Method for improving bandwidth and efficiency of 1bit circular polarization transmission array antenna

Abstract

The invention discloses a method for improving bandwidth and efficiency of a 1bit circular polarization transmission array antenna, which comprises the following steps of: rotating a radiation patch of a 1bit circular polarization phase coding transmission unit by 90 degrees to form a first-class unit which is orthogonally placed with a radiation layer of an original transmission unit; the original transmission units and the orthogonal units are arranged in a crossed and staggered manner to form 2 * 2 structural blocks; exchanging the positions of the original units and the orthogonal units in the 2 * 2 structural blocks to form 2 * 2 replacement structural blocks; the original structural blocks and the replacement structural blocks are arranged in a crossed and staggered mode to form 4 * 4 unit supercells; the radiation layer distribution pattern of the 4 * 4 unit supercell is approximately that four 2 * 2 structural blocks rotate in sequence at angles of 0 degree, 90 degrees, 180 degrees and 270 degrees; and constructing a 1bit circular polarization transmission array antenna by 4 * 4 unit supercells. According to the invention, the strong relevance of main polarization and cross polarization phase regulation in a uniform array is relieved, and the axial ratio bandwidth of a circular polarization beam and the aperture efficiency of an array antenna are improved.

Description

Technical Field

[0001] The present invention relates to the field of optical or electromagnetic radiation control, microwave and antenna technology, and specifically to a method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna, which can effectively improve the radiation performance such as the axial ratio bandwidth and aperture efficiency of a circularly polarized radiation array antenna with a 1-bit phase coding requirement. Background Art

[0002] As an important component of radar detection and wireless communication systems, circularly polarized antennas have received extensive attention in various application scenarios due to their advantages in anti-interference and multipath effect reduction. However, with the development of the times, flexible and fast beam scanning capabilities have posed great challenges to existing antenna forms; traditional mechanical scanning and electronic scanning methods achieved by loading phase shifters have been difficult to meet the requirements of modern detection and communication systems due to their inherent defects.

[0003] In the past two decades, some scholars have proposed to use the digital coding phase control capability of metasurfaces to achieve arbitrary controllable electromagnetic wave manipulation. Compared with the continuous phase control of phase shifters, it is simpler in form and more streamlined in implementation. In addition, the low cost and easy integration of metasurfaces also have advantages in antenna system implementation. However, for the continuous phase that can be achieved by phase shifters, array antennas with discrete coding phases are only approximate to the performance of continuous phase control antennas. The more coding states there are, the closer they are to continuous phase control, and the more complicated their implementation is. The fewer coding states there are, the simpler the implementation will be, but it also means a greater approximation error. The minimum 1 bit (i.e., only two states of 0° and 180°) or 2 bits (i.e., four states of 0°, 90°, 180°, and 270°) coding number is the scheme adopted by most existing studies. However, although the 2-bit discrete scheme has a more approximate phase distribution and radiation performance, it requires more device integration and more complex network requirements. Therefore, the 1-bit phase discrete scheme has been favored by most researchers.

[0004] For simple linear polarization wave control, due to the natural high isolation characteristics between orthogonal polarizations, uniform unit arrangement can achieve better sidelobe and cross-polarization performance using optimization algorithms. However, for circularly polarized waves, its unique unit structure and phase control mechanism determine that there is a strong correlation between the main polarization and the cross polarization. If the distribution of discrete phases is unreasonable, the main polarization and the cross polarization will be superimposed in an undesirable direction, thereby deteriorating the radiation performance of the antenna; therefore, the 1-bit phase discrete scheme is difficult to apply in circularly polarized array antennas, especially for transmission array antennas; the existing 1-bit phase discrete scheme is mostly limited to circularly polarized reflective array antennas, but it has significant feed source shielding and high profile problems; in order to solve the phase discrete problem in circularly polarized transmission array antennas, researchers have successively proposed solutions such as multi-bit structure and multi-layer phase control functional layer, but this undoubtedly increases the design complexity of the unit structure and the complexity of phase control, and it is difficult to meet the application requirements of actual circularly polarized antennas. Therefore, there are still many technical challenges in realizing a high-performance 1-bit circularly polarized transmission array antenna with a single phase modulation functional layer.

[0005] The invention with patent publication number CN117013270A discloses a low RCS circularly polarized antenna array with reconfigurable scattered beam, which includes a feeding network, a dielectric plate, and a radiating patch. By definition, it is a radiating metasurface that does not require a receiving layer patch and a spatial feed source; on the other hand, its unit radiating patches are placed orthogonally, with the aim of canceling the scattering of the co-polarized and cross-polarized components of the linearly polarized incoming waves irradiated on the radiating patches, and realizing reconfigurable control of the scattered beam by changing the unit state; in order to cope with the influence of the linearly polarized scattered beam on the circularly polarized radiation beam when controlling the linearly polarized scattered beam, a complex phase shifter network is required to offset this influence; from the radiation perspective, its structure does not realize a controllable circularly polarized radiation beam, and an additional phase shifter network is required to correct the phase, so that the radiated circularly polarized beam always points to 0°; combined with the unit layout and the phase correction phase shifter as a whole, the circularly polarized waves radiated by each unit in the orthogonal unit pattern have the same phase, and the suppression of the cross-polarized components of the radiated circularly polarized waves is neither considered nor realized.

[0006] The invention with patent publication number CN116207511A discloses a design method and antenna for a fully polarized high-gain antenna. The antenna is defined as a type of reflector array, which controls the state of the unit diode to control the reflected beam of the electromagnetic wave irradiated on the unit. From the functional mechanism, the switching of the two states of the unit is equivalent to a 90° physical rotation, and its purpose is to introduce a 180° 1-bit reflection phase difference between the two states, that is, the reflection phase of state 0 is 0°, and the reflection phase of state 1 is 180° after rotating 90°; the 1-bit phase control of the unit is achieved through rotation. The invention cannot solve the technical problem that the cross-polarization component interferes with the main polarization beam in the same direction.

[0007] The invention with patent publication number CN112949032B discloses a design method for a fully polarized reconfigurable planar reflectarray antenna technology. First of all, the antenna is a type of reflectarray by definition, which controls the state of the unit diode to control the electromagnetic wave irradiated on the unit to achieve the control of the reflected beam; secondly, since its antenna unit mainly independently controls two orthogonal linearly polarized electromagnetic waves in a 1-bit manner, it is impossible to directly generate or control circularly polarized electromagnetic waves; in order to achieve the control of circularly polarized waves, it is necessary to set different reference phases for the two linearly polarized components, and the reference phase cannot be controlled by electrical signals; in order to improve the quality of the circularly polarized beam, it rotates several units in sequence, but it should be noted that their relative positions are fixed, and the relative rotation angle cannot be changed by changing the state of the PIN diode; although this scheme achieves the suppression of cross-polarization to a certain extent, when performing circularly polarized beam scanning, the reference phase needs to be continuously optimized, which will inevitably affect the gain and efficiency of the circularly polarized beam. Summary of the invention

[0008] The purpose of the present invention is to provide a method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna. Without changing the existing structure, the technical solution discussed is arranged in a specific pattern with two orthogonally placed radiation layer patch units, which eliminates the strong correlation between the main polarization and cross-polarization phase control in the uniform array, and not only achieves the cross-polarization cancellation effect in the broadband range, but also significantly improves the axial ratio bandwidth of the circularly polarized beam, so that the energy is further superimposed in a desired manner, effectively increasing the aperture efficiency of the array antenna; the scheme discussed can be widely used in radiating circularly polarized antennas with 1-bit electrically controlled phase adjustment capability, not only for circularly polarized transmission array antennas with receiving and radiating patches, but also for all array antennas generally having a single-layer radiation layer circularly polarized patch, such as phased arrays and radiating metasurfaces.

[0009] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0010] The present invention discloses a method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna, the method comprising the following steps:

[0011] Construct a 1-bit circularly polarized phase-coded transmission unit; wherein the RF radio frequency current signal received by the inner circle of the radiation patch flows to the outer circle of the radiation patch according to the selected PIN diode and generates circularly polarized radiation, and the radiation patch has two coding phase states of 0° and 180°;

[0012] Without changing the rest of the structure of the 1-bit circular polarization phase-coded transmission unit, the radiation patch of the 1-bit circular polarization phase-coded transmission unit is rotated 90° to form a type of unit placed orthogonally to the radiation layer of the original transmission unit; the original unit and the orthogonal unit are placed crosswise and staggered to form a unit structure block in a 2×2 array;

[0013] The positions of the original unit and the orthogonal unit in the 2×2 unit structure block are exchanged to form another type of 2×2 replacement structure block; the original structure block and the replacement structure block are further placed crosswise and staggered to form a 4×4 unit supercell; the radiation layer distribution pattern of the 4×4 unit supercell is approximately the rotation of the four 2×2 structure blocks in the order of 0°, 90°, 180° and 270°; the rest of the unit structure is arranged in the same way;

[0014] A 1-bit circularly polarized transmission array antenna is constructed with 4×4 unit supercell as the basic component. After receiving the linearly polarized electromagnetic wave, each unit in the array uses the 4×4 unit supercell as the basic block to re-radiate the circularly polarized electromagnetic wave. The main polarization components are superimposed on each other in the basic block, and the cross-polarization components are offset on the basic block. Since the orthogonal placement of the radiating patches in the 4×4 unit supercell is equivalent to a dispersion-free rotation operation, cross-polarization suppression and main polarization superposition can be achieved in a broadband, thereby realizing a broadband and efficient radiation beam.

[0015] Furthermore, the 1-bit circular polarization phase-encoded transmission unit includes a linear polarization receiving patch, a metal ground plane, a radiation patch with 1-bit phase regulation capability, and two layers of dielectric substrates;

[0016] The linear polarization wave receiving patch and the circular polarization wave radiating patch are respectively located on the two side surfaces of the transmission unit and are respectively attached to two layers of dielectric substrates;

[0017] The linear polarization receiving patch is used to receive linear polarization electromagnetic waves that conform to the polarization direction, convert them into RF radio frequency current signals and conduct them to the inner circle of the radiating patch; the radiating patch transmits the RF radio frequency current signal to the outer circle of the radiating patch according to the selected PIN diode and generates circular polarization radiation;

[0018] The metal ground plane is located between the two layers of dielectric substrates and is used to isolate the linear polarization wave receiving patch and the circular polarization wave radiating patch; a hole is pre-punched in the center of the metal ground plane to allow the central metal conduction via to pass through;

[0019] The radiation patch integrates two PIN diodes, only one of which is turned on at the same time. According to the conduction state of the PIN diode, the radiation patch includes two working states, and the phase difference of the radiation circularly polarized beams in the two working states is 180°.

[0020] Furthermore, the dielectric substrate and the metal ground plane are both square with a side length of 15 mm, and the electrical size thereof is half the working wavelength. The working frequency of the transmission unit is selected in the X-band range of 8 GHz-12 GHz, and the central working frequency is 10 GHz.

[0021] Furthermore, the dielectric substrate is made of F4B material with a dielectric constant of 3.5 and a loss tangent of 0.0015, and a thickness of 1.524 mm.

[0022] Furthermore, the linearly polarized receiving patch is a rectangular metal patch placed in a horizontal direction, with a central metal conductive via in the middle and a U-shaped groove around the central metal conductive via; electromagnetic waves that conform to the structural polarization direction are received by the linearly polarized receiving patch and converted into RF radio frequency current signals, and are merged into the central metal conductive via through the middle metal microstrip line, and then pass through the circular groove in the middle of the metal ground plane to reach the radiation patch.

[0023] Furthermore, the radiation patch is a centrally placed square metal patch with two cut corners in the main diagonal direction. A mouth-shaped groove is provided in the middle part of the square patch. The inner circle patch is connected to the outer circle patch through two PIN diodes. The RF radio frequency current signal flowing out from the central metal conduction via reaches the inner circle patch, and then flows to the outer circle patch through the turned-on PIN diode, generating left-handed circularly polarized electromagnetic wave radiation.

[0024] Furthermore, the 1-bit circularly polarized transmission array antenna continuously rotates the array radiation direction. The continuous compensation phase of the directional beam in the direction and the compensation phase of the radiation patch distribution rotated to the corresponding angle are:

[0025]

[0026] Among them, λ is the wavelength corresponding to the antenna operating frequency, (x, y) is the horizontal and vertical coordinates of the center of each transmission unit in the array, F is the height of the phase center of the normal-placed vertical feed antenna from the plane receiving layer of the transmission array, and φ0 is the reference phase.

[0027] Furthermore, the phase discretization criterion of the 1-bit circularly polarized transmission array antenna is:

[0028]

[0029] In the formula, φ cont is the calculated continuous compensation phase, 'V' and 'H' represent the vertical unit and the horizontal unit respectively; State I is the 0° and 270° phases obtained by the two types of units being discrete, and State II is the 180° and 90° phases obtained by the two types of units being discrete.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] First, the method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna of the present invention proposes two array arrangement patterns suitable for a single-layer 1-bit coded phase circularly polarized metasurface, which not only eliminates the 1-bit phase correlation between the main polarization and the cross-polarization in the transmission unit of linear polarization reception and circularly polarized radiation, but also simplifies the structure of the existing 1-bit circularly polarized radiation unit, and realizes effective circularly polarized wave phase control with a single functional layer; one of the schemes using a rotation strategy also cancels out undesirable cross-polarization components in the structural block subarray, further preventing the superposition of cross-polarization in the far field. Since this physical rotation is dispersion-free, the radiation or transmission circularly polarized array arranged using this scheme has a good cross-polarization level and axial ratio bandwidth in a wide band.

[0032] Second, the method for improving the bandwidth and efficiency of 1-bit circularly polarized transmission array antennas of the present invention is applicable to all array antennas that require single-layer circularly polarized phase encoding, such as circularly polarized radiating patches with 1-bit phase control capability in the transmission unit, single-layer radiating circularly polarized phased arrays, and circularly polarized radiating metasurfaces that use a feeding network for unified feeding. The scheme has important inspirational significance for 1-bit real-time reconfigurable circularly polarized array antennas with integrated active devices, greatly promoting the practical application of circularly polarized electronically scanned array antennas and expanding their application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of a transmissive metasurface unit structure modified for conceptual illustration, with linear polarization reception and 1-bit circular polarization radiation;

[0034] Figure 2 for Figure 1 Bottom view of the unit, specifically showing the structure of the linear polarization receiving patch; and the middle layer ground plane;

[0035] Figure 3 for Figure 1The top view of the unit is a schematic diagram of the structure of a circularly polarized radiating patch with two PIN diodes integrated thereon; the two diodes work in the 'ON / OFF' state, marked as state I; the right figure is the equivalent structure of the passive patch in state I;

[0036] Figure 4 The figure below is a circularly polarized radiating patch working in state II (i.e., the two diodes work in the 'OFF / ON' state); the figure on the right is an equivalent passive patch structure in state II;.

[0037] Figure 5 It is the transmission amplitude response of the linear polarization to circular polarization of the 1-bit unit working in state I.

[0038] Figure 6 Transmission phase curves of the main polarization and cross-polarization components and the corresponding phase differences when the 1-bit unit operates in two states.

[0039] Figure 7 Schematic diagram of two unit radiation patches placed orthogonally according to the orientation of the PIB diode.

[0040] Figure 8 Schematic diagram of a 2×2 structural block composed of two types of units and the corresponding unit sub-array structure.

[0041] Fig. 9 Schematic diagram of a 4×4 structural block composed of two types of units and the corresponding unit supercell structure.

[0042] Fig.10 The schematic diagram is a structural diagram of a 16×16 array antenna formed by using the unit, including a linearly polarized feed horn and linearly polarized receiving patches arranged in the same manner at the bottom layer.

[0043] Fig.11 The calculated direction The continuous compensation phase required for the outgoing beam and the corresponding continuous phase modulation array radiation layer.

[0044] Fig.12 The figure shows the radiation layer of an array with vertical units placed in the same manner, and the 1-bit phase distribution diagram obtained by discretizing the continuous phase.

[0045] Fig.13 A schematic diagram of the array radiation layer composed of two types of units placed in a 2×2 structural block, and a 1-bit / quasi-2-bit phase distribution diagram obtained by discretizing the continuous phase.

[0046] Fig.14A schematic diagram of the array radiation layer composed of two types of units placed in a 4×4 structural block, and a 1-bit / quasi-2-bit phase distribution diagram obtained by discretizing the continuous phase.

[0047] Fig.15 The main polarization and cross-polarization far-field radiation patterns of four array antennas: continuous phase modulation array, UEA uniform array, 2×2 structure block OEA array and 4×4 supercell OEAR array.

[0048] Fig.16 These are the curves showing the main polarization and cross-polarization gains of four array antennas, namely, continuous phase modulation array, UEA uniform array, 2×2 structure block OEA array and 4×4 super cell OEAR array, varying with frequency in the main beam direction.

[0049] Fig.17 These are the curves showing how the axial ratio of four array antennas, namely, continuous phase modulation array, UEA uniform array, 2×2 structure block OEA array and 4×4 super cell OEAR array, varies with frequency in the main beam direction.

[0050] Fig.18 These are the curves showing how the aperture efficiency corresponding to the main polarization gain in the main beam direction of four array antennas, namely, continuous phase modulation array, UEA uniform array, 2×2 structure block OEA array and 4×4 super cell OEAR array, varies with frequency.

[0051] The accompanying drawings are denoted as follows:

[0052] 1. Bottom layer linear polarization receiving patch; 2. Top layer circular polarization radiating patch; 3. Two integrated PIN diodes; 4. Central RF signal conduction metal via; 5. Middle layer isolation metal ground plane; 6. Upper layer dielectric substrate; 7. Lower layer dielectric substrate. DETAILED DESCRIPTION

[0053] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0054] The present invention discloses a method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna, the method comprising the following steps:

[0055] Construct a 1-bit circularly polarized phase-coded transmission unit; wherein the RF radio frequency current signal received by the inner circle of the radiation patch flows to the outer circle of the radiation patch according to the selected PIN diode and generates circularly polarized radiation, and the radiation patch has two coding phase states of 0° and 180°;

[0056] Without changing the rest of the structure of the 1-bit circular polarization phase-coded transmission unit, the radiation patch of the 1-bit circular polarization phase-coded transmission unit is rotated 90° to form a type of unit placed orthogonally to the radiation layer of the original transmission unit; the original unit and the orthogonal unit are placed crosswise and staggered to form a unit structure block in a 2×2 array;

[0057] The positions of the original unit and the orthogonal unit in the 2×2 unit structure block are exchanged to form another type of 2×2 replacement structure block; the original structure block and the replacement structure block are further placed crosswise and staggered to form a 4×4 unit supercell; the radiation layer distribution pattern of the 4×4 unit supercell is approximately the rotation of the four 2×2 structure blocks in the order of 0°, 90°, 180° and 270°; the rest of the unit structure is arranged in the same way;

[0058] A 1-bit circularly polarized transmission array antenna is constructed with 4×4 unit supercell as the basic component. After receiving linearly polarized electromagnetic waves, each unit in the array uses 4×4 unit supercell as the basic block to reradiate circularly polarized electromagnetic waves. The main polarization components are superimposed on each other in the basic block, and the cross-polarization components are offset on each other in the basic block. Since the orthogonal placement of the radiation patches in the 4×4 unit supercell is equivalent to a dispersion-free rotation operation, cross-polarization suppression and main polarization superposition can be achieved in a broadband, thereby realizing a broadband and efficient radiation beam.

[0059] The present invention transforms a transmission metasurface unit (transmission unit) for linear polarization reception and circular polarization radiation, which mainly includes a fixed linear polarization reception patch, a metal ground plane, a circular polarization radiation layer with 1-bit phase regulation capability, and two layers of dielectric substrates; the linear polarization wave reception and circular polarization radiation patches are respectively located on the two side surfaces of the unit and are respectively attached to the two outer dielectric substrates; only the top circular polarization radiation patch has phase regulation capability; the linear polarization reception patch does not perform phase regulation, and is used to receive linear polarization electromagnetic waves that conform to the polarization direction, and converts them into RF radio frequency current signals, which are conducted to the radiation patch through the central metallized via hole; the radiation patch flows to the outer ring radiation patch according to the selected PIN diode and generates circular polarization radiation; the metal ground plane is located between the two layers of dielectrics and is used to isolate the reception and radiation patches; the center of the metal ground plane is pre-punched to allow the metallized via hole to pass through; as a concept verification, the transmission metasurface unit omits a DC bias network for controlling the conduction and cutoff of a PIN diode; the PIN diode that is turned on or off is replaced by a corresponding equivalent circuit.

[0060] The radiation patch of the transmission metasurface unit integrates two PIN diodes, and only one of them is turned on at the same time. At this time, the radiation patch has only two working states, that is, when PIN#1 / PIN#2 is ON / OFF, it is defined as state I, and when PIN#1 / PIN#2 is OFF / ON, it is defined as state II; the phase difference between the radiated circularly polarized beams in the two working states is 180°; due to the central symmetry property of the unit structure, the two states can be equivalent to a physical rotation of 180°.

[0061] like Figure 1 As shown, a 1-bit phase-reconfigurable metasurface transmission unit for linear polarization reception and circular polarization radiation is obtained by modifying a passive structure, which includes, from bottom to top, a bottom linear polarization receiving patch 1, a lower dielectric substrate 7, an intermediate isolation metal ground plane 5, an upper dielectric substrate 6, a central RF signal conduction metal via 4, a top circular polarization radiation patch 2 and two integrated PIN diodes 3; the metal ground plane 5 isolates the receiving layer and the radiation layer; the metal via 4 passes through the ground plane to connect the linear polarization receiving patch 1 and the circular polarization radiation patch 2; only one of the two PIN diodes is turned on at the same time to connect the outer ring radiation patch; as a conceptual illustration, all units and arrays do not consider the actual DC bias network.

[0062] The size of all dielectric substrates and metal ground planes is preferably a square with a side length of 15 mm, which is half the working wavelength. The working frequency here is selected in the X-band range of 8-12 GHz, and the central working frequency is 10 GHz; the material of the upper and lower dielectric substrates here is preferably F4B material with a dielectric constant of 3.5 and a loss tangent of 0.0015, and the thickness is preferably 1.524 mm. The use of dielectric substrates with different dielectric constants and different heights has a great influence on the performance of the receiving and radiating patches on the top and bottom layers. Under the condition of ensuring the effective reception and emission of circularly polarized electromagnetic waves by the metal patch under a specific unit size, the more common and relatively inexpensive preferred F4B material is selected, which is conducive to reducing the cost of the entire transmission array antenna;

[0063] The detailed structure of the linear polarization receiving patch 1 is as follows Figure 2 As shown, it is specifically a rectangular metal patch placed along the horizontal direction, and a 'U'-shaped groove is dug around the middle metal conductive via 4; the electromagnetic wave in the polarization direction (here horizontal polarization) of the structure is received by the receiving patch and converted into an RF radio frequency current signal, and then converges into the central metal conductive via 4 through the narrow metal microstrip line in the middle; Figure 2 The right side shows the middle layer isolation metal ground plane 5 of the unit, with a circular groove dug in the middle to allow the passage of the conductive via 4 while preventing electromagnetic waves from passing through the structural layer to the other side.

[0064] The specific structure of the circularly polarized radiation patch 2 integrating two PIN diodes 3 is shown in Figure 3 Among them, the whole is a centrally placed square metal patch with two cut corners in the main diagonal direction. In order to realize 1-bit phase modulation, a "mouth"-shaped groove is dug out in the middle part of the square patch, and the small patch in the middle is connected to the outer circle patch through a PIN diode; the RF radio frequency current signal flowing out of the conductive via 4 reaches the small patch in the middle, and then flows to the outer circle radiation patch through the turned-on diode (here the unit works in state I, and the PIN diode state is upper ON and lower OFF), thereby generating left-handed circularly polarized electromagnetic wave radiation (it should be noted that the radiation patch will generate right-handed circularly polarized electromagnetic wave radiation when the diagonal cut corner is cut, which is not a restrictive requirement here); Figure 3 On the right is the equivalent passive structure of the state I cell; similarly, Figure 4 The unit configuration working in state II (i.e., the PIN diode state is OFF at the top and ON at the bottom) is shown, and the corresponding passive structure is on the right; by comparing the passive structures of the two working states of the unit, it is not difficult to find that the switching of the two states can be equivalent to a 180° physical rotation between the two.

[0065] The reception of linearly polarized waves and the radiation of circularly polarized waves can be expressed by the following Jones matrix derivation process:

[0066] For the bottom layer linear polarization receiving patch, its transmission relationship can be expressed as:

[0067]

[0068] This shows that the receiving patch can be regarded as a polarizer, that is, it only allows the reception and transmission of y-polarized electromagnetic waves.

[0069] When the y-polarized electromagnetic wave is coupled to the top circularly polarized radiation patch and converted into a left-handed circularly polarized wave, the Jones matrix is:

[0070]

[0071] As mentioned above, the two states of the unit can be equivalent to a 180° physical rotation between them, and the corresponding process can be expressed as:

[0072]

[0073] Therefore, the above process can be written as

[0074]

[0075] Similarly, when converted to right-hand circularly polarized waves, the corresponding Jones matrix and transformation process can be written as:

[0076]

[0077]

[0078] When the y-polarized electric field is input, its electric field vector can be written as:

[0079] E i =(E x ,E y ) T =(0,1) T (0.7) The process of converting to the corresponding circularly polarized radiation wave is calculated according to the above equation:

[0080]

[0081] From the above derivation, it can be seen that the rotation of the top radiation patch has different phase modulation effects on different circularly polarized waves, that is, the rotation angle θ brings a phase shift of -θ for the left-hand circularly polarized wave, and brings an angular phase shift the same as the rotation angle θ for the right-hand circularly polarized wave; this is obviously different from the conventional Pancharatnam-Berry phase relationship which is twice the rotation angle.

[0082] For 1-bit phase discreteness (i.e., 0° and 180°), this geometric phase that is in a one-fold relationship makes the phase control of left-handed and right-handed circularly polarized waves have a strong correlation; that is, for a physical rotation of 180°, the phase shift of the left-handed circularly polarized wave is -180°, while the phase shift of the right-handed circularly polarized wave is +180°; we know that ±180° is in the same position in the range of [0,2π], which means that a 180° phase shift of a physical rotation of a right-handed circularly polarized wave will inevitably bring about a 180° phase shift of a left-handed circularly polarized wave, and the two are strongly correlated.

[0083] Figure 5 The amplitude response of the unit when it is operating in state I is given. It can be seen that the main polarization of the unit is left-hand circular polarization (LCP) and the cross polarization is right-hand circular polarization (RCP); Figure 6 The left side shows the phase of the main polarization LCP and the phase difference between the two in state I and state II, and the right side shows the phase and phase difference of the cross-polarization RCP; Obviously, although LCP and RCP have different phases, the two states at all frequencies have a phase difference of 180°. The above results demonstrate the correctness of the theoretical derivation, indicating that in the same array antenna (UEA) with uniform arrangement, while the main polarization LCP is adjusted, the RCP will respond in a consistent manner, that is, the two have the same phase distribution diagram; specifically, the two polarized electromagnetic waves will be superimposed in the same direction in the far field, and two polarized beams will be formed at the same time, of course, the intensity varies according to the amplitude response of the unit.

[0084] Obviously, although the 1-bit circularly polarized uniform array antenna (UEA) can achieve the desired beam steering, it will also bring about unwanted cross-polarized beams in the same direction, causing serious deterioration of the axial ratio in the main beam direction, thereby seriously affecting the polarization purity of the circularly polarized array antenna. This obviously greatly limits the application of the 1-bit circularly polarized array antenna.

[0085] In order to solve the above problems, the present invention proposes a method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna. Based on this method, two improved solutions for 1-bit circularly polarized array antennas are obtained:

[0086] Improvement plan 1: Physically rotate the radiation layer of the original 1-bit reconfigurable transmission unit by 90°, and keep the rest unchanged. This forms a unit that is placed orthogonally to the original unit. Figure 7 The structural schematics of the two unit radiation layers are given, and they are represented by the letters 'V' and 'H' according to the orientation of the integrated PIN diodes; the 2×2 structural block adopts the original unit and the orthogonal unit to be placed in a cross-arrangement, and only the circularly polarized radiation layer is rotated 90° as a whole to obtain the rotated orthogonal unit. The bottom linear polarization receiving patch of the 2×2 structural block maintains a uniform and identical arrangement, thereby introducing a 90° rotational phase shift while retaining the 1-bit phase control capability of the original unit structure. When the phase of each unit of the array antenna is discretized, the unit phase distribution in the subarray will meet the phase requirement of the main polarization beam as much as possible, while the 90° rotational phase shift of the orthogonal unit will disrupt the phase distribution of the cross-polarization component, making it impossible to form a cross-polarization beam in the same direction in the far field, thereby improving the cross-polarization ratio, reducing the axial ratio and improving the polarization purity. Figure 8 A schematic diagram of a 2×2 structural block based on a transmission unit and its corresponding unit structure diagram are given.

[0087] Improvement scheme 2: Further improvements are made on the basis of the original 2×2 structural block to obtain a 4×4 structural block supercell. Specifically, while retaining the function of the original 2×2 structural block, adjustments are made to the distribution of 'V' and 'H' units. Specifically, the positions of the 'V' unit and the 'H' unit in the 2×2 unit structural block are exchanged to form another type of 2×2 replacement structural block; the original structural block and the replacement structural block are further placed in a cross-staggered manner to form a 4×4 unit supercell; the radiation layer distribution pattern of the 4×4 unit supercell is approximately the rotation of 4 2×2 structural blocks in the order of 0°, 90°, 180° and 270°; due to the orthogonal relationship of the rotation of multiples of 90°, the 4×4 structural block supercell does not change the relative position of the existing units, that is, the supercell still has only the original and orthogonal unit structures; similarly, the bottom layer linear polarization receiving patches of the 4×4 structural block maintain a uniform and identical arrangement. Fig. 9 The schematic diagram of the 4×4 structural block supercell based on the transmission unit and its corresponding unit structure diagram are given. Fig. 9 It shows that each 2×2 structural block is distributed in rotational symmetry. Such a rotational layout structure not only allows the main polarization components to be further superimposed, but also allows the cross-polarization components to further cancel each other in the sub-array, thereby effectively eliminating the cross-polarization components from forming superposition interference with the main polarization beam in the far field.

[0088] Fig.10 A schematic diagram of the structure of a circularly polarized transmission array metasurface with a scale of 16×16 is given, including a linearly polarized feed horn antenna and a linearly polarized receiving patch uniformly arranged at the bottom layer. As a comparison, the present invention provides four radiation layer schemes with different layouts, namely, a continuous rotation array Continue-Phase Array, CPA, which performs continuous rotation phase modulation with the equivalent passive structure when the unit works in state I, a 1-bit coded phase uniform array (Uniform-Element Array, UEA) with a uniform layout of vertical units, an orthogonal unit array (Orthogonal-Element Array, OEA) with a 2×2 structural block as a basic component, and an orthogonal rotation unit array (Orthogonal-Element Array with Rotation, OEAR) with a 4×4 structural block supercell as a basic component. The receiving patch layer in the above four arrays is replaced with a feeding network, that is, a radiating metasurface consisting of only a single layer of radiating patches is formed, and its performance is analyzed and compared with the above-mentioned transmission array antenna.

[0089] Fig.11 The continuously rotating array radiation pointing is given The continuous compensation phase of the directional beam in the direction and the distribution of the radiation patch corresponding to the rotation angle, the compensation phase can be calculated according to the following formula:

[0090]

[0091] Among them, λ is the wavelength corresponding to the antenna operating frequency, (x, y) is the horizontal and vertical coordinates of the center of each unit in the array, F is the height of the phase center of the normal vertically placed feed antenna from the plane receiving layer of the transmission array, which is preferably 160mm here, and the focal diameter ratio F / D of the feed and the array is preferably 0.667, where D is preferably the side length of the square reflecting surface of 240mm.

[0092] Fig.12 The unit distribution of the UEA uniform array and the corresponding discrete phase distribution are given. Since the array uses only one unit, it only has two discrete phases of 0° and 180°; the discrete criterion is:

[0093]

[0094] For the OEA and OEAR arrays, since two types of units are placed in the array, a 90° rotation phase shift is added to the two discrete phases of 0° and 180°, so there are four discrete phases of 0°, 90°, 180° and 270°; in addition, since the positions of the 'V' and 'H' units are relatively fixed, the phase discrete criterion is changed to:

[0095]

[0096] Need to explain, φ cont is the calculated continuous compensation phase, 'V' and 'H' represent the vertical unit and the horizontal unit respectively; State I is the 0° and 270° phase obtained by the two types of units, and State II is the 180° and 90° phase obtained by the two types of units. The unit distribution diagram of the OEA and OEAR array antennas and their corresponding discrete phase distribution are shown as follows Fig.13 and Fig.14 shown.

[0097] As a performance comparison, Fig.15The radiation patterns of four types of transmission array antennas with fixed transmission beam pointing are given, including co-polarization and cross-polarization transmission components; it can be seen that the continuous phase modulation array has a very good main polarization beam pattern, its direction is consistent with the pre-set, and has a good sidelobe level and cross-polarization level, the main beam gain is as high as 23.5dBi, the sidelobe level is lower than 26.3dB, and the cross-polarization level is lower than 20.5dBi. The performance of the continuous phase modulation array can be used as the best ideal antenna performance for discrete solutions. Consistent with the above analysis, the radiation pattern of the UEA uniform array has both main polarization and cross-polarization beams in the set 30° direction. The main polarization beam gain is 19.1dBi, and the cross-polarization beam gain is as high as 13.8dBi. This obviously seriously deteriorates the polarization purity of the circularly polarized beam. It can be expected that the axial ratio of the beam will be relatively poor, which is obviously not suitable for the application of circularly polarized antennas. For the OEA array with 2×2 structural block subarrays, its radiation pattern shows that the cross-polarization components do not form an effective superposition in the main beam direction to generate a beam, which fully demonstrates the effectiveness of the proposed scheme to disrupt the phase distribution of the cross-polarization components; the main polarization beam also appears in the predetermined direction, with a beam gain of 19.9dBi and a co-polarization sidelobe level lower than -15dB; it should be noted that although the cross-polarization components do not form a superposition in the main beam direction, higher sidelobes appear in other directions. Compared with the UEA array, the main beam gain is not significantly improved, indicating that the energy is dispersed to other directions. For the further optimized 4×4 structure block OEAR array, the main polarization beam gain is as high as 21.2dBi, the co-polarization sidelobe level is lower than -15dB, and the beam points to the predetermined direction; in addition, observation of the cross-polarization component shows that it neither converges in the main beam direction nor has high spurious sidelobes in other directions, indicating that the cross-polarization components have canceled each other out in the sub-array and cannot be superimposed in any direction in the far field, and the cross-polarization sidelobe level is lower than -18dB overall; compared with the ideal continuous phase modulation array, the 4×4 structure block OEAR array achieves a similar level of cross-polarization component suppression; this fully demonstrates the outstanding ability of the OEAR array to suppress cross-polarization components.

[0098] To further analyze the bandwidth performance of the array, Fig.16The curves of the gain variation with frequency in the main beam direction of the four arrays are given respectively, including main polarization and cross polarization. Compared with the ideal continuous phase modulation array, it can be found that the main polarization and cross polarization gains of the UEA uniform array show the same curve as the unit, which can almost be regarded as a simple superposition of unit performance. It is difficult to achieve effective suppression of undesired cross-polarization components, indicating that the UEA array cannot be used as a design for a 1-bit reconfigurable circularly polarized scanning array antenna; observing the gain curve of the OEA array, it can be seen that although it has achieved suppression of cross-polarization components in some frequency bands, it still retains a relatively high cross-polarization gain in other frequency bands, which is not conducive to the practical application of 1-bit reconfigurable circularly polarized scanning array antennas; surprisingly, the OEAR array achieves the same cross-polarization suppression level as the ideal continuous phase modulation array in the full frequency band of 8-12GHz, and the gain difference with the main polarization beam in a wider frequency band is less than -15dB; combined with Fig.17 From the main beam axial ratio bandwidth shown, it can be seen that the beam axial ratio of the UEA and OEA arrays is less than 3dB only in a narrow frequency range. Compared with the 3dB axial ratio bandwidth of 19.5% of the ideal continuous phase modulation array, the OEAR array achieves a 3dB axial ratio bandwidth as wide as 32.7%, that is, the beam axial ratio is less than 3dB in the broadband range of 8.2-11.4GHz. This fully demonstrates that the 4×4 structural blocks in the OEAR array can effectively suppress the cross-polarization components of circular polarization in a broadband range.

[0099] In addition, aperture efficiency is also an important parameter to measure the performance of array antennas. Fig.18 The aperture efficiency corresponding to the main polarization gain of four arrays in the main beam direction is given. It can be seen that compared with the ideal continuous phase modulation array, the OEAR scheme achieves an aperture efficiency of up to 21.6% at the center operating frequency of 10GHz, which is a relatively high aperture efficiency for the transmission array with 1bit discrete phase. The above performance fully demonstrates the excellent ability of the OEAR scheme in broadband suppression of cross-polarization components and further improving the energy convergence in the main polarization beam direction. These capabilities make it widely used in transmission array antennas with 1bit discrete coding phase, especially 1bit circularly polarized electronically scanned array antennas with integrated adjustable devices, which can realize simple, broadband, and high-performance circularly polarized beam scanning.

[0100] The proposed OEA and OEAR arrays only utilize a single-layer phase modulation functional layer, which not only solves the inherent defects of traditional 1-bit circularly polarized array antennas, but also realizes simple and high-performance circularly polarized beam radiation; the two schemes proposed in the present invention can be widely used in circularly polarized array antennas that require a single phase modulation functional layer, such as circularly polarized phased array antennas and radiating metasurfaces.

[0101] Compared with the prior art, the unit of the present invention is a radiation structure, which can achieve 1-bit transmission phase control without rotation. The purpose of adopting 90° rotation orthogonality is to introduce additional rotation phase to disrupt the distribution of the cross-polarization component phase of the radiated circularly polarized wave, so that the cross-polarization components cancel each other in the structural block subarray, thereby avoiding interference with the main polarization beam in the same direction. Therefore, this patent is essentially different from the present invention. In addition, the unit of the present invention first directly controls the circularly polarized electromagnetic wave, and does not require additional reference phase settings; the 1-bit phase characteristic of the unit itself is equivalent to a physical rotation of 180°, and a physical rotation of 90° is added on this basis. Therefore, when determining the discrete phase, the unit rotation angle in the 2×2 structural block is not relatively fixed, and the closest phase rotation angle setting can be achieved according to the beam requirements, while retaining the advantages of the rotating array, the setting freedom is expanded; in addition, the present invention does not make a rigid requirement for the reference phase for the control of the circularly polarized wave, so there is no need to make a trade-off and compromise on the beam polarization and beam gain; the reference phase can be set additionally and independently to take into account the polarization purity and beam gain of the circularly polarized beam, which is particularly important for large-angle circularly polarized beam scanning.

[0102] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0103] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0104] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0105] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0106] 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.

[0107] 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 method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna, characterized in that: The method comprises the following steps: Construct a 1-bit circularly polarized phase-coded transmission unit; wherein the RF radio frequency current signal received by the inner circle of the radiation patch flows to the outer circle of the radiation patch according to the selected PIN diode and generates circularly polarized radiation, and the radiation patch has two coding phase states of 0° and 180°; Without changing the rest of the structure of the 1-bit circular polarization phase-coded transmission unit, the radiation patch of the 1-bit circular polarization phase-coded transmission unit is rotated 90° to form a type of unit placed orthogonally to the radiation layer of the original transmission unit; the original unit and the orthogonal unit are placed crosswise and staggered to form a unit structure block in a 2×2 array; The positions of the original unit and the orthogonal unit in the 2×2 unit structure block are exchanged to form another type of 2×2 replacement structure block; the original structure block and the replacement structure block are further placed crosswise and staggered to form a 4×4 unit supercell; the radiation layer distribution pattern of the 4×4 unit supercell is approximately the rotation of the four 2×2 structure blocks in the order of 0°, 90°, 180° and 270°; the rest of the unit structure is arranged in the same way; A 1-bit circularly polarized transmission array antenna is constructed with 4×4 unit supercell as the basic component. After receiving the linearly polarized electromagnetic wave, each unit in the array uses the 4×4 unit supercell as the basic block to re-radiate the circularly polarized electromagnetic wave. The main polarization components are superimposed on each other in the basic block, and the cross-polarization components are offset on the basic block. The orthogonal placement of the radiating patches in the 4×4 unit supercell is equivalent to a dispersion-free rotation operation, which realizes cross-polarization suppression and main polarization superposition in a broadband, thereby realizing a broadband and efficient radiation beam.

2. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna according to claim 1, characterized in that: The 1-bit circular polarization phase-encoded transmission unit includes a linear polarization receiving patch, a metal ground plane, a radiation patch with 1-bit phase regulation capability, and two layers of dielectric substrates; The linear polarization wave receiving patch and the circular polarization wave radiating patch are respectively located on the two side surfaces of the transmission unit and are respectively attached to two layers of dielectric substrates; The linear polarization receiving patch is used to receive linear polarization electromagnetic waves that conform to the polarization direction, convert them into RF radio frequency current signals and conduct them to the inner circle of the radiating patch; the radiating patch transmits the RF radio frequency current signal to the outer circle of the radiating patch according to the selected PIN diode and generates circular polarization radiation; The metal ground plane is located between the two layers of dielectric substrates and is used to isolate the linear polarization wave receiving patch and the circular polarization wave radiating patch; a hole is pre-punched in the center of the metal ground plane to allow the central metal conduction via to pass through; The radiation patch integrates two PIN diodes, only one of which is turned on at the same time. According to the conduction state of the PIN diode, the radiation patch includes two working states, and the phase difference of the radiation circularly polarized beams in the two working states is 180°.

3. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna according to claim 2, characterized in that: The dielectric substrate and the metal ground plane are both square with a side length of 15 mm, and the electrical size thereof is half the working wavelength. The working frequency of the transmission unit is selected in the X-band range of 8 GHz-12 GHz, and the central working frequency is 10 GHz.

4. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna according to claim 2, characterized in that: The dielectric substrate is made of F4B material with a dielectric constant of 3.5 and a loss tangent of 0.0015, and a thickness of 1.524 mm.

5. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna according to claim 2, characterized in that: The linearly polarized receiving patch is a rectangular metal patch placed in the horizontal direction, with a central metal conductive via in the middle and a U-shaped groove around the central metal conductive via. The electromagnetic waves that conform to the structural polarization direction are received by the linearly polarized receiving patch and converted into RF radio frequency current signals, and are merged into the central metal conductive via through the metal microstrip line in the middle, and then pass through the circular groove in the middle of the metal ground plane to reach the radiation patch.

6. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna according to claim 2, characterized in that: The radiation patch is a centrally placed square metal patch with two cut corners in the main diagonal direction. A mouth-shaped groove is provided in the middle part of the square patch. The inner circle patch is connected to the outer circle patch through two PIN diodes. The RF radio frequency current signal flowing out of the central metal conduction via reaches the inner circle patch and then flows to the outer circle patch through the turned-on PIN diode, generating left-handed circularly polarized electromagnetic wave radiation.

7. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna according to claim 1, characterized in that: The 1-bit circularly polarized transmission array antenna continuously rotates the array radiation pointing The continuous compensation phase of the directional beam in the direction and the compensation phase of the radiation patch distribution rotated to the corresponding angle are: Among them, λ is the wavelength corresponding to the antenna operating frequency, (x, y) is the horizontal and vertical coordinates of the center of each transmission unit in the array, F is the height of the phase center of the normal-placed vertical feed antenna from the plane receiving layer of the transmission array, and φ0 is the reference phase.

8. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna according to claim 1, characterized in that: The phase discretization criterion of the 1-bit circularly polarized transmission array antenna is: In the formula, φ cont is the calculated continuous compensation phase, 'V' and 'H' represent the vertical unit and the horizontal unit respectively; State I is the 0° and 270° phases obtained by the two types of units being discrete, and State II is the 180° and 90° phases obtained by the two types of units being discrete.

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