Miniaturized multilayer capacitive coupled ltcc dual-band antenna

Abstract

The application discloses a miniaturized multilayer capacitive coupling LTCC dual-frequency antenna, which comprises an LTCC substrate, four metal layers embedded in the LTCC substrate, and a feeding electrode, a rear auxiliary electrode, a left ground electrode and a right ground electrode packaged on the surface of the LTCC substrate. The LTCC substrate comprises five dielectric layers, and the four metal layers are sequentially stacked in the vertical direction and are separated by the dielectric layers between adjacent metal layers. The four metal layers comprise a first coupling patch and a second coupling patch, a third coupling patch, a first radiation plate and a second radiation plate. The first coupling patch and the third coupling patch are coupled with the first radiation plate through interlayer coupling to generate a first resonant frequency; and the second coupling patch and the second radiation plate are coupled through interlayer coupling to generate a second resonant frequency which is higher than the first resonant frequency. The application realizes dual-frequency operation in a small size by optimizing the antenna structure, and has the characteristics of simple structure, easy processing and stable performance.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to a miniaturized multilayer capacitively coupled LTCC dual-band antenna. Background Technology

[0002] With the rapid popularization of fifth-generation mobile communication (5G) and Internet of Things (IoT) technologies, wireless terminal devices are accelerating their development towards high integration and ultra-miniaturization. As a key component of the radio frequency front end, antennas need to cover multiple frequency bands such as 2.4 GHz and 3.5 GHz simultaneously within a limited space, while ensuring sufficient bandwidth and radiation gain. Low-temperature co-fired ceramic (LTCC) technology, due to its ability to use high dielectric constant materials and its combination of multi-layer three-dimensional wiring capability and excellent high-frequency performance, has become an important technical approach for realizing miniaturized multi-band antennas.

[0003] In existing LTCC miniaturized antenna designs, zigzag and spiral structures are commonly used to extend the electrical length and reduce the resonant frequency. For example, there are schemes that use double-layer zigzag stacking to achieve dual-frequency operation, schemes that generate multiple resonant frequencies by coupling the upper and lower layers of zigzags, and schemes that use capacitively coupled feeding structures for impedance matching of small antennas.

[0004] However, existing LTCC dual-band antenna technology still has the following shortcomings: When the antenna size is further reduced, traditional zigzag or spiral structures cannot simultaneously guarantee the impedance bandwidth and radiation gain of both frequency bands, often resulting in low gain or excessively narrow bandwidth, which cannot meet the performance requirements of terminal equipment. In addition, existing miniaturized dual-band antennas typically use vertical through-holes to achieve interlayer connections, increasing processing difficulty and manufacturing costs, and the coupling method between multiple metal layers needs further optimization to achieve stable dual-band resonance in a small size.

[0005] Therefore, how to design an LTCC dual-band antenna that does not require a vertical through-hole, achieves dual-frequency operation, and has good radiation performance in a small size has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a miniaturized multilayer capacitively coupled LTCC dual-band antenna. By optimizing the coupling structure between multiple metal layers, dual-band operation is achieved in a small size while maintaining good impedance bandwidth and radiation gain. Furthermore, surface electrodes are used to achieve feeding and metal layer conduction, thereby solving the problems in existing technologies where the small physical size of the antenna makes it difficult to achieve both dual-band performance and the vertical through-hole structure increases processing difficulty and manufacturing cost.

[0007] The present invention provides a miniaturized multilayer capacitively coupled LTCC dual-band antenna, comprising an LTCC substrate, four metal layers embedded in the LTCC substrate, and a feed electrode, a rear auxiliary electrode, a left ground electrode, and a right ground electrode encapsulated on the surface of the LTCC substrate.

[0008] Furthermore, the LTCC substrate includes five dielectric layers: a first dielectric layer, a second dielectric layer, a third dielectric layer, a fourth dielectric layer, and a top cover dielectric layer.

[0009] Furthermore, among the four metal layers, the first metal layer includes a first coupling patch and a second coupling patch, the second metal layer is a third coupling patch, the third metal layer is a first radiating electrode, and the fourth metal layer is a second radiating electrode.

[0010] Furthermore, the LTCC substrate is configured with, from bottom to top, a first dielectric layer, a first metal layer, a second dielectric layer, a second metal layer, a third dielectric layer, a third metal layer, a fourth dielectric layer, a fourth metal layer, and a top cover dielectric layer, with the first coupling patch and the second coupling patch in the first metal layer located at the same height.

[0011] Furthermore, the LTCC substrate has opposing front end face and rear end face, as well as opposing left end face and right end face; the feed electrode is located on the front end face of the LTCC substrate, the rear auxiliary electrode is located on the rear end face of the LTCC substrate, the left ground electrode is located on the left end face of the LTCC substrate, and the right ground electrode is located on the right end face of the LTCC substrate. Furthermore, the rear auxiliary electrode has no electrical connection to any metal layer in the LTCC substrate and is used only for SMT mounting balance.

[0012] Furthermore, the thickness of each dielectric layer in the LTCC substrate is not uniform. The first dielectric layer is located at the bottom of the LTCC substrate and is used to support the first and second coupling patches. The second dielectric layer is disposed between the first and second metal layers, and its thickness determines the interlayer coupling strength between the first and third coupling patches. The third dielectric layer is disposed between the second and third metal layers, and its thickness affects the parallel plate capacitance value between the third coupling patch and the first radiating electrode. The fourth dielectric layer is disposed between the third and fourth metal layers. The thickness of each dielectric layer is independently adjusted according to the target coupling coefficient and capacitance value, and the two frequency bands are independently optimized.

[0013] Furthermore, the first coupling patch is a horizontally arranged metal patch, the main body of which is a rectangular metal patch, and a rectangular connecting strip extends from one side of the main body to connect with the feed electrode.

[0014] Furthermore, the second coupling patch is a horizontally arranged metal patch, the main body of which is a rectangular metal patch, and a rectangular connecting strip extends from one side of the main body to connect with the feed electrode.

[0015] Furthermore, neither the first coupling patch nor the second coupling patch is grounded.

[0016] Furthermore, the third coupling patch is located vertically above the first coupling patch, and its main body is a rectangular metal patch, with a rectangular connecting strip extending from one side of the main body to connect with the feed electrode.

[0017] Furthermore, the third coupling patch is separated from the first coupling patch by a second dielectric layer, and their projections in the vertical direction partially overlap, forming interlayer capacitive coupling.

[0018] Furthermore, the first radiating electrode is located vertically above the third coupling patch, and the third coupling patch and the first radiating electrode are separated by a third dielectric layer. The projections of the first radiating electrode and the third coupling patch in the vertical direction partially overlap, forming a parallel plate capacitor radiation structure between them.

[0019] Furthermore, the first radiating electrode is a horizontally arranged rectangular metal patch, the area of ​​which is larger than the area of ​​the third coupling patch.

[0020] Furthermore, the length of the first radiating electrode in the left-right direction is less than half the length of the LTCC substrate, and the width in the front-back direction is less than the width of the LTCC substrate.

[0021] Furthermore, the first radiating plate is not directly connected to the feeding electrode, but is fed by the third coupling patch through interlayer capacitive coupling.

[0022] Furthermore, the left end of the first radiating electrode is connected to the left ground electrode on the left end face of the LTCC substrate.

[0023] Furthermore, the second radiating electrode is located vertically above the second coupling patch, and a rectangular connecting strip extends from one side of the second radiating electrode to connect with the feeding electrode for feeding.

[0024] Furthermore, the second radiating electrode and the second coupling patch are separated by a second dielectric layer, a third dielectric layer and a fourth dielectric layer, and their projections in the vertical direction partially overlap, forming interlayer capacitive coupling.

[0025] Furthermore, the second radiating electrode is an interdigitated capacitor radiating structure, comprising multiple alternating metal fingers that form an interdigitated capacitor.

[0026] Furthermore, the right end of the second radiating electrode is connected to the right ground electrode on the right end face of the LTCC substrate.

[0027] Furthermore, the first coupling patch, the second coupling patch, the third coupling patch, and the second radiating plate are all directly physically connected by the feeding electrode to form a complete feeding network.

[0028] Furthermore, the first coupling patch and the third coupling patch transmit the power supply signal to the third coupling patch through interlayer capacitive coupling, and the third coupling patch then couples the energy to the first radiating plate through the parallel plate capacitance effect, thereby generating the first resonant frequency.

[0029] Furthermore, a second resonant frequency is generated between the second coupling patch and the second radiating electrode through interlayer capacitive coupling.

[0030] This invention provides a miniaturized multilayer capacitively coupled LTCC dual-band antenna, and also includes a test circuit board. The test circuit board includes a test dielectric substrate, coplanar waveguide signal lines, impedance matching lines, metal shorting plates, a left PCB ground pad, a right PCB ground pad, a ground plane, and a clearance area.

[0031] Furthermore, the test dielectric substrate, the coplanar waveguide signal line, and the ground plane constitute a coplanar waveguide transmission line, and the linewidth of the coplanar waveguide signal line is calculated based on the dielectric constant and thickness of the test dielectric substrate.

[0032] Furthermore, the left PCB grounding pad and the right PCB grounding pad are symmetrically arranged and located on the ground area of ​​the test circuit board at the edge of the clearance area.

[0033] Furthermore, the clearance area is located below the antenna installation position, and the range of the clearance area should ensure that the antenna has good radiation performance; the antenna is set across the clearance area, the antenna feed electrode is electrically connected to the coplanar waveguide signal line through an impedance matching line, and the left ground electrode and right ground electrode of the antenna are electrically connected to the ground plane of the test circuit board through the left PCB ground pad and the right PCB ground pad, respectively.

[0034] Furthermore, the impedance matching line is arranged horizontally on the test dielectric substrate in a zigzag shape, with one end of the impedance matching line connected to the feed electrode of the antenna and the other end connected to the coplanar waveguide signal line.

[0035] Furthermore, the length and width of the impedance matching line segments are adjusted according to the target input impedance of the antenna to achieve good impedance matching between the antenna and the coplanar waveguide transmission line. Furthermore, the end of the impedance matching line closest to the coplanar waveguide signal line is shorted to the ground plane below via a metal shorting plate.

[0036] Furthermore, the metal shorting piece is used to assist in impedance matching, enabling the antenna to exhibit purely resistive characteristics within the operating frequency band.

[0037] Compared with the prior art, the present invention has the following advantages: 1) The miniaturized multilayer capacitively coupled LTCC dual-band antenna structure proposed in this invention has an ingenious design, simple processing technology, stable working performance, and small physical size, which effectively solves the technical problem that ultra-small terminal devices are limited by antenna size and it is difficult to simultaneously take into account the radiation performance of dual bands. 2) This invention directly and physically connects multiple coupling patches and radiating plates simultaneously through the feeding electrode, and with the interlayer capacitive coupling, completely avoids the use of vertical through holes, reducing the difficulty and manufacturing cost of LTCC multilayer stacking process. 3) This invention further increases the equivalent electrical length of the antenna through interlayer capacitive coupling, enabling the antenna to operate in dual frequencies of 2.4 GHz and 3.5 GHz within a 2012 package size, while maintaining good impedance bandwidth and radiation gain in both frequency bands. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 This is a three-dimensional perspective structural diagram of the miniaturized multilayer capacitively coupled LTCC dual-band antenna provided in an embodiment of the present invention.

[0040] Figure 2 This is an exploded view of the stacked structure of a miniaturized multilayer capacitively coupled LTCC dual-band antenna provided in an embodiment of the present invention.

[0041] Figure 3 This is a top view of the test circuit board for a miniaturized multilayer capacitively coupled LTCC dual-band antenna provided in an embodiment of the present invention.

[0042] Figure 4 The simulation curve of return loss of the miniaturized multilayer capacitively coupled LTCC dual-band antenna provided in the embodiment of the present invention is shown.

[0043] Figure 5 The 2.4 GHz three-dimensional radiation pattern of a miniaturized multilayer capacitively coupled LTCC dual-band antenna provided in an embodiment of the present invention.

[0044] Figure 6The 3.5 GHz three-dimensional radiation pattern of a miniaturized multilayer capacitively coupled LTCC dual-band antenna provided in an embodiment of the present invention.

[0045] The attached figures are labeled as follows: LTCC substrate 101, first coupling patch 1.1, second coupling patch 1.2, third coupling patch 2, first radiating electrode 3, second radiating electrode 4, feed electrode 5.1, rear auxiliary electrode 5.2, left ground electrode 6.1, right ground electrode 6.2, first dielectric layer 7, second dielectric layer 8, third dielectric layer 9, fourth dielectric layer 10, top cover dielectric layer 11, test dielectric substrate 102, antenna mounting position 12, coplanar waveguide signal line 13, impedance matching line 14, metal shorting piece 15, left PCB ground pad 16.1, right PCB ground pad 16.2, ground plane 17, clearance area 18. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be further described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] In this invention, descriptions involving orientation or directional indications (e.g., up, down, front, back, left, right, etc.) are only used to explain the relative positions or motion relationships between components in a specific posture. If the specific posture changes, the corresponding directional indications will also change.

[0048] In this invention, ordinal numbers such as "first" and "second" are used only for descriptive purposes and should not be construed as indicating relative importance or implicitly specifying the number of technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible to those skilled in the art. If a combination is contradictory or impossible to implement, such a combination is invalid and does not fall within the scope of protection claimed by this invention.

[0049] Example 1

[0050] like Figure 1As shown, this embodiment of the invention provides a miniaturized multilayer capacitively coupled LTCC dual-band antenna, including an LTCC substrate 101, embedded metal layers (first coupling patch 1.1, second coupling patch 1.2, third coupling patch 2, first radiating electrode 3, second radiating electrode 4), and surface-mounted electrode patches (feed electrode 5.1, rear auxiliary electrode 5.2, left ground electrode 6.1, right ground electrode 6.2). In this embodiment, the overall package size of the LTCC substrate 101 is 2.0 mm × 1.2 mm × 0.9 mm, corresponding to the 2012 package specification, with a relative permittivity of 8 and a loss tangent of 0.006. The LTCC substrate is formed by laminating and sintering multiple layers of ceramic green tape, containing five dielectric layers. Using a high-dielectric-constant ceramic material allows for a reduction in operating frequency without increasing physical size, enabling electromagnetic waves to propagate within it with a shorter operating wavelength, thereby achieving miniaturization of the antenna at the physical level. The metal conductor is silver, and all metal patterns are embedded in the LTCC substrate 101. The silver conductor has excellent conductivity, which helps to ensure the radiation efficiency of the antenna.

[0051] The LTCC substrate 101 has opposing front and rear faces, as well as opposing left and right faces. The front face of the LTCC substrate 101 has a feed electrode 5.1 for introducing external radio frequency signals. The rear face of the LTCC substrate 101 has a rear auxiliary electrode 5.2, which has no electrical connection to any of the metal layers within the LTCC substrate and is used only for SMT (Surface Mount Technology) mounting balance. The left face of the LTCC substrate has a left ground electrode 6.1, and the right face of the LTCC substrate 101 has a right ground electrode 6.2.

[0052] like Figure 2 As shown, the LTCC substrate 101 is provided with the following layers stacked from bottom to top: a first dielectric layer 7, a first metal layer (first coupling patch 1.1 and second coupling patch 1.2), a second dielectric layer 8, a second metal layer (third coupling patch 2), a third dielectric layer 9, a third metal layer (first radiating electrode 3), a fourth dielectric layer 10, a fourth metal layer (second radiating electrode 4), and a top cover dielectric layer 11.

[0053] In this embodiment, the materials of the first dielectric layer 7, the second dielectric layer 8, the third dielectric layer 9, the fourth dielectric layer 10, and the top cover dielectric layer 11 are all LTCC ceramic dielectrics, with a relative permittivity of 8 and a loss tangent of 0.006. However, the thickness of each dielectric layer is not uniform. Specifically, the first dielectric layer 7 is located at the bottom of the LTCC substrate 101 and is used to support the first coupling patch 1.1 and the second coupling patch 1.2; the second dielectric layer 8 is disposed between the first metal layer and the second metal layer, and its thickness determines the interlayer coupling strength between the first coupling patch 1.1 and the third coupling patch 2; the third dielectric layer 9 is disposed between the second metal layer and the third metal layer, and its thickness affects the parallel plate capacitance value between the third coupling patch 2 and the first radiating electrode 3; the fourth dielectric layer 10 is disposed between the third metal layer and the fourth metal layer. The thickness of each dielectric layer can be independently adjusted according to the target coupling coefficient and capacitance value, and the two frequency bands can be independently optimized.

[0054] Specifically, the first coupling patch 1.1, the second coupling patch 1.2, the third coupling patch 2, and the second radiating plate 4 are all directly physically connected to the feeding electrode 5.1 for power supply. In other words, the feeding electrode 5.1 connects to four metal structures simultaneously, forming a complete power supply network.

[0055] A first coupling patch 1.1 and a second coupling patch 1.2 are disposed in the first metal layer within the LTCC substrate 101. The first coupling patch 1.1 is a horizontally disposed metal patch, the main body of which is a rectangular metal patch, and a rectangular connecting strip extends from one side of the main body to connect with the feed electrode 5.1. The second coupling patch 1.2 is also a horizontally disposed metal patch, the main body of which is also a rectangular metal patch, and a rectangular connecting strip extends from one side of the main body to connect with the feed electrode 5.1. Neither the first coupling patch 1.1 nor the second coupling patch 1.2 is grounded.

[0056] The third coupling patch 2 is disposed in the second metal layer within the LTCC substrate 101, located vertically above the first coupling patch 1.1. Its main body is a rectangular metal patch, with a rectangular connecting strip extending from one side of the main body to connect with the feed electrode 5.1. The third coupling patch 2 and the first coupling patch 1.1 are separated by a second dielectric layer 8, and their vertical projections partially overlap, forming interlayer capacitive coupling.

[0057] The first radiating electrode 3 is disposed in the third metal layer within the LTCC substrate 101, located vertically above the third coupling patch 2. The third coupling patch 2 and the first radiating electrode 3 are separated by a third dielectric layer 9. The projections of the first radiating electrode 3 and the third coupling patch 2 in the vertical direction partially overlap, forming a parallel plate capacitive radiation structure. The first radiating electrode 3 is a horizontally arranged rectangular metal patch with an area larger than that of the third coupling patch 2. Specifically, the length of the first radiating electrode 3 in the left-right direction is less than half the length of the LTCC substrate 101 (i.e., the total length in the left-right direction), and its width is less than the width of the LTCC substrate 101 (the front-back dimension). The first radiating electrode 3 is not directly connected to the feed electrode 5.1, but is fed by the third coupling patch 2 through interlayer capacitive coupling. The left end of the first radiating electrode 3 is connected to the left ground electrode 6.1 on the left end face of the LTCC substrate 101. Since the area of ​​the first radiating plate 3 is larger than the area of ​​the third coupling patch 2, the area between them approximates a parallel plate capacitor. The capacitance value of the first radiating plate 3 is directly proportional to the area between them and inversely proportional to the thickness of the third dielectric layer 9. In this embodiment, by increasing the area of ​​the first radiating plate 3 and controlling the thickness of the third dielectric layer 9, a sufficient capacitance value can be obtained to enable the antenna to resonate in the 2.4 GHz frequency band.

[0058] The second radiating electrode 4 is disposed in the fourth metal layer within the LTCC substrate 101, and is located vertically above the second coupling patch 1.2. A rectangular connecting strip extends from one side of the second radiating electrode 4 and connects to the feed electrode 5.1 for feeding. The second radiating electrode 4 and the second coupling patch 1.2 are separated by the second dielectric layer 8, the third dielectric layer 9, and the fourth dielectric layer 10. Their projections in the vertical direction partially overlap, forming interlayer capacitive coupling. The second radiating electrode 4 is an interdigitated capacitor radiating structure, including multiple alternately arranged metal fingers, which form an interdigitated capacitor. In this embodiment, there are five metal fingers, arranged in an asymmetrical layout of three on the left and two on the right, forming four alternating gaps. Each metal finger is rectangular, extending along the front-back direction of the LTCC substrate 101 in the length direction and arranged along the left-right direction in the width direction. This asymmetrical layout accommodates a sufficient number of interdigitated pairs within a limited package size to obtain a large capacitance value, enabling the antenna to resonate in the 3.5GHz band. The electric field of the interdigital capacitor is mainly concentrated in the gaps of the same metal layer and is less affected by changes in the thickness of the dielectric layer. Therefore, its resonant frequency is not sensitive to fluctuations in the LTCC layer height, which is beneficial to ensuring frequency consistency during mass production of antennas. The right end of the second radiating electrode 4 is connected to the right ground electrode 6.2 on the right end face of the LTCC substrate 101.

[0059] The first coupling patch 1.1 and the third coupling patch 2 transmit the feed signal to the third coupling patch 2 via interlayer capacitive coupling. The third coupling patch 2 then couples the energy to the first radiating plate 3 via the parallel plate capacitance effect, thereby generating the first resonant frequency (2.4 GHz band in this embodiment). The second coupling patch 1.2 and the second radiating plate 4 (interdigitated capacitive radiating structure) generate the second resonant frequency (3.5 GHz band in this embodiment) via interlayer capacitive coupling.

[0060] It should be noted that the parallel-plate capacitor radiation structure formed by the first radiating plate 3 and the third coupling patch 2, and the interdigitated capacitor radiation structure of the second radiating plate 4, are different types of capacitive coupling structures. The parallel-plate capacitor radiation structure controls the capacitance value through the overlap area of ​​the upper and lower plates and the thickness of the third dielectric layer 9, making it suitable for generating resonance in the lower frequency band (2.4 GHz). The interdigitated capacitor radiation structure controls the capacitance value through the gap and number of metal fingers, making it suitable for generating resonance in the higher frequency band (3.5 GHz). This invention employs this heterogeneous combination resonant structure, which, compared to the existing technology that only uses a single type of zigzag or spiral structure, has a larger frequency ratio adjustment range. It can achieve independent control of two frequency bands in a small size (2.0 mm × 1.2 mm × 0.9 mm), avoiding the problem of severe coupling and difficulty in separation of resonant modes between homogeneous structures.

[0061] It should also be emphasized that the first coupling patch 1.1 and the second coupling patch 1.2 are one of the core designs of this invention. This invention uses horizontally arranged first coupling patches 1.1 and second coupling patches 1.2, fed by the feed electrode 5.1. Energy is transferred to the upper third coupling patch 2, first radiating plate 3, and second radiating plate 4 through interlayer capacitive coupling, further increasing the equivalent electrical length of the antenna. This allows the antenna to achieve good dual-frequency resonance characteristics even in a small size (2.0 mm × 1.2 mm × 0.9 mm), which is key to achieving antenna miniaturization.

[0062] Furthermore, the 2.4 GHz and 3.5 GHz frequency bands mentioned above are merely illustrative examples, and the heterogeneous resonant structure of the present invention is not limited to these two frequency bands. By adjusting the dielectric constant of the LTCC substrate 101, the dimensional parameters of each metal layer, and the thickness of each dielectric layer (especially the thickness of the second dielectric layer 8 and the third dielectric layer 9), the antenna structure of the present invention is also applicable to dual-band operation in other wireless communication frequency bands (such as 1.8 GHz, 2.1 GHz, 5 GHz, etc.), which will not be listed here.

[0063] Furthermore, within the three-dimensional dimensions of the LTCC substrate 101, dual-band antenna designs with different package specifications, such as 3216 and 2012, can be achieved by adjusting the parameters of each metal layer inside the antenna (such as the area of ​​the first radiating plate 3, the number and spacing of the fingers of the second radiating plate 4, and the extension length of each coupling patch) according to different application scenarios. This antenna structure allows the operating frequency to vary near the target frequency band by adjusting its structural parameters. Different package sizes can achieve different antenna performances; theoretically, a larger package corresponds to better radiation performance, thus meeting the performance and size requirements of different application scenarios.

[0064] Example 2

[0065] like Figure 3 As shown, this embodiment of the invention provides a miniaturized multilayer capacitively coupled LTCC dual-band antenna, which is also equipped with a test circuit board in practical applications. The test circuit board includes a test dielectric substrate 102, coplanar waveguide signal lines 13, impedance matching lines 14, metal shorting plates 15, a left PCB grounding pad 16.1, a right PCB grounding pad 16.2, a grounding plane 17, and a clearance area 18.

[0066] In this embodiment, the test dielectric substrate 102 is made of FR4 dielectric material, with a relative permittivity of 4.4, a loss tangent of 0.02, a thickness of 0.8 mm, and dimensions of 50 mm × 25 mm. In this embodiment, the test dielectric substrate 102, the coplanar waveguide signal line 13, and the ground plane 17 form a coplanar waveguide transmission line, with a characteristic impedance of 50Ω. The linewidth of the coplanar waveguide signal line 13 can be calculated based on the permittivity and thickness of the test dielectric substrate 102; in this embodiment, it is 0.6 mm. The clearance area 18 is located below the antenna mounting position 12, and the antenna is positioned across the clearance area 18. The antenna's feed electrode 5.1 is electrically connected to the coplanar waveguide signal line 13 via an impedance matching line 14. The antenna's left ground electrode 6.1 and right ground electrode 6.2 are electrically connected to the ground plane 17 of the test circuit board via the left PCB ground pad 16.1 and the right PCB ground pad 16.2, respectively.

[0067] Impedance matching line 14 is horizontally arranged in a zigzag shape on the test dielectric substrate 102 of the test circuit board. One end of impedance matching line 14 is connected to the feed electrode 5.1 of the antenna, and the other end is connected to the coplanar waveguide signal line 13. The length and width of the impedance matching line 14 are adjusted according to the target input impedance of the antenna to achieve good impedance matching between the antenna and the 50 Ω coplanar waveguide transmission line.

[0068] One end of the impedance matching line 14 near the coplanar waveguide signal line 13 is shorted to the ground plane 17 below via a metal shorting piece 15. This metal shorting piece 15 is used to assist in achieving impedance matching, so that the antenna exhibits purely resistive characteristics within the operating frequency band.

[0069] The left PCB grounding pad 16.1 and the right PCB grounding pad 16.2 are symmetrically arranged and located on the ground area of ​​the test circuit board at the edge of the clearance area 18. The antenna is mounted above the clearance area 18, and the clearance area 18 should ensure that the antenna has good radiation performance. In this embodiment, the width of the clearance area 18 is 6 mm, which can ensure that the antenna has good radiation space. If the width of the clearance area 18 is insufficient, the radiation performance of the antenna will be severely affected by the ground plane 17, resulting in a decrease in gain and a distortion of the radiation pattern.

[0070] Figure 4 This paper presents the simulation curves of antenna return loss (S11) versus frequency obtained by performing full-wave simulation analysis on the antenna model proposed in this embodiment using ANSYS high-frequency electromagnetic simulation software. Using -7 dB as the impedance bandwidth reference standard, the -7 dB impedance bandwidth is 120 MHz (2.38-2.50 GHz) in the 2.4 GHz band and 310 MHz (3.32-3.63 GHz) in the 3.5 GHz band. At the resonant point, the return loss value is -20.3 dB at 2.4 GHz and -13.1 dB at 3.5 GHz, indicating that the antenna has good impedance matching in both frequency bands. The miniaturized multilayer capacitively coupled LTCC dual-band antenna proposed in this invention has two operating frequency bands, 2.4 GHz and 3.5 GHz, meeting the basic engineering requirements for dual-band antennas in terminal devices such as WLAN and 5G indoor coverage.

[0071] Figure 5 and Figure 6 The images show the three-dimensional radiation patterns of the miniaturized multilayer capacitively coupled LTCC dual-band antenna proposed in this invention at operating frequencies of 2.4 GHz and 3.5 GHz, respectively. The radiation pattern at 2.4 GHz is approximately apple-shaped, exhibiting good omnidirectional radiation characteristics with a maximum gain of 2.8 dB. Similarly, the radiation pattern at 3.5 GHz is also approximately apple-shaped, with good omnidirectional radiation characteristics and a maximum gain of 2.51 dB. Therefore, the miniaturized multilayer capacitively coupled LTCC dual-band antenna designed in this invention exhibits good radiation characteristics in both the 2.4 GHz and 3.5 GHz frequency bands, meeting basic engineering performance requirements.

[0072] The specific embodiments described herein are merely illustrative examples illustrating the spirit of the invention. The invention is not limited to the above-described embodiments. Other miniaturized multilayer capacitively coupled LTCC dual-band antennas and wireless communication terminal devices equipped with such antennas, obtained by employing the same or similar technical features as the embodiments described above, are all within the protection scope of this invention.

Claims

1. A miniaturized multilayer capacitively coupled LTCC dual-band antenna, characterized in that, It includes an LTCC substrate, four metal layers embedded in the LTCC substrate, and a feed electrode, a rear auxiliary electrode, a left ground electrode, and a right ground electrode packaged on the surface of the LTCC substrate. The LTCC substrate contains five dielectric layers: a first dielectric layer, a second dielectric layer, a third dielectric layer, a fourth dielectric layer, and a top cover dielectric layer. Of the four metal layers, the first metal layer includes a first coupling patch and a second coupling patch, the second metal layer is a third coupling patch, the third metal layer is a first radiating electrode, and the fourth metal layer is a second radiating electrode. The LTCC substrate is arranged in layers from bottom to top as follows: a first dielectric layer, a first metal layer, a second dielectric layer, a second metal layer, a third dielectric layer, a third metal layer, a fourth dielectric layer, a fourth metal layer, and a top cover dielectric layer. The first coupling patch and the second coupling patch in the first metal layer are located at the same height. The LTCC substrate has opposing front and rear faces, as well as opposing left and right faces; the power supply electrode is located on the front face of the LTCC substrate, the rear auxiliary electrode is located on the rear face of the LTCC substrate, the left ground electrode is located on the left face of the LTCC substrate, and the right ground electrode is located on the right face of the LTCC substrate; the rear auxiliary electrode has no electrical connection to any metal layer in the LTCC substrate and is only used for SMT mounting balance.

2. The miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 1, characterized in that: The thickness of each dielectric layer in the LTCC substrate is not uniform. The first dielectric layer is located at the bottom of the LTCC substrate and is used to support the first and second coupling patches. The second dielectric layer is disposed between the first and second metal layers, and its thickness determines the interlayer coupling strength between the first and third coupling patches. The third dielectric layer is disposed between the second and third metal layers, and its thickness affects the parallel plate capacitance between the third coupling patch and the first radiating electrode. The fourth dielectric layer is disposed between the third and fourth metal layers. The thickness of each dielectric layer is independently adjusted according to the target coupling coefficient and capacitance value, and the two frequency bands are independently optimized.

3. The miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 1, characterized in that: The first coupling patch is a horizontally positioned metal patch, the main body of which is a rectangular metal patch, and a rectangular connecting strip extends from one side of the main body to connect with the feed electrode; the second coupling patch is a horizontally positioned metal patch, the main body of which is a rectangular metal patch, and a rectangular connecting strip extends from one side of the main body to connect with the feed electrode; neither the first nor the second coupling patch is grounded; the third coupling patch is located vertically above the first coupling patch, the main body of which is a rectangular metal patch, and a rectangular connecting strip extends from one side of the main body to connect with the feed electrode; the third coupling patch and the first coupling patch are separated by a second dielectric layer, and their projections in the vertical direction partially overlap, forming interlayer capacitive coupling.

4. The miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 1, characterized in that: The first radiating electrode is located vertically above the third coupling patch. The third coupling patch and the first radiating electrode are separated by a third dielectric layer. The projections of the first radiating electrode and the third coupling patch in the vertical direction partially overlap, forming a parallel plate capacitor radiation structure. The first radiating electrode is a horizontally arranged rectangular metal patch with an area larger than that of the third coupling patch. The length of the first radiating electrode in the left-right direction is less than half the length of the LTCC substrate, and the width in the front-back direction is less than the width of the LTCC substrate. The first radiating electrode is not directly connected to the feed electrode, but is fed by the third coupling patch through interlayer capacitive coupling. The left end of the first radiating electrode is connected to the left ground electrode on the left end face of the LTCC substrate.

5. A miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 1, characterized in that: The second radiating electrode is located vertically above the second coupling patch, and a rectangular connecting strip extends from one side of the second radiating electrode to connect with the feeding electrode for feeding. The second radiating electrode and the second coupling patch are separated by a second dielectric layer, a third dielectric layer, and a fourth dielectric layer. Their projections in the vertical direction partially overlap, forming interlayer capacitive coupling. The second radiating electrode is an interdigitated capacitor radiating structure, including multiple alternately arranged metal fingers, which form an interdigitated capacitor. The right end of the second radiating electrode is connected to the right ground electrode on the right end face of the LTCC substrate. The first coupling patch, the second coupling patch, the third coupling patch, and the second radiating electrode are all directly physically connected and fed by a feed electrode, forming a complete feed network.

6. A miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 1, characterized in that: The first coupling patch and the third coupling patch transmit the power supply signal to the third coupling patch through interlayer capacitive coupling. The third coupling patch then couples the energy to the first radiating electrode through the parallel plate capacitance effect, thereby generating the first resonant frequency. The second coupling patch and the second radiating plate generate a second resonant frequency through interlayer capacitive coupling.

7. A miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 1, characterized in that: It also includes a test circuit board, which includes a test dielectric substrate, coplanar waveguide signal lines, impedance matching lines, metal shorting plates, a grounding pad on the left PCB, a grounding pad on the right PCB, a grounding plane, and a clearance area.

8. A miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 7, characterized in that: The test dielectric substrate, coplanar waveguide signal line and ground plane form a coplanar waveguide transmission line. The line width of the coplanar waveguide signal line is calculated based on the dielectric constant and thickness of the test dielectric substrate. The left PCB ground pad and the right PCB ground pad are symmetrically arranged and located in the ground area of ​​the test circuit board at the edge of the clearance area.

9. A miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 7, characterized in that: The clearance area is located below the antenna installation position, and the scope of the clearance area should ensure that the antenna has good radiation performance. The antenna is set across the clearance area, and the antenna feed electrode is electrically connected to the coplanar waveguide signal line through the impedance matching line. The left and right ground electrodes of the antenna are electrically connected to the ground plane of the test circuit board through the left PCB ground pad and the right PCB ground pad, respectively.

10. A miniaturized multilayer capacitively coupled LTCC dual-band antenna as described in claim 7, characterized in that: Impedance matching lines are laid horizontally on the test dielectric substrate in a zigzag shape. One end of the impedance matching line is connected to the antenna feed electrode, and the other end is connected to the coplanar waveguide signal line. The length and width of the impedance matching line segment are adjusted according to the target input impedance of the antenna to achieve good impedance matching between the antenna and the coplanar waveguide transmission line. The end of the impedance matching line closest to the coplanar waveguide signal line is shorted to the ground plane below through a metal shorting piece. The metal shorting piece is used to assist in achieving impedance matching, so that the antenna exhibits purely resistive characteristics in the operating frequency band.

Images