Variable capacitance diode-based adjustable beam control method for element grating leaky-wave antenna

Abstract

The invention discloses a variable capacitance diode-based element grating leaky-wave antenna adjustable beam control method. The method comprises the following steps of S1, researching and analyzing a super grating beam conversion mechanism; a plane super grating mechanism under anisotropic, uniform and continuous periodic boundary conditions is researched; s2, carrying out the transmission mode and optimization design of the Floquet-Blocch theorem according to the super grating; the FB mode is researched, and a tool used for super grating parameters is designed to eliminate the bad FB mode; s3, analyzing and designing the super grating leaky-wave antenna; the analytic field and current of the synthetic super grating are researched in the leaky-wave antenna frame to customize the performance in the aspects of phase, beam shape and polarization; s4, designing and analyzing the electric tuning wave beam control super grating leaky-wave antenna; according to the variable capacitance diode-based element grating leaky-wave antenna adjustable wave beam control method, a high-efficiency structure platform which is tuned by a tunable material with a simple structure is adopted, and a road is laid for a new generation of high-efficiency special grating.

Description

Technical Field

[0001] The invention relates to the field of grating technology, and in particular to an adjustable beam control method of a meta-grating leaky wave antenna based on a varactor diode. Background Art

[0002] In the past few years, metagratings (also known as metasurfaces), as two-dimensional arrays composed of densely distributed polarizable particles, have made unprecedented progress in optical flow control, leading to their application in multiple research and technology fields such as energy harvesting, imaging and stealth. Metagratings are an important class of engineered surfaces that are widely used to redirect the reflection and transmission directions of incident waves. These metagratings are carefully designed to provide gradient surface impedance to achieve the required local momentum, thereby guiding the incident wave to the desired direction. Although these gratings have achieved unprecedented capabilities in controlling electromagnetic waves, recent independent studies have demonstrated that gradient metagratings designed based on generalized laws of reflection and refraction have fundamental physical limitations in their conversion efficiency, provided that they are assumed to be local and passive. Notably, studies have shown that active or strongly non-local metagratings are required to achieve unit efficiency in redirecting incident or excitation waves to the desired direction during reflection or transmission. In addition, since gradient metagratings need to provide carefully designed and rapidly changing gradient grating impedance characteristics, they require high-resolution discretization, which complicates their manufacturing process.

[0003] Therefore, the basic design approach followed by most reports is to try to establish effective coupling to the desired FB mode by choosing a period that allows only a few propagating modes to exist and applying some heuristics or numerical optimization to a single period to reduce coupling to all modes except the prescribed mode. One of the basic functions used to measure the capabilities of a metasurface (MTS) is anomalous refraction, where a given incident plane wave is deflected to a desired angle during transmission. Summary of the invention

[0004] The purpose of the present invention is to provide a variable capacitance diode based meta-grating leaky wave antenna adjustable beam control method, using a simple structure of tunable materials for tuning the efficient structural platform, paving the way for a new generation of efficient special gratings.

[0005] The present invention provides a variable capacitance diode based meta-grating leaky wave antenna adjustable beam control method, comprising the following steps:

[0006] S1. Research and analyze the supergrating beam switching mechanism;

[0007] Study the planar supergrating mechanism under anisotropic, uniform, and continuous periodic boundary conditions;

[0008] The scalar electrical impedance density and magnetic admittance density that constitute the supergrating are studied, and the performance of the electrical impedance density and magnetic admittance density as a function of load impedance and operating frequency is examined;

[0009] Research on the conversion of surface wave to propagation wave method for various physical quantities of supermagnetic field;

[0010] S2, transmission mode and optimization design based on Floquet-Bloch theorem of supergrating;

[0011] Study FB modes and eliminate undesirable FB modes by designing a tool for supergrating parameters;

[0012] Through local matching between the surface wave interaction with the periodic supergrating and an infinite uniform periodic structure with the same amplitude and period, the number of propagating FB modes is matched to the number of different supergratings in the periodic structure.

[0013] S3. Analyze and design supergrating leaky wave antenna;

[0014] Study the resolved fields and currents of synthetic supergratings in the framework of leaky-wave antennas to tailor the performance in terms of phase, beam shape, and polarization. Study the design considerations of supergrating leaky-wave antennas, focusing on characterizing the impedance characteristics of the supergrating and describing the required feeding system.

[0015] S4. Design and analysis of electrically tunable beam steering supergrating leaky wave antennas;

[0016] Establish an analytical model of the wide-angle supergrating beam radiation field and conduct in-depth research;

[0017] Study beam control methods; control the phase of leaky wave antennas to achieve electronic scanning; change the phase of supergratings to control the radiation direction.

[0018] Preferably, in step S1, the supergrating is divided into two modeling modes through anisotropic continuous impedance, and the two modeling modes are opaque supergrating or transparent supergrating;

[0019] A specific grating pattern is constructed in the TE or transverse magnetic TM mode through a supergrating. Each conductor constituting the supergrating is represented by a scalar electrical impedance density, and for the conductor with magnetic response, it is represented by a scalar magnetic admittance density.

[0020] Preferably, in step S2, the FB mode is a mode with a negative index, which is n=-1, and its phase modulus is smaller than the wave number of free space. In addition, the mode of n=-1 contributes to the far-field radiation pattern. The FB mode of n=-1 is matched with the target aperture distribution to determine the periodic parameters of the supergrating.

[0021] Preferably, a dielectric layer or supergrating will be located above the ground plane, wherein the dielectric layer is characterized by dielectric constant and thickness, and the supergrating will be composed of metal strips or metal grooves with determined width and periodicity due to the reactance resolution closure.

[0022] Preferably, beam scanning is achieved by adjusting the supergrating elements without the need for complex and lossy beam forming networks.

[0023] Therefore, the present invention adopts the above-mentioned variable capacitance diode-based meta-grating leaky wave antenna adjustable beam control method, and uses a simple structure tunable material for tuning an efficient structural platform, paving the way for a new generation of efficient special gratings.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the adjustable beam control method of the meta-grating leaky wave antenna based on varactor diode of the present invention;

[0026] Figure 2 A schematic diagram of a supergrating leaky wave antenna of the present invention for an adjustable beam control method of a metagrating leaky wave antenna based on a varactor diode;

[0027] Figure 3 A schematic diagram of a varactor diode of the method for adjustable beam control of a meta-grating leaky wave antenna based on a varactor diode of the present invention;

[0028] Figure 4 A schematic diagram of the radiation angle in the supergrating leaky wave antenna of the method for adjustable beam control of the metagrating leaky wave antenna based on varactor diode of the present invention;

[0029] Figure 5 The present invention is a schematic diagram of an equivalent impedance matching circuit of a unit cell of a supergrating leaky wave antenna according to an adjustable beam control method of a metagrating leaky wave antenna based on a varactor diode. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0031] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0032] The words "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprises" and similar terms mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0033] Embodiment 1

[0034] like Figure 1 As shown, the adjustable beam control method of the meta-grating leaky wave antenna based on the varactor diode of the present invention comprises the following steps:

[0035] S1. Research and analyze the supergrating beam switching mechanism;

[0036] The mechanism of planar supergrating under anisotropic, uniform, and continuous periodic boundary conditions is studied; the geometric shape and material parameters of arbitrary unit structures can be conveniently processed by periodic boundaries, and the size of the supergrating can be greatly reduced. The supergrating can be accurately characterized based on the uniform equivalent surface impedance.

[0037] When the surface impedance is uniform, the anisotropic field and tangential field of the surface must satisfy anisotropic boundary conditions. Therefore, a practical solution is to use small metal elements (about λ / 10) printed on the dielectric plate to achieve anisotropic boundary conditions, thereby giving them a preferred direction. For example, the elements can have a shape divided by small gaps. When the small cuts are neither parallel nor orthogonal to the radial direction, the boundary conditions become anisotropic.

[0038] The scalar electrical impedance density and magnetic admittance density that constitute the supergrating are studied, and the performance of the electrical impedance density and magnetic admittance density as a function of load impedance and operating frequency is examined;

[0039] The supergrating is divided into two modeling methods through anisotropic continuous impedance, and the two modeling methods are opaque supergrating or transparent supergrating;

[0040] A supergrating can be modeled in two different ways by anisotropic continuous impedances, which we refer to as opaque supergratings or transparent supergratings. In the first case, the supergrating is represented as a tensor opaque reactance (X_op) that relates the average tangential electric field (Et) and magnetic field (Ht) at the interface on the supergrating as follows

[0041]

[0042] where the symbol represents the limit of z approaching 0 from above, z is perpendicular to the supergrating, and the time-harmonic relationship exp(jωt) is assumed to exist, which is omitted. The opaque reaction resistance X_op is a function of the frequency and the surface wave vector Kt. On the other hand, anisotropic transparent supergratings can be defined using the transparent reaction resistance X_ as follows:

[0043]

[0044] where J is the average current flowing in the transparent reactance and, in this case, kt depends on the non-negligible opaque impedance since it includes the electrical impedance of the short-circuited transmission line included in the network formalism. Figure 3 A tunable element grating leaky-wave antenna using a varactor diode is shown. Input parameters include the aperture field, frequency, substrate properties, and the aperture size used to set the initial value.

[0045] A specific grating pattern is constructed in TE or transverse magnetic TM mode through a supergrating. Each wire constituting the supergrating is represented by a scalar electrical impedance density, and for wires with magnetic response, it is represented by a scalar magnetic admittance density.

[0046] S1.3. Research on the surface wave to propagation wave method conversion of various physical quantities of supermagnetic fields; propose an alternative practical design of a converter based on supergrating, which realizes the engineering transmission of propagating plane waves by separating incident plane waves and surface waves of the same polarization in different half-spaces. This demonstrates the practical implementation of a converter based on a conventional printed circuit board and confirms its high efficiency through full-wave three-dimensional simulation. In addition, the impedance matrix of the converter based on supergrating will be derived. Through this two-dimensional full-wave numerical simulation method, the theoretical findings will be verified and a practically implementable supergrating topology will be proposed.

[0047] S2, transmission mode and optimization design based on Floquet-Bloch theorem of supergrating;

[0048] Study all FB modes and eliminate undesirable FB modes by designing a tool for supergrating parameters;

[0049] The FB expansion can be applied to the problem of plane wavefront propagation on a periodic impedance supergrating. This problem is posed for the case of surface waves propagating on an impedance surface with a scalar impedance supergrating. The fields and currents are well approximated as those of a local plane wavefront on an infinite homogeneous medium, with amplitude and period matching the local problem. Furthermore, the spectral GF function is evaluated at each local FB wavenumber by the same local plane approximation, which provides an additional equation for the associated fields and currents. Thus, a local dispersion equation is established, which once solved yields the local value of the complex wavenumber of the surface wave on the supergrating.

[0050] The design tool for the metagrating will give uniform periodic parameters (i.e., phase and amplitude) to the tensor reactance sheet so that the radiating aperture field matches the target aperture field. To achieve this goal, we will identify FB modes that can distinguish between radiating modes or non-radiating modes. Radiating FB modes are modes with negative index, usually n=-1, whose phase modulus is less than the wave number in free space. In addition, the n=-1 mode has a dominant contribution to the far-field radiation pattern. Therefore, by matching the n=-1 FB mode to the target aperture distribution, the periodic parameters of the metagrating can be determined. The phase of the metagrating determines the phase of the radiated field. The depth of the metagrating controls the amplitude of the aperture field and the amount of energy converted from surface waves to leaky waves. The polarization of the aperture field is controlled by the relative phase between the inputs to the tensor metagrating.

[0051] Through local matching between the surface wave interaction with the periodic supergrating and an infinite uniform periodic structure with the same amplitude and period, the number of propagating FB modes is matched to the number of different supergratings in the periodic structure.

[0052] The FB wave expansion is introduced for modeling and designing supergrating antennas fed by microstrip surface waves, which implement a periodic impedance surface. The adiabatic expansion of the FB wave arises from the local match between the problem of the interaction of the microstrip surface wave with the periodic supergrating and the problem of a plane wavefront on an infinite uniform period with the same amplitude and period. This model is the basis for building a design tool for supergrating antennas with ideal radiation performance. The exact solution exists in space as a single propagation is a non-uniform plane wave. Under this assumption, the required local power balance can be exactly achieved by a system consisting of only one surface bound mode and one propagating plane wave. The infinite region is lossless, and by operating as an ideal leaky wave antenna, only emitting a plane wave in a given direction, without storing any reactive energy in higher-order FB modes, the conversion efficiency is theoretically expected to be ideal and reaches almost 100% in numerical tests, as a reference solution for periodic supergrating impedance leaky wave antennas, taking into account the radiation of partially transparent walls.

[0053] S3. Analyze and design supergrating leaky wave antenna;

[0054] The resolved fields and currents of synthetic supergratings are studied in the framework of leaky-wave antennas to tailor the performance in terms of phase, beam shape and polarization;

[0055] An analytical solution is proposed to predict the beam pointing angles achieved by phased supergratings in such leaky-wave antennas. The primary goal is to extend the synthesis of multiple supergrating fed antennas to shaped beams. The solution is based on a synthesis technique that relies on the direct inversion of the electric field integral equation (EFIE) after expanding the surface currents and sheet impedances in terms of Fourier-Bessel basis functions (FBBFs). Proper phasing of the feed allows continuous beam pointing over an angular range equal to the 3 dB beamwidth.

[0056] The design considerations of supergrating leaky-wave antennas are studied, with a focus on characterizing the impedance characteristics of the supergrating and describing the required feeding system to ensure the correct excitation of the surface waves while controlling the leakage of the total field.

[0057] The radiation fields in the far field will be studied by means of an equivalent supergrating leaky wave antenna. These patterns can be obtained by applying a rigorous spectral Green's function method for the fundamental sources in the E and H planes at the center frequency. In fact, for dielectric materials, the presence of this mode leads to the appearance of a sidelobe in the direction close to the Brewster angle. For supergratings based on capacitive slot grids, this peak effect can also be observed, but at a slightly larger angle. For supergratings based on inductive strip grids, the peak disappears and the directivity is improved. Compared with dielectric solutions, such as Figure 5 As shown in Figure 1, the supergrating MG antenna is a versatile planar antenna that can achieve beamforming and pattern control through periodic boundary conditions while keeping the antenna structure unchanged. This feature makes it suitable for dynamic supergrating. It can be applied to any unit structure, regardless of its complexity, and can take into account all difficult-to-calculate scattered fields, achieve high directivity and reduce beamwidth angles through radiating grating elements.

[0058] S4. Design and analysis of electrically tunable beam steering supergrating leaky wave antennas;

[0059] An analytical model of the wide-angle supergrating beam radiation field is established and studied in depth; a new configuration of a periodic supergrating for beam control in a supergrating leaky wave antenna controls the radiation phase by changing the inductor / capacitor (LC) element, thereby controlling the pointing angle of the radiation beam. Several prototypes will be designed and made for operation at X-band frequencies. Each grating has an input impedance that can be adjusted by carefully adjusting the element spacing and geometric dimensions to achieve a wide range of controllable phases in the z direction. All gratings are connected to a feed port with a 50Ω input impedance. The far-field radiation pattern measurements of the fabricated prototypes are in good agreement with the simulation results and show a wide beam control range of nearly 120°.

[0060] Study beam steering methods; control the phase of leaky wave antennas to achieve electronic scanning;

[0061] Control the phase of the leaky wave antenna to achieve electronic scanning. A prototype of a fixed-frequency electronically scanned supergrating leaky wave antenna is proposed. The construction of this antenna is based on the concept of supergrating. By adding an adjustable substrate, continuous beam scanning at a fixed frequency can be achieved, thereby providing a wide range of scanning angles. These angles can be controlled by applying a bias voltage while maintaining a constant characteristic impedance to achieve good matching. In addition, the antenna uses microstrip technology, and the low-profile characteristics make the proposed antenna easier to manufacture and more suitable for integration into microwave or millimeter wave systems.

[0062] The phase of the supergrating is changed (-90°<θ<90°) to control the radiation direction.

[0063] In particular, beam scanning can be achieved by tuning the metagrating elements without the need for complex and lossy beam forming networks. Instead of achieving beam scanning by controlling the dielectric substrate material, the subwavelength size of the unit cell can be used to control the equivalent impedance (or equivalently, to control the properties of the scattering element). Different tuning methods and various technical solutions can be used to achieve beam scanning. Two possible methods for beam scanning: global control for one-dimensional scanning or two-dimensional scanning. Designs related to the implementation of tuning the metagrating in the first method using varactor diodes are proposed here.

[0064] Therefore, the present invention adopts the above-mentioned variable capacitance diode-based meta-grating leaky wave antenna adjustable beam control method, and uses a simple structure tunable material for tuning an efficient structural platform, paving the way for a new generation of efficient special gratings.

[0065] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for adjustable beam control of a meta-grating leaky wave antenna based on a varactor diode, characterized in that: The following steps are involved: S1. Research and analyze the supergrating beam switching mechanism; Study the planar supergrating mechanism under anisotropic, uniform, and continuous periodic boundary conditions; The scalar electrical impedance density and magnetic admittance density that constitute the supergrating are studied, and the performance of the electrical impedance density and magnetic admittance density as a function of load impedance and operating frequency is examined; Research on the conversion of surface wave to propagation wave method for various physical quantities of supermagnetic field; S2, transmission mode and optimization design based on Floquet-Bloch theorem of supergrating; Study FB modes and eliminate undesirable FB modes by designing a tool for supergrating parameters; Through local matching between the surface wave interaction with the periodic supergrating and an infinite uniform periodic structure with the same amplitude and period, the number of propagating FB modes is matched to the number of different supergratings in the periodic structure. S3. Analyze and design supergrating leaky wave antenna; Study the analytical fields and currents of synthetic supergratings in the framework of leaky-wave antennas to tailor performance in terms of phase, beam shape, and polarization. Study the design considerations of supergrating leaky-wave antennas, focusing on characterizing the impedance characteristics of the supergrating and describing the required feeding system. S4. Design and analysis of electrically tunable beam steering supergrating leaky wave antennas; Establish an analytical model of the wide-angle supergrating beam radiation field and conduct in-depth research; Study beam control methods; control the phase of leaky wave antennas to achieve electronic scanning; change the phase of supergratings to control the radiation direction.

2. The adjustable beam control method of the meta-grating leaky wave antenna based on varactor diode according to claim 1 is characterized in that: In step S1, the supergrating is divided into two modeling modes through anisotropic continuous impedance, and the two modeling modes are opaque supergrating or transparent supergrating; A specific grating pattern is constructed in the TE or transverse magnetic TM mode through a supergrating. Each conductor constituting the supergrating is represented by a scalar electrical impedance density, and for the conductor with magnetic response, it is represented by a scalar magnetic admittance density.

3. The adjustable beam control method of the meta-grating leaky wave antenna based on varactor diode according to claim 1, characterized in that: In step S2, the FB mode is a mode with a negative index, which is n=-1, and its phase modulus is smaller than the wave number of free space. In addition, the mode of n=-1 contributes to the far-field radiation pattern. The FB mode of n=-1 is matched with the target aperture distribution to determine the periodic parameters of the supergrating.

4. The adjustable beam control method of the meta-grating leaky wave antenna based on varactor diode according to claim 1, characterized in that: A dielectric layer or supergrating will be located above the ground plane, where the dielectric layer is characterized by dielectric constant and thickness, and the supergrating will consist of metal strips or grooves with determined width and periodicity due to the reactance resolution closure.

5. The adjustable beam control method of the meta-grating leaky wave antenna based on varactor diode according to claim 1, characterized in that: Beam scanning is achieved by adjusting the supergrating elements without the need for complex and lossy beamforming networks.

Images