A method for improving bandwidth and efficiency of 1bit circularly polarized transmit array antenna

Abstract

The application discloses a method for improving the bandwidth and efficiency of a 1bit circularly polarized transmission array antenna, which comprises the following steps: rotating the radiation patch of a 1bit circularly polarized phase encoding transmission unit by 90 degrees to form a type of unit which is orthogonally arranged with the radiation layer of the original transmission unit; cross-distributing the original transmission unit and the orthogonal unit to form a 2*2 structure block; exchanging the positions of the original unit and the orthogonal unit in the 2*2 structure block to form a 2*2 permutation structure block; cross-distributing the original structure block and the permutation structure block to form a 4*4 unit supercell; the radiation layer distribution pattern of the 4*4 unit supercell is approximately the order rotation of 4 2*2 structure blocks at 0 degrees, 90 degrees, 180 degrees and 270 degrees; and the 4*4 unit supercell is used to construct a 1bit circularly polarized transmission array antenna. The application solves the strong correlation of the main polarization and cross-polarization phase control in the uniform array, and improves the axial ratio bandwidth of the circularly polarized beam and the aperture efficiency of the array antenna.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical or electromagnetic radiation regulation, microwave and antenna technology, and in particular to a method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmission array antenna, which can effectively improve the axial ratio bandwidth and aperture efficiency of a circularly polarized radiation array antenna with 1-bit phase coding requirements and other radiation performance. BACKGROUND

[0002] As one of the important components of radar detection and wireless communication systems, circularly polarized antennas have received widespread attention in various application scenarios due to their advantages in anti-interference and multi-path effect reduction. However, with the development of the times, the flexible and rapid beam scanning capability has posed great challenges to existing antenna forms; traditional mechanical scanning and electric scanning realized by loading phase shifters have inherent defects and have been difficult to meet the requirements of modern detection and communication systems.

[0003] In the past two decades, some scholars have proposed using the digital coding phase regulation capability of metasurfaces to realize arbitrary controllable electromagnetic wave manipulation, which is simpler in form and more compact in implementation compared to continuous phase control by phase shifters; in addition, the low cost and easy integration of metasurfaces also have advantages in antenna system implementation. However, for continuous phase that can be realized by phase shifters, array antennas with discrete coding phase are only an approximation of continuous phase regulation; the more coding states, the closer to continuous phase regulation, and the more complex the implementation; the fewer coding states, the simpler the implementation, but also means greater approximation error; the lowest 1-bit (i.e., only two states of 0° and 180°) or 2-bit (i.e., four states of 0°, 90°, 180°, and 270°) coding number is the scheme adopted by most existing research; however, although the 2-bit discrete scheme has a more approximate phase distribution and radiation performance, it requires more device integration and a more complex network configuration; therefore, the 1-bit phase discrete scheme has been favored by most researchers.

[0004] For simple linearly polarized wave regulation, due to the natural high isolation between orthogonal polarizations, uniform unit arrangement can achieve better sidelobe and cross-polarization performance using optimization algorithms. However, for circularly polarized waves, the unique unit structure and phase regulation mechanism determines that there is a strong phase binding relationship between the main polarization and the cross-polarization. If the distribution of discrete phase is unreasonable, it will cause the main polarization and cross-polarization to superimpose in the unexpected direction, thus deteriorating the radiation performance of the antenna; Therefore, the 1bit phase discrete scheme is difficult to apply in circularly polarized array antennas, especially for transmissive array antennas; The existing 1bit phase discrete scheme is mostly limited to circularly polarized reflective array antennas, but it has significant feed blockage and high profile problems; In order to solve the phase discrete problem in circularly polarized transmissive array antennas, researchers have successively proposed multi-bit structure, multi-layer phase regulation function layer and other schemes, which undoubtedly increase the design complexity of the unit structure and the phase regulation complexity, making it difficult to meet the application requirements of actual circularly polarized antennas. Therefore, there are still many technical challenges to realize high-performance 1bit circularly polarized transmissive array antennas with a single phase modulation function layer.

[0005] The invention disclosed in patent publication No. CN117013270A is a scattering beam reconfigurable low RCS circularly polarized antenna array, which includes a feed network, a dielectric plate and a radiation patch. It is a radiation type metasurface by definition, without receiving layer patch and spatial feed source. On the other hand, the unit radiation patch is placed orthogonally to make the scattering cancellation of the co-polarization and cross-polarization components of the linearly polarized incident wave on the radiation patch, and to realize the reconfigurable regulation of the scattering beam by changing the unit state. In order to cope with the influence of regulating linearly polarized scattering beam on circularly polarized radiation beam, a complex phase shifter network is required to offset this influence. From the perspective of radiation, the structure does not realize controllable circularly polarized radiation beam, and additional phase shifter network is required to correct the phase, and the circularly polarized radiation beam is always directed to 0°. From the perspective of the whole unit layout and phase correction phase shifter, the circularly polarized wave radiated by each unit in the orthogonal unit pattern has the same phase, and the suppression of the cross-polarization component of the radiated circularly polarized wave is not considered or realized.

[0006] The invention disclosed in patent publication No. CN116207511A discloses a design method of a full polarization high-gain antenna and an antenna. The antenna is first a kind of reflection array by definition, which controls the reflection beam by controlling the state of the diode on the unit when electromagnetic waves are irradiated onto the unit. From the functional mechanism, the switching of the two states of the unit is equivalent to a 90° physical rotation, and the purpose is to introduce a 180° 1bit 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 1bit phase control of the unit is realized by 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 disclosed in patent publication No. CN112949032B discloses a design method of a full polarization reconfigurable planar reflection array antenna technology. First, the antenna is first a kind of reflection array by definition, which controls the reflection beam by controlling the state of the diode on the unit when electromagnetic waves are irradiated onto the unit. Second, since the antenna unit mainly controls two orthogonal linearly polarized electromagnetic waves in a 1bit manner, it cannot directly generate or control circularly polarized electromagnetic waves. In order to realize the control of circularly polarized waves, different reference phases need to be set for the two linear polarization components, which cannot be controlled by electrical signals. In order to improve the quality of the circularly polarized beam, several units are placed in order and rotated, but the relative positions are fixed and cannot be changed by changing the state of the PIN diode. Although this scheme can suppress cross-polarization to some extent, the reference phase needs to be optimized constantly when scanning the circularly polarized beam, which inevitably affects the gain and efficiency of the circularly polarized beam. SUMMARY

[0008] The purpose of the present application is to provide a method for improving the bandwidth and efficiency of a 1bit circularly polarized transmission array antenna. Without changing the existing structure, the technical solution discussed arranges two orthogonally placed radiation layer patch units in a specific pattern, which eliminates the strong correlation between the phase control of the main polarization and the cross-polarization in the uniform array. Not only does it achieve the effect of canceling cross-polarization in a wide band, but it also significantly improves the axial ratio bandwidth of the circularly polarized beam, so that the energy can be further superimposed in the desired way, effectively increasing the aperture efficiency of the array antenna. The scheme discussed can be widely applied to radiation circularly polarized antennas with 1bit electrically controlled phase adjustment capability, and is not only suitable for circularly polarized transmission array antennas with receiving and radiating patches, but also suitable for all array antennas with single-layer radiation layer circularly polarized patches, such as phased arrays and radiation super surfaces, etc.

[0009] To achieve the above technical purpose, the technical solution adopted by the present application is as follows:

[0010] The application discloses a method for improving the bandwidth and efficiency of a 1bit circularly polarized transmitting array antenna.

[0011] A 1bit circularly polarized phase coding transmitting unit is constructed; wherein the RF current signal received by the inner circle of the radiating patch is transmitted to the outer circle of the radiating patch according to the gating PIN diode and circularly polarized radiation is generated, and the radiating patch has two coding phase states of 0° and 180°;

[0012] Without changing the rest of the structure of the 1bit circularly polarized phase coding transmitting unit, the radiating patch of the 1bit circularly polarized phase coding transmitting unit is rotated by 90° to form a type of unit arranged orthogonally to the radiating layer of the original transmitting unit; the original unit and the orthogonal unit are cross-displaced to form a 2*2 unit structure block;

[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 displacement structure block; further, the original structure block and the displacement structure block are cross-displaced to form a 4*4 unit supercell; the radiating layer distribution pattern of the 4*4 unit supercell is approximately the order rotation of 0°, 90°, 180° and 270° of the four 2*2 structure blocks; the rest of the structure of the unit is arranged in the same way;

[0014] The 1bit circularly polarized transmitting array antenna is constructed based on the 4*4 unit supercell; after receiving linearly polarized electromagnetic waves, each unit in the array uses the 4*4 unit supercell as a basic block, and the main polarization components of the circularly polarized electromagnetic waves radiated again are superimposed on each other in the basic block, and the cross-polarization components are cancelled out in the basic block; since the orthogonal arrangement of the radiating patches in the 4*4 unit supercell can be equivalent to a rotation operation without dispersion, the cross-polarization suppression and the main polarization superposition can be realized in a wide band, so that a wideband and efficient radiation beam is realized.

[0015] Further, the 1bit circularly polarized phase coding transmitting unit comprises a linearly polarized receiving patch, a metal ground plane, a radiating patch with 1bit phase control capability and two layers of dielectric substrates;

[0016] The linearly polarized wave receiving patch and the circularly polarized wave radiating patch are respectively located on the two side surfaces of the transmitting unit and are attached to the two layers of dielectric substrates;

[0017] The linearly polarized receiving patch is used for receiving linearly polarized electromagnetic waves in the polarization direction, converting the linearly polarized electromagnetic waves into RF current signals and conducting the RF current signals to the inner circle of the radiating patch; the radiating patch transmits the RF current signals to the outer circle of the radiating patch according to the gating PIN diode and generates circularly polarized radiation;

[0018] The metal ground plane is located in the middle of the two-layer dielectric substrate, and is used for isolating linearly polarized wave receiving patch and circularly polarized wave radiating patch; the metal ground plane is pre-penetrated in the center, so that the central metal conductive via passes through;

[0019] The radiation patch is integrated with two PIN diodes, only one of which is turned on at the same time, and the radiation patch includes two working states according to the turn-on state of the PIN diode, and the phase difference between the two working states of the radiation circularly polarized wave beam is 180°.

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

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

[0022] Further, the linearly polarized receiving patch is a rectangular metal patch placed along the horizontal direction, and a central metal conductive via is arranged in the middle, and a U-shaped groove is arranged around the central metal conductive via; the electromagnetic wave conforming to the structural polarization direction is received by the linearly polarized receiving patch and converted into an RF radio frequency current signal, and is collected into the central metal conductive via through the metal microstrip line in the middle, and then passes through the circular slot in the middle of the metal ground plane to reach the radiation patch.

[0023] Further, the radiation patch is a square metal patch placed in the center, and has two cut angles in the main diagonal direction, and a mouth-shaped groove is arranged in the middle part of the square patch, and the inner ring patch is connected with the outer ring patch through two PIN diodes; the RF radio frequency current signal flowing out of the central metal conductive via flows to the outer ring patch through the turned-on PIN diode after reaching the inner ring patch, and generates left-handed circularly polarized electromagnetic wave radiation.

[0024] Further, the 1bit circularly polarized transmission array antenna continuously rotates the array radiation pointing The compensation phase of the radiation patch distribution corresponding to the rotation angle of the directional beam in the continuous compensation phase of the directional beam in the continuous rotation array is:

[0025]

[0026] Wherein, λ is the wavelength corresponding to the working frequency of the antenna, (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 vertically placed feed source antenna from the receiving layer of the transmission array plane, and φ0 is the reference phase.

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

[0028]

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

[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 adopts a rotation strategy and also cancels out the 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 radiating or transmitting circularly polarized array arranged using this scheme has a good cross-polarization level and axial ratio bandwidth within the broadband.

[0032] Second, the present invention's method for improving the bandwidth and efficiency of 1-bit circularly polarized transmission array antennas is applicable to all array antennas requiring single-layer circularly polarized phase encoding, such as circularly polarized radiating patches with 1-bit phase control capability in transmission elements, single-layer radiating circularly polarized phased arrays, and circularly polarized radiating metasurfaces using a feed network for unified feeding. This approach offers important insights into 1-bit real-time reconfigurable circularly polarized array antennas with integrated active devices, significantly 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, capable of linearly polarized reception and 1-bit circularly polarized 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 1Top view of the unit, specifically the structure of a circularly polarized radiating patch, on which two PIN diodes are integrated; the two diodes work in 'ON / OFF' state, marked as state I; the right figure is the equivalent passive patch structure of state I;

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

[0037] Figure 5 Transmission amplitude response of the linear-to-circular polarization conversion for the unit of the 1-bit unit working in state I.

[0038] Figure 6 Transmission phase curves of the principal and cross-polarization components and the corresponding phase difference for the 1-bit unit working in both states.

[0039] Figure 7 Radiation patch schematic of two units according to the PIB diode being placed orthogonally.

[0040] Figure 8 Schematic of a 2x2 structure block composed of two units, and the corresponding unit subarray structure.

[0041] Figure 9 Schematic of a 4x4 structure block composed of two units, and the corresponding unit supercell structure.

[0042] Figure 10 Schematic of a 16x16 array antenna composed of the unit, including a linearly polarized feed horn and a bottom layer of the same arrangement of linearly polarized receiving patches.

[0043] Figure 11 Calculated continuous compensation phase required for the directive beams, and the corresponding continuous phase modulated array radiating layer.

[0044] Figure 12 Schematic of an array radiating layer with vertical units arranged in the same way, and the 1-bit phase distribution diagram obtained by discretizing the continuous phase.

[0045] Figure 13 Schematic of an array radiating layer composed of two units arranged in a 2x2 structure block, and the 1-bit / quasi-2-bit phase distribution diagram obtained by discretizing the continuous phase.

[0046] Figure 14Schematic diagram of array radiation layer composed of two units arranged in 4x4 structure block, and 1-bit / quasi-2-bit phase distribution diagram obtained by discretizing continuous phase.

[0047] Figure 15 Main polarization and cross polarization far field radiation patterns of four array antennas of continuous phase modulation array, UEA uniform array, 2x2 structure block OEA array and 4x4 supercell OEAR array.

[0048] Figure 16 Frequency variation curves of main polarization and cross polarization gain in the main beam direction of four array antennas of continuous phase modulation array, UEA uniform array, 2x2 structure block OEA array and 4x4 supercell OEAR array.

[0049] Figure 17 Frequency variation curves of axial ratio in the main beam direction of four array antennas of continuous phase modulation array, UEA uniform array, 2x2 structure block OEA array and 4x4 supercell OEAR array.

[0050] Figure 18 Frequency variation curves of aperture efficiency corresponding to main polarization gain in the main beam direction of four array antennas of continuous phase modulation array, UEA uniform array, 2x2 structure block OEA array and 4x4 supercell OEAR array.

[0051] The reference signs in the drawings are as follows:

[0052] 1. Bottom layer linear polarization receiving patch; 2. Top layer circular polarization radiation patch; 3. Integrated two PIN diodes; 4. Central RF signal conducting 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 application will be further described in detail below with reference to the accompanying drawings.

[0054] The present application discloses a method for improving the bandwidth and efficiency of a 1bit circularly polarized transmission array, which comprises the following steps:

[0055] A 1bit circularly polarized phase encoding transmission unit is constructed; wherein the RF current signal received by the inner circle of the radiation patch flows to the outer circle of the radiation patch according to the gating PIN diode and generates circularly polarized radiation, and the radiation patch has two encoding phase states of 0° and 180°;

[0056] Without changing the rest of the structure of the 1bit circular polarization phase encoding transmission unit, the radiation patch of the 1bit circular polarization phase encoding transmission unit is rotated by 90° to form a type of unit which is orthogonally placed with the radiation layer of the original transmission unit; the original unit and the orthogonal unit are cross-displaced to form a 2*2 unit structure block;

[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 displacement structure block; further, the original structure block and the displacement structure block are cross-displaced to form a 4*4 unit supercell; the radiation layer distribution pattern of the 4*4 unit supercell is approximately the order of 0°, 90°, 180° and 270° rotation of the four 2*2 structure blocks; the rest of the structure of the unit is the same arrangement;

[0058] Based on the 4*4 unit supercell as a basic component, a 1bit circular polarization transmission array antenna is constructed. After receiving linearly polarized electromagnetic waves, each unit in the array radiates the main polarization component of the circularly polarized electromagnetic waves in the basic block, and the cross-polarization component is cancelled in the basic block. Since the orthogonal placement of the radiation patches in the 4*4 unit supercell can be equivalent to a non-dispersive rotation operation, cross-polarization suppression and main polarization superposition can be realized in a wide band, thereby realizing a wideband and efficient radiation beam.

[0059] The application modifies a transmission metasurface unit (transmission unit) which receives linear polarization and radiates circular polarization, mainly including a fixed linear polarization receiving patch, a metal ground plane and a circular polarization radiation layer with 1bit phase control capability, and two layers of dielectric substrates; the linear polarization wave receiving and circular polarization radiation patches are respectively located on the two side layers of the unit and are attached to the two layers of outer dielectric substrates; only the top circular polarization radiation patch has phase control capability; the linear polarization receiving patch does not have phase control, receives linearly polarized electromagnetic waves in the polarization direction and converts them into RF radio frequency current signals, which are conducted to the radiation patch through the central metalized via; the radiation patch flows to the outer radiation patch according to the gating PIN diode and generates circular polarization radiation; the metal ground plane is located in the middle of the two layers of dielectric and is used to isolate the receiving and radiation patches; the central of the metal ground plane is pre-punched to allow the metalized via to pass through; as a proof of concept, the transmission metasurface unit omits the direct current bias network for controlling the conduction and cutoff of the PIN diode; the conduction or cutoff PIN diode is replaced by the corresponding equivalent circuit.

[0060] The radiation patch of the transmission metasurface unit integrates two PIN diodes, only one of which is turned on at the same time, at which time the radiation patch has only two working states, i.e., state I when PIN#1 / PIN#2 is ON / OFF, and state II when PIN#1 / PIN#2 is OFF / ON; the phase difference of the two working states of the radiation circularly polarized wave beam is 180°; due to the central symmetry of the unit structure, the two states can be equivalent to a physical rotation of 180°.

[0061] As shown in Figure 1 , a 1bit phase reconfigurable transmission metasurface unit for linearly polarized receiving and circularly polarized radiation is obtained by modifying a passive structure, from bottom to top, it is a bottom linearly polarized receiving patch 1, a lower layer dielectric substrate 7, a middle layer isolation metal ground plane 5, an upper layer dielectric substrate 6, a central RF signal conducting metal via 4, a top circularly polarized radiation patch 2 and two integrated PIN diodes 3; the metal ground plane 5 separates the receiving layer and the radiation layer; the metal via 4 connects the linearly polarized receiving patch 1 and the circularly polarized radiation patch 2 by passing through the ground plane; only one of the two PIN diodes is turned on at the same time, which is used to connect the outer 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 one half of the working wavelength, and the working frequency is selected in the X-band 8-12GHz range, with a center working frequency of 10GHz; here the material of the upper and lower dielectric substrates is preferably F4B material with a dielectric constant of 3.5 and a loss tangent of 0.0015, and the thickness is preferably 1.524mm; the selection of dielectric substrates with different dielectric constants and heights has a great influence on the performance of the receiving and radiation patches of the top and bottom layers; under the condition of ensuring the effective reception and transmission of circularly polarized electromagnetic waves by metal patches with a specific unit size, the selection of the relatively common and relatively low-cost preferred F4B material is conducive to reducing the cost of the entire transmission array antenna;

[0063] The detailed structure of the linearly polarized receiving patch 1 is shown in Figure 2 , specifically a rectangular metal patch is placed along the horizontal direction, and a 'U' shaped slot is dug around the middle metal conducting via 4; the electromagnetic wave with the polarization direction (here the horizontal polarization) conforming to the structure is received by the receiving patch and converted into an RF current signal, which is then collected into the central metal conducting via 4 through the middle narrow metal microstrip line; Figure 2 The right side shows the middle layer isolation metal ground plane 5 of the unit, which has a circular slot in the middle to allow the conducting via 4 to pass through, 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 FIG. 2. Figure 3 When the whole is a centrally placed square metal patch, and there are two cut corners in the main diagonal direction, to achieve 1-bit phase modulation, a'mouth' type slot is dug in the middle part of the square patch, and the small patch in the middle is connected with the outer ring patch through the PIN diode; the RF current signal flowing out of the conductive via 4 flows to the outer ring radiation patch through the conducting diode (here the unit works in state I, and the PIN diode is in the state of upper ON and lower OFF) after reaching the small patch in the middle, thereby generating left-handed circularly polarized electromagnetic wave radiation (it should be noted that the radiation patch in the oblique diagonal cut corner will produce right-handed circularly polarized electromagnetic wave radiation, which is not a restrictive requirement here); Figure 3 The right side is the equivalent passive structure of the state I unit; similarly, Figure 4 The unit configuration working in state II (i.e. the PIN diode is in the state of upper OFF and lower ON) is shown, and the corresponding passive structure is shown on the right side; by comparing the passive structures of the two working states of the unit, it is not difficult to find that the switching between the two states can be equivalent to a 180° physical rotation between the two.

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

[0066] For the bottom linearly polarized receiving patch, the transmission relationship can be represented as:

[0067]

[0068] It is shown that the receiving patch can be regarded as a polarizer, i.e. only allowing the reception and transmission of y-polarized electromagnetic wave.

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

[0070]

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

[0072]

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

[0074]

[0075] Similarly, when converted into right-handed circularly polarized wave, the corresponding Jones matrix and transformation process can be written as:

[0076]

[0077]

[0078] When a 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 The process of converting (0.7) into the corresponding circularly polarized radiation wave is calculated according to the above equation as:

[0080]

[0081] From the above deduced relationship, it can be seen that the rotation of the top layer of the 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-handed circularly polarized wave, and a phase shift of the same angle θ for the right-handed circularly polarized wave; this is obviously different from the Pancharatnam-Berry phase relationship in the conventional sense, which is twice the relationship with the rotation angle.

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

[0083] Figure 5 The amplitude response of the unit when it works in state I is given, and it can be seen that the main polarization of the unit is left-handed circularly polarized (LCP), and the cross-polarization is right-handed circularly polarized (RCP); Figure 6 The left side gives the phase of the main polarization LCP in state I and state II and the phase difference between the two, and the right side gives the phase of the cross-polarization RCP and the phase difference; obviously, although LCP and RCP have different phases, both states at all frequency points have a phase difference of 180°. The above results demonstrate the correctness of the theoretical derivation, and show that in the same array antenna (UEA) arranged uniformly, while the main polarization LCP is regulated, RCP will make a consistent response, that is, they have the same phase distribution; the specific performance is that the electromagnetic waves of the two polarizations will be superimposed in the same direction in the far field, and at the same time form two polarized beams, of course, the intensity is different according to the amplitude response of the unit.

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

[0085] In order to solve the above problems, the present application proposes a method for improving the bandwidth and efficiency of a 1bit circularly polarized transmissive array antenna, and two improved schemes of 1bit circularly polarized array antennas are obtained based on the method:

[0086] The first improved scheme: the radiation layer of the original 1bit reconfigurable transmissive unit is physically rotated by 90°, and the remaining part remains unchanged. The unit is placed orthogonally to the original unit. Figure 7 The structure diagrams of the two unit radiation layers are given, and the orientations of the integrated PIN diodes are represented by the letters 'V' and 'H' respectively; the 2x2 structure block is placed by cross arrangement of the original unit and the orthogonal unit, only the circularly polarized radiation layer is rotated by 90° to obtain the rotated orthogonal unit, and the bottom linearly polarized receiving patch of the 2x2 structure block remains uniformly arranged, thereby retaining the 1bit phase control capability of the original unit structure while introducing a 90° rotation phase shift. When the phases of the units in the array antenna are discretized, the phase distribution of the units in the subarray will meet the phase requirements of the main polarized beam as much as possible, and the 90° rotation phase shift of the orthogonal unit will disturb the phase distribution of the cross-polarized component, so that it cannot form a cross-polarized 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 The structure diagrams of the two unit radiation layers are given, and the orientations of the integrated PIN diodes are represented by the letters 'V' and 'H' respectively; the 2x2 structure block is placed by cross arrangement of the original unit and the orthogonal unit, only the circularly polarized radiation layer is rotated by 90° to obtain the rotated orthogonal unit, and the bottom linearly polarized receiving patch of the 2x2 structure block remains uniformly arranged, thereby retaining the 1bit phase control capability of the original unit structure while introducing a 90° rotation phase shift. When the phases of the units in the array antenna are discretized, the phase distribution of the units in the subarray will meet the phase requirements of the main polarized beam as much as possible, and the 90° rotation phase shift of the orthogonal unit will disturb the phase distribution of the cross-polarized component, so that it cannot form a cross-polarized beam in the same direction in the far field, thereby improving the cross-polarization ratio, reducing the axial ratio and improving the polarization purity.

[0087] The second improved scheme: the original 2x2 structure block is further improved to obtain a 4x4 structure block supercell. Specifically, on the basis of retaining the function of the original 2x2 structure block, the distribution of 'V' and 'H' units is adjusted. Specifically, the positions of 'V' units and 'H' units in the 2x2 structure block are exchanged to form another type of 2x2 permutation structure block. Further, the original structure block and the permutation structure block are placed by cross misplacement to form a 4x4 unit supercell. The radiation layer distribution pattern of the 4x4 unit supercell is approximately the order of 0°, 90°, 180° and 270° rotation of the four 2x2 structure blocks. Due to the orthogonal relationship of the 90° multiple rotation, the 4x4 structure block supercell does not change the relative positions of the existing units, i.e. only the original and orthogonal two types of unit structures are still present in the supercell. Similarly, the bottom linearly polarized receiving patch of the 4x4 structure block remains uniformly arranged. Figure 9 The structure diagrams of the two unit radiation layers are given, and the orientations of the integrated PIN diodes are represented by the letters 'V' and 'H' respectively; the 2x2 structure block is placed by cross arrangement of the original unit and the orthogonal unit, only the circularly polarized radiation layer is rotated by 90° to obtain the rotated orthogonal unit, and the bottom linearly polarized receiving patch of the 2x2 structure block remains uniformly arranged, thereby retaining the 1bit phase control capability of the original unit structure while introducing a 90° rotation phase shift. When the phases of the units in the array antenna are discretized, the phase distribution of the units in the subarray will meet the phase requirements of the main polarized beam as much as possible, and the 90° rotation phase shift of the orthogonal unit will disturb the phase distribution of the cross-polarized component, so that it cannot form a cross-polarized 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 9 The 2x2 structure block is distributed in a rotationally symmetric manner, and such a rotationally distributed structure not only further superimposes the main polarization component, but also further cancels the cross-polarization components in the subarray, thereby effectively eliminating the cross-polarization components from forming a superimposed interference main-polarization beam in the far field.

[0088] Figure 10 A structure diagram of a circularly polarized transmission array metasurface with a size of 16x16 is given, including a linearly polarized feed horn antenna and a bottom layer of uniformly arranged linearly polarized receiving patches. As a comparison, the application gives four different layout schemes of the radiation layer, which are a continuous phase array (CPA) with a continuously rotating phase modulation of the equivalent passive structure of the unit operating in state I, a 1-bit coded phase uniform element array (UEA) with a vertical unit in a unified layout, an orthogonal element array (OEA) with a 2x2 structure block as a basic component, and an orthogonal element array with rotation (OEAR) with a 4x4 structure block supercell as a basic component. The receiving patch layer in the above four arrays is replaced by a feed network, which constitutes a radiating metasurface composed of only a single layer of radiating patches, and the performance of the above transmission array antenna is analyzed and compared.

[0089] Figure 11 The continuous compensation phase of the directional beam of the continuous rotation array radiating in the direction and the rotation corresponding angle of the radiating patch distribution, the compensation phase can be calculated according to the following formula:

[0090]

[0091] wherein, λ is the wavelength corresponding to the working frequency of the antenna, (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 vertically placed feed antenna from the receiving layer of the transmission array plane, which is preferably 160mm, the focal ratio F / D of the feed and the array is preferably 0.667, wherein D is preferably the side length of the square reflector 240mm.

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

[0093]

[0094] For OEA and OEAR arrays, since two types of elements are placed in the array, they have four discrete phases of 0°, 90°, 180° and 270°, based on the additional 90° rotation phase shift of the two discrete phases of 0° and 180°. In addition, due to the relative fixation of the positions of the 'V' and 'H' elements, the phase discrete criterion is changed to:

[0095]

[0096] It should be noted that φ cont is the calculated continuous compensation phase, 'V' and 'H' represent vertical and horizontal elements respectively; State I is the discrete 0° and 270° phases of the two types of elements respectively, and State II is the discrete 180° and 90° phases of the two types of elements. The element distribution and the corresponding discrete phase distribution of the OEA and OEAR array antennas are shown in Figure 13 and Figure 14 respectively.

[0097] As a performance comparison, Figure 15The radiation patterns of the four types of transmitting array antennas with fixed transmitting beam direction are given, including co-polarization and cross-polarization transmission components. It can be seen that the continuous phase modulation array has very good main polarization beam pattern, and its direction coincides with the pre-set direction, and has good side lobe level and cross polarization level. The main beam gain is as high as 23.5dBi, the side lobe 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 reference of the discrete scheme. Consistent with the foregoing analysis, the radiation pattern of the UEA uniform array has main polarization and cross polarization beams in the set direction of 30°. 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 circular polarization beam, and it can be expected that the axial ratio of the beam will be relatively poor, which is obviously not suitable for the application of circular polarization antennas. For the OEA array with a 2x2 structure block subarray, the radiation pattern shows that the cross polarization component does not form effective superposition in the main beam direction to generate a beam, which fully demonstrates the effectiveness of the proposed scheme in disturbing the phase distribution of the cross polarization component. The main polarization beam also appears in the predetermined direction, and the beam gain is 19.9dBi. The co-polarization side lobe level is lower than -15dB. It should be noted that although the cross polarization component does not form superposition in the main beam direction, it appears in other directions with relatively high side lobes. 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 4x4 structure block OEAR array, the main polarization beam gain is as high as 21.2dBi, the co-polarization side lobe level is lower than -15dB, and the beam direction is in the predetermined direction. In addition, by observing the cross polarization component, it can be seen that it neither converges in the main beam direction nor has high stray side lobes in other directions, indicating that the cross polarization components in the subarray have been mutually cancelled, and cannot form superposition in the far field in any direction. The cross polarization side lobe level is lower than -18dB. Similarly, compared with the ideal continuous phase modulation array, the 4x4 structure block OEAR array achieves an approximate cross polarization component suppression level. This fully demonstrates the outstanding ability of the OEAR array to suppress the cross polarization component.

[0098] To further analyze the bandwidth performance of the array, Figure 16The gain curves of the four arrays in the main beam direction with frequency variation are respectively given, including the main polarization and cross polarization. By comparing with the ideal continuous phase modulation array, it can be found that the main polarization and cross polarization gain of the UEA uniform array shows consistent curves with the unit, which can be regarded as a simple superposition of the unit performance, and it is difficult to effectively suppress the undesired cross polarization component, indicating that the UEA array cannot be used as the design of the 1bit reconfigurable circular polarization scanning array antenna; it can be observed from the gain curve of the OEA array that although the cross polarization component is suppressed in some frequency bands, the cross polarization gain is still relatively high in other frequency bands, which is not conducive to the practical application of the 1bit reconfigurable circular polarization scanning array antenna; surprisingly, the OEAR array realizes the same cross polarization suppression level as the ideal continuous phase modulation array in the full frequency range of 8-12GHz, and the gain difference with the main polarization beam is below-15dB in a wide frequency band; combined with the beam axis ratio bandwidth shown in the figure, the beam axis ratio of the UEA and OEA arrays is only below 3dB in a narrow frequency range, compared with the 3dB axis ratio bandwidth of 19.5% of the ideal continuous phase modulation array, the OEAR array realizes a 3dB axis ratio bandwidth of up to 32.7%, that is, the beam axis ratio is below 3dB in the wideband range of 8.2-11.4GHz, which fully demonstrates that the 4x4 structure block in the OEAR array can effectively suppress the cross polarization component of the circular polarization in a wideband range. Figure 17

[0099] In addition, the aperture efficiency is also an important parameter for measuring the performance of the array antenna, Figure 18 The aperture efficiency corresponding to the main polarization gain of the four arrays in the main beam direction is given, and it can be seen that, compared with the ideal continuous phase modulation array, the OEAR scheme realizes an aperture efficiency of up to 21.6% at the center working frequency of 10GHz, which realizes a relatively high aperture efficiency for the 1bit discrete phase transmission array. The above performance fully demonstrates the excellent ability of the OEAR scheme in suppressing the cross polarization component in a wideband and further improving the energy convergence in the main polarization beam direction, which makes it widely applicable in the transmission array antenna with 1bit discrete coded phase, especially in the 1bit circular polarization electrically scanned array antenna integrated with adjustable devices, which can realize simple, wideband and high-performance circular polarization beam scanning.

[0100] The proposed OEA and OEAR arrays only use a single phase modulation functional layer, which not only solves the inherent defects of the traditional 1bit circular polarization array antenna, but also realizes simple and high-performance circular polarization beam radiation; the two schemes proposed in the application can be widely applied to circular polarization array antennas requiring a single phase modulation functional layer, such as circular polarization phased array antennas and radiating metasurfaces.

[0101] ​Compared with the prior art, the unit of the application is a radiation structure, and 1bit transmission phase control can be realized without rotation, and the purpose of adopting 90° rotation quadrature is to introduce additional rotation phase to disturb the distribution of the cross-polarization component phase of the circularly polarized wave, so that the cross-polarization components offset each other in the subarray of the structure block, thereby avoiding interference on the main polarized wave beam in the same direction. Therefore, the patent and the application have essential differences. In addition, the unit of the application directly controls the circularly polarized electromagnetic wave first, and does not require an additional reference phase setting; the 1bit phase characteristics of the unit itself can be equivalent to a physical rotation of 180°, and a physical rotation of 90° is additionally introduced, so that the rotation angle of the unit in the 2x2 structure block is not relatively fixed when the discrete phase is determined, and the closest phase rotation angle setting can be realized according to the beam requirement, thereby expanding the setting degree of freedom while retaining the advantages of the rotation array; in addition, the control of the circularly polarized wave in the application does not make a hard requirement on the reference phase, so that a trade-off and compromise between the beam polarization and the beam gain is not required; the reference phase can be additionally and independently set to take into account the polarization purity and the beam gain of the circularly polarized wave beam, which is particularly important for a large-angle circularly polarized wave beam scanning.

[0102] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. 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.) containing computer usable program codes. The solutions in the embodiments of the present application can be implemented in various computer languages, such as object-oriented programming languages Java and interpreted scripting language JavaScript.

[0103] The present application is described with reference to flowcharts and / or block diagrams according to the methods, devices (systems), and computer program products of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one flow or multiple flows and / or blocks Figure 1 The device that implements the functions specified in one flow or multiple flows and / or blocks.

[0104] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0105] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the Figure 1 function specified in the flow or flows and / or blocks Figure 1 of the block or blocks.

[0106] Although preferred embodiments of the application have been described herein, substitutions and alterations are possible in view of the disclosure of this application without departing from the spirit and scope of the present application. Therefore, it is intended that the appended claims be interpreted as including all such alternatives and modifications as fall within the true spirit and scope of the present application.

[0107] It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application cover modifications and variations of this application provided they come within the scope of the appended claims and their equivalents.

Claims

1. A method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmit array antenna, characterized in that, The method comprises the following steps: Constructing a 1bit circular polarization phase encoding transmission unit; wherein the RF current signal received by the inner circle of the radiation patch flows to the outer circle of the radiation patch according to the gating PIN diode and generates circularly polarized radiation, and the radiation patch has two encoding phase states of 0° and 180°; Without changing the rest of the structure of the 1bit circular polarization phase encoding transmission unit, rotating the radiation patch of the 1bit circular polarization phase encoding transmission unit by 90° to form a type of unit placed orthogonally to the radiation layer of the original transmission unit; placing the original unit and the orthogonal unit cross-located to form a 2*2 unit structure block; Swapping the positions of the original unit and the orthogonal unit in the 2*2 unit structure block to form another type of 2*2 permutation structure block; further cross-locating the original structure block and the permutation structure block to form a 4*4 unit supercell; the radiation layer distribution pattern of the 4*4 unit supercell is the order rotation of 0°, 90°, 180° and 270° of the four 2*2 structure blocks; the rest of the unit structure is the same arrangement; Taking the 4*4 unit supercell as the basic component, a 1bit circular polarization transmission array antenna is constructed; after receiving linearly polarized electromagnetic waves, each unit in the array takes the 4*4 unit supercell as the basic block, and the main polarization component of the circularly polarized electromagnetic waves radiated again in the basic block superimposes each other, and the cross-polarization component cancels each other in the basic block; the orthogonal placement of the radiation patch in the 4*4 unit supercell is equivalent to a non-dispersive rotation operation, which realizes cross-polarization suppression and main polarization superposition in a wide band, and further realizes a wideband and efficient radiation beam; The 1bit circular polarization phase encoding transmission unit comprises a linear polarization receiving patch, a metal ground plane, a radiation patch with 1bit phase control capability, and two layers of dielectric substrates; The linear polarization receiving patch and the circularly polarized wave radiation patch are respectively located on the two side layers of the transmission unit and are attached to the two layers of dielectric substrates; The linear polarization receiving patch is used for receiving linearly polarized electromagnetic waves in the polarization direction, converting them into RF current signals and conducting them to the inner circle of the radiation patch; the radiation patch flows the RF current signals to the outer circle of the radiation patch according to the gating PIN diode and generates circularly polarized radiation; The metal ground plane is located between the two layers of dielectric substrates and is used for isolating the linearly polarized wave receiving patch and the circularly polarized wave radiation patch; the metal ground plane is pre-pierced in the center to pass through the central metal through hole; The radiation patch integrates two PIN diodes, only one of which is conductive at the same time; according to the conduction state of the PIN diode, the radiation patch includes two working states, and the phase difference between the two working states of the radiation circularly polarized beam is 180°.

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

3. The method for improving the bandwidth and efficiency of a 1-bit circularly polarized transmit array antenna according to claim 1, wherein, The dielectric substrate is made of F4B material with a dielectric constant of 3.5 and a loss tangent of 0.0015, and the thickness is 1.524mm.

4. The method for improving 1-bit circularly polarized transmitarray antenna bandwidth and efficiency of claim 1, wherein, The linear polarization receiving patch is a rectangular metal patch placed along the horizontal direction, with a central metal conductive via arranged in the middle and a U-shaped slot arranged around the central metal conductive via; electromagnetic waves conforming to the structural polarization direction are received by the linear polarization receiving patch and converted into RF radio frequency current signals, and are collected into the central metal conductive via through the metal microstrip line in the middle, and then pass through the circular slot in the metal ground plane to reach the radiation patch.

5. The method for improving 1-bit circularly polarized transmitarray bandwidth and efficiency according to claim 1, wherein, The radiation patch is a square metal patch placed in the center, with two cut corners in the main diagonal direction, a mouth-shaped slot is arranged in the middle part of the square patch, and the inner ring patch is connected with the outer ring patch through two PIN diodes; the RF radio frequency current signals flowing out of the central metal conductive via flow to the outer ring patch through the conducting PIN diode after reaching the inner ring patch, to generate left-handed circularly polarized electromagnetic wave radiation.

6. The method for improving 1-bit circularly polarized transmitarray bandwidth and efficiency according to claim 1, wherein, The 1-bit circularly polarized transmit array antenna continuously rotates the array radiation pointing direction The continuous compensation phase of the directional beam in the direction and the compensation phase of the radiation patch distribution corresponding to the rotation angle are: Wherein, λ is the wavelength corresponding to the working frequency of the antenna, (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 normally placed vertical feed source antenna from the receiving layer of the transmission array plane, and φ0 is the reference phase.

7. The method for improving 1-bit circularly polarized transmitarray antenna bandwidth and efficiency of claim 1, wherein, The 1bit circularly polarized transmission array antenna phase discretization criterion is: where φ cont is the calculated continuous compensation phase, 'V' and 'H' represent vertical and horizontal cells, respectively; State I is the 0° and 270° phase obtained from the two types of cells, respectively, and State II is the 180° and 90° phase obtained from the two types of cells, respectively.

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