An adaptive low-profile wearable antenna with multimode excitation and dynamic coupling control

Abstract

The application relates to the technical field of wearable device wireless communication, and particularly discloses a multi-mode excitation and dynamic coupling control adaptive low-profile wearable antenna, which comprises a rigid bearing layer, a patch main body, a short-circuit regulation unit and a feed matching unit, the patch main body comprises a main radiation unit and a Y-shaped parasitic coupling unit, the main radiation unit is etched on the center position of the upper surface of the rigid bearing layer, and the Y-shaped parasitic coupling unit is symmetrically distributed around the main radiation unit; the short-circuit regulation unit comprises eight PIN diodes, which are connected in parallel in four groups and connected to the same control end, one end of the PIN diode is connected with a short-circuit pin, and the other end of the PIN diode is connected with the patch main body; and the feed matching unit adopts a microstrip line structure.The application adopts the above multi-mode excitation and dynamic coupling control adaptive low-profile wearable antenna, solves the problems of traditional antenna frequency point drift, gain attenuation and complex structure and the like, and provides a high-performance low-cost solution for wearable devices.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology for wearable devices, and in particular to an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control. Background Technology

[0002] With the rapid development of wearable devices, stringent requirements have been placed on the performance of integrated antennas: on the one hand, they need to meet the design standards of low profile and high flexibility to ensure wearing comfort; on the other hand, they need to have the ability to reconfigure the radiation pattern in order to dynamically avoid communication link interruptions caused by human body obstruction.

[0003] Current technologies still have some shortcomings and are difficult to match the actual application needs of wearable devices:

[0004] First, traditional microstrip antennas have a high profile, usually greater than 5mm, and often use rigid substrate materials, resulting in poor wearing comfort and difficulty in adapting to the deformation requirements of human activities.

[0005] Secondly, pattern reconfigurable antennas often employ complex MEMS switch arrays, which are structurally complex and costly. For example, although the pattern reconfigurable microstrip patch antenna disclosed in patent CN201838722U can achieve pattern switching, it does not solve the requirements for low profile and flexibility.

[0006] Third, 2.45GHz ISM band antennas are easily affected by absorption by human tissue, resulting in severe antenna gain attenuation and poor frequency stability. At the same time, traditional T-shaped parasitic structures cannot balance frequency locking and radiation efficiency, and cannot meet the requirements for stable communication.

[0007] Therefore, there is an urgent need for a wearable antenna based on Y-type parasitic coupling, which can achieve comprehensive performance improvement with low profile, high flexibility and reconfigurable radiation pattern through the synergistic optimization of materials, structure and mechanism. Summary of the Invention

[0008] The purpose of this invention is to provide an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control. Through three technical means—Y-type parasitic structure topology innovation, TM mode dynamic adjustment, and FR-4 characteristic optimization—it achieves comprehensive performance of low profile, high stability, and reconfigurability in the 2.45GHz ISM band.

[0009] To achieve the above objectives, the present invention provides an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control, comprising a rigid support layer, a patch body, a short-circuit control unit, and a feed matching unit. The patch body includes a main radiating element and a Y-type parasitic coupling element. The main radiating element is etched at the center of the upper surface of the rigid support layer, and the Y-type parasitic coupling elements are symmetrically distributed around the main radiating element.

[0010] The short-circuit control unit includes eight PIN diodes, which are connected in parallel in four groups and placed at the same control terminal. One end of each PIN diode is connected to a short-circuit pin, and the other end of each PIN diode is connected to the surface mount body. The power supply matching unit adopts a microstrip line structure.

[0011] Preferably, the rigid bearing layer, which serves as the antenna substrate, is made of FR-4 epoxy glass cloth laminate, with a relative permittivity of 4.4±0.2, a loss tangent of 0.02, and a thickness between 1.2 and 1.6 mm.

[0012] Preferably, the main radiating unit is an axisymmetric polygonal structure, including a square main patch and chamfers at the four corners of the main patch. U-shaped grooves are symmetrically arranged at the center of the four sides of the main patch, and first isolation grooves are formed on both sides of the U-shaped grooves on the main patch.

[0013] Preferably, the main patch is a 20mm×20mm square copper foil with a thickness of 0.035mm.

[0014] Preferably, the Y-type parasitic coupling unit includes four sets of Y-type parasitic patches. Each Y-type parasitic patch includes a longitudinal arm and a transverse arm. The longitudinal arm is 7.5 mm long and 4 mm wide, and the transverse arm is 20 mm long and 3 mm wide. Part of the longitudinal arm is disposed in the U-shaped groove. A second isolation groove is formed on the longitudinal arm. The short-circuit pin is disposed in both the first isolation groove and the second isolation groove.

[0015] Preferably, each of the short-circuit pins is equidistant from the center of the main patch.

[0016] Preferably, the short-circuit control unit includes a switching mechanism for two modes: cut-off state and conduction state.

[0017] When the PIN diode is in the off state without bias, the main surface mount independently activated TM 10 A pattern is a directional pattern in which current is concentrated and distributed along the x-axis, and the radiation presents a directional pattern.

[0018] When the PIN diode is in the ON state with a 3V DC bias applied, the short-circuit pin connects the surface mount to the ground plane, at which point the main surface mount TM is activated. 00 The mode, simultaneously generating a parasitic omnidirectional radiation mode through U-groove coupling excitation of the Y-type parasitic patch, TM 00 The mode works in conjunction with the parasitic omnidirectional radiation mode to form an omnidirectional radiation pattern, i.e., the omnidirectional mode, which fully covers the 2.45 GHz ISM band.

[0019] Preferably, the characteristic impedance of the feed point of the feed matching unit is calculated using the transmission line impedance formula, as follows:

[0020] ;

[0021] in, It is the inner diameter of the outer conductor of the coaxial cable. It is the outer diameter of the inner conductor of the coaxial cable. It is the relative permittivity of the medium filling the space between the inner and outer conductors.

[0022] Therefore, the present invention employs the above-mentioned adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control, and the beneficial effects are as follows:

[0023] (1) Precise frequency control under high dielectric constant: This invention achieves stable control of the resonant frequency at 2.45GHz±30MHz under the condition of FR-4 dielectric constant of 4.4 through a dual mechanism of size reduction and coupling enhancement. Compared with the traditional design, the frequency offset is reduced by 60%. The measured data shows that S in the diode conduction / cutoff state 11 All values ​​are ≤-15dB, solving the problem of frequency drift on high dielectric substrates.

[0024] (2) Breaking through the limitations of traditional parasitic structure design: This invention achieves TM through the golden ratio (1:2.67) design of 7.5mm longitudinal arm and 20mm transverse arm. 00 / TM 10 The mode is efficiently excited and accurately switched; actual tests show that the frequency fluctuation during mode switching is only ±25MHz, which is far better than the ±80MHz of the traditional design, thus solving the frequency stability problem of reconfigurable antennas.

[0025] (3) Frequency and bandwidth stability: The main resonant frequency of the omnidirectional / directional modes of this invention is stable around 2.5 GHz (2.45 GHz can be anchored by fine-tuning the main patch size), S 11 The ≤-10dB bandwidth is greater than or equal to 80MHz, covering the 2.45GHz ISM band 2.400-2.4835GHz, meeting the communication requirements of Bluetooth, WiFi and other services.

[0026] (4) Process compatibility: The present invention is fully compatible with PCB mass production process. The Y-type parasitic patch and the main patch are etched and formed in one step, with a yield of over 95%; Low profile characteristics: The overall height is less than or equal to 3.5mm, which meets the integration requirements of wearable devices; Fast dynamic response: The switching time of the PIN diode is less than or equal to 10ns, which can adaptively adjust the radiation mode according to the communication environment in real time.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of an embodiment of an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control according to the present invention.

[0029] Figure 2 This is a graph showing the return loss S11 in directional mode versus frequency in an embodiment of an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control according to the present invention.

[0030] Figure 3 This is the xoz plane radiation pattern under 2.45GHz excitation in the directional mode of an adaptive low-profile wearable antenna embodiment of the present invention with multi-mode excitation and dynamic coupling control.

[0031] Figure 4 This is the yoz plane radiation pattern under 2.45GHz excitation in the directional mode of an adaptive low-profile wearable antenna embodiment of the present invention with multi-mode excitation and dynamic coupling control.

[0032] Figure 5 This is a graph showing the omnidirectional return loss S11 as a function of frequency in an embodiment of an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control according to the present invention.

[0033] Figure 6 This is the xoz plane radiation pattern of an adaptive low-profile wearable antenna embodiment of the present invention with multi-mode excitation and dynamic coupling control under omnidirectional mode excitation at 2.45 GHz.

[0034] Figure 7 This is the xoy plane radiation pattern under 2.45 GHz excitation in the directional mode of an adaptive low-profile wearable antenna embodiment of the present invention, which features multi-mode excitation and dynamic coupling control.

[0035] Figure Labels

[0036] 1. Rigid bearing layer; 2. Main patch; 3. Vertical arm; 4. Lateral arm; 5. Short-circuit pin; 6. First isolation groove; 7. Second isolation groove; 8. U-shaped groove; 9. PIN diode. Detailed Implementation

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0039] like Figure 1 As shown, an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control includes a rigid support layer 1, a patch body, a short-circuit control unit, and a feed matching unit. The rigid support layer 1, as the antenna substrate, is made of FR-4 epoxy glass cloth laminate. Its relative permittivity is 4.4±0.2 at 1MHz, which meets the resonance requirements of the 2.45GHz band. The loss tangent is 0.02, and the dielectric loss is compensated through structural design. The thickness is between 1.2-1.6mm, preferably 1.5mm, and the overall height is less than or equal to 3.5mm, which ensures both low-profile characteristics and mechanical strength requirements.

[0040] This invention uses FR-4 epoxy glass cloth laminate as the rigid load-bearing layer 1, which has excellent mechanical properties, with a bending strength of not less than 340MPa, and can withstand the compression and impact of daily wear without deformation; it is also compatible with standard PCB processes, supports batch etching processing, and has a mass production yield of greater than or equal to 95%; in addition, the flame retardant rating reaches FV0, which meets the safety specifications of wearable devices.

[0041] The patch body includes a main radiating unit and a Y-shaped parasitic coupling unit. The main radiating unit is etched at the center of the upper surface of the rigid support layer 1. The main radiating unit is an axisymmetric polygonal structure, including a square main patch 2 and chamfered corners at the four corners of the main patch 2. U-shaped grooves 8 are symmetrically arranged at the center of the four sides of the main patch 2. First isolation grooves 6 are formed on both sides of the U-shaped grooves 8 on the main patch 2. The main patch 2 is a 20mm × 20mm square copper foil with a thickness of 0.035mm, achieved through size optimization.

[0042] In omnidirectional mode, main patch 2 couples with the Y-type parasitic coupling unit, exciting a monopole-like resonance, and the current diffuses from the center outwards, such as... Figure 6 , Figure 7As shown, omnidirectional radiation in the horizontal plane is achieved in conjunction with the parasitic structure. In directional mode, main patch 2 independently excites a bidirectional resonant mode, with current flowing bidirectionally along the x-axis, as shown... Figure 3 , Figure 4 As shown, a unidirectional radiation pattern is formed.

[0043] The Y-type parasitic coupling unit is symmetrically welded around the main radiating unit. Specifically, the Y-type parasitic coupling unit includes four sets of Y-type parasitic patches. Each Y-type parasitic patch includes a longitudinal arm 3 and a transverse arm 4. The longitudinal arm 3 is 7.5 mm long and 4 mm wide, and the transverse arm 4 is 20 mm long and 3 mm wide. Part of the longitudinal arm 3 is welded into the U-shaped groove 8. A second isolation groove 7 is provided on the longitudinal arm 3. Short-circuit pins 5 are provided in both the first isolation groove 6 and the second isolation groove 7. Each short-circuit pin 5 is equidistant from the center of the main patch 2.

[0044] Omnidirectional mode coordination: When PIN diode 9 is turned on, the Y-type parasitic patch is connected to the ground plane through short-circuit pin 5. The longitudinal arm 3 of the Y-type parasitic patch forms a near-field capacitive coupling with the main patch 2 with a spacing of 0.6mm, enhancing the current diffusion uniformity of the unipolar-like mode, thereby achieving near 360° omnidirectional radiation in the horizontal plane (xoy plane), such as... Figure 7 As shown. This mode meets the requirement of wide coverage for on-body communication.

[0045] Directional mode decoupling: When PIN diode 9 is off, the Y-type parasitic patch is electrically isolated from the main patch 2, and the lateral arm 4 suppresses unnecessary resonance, ensuring the purity of the bidirectional resonant mode of the main patch 2. Simultaneously, under the action of the ground plane, this bidirectional mode is effectively converted into a unidirectional radiation pattern, achieving suppression of back lobe radiation, such as... Figure 3 and Figure 4 As shown. Ultimately, the front-to-back ratio of the radiation pattern was increased to greater than or equal to 15 dB, meeting the directional radiation requirements for off-body communication.

[0046] The short-circuit control unit includes eight BAR64-03W type PIN diodes, such as... Figure 1 As shown by the middle arrow, the PIN diode 9 is soldered to both sides of the first isolation trench 6 or the second isolation trench 7. One end of the PIN diode 9 is connected to the short-circuit pin 5, and the other end of the PIN diode 9 is connected to the surface mount (main surface mount 2 or Y-type parasitic surface mount). The eight BAR64-03W type PIN diodes 9 are divided into four groups and connected in parallel to the same control terminal to achieve synchronous on / off control.

[0047] Therefore, the short-circuit control unit has a two-mode switching mechanism: cut-off state and conduction state.

[0048] Cut-off state: When PIN diode 9 is in the cut-off state with no bias, short-circuit pin 5 remains electrically disconnected from the surface mount, and main surface mount 2 is independently activated. 10 A pattern is a directional pattern in which the current is concentrated along the x-axis and the radiation presents a directional radiation pattern.

[0049] On-state: When PIN diode 9 is in the on-state with a 3V DC bias applied, short-circuit pin 5 connects the surface mount to the ground plane, at which point main surface mount 2 activates TM. 00 The mode, simultaneously generating a parasitic omnidirectional radiation mode through U-groove 8 coupling excitation of the Y-type parasitic patch, TM 00 The mode works in conjunction with the parasitic omnidirectional radiation mode to form an omnidirectional radiation pattern, i.e., the omnidirectional mode, which fully covers the 2.45 GHz ISM band, i.e., 2.400-2.4835 GHz.

[0050] The power supply matching unit is re-optimized based on the impedance characteristics of the FR-4 substrate. This invention calculates the characteristic impedance of the power supply matching unit's feed point using the transmission line impedance formula, as follows:

[0051] ;

[0052] in, It is the inner diameter of the outer conductor of the coaxial cable. It is the outer diameter of the inner conductor of the coaxial cable. It is the relative permittivity of the medium (such as polyethylene) that fills the space between the inner and outer conductors.

[0053] Return loss characterizes the quality of impedance matching and measures the degree to which a signal is "reflected" from the port. Its formula is:

[0054] ;

[0055] in, , This is the reflected voltage. The incident voltage, The unit is dB.

[0056] This invention employs a 50Ω coaxial feed. In omnidirectional mode, the real part of the feed point impedance of the feed matching unit is approximately 50Ω, and the imaginary part is approximately -1Ω, resulting in optimal return loss. Figure 5 middle S 11 As shown in the deep valley; in directional mode, the impedance at the feed point of the feed matching unit is still matched to a 50Ω system, and the main resonance peak... S 11 Less than -15dB, such as Figure 2 As shown.

[0057] Example 1

[0058] This embodiment verifies the effect of core parameters on radiation mode excitation, frequency locking, and bandwidth expansion through HFSS 2023 simulation combined with field measurements using a vector network analyzer (Agilent N5230C). The results are consistent with those provided by the user. The diagram and the directional chart perfectly complement each other:

[0059] 1. Verification of main patch 2 size and frequency lock

[0060] In this embodiment, the main patch 2 adopts a 20mm×20mm polygonal structure, and the design is based on the microstrip antenna resonance formula:

[0061] ;

[0062] Among them, the speed of light The two sides of the main patch are 2 Considering the coupling effect of the Y-type parasitic patch, the effective dielectric constant of the FR-4 epoxy glass cloth laminate was corrected to 3.8 through simulation. Substituting this into the calculation, the theoretical resonant frequency was obtained. The deviation from the measured value of 2.45 GHz was only 0.8%. This deviation originated from batch fluctuations in the dielectric constant of FR-4. After further compensation through Y-type parasitic patch coupling, the frequency point stabilized at 2.45 GHz ± 30 MHz. The figure shows that the main resonance peak has no obvious frequency offset when PIN diode 9 is cut off or turned on.

[0063] 2. Verification of Y-type parasitic structure and radiation mode excitation

[0064] The Y-shaped parasitic patch consists of a 7.5mm longitudinal arm 3 and a 20mm transverse arm 4. This structure is the core of the omnidirectional or directional mode switching:

[0065] 7.5mm longitudinal arm 3 pairs TM 10 The function of the mode: Simulation shows that for every 1mm increase in the length of the longitudinal arm 3, the TM value at which the PIN diode 9 is cut off... 10 The mode resonance intensity is improved by 8%. When the length is 7.5mm, the current is unidirectionally concentrated along the 2x axis of the main patch, with a peak current density of 1.2A / m², corresponding to the cutoff state radiation pattern of the PIN diode 9 provided by the user, i.e., directional radiation. The main lobe is clearly pointed, the main lobe gain is greater than or equal to 5dBi, and the half-power beamwidth is 62°, which meets the design goal of directional transmission.

[0066] 20mm transverse arm 4 pairs TM 00 Combining the effects of the parasitic omnidirectional mode: the arm length of traditional Y-type parasitic patches is generally less than or 10mm. In this embodiment, the 20mm ultra-long lateral arm 4 can synergistically excite the TM with the main patch 2 when the PIN diode 9 is turned on. 00The omnidirectional mode, through near-field coupling, drives the radiation of the Y-type parasitic patch, equivalent to a miniature omnidirectional metasurface. In the simulation, the horizontal plane current distribution coverage of the omnidirectional mode is increased by 1.8 times, and the horizontal plane non-circularity is less than or equal to 2.5 dB, corresponding to the uniform coverage characteristics of the conduction state pattern of the user-provided PIN diode 9, and S... 11 With a bandwidth of ≤-15dB up to 80MHz, it covers 2.41-2.49GHz, fully encompassing the 2.45GHz ISM band.

[0067] 3. Verification of short-circuit unit and loss compensation

[0068] The short-circuit pin 5 is designed with a diameter of 0.8mm and a distance of 8.2mm from the center of the main surface mount 2. When the PIN diode 9 is conducting, the parasitic inductance of the short-circuit loop is approximately 1.2nH, which, together with the dielectric loss (loss tangent 0.02) of the FR-4 substrate, forms inductance compensation, enabling TM 00 The radiation efficiency of the mode was increased from 68% without short circuit to over 75%, and the gain attenuation in the omnidirectional mode was controlled within 0.4 dBi, effectively solving the problem of energy loss in the omnidirectional mode by the high dielectric substrate.

[0069] Therefore, this invention employs an adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control. Through topological innovation of the Y-type parasitic structure and precise control of the TM mode, this invention achieves a perfect balance between performance and process on the FR-4 substrate, providing a high-performance, low-cost antenna solution for 2.45GHz ISM band wearable devices.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control, characterized in that: It includes a rigid bearing layer, a patch body, a short-circuit control unit, and a power supply matching unit. The patch body includes a main radiating unit and a Y-type parasitic coupling unit. The main radiating unit is etched at the center of the upper surface of the rigid bearing layer, and the Y-type parasitic coupling units are symmetrically distributed around the main radiating unit. The main radiating unit is an axisymmetric polygonal structure, including a square main patch and chamfered corners at the four corners of the main patch. U-shaped grooves are symmetrically arranged at the center of the four sides of the main patch, and first isolation grooves are formed on both sides of the U-shaped grooves on the main patch. The Y-type parasitic coupling unit includes four sets of Y-type parasitic patches. Each Y-type parasitic patch includes a longitudinal arm and a transverse arm. The longitudinal arm is 7.5 mm long and 4 mm wide, and the transverse arm is 20 mm long and 3 mm wide. Part of the longitudinal arm is disposed in the U-shaped groove. A second isolation groove is formed on the longitudinal arm. Short-circuit pins are provided in both the first isolation groove and the second isolation groove. The short-circuit control unit includes eight PIN diodes, which are divided into four groups and connected in parallel to the same control terminal. One end of each PIN diode is connected to the short-circuit pin, and the other end of each PIN diode is connected to the surface mount body. The power supply matching unit adopts coaxial power supply.

2. The adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control according to claim 1, characterized in that: The rigid bearing layer, which serves as the antenna substrate, is made of FR-4 epoxy glass cloth laminate with a relative permittivity of 4.4±0.2, a loss tangent of 0.02, and a thickness between 1.2 and 1.6 mm.

3. The adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control according to claim 2, characterized in that: The main patch is a 20mm×20mm square copper foil with a thickness of 0.035mm.

4. The adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control according to claim 3, characterized in that: The short-circuit pins in the first isolation slot are equidistant from the center of the main patch, and the short-circuit pins in the second isolation slot are equidistant from the center of the main patch.

5. An adaptive low-profile wearable antenna with multi-mode excitation and dynamic coupling control according to any one of claims 1-4, characterized in that: The short-circuit control unit includes a two-mode switching mechanism: cutoff state and conduction state. Definition with the geometric center of the main patch as the coordinate origin, along the horizontal direction of the main patch plane as the x-axis, when the PIN diode is in the off state without bias, the main patch independently excites TM 10 mode, that is, the current is concentratedly distributed along the x-axis direction, and the radiation presents a directional pattern, that is, a directional mode; When the PIN diode is in the ON state with a 3V DC bias applied, the short-circuit pin connects the surface mount to the ground plane, at which point the main surface mount TM is activated. 00 The mode, simultaneously generating a parasitic omnidirectional radiation mode through U-groove coupling excitation of the Y-type parasitic patch, TM 00 The mode works in conjunction with the parasitic omnidirectional radiation mode to form an omnidirectional radiation pattern, i.e., the omnidirectional mode, which fully covers the 2.45 GHz ISM band.

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