mode beam, where j is the beam index of the 0-mode scanning.
Step S32, the receiving end receives all the second scanning beams, and records the signal-to-noise ratio as S' 0，j The maximum signal-to-noise ratio is selected.
Suppose the scan angle index corresponding to the maximum SNR is j 0 The receiving end will scan the angle range roughly
And feeding back to the transmitting end.
Step S33, the radius of the transmitting end is selected to be r N-1 (maximum radius) UCA, theta in equation (3) has been set to theta 0 In the case of (2), set phi at
The beam scanning is carried out in a 0 mode within the range (the scanning step size is set according to the precision requirement). In the present invention, it is assumed that the step size is Δ φ Then the phi angle of each scan is
Step S34, the receiving end receives Q second scanning beams in the fine scanning process, records the signal-to-noise ratio corresponding to each second scanning beam, and selects phi corresponding to the maximum signal-to-noise ratio as phi 0 And feeding back to the transmitting end.
Step S35, the transmitting terminal receives phi 0 In combination with existing theta 0 And selecting an array element and setting the phase of the array element, thereby completing all settings of the deflection wave beam OAM communication. In this embodiment, the specific process implemented in step S35 can refer to the paper "UCA Based OAM Beam Steering with High Mode Isolation [ J ] of YU W].IEEE Wireless Communications Letters”。
And the two wave beam scanning processes adopt OAM wave beams, wherein the first scanning wave beam is continuously traversed through all the mode OAM wave beams which can be supported to carry out scanning, and the second scanning wave beam is only used for carrying out multi-direction scanning by using a 0-mode wave beam.
The receiving end can also adopt the steps to carry out DOA estimation, and then array elements are selected and phases are set. And after the receiving and transmitting end is set, the deflection wave beam OAM communication can be carried out.
The DOA estimation is carried out in two stages, firstly, the theta angle is estimated by adopting OAM wave beams with different radiuses and different modes, and then the phi angle is estimated by utilizing 0-mode wave beams with different radiuses.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention, and such modifications and adaptations are intended to be within the scope of the invention.
Claims (10)
1. A DOA estimation method for OAM communication, comprising the steps of:
the transmitting end estimates the elevation angle theta by OAM wave beams with different radiuses and different modes 0 ；
Fixed elevation angle theta of transmitting end 0 Estimating the deflection angle phi by beams with different radii and 0 modes 0 ；
The transmitting end obtains the beam deflection angle (theta) 0 ，φ 0 ) And realizing DOA estimation of a transmitting end.
2. The DOA estimation method for OAM communication as recited in claim 1, wherein said beam is formed from a plurality of beamsThe coordinates of the deflection angle are constructed as: the method comprises the following steps that a transmitting terminal antenna and a receiving terminal antenna both adopt square grid arrays, an SGA central point is selected as a coordinate original point o at a transmitting terminal, a plane where the SGA is located is taken as an xoy plane, an x axis and a y axis are respectively selected as straight lines parallel to vertical edges of two edges of the SGA, and the straight lines are all taken from the original point o to the SGA edge as a positive direction; the straight line which passes through the o point and is perpendicular to the plane of xoy is the z axis, the positive direction of the z axis is upward, and the beam deflection angle (theta) of the receiving end relative to the transmitting end 0 ，φ 0 ) The angle of a vector v formed by a connecting line of a central point of the receiving end SGA and a central point of the transmitting end SGA in a transmitting coordinate system z-xoy is defined, the direction of the vector v is from the transmitting central point to the receiving central point, and the elevation angle theta is 0 Is defined as the included angle between the vector v and the z axis; deflection angle phi 0 Defined as the angle of the projection line of the vector v on the xoy plane with the y-axis.
3. The DOA estimation method according to claim 2, wherein the transmitting end estimates an elevation angle with OAM beams of different radii and different modes, specifically comprising:
the transmitting terminal scans by OAM wave beams with different radiuses and different modes and transmits a first scanning wave beam to the receiving terminal;
the transmitting terminal obtains the elevation angle theta fed back by the receiving terminal 0 The elevation angle theta 0 And the first scanning beam is obtained by the receiving end through calculation.
4. The DOA estimation method according to claim 3, wherein the transmitting end sends a first scanning beam to a receiving end by scanning with different OAM beams with different radii and different modes, specifically comprising:
at the transmitting end, the radius of a uniform circular array antenna (UCA) supported by the SGA is assumed to be r from small to large 0 、r 1 ...r N-1 For a radius of r n The effective OAM mode supported by the UCA of (a) is 0 n Let the radius index be n and the modal index be l;
selecting radius r n For the selected UCA, feeding according to the mode lThe method comprises the steps that phase deviation of each array element of UCA is set, and a transmitting end transmits a first scanning beam in a selected UCA and a specified OAM mode; until l is completed 0 n All radii, all modes of OAM beam scanning of N-1.
5. A DOA estimation method for OAM communication as recited in claim 3, wherein said elevation angle θ 0 The method is obtained by the receiving end through the calculation of the received first scanning beam, and comprises the following steps:
the receiving end receives the first scanning beam and records the signal-to-noise ratio of each measurement as s n，l And simultaneously recording the corresponding radius mode combination (r) of the transmitting end of the measurement n ，l)。
Comparing the recorded signal-to-noise ratios s at the receiving end n，l Selecting the radius mode combination corresponding to the maximum signal-to-noise ratio
By combination of radius modes
Calculating elevation angle theta 0 。
6. A DOA estimation method for OAM communication according to claim 5, wherein said combining by radius modality
Calculating elevation angle theta 0 The calculation formula comprises:
wherein the content of the first and second substances,
is the wavenumber, and λ is the wavelength.
7. The DOA estimation method for OAM communication as recited in claim 2, wherein said transmitter end fixed elevation angle θ 0 Estimating the deflection angle phi by beams with different radii and 0 mode 0 The method specifically comprises the following steps:
fixed elevation angle theta of transmitting end 0 Scanning with beams with different radiuses and 0 modes, and sending a second scanning beam to a receiving end;
the transmitting end obtains the deflection angle phi fed back by the receiving end 0 Said angle of deflection phi 0 And the second scanning beam is obtained by the receiving end through the received second scanning beam calculation.
8. The DOA estimation method for OAM communication according to claim 7, wherein said second scanning beam design procedure comprises:
the transmitting end selects UCA with a preset radius, calculates a configuration phase for each antenna array element in the UCA, sets a variable phi to traverse in a [0, 2 pi ] section by section according to a UCA directional diagram, and transmits a second scanning beam; the second scanning beam is a 0 mode OAM beam; the number of the second scanning beams is the number of segments of the direction angle phi;
the receiving end receives all the second scanning beams, records the signal-to-noise ratio corresponding to each second scanning beam, and selects a variable phi corresponding to the maximum signal-to-noise ratio as a direction angle phi 0 And feeding back to the transmitting end.
9. The DOA estimation method for OAM communication as recited in claim 8, wherein said setting a variable Φ according to UCA pattern to traverse in sections within [0, 2 π ] and transmit a second scanned beam comprises:
coarse scanning: the transmitting end selects the minimum radius r 0 The UCA calculates the configuration phase of each antenna array element in the UCA, and sets a variable phi to be 0, 2 pi according to a UCA directional diagram]Internal segmentation traversal, the scanning segmentation number of the coarse scanning is M, and the scanning step length is
Transmitting a second scanning beam;
the receiving end receives M second scanning beams in the coarse scanning process, records the signal-to-noise ratio corresponding to each second scanning beam, selects the maximum signal-to-noise ratio, and records the coarse scanning angle range corresponding to the maximum signal-to-noise ratio and feeds the coarse scanning angle range back to the transmitting end;
fine scanning: the maximum radius r is selected by the transmitting end N-1 The UCA calculates the configuration phase of each antenna array element in the UCA, sets phi in a coarse scanning angle range according to a UCA directional diagram for sectional traversal, the scanning section number of fine scanning is Q, and the scanning step length is delta φ Emitting a second scanning beam;
the receiving end receives Q second scanning beams in the fine scanning process, records the signal-to-noise ratio corresponding to each second scanning beam, and selects phi corresponding to the maximum signal-to-noise ratio as phi 0 And feeding back to the transmitting end.
10. The DOA estimation method for OAM communication as recited in claim 8, wherein said computing a configuration phase for each antenna element in a UCA is performed according to a formula comprising:
α i ＝kr 0 sinθ 0 cos(φ-φ i )
wherein alpha is i Is the phase of the ith antenna element and phi is a variable used to determine the azimuth angle.
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