A broadband dual-circularly-polarized reconfigurable conformal antenna and a design method thereof

Abstract

The application discloses a broadband dual-circularly-polarized reconfigurable conformal antenna and a design method thereof, relates to the technical field of radiating antenna elements, and comprises a substrate, a radiating assembly, a ground plane and a feeding port; wherein the radiating assembly comprises four parasitic patches above the cross-dipole and the ground plane, two adjacent arms of the cross-dipole are connected with an inner conductor of the coaxial feeding port, and the other arms are connected with the ground plane through short-circuit pins. 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, a conformal ground plane is loaded below the polarization-reconfigurable conformal radiating element to realize unidirectional radiation. Meanwhile, the four fan-shaped parasitic patches arranged in four quadrants of the dipole are used for expanding the working bandwidth.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radiation antenna elements, in particular to a wideband dual circularly polarized reconfigurable conformal antenna and a design method thereof. BACKGROUND

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

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

[0004] Therefore, we propose a wideband dual circularly polarized reconfigurable conformal antenna and a design method thereof to solve the problems raised in the above background.

[0005] The above information disclosed in this BACKGROUND section is only for increasing the understanding of the background of the application, therefore, it can include information known by those of ordinary skill in the art. SUMMARY

[0006] The purpose of the present application is to provide a wideband dual circularly polarized reconfigurable conformal antenna and a design method thereof to solve the problems of wearable antenna design that need to solve the problems of human body influence, large beam coverage, circularly polarized radiation and wideband working bandwidth in the current market raised in the above background.

[0007] To achieve the above purpose, the present application provides the following technical solutions:

[0008] A wideband dual circularly polarized reconfigurable conformal antenna, comprising a substrate, a radiation assembly, a ground plane and a feed port;

[0009] The radiation assembly includes a cross-dipole composed of two 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 feed 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 for grounding the two PIN (D1, D2) tubes connected thereto.

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

[0011] As a further optimization scheme of the present application, the ground plane is located below the radiation assembly at a wavelength corresponding to the quarter center frequency point.

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

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

[0014] As a further optimization scheme of the present application, the parasitic patch is a fan shape, and four parasitic patches are symmetrically arranged in the four quadrants of the cross-dipole, and the parasitic patches and the cross-dipole are coupled with each other.

[0015] A copper shorting pin is arranged on one of the fan-shaped parasitic elements, the lower end of the shorting pin is connected to the ground, and two patch inductors are arranged between the two straight edges of the fan-shaped parasitic element provided with the shorting pin and the two arms connected to the inner conductor of the coaxial feeder, which are used to ground the PIN (D3, D4) tubes on the two arms while isolating the AC signals on the arms.

[0016] As a further optimization scheme of the present application, the operating frequency range of the conformal radiation antenna element is 2.24-3.42 GHz, the reflection coefficient is less than -10 dB, and the axial ratio bandwidth is greater than 29.6%.

[0017] A design method of a wideband dual circularly polarized reconfigurable conformal antenna, which is suitable for the wideband dual circularly polarized reconfigurable conformal antenna as described above, specifically includes the following steps:

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

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

[0020] S3. Set four fan-shaped parasitic patches 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] This invention designs a broadband and polarization-reconfigurable conformal radiating element. It integrates a single-feed reconfigurable cross-dipole and parasitic patches above the ground plane to achieve unidirectional radiation. By integrating four PIN diodes in the four arms of the cross-dipole, the element can flexibly switch its polarization state between two orthogonal CP modes. Four sector-shaped parasitic patches placed in the four quadrants of the dipole help expand the operating 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 a 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 of the present invention, where (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 how (a) |S11| and (b) AR vary with frequency, simulated in the present invention, where Ant.1, Ant.2, and Ant.3 are shown respectively;

[0028] Figure 4 The geometric structure diagram of the broadband dual-CPs reconfigurable conformal radiating element of the present invention: (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; (b) is a reconfigurable LHCP and (c) RHCP diagram of a conformal radiating element in the present invention;

[0030] Figure 6 Figures 6a and 6b show the simulated surface current distributions on the cross-dipole and parasitic patches, respectively, for the conformal radiating element in Example 1 of the present disclosure operating in LHCP mode at 2.4 GHz frequency;

[0031] Figure 7 Figures 7a and 7b show the simulated reflection coefficient and AR, respectively, as a function of frequency for the conformal radiating element in Example 2 of the present disclosure under (a) different Rp and (b) different rL conditions;

[0032] Figure 8 Figures 8a, 8b and 8c show the simulated reflection coefficient, AR and xz-plane radiation pattern (3 GHz), respectively, for the conformal radiating element in Example 2 of the present disclosure with different K. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present disclosure will be apparently and completely described below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present disclosure.

[0034] A broadband dual-circularly polarized reconfigurable conformal antenna, comprising a substrate, a radiating assembly, a ground plane, a feed port;

[0035] The radiating assembly comprises a cross-dipole composed of two 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 feed port, and the other arms are connected to the ground plane through shorting pins.

[0036] A pair of cross-dipoles with different arm lengths is designed on a finite ground plane. The initial design is named Ant.1 as shown in Figure 2 (a), two adjacent arms of the cross-dipole are connected to the inner conductor of the coaxial feed port, and the other arms are connected to the ground plane through shorting pins.

[0037] According to the transmission 4-line theory, the dipole of Ant.1 has inductive impedance, while the shorter dipole has capacitive impedance. Adjusting the length difference between the two dipoles generates a phase difference of 90° surface current on the two dipoles. Therefore, Ant.1 can generate CP unidirectional radiation. However, due to the existence of the ground plane close to the cross-dipole, the impedance bandwidth (IMBW) or axial ratio bandwidth (ARBW) of Ant.1 is very narrow, as shown in Figure 3 .

[0038] Four fan-shaped patches are placed as parasitic elements in the four quadrants of the cross-dipole to make Ant. 1 become Ant. 2. As can be seen from Fig. 3, Ant. 2 is superior to Ant. 1. Ant. 1 is further evolved into Ant. 2 to realize the reconfigurable dual-CP radiation capability. To realize the reconfigurable dual-CP radiation capability, Ant. 2 is further developed into Ant. 3.

[0039] Ant. 3, four PIN diodes are integrated 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 realize 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 realize LHCP and RHCP radiation, respectively, and the longer and shorter dipoles of their exchange are considered.

[0040] As shown in Fig. 4(a), a broadband dual-circularly polarized reconfigurable conformal antenna mainly consists of a substrate, a radiation component, a ground plane, and a feed port. The radiation element is consistent with the hemispherical helmet, and a curved cylindrical body with a curvature of K and a height of Hs is designed as the substrate. The substrate material is acrylonitrile-butadiene-styrene (ABS) plastic with a dielectric constant of 3.2, which is light in weight and easy to shape.

[0041] The conformal radiator located at the top layer of the substrate consists of a cross-dipole and a parasitic patch.

[0042] Compared with the feed part of Ant. 3, an additional short pin is used to connect the adjacent harmonic to the ground plane, thereby effectively reducing the parasitic inductance brought by a single short 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, respectively. The DC bias point of the PIN diode is located near the open ends of the arms, and RF isolation is achieved by connecting a 37-nH inductor.

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

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

[0045] Figure 5(a) describes the equivalent circuit model of the PIN diode in off and on states. As shown in Figures 5(b) and 5(c), the antenna can work in mode 1 (LHCP mode) by applying a same positive DC voltage at the four bias points, and in mode 2 (RHCP mode) by applying a negative DC voltage. Regardless of DC grounding, only one bias line is needed since the same DC voltage is applied at the four bias points.

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

[0047] As shown in Figure 6(a), when the antenna works in the LHCP mode, the sum vector of the surface currents on the cross-dipole and the parasitic patch will rotate clockwise in one period. Since the shorting pin connecting the ground wire and the parasitic patch is located at the edge quarter wavelength of the parasitic patch, the position of the shorting pin is equivalent to an actual shorting point, thus causing little disturbance to the current mode on the conformal antenna.

[0048]

[0049] Table 1 Configuration of the pin diode in all working states of the conformal antenna element

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

[0051] As shown in Figure 7(a), the working frequency decreases with the increase of Rp due to the lengthening of the current path on the parasitic patch. In addition, the change of the rL value will also cause the curve of the reflection coefficient S11 varying with the frequency to change [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 peaks tend to disappear. In addition, increasing the curvature K will reduce the working frequency band [see Figure 8(a)]. As can be seen from Figures 7 and 8(a), compared with S11, AR is more sensitive to the change of the geometric parameters. Figure 8(b) shows the xz-plane radiation mode at a frequency of 3 GHz, indicating that the greater the curvature, the smaller the gain and the wider the beam width. Finally, the curvature K is selected as 12.5, and Rp and rL are optimized as 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 circularly polarized reconfigurable conformal antenna is applicable to the broadband dual circularly polarized reconfigurable conformal antenna described above, and specifically includes the following steps:

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

[0055] S2. Four PIN diodes are integrated on the four arms of the cross dipole. The on and off states of the PIN diodes can be flexibly controlled by changing the DC bias voltage, enabling the cross dipole to switch its polarization state between two orthogonal CP modes.

[0056] S3. Four fan-shaped parasitic patches are placed on the four quadrants of the crossed dipole to expand the operating bandwidth. The radiating element is designed to have a curvature consistent with the hemispherical helmet. An arched cylinder with a curvature K and a height Hs is used as the substrate. 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 will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A broadband dual circularly polarized reconfigurable conformal antenna, characterized in that: Including substrate, radiating components, ground plane, and feed port; The radiating component includes a cross dipole and four parasitic patches above the ground plane. Two adjacent arms of the cross dipole are connected to the inner conductor of the coaxial feed port, and the other arms are connected to the ground plane through short-circuit pins. The cross dipole consists of four arms, each of which is composed of two microstrip lines of different lengths and widths connected in series through a PIN transistor. At the end of each arm, a patch inductor is connected in series with a DC bias point to conduct the DC signal required to control the PIN transistor switch and prevent the AC signal on the radiating patch from flowing into the DC bias point. 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.

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

3. The broadband dual circularly polarized reconfigurable conformal antenna according to claim 1, wherein: The substrate is an arched cylinder with a curvature K of 12.5 and is made of ABS plastic.

4. The broadband dual circularly polarized reconfigurable conformal antenna according to claim 1, wherein: Four PIN diodes are integrated on the four arms of the cross dipole respectively. By controlling the on and off states of the PIN diodes, the radiating element can operate in two CP modes, LHCP and RHCP.

5. The broadband dual circularly polarized reconfigurable conformal antenna according to claim 1, wherein: The conformal radiating antenna element operates in the frequency range of 2.24-3.42 GHz, with an axial specific bandwidth greater than 29.6%, a maximum gain of 5.58dBi, and a maximum 3dB beamwidth of 98°.

6. A design method for a broadband dual circularly polarized reconfigurable conformal antenna, characterized in that: The method is applicable to the broadband dual circularly polarized reconfigurable conformal antenna according to any one of claims 1 to 5, and specifically comprises the following steps: S1. Design a pair of crossed dipoles with different arm lengths on the ground plane. The two adjacent arms of one crossed dipole are connected to the inner conductor of the coaxial feed port, and the other arm is connected to the ground plane through a short-circuit pin. S2. Four PIN diodes are integrated on the four arms of the cross dipole. The on and off states of the PIN diodes can be flexibly controlled by changing the DC bias voltage, enabling the cross dipole to switch its polarization state between two orthogonal CP modes. S3. Set four fan-shaped parasitic patches 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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