Dual-band reconfigurable antenna array design and beam forming method

Abstract

The invention discloses a sub-6GHz and millimeter wave dual-band reconfigurable antenna array design and beam forming method, on one hand, a sub-6GHz band antenna is formed by multiplexing a millimeter wave band antenna, and the space occupation overhead of the antenna array is saved; and on the other hand, the PIN diode is connected with the millimeter wave array, and the millimeter wave antenna forming the sub-6GHz frequency band antenna is flexibly selected by controlling the on-off of the PIN diode, so that the freedom degree of the sub-6GHz design is increased. The beam forming design of the array maximizes the millimeter wave frequency band communication and rate under the constraint of satisfying the sub-6 GHz frequency band communication quality and perception quality, can fully utilize the signal characteristics of the sub-6 GHz frequency band and the millimeter wave frequency band, and effectively deals with actual complex and diversified channels.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a dual-band reconfigurable antenna array design and a beamforming method. Background Art

[0002] The sixth generation of wireless communication (6G) technology has attracted widespread attention in academia and industry. With its unprecedented high speed, low latency and potential for large-scale connectivity, 6G will promote the development of many new application scenarios. For 6G wireless networks, sub-6GHz bands (bands below 6GHz) and millimeter wave bands are crucial. The millimeter wave band, due to its abundant spectrum resources, can achieve high data transmission rates and is very suitable for dense urban environments and applications that require large data throughput. However, high path loss limits its effective coverage. In contrast, the sub-6GHz band provides a wider coverage area and is more suitable for wide-area connectivity, but its data transmission rate is lower. In addition, the millimeter wave band has a shorter wavelength and more antennas, which can achieve higher-precision perception than the sub-6GHz band. Taking full advantage of the advantages of these two bands, so that 6G networks can achieve high-speed communication and high-precision perception while ensuring communication reliability and coverage, is crucial to realizing the full potential of 6G networks. On the other hand, since the antenna size is directly related to the carrier wavelength, there is a significant difference in size between sub-6GHz antennas and millimeter wave antennas. In order to fully utilize the advantages of these two frequency bands, base stations usually need to be equipped with independent sub-6GHz antennas and millimeter wave antennas, which leads to an increase in the space occupied by the antenna. In order to save space, in the literature [1], the authors proposed a dual-band antenna that can operate in the sub-6GHz and millimeter wave bands. These antennas integrate multiple millimeter wave antennas into a sub-6GHz antenna, realizing aperture sharing between frequency bands (literature [1]: L. Sang et al., "A dual-band planar antenna array with high-frequency ratio for both Sub-6band and mm-Wave band," IEEE Trans. Antennas Propag., vol. 71, no. 5, pp. 3856–3867, May 2023). However, because the position of the dual-band antenna cannot dynamically adapt to the changing channel state information, the design freedom is very limited.In order to increase the degree of design freedom, in the literature [2], the authors used an antenna selection method to select some arrays from the pre-arranged arrays to dynamically adapt to the changing channel state information (literature [2]: Y. Gao, H. Vinck and T. Kaiser, "Massive MIMO antenna selection: Switching architectures capacitybounds and optimal antenna selection algorithms", IEEE Trans. Signal Process., vol. 66, no. 5, pp. 1346-1360, Mar. 2018.). However, this method is limited by the spacing of the pre-arranged arrays, and a large number of arrays require a large hardware overhead. To this end, the present invention proposes a millimeter wave and sub-6GHz dual-band reconfigurable antenna array architecture design to achieve dual-band functions, save hardware overhead, and flexibly design the antenna array arrangement according to actual channel state information. In terms of beamforming architecture, since there are fewer sub-6 GHz antennas, the all-digital architecture in reference [3] can be used (reference [3]: R. Li, Z. Xiao and Y. Zeng, "Towards seamless sensing coverage for cellular multi-static integrated sensing and communication", IEEE Trans. Wireless Commun., vol. 23, no. 6, pp. 5363-5376, June, 2023.). The focus of its beamforming design is how to flexibly select sub-6 GHz antenna arrays based on actual channel state information. However, there are many millimeter wave arrays, and the use of an all-digital architecture will bring a lot of hardware overhead. In the document [4], the authors proposed a hybrid beamforming architecture to significantly reduce hardware overhead by comprehensively utilizing analog beamforming and digital beamforming (Document [4]: ​​A. Alkhateeb, O. El Ayach, G. Leus and RW Heath, "Channel estimation and hybrid precoding for millimeter wave cellular systems", IEEE J. Sel. Top. Signal Process., vol. 8, no. 5, pp. 831-846, July 2014.). To this end, the present invention designs a millimeter wave communication perception integrated beamforming based on a hybrid beamforming architecture. Summary of the invention

[0003] The purpose of the present invention is to propose a dual-band reconfigurable antenna array design and beamforming method. The dual-band reconfigurable antenna array connects the RF link to the antenna through a phase shifter network in the millimeter wave band, and dynamically multiplexes the millimeter wave antenna to form a sub-6GHz antenna in the sub-6GHz band by controlling the PIN diode. The beamforming design goal is to maximize the communication and rate of the millimeter wave band while satisfying the constraints of the communication quality and perception quality of the sub-6GHz band. This method makes full use of the characteristics of millimeter wave and sub-6GHz band signals, and can effectively cope with complex and diverse channel environments.

[0004] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0005] The present invention discloses a dual-band reconfigurable antenna array design and beamforming method, the method comprising the following steps:

[0006] S1, a sub-6GHz and millimeter-wave dual-band reconfigurable antenna array is constructed by multiple sub-6GHz antennas. Each sub-6GHz antenna selects f×g millimeter-wave antennas to form a sub-6GHz antenna, where f and g are positive integers; the millimeter-wave antennas are arranged in a uniform planar array with an interval of half a wavelength, and the millimeter-wave antennas are connected using PIN diodes. By controlling the on and off of the PIN diodes, the position of the millimeter-wave antenna combined into the sub-6GHz antenna is selected;

[0007] S2, connects the candidate sub-6GHz antenna to the RF link through a switch network, and controls the on and off of each switch in the switch network to obtain the p Select N out of the candidate sub-6GHz antennas s antennas are used for transmitting and receiving signals in the sub-6 GHz frequency band, wherein each selected antenna is uniquely connected to a radio frequency link in the sub-6 GHz frequency band; and in the millimeter wave frequency band, the millimeter wave radio frequency link is connected to the millimeter wave antenna through a phase shifter network;

[0008] S3, while satisfying the constraints of sub-6GHz band communication quality and perception quality, maximizes the communication and rate of the millimeter wave band, and designs the beamforming of the sub-6GHz band and the millimeter wave band.

[0009] Compared with the prior art, the present invention has the following beneficial effects:

[0010] First, the dual-band reconfigurable antenna array design and beamforming method of the present invention has higher design flexibility than the existing fixed antenna architecture for the millimeter wave and sub-6GHz dual-band reconfigurable antenna array by flexibly utilizing the characteristics of the dual-band array and the reconfigurable array.

[0011] Second, the dual-band reconfigurable antenna array design and beamforming method of the present invention, for the millimeter wave and sub-6GHz dual-band reconfigurable antenna array, can flexibly select millimeter wave arrays to form sub-6GHz arrays, which can more finely adjust the position of the sub-6GHz array than the existing antenna selection method.

[0012] Third, the dual-band reconfigurable antenna array design and beamforming method of the present invention, for the beamforming method, fully exploits the characteristics of the millimeter wave and sub-6GHz dual-bands and utilizes optimization methods to achieve better beamforming performance than existing methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of a millimeter wave and sub-6GHz dual-band reconfigurable antenna array architecture designed in an embodiment of the present invention;

[0014] Figure 2 This is a schematic diagram of selecting a sub-6GHz frequency band antenna designed in an embodiment of the present invention;

[0015] Figure 3 It is a schematic diagram of a millimeter wave and sub-6GHz dual-band reconfigurable antenna RF architecture designed in an embodiment of the present invention;

[0016] Figure 4 It is a schematic diagram of the variation of transmission power in the sub-6 GHz band with the number of millimeter wave arrays in different architectures simulated in an embodiment of the present invention.

[0017] Figure 5 It is a schematic diagram of the variation of transmission power in the sub-6GHz frequency band with the number of users in different architectures simulated by an embodiment of the present invention.

[0018] Figure 6 It is a schematic diagram of the trade-off relationship between millimeter wave frequency band communication and rate and perception beamforming of different RF architectures simulated in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0020] The present invention discloses a dual-band reconfigurable antenna array design and beamforming method, the method comprising the following steps:

[0021] S1, a sub-6GHz and millimeter-wave dual-band reconfigurable antenna array is constructed by multiple millimeter-wave antennas and PIN diodes. The millimeter-wave antennas are arranged in a uniform planar array with an interval of half a wavelength. The millimeter-wave antennas are connected by PIN diodes. By controlling the on and off of the PIN diodes, f×g millimeter-wave antennas are selected from the millimeter-wave antennas to form a sub-6GHz antenna, where f and g are positive integers;

[0022] S2, connects the candidate sub-6GHz antenna to the RF link through a switch network, and controls the on and off of each switch in the switch network to obtain the p Select N out of the candidate sub-6GHz antennas s antennas are used for transmitting and receiving signals in the sub-6 GHz frequency band, wherein each selected antenna is uniquely connected to a radio frequency link in the sub-6 GHz frequency band; and in the millimeter wave frequency band, the millimeter wave radio frequency link is connected to the millimeter wave antenna through a phase shifter network;

[0023] S3, while satisfying the constraints of sub-6GHz band communication quality and perception quality, maximizes the communication and rate of the millimeter wave band, and designs the beamforming of the sub-6GHz band and the millimeter wave band.

[0024] (1) Design of antenna architecture for sub-6 GHz and millimeter wave dual-band reconfigurable antenna array

[0025] like Figure 1 As shown, the antenna architecture of the sub-6GHz and millimeter wave dual-band reconfigurable antenna array designed by the present invention is described as follows:

[0026] The millimeter wave antennas of the array are arranged in a uniform planar array with a spacing of half a wavelength, and the number of antenna array rows is N. row , the number of columns is N col , the total number of antennas is N m =N row ×n col Each sub-6GHz antenna of the array is composed of 2×2 millimeter-wave antennas. The millimeter-wave antennas are connected by PIN diodes. By controlling the on-off of the PIN diodes, the position of the millimeter-wave antennas combined into the sub-6GHz antenna can be flexibly selected. Each sub-6GHz antenna has N p =(N row -1)×(N col -1) combinations.

[0027] (2) Design of RF architecture for sub-6 GHz and millimeter wave dual-band reconfigurable antenna arrays

[0028] like Figure 2 and Figure 3As shown, the radio frequency architecture design of the sub-6GHz and millimeter wave dual-band reconfigurable antenna array of the present invention is as follows:

[0029] There are N sub-6GHz bands s RF chains, N p Candidate sub-6GHz antennas and N s The RF links are connected through a switch network. By controlling the on and off of each switch in the switch network, N p Select N out of the candidate sub-6GHz antennas s Antennas are used for signal transmission and reception in the sub-6GHz band, where each selected antenna is uniquely connected to a RF link in the sub-6GHz band. RF RF links. RF The RF links are connected to N m On an antenna.

[0030] (3) Design of signal transmission model for sub-6 GHz frequency band

[0031] The signal transmission model of the sub-6GHz frequency band used in the present invention is described as follows:

[0032] After the communication symbol passes through the beamformer at the base station, it is sent out through the antenna array. The signal reaches the user after being transmitted in the wireless channel. s The received signal of a sub-6GHz communication user is expressed as

[0033]

[0034] Among them, H s represents the channel matrix between the sub-6GHz antenna array and the sub-6GHz communication user, F s represents the digital beamforming matrix, s s Send signal, n s represents the additive white Gaussian noise vector, (·) H Indicates conjugate transpose.

[0035] (4) Design of signal transmission model in millimeter wave frequency band

[0036] The signal transmission model of the millimeter wave frequency band used in the present invention is described as follows:

[0037] After the communication symbols are digitally precoded, RF link, and analog precoded at the base station, they are sent out through the antenna array. The signal is transmitted in the wireless channel and reaches the user. m The received signal of a millimeter wave communication user is expressed as

[0038]

[0039] Among them, y m K m The received signal of a communication user, H m represents the channel matrix between the millimeter wave antenna array and the millimeter wave communication user, F RF represents the analog beamforming matrix, F BB represents the digital beamforming matrix, s m Indicates sending signal, n m represents the additive white Gaussian noise vector.

[0040] (5) Design of channel transmission model for sub-6 GHz frequency band

[0041] The channel transmission model of the sub-6 GHz frequency band of the present invention can be described as:

[0042] Assume that the total number of nodes from the base station to the kth user is L s,k transmission paths, each of which is represented by azimuth, elevation and channel gain. According to the widely used Saleh-Valenzuela (SV) model, the channel of this sub-6GHz communication system is generally modeled as

[0043]

[0044] in, L s,k , s,k,l ,φ s,k,l and θ s,k,l They represent the number of paths, the channel gain of the lth path, the elevation angle, and the azimuth angle, respectively. where λ m and λ s denote millimeter wave and sub-6 GHz wavelength respectively, then the sub-6 GHz array steering vector β(φ,θ) can be expressed as:

[0045]

[0046] (6) Design of channel transmission model for millimeter wave frequency band

[0047] The channel transmission model of the millimeter wave frequency band of the present invention can be described as:

[0048] Assume that the total number of nodes from the base station to the kth user is L m,k transmission paths, each of which is represented by azimuth, elevation and channel gain. According to the SV model, the channel of this millimeter wave communication system is generally modeled as

[0049]

[0050] in, L m,k , m,k,l ,φ m,k,l and θ m,k,l denote the number of paths, the channel gain of the lth path, the elevation angle, and the departure angle respectively; represents the tensor product; α(·) represents the millimeter wave array steering vector, which is defined as:

[0051] α(N,θ)=[1,e jπθ ,…,e jπ(N-1)θ ].

[0052] (7) Designing beamforming for sub-6 GHz band

[0053] The beamforming in the sub-6 GHz frequency band proposed in the present invention can be described as:

[0054] (7.1) The signal-to-interference-to-noise ratio of the kth sub-6GHz communication user is expressed as:

[0055]

[0056] where f s,k Indicates F s The kth column of ; p = vec(P), P represents the antenna selection matrix, satisfying [P] m,n ∈0,1,m=1,2,…,N row -1,n=1,2,…,c col -1, and p T p=N s ; vec(·) represents the vectorization of the matrix, and diag{·} represents the diagonalization of the vector.

[0057] (7.2) According to the communication requirements, the signal-to-interference-to-noise ratio threshold of the kth communication user is determined as Γ k . Make the communication signal to noise ratio in (7.1) greater than the threshold, that is, S s,k ≥Γ k ,k=1,2,…,K s .

[0058] (7.3) In order to avoid interference between sub-6GHz antennas, a certain distance needs to exist between the selected antennas. Assume that H s 、V s , J H,p and J V,p Respectively represent the minimum horizontal spacing, the minimum vertical spacing, the horizontal index and the vertical index of the pth sub-6GHz antenna, and must meet the following requirements:

[0059] |J H,p -JH,q |≥H s ,|J V,p -J V,q |≥V s ,p,q=1,2,…,N s ,p≠q

[0060] (7.4) The elevation angle and azimuth angle of the tth direction are defined as and θ s,t , the beamforming gain of the base station in this direction is expressed as:

[0061]

[0062] (7.5) According to the perception requirements, the beamforming gain threshold in the tth direction of the sub-6GHz band is Υ s,t . Make the perceptual beamforming gain in (7.4) greater than the threshold, that is, G s,t ≥Υ s,t ,t=1,2,…,T s , where T s The number of sub-6GHz sensing targets.

[0063] (7.6) Determine the base station sub-6GHz frequency band transmission power:

[0064] (7.7) While satisfying the signal-to-interference-to-noise ratio of the communication users in the sub-6GHz band and the sensing direction beamforming gain constraints, the sub-6GHz band transmission power is minimized. According to (7.2), (7.3), (7.5) and (7.6), the sub-6GHz band beamforming problem is established as:

[0065]

[0066] S s,k ≥Γ k

[0067] G s,t ≥Υ s,t

[0068] |J H,p -J H,q |≥H s ,|J V,p -J V,q |≥V s ,p,q=1,2,…,N s ,p≠q

[0069] (7.8) Solve the sub-6 GHz band beamforming problem in (7.7). The specific steps are as follows:

[0070] (7.8.1) Randomly initialize the antenna selection matrix that meets the conditions as the initial value P (0) .

[0071] (7.8.2) Perform digital beamforming matrix F s The specific steps for optimization are as follows:

[0072] ① After the antenna selection matrix P is given, by utilizing the phase rotation property of complex numbers, the non-convex communication user signal-to-interference-noise ratio constraint in (7.2) can be rewritten as

[0073]

[0074] to convert it into a convex constraint.

[0075] ② Using the property that a quadratic convex function is always not less than its first-order Taylor expansion, the non-convex sensing direction beamforming gain constraint in (7.2) is rewritten as

[0076]

[0077] To transform it into a convex constraint, where t = vec{F s};

[0078] ③ Through steps ① and ②, the sub-6GHz band beamforming problem in (7.7) is transformed into a convex problem, which can be solved by the existing convex optimization toolbox to obtain the design result

[0079] (7.8.3) Optimize the antenna selection matrix P. The specific steps are as follows:

[0080] ① Antenna selection matrix P in N s The non-zero elements correspond to the selected N s sub-6GHz antennas. Define the horizontal index and vertical index of the selected antenna as x and u respectively, and define is the mapping relationship between P and x, y, expressed as:

[0081]

[0082] ②In the bth iteration, the updated sub-6GHz antenna index is:

[0083]

[0084] The horizontal index and vertical index after the last iteration are expressed as and Due to the existence of antenna spacing constraints, the set of horizontal indexes and vertical indexes of feasible antennas in the b-th iteration process is expressed as:

[0085]

[0086] This collection has elements, respectively define the set The horizontal index and vertical index of the sth element in are and Then N s Index of root antenna and It can be expressed as:

[0087]

[0088] The corresponding antenna selection matrix It can be expressed as:

[0089]

[0090] Based on this, the corresponding base station sub-6GHz frequency band transmission power can be calculated as:

[0091] ③Traversal steps ②Set All elements in , and return the element that minimizes the base station sub-6GHz frequency band transmission power among all elements, that is,

[0092]

[0093] The horizontal index and vertical index of the antenna selected after the i-th iteration can be expressed as The corresponding antenna selection matrix is ​​expressed as The minimum sub-6GHz band transmit power is expressed as

[0094] (7.8.4) Iterate (7.8.2) and (7.8.3) until one of the following stopping conditions is met:

[0095] ① Reach the maximum number of iterations B F ;

[0096] ②The minimum sub-6GHz band transmit power after the bth iteration is less than the predefined power threshold

[0097] ③The result after the b-th iteration is exactly the same as the result after the b-1-th iteration.

[0098] The final designed sub-6GHz band antenna selection matrix is ​​expressed as The beamforming matrix is ​​expressed as The transmit power is expressed as

[0099] (8) Designing beamforming for millimeter wave bands

[0100] The beamforming method for the millimeter wave frequency band proposed by the present invention can be described as follows:

[0101] (8.1) The signal-to-interference-to-noise ratio of the kth millimeter-wave communication user is expressed as:

[0102]

[0103] in Represents the noise power in the millimeter wave frequency band.

[0104] (8.2) K m The sum rate of the communicating users is expressed as:

[0105]

[0106] (8.3) The elevation angle and azimuth angle of the tth direction are defined as and θ m,t , then the beamforming gain of the base station in this direction is:

[0107]

[0108] (8.4) For the millimeter wave frequency band communication and perception integrated system, the beamforming gain of the base station in the tth direction needs to be greater than the predetermined threshold Υ m,t , that is, G m,t ≥Υ m,t ,t=1,2,…,T m .

[0109] ((8.5) While satisfying the constraints of the beamforming gain and transmit power in the millimeter wave band, in order to provide high-speed communication services, it is necessary to maximize the communication and rate R m The millimeter wave beamforming optimization problem is formulated as

[0110]

[0111] sG m,t ≥Υ m,t

[0112]

[0113] |[F RF ] m,i |=1

[0114] in, is the maximum transmission power of millimeter wave, |[F RF ] m,i Denotes the matrix F RF The i-th element in the m-th row of .

[0115] (8.6) To solve the millimeter wave beamforming problem, the specific steps are as follows:

[0116] (8.6.1) Simplify the millimeter wave beamforming problem. Introduce auxiliary variables F m =F RF F ii , rewrite the perceptual directional beamforming gain constraint as:

[0117]

[0118] The transmit power constraint is rewritten as:

[0119]

[0120] The communication sum rate is rewritten as:

[0121]

[0122] where f m,k Indicates F m Using the equivalence between sum rate maximization and weighted mean square error minimization, the maximum communication sum rate is written as:

[0123]

[0124] where w k represents the weighting coefficient; u k represents the weight of the kth user; e k Defined as:

[0125]

[0126] By using the penalty function method, the auxiliary variable constraint F m =F RF F BB Introduce the objective function:

[0127]

[0128] Where ρ represents the penalty parameter; D represents the dual variable. Then the millimeter wave beamforming optimization problem can be rewritten as

[0129]

[0130] |[F RF ] m,i |=1

[0131] (8.6.2) Randomly initialize u that meets the conditions k 、w k 、F m 、F RF 、F BB , ρ and D, assuming that the corresponding variables have the value of and

[0132] (8.6.3) Update u in the dth iteration k 、w k 、F m 、F RF 、F BB , ρ and D, the specific steps are as follows:

[0133] ① will u k The optimization problem is transformed into:

[0134]

[0135] By making it k The partial derivative is zero, and the optimal solution can be obtained:

[0136]

[0137] in express The kth column of .

[0138] ②W k The optimization problem is transformed into:

[0139]

[0140] By making it w k The partial derivative is zero, and the optimal solution can be obtained:

[0141]

[0142] ③F m The optimization problem is transformed into:

[0143]

[0144] r=vec{F m}; is the value of the last iteration; The problem is solved by using the existing convex optimization toolbox, and the design result is obtained.

[0145] ④F RF The optimization problem can be transformed into:

[0146]

[0147] st|[F RF ] m,i |=1

[0148] This problem can be solved by Riemann manifold optimization to obtain F RF Solution

[0149] ⑤F BB The optimization problem can be transformed into:

[0150]

[0151] This problem is a least squares problem. BB The partial derivative is zero, and the optimal solution can be obtained:

[0152]

[0153] ⑥ Update the penalty parameter ρ to obtain better convergence performance. Specifically, the update process of ρ is as follows:

[0154]

[0155] Where ξ represents a predefined threshold; η represents a scaling factor.

[0156] ⑦The update process of D is as follows:

[0157]

[0158] (8.6.4) Iterate (8.6.3) until one of the following stopping conditions is met:

[0159] ① Reach the maximum number of iterations D M ;

[0160] ② The difference between the result after the dth iteration and the result after the d-1th iteration is less than a predefined threshold, that is

[0161] The present invention is further described below in conjunction with simulation conditions and results:

[0162] The sub-6GHz frequency of the dual-band communication and perception integrated system is f s =5GHz, the millimeter wave frequency is f m =30GHz. Set the minimum antenna spacing to H s =V s =6. For millimeter wave channels, the number of channel paths is set to L m,k=3, and the channel gain of each path obeys For sub-6GHz channels, set L s,k =5, and the channel gain of each path obeys The noise power of the system's dual-bands is set to

[0163] Figure 4 The figure is a schematic diagram of the variation of the transmission power of the sub-6GHz band with the number of millimeter wave array elements in different architectures simulated by an embodiment of the present invention. The number of antennas in each row and column of the millimeter wave antenna array is set to be the same as the horizontal axis. The number of sub-6GHz antennas is set to 4. The minimum beamforming gain and signal-to-interference-noise ratio threshold of the sub-6GHz band are both set to 10. It can be seen from the figure that the transmission power of the proposed dual-band reconfigurable antenna array decreases with the increase of the number of millimeter wave array elements, and is significantly better than the fixed antenna architecture in reference [1] and the antenna selection architecture in reference [2], which proves the superiority of the proposed scheme.

[0164] Figure 5 This is a schematic diagram of the variation of sub-6GHz frequency band transmission power with the number of users in different architectures simulated by the embodiment of the present invention. The number of millimeter wave arrays is set to N row =N col =14. The number of sub-6GHz antennas is set to 5. The minimum beamforming gain and signal-to-interference-noise ratio thresholds of the sub-6GHz band are both set to 10. As can be seen from the figure, the transmit power of the proposed dual-band reconfigurable antenna array increases with the increase in the number of users, and is significantly better than the fixed antenna architecture in reference [1] and the antenna selection architecture in reference [2], which further proves the superiority of the proposed scheme.

[0165] Figure 6 This is a schematic diagram of the trade-off relationship between the communication rate and sensing beamforming of different architectures in the millimeter wave frequency band simulated by the embodiment of the present invention. The number of millimeter wave arrays is set to N row =N col = 14. Number of millimeter wave users K m =4, number of radio frequency links N RF =4. The azimuth and elevation angles of the sensing area are both in the range of [0.5, 0.7]. The minimum sensing beamforming gain is set to Υ m,t =11. The total base station transmit power is set to 7. As can be seen from the figure, with the increase of the perception beamforming gain, the communication rate gradually decreases, indicating that the proposed scheme can effectively achieve a compromise between communication and perception performance. The performance of the communication perception integrated beamforming based on the hybrid beamforming architecture designed by the present invention can approach the beamforming performance based on the all-digital architecture of the reference [3], which verifies the effectiveness of the proposed beamforming method.

[0166] The reconfigurable antenna array designed by the present invention, on the one hand, forms a sub-6GHz band antenna by reusing the millimeter wave band antenna, saving the space occupied by the antenna array; on the other hand, the millimeter wave array is connected through PIN diodes, and the millimeter wave antenna forming the sub-6GHz band antenna is flexibly selected by controlling the on-off of the PIN diode, thereby increasing the degree of freedom of sub-6GHz design. The beamforming design of the array maximizes the communication and rate of the millimeter wave band under the constraints of meeting the communication quality and perception quality of the sub-6GHz band, and can make full use of the signal characteristics of the sub-6GHz band and the millimeter wave band, and effectively deal with the actual complex and diverse channels.

[0167] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0168] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A dual-band reconfigurable antenna array design and beamforming method, characterized in that: The method comprises the following steps: S1, a sub-6GHz and millimeter-wave dual-band reconfigurable antenna array is constructed by multiple millimeter-wave antennas and PIN diodes. The millimeter-wave antennas are arranged in a uniform planar array with an interval of half a wavelength. The millimeter-wave antennas are connected by PIN diodes. By controlling the on and off of the PIN diodes, f×g millimeter-wave antennas are selected from the millimeter-wave antennas to form a sub-6GHz antenna, where f and g are positive integers; S2, connects the candidate sub-6GHz antenna to the RF link through a switch network, and controls the on and off of each switch in the switch network to obtain the p Select N out of the candidate sub-6GHz antennas s antennas are used for transmitting and receiving signals in the sub-6 GHz frequency band, wherein each selected antenna is uniquely connected to a radio frequency link in the sub-6 GHz frequency band; and the millimeter wave antenna is connected to the millimeter wave radio frequency link through a phase shifter network in the millimeter wave frequency band; S3, while satisfying the constraints of sub-6GHz band communication quality and perception quality, maximizes the communication and rate of the millimeter wave band, and designs the beamforming of the sub-6GHz band and the millimeter wave band.

2. The dual-band reconfigurable antenna array design and beamforming method according to claim 1, characterized in that: Step S3 further comprises: S31, based on the signal transmission process in which the communication symbol passes through the beamformer at the base station and is sent out through the antenna array, and the signal is transmitted in the wireless channel and reaches the user, a signal transmission model for the sub-6GHz frequency band is designed; S32, based on the signal transmission process in which the communication symbol is sent out through the antenna array after being digitally precoded, radio frequency link, and analog precoded at the base station, and the signal is transmitted in the wireless channel and then reaches the user, a signal transmission model of the millimeter wave frequency band is designed; S33, based on the Saleh-Valenzuela model, designs a channel transmission model for the sub-6GHz frequency band; S34, based on the Saleh-Valenzuela model, designs a channel transmission model for the millimeter wave frequency band; S35, while satisfying the signal-to-interference-to-noise ratio of communication users in the sub-6GHz band and the sensing direction beamforming gain constraints, minimize the sub-6GHz band transmit power, establish and solve the sub-6GHz band beamforming problem, and design the sub-6GHz band beamforming; S36, while satisfying the millimeter wave band sensing direction beamforming gain and transmission power constraints, maximizes communication and rate, establishes and solves the millimeter wave beamforming optimization problem, and designs the beamforming in the millimeter wave band.

3. The dual-band reconfigurable antenna array design and beamforming method according to claim 2, characterized in that: In step S31, the signal transmission model of the sub-6GHz frequency band is: Among them, y s K s The received signal of a sub-6GHz communication user, H s represents the channel matrix between the sub-6GHz antenna array and the sub-6GHz communication user, F s represents the digital beamforming matrix, s s Send signal, n s represents the sub-6GHz additive white Gaussian noise vector, (·) H Indicates conjugate transpose.

4. The dual-band reconfigurable antenna array design and beamforming method according to claim 2, characterized in that: In step S32, the signal transmission model in the millimeter wave frequency band is: Among them, y m K m The received signal of a communication user, H m represents the channel matrix between the millimeter wave antenna array and the millimeter wave communication user, F RF represents the analog beamforming matrix, F BB represents the digital beamforming matrix, s m Indicates sending signal, n m represents the millimeter-wave additive white Gaussian noise vector.

5. The dual-band reconfigurable antenna array design and beamforming method according to claim 2, characterized in that: In step S33, the channel transmission model of the sub-6 GHz frequency band is: in, L s,k , s,k,l ,φ s,k,l and θ s,k,l Respectively represent the number of paths, the channel gain of the lth path, the elevation angle and the departure angle; define where λ m and λ s represent millimeter wave and sub-6 GHz wavelength respectively, and the sub-6 GHz array steering vector β(φ,θ) is expressed as:

6. The dual-band reconfigurable antenna array design and beamforming method according to claim 2, characterized in that: In step S34, the channel transmission model of the millimeter wave frequency band is: Among them, N row and N col denote the number of rows and columns of the millimeter wave antenna array, respectively. L m,k , m,k,l ,φ m,k,l and θ m,k,l denote the number of paths, the channel gain of the lth path, the elevation angle, and the departure angle respectively; represents the tensor product; α(·) represents the millimeter wave array steering vector, which is defined as: α(N,θ)=|1,e jπθ ,…,e jπ(N-1)θ ] T 。 7. The dual-band reconfigurable antenna array design and beamforming method according to claim 2, characterized in that: In step S35, while satisfying the signal-to-interference-noise ratio of the communication user in the sub-6 GHz band and the sensing direction beamforming gain constraints, the sub-6 GHz band transmit power is minimized, and the sub-6 GHz band beamforming problem is established as: In the formula, S s,k represents the signal-to-interference-to-noise ratio of the kth sub-6GHz communication user, Γ k H represents the signal-to-interference-noise ratio threshold of the kth communication user; s 、V s , J H,p and J V,p Respectively represent the minimum horizontal spacing, the minimum vertical spacing, the horizontal index and vertical index of the pth sub-6GHz antenna; G s,t represents the beamforming gain of the base station in the tth direction, Υ s,t Indicates the beamforming gain threshold in the tth direction in the sub-6 GHz band.

8. The dual-band reconfigurable antenna array design and beamforming method according to claim 7, characterized in that: In step S35, the process of solving the sub-6 GHz band beamforming problem includes: S351, randomly initialize the antenna selection matrix that meets the conditions as the initial value P (0) ; S352, perform digital beamforming matrix F s The specific steps for optimization are as follows: S3521, given the antenna selection matrix P, by utilizing the phase rotation property of complex numbers, the non-convex communication user signal-to-interference-noise ratio constraint is rewritten as to transform it into a convex constraint; S3522, using the property that a quadratic convex function is always not less than its first-order Taylor expansion, the non-convex sensing direction beamforming gain constraint is rewritten as to transform it into a convex constraint, where S3523, transform the sub-6GHz band beamforming problem into a convex problem and solve it using the existing convex optimization toolbox to obtain the design result S353, optimizing the antenna selection matrix P, the specific steps are as follows: S3531, antenna selection matrix P in N s The non-zero elements correspond to the selected N s sub-6GHz antennas, define the horizontal index and vertical index of the selected antenna as x and y respectively, and define is the mapping relationship between P and x, y, expressed as: [x] p represents the pth element of x; S3532, in the bth iteration, the updated sub-6GHz antenna index is: The horizontal index and vertical index after the last iteration are expressed as and Due to the existence of antenna spacing constraints, the set of horizontal indexes and vertical indexes of feasible antennas in the b-th iteration process is expressed as: This collection has elements, respectively define the set The horizontal index and vertical index of the sth element in are and Then N s Index of root antenna and It is expressed as: The corresponding antenna selection matrix It is expressed as: Calculate the corresponding base station sub-6GHz frequency band transmission power: S3533, traverse the set of step S3532 All elements in , and return the element that minimizes the base station's sub-6GHz frequency band transmission power among all elements: The horizontal index and vertical index of the antenna selected after the bth iteration are expressed as The corresponding antenna selection matrix is ​​expressed as The minimum sub-6GHz band transmit power is expressed as S354, iterate step S352 and step S353 until one of the following stop conditions is met: ① Reach the maximum number of iterations B F ; ②The minimum sub-6GHz band transmit power after the bth iteration is less than the predefined power threshold ③The result after the b-th iteration is exactly the same as the result after the b-1-th iteration; The final designed sub-6GHz band antenna selection matrix is ​​expressed as The beamforming matrix is ​​expressed as The transmit power is expressed as 9. The dual-band reconfigurable antenna array design and beamforming method according to claim 2, characterized in that: In step S36, the communication sum rate R is maximized while satisfying the millimeter wave band sensing direction beamforming gain and transmission power constraints. m , the millimeter wave beamforming optimization problem is formulated as in, is the maximum transmission power of millimeter wave; R m K m The sum rate of the communicating users, G m,t represents the beamforming gain of the base station in the tth direction, Υ m,t represents the beamforming gain threshold of the base station in the tth direction, F RF represents the analog beamforming matrix, F BB represents the digital beamforming matrix, |[F RF ] m,i Denotes the matrix F RF The i-th element in the m-th row of .

10. The dual-band reconfigurable antenna array design and beamforming method according to claim 9, characterized in that: The solution process of the millimeter wave beamforming optimization problem includes the following steps: Step S361, introduce auxiliary variable F m =F RF F BB , rewrite the perceptual directional beamforming gain constraint as: The transmit power constraint is rewritten as: The communication sum rate is rewritten as: where f m,k Indicates F m The kth column of ; using the equivalence between sum rate maximization and weighted mean square error minimization, the maximum communication sum rate is written as: where w k represents the weighting coefficient; u k represents the weight of the kth user; e k Defined as: By using the penalty function method, the auxiliary variable constraint F m =F RF F BB Introduce the objective function: Where ρ represents the penalty parameter; D represents the dual variable; then the millimeter wave beamforming optimization problem is rewritten as: S362, randomly initialize u that meets the conditions k 、w k 、F m 、F RF 、F BB , ρ and D, assuming that the corresponding variables have the value of and S363, update u in the dth iteration k 、w k 、F m 、F RF 、F BB , ρ and D, the specific steps are as follows: S3631, u k The optimization problem is transformed into: By making it k The partial derivative is zero, and the optimal solution is obtained: in express The kth column of S3632, w k The optimization problem is transformed into: By making it w k The partial derivative is zero, and the optimal solution is obtained: S3633, F m The optimization problem is transformed into: r=vec{F m }; is the value of the last iteration; The problem is solved by using the existing convex optimization toolbox, and the design result is obtained. S3634, F RF The optimization problem is transformed into: Through Riemann manifold optimization, we can get F iF Solution S3635, F BB The optimization problem is transformed into: By making it BB The partial derivative is zero, and the optimal solution is obtained: S3636, the penalty parameter ρ is updated; the updating process of ρ is as follows: Where ξ represents a predefined threshold; η represents a scaling factor; S3637, the update process of D is as follows: S364, iterate step S363 until one of the following stop conditions is met: ① Reach the maximum number of iterations D M ; ② The difference between the result after the dth iteration and the result after the d-1th iteration is less than a predefined threshold ∈, that is,

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