Ultra wide band loop antenna for wireless communication and wireless energy transceiving
By designing a loop antenna in mobile electronic devices, combining equivalent capacitive coupling elements, and exciting a multi-order degenerate mode, the problem of insufficient antenna band coverage is solved and efficient ultra-wideband band coverage is achieved.
Patent Information
- Application Number
- CN202411599229.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-01-11
- Filing Date
- 2024-11-11
- Publication Date
- 2025-07-11
AI Technical Summary
The antennas of existing mobile electronic devices are difficult to cover the entire Sub-6 GHz frequency band, and the reflection coefficient is low, resulting in insufficient efficiency.
A loop antenna is designed, including a loop part and an equivalent capacitive coupling element, and ultra-wideband frequency band coverage is achieved through excitation in multi-order degenerate mode.
A low reflection coefficient <-10 dB in the Sub-6 GHz spectrum is achieved, with a bandwidth of 158%, and a total antenna efficiency of more than 90%, without the need for complex antenna tuners.
Smart Images
Figure CN120300447A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a radio frequency antenna for a mobile electronic device, and more particularly to a loop antenna for a mobile electronic device. Background Art
[0002] Mobile electronic devices are widely used in industry and personal life, and many of these devices have wireless communication and / or wireless energy transceiver functions. Examples of these mobile electronic devices include smartphones, smart watches / bracelets, smart glasses, drones (UAVs), Internet of Things (IoT) devices, and hybrid devices with functions of multiple such devices. For devices with wireless communication and / or wireless energy transmission functions, their radio frequency modules typically cover one or more frequency bands in the Sub-6 GHz spectrum (about 700 MHz - 6 GHz) because this spectrum contains the carrier frequency bands of 2G, 3G, 4G, and Sub-6 GHz 5G, as well as some Industrial, Scientific and Medical (ISM), Global Navigation Satellite System (GNSS), Internet of Things, and other communication protocol frequency bands.
[0003] To meet the diverse needs of consumers, mobile electronic device manufacturers always strive to enable radio frequency components (such as antennas) to cover as wide a frequency band as possible. On the other hand, different from other antennas, the antenna of a mobile electronic device (mobile antenna) should have a quite small size, that is, a small projected area and an extremely low profile height.
[0004] However, there is a contradiction between the limited space reserved for the antenna and the ultra-wide frequency band required by the electronic device. This is caused by the basic rule of electromagnetics - the quality factor theory (Q-factor theory). This rule severely limits the performance of mobile antennas. Therefore, many people have started to pay attention to this problem and designed complex antenna geometries, and at the same time used high-performance antenna tuners to cover as wide a frequency band as possible. However, most existing mobile antennas can still only cover a limited part of the Sub-6 GHz spectrum, and there is still a large gap from covering the entire spectrum. For example, The 14 Pro Max contains multiple antennas and is used in conjunction with an antenna tuner to cover the 600 - 900 MHz / 1500 MHz / 1800 - 2600 MHz / 3500 - 3900 MHz / 4700 MHz frequency bands of the cellular network. Apple The Series 8 antenna covers the 700 - 850 MHz / 1800 - 2600 MHz of the cellular network. On the other hand, compared with base station antennas, mobile antennas usually can only achieve a lower standard of reflection coefficient. The reflection coefficient of a mobile antenna is usually only less than -6 dB (corresponding to an antenna total efficiency greater than 75%), while the reflection coefficient of a base station antenna is at least less than -10 dB (corresponding to an antenna total efficiency greater than 90%). Summary of the Invention
[0005] In view of the above problems, one of the objectives of the present invention is to propose a small loop antenna for mobile electronic devices that covers the entire Sub-6 GHz frequency band to alleviate this contradiction.
[0006] Therefore, in one aspect, the present invention provides a loop antenna, including a loop portion extending along a virtual closed shape, where the loop portion has an opening at a certain place and has two ends separated by a gap; and a first equivalent capacitance coupling element (eCCE) that is at least partially adjacent to the above gap. The first equivalent capacitance coupling element is connected to the loop portion near the gap.
[0007] Preferably, both the loop portion and the first equivalent capacitance coupling element are conductive strips, and they each have a surface. The surfaces of the loop portion and the first equivalent capacitance coupling element are parallel to each other.
[0008] More preferably, the surfaces of both the loop portion and the first equivalent capacitance coupling element are generally located in the same virtual plane as the virtual closed shape.
[0009] Alternatively, the surfaces of both the loop portion and the first equivalent capacitance coupling element are generally perpendicular to the virtual plane where the virtual closed shape is located.
[0010] In a specific embodiment, the virtual closed shape is circular, and the shape of the loop portion is an annular sector.
[0011] Preferably, the first equivalent capacitance coupling element is located at one of the radially inner position and the radially outer position of the loop portion.
[0012] More preferably, the loop antenna further includes a second equivalent capacitance coupling element. The second equivalent capacitance coupling element is located at the other of the radially inner position and the radially outer position of the loop portion.
[0013] More preferably, the second equivalent capacitance coupling element and the first equivalent capacitance coupling element have different lengths in the circumferential direction.
[0014] More preferably, both the second equivalent capacitance coupling element and the first equivalent capacitance coupling element are connected to the position of the loop portion near the gap.
[0015] In a specific embodiment, the midpoint of the first equivalent capacitance coupling element is connected to the loop portion.
[0016] In another specific embodiment, the loop antenna is fed at one or both of the two ends of the loop portion.
[0017] In yet another specific embodiment, the loop antenna further includes a first connection line that electrically connects the loop portion and the first equivalent capacitance coupling element. The first connection line passes near the gap.
[0018] In yet another specific embodiment, the first equivalent capacitance coupling element includes a first part and a second part, which are defined by the connection point of the first connection line and the first equivalent capacitance coupling element. The loop antenna further includes a second connection line that electrically connects the loop portion and the second equivalent capacitance coupling element. The second equivalent capacitance coupling element includes a first part and a second part, which are defined by the connection point of the second connection line and the second equivalent capacitance coupling element. The first parts of the first equivalent capacitance coupling element and the second equivalent capacitance coupling element are on the same side of the gap and have different lengths in their circumferential directions. The second parts of the first equivalent capacitance coupling element and the second equivalent capacitance coupling element are on the other side of the gap and have different lengths in their circumferential directions.
[0019] In yet another specific embodiment, the loop portion and the first equivalent capacitance coupling element are substantially parallel along their extending directions, such that the distance between the first equivalent capacitance coupling element and the loop portion is substantially constant.
[0020] In yet another specific embodiment, the loop portion and the second equivalent capacitance coupling element are substantially parallel along their extending directions, such that the distance between the second equivalent capacitance coupling element and the loop portion is substantially constant.
[0021] It can be seen that the embodiments of the present invention provide a loop antenna that supports wireless communication and wireless energy transmission and reception for mobile electronic devices in multi-band or ultra-wideband frequency bands. In addition, the loop antenna is beneficial for ultra-wideband wireless energy harvesting and ultra-wideband sensing. Thus, in the research and development process of mobile electronic devices, there is no longer a need for cumbersome and particularly careful Sub-6 GHz antenna tuning, nor most of the expensive Sub-6 GHz antenna tuners. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The above and further features of the present invention will be clearly described in the following embodiments, which are provided only as examples together with the following appendices Figure 1 as follows:
[0023] Figure 1 is a perspective view of a loop antenna according to a first embodiment of the present invention.
[0024] Figure 2 is Figure 1 a schematic diagram of the reflection coefficient of the loop antenna in the frequency domain in
[0025] Figure 3is a Smith chart showing Figure 1 the impedance matching characteristics of the loop antenna in the frequency domain in
[0026] Figure 4 is a perspective view of a loop antenna according to a second embodiment of the present invention.
[0027] Figure 5 is a perspective view of a loop antenna according to a third embodiment of the present invention.
[0028] In the drawings, the same numerals denote the same parts in the various embodiments described herein. Detailed Description
[0029] Now referring to Figure 1 , a first embodiment of the present invention is a loop antenna having a planar shape. The loop antenna includes a loop portion 20, which is the main radiator of the loop antenna and has an annular sector shape. In other words, although the loop portion 20 extends along a virtual circle 21 (i.e., a closed shape), it is not actually closed into a complete circle. Instead, the loop portion 20 is open at both ends and includes two end points 20a, 20b, and there is a gap 22 between these two end points. The loop portion 20 has a uniform width in its circumferential direction, and this width refers to the dimension of the loop portion 20 in the radial direction.
[0030] The loop antenna further includes a first eCCE 24 and a second eCCE 26, both of which are electrically connected to the loop portion 20. The first eCCE 24 and the second eCCE 26 are also referred to as "couplers". The shapes of the first eCCE 24 and the second eCCE 26 are both curved, and their curvatures are the same as that of the loop portion 20. In other words, the virtual circles (not shown) that respectively coincide with and extend in the same direction as the first eCCE 24 and the second eCCE 26 are concentric with the virtual circle 21. The lengths of the first eCCE 24 and the second eCCE 26 extending in the circumferential direction are different, and the first eCCE 24 is longer than the second eCCE 26. The first eCCE 24 is located radially outside the loop portion 20, and the second eCCE 26 is located radially inside the loop portion 20. The first eCCE 24 and the second eCCE 26 both extend together with the loop portion 20 and are completely adjacent to the loop portion 20. In fact, the first eCCE 24 and the second eCCE 26 are both parallel to the loop portion 20 and parallel to each other along their extension directions (i.e., the circumferential direction). Due to this parallel relationship, the spacing between the first eCCE 24 and the loop portion 20 is substantially constant in the length direction of the first eCCE 24. Similarly, the spacing between the second eCCE 26 and the loop portion 20 is substantially constant in the length direction of the second eCCE 26.
[0031] In Figure 1 In the exemplary embodiment shown, the loop portion 20, the first eCCE 24, and the second eCCE 26 are all single-layer, coplanar conductive strips. All of these conductive strips are also parallel to the plane in which the loop antenna lies, such as a layer (not shown) of a PCB (printed circuit board) substrate. The loop portion 20, the first eCCE 24, and the second eCCE 26 each have a top surface and a bottom surface due to their planar shape. All the top surfaces and bottom surfaces are parallel to each other, and the top surfaces are flush with each other, and so are the bottom surfaces. Since the thickness of the conductive strips is very small and can be ignored, all the top surfaces and bottom surfaces can be considered to lie within the same virtual plane (not shown), in which the virtual circle 21 lies within this plane.
[0032] The conductive strips of the loop antenna can be fabricated using different techniques, such as on one or more layers of a printed circuit board. However, those skilled in the art should realize that in other variants of the present invention, the conductive strips can be a flexible printed circuit (FPC), or part of the conductive housing structure of a mobile electronic device, or can be a metal structure, etc.
[0033] As described above, the first eCCE 24 and the second eCCE 26 are electrically connected to the loop portion 20, which is achieved by configuring the connection line 30 passing through the gap 22. As Figure 1 shown, each of the first eCCE 24 and the second eCCE 26 forms a T-shaped structure with the corresponding part of the connection line 30, which is different from a conventional capacitive coupling element (CCE), in which the traces of the coupler and the main radiator are not directly connected. Therefore, the connection line 30 can be regarded as consisting of two parts, each part being an independent connection line of its respective eCCE. Specifically, the eCCE is derived from the CCE and is usually made of a conductive strip or a conductive plate. It is an additional topological structure outside the main radiator of the antenna. It is close to and coupled with the main radiator of the antenna and has a connection point near the feeding position of the main radiator. The eCCE is usually T-shaped or its variant. It is a coupling structure and can therefore also be regarded as a coupler. Its function is to excite certain characteristic modes of the radiator. The characteristic currents of these characteristic modes have a minimum value at the connection point of the main radiator of the antenna.
[0034] The connection line 30 is also integrally formed with the annular portion 20, the first eCCE 24, and the second eCCE 26, and the connection line 30 extends radially to connect the annular portion 20, the first eCCE 24, and the second eCCE 26 together at the gap 22. It can be seen that the connection line 30 is connected to the first eCCE 24, substantially at the midpoint of the first eCCE 24 along the circumferential direction, and similarly connected to the midpoint of the second eCCE 26 along the circumferential direction. The first eCCE 24 can be regarded as consisting of two parts, bounded by the intersection of the connection line 30 and the first eCCE 24. In other words, the virtual extension line (not shown) of the connection line 30 passes through the first eCCE 24. The first part of the first eCCE 24 is on the left side of the virtual extension line, and the second part of the first eCCE 24 is on the right side of the virtual extension line. Similarly, the second eCCE 26 can be regarded as having two parts, bounded by the connection point of the connection line 30 and the second eCCE 26. The virtual extension line (not shown) of the connection line 30 passes through the second eCCE 26. The first part of the second eCCE 26 is on the left side of the virtual extension line, and the second part of the second eCCE 26 is on the right side of the virtual extension line. As Figure 1 shown, the left part of the first eCCE 24 is longer than the left part of the second eCCE 26. Similarly, the right part of the first eCCE 24 is longer than the right part of the second eCCE 26.
[0035] Figure 1 The loop antenna in Figure 1 is fed at the two end points 20a, 20b of the annular portion 20. In other words, the loop antenna is fed at the break point of its annular shape (i.e., the gap 22). Specifically, a feeding terminal 28 is disposed on each of the two end points 20a, 20b, and the feeding terminal 28 is connected to a feeding wire (not shown in
[0036] After describing the structure of the loop antenna in Figure 1 the working principle of the antenna will be introduced next. Loop antennas (such as the annular portion 20) are often used as antennas for mobile devices because they can be naturally integrated with metal casings (such as the metal frames of modern smartphones). However, traditional loop antennas themselves can only excite single resonances for each order mode, so it is difficult for traditional loop antennas to achieve a continuous reflection coefficient < -10 dB over an ultra-wide frequency band. In contrast, Figure 1The loop antenna therein includes multiple eCCEs close to the feeding position, which can excite the multi-order degenerate radiation modes inherent in the loop radiator, thereby significantly expanding the antenna bandwidth. Figure 1 The loop antenna therein can excite n-order modes: 1λ, 2λ, 3λ, 4λ... modes (λ is the waveguide wavelength), and each order of mode has double resonances, which are excited by the eCCE and the embedded port respectively. As described above, the feeder is connected to the feeding terminals 28 at both ends 20a and 20b of the loop portion 20 to feed the loop portion 20 from an external feed source. At the same time, the eCCE introduces perturbations, making the resonance frequencies of the double degenerate modes different. Therefore, Figure 1 The loop antenna therein has 2n resonances. The spacing between the 2n resonance frequencies is small enough, so the antenna can achieve a continuous ultra-wideband with a reflection coefficient < -10 dB. In this embodiment, Figure 1 the loop antenna achieves a reflection coefficient below -10 dB in the entire Sub-6 GHz spectrum (theoretically corresponding to an antenna total efficiency higher than 90%). The circumference of the loop is only one wavelength (1λ lowest ) of the lowest resonance frequency. Correspondingly, the diameter of the loop is about 0.3λ lowest . Therefore, this loop antenna is small in size and suitable for metal frame antennas of smartphones, smart watches, smart glasses and many other mobile intelligent devices.
[0037] Figure 1 The reflection coefficient of the loop antenna shown is as Figure 2 shown. Since the double degenerate modes of the first n-order resonances of the loop antenna can be excited simultaneously, a total of 2n modes of the loop antenna will be excited. Therefore, the spacing of the resonance frequencies of the excited modes is very close in the spectrum. Over a wide spectrum, the antenna matches well with a 50Ω standard RF port, as Figure 3 shown in the Smith chart. In the example, the bandwidth is 721 MHz - 6197 MHz, and the relative bandwidth is as high as 158%, that is, 8.6 octaves. This bandwidth is significantly wider than that of traditional loop antennas.
[0038] Figure 4 shows a loop antenna according to another embodiment of the present invention. The structure and components of this loop antenna are substantially similar to those in Figure 1 , and for the sake of brevity, they will not be described again, but only the differences between the loop antenna in Figure 4 and the loop antenna in Figure 1 will be described. Specifically, in Figure 4 , the loop portion 120, the first eCCE 124 and the second eCCE 126, and the connection line 130 are also conductive strips, but their orientations are different compared with the corresponding components in Figure 1 . From Figure 4It can be seen that all the top surfaces and bottom surfaces of the loop portion 120, the first eCCE 124, the second eCCE 126, and the connection line 130 are substantially perpendicular to the virtual plane in which the virtual closed loop (not shown) lies. Therefore, the top surface and the bottom surface of the conductive strip are substantially perpendicular to the antenna placement plane. In addition, it can be seen that the lengths of the left portions (substantially defined by the connection line 130) of the first eCCE 124 and the second eCCE 126 are not equal. Similarly, the lengths of the right portions of the first eCCE 124 and the second eCCE 126 are not equal. In addition, the connection line 130 is not connected to the midpoint of the second eCCE 126.
[0039] Figure 5 A loop antenna according to another embodiment of the present invention is shown, which can be connected to a circuit (not shown) of a mobile electronic device. The structure and components of the loop antenna are substantially similar to those in Figure 1 and will not be described in detail for the sake of brevity, but only the differences between the loop antenna in Figure 5 and the loop antenna in Figure 1 will be described. Specifically, for the loop antenna in Figure 5 , the connection line 230 is not connected to the midpoints of the first eCCE 224 and the second eCCE 226. Instead, the connection position between the first eCCE 224 and the connection line 230 is offset from the center of the first eCCE 224 along its length direction. Similarly, the connection position of the second eCCE 226 and the connection line 230 is offset from the center of the length direction of the second eCCE 226. In addition, the width of the second eCCE 226 is significantly greater than the widths of the loop portion 200 and the first eCCE 224. Finally, two feeder lines 232 are shown in the figure connected to the feeding terminals 228 at both ends of the loop portion 200. In addition, it can be seen that the lengths of the left portions (substantially defined by the connection line 230) of the first eCCE 224 and the second eCCE 226 are not equal. Similarly, the lengths of the right portions of the first eCCE 224 and the second eCCE 226 are not equal. In addition, the connection line 230 is not connected to the midpoint of the second eCCE 226, and the connection line 230 is not connected to the midpoint of the first eCCE 224.
[0040] Therefore, the above embodiments of the present invention have been fully described. Although specific embodiments are mentioned in the description, those skilled in the art will clearly recognize that the present invention can be implemented in variations of these specific details. Therefore, the present invention should not be construed as being limited to the embodiments set forth herein.
[0041] Although the embodiments have been described in detail in the drawings and the foregoing description, they should be regarded as illustrative rather than restrictive, as only exemplary embodiments are shown and the scope of the present invention is not limited in any way. It is understood that any feature described herein can be used in combination with any embodiment. The illustrative embodiments are not mutually exclusive, nor do they exclude other embodiments not described in this specification. Accordingly, the present invention also provides embodiments comprising combinations of one or more of the above-described illustrative embodiments. Modifications and variations can be made to the invention described in this specification without departing from the spirit and scope of the present invention, and thus only the limitations set forth in the appended claims should be imposed.
[0042] For example, in Figure 1 、 4 and the embodiment shown in 5, the two eCCEs are in the same plane as the annular portion, and their respective surfaces are flush with each other. However, in a variant of the preferred embodiment of the present application, the eCCE can be perpendicular to the annular portion or at any other angle with respect to the annular portion. In these cases, not the entire eCCE can be considered adjacent to the annular portion, but in any case, at least the portion of the eCCE close to the connection line with the annular portion is adjacent to the annular portion.
[0043] Furthermore, the loop antenna (especially its annular portion) in the above-described exemplary embodiments is in the shape of an annular sector. Those of ordinary skill in the art should recognize that the above-described generally circular shape is not necessary, but the annular portion can also be other approximately closed topological structures, such as an ellipse, a rectangle or a rounded rectangle curve, a spectacle lens frame, etc. The term "annular" used in this specification only means that the shape is approximately closed, but does not limit the shape to be annular.
[0044] In Figure 1 、 4 and the embodiment of 5, two eCCEs are configured in the loop antenna. In other variants of the preferred embodiment, there can also be more or fewer eCCEs in the loop antenna.
[0045] The antenna described in the above embodiments can be used as an antenna element of an antenna array or a multiple-input multiple-output (MIMO) antenna. An antenna array or a multiple-input multiple-output antenna obtained by repeating the antenna described in the above embodiments still falls within the scope of the present invention. For example, Figure 1 the annular portion in can be modified to have a plurality of gaps, and additional eCCEs can be configured near the additional gaps to construct additional antenna elements.
Claims
1. A loop antenna, comprising: A loop portion extending along a virtual closed shape, the loop portion having an open end and having two ends separated by a gap; A first equivalent capacitance coupling element at least partially adjacent to the gap; Wherein the first equivalent capacitance coupling element is electrically connected to the loop portion near the gap.
2. The loop antenna according to claim 1, wherein both the loop portion and the first equivalent capacitance coupling element are conductive strips and each has a surface; the surfaces of the loop portion and the first equivalent capacitance coupling element are parallel to each other.
3. The loop antenna according to claim 2, wherein the surfaces of the loop portion and the first equivalent capacitance coupling element are substantially located in the same virtual plane as the virtual closed shape.
4. The loop antenna according to claim 2, wherein the surfaces of the loop portion and the first equivalent capacitance coupling element are substantially perpendicular to the virtual plane in which the virtual closed shape lies.
5. The loop antenna according to claim 1, wherein the virtual closed shape is circular; the shape of the loop portion is an annular sector.
6. The loop antenna according to claim 5, wherein the first equivalent capacitance coupling element is located at one of a radially inner position and a radially outer position of the loop portion.
7. The loop antenna according to claim 6, further comprising a second equivalent capacitance coupling element located at the other of the radially inner position and the radially outer position of the loop portion.
8. The loop antenna according to claim 7, wherein both the second equivalent capacitance coupling element and the first equivalent capacitance coupling element are electrically connected to the loop portion near the gap.
9. The loop antenna according to claim 1, wherein the loop antenna is fed at one or both of the two ends of the loop portion.
10. The loop antenna according to claim 1, further comprising a first connection line that electrically connects the loop portion and the first equivalent capacitance coupling element; the first connection line passes near the gap.
11. The loop antenna according to claim 10, wherein the first equivalent capacitance coupling element includes a first portion and a second portion defined by a connection point of the first connection line and the first equivalent capacitance coupling element; the loop antenna further comprises a second connection line that electrically connects the loop portion and the second equivalent capacitance coupling element; the second equivalent capacitance coupling element includes a first portion and a second portion, and the second portion is defined by a connection point of the second connection line and the second equivalent capacitance coupling element; the first portions of the first equivalent capacitance coupling element and the second equivalent capacitance coupling element have different lengths in their circumferential directions; the second portions of the first equivalent capacitance coupling element and the second equivalent capacitance coupling element have different lengths in their circumferential directions.
12. The loop antenna according to claim 2, wherein the annular portion and the first equivalent capacitive coupling element are substantially parallel along their extending directions, such that the distance between the first equivalent capacitive coupling element and the annular portion is substantially unchanged.
13. The loop antenna according to claim 7, wherein the annular portion and the second equivalent capacitive coupling element are substantially parallel along their extending directions, such that the distance between the second equivalent capacitive coupling element and the annular portion is substantially unchanged.