Broadband dual-circular-polarization reconfigurable conformal antenna and design method thereof

Abstract

The invention discloses a broadband dual-circular-polarization reconfigurable conformal antenna and a design method thereof, and relates to the technical field of radiation antenna elements, and the antenna comprises a substrate, a radiation assembly, a ground plane, and a feed port. Wherein the radiation assembly comprises a cross dipole and four parasitic patches above the ground plane, two adjacent arms of the cross dipole are connected with the inner conductor of the coaxial feed port, and other arms are connected with the ground plane through short circuit pins. The four PIN diodes are integrated on the four arms of the cross dipole, the element can flexibly switch the polarization state between two orthogonal CP modes, and the conformal ground is loaded below the polarization reconfigurable conformal radiation element, so that unidirectional radiation is realized. Meanwhile, the four fan-shaped parasitic patches arranged in the four quadrants of the dipole are used for expanding the working bandwidth.

Description

Technical Field

[0001] The invention relates to the technical field of radiating antenna elements, and in particular to a broadband dual circular polarization reconfigurable conformal antenna and a design method thereof. Background Art

[0002] With the rapid development of wearable electronic devices, wireless body area network (WBAN) is considered to be a promising technology in various fields such as military, medical, and disaster relief. As a crucial component in the WBAN system, conformal wearable antennas are very attractive due to their small size, strong portability, and easy operation. In typical emergency rescue scenarios (such as Figure 1 A high-speed, stable, and reliable communication network between rescue workers is essential to ensure disaster control and their own safety.

[0003] However, strict communication requirements and advertising channel conditions pose great challenges to the design of conformal wearable antennas. First, the antenna's beam coverage should be as large as possible, because rescuers may include ground personnel and aerial drones in different positions. Second, because the carrier of the wearable antenna (i.e., the human body) is affected by various posture changes, its movement affects the circular polarization (CP) radiation capability. Therefore, the wearable antenna design requires a unidirectional radiating element with a high front-to-back ratio.

[0004] Therefore, we propose a broadband dual circularly polarized reconfigurable conformal antenna and its design method to solve the above problems.

[0005] The above information disclosed in this background technology is only used to increase the understanding of the background technology of the present invention and therefore, it may include information that does not constitute the prior art known to ordinary technicians in this field. Summary of the invention

[0006] The purpose of the present invention is to provide a broadband dual circularly polarized reconfigurable conformal antenna and a design method thereof, so as to solve the problems in the wearable antenna design proposed in the above background technology, such as human body influence, large beam coverage, circularly polarized radiation and broadband working bandwidth, which are currently on the market.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A broadband dual circular polarization reconfigurable conformal antenna, comprising a substrate, a radiation component, a ground plane, and a feeding port;

[0009] The radiation component includes a cross dipole composed of two arms of different lengths and four parasitic patches above the ground plane. Two adjacent arms of the cross dipole are connected to the inner conductor of the coaxial feeding port, and the other arms are connected to the ground plane through a short-circuit pin. At the same time, the short-circuit pin can also be used to ground the two PIN (D1, D2) tubes connected to it.

[0010] As a further optimization scheme of the present invention, the cross dipole includes four arms, each of which is composed of two microstrip lines with lengths and widths Ld1, Wd1 and Ld2, Wd2 respectively, connected in series through a PIN tube. At the end of each arm, a patch inductor is used in series with a DC bias point to conduct the DC signal required to control the PIN tube switch and prevent the AC signal on the radiation patch from flowing into the DC bias point.

[0011] As a further optimization solution of the present invention, the ground plane is located below the radiation component at a wavelength corresponding to one quarter of the center frequency.

[0012] As a further optimization solution of the present invention, the substrate is an arched cylinder, wherein the curvature K is 12.5 and the material is ABS plastic.

[0013] As a further optimization solution of the present invention, four PIN diodes are respectively integrated on the four arms of the cross dipole, and the two CP modes of LHCP and RHCP are switched by controlling the on and off states of the PIN diodes.

[0014] As a further optimization solution of the present invention, the parasitic patch is fan-shaped, and four parasitic patches are symmetrically arranged in four quadrants of the cross dipole, and the parasitic patch and the cross dipole are coupled to each other;

[0015] A copper short-circuit pin is provided on one of the fan-shaped parasitic elements, and the lower end of the short-circuit pin is connected to the ground. Two chip inductors are provided between the two right-angled sides of the fan-shaped parasitic element with the short-circuit pin and the two arms connected to the coaxial inner conductor, which are used to ground the PIN (D3, D4) tubes on the two arms and isolate the AC signals on the arms.

[0016] As a further optimization scheme of the present invention, the conformal radiating antenna element has an operating frequency range of 2.24-3.42 GHz, a reflection coefficient of less than -10 dB, and an axial specific bandwidth of greater than 29.6%.

[0017] A design method for a broadband dual circular polarization reconfigurable conformal antenna is applicable to the broadband dual circular polarization reconfigurable conformal antenna as described above, and specifically comprises the following steps:

[0018] S1. Design a pair of crossed dipoles with different arm lengths on the ground plane, where two adjacent arms of one crossed dipole are connected to the inner conductor of the coaxial feeding port, and the other arms are connected to the ground plane through short-circuit pins;

[0019] S2, four PIN diodes are integrated on the four arms of the cross dipole, and the on and off states of the PIN diodes are flexibly controlled by changing the DC bias voltage, so that the cross dipole can switch the polarization state between two orthogonal CP modes;

[0020] S3, four fan-shaped parasitic patches are arranged on the four quadrants of the cross dipole to expand the working bandwidth;

[0021] S4. Design an additional short-circuit pin to connect the adjacent harmonics to the ground plane to reduce the parasitic inductance brought by a single short-circuit pin.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention designs a broadband and polarization reconfigurable conformal radiating element, integrating a single-feed reconfigurable cross dipole and parasitic patches above the ground plane to achieve unidirectional radiation. By integrating four PIN diodes on the four arms of the cross dipole, the element can flexibly switch the polarization state between two orthogonal CP modes. Four fan-shaped parasitic patches placed in the four quadrants of the dipole help to expand the working bandwidth.

[0024] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of WBAN application of a hemispherical wearable array antenna based on a helmet in a typical forest fire emergency rescue scenario in the prior art;

[0026] Figure 2 The working principle and evolution diagram of the broadband dual-CPs reconfigurable conformal radiating element in the present invention, wherein (a) is a unidirectional cross-dipole antenna; (b) is a broadband unidirectional antenna; (c) is a broadband unidirectional dual-CPs reconfigurable antenna;

[0027] Figure 3 Graphs showing the changes of (a) |S11| and (b) AR with frequency simulated in the present invention, where Ant.1, Ant.2 and Ant.3 are respectively;

[0028] Figure 4 The geometric structure diagram of the broadband dual CPs reconfigurable conformal radiating element of the present invention is shown in FIG. 1 , wherein (a) is a three-dimensional view; (b) is a top view; (c) is a side view;

[0029] Figure 5 (a) is an equivalent circuit diagram of a PIN diode operating in the on and off states in the present invention; (b) is a reconfigurable LHCP and (c) RHCP diagram of a conformal radiating element;

[0030] Figure 6 When the conformal radiating element in the first example of the present invention works in the LHCP mode at a frequency of 2.4 GHz, the simulated surface current distribution diagrams on (a) the cross dipole and (b) the parasitic patch;

[0031] Figure 7 Graph showing how the simulated reflection coefficient and AR of the conformal radiating element vary with frequency under (a) different Rp and (b) different rL conditions in Verification Example 2 of the present invention;

[0032] Figure 8 The simulated reflection coefficient, AR and xz plane radiation pattern (3 GHz) diagram of the conformal radiating element with different K in the second verification example of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] A broadband dual circular polarization reconfigurable conformal antenna, comprising a substrate, a radiation component, a ground plane, and a feeding port;

[0035] The radiation component includes a cross dipole consisting of two arms with different arm lengths and four parasitic patches above the ground plane. Two adjacent arms of the cross dipole are connected to the inner conductor of the coaxial feeding port, and the other arms are connected to the ground plane through short-circuit pins.

[0036] Design a pair of crossed dipoles with different arm lengths on a finite ground plane. The initial design is named Ant. Figure 2 As shown in (a), two adjacent arms of the cross dipole are connected to the inner conductor of the coaxial feeding port, and the other arm is connected to the ground plane through a short-circuit pin.

[0037] According to the transmission 4-wire theory, the dipole of Ant.1 has inductive impedance, while the shorter dipole has capacitive impedance. By adjusting the length difference between the two dipoles, surface currents with a phase difference of 90° are generated on the two dipoles. Therefore, Ant.1 can generate CP unidirectional radiation. However, due to the presence of the ground plane close to the crossed dipoles, the impedance bandwidth (IMBW) or axial ratio bandwidth (ARBW) of unit 1 is very narrow, such as Figure 3 shown.

[0038] Placing four sector-shaped patches as parasitic elements in the four quadrants of the crossed dipole turns unit 1 into unit 2. 1 turns into Ant.2. Figure 3 It can be seen that Ant.2 is significantly larger than Unit 1. Ant.1. To achieve reconfigurable dual-CPs radiation capability, Unit 2 further evolved into Unit 1. To achieve reconfigurable dual-CPs radiation capability, Ant 2 further evolved into Ant 3.

[0039] Ant.3, integrates four PIN diodes at appropriate positions of the four arms. By flexibly configuring the on and off states of the PIN diodes, two effective radiation apertures similar to Ant.2 are created to achieve low radiation. By flexibly configuring the on and off states of the PIN diodes, two effective radiation apertures similar to Ant.2 are created to achieve LHCP and RHCP radiation respectively, and their exchanged longer and shorter dipoles are taken into account.

[0040] like Figure 4 As shown in (a), a broadband dual circular polarization reconfigurable conformal antenna is mainly composed of a substrate, a radiating component, a ground plane, and a feeding port. The radiating element is consistent with the hemispherical helmet, and an arched cylinder with a curvature K and a height Hs is designed as the substrate. The substrate material is acrylonitrile butadiene styrene (ABS) plastic with a dielectric constant of 3.2, light weight, and easy to shape.

[0041] The conformal radiator located on the top layer of the substrate consists of crossed dipoles and parasitic patches.

[0042] Compared with the feeding part of Ant.3, an additional short-circuit pin is used to connect the adjacent harmonics to the ground plane, thereby effectively reducing the parasitic inductance caused by a single short-circuit pin. Four BAR64-02V PIN diodes (i.e., D1, D2, D3, and D4) are placed at Ld1 away from the open ends of the double arms. The DC bias point of the PIN diode is located near the ends of the open arms, and RF isolation is achieved by connecting a 37-nH inductor.

[0043] A short-circuit pin with a radius of Rs is used to connect a parasitic patch and the ground plane to achieve DC bias grounding. Figure 4 As shown in (a), the positive terminal of D1 and the negative terminal of D2 are directly grounded through the short-circuit pin, while D3 and D4 are DC-grounded through a short-circuit pin and two inductors that bridge a pair of adjacent arms and a parasitic patch.

[0044] Table I shows the configuration of the PIN diodes in all operating states of the conformal antenna element.

[0045] Figure 5 (a) describes the equivalent circuit model of the PIN diode in the off and on states. Figure 5 (b) and Figure 5 As shown in (c), by applying the same positive DC voltage to the four bias points, the antenna can operate in mode 1 (LHCP mode); by applying a negative DC voltage, the antenna can operate in mode 2 (RHCP mode). Regardless of whether the DC is grounded or not, since the same DC voltage is applied to the four bias points, only one bias line is required.

[0046] Verification example 1: Verify the surface current distribution on the conformal radiating element.

[0047] like Figure 6 As shown in (a), when the antenna operates in LHCP mode, the surface current sum vector of both the cross dipole and the parasitic patch rotates clockwise within a cycle. Since the short-circuit pin connecting the ground wire and the parasitic patch is located at a quarter wavelength of the edge of the parasitic patch, the position of the short-circuit pin is equivalent to an actual short-circuit point, so it has little interference with the current pattern on the conformal antenna.

[0048]

[0049] Table 1 Pin diode configuration of conformal antenna element in all working states

[0050] Verification Example 2: Verify the influence of Rp, rL=Ld2 / Ld1 and K on the radiation performance of conformal radiating elements.

[0051] like Figure 7 As shown in (a), the operating frequency decreases with the increase of Rp due to the extension of the current path on the parasitic patch. In addition, the change of rL value will also cause the curve of reflection coefficient S11 to change with frequency [see Figure 7 (b)].

[0052] Specifically, as the length difference between the long dipole and the short dipole decreases (i.e., the rL value increases), the double resonance peak tends to disappear. In addition, increasing the curvature K will reduce the operating frequency band [see Figure 8 (a)] from Figure 7 and Figure 8 (a) It can be seen that AR is more sensitive to the changes of geometric parameters than S11. Figure 8 (b) shows the xz plane radiation pattern at 3 GHz, indicating that the greater the curvature, the smaller the gain and the wider the beamwidth. The curvature K was finally selected as 12.5, and Rp and rL were optimized to 19.5 mm and 0.67, respectively. The simulated -10-dB impedance bandwidth and 3-dB AR bandwidth of the conformal radiating element are 2.24-3.42 GHz and 2.5-3.45 GHz, respectively.

[0053] A design method for a broadband dual circular polarization reconfigurable conformal antenna is applicable to the broadband dual circular polarization reconfigurable conformal antenna described above, and specifically comprises the following steps:

[0054] S1. Design a pair of crossed dipoles with different arm lengths on the ground plane, where two adjacent arms of one crossed dipole are connected to the inner conductor of the coaxial feeding port, and the other arms are connected to the ground plane through short-circuit pins;

[0055] S2, four PIN diodes are integrated on the four arms of the cross dipole, and the on and off states of the PIN diodes are flexibly controlled by changing the DC bias voltage, so that the cross dipole can switch the polarization state between two orthogonal CP modes;

[0056] S3. Four fan-shaped parasitic patches are arranged on the four quadrants of the cross dipole to expand the working bandwidth; the radiating element is designed to have a curvature consistent with that of the hemispherical helmet, and an arched cylinder with a curvature K and a height Hs is used as a substrate, and the substrate material is acrylonitrile butadiene styrene (ABS) plastic;

[0057] S4. Design an additional short-circuit pin to connect the adjacent harmonics to the ground plane to reduce the parasitic inductance brought by a single short-circuit pin.

[0058] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A broadband dual circular polarization reconfigurable conformal antenna, characterized in that: Includes substrate, radiating components, ground plane, and feed port; The radiation component includes a cross dipole and four parasitic patches above a ground plane, two adjacent arms of the cross dipole are connected to an inner conductor of a coaxial feeding port, and other arms are connected to the ground plane through a short-circuit pin.

2. The broadband dual circular polarization reconfigurable conformal antenna according to claim 1, characterized in that: The crossed dipole includes four arms, each of which is composed of two microstrip lines of different lengths and widths connected in series through a PIN tube. At the end of each arm, a patch inductor is used in series with a DC bias point to conduct the DC signal required to control the PIN tube switch and prevent the AC signal on the radiation patch from flowing into the DC bias point.

3. The broadband dual circular polarization reconfigurable conformal antenna according to claim 1, characterized in that: The ground plane is located below the radiating components.

4. The broadband dual circular polarization reconfigurable conformal antenna according to claim 1, characterized in that: The substrate is an arched cylinder, wherein the curvature K is 12.5 and the material is ABS plastic.

5. The broadband dual circular polarization reconfigurable conformal antenna according to claim 1, characterized in that: Four PIN diodes are respectively integrated on the four arms of the cross dipole, and the radiating element can work in two CP modes, LHCP and RHCP, by controlling the on and off states of the PIN diodes.

6. The broadband dual circular polarization reconfigurable conformal antenna according to claim 1, characterized in that: The parasitic patch is fan-shaped, and four parasitic patches are symmetrically arranged in four quadrants of the cross dipole, and the parasitic patch and the cross dipole are coupled to each other; A copper short-circuit pin is provided on one of the fan-shaped parasitic elements, and the lower end of the short-circuit pin is connected to the ground. Two chip inductors are provided between the two right-angled sides of the fan-shaped parasitic element with the short-circuit pin and the two arms connected to the coaxial inner conductor, which are used to ground the PIN (D3, D4) tubes on the two arms and isolate the AC signals on the arms.

7. The broadband dual circular polarization reconfigurable conformal antenna according to claim 1, characterized in that: The conformal radiating antenna element has an operating frequency range of 2.24-3.42 GHz, an axial specific bandwidth greater than 29.6%, a maximum gain of 5.58 dBi, and a maximum 3dB beam width of 98°.

8. A design method for a broadband dual circularly polarized reconfigurable conformal antenna, characterized in that: The method is applicable to the broadband dual circular polarization reconfigurable conformal antenna as claimed in any one of claims 1 to 7, and specifically comprises the following steps: S1. Design a pair of crossed dipoles with different arm lengths on the ground plane, where two adjacent arms of one crossed dipole are connected to the inner conductor of the coaxial feeding port, and the other arms are connected to the ground plane through short-circuit pins; S2, four PIN diodes are integrated on the four arms of the cross dipole, and the on and off states of the PIN diodes are flexibly controlled by changing the DC bias voltage, so that the cross dipole can switch the polarization state between two orthogonal CP modes; S3, four fan-shaped parasitic patches are arranged on the four quadrants of the cross dipole to expand the working bandwidth; S4. Design an additional short-circuit pin to connect the adjacent harmonics to the ground plane to reduce the parasitic inductance brought by a single short-circuit pin.

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