Low-profile portable dual-band Beidou navigation antenna

Abstract

The invention provides a low-profile portable dual-band Beidou navigation antenna, and belongs to the technical field of antennas. Comprising an upper-layer radiation sheet, a dielectric substrate, a lower-layer main radiation sheet, a coupling short-circuit branch knot and a feed probe, the dielectric substrate adopts a single-layer structure, the lower part of the dielectric substrate is hollowed out to form a cavity, the lower-layer main radiation sheet is covered in the cavity, and the coupling short-circuit branch comprises a coupling branch embedded in a rectangular groove of the lower-layer main radiation sheet, a short-circuit branch connected with the coupling branch and an extension branch connected with the short-circuit branch; the upper radiation sheet covers the upper layer of the dielectric substrate; and the feed probe and the lower-layer main radiation sheet perform coupling feed, and penetrate through the dielectric substrate and the upper-layer radiation sheet to perform direct feed. On one hand, the weight of the antenna is reduced, on the other hand, good matching and circular polarization performance are achieved in the B1 / B3 frequency band through dual-frequency feed and four-probe phase regulation and control, and the antenna can be applied to portable Beidou navigation terminal equipment sensitive to the size and the weight.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a low-profile, lightweight, dual-band Beidou navigation antenna. Background Art

[0002] The widespread adoption of the Beidou navigation system in vehicles, drones, and portable devices has placed higher demands on miniaturization, low profile, and lightweight navigation antennas. Traditional dual-band Beidou antennas typically utilize stacked patches or four-arm helical structures. These antennas are bulky (e.g., height >10mm) and heavy (due to the inherent weight of traditional ceramic materials), making them difficult to meet the demands of modern devices for thinness, lightness, and high integration. Furthermore, existing antennas often face performance bottlenecks such as narrow bandwidth and poor axial ratio when operating at low profiles.

[0003] There are two main technical methods for achieving miniaturization: one is to use high dielectric constant materials as dielectric substrates. Although this can reduce the overall size of the antenna, the overall height and weight of the antenna are still high. For example, the existing articles disclose the use of dielectric constant ε r =9.8 and ε r =45 ceramic material to achieve antenna miniaturization. The antenna diameter is 26.6mm, but the total cross-section height reaches 12mm due to the stacking method, and the double-layer dielectric substrate and ceramic material lead to a large weight. Secondly, the use of short-circuit branch technology can effectively reduce the overall size of the antenna, but the short-circuit branches and coupling branches introduced and added still occupy a large cross-sectional space, increasing the antenna cross-sectional size to 60×60mm. 2 , the overall size is still large and is not suitable for application in truly miniaturized terminal equipment.

[0004] Therefore, it is of great practical significance to provide a dual-band Beidou navigation antenna that can achieve good performance of dual-frequency matching and low axial ratio while ensuring low profile and lightweight. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a low-profile lightweight dual-band Beidou navigation antenna. The present invention provides an overall size of 30×30×6mm. 3 The dual-band Beidou navigation antenna with a low profile of 6mm uses PPO material to reduce weight. Through dual-frequency feeding and four-probe phase control, it achieves good matching and circular polarization performance in the B1 / B3 frequency bands. It can be used in portable Beidou navigation terminal devices that are sensitive to size and weight.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A low-profile, lightweight, dual-band Beidou navigation antenna comprises an upper radiating plate, a dielectric substrate, a lower main radiating plate, a coupling short-circuit branch, and a feeding probe. The dielectric substrate adopts a single-layer structure with a cavity hollowed out below. The lower main radiating plate is covered in the cavity. The coupling short-circuit branches include coupling branches embedded in rectangular slots of the lower main radiating plate, short-circuit branches connected to the coupling branches, and extended branches connected to the short-circuit branches. The upper radiating plate is covered on the upper layer of the dielectric substrate. The feeding probe is coupled and fed with the lower main radiating plate, and is directly fed through the dielectric substrate and the upper radiating plate.

[0008] Preferably, the overall size of the antenna is 30×30×6 mm 3 , using ppo material as the dielectric substrate, the dielectric constant ε r =11, the hollow space size of the cavity is 28×28×4mm 3 , the antenna side wall thickness is 1mm.

[0009] Preferably, rectangular grooves of equal area are opened from the four edges of the lower main radiation piece toward the center point, and the coupling branches in the coupling short-circuit branches are completely embedded in the rectangular grooves of the lower main radiation piece, with a gap left between them.

[0010] Preferably, one end of the short-circuit branch is connected to the coupling branch, and is used to control the resonant frequency by adjusting the length of the extended branch; the other end extends along the inner wall of the dielectric substrate to the metal ground, and is used to change the current path and reduce the size of the antenna.

[0011] Preferably, the feeding probes are provided with four vertical feeding points at symmetrical positions along the center point of the antenna, the probes are spatially rotationally symmetrically distributed, and the phases of the excitation signals differ by 90°.

[0012] Preferably, four circular holes are opened on the lower main radiating plate, and the feeding probe is coupled and fed through the circular holes, so that the lower main radiating plate operates in the B3I frequency band.

[0013] Preferably, the upper radiation piece directly operates in the B1I frequency band through a feeding probe, and the size of the upper radiation piece is adjustable to control the resonant frequency of the B1I frequency band. The quadrilateral rectangular slots and coupling branches of the lower main radiation piece serve as the radiation body of the B1I frequency band.

[0014] Preferably, the upper radiation piece changes the electromagnetic coupling strength with the lower main radiation piece by adjusting its own size. When the size of the upper radiation piece increases, the binding effect on the lower high-frequency current is enhanced, so that the resonant frequency is reduced; when the size of the upper radiation piece decreases, the electromagnetic coupling is weakened, so that the resonant frequency is increased, thereby realizing the secondary radiation of the energy of the upper radiation piece to the lower main radiation piece.

[0015] Preferably, the coupled short-circuit branch forms an LC resonant circuit with the lower main radiation plate, and a parallel inductance effect is introduced through the short-circuit structure to shorten the current path and reduce the equivalent electrical size of the antenna.

[0016] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0017] (1) The present invention forms a cavity structure by hollowing out the bottom of a single-layer dielectric substrate and adopts PPO material (dielectric constant ε r =11) as the dielectric substrate, reducing the overall size of the antenna to 30×30×6mm 3 , with a cross-sectional height of only 6mm; compared with traditional stacked patch antennas, the antenna provided by the present invention has a reduced height and a significantly reduced weight, meeting the demand for lightweight and thinness of portable devices.

[0018] (2) The present invention utilizes the coupled short-circuit branches and the rectangular slots of the lower main radiating plate to form an LC resonant circuit. The short-circuit structure introduces a parallel inductance effect, shortens the current path, reduces the antenna's equivalent electrical dimensions, and achieves antenna miniaturization. Furthermore, the introduction of two layers of metal radiating plates, operating in dual frequency bands, and a four-probe feed design with phases differing by 90° enable the antenna to achieve circular polarization performance in both frequency bands, with an in-band right-hand circular polarization axial ratio AR < 3dB, ensuring stable signal reception in high dynamic environments.

[0019] (3) The present invention controls the B1 band resonant frequency by adjusting the size of the upper radiation plate. The four-sided rectangular slots and coupling branches of the lower main radiation plate serve as the B1 band radiation body. The cavity structure and the extended branches are combined to adjust the B3 band resonant frequency, thereby realizing independent control of the dual-bands and solving the problem of frequency interference of traditional dual-band antennas. The present invention can be applied to portable Beidou navigation terminal devices that are sensitive to volume and weight, including but not limited to: shared bicycle smart locks, handheld locators, small drones and other fields that require lightweight and low-power navigation solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a schematic diagram of the structure provided by Example 1 of the present invention; wherein, Figure 1 (a) is a schematic diagram of the overall structure. Figure 1 (b) is a schematic diagram of the internal structure of the dielectric substrate;

[0022] Figure 2 This is a diagram showing the current distribution of the dual-band Beidou navigation antenna at different operating frequencies provided by Example 1 of the present invention; wherein, Figure 2 (a) is the surface current distribution diagram of the dual-band Beidou navigation antenna at 1.268 GHz, i.e., the B3I frequency band. Figure 2 (b) shows the surface current distribution of the dual-band BeiDou navigation antenna at 1.561 GHz, i.e., the B1I band.

[0023] Figure 3 The S11 curve diagram provided in Example 1 of the present invention;

[0024] Figure 4 A graph showing gain versus frequency variation provided in Example 1 of the present invention;

[0025] Figure 5 The center frequency pattern provided in Example 1 of the present invention;

[0026] Figure 6 A curve diagram showing the change of axial ratio with frequency provided in Example 1 of the present invention;

[0027] Figure 7 This is a diagram showing the center frequency axial ratio changing with angle provided in Example 1 of the present invention.

[0028] Description of reference numerals:

[0029] 1. Upper radiation plate; 2. Dielectric substrate; 3. Lower main radiation plate; 4. Coupling branch; 5. Short-circuit branch; 6. Extension branch; 7. Feed probe; 8. Circular hole; 9. Rectangular slot. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] like Figure 1 As shown, the present invention provides a low-profile lightweight dual-band Beidou navigation antenna, which uses a cavity structure and a short-circuit coupling branch 4 to achieve miniaturization of the antenna, making the overall size of the antenna only 30×30×6mm 3(0.127λ0*0.127λ0*0.025λ0, λ0 is the wavelength of 1.268GHz operating frequency), which can work in BeiDou B1I and B31 frequency bands. At the same time, the dual-band BeiDou navigation antenna provided by the present invention uses ppo material as the dielectric substrate 2, with a dielectric constant of ε r =11, with the characteristics of miniaturization, low profile and low axis ratio, it meets the requirements of thinness and is suitable for applications in terminal equipment such as drones and shared bicycles.

[0034] Specifically, refer to Figure 1 In (a) and (b), the dual-band Beidou navigation antenna includes an upper radiating plate 1, a dielectric substrate 2, a lower main radiating plate 3, a coupling short-circuit branch 5, and a feeding probe 7; the dielectric substrate 2 adopts a single-layer structure for achieving dual-band operation, and a cavity is hollowed out below it. The hollow space size of the cavity is 28×28×4mm 3 The thickness of the antenna side wall is 1mm, and the weight of the antenna is significantly reduced by hollowing out a large area. The lower main radiating plate 3 is covered in the cavity; the upper radiating plate 1 is covered on the upper layer of the dielectric substrate 2, and the feeding probe 7 is coupled and fed between the lower main radiating plate 3, and directly fed through the dielectric substrate 2 and the upper radiating plate 1. The upper and lower layers share a set of feeding probes 7. The lower main radiating plate 3 works in the B3I frequency band and uses a coupled feeding method; the upper radiating plate 1 works in the B1I frequency band and uses a probe direct feeding method. Four vertical probe feeding points are set at symmetrical positions along the center point of the antenna, and each probe is rotationally symmetrically distributed in space; through the control of the feeding network, the phases of the excitation signals of the four probes are made to differ by 90° (i.e. 0°, 90°, 180°, 270°) in sequence, thereby exciting equal amplitude and orthogonal phase signals on the upper and lower radiating plates to achieve the circular polarization performance of the antenna.

[0035] Furthermore, the coupling short-circuit branch 5 includes a coupling branch 4 embedded in the rectangular slot 9 of the lower main radiating plate 3, a short-circuit branch 5 connected to the coupling branch 4, and an extension branch 6 connected to the short-circuit branch 5. The short-circuit branch 5 is connected to the metal ground along the inner wall of the dielectric substrate 2, and the extension branch 6 is provided on the side of the short-circuit branch 5. The resonant frequency is controlled by adjusting the length of the extension branch 6. The coupling short-circuit branch 5 forms an LC resonant circuit with the lower main radiating plate 3. The short-circuit structure introduces a parallel inductance effect, shortening the current path and reducing the antenna's equivalent electrical size.

[0036] The upper radiation piece 1 changes the electromagnetic coupling strength with the lower main radiation piece 3 by adjusting its own size. When the size of the upper radiation piece 1 increases, the binding effect on the lower high-frequency current is enhanced, and the resonant frequency is reduced; when the size of the upper radiation piece 1 decreases, the electromagnetic coupling is weakened, and the resonant frequency is increased, thereby realizing the secondary radiation of the energy of the upper radiation piece 1 to the lower main radiation piece 3.

[0037] Based on the above, the dual-band operating principle of this dual-band Beidou navigation antenna is described. When operating in the B3I band, the dual-band Beidou navigation antenna operates as follows: the lower main radiator 3, coupling branch 4, short-circuit branch 5, and extension branch 6 combine to simultaneously operate in the B3I band. The lower main radiator 3 has a side length of 28 mm, the same as the side length of the cavity cross-section, and is located close to the top of the cavity, operating in the Beidou B3I band. Rectangular slots 9 of equal area are provided along the four edges of the lower main radiator 3 toward the center point. This allows for coupling with the short-circuit branch 5 without increasing the cross-sectional area. Coupling branches 4, each smaller than the rectangular slot 9, are added to each of the rectangular slots 9. A gap is left between the coupling branch 4 and the rectangular slot 9 to achieve coupling. The coupling branch 4 is connected to the short-circuit branch 5 to form a short-circuit structure.

[0038] The short-circuit branch 5 extends downward along the inner wall of the dielectric substrate 2 and is connected to the metal ground. This part belongs to the feed network and is not marked in the figure. The short-circuit structure directly connects the antenna radiating plate to the ground plate by introducing a short-circuit wall, forming a parallel inductance effect. This structure changes the current distribution of the radiating plate, forcing the current path to be extended, thereby reducing the equivalent electrical size of the antenna, significantly reducing the physical size while keeping the resonant frequency unchanged. At the same time, the short-circuit branch 5 and the capacitive reactance of the radiating plate form an LC resonant circuit, optimizing impedance matching and maintaining radiation efficiency while achieving miniaturization. Its principle is to shorten the wavelength by controlling the current path and achieve a size-performance balance by reconstructing the electromagnetic field.

[0039] Extension branches 6 are introduced to the sides of the short-circuit branches 5. Simulations show that the longer the extension branches 6, the lower the resonant frequency. By adjusting the length of the extension branches 6, the resonant frequency can be precisely controlled. The coupling branches 4 are embedded in the rectangular slots 9 of the lower main radiating plate 3. The short-circuit branches 5 and the extension branches 6 are closely attached to the inner wall of the antenna, significantly reducing the cross-sectional space and making the antenna more compact. This frequency band uses a coupled feed method. Four circular holes 8 are drilled in the lower main radiating plate 3, through which the feed probe 7 is fed for coupled feeding.

[0040] Reference Figure 2 In figure (a), when the antenna operates in the B3I frequency band (i.e., 1268 MHz), electromagnetic signals at a specific frequency excite the current, resulting in a current distribution strongly associated with the lower main radiator 3 and the coupled short-circuit branch 5. As shown in the current distribution at 1.268 GHz (i.e., 1268 MHz), under the 1268 MHz signal drive, the current is primarily concentrated in the lower main radiator 3, with a significant current path forming near the coupled short-circuit branch 5.

[0041] Specifically, the lower main radiating plate 3 and the coupled short-circuit branch 5 form an LC resonant circuit. The rectangular slot 9 and the gap between the coupled short-circuit branch 4 form a capacitive effect. The short-circuit branch 5 is connected to the metal ground along the inner wall of the dielectric substrate 2, introducing a parallel inductance effect. The two work together to shorten the current path, allowing the current corresponding to the 1268MHz signal to be concentrated on the lower main radiating plate 3 and the coupled short-circuit branch 5, thereby achieving effective resonance and radiation in this frequency band. This current distribution pattern intuitively confirms the design logic of the B3I band, which relies on the "lower main radiating plate 3 + coupled short-circuit branch 5" to build LC resonance and shorten the current path to ensure stable transmission and reception of 1268MHz signals, ensuring that the antenna can operate reliably in the B3I frequency band (1268MHz).

[0042] The dual-band BeiDou navigation antenna operates in the B1I band as follows: the high-frequency resonance is controlled by adjusting the size of the upper radiation plate 1, and the rectangular slots 9 and coupling branches 4 of the lower main radiation plate 3 serve as the main radiation body. These structures serve as the main high-frequency radiation body, and the current is mainly concentrated in the lower slots and coupling branches 4. Figure 2 (b) The red highlighted portion. Adjusting the size of the upper radiator 1 changes the strength of its electromagnetic coupling with the underlying structure. Increasing the size of the upper radiator 1 enhances the confinement of the high-frequency current in the lower layer, lowering the resonant frequency. Conversely, reducing the size weakens the coupling and increases the frequency. This coordinated mechanism of upper-layer regulation and lower-layer radiation maintains the optimal distribution of high-frequency current while achieving precise frequency control through simple size adjustments. When the upper radiator 1 is 28×28 mm, the coupling with the underlying structure is strongest, with a resonant frequency of approximately 1561 MHz.

[0043] Based on the above content, the dual-band Beidou navigation antenna provided by the present invention realizes the independent control of Beidou dual-frequency signals by hollowing out the dielectric substrate 2 and embedding the upper and lower layers of radiators. At the same time, the present invention uses the size of the top adjustable radiator to accurately control the high-frequency resonant frequency (1561MHz), and realizes secondary radiation coupling through the lower layer gap branches; the bottom layer short-circuit branches 5 independently control the low-frequency resonance (1268MHz). In addition, the two layers of radiators interact with each other through electromagnetic induction, the upper layer specifically processes the 1561MHz signal, and the lower layer is responsible for the 1268MHz signal, and they do not interfere with each other. The antenna uses a combination of a cavity structure and a coupled short-circuit branch 5 to reduce the antenna cross-sectional height to 6mm. This structure not only maintains the light and thin characteristics of the antenna, but also ensures the stable reception of dual-band signals. It is particularly suitable for use in navigation equipment with strict requirements on volume and weight.

[0044] Reference Figure 3The antenna S11 curve loss curve shows that the minimum return loss in the B3 band (1.268GHz) and the B1 band (1.561GHz) is less than -17dB, indicating that the antenna achieves excellent impedance matching characteristics in both bands. This is due to the LC resonant circuit formed by the lower main radiating plate 3 and the coupling short-circuit branch 5, and the optimization of the electromagnetic coupling strength by adjusting the size of the upper radiating plate 1, which ensures efficient energy transmission between the feed probe 7 and the radiating plate. Figure 4 In the B3 band (1.268 GHz), the right-hand circularly polarized peak gain exceeds 3 dBic, while in the B1 band (1.561 GHz), the peak gain exceeds 4 dBic. This gain performance relies on the synergistic effect of the two-layer radiator: the lower main radiator 3 and the coupled short-circuit branch 5 form a highly efficient radiating unit in the B3 band. The upper radiator 1, through size adjustment, controls the resonant frequency in the B1 band and reradiates energy to the lower layer, maintaining high radiation efficiency in both bands.

[0045] In addition, if Figure 5 As shown in Figure 1, the center frequency radiation patterns of the B3 and B1 bands exhibit good upward radiation capabilities, with the main radiation energy concentrated above the horizontal plane. Its radiation performance meets the technical requirements of modern satellite navigation systems for circularly polarized radiation. Figure 6 As shown in the figure, the axial ratio (AR) in both B3 and B1 bands is less than 3dB, and the AR in both bands is less than 1dB, indicating that the antenna has achieved excellent circular polarization performance in both bands. Figure 7 It shows that at the center frequency, the angle range in which the axial ratio of the B3 and B1 bands is less than 3dB exceeds 120°, among which the axial ratio of the B1 band in the range of θ=0°~150° is less than 2.5dB, which further proves that the present invention has excellent circularly polarized radiation characteristics.

[0046] Therefore, using the above-mentioned low-profile lightweight dual-band Beidou navigation antenna, the present invention provides a 30×30×6mm overall size. 3 The dual-band Beidou navigation antenna with a low profile of 6mm uses PPO material to reduce weight. Through dual-frequency feeding and four-probe phase control, it achieves good matching and circular polarization performance in the B1 / B3 frequency bands. It can be used in portable Beidou navigation terminal devices that are sensitive to size and weight.

[0047] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A low-profile, lightweight dual-band Beidou navigation antenna, characterized in that: It includes an upper radiation plate, a dielectric substrate, a lower main radiation plate, a coupling short-circuit branch, and a feeding probe; The dielectric substrate adopts a single-layer structure, the bottom of which is hollowed out to form a cavity, the lower main radiating plate is covered in the cavity, the coupling short-circuit branches include coupling branches embedded in the rectangular grooves of the lower main radiating plate, short-circuit branches connected to the coupling branches, and extension branches connected to the short-circuit branches; the upper radiating plate is covered on the upper layer of the dielectric substrate; The feeding probe is coupled to the lower main radiating plate for feeding, and penetrates the dielectric substrate and the upper radiating plate for direct feeding.

2. The low-profile, lightweight, dual-band Beidou navigation antenna according to claim 1, characterized in that: The overall size of the antenna is 30×30×6mm 3 , using ppo material as the dielectric substrate, the dielectric constant ε r =11, the hollow space size of the cavity is 28×28×4mm 3 , the antenna side wall thickness is 1mm.

3. The low-profile, lightweight, dual-band Beidou navigation antenna according to claim 1, characterized in that: The four edges of the lower main radiation piece are provided with rectangular grooves of equal area toward the center point, and the coupling branches in the coupling short-circuit branches are completely embedded in the rectangular grooves of the lower main radiation piece, with a gap left between them.

4. The low-profile, lightweight, dual-band Beidou navigation antenna according to claim 1, characterized in that: One end of the short-circuit branch is connected to the coupling branch, and is used to control the resonant frequency by adjusting the length of the extension branch; the other end extends along the inner wall of the dielectric substrate to the metal ground, and is used to change the current path and reduce the size of the antenna.

5. The low-profile, lightweight, dual-band BeiDou navigation antenna according to claim 1, characterized in that: The feeding probes are provided with four vertical feeding points at symmetrical positions along the center point of the antenna. The probes are spatially rotationally symmetrically distributed, and the phases of the excitation signals differ by 90 degrees.

6. The low-profile, lightweight, dual-band Beidou navigation antenna according to claim 1, characterized in that: Four circular holes are opened on the lower main radiation plate, and the feeding probe is coupled and fed through the circular holes, so that the lower radiation plate operates in the B3I frequency band.

7. The low-profile, lightweight, dual-band Beidou navigation antenna according to claim 1, characterized in that: The upper radiation piece works directly in the B1I frequency band through the feeding probe, and the size of the upper radiation piece is adjustable to control the resonant frequency of the B1I frequency band. The quadrilateral rectangular slots and coupling branches of the lower main radiation piece serve as the radiation body of the B1I frequency band.

8. The low-profile, lightweight, dual-band Beidou navigation antenna according to claim 7, characterized in that: The upper radiation piece changes the electromagnetic coupling strength with the lower main radiation piece by adjusting its own size. When the size of the upper radiation piece increases, the binding effect on the high-frequency current of the lower layer is enhanced, so that the resonant frequency is reduced. When the size of the upper radiation piece is reduced, the electromagnetic coupling is weakened, and the resonant frequency is increased, thereby achieving secondary radiation of the energy of the upper radiation piece to the lower main radiation piece.

9. The low-profile, lightweight, dual-band BeiDou navigation antenna according to any one of claims 1 to 8, characterized in that: The coupled short-circuit branch forms an LC resonant loop with the lower main radiation plate, and a parallel inductance effect is introduced through the short-circuit structure, thereby shortening the current path and reducing the equivalent electrical size of the antenna.

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