Wideband Elliptical Microstrip Antenna for Indoor Communication

Abstract

The present invention provides a broadband elliptical microstrip antenna suitable for indoor communication, which includes a dielectric substrate. A grounding metal plate is provided on the bottom surface of the dielectric substrate, and a metal patch is provided on the top surface of the dielectric substrate. It also includes an elliptical slot, a stub, a first shorting wall, a second shorting wall, a third shorting wall, an annular capacitive slot, a radio frequency connector, a first rectangular narrow slot, and a second rectangular narrow slot. The metal patch is semi-elliptical, an elliptical slot is provided in the middle of the metal patch, a first shorting wall is provided on the straight edge of the metal patch, and a second shorting wall and a third shorting wall are respectively provided at both ends of the elliptical arc edge of the metal patch. The grounding metal plate is provided with a first rectangular narrow slot and a second rectangular narrow slot. The present invention has the advantages of compact size, low profile, low cost, wide bandwidth, small gain fluctuation in the passband during multi-mode coupling, and stable gain within the impedance bandwidth, and is suitable for indoor scenarios.

Description

Technical Field

[0001] The present invention relates to a broadband elliptical microstrip antenna suitable for indoor communication, belonging to the technical field of antennas. Background Art

[0002] As an important transmitting and receiving unit of many terminal devices, microstrip antennas play an important role in modern communication systems. Due to the end-fire characteristics of microstrip patch antennas, they can be used as wall-mounted devices on walls and ceilings, and are very suitable for small indoor communication application scenarios, especially small supermarkets, stores, offices, and meeting rooms.

[0003] However, microstrip antennas are also limited by some defects, especially their narrow bandwidth. To address the above problems, in order to achieve a broadband microstrip patch antenna, the thickness of the microstrip patch antenna profile can be increased. As the thickness increases, the antenna impedance bandwidth can be effectively broadened. However, unfortunately, the increase in profile thickness will also introduce surface waves, reducing the antenna efficiency, and with the increase in thickness, the antenna is not conducive to conformal shaping. In addition, when existing microstrip antennas are in multimode coupling, the gain fluctuation in the passband is relatively large.

[0004] The above problems should be considered and solved in the design and production process of a broadband elliptical microstrip antenna suitable for indoor communication. Summary of the Invention

[0005] The purpose of the present invention is to provide a broadband elliptical microstrip antenna suitable for indoor communication to solve the problems in the prior art, such as narrow bandwidth, large profile thickness caused by achieving a large bandwidth, and large gain fluctuation in the passband during multimode coupling.

[0006] The technical solution of the present invention is as follows:

[0007] A broadband elliptical microstrip antenna suitable for indoor communication includes a dielectric substrate. A ground metal plate is provided on the bottom surface of the dielectric substrate, and a metal patch is provided on the top surface of the dielectric substrate. It also includes an elliptical slot, a stub, a first shorting wall, a second shorting wall, a third shorting wall, an annular capacitive slot, a radio frequency connector, a first rectangular narrow slot, and a second rectangular narrow slot. The metal patch is semi-elliptical. An elliptical slot is provided in the middle of the metal patch. A first shorting wall is provided on the straight edge of the metal patch. Second and third shorting walls are respectively provided at both ends of the elliptical arc edge of the metal patch. The metal patch is provided with an annular capacitive slot, and the annular capacitive slot is provided between the first shorting wall and the elliptical slot. A radio frequency connector is provided in the annular capacitive slot. The radio frequency connector passes through the dielectric substrate, and both ends of the radio frequency connector are respectively connected to the metal patch and the ground metal plate. A stub is provided on the side of the elliptical slot; the ground metal plate is provided with a first rectangular narrow slot and a second rectangular narrow slot.

[0008] Furthermore, the elliptical slot is used to achievee TM 31 mode and e TM 51 mode coupling, the first rectangular slot and the second rectangular slot are used to increase e TM 12 mode electrical length and e TM 12 mode frequency point is pulled into e TM 31 and e TM 51 two modes to form a triple-mode resonance enhanced bandwidth.

[0009] Furthermore, an elliptical slot is loaded at the center of the metal patch e TM 51 the zero-value point of the mode electric field, i.e., the electric wall, e TM 31 the peak value of the mode electric field, i.e., the magnetic wall, and the minor axis of the elliptical slot coincides with the major axis of the metal patch.

[0010] Furthermore, along the e TM 12 two symmetric zero-value points of the mode electric field, i.e., the electric walls, on the grounded metal plate are respectively provided with a first rectangular slot and a second rectangular slot, and the first rectangular slot and the second rectangular slot are parallel to the e TM 31 and e TM 51 mode current distributions.

[0011] Furthermore, the first short circuit wall, the second short circuit wall and the third short circuit wall are used to eliminate e TM 31 and e TM 51 the out-of-phase magnetic current elements of the mode and are used to complete e TM 31 and e TM 51 mode and e TM 12 mode current orthogonalization processing.

[0012] Furthermore, a number of first metal cylindrical through holes are provided on the straight edge of the metal patch, and the first metal cylindrical through holes pass through the dielectric substrate to connect to the grounded metal plate to form the first short circuit wall; at both ends of the elliptical arc edge of the metal patch, a number of second metal cylindrical through holes and a number of third metal cylindrical through holes are respectively provided, and the second metal cylindrical through holes pass through the dielectric substrate to connect to the grounded metal plate to form the second short circuit wall, and the third metal cylindrical through holes pass through the dielectric substrate to connect to the grounded metal plate to form the third short circuit wall.

[0013] Further, the first metal cylinders are arranged in a straight line, and the through-holes of the second and third metal cylinders are both arranged in an elliptical arc shape. The through-holes of the second and third metal cylinders are symmetrically loaded starting from the straight edge of the metal patch and along the elliptical arc edge. The specific numbers of the through-holes of the first, second, and third metal cylinders are determined according to the electromagnetic simulation software. e TM 31 、 e TM 51 and e TM 12 mode current distributions, that is, when e TM 31 、 e TM 51 mode currents are orthogonal to e TM 12 mode currents, the loading is stopped.

[0014] Further, the stub is used to improve the gain of the e TM 31 mode within the radiation passband. The stub is arranged on the magnetic wall boundary of the e TM 31 mode.

[0015] Further, the process of determining the length of the stub is as follows: by increasing the length of the stub until the difference between the maximum and minimum values of the gain within the entire passband obtained by the electromagnetic simulation software is within the set value, then stop increasing and determine the length of the stub.

[0016] Further, the semi-major axis length a of the metal patch is 0.474λ0, the eccentricity e is 0.38; the minor axis length W1 of the elliptical slot is W1 = 0.122λ0, and the major axis length is L1: L1 = 0.395λ0; the lengths of the first and second rectangular slots are L3 = 0.304λ0, where λ0 is the wavelength corresponding to the center frequency of the antenna operation, the stub length L2 = 0.049λ0, the diameter of the annular capacitive slot is 0.08λ0, the width of the annular capacitive slot is 0.12 mm, and the overall antenna formed by the dielectric substrate, the ground metal plate, and the metal patch is rectangular with dimensions of 0.73λ0 × 0.949λ0 × 0.049λ0. The dielectric substrate uses a polytetrafluoroethylene glass cloth copper-clad laminate F4B, with a relative dielectric constant of ε r = 3.55 and a loss tangent value of tanδ = 0.002.

[0017] The beneficial effects of the present invention are:

[0018] 1. A broadband elliptical microstrip antenna suitable for indoor communication, which is compact in size and has the advantages of low profile, low cost, wide bandwidth, small gain fluctuation in the passband during multimode coupling, and stable gain within the impedance bandwidth, and is suitable for indoor scenarios.

[0019] 2. The broadband elliptical microstrip antenna suitable for indoor communication can achieve e TM 12 mode, e TM 31 mode and e TM 51 mode coupling of three modes. By using the e TM 12 , e TM 31 and e TM 51 modes of the semi-elliptical patch antenna as the working modes of multimode coupling, an enhanced impedance bandwidth can be achieved.

[0020] 3. In the present invention, an elliptical slot is loaded at the peak of the electric field of the e TM 31 mode, that is, at the magnetic wall, and at the zero point of the electric field of the e TM 51 mode, that is, at the electric wall, so as to complete the e TM 31 and e TM 51 mode frequency point coupling; on the ground metal plate, a first rectangular slender slot and a second rectangular slender slot are opened at two symmetric virtual electric walls of the e TM 12 mode, and the e TM 12 mode frequency point is pulled into the e TM 31 and e TM 51 mode middle to complete the coupling of three modes.

[0021] 4. For the broadband elliptical microstrip antenna suitable for indoor communication, the elliptical arc edge of the metal patch is sequentially loaded with a second metal through hole and a third metal through hole, which can eliminate the e TM 31 and e TM 51 mode anti-phase magnetic current elements, eliminate the beam in the sidelobe direction of the high-order mode, and improve the main polarization gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FIG. is a schematic structural diagram of a broadband elliptical microstrip antenna suitable for indoor communication according to an embodiment of the present invention;

[0023] Figure 2 It is a schematic structural diagram of the grounding metal plate, the first rectangular elongated slot, and the second rectangular elongated slot in the embodiment;

[0024] Figure 3 It is a schematic cross-sectional structural diagram of the wideband elliptical microstrip antenna applicable to indoor communication in the embodiment;

[0025] Figure 4 It is in the embodiment e TM 31 mode and e TM 51 mode of the electric field distribution schematic diagram, where (a) is the e TM 31 mode of the electric field distribution schematic diagram, (b) is the e TM 51 mode of the electric field distribution schematic diagram.

[0026] Figure 5 It is a schematic diagram for explaining the loading directions of the second metal cylindrical through hole and the third metal cylindrical through hole in the embodiment.

[0027] Figure 6 It is in the embodiment after loading the second metal cylindrical through hole and the third metal cylindrical through hole e TM 31 , e TM 12 , e TM 51 mode of the current distribution schematic diagram, where (a) is the e TM 31 mode of the current distribution schematic diagram, (b) is the e TM 12 mode of the current distribution schematic diagram, (c) is the e TM 51 mode of the current distribution schematic diagram.

[0028] Figure 7 It is a schematic physical reference diagram of the wideband elliptical microstrip antenna applicable to indoor communication in the embodiment;

[0029] Figure 8 It is a schematic diagram of the simulation and measured reflection coefficient frequency response curves of the wideband elliptical microstrip antenna applicable to indoor communication in the embodiment;

[0030] Figure 9 It is a schematic diagram of the simulation and measured gain frequency response curves of the wideband elliptical microstrip antenna applicable to indoor communication in the embodiment;

[0031] Figure 10Schematic diagram of comparison between simulated and measured radiation patterns of a broadband elliptical microstrip antenna applicable to indoor communication. Among them, (a) is the simulated radiation pattern of the E-plane at the mode frequency point of 5.21 GHz, (b) is the simulated radiation pattern of the H-plane at the mode frequency point of 5.21 GHz, (c) is the measured radiation pattern of the E-plane at the mode frequency point of 5.21 GHz, (d) is the measured radiation pattern of the H-plane at the mode frequency point of 5.21 GHz, (e) is the simulated radiation pattern of the E-plane at the mode frequency point of 5.45 GHz, (f) is the simulated radiation pattern of the H-plane at the mode frequency point of 5.45 GHz, (g) is the measured radiation pattern of the E-plane at the mode frequency point of 5.45 GHz, (h) is the measured radiation pattern of the H-plane at the mode frequency point of 5.45 GHz, (i) is the simulated radiation pattern of the E-plane at the mode frequency point of 5.74 GHz, (j) is the simulated radiation pattern of the H-plane at the mode frequency point of 5.74 GHz, (k) is the measured radiation pattern of the E-plane at the mode frequency point of 5.74 GHz, (l) is the measured radiation pattern of the H-plane at the mode frequency point of 5.74 GHz;

[0032] Wherein: 1 - dielectric substrate, 2 - grounded metal plate, 3 - metal patch, 4 - elliptical slot, 5 - stub, 6 - first metal cylindrical through hole, 7 - second metal cylindrical through hole, 8 - third metal cylindrical through hole, 9 - circular ring-shaped capacitive slot, 10 - RF connector, 11 - first rectangular narrow slot, 12 - second rectangular narrow slot. Specific implementation mode

[0033] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] Embodiment

[0035] A broadband elliptical microstrip antenna applicable to indoor communication, as shown in Figure 1 and Figure 2 , includes a dielectric substrate 1, a grounded metal plate 2 is provided on the bottom surface of the dielectric substrate 1, a metal patch 3 is provided on the top surface of the dielectric substrate 1, and further includes an elliptical slot 4, a stub 5, a first short circuit wall, a second short circuit wall, a third short circuit wall, a circular ring-shaped capacitive slot, an RF connector 10, a first rectangular narrow slot 11 and a second rectangular narrow slot 12. The metal patch 3 is semi-elliptical, an elliptical slot 4 is provided in the middle of the metal patch 3, a first short circuit wall is provided on the straight edge of the metal patch 3, second and third short circuit walls are respectively provided at both ends of the elliptical arc edge of the metal patch 3. The metal patch 3 is provided with a circular ring-shaped capacitive slot, and the circular ring-shaped capacitive slot is arranged between the first short circuit wall and the elliptical slot 4. An RF connector 10 is arranged in the circular ring-shaped capacitive slot. The RF connector 10 passes through the dielectric substrate 1, and both ends of the RF connector 10 are respectively connected to the metal patch 3 and the grounded metal plate 2. A stub 5 is provided on the side of the elliptical slot 4; the grounded metal plate 2 is provided with a first rectangular narrow slot 11 and a second rectangular narrow slot 12.

[0036] The broadband elliptical microstrip antenna applicable to indoor communication has a compact size and has the advantages of low profile, low cost, broadband, small gain fluctuation in the passband during multimode coupling, and stable gain within the impedance bandwidth, and is applicable to indoor scenarios.

[0037] The broadband elliptical microstrip antenna applicable to indoor communication, the elliptical slot 4 is used to achieve e TM 31 mode and e TM 51 mode coupling, the first rectangular slot 11 and the second rectangular slot 12 are used to increase e TM 12 mode electrical length and pull e TM 12 mode frequency points into e TM 31 and e TM 51 two modes to form a triple-mode resonance enhanced bandwidth. The broadband elliptical microstrip antenna applicable to indoor communication uses the e TM 12 、 e TM 31 and e TM 51 modes as the working modes of multimode coupling, and can achieve an enhanced impedance bandwidth.

[0038] Such as Figure 1 , the first shorting wall, the second shorting wall and the third shorting wall are used to eliminate e TM 31 and e TM 51 mode's anti-phase magnetic current element and are used to complete e TM 31 and e TM 51 mode and e TM 12 mode's current orthogonalization process. The straight edge of the metal patch 3 is provided with a number of first metal cylinder 6 through holes, and the first metal cylinder 6 through holes pass through the dielectric substrate 1 to connect to the ground metal plate 2 to form the first shorting wall; both ends of the elliptical arc edge of the metal patch 3 are respectively provided with a number of second metal cylinder through holes 7 and a number of third metal cylinder through holes 8, the second metal cylinder 7 through holes pass through the dielectric substrate 1 to connect to the ground metal plate 2 to form the second shorting wall, and the third metal cylinder through holes 8 pass through the dielectric substrate 1 to connect to the ground metal plate 2 to form the third shorting wall.

[0039] Such as Figure 5 and Figure 6, the first metal cylinders 6 are arranged in a straight line, and the second metal cylinders 7 and the through-holes of the third metal cylinders 8 are arranged in an elliptical arc. As Figure 5 shown by the arrow direction in, the through-holes of the second metal cylinders and the through-holes of the third metal cylinders are symmetrically loaded starting from the straight edge of the metal patch and along the elliptical arc edge respectively. The specific numbers of the through-holes of the first metal cylinders 6, the through-holes of the second metal cylinders 7, and the through-holes of the third metal cylinders 8 are obtained according to the electromagnetic simulation software e TM 31 、 e TM 51 and e TM 12 mode current distributions, that is, when e TM 31 、 e TM 51 mode current is orthogonal to e TM 12 mode current, the loading stops. As Figure 6 shown by the arrow directions in (a), (b), and (c) in, the through-holes of the first metal cylinders 6 are sequentially loaded along the straight edge of the metal patch 3. The diameter R1 of the through-holes of the first metal cylinders 6 is 0.8 mm, the spacing of the through-holes of the first metal cylinders 6 is 0.1 mm, and the distance from the straight edge of the metal patch 3 is 0.25 mm. The through-holes of the second metal cylinders 7 and the through-holes of the third metal cylinders 8 are sequentially loaded along the metal patch 3. The distance between the two boundaries of the two metal cylinder through-holes is 0.4 mm, and the distance from the elliptical arc boundary of the metal patch 3 is 0.25 mm. They are symmetrically distributed up and down.

[0040] As Figure 4 shown in (a) and (b) in, the elliptical slot 4 is loaded at the center of the metal patch 3 e TM 51 mode electric field zero-value point, that is, at the electric wall, e TM 31 mode electric field peak value, that is, at the magnetic wall, and the minor axis of the elliptical slot 4 coincides with the major axis of the metal patch 3. Figure 4 In, the leftmost color bar increases in electric field from bottom to top. The color at the bottom is the weak or zero electric field at the electric wall, and the color at the top is the strong electric field at the magnetic wall.

[0041] The major axis of the elliptical slot 4 basically coincides with the straight line where the electric wall is located to maximize the e TM 51 mode electrical length and reduce the e TM 31 mode electrical length. At the same time, due to e TM 12 mode current and e TM 51 mode, e TM 31The mode currents are orthogonal and their electrical lengths are almost constant. Since e TM 51 the electrical length of the mode increases while e TM 31 the electrical length of the mode decreases. When the major axis length of the elliptical slot 4 reaches a certain extent, e TM 31 and e TM 51 the modes complete coupling. The minor axis length W1 of the elliptical slot 4 is: W1 = 0.122λ0, and the major axis length is L1: L1 = 0.395λ0, where λ0 is the wavelength corresponding to the center frequency at which the antenna operates.

[0042] As Figure 2 , by setting the first rectangular slender slot and the second rectangular slender slot on the ground metal plate 2, the cross-polarization side-lobe level of the antenna can be effectively reduced. Along the e TM 12 two symmetric electric field null points of the mode, i.e., at the electric walls, the first rectangular slender slot 11 and the second rectangular slender slot 12 are respectively provided. The first rectangular slender slot 11 and the second rectangular slender slot 12 are parallel to the e TM 31 and e TM 51 mode current distributions and will not disturb the e TM 31 and e TM 51 modes.

[0043] As Figure 1 , the stub 5 is used to enhance the e TM 31 mode gain within the radiation passband. By loading a stub 5 on the right magnetic wall boundary of the elliptical slot 4, the equivalent magnetic current element intensity at the right magnetic wall position of the elliptical slot 4 in the e TM 31 mode can be greatly increased, while the equivalent magnetic current element intensity of the left magnetic wall is reduced. At this time, the magnetic current element intensity for radiation of the metal patch 3 will be significantly enhanced, thereby enhancing the gain within the passband. By increasing the length of the stub 5, the intensity of the equivalent magnetic current on the right side of the elliptical slot 4 is continuously increased, while the intensity of the equivalent magnetic current on the left side is continuously reduced. By observing the relationship between the passband gain size formed by the entire radiation mode and the length of the stub 5 through electromagnetic simulation software, when the difference between the maximum value and the minimum value of the passband gain size is controlled within the set value of 3 dBi, stop increasing the length of the stub 5 to achieve stable gain within the impedance bandwidth.

[0044] As Figure 1 and Figure 7, for the broadband elliptical microstrip antenna applicable to indoor communication, the lengths of the first rectangular slot 11 and the second rectangular slot 12 are L3 = 0.304λ0, where λ0 is the wavelength corresponding to the center frequency at which the antenna operates. The semi-major axis length a of the metal patch 3 is 0.474λ0 and the eccentricity e is 0.38; the length L2 of the stub 5 is 0.049λ0, the diameter of the annular capacitive slot 9 is 0.08λ0, and the width of the annular capacitive slot is 0.12 mm. The overall antenna formed by the dielectric substrate 1, the grounded metal plate 2, and the metal patch 3 is rectangular with dimensions of 0.73λ0 × 0.949λ0 × 0.049λ0. The dielectric substrate 1 is made of a copper-clad Teflon fiberglass board F4B with a relative dielectric constant of ε r = 3.55 and the loss tangent value is tanδ = 0.002.

[0045] As Figure 3 , for the broadband elliptical microstrip antenna applicable to indoor communication, the overall cross-sectional structure is divided into three layers, including the upper metal patch 3, the middle dielectric substrate 1, and the lower grounded metal plate 2; the metal patch 3 is semi-elliptical and is the main part of the antenna participating in radiation. For the broadband elliptical microstrip antenna applicable to indoor communication, in order to achieve an enhanced impedance bandwidth, the e TM 12 , e TM 31 and e TM 51 modes are used as the working modes for multimode coupling. First, in order to eliminate the beam in the sidelobe direction of the higher-order mode and increase the main polarization gain, it is necessary to eliminate the e TM 31 and e TM 51 mode's out-of-phase magnetic current elements. Therefore, the approach taken is to sequentially load a number of short-circuit metal vias along the elliptical arc segment of the semi-elliptical patch to complete this operation. Second, in order to complete the e TM 31 and e TM 51 mode frequency point coupling, an elliptical slot 4 is loaded at the center of the metal patch 3 where the e TM 31 mode electric field peak (magnetic wall), which is also the e TM 51 mode electric field zero point (electric wall). By fixing the minor axis length and continuously increasing the major axis length, the e TM 31 and e TM 51 two-mode coupling is completed. Finally, by e TM 12Two symmetrical virtual electric walls of the mode are provided with two rectangular slender slots, namely a first rectangular slender slot and a second rectangular slender slot. By increasing the lengths of the two rectangular slender slots, finally e TM 12 mode frequency points are pulled into e TM 31 and e TM 51 mode middle to complete the coupling of three modes. By providing an annular capacitive slot at the feeding position of the metal patch 3, the parasitic inductance of the whole antenna is eliminated to complete impedance matching.

[0046] For this low-profile triple-mode broadband elliptical patch antenna, the three radiation modes e TM 12 , e TM 51 and e TM 32 are described as follows: The modes of a circular patch antenna are generally TM mn , where m is the radial wave number and n is the angular wave number. The modes of an elliptical patch antenna are slightly different from those of a circular patch and are divided into two types, namely e TM mn and o TM mn . This is because when one diameter of the circular patch is used as the major axis and the other perpendicular diameter is used as the minor axis to increase its eccentricity, the circle will become an ellipse. Since the major axis is longer than the minor axis, the mode TM mn of the original circular patch antenna will be divided into e TM mn and o TM mn two modes, that is, TM mn is divided into e TM mn and o TM mn , and e TM mn and o TM mn modes are perpendicular to each other. Here, e at the lower left corner is "even", which is the mode type obtained from the solutions of the radial and angular Mathieu even functions of the elliptical patch antenna, and o is "odd", the odd solution is the mode type obtained from the solutions of the radial and angular Mathieu odd functions of the elliptical patch antenna. The radial function of the internal field in the circular patch is the Bessel function with only one type of solution, so there is no subscript e or o at the lower left corner. Therefore e TM 12 , e TM 31 and e TM 51 modes are the three modes of the elliptical patch antenna.

[0047] The broadband elliptical microstrip antenna applicable to indoor communication adopts a coaxial single-feed form, and an annular capacitive slot 9 is loaded at the feeding position on the surface of the metal patch 3. By introducing the elliptical slot 4, the e TM 31 、 e TM 51 coupling of two modes is completed. On the ground metal plate 2 e TM 12 at the electric field zero point (electric wall) of the mode, two rectangular narrow slots are loaded, and the e TM 12 mode frequency point is pulled into the e TM 31 、 e TM 51 middle of two modes to complete the three-mode coupling, effectively expanding the impedance bandwidth of the elliptical patch antenna. By introducing a stub 5, the gain within the entire passband is increased.

[0048] The broadband elliptical microstrip antenna applicable to indoor communication realizes the elimination of the antenna's anti-phase magnetic current (rectification operation) by loading a short-circuit wall on the elliptical arc of the metal patch 3, for enhancing e TM 31 and e TM 51 the main radiation direction gain of two radiation modes and reducing the cross-polarization side-lobe level. By loading the elliptical slot 4, the e TM 31 and e TM 51 coupling of two radiation modes forms a dual-mode broadband. By loading two rectangular narrow slots on the ground metal plate 2, the e TM 12 mode can be pulled into the middle of two radiation modes to form a three-mode broadband elliptical microstrip antenna.

[0049] The broadband elliptical microstrip antenna applicable to indoor communication can achieve a broadband while maintaining the low profile of the patch antenna. It can excite multiple resonant modes of the patch antenna and pull the multiple resonant modes closer to form a multi-mode resonance enhanced bandwidth. The broadband elliptical microstrip antenna applicable to indoor communication, when combined with the multi-mode resonance technology, the resulting multi-mode broadband elliptical microstrip patch antenna is also very suitable for the broadband application scenarios in modern communication systems.

[0050] Figure 8 is a schematic diagram of the echo loss frequency response characteristic curve of the broadband elliptical microstrip antenna applicable to indoor communication in the embodiment. From Figure 8It can be seen that the electromagnetic simulation frequency curve and the measured curve are basically in agreement, and there are three frequency points in the impedance bandwidth. The relative bandwidth of the simulation is 13.23% (5.15 GHz - 5.88 GHz), and the relative bandwidth of the measurement is 13.52% (5.1 GHz - 5.85 GHz). The experimental results verify that the antenna has the impedance bandwidth characteristic of broadband.

[0051] Figure 9 It is a schematic diagram of the simulation and measured gain frequency response characteristics curves of the broadband elliptical microstrip antenna applicable to indoor communication in the embodiment. Figure 7 It can be seen that the electromagnetic simulation frequency curve and the measured curve are in good agreement. Due to many errors in the printing, processing, welding, and testing processes, the measured gain values of the three modes of the antenna at their respective frequency points are 5.45 dBi, 6.85 dBi, and 7.41 dBi respectively, while the gains obtained by electromagnetic simulation are 5.64 dBi, 7.2 dBi, and 7.72 dBi respectively. The measurement is about 0.3 dBi lower than the simulation.

[0052] Figure 10 It is a schematic diagram of the comparison of the simulation and measured radiation patterns of the broadband elliptical microstrip antenna applicable to indoor communication in the embodiment. Figure 10 From the comparison of the simulation and measured radiation patterns at the three frequency points 5.21 GHz, 5.45 GHz, and 5.74 GHz in (a) - (l) of it, it can be found that at the three frequency points of the three modes, it shows the radiation characteristic of the broadside, and all show a single beam, and the cross-polarization level is small.

[0053] This kind of broadband elliptical microstrip antenna applicable to indoor communication has e TM 12 、 e TM 31 and e TM 51 three mode frequency points, and the bandwidth reaches 13.52%, which can be well applied in broadband indoor communication systems. This antenna has the advantages of small size, small profile thickness, broadband, small gain fluctuation in the passband during multimode coupling, stable gain within the impedance bandwidth, simple feeding form, convenient processing, and low cost.

[0054] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made to the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the present invention.

Claims

1. A broadband elliptical microstrip antenna suitable for indoor communication, comprising a dielectric substrate, a ground metal plate is provided on the bottom surface of the dielectric substrate, and a metal patch is provided on the top surface of the dielectric substrate, characterized in that: It also includes an elliptical groove, a stub, a first short - circuit wall, a second short - circuit wall, a third short - circuit wall, an annular - shaped groove, a radio - frequency connector, a first rectangular narrow groove, and a second rectangular narrow groove. The metal patch is semi - elliptical, and an elliptical groove is provided in the middle of the metal patch. The elliptical groove is used to achieve e TM 31 mode and e TM 51 mode coupling. The first rectangular narrow groove and the second rectangular narrow groove are used to increase e TM 12 mode electrical length and pull e TM 12 mode frequency points into e TM 31 and e TM 51 two modes to form a triple - mode resonance enhanced bandwidth. A first short - circuit wall is provided on the straight edge of the metal patch. Second and third short - circuit walls are respectively provided at both ends of the elliptical arc edge of the metal patch. The metal patch is provided with an annular - shaped accommodating groove, and the annular - shaped accommodating groove is arranged between the first short - circuit wall and the elliptical groove. A radio - frequency connector is provided in the annular - shaped accommodating groove. The radio - frequency connector passes through the dielectric substrate, and both ends of the radio - frequency connector are respectively connected to the metal patch and the ground metal plate. A stub is provided on the side of the elliptical groove; the ground metal plate is provided with a first rectangular narrow groove and a second rectangular narrow groove; a number of first metal cylindrical through - holes are provided on the straight edge of the metal patch. The first metal cylindrical through - holes pass through the dielectric substrate and are connected to the ground metal plate to form the first short - circuit wall; a number of second metal cylindrical through - holes and a number of third metal cylindrical through - holes are respectively provided at both ends of the elliptical arc edge of the metal patch. The second metal cylindrical through - holes pass through the dielectric substrate and are connected to the ground metal plate to form the second short - circuit wall, and the third metal cylindrical through - holes pass through the dielectric substrate and are connected to the ground metal plate to form the third short - circuit wall; the first metal cylinders are arranged in a straight line, and the second and third metal cylindrical through - holes are both arranged in an elliptical arc shape. The second and third metal cylindrical through - holes are symmetrically loaded starting from the straight edge of the metal patch and along the elliptical arc edge. The specific numbers of the first, second, and third metal cylindrical through - holes are determined according to the electromagnetic simulation software e TM 31 、 e TM 51 and e TM 12 mode current distributions, that is, when e TM 31 、 e TM 51 mode currents are orthogonal to e TM 12 mode current, the loading stops.

2. The broadband elliptical microstrip antenna applicable to indoor communication according to claim 1, wherein: The elliptical slot is loaded at the center of the metal patch e TM 51 The zero value point of the electric field in the mode is at the electric wall, e TM 31 the peak value of the electric field in the mode is at the magnetic wall, and the minor axis of the elliptical slot coincides with the major axis of the metal patch.

3. The broadband elliptical microstrip antenna applicable to indoor communication according to claim 1, wherein: Along the ground metal plate e TM 12 At the two symmetric electric field zero points, i.e., the electric walls, of the mode, a first rectangular slot and a second rectangular slot are respectively provided, and the first rectangular slot and the second rectangular slot are parallel to e TM 31 and e TM 51 mode current distributions.

4. The broadband elliptical microstrip antenna applicable to indoor communication according to any one of claims 1-3, characterized in that: The first short - circuit wall, the second short - circuit wall, and the third short - circuit wall are used to eliminate e TM 31 and e TM 51 mode's anti - phase magnetic current elements and are used to complete e TM 31 and e TM 51 mode's current orthogonalization process with e TM 12 mode.

5. The broadband elliptical microstrip antenna applicable to indoor communication according to any one of claims 1-3, characterized in that: The stub is used to enhance the gain in the radiation passband e TM 31 mode, and the stub is disposed on e TM 31 the magnetic wall boundary of the mode.

6. The broadband elliptical microstrip antenna applicable to indoor communication according to claim 5, characterized in that: The process of determining the length of the stub is as follows: increase the length of the stub until the difference between the maximum and minimum values of the gain within the entire passband is within the set value by electromagnetic simulation software, then stop increasing and determine the length of the stub.

7. The broadband elliptical microstrip antenna applicable to indoor communication according to any one of claims 1 to 3, characterized in that: The semi-major axis length a of the metal patch is a = 0.474λ0, and the eccentricity e = 0.38; the minor axis length W1 of the elliptical groove is W1 = 0.122λ0, and the major axis length is L1: L1 = 0.395λ0; the lengths of the first rectangular narrow groove and the second rectangular narrow groove are L3 = 0.304λ0, where λ0 is the wavelength corresponding to the center frequency at which the antenna operates, the stub length L2 = 0.049λ0, the diameter of the annular capacitive groove is 0.08λ0, and the width of the annular capacitive groove is 0.12 mm. The overall antenna formed by the dielectric substrate, the ground metal plate, and the metal patch is rectangular with dimensions of 0.73λ0 × 0.949λ0 × 0.049λ0. The dielectric substrate is made of a copper-clad Teflon fiberglass board F4B with a relative dielectric constant of ε r = 3.55, and the loss tangent value is tanδ = 0.002.

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