A single-plane electric small magnetic dipole microstrip antenna

Abstract

This invention discloses a single-planar electrically small magnetic dipole microstrip antenna, comprising a dielectric substrate and an antenna radiating element attached to the upper surface of the dielectric substrate. The antenna radiating element includes a rectangular open loop and a parallel transmission line. The parallel transmission line is placed at the opening of the rectangular open loop to excite the dipole. The opening of the rectangular open loop is located at the top of the loop, and the bottom edge of the loop is not directly connected to its left and right sides, but rather coupled together, with both ends of the bottom edge of the loop bent upwards at 90° to couple to the left and right sides of the loop, respectively. This invention achieves miniaturization of the magnetic dipole antenna while maintaining a single-planar structure, allowing it to be integrated into implantable wireless mobile medical devices for stable wireless communication.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, and specifically relates to a single-plane electrically small magnetic dipole microstrip antenna. Background Technology

[0002] With the rapid development of modern communication technology, mobile healthcare, which provides medical services to patients through implantable wireless communication devices, has received increasing attention. In wireless mobile medical devices, the antenna is a key component for wireless communication. Theoretical analysis has revealed that, when surrounded by a lossy medium, magnetic antennas exhibit lower losses and better radiation performance compared to electric antennas. Furthermore, magnetic antennas have less impact on the human body, and their radiation characteristics remain relatively stable regardless of the conductivity of different media. Therefore, magnetic dipole antennas, as magnetic antennas, are widely used in implantable wireless mobile medical devices. With the trend towards device miniaturization, miniaturized, low-profile magnetic dipole antennas will have broad application prospects.

[0003] Generally speaking, there are two ways to implement magnetic dipole antennas: current loop antennas and slot antennas. Slot antennas typically require two layers of metal structure, making the overall structure relatively complex. Current loop antennas usually have low radiation impedance, and to achieve good impedance matching, lumped elements or grounding holes are usually required, which are inconvenient for fabrication and assembly. Therefore, designing a single-plane, low-cost, and easily fabricated microstrip antenna is of significant research value. Summary of the Invention

[0004] To address the problems of the prior art, this invention proposes a single-planar electrically small magnetic dipole microstrip antenna. This invention achieves miniaturization of the magnetic dipole antenna while retaining the characteristics of a single-planar structure. Therefore, the antenna is simple in structure, easy to manufacture, and readily integrated into implantable wireless mobile medical devices for stable wireless communication, thus solving the problems existing in the prior art.

[0005] The technical solution of the present invention is implemented as follows: a single-plane electric small magnetic dipole microstrip antenna includes a dielectric substrate and an antenna radiating element attached to the upper surface of the dielectric substrate; the antenna radiating element includes a rectangular open loop and a parallel transmission line; the parallel transmission line is placed at the opening of the rectangular open loop and is used to excite the dipole to work.

[0006] The opening of the rectangular open loop is located at the top of the loop. To adjust the current magnitude on each side of the rectangular open loop and achieve a good current loop antenna, the bottom edge of the loop is not directly connected to its left and right sides, but rather connected via coupling. Specifically, both ends of the bottom edge of the loop are bent upwards at 90° and coupled to the left and right sides of the loop, respectively. It should be noted that the current loop antenna can be equivalently represented as a magnetic dipole antenna perpendicular to the current loop.

[0007] Preferably, the circumference of the rectangular open ring is approximately one wavelength.

[0008] Preferably, the total length of the rectangular open ring is at least two-fifths of the working wavelength; wherein, the length of the upper and lower sides is at least one-eighth of the working wavelength, the width of the upper side is at least one-three-hundredth of the working wavelength, and the width of the lower side is at least one-two-hundredth of the working wavelength; the length of the left and right sides is at least one-tenth of the working wavelength, and the width of the left and right sides is at least one-three-hundredth of the working wavelength; the length of the lower coupling branch is at least one-thirtieth of the working wavelength, the width is at least one-two-hundredth of the working wavelength, and the distance between the coupling branch and the left and right sides is at least one-three-thousandth of the working wavelength.

[0009] Preferably, the parallel transmission line consists of two parallel microstrip lines. To achieve a compact structure, the parallel transmission line feeding the rectangular open loop extends into the rectangular open loop.

[0010] Preferably, a comb structure, i.e. a capacitor structure, is introduced into the parallel transmission line to adjust the impedance of the single-plane electric small magnetic dipole microstrip antenna and achieve impedance matching.

[0011] Preferably, the total length of the parallel transmission lines is at least one-fourteenth of the operating wavelength, wherein the length of the comb structure is at least one-thirtieth of the operating wavelength, the width of each of the two microstrip lines is at least one-three-hundredth of the operating wavelength, the spacing is at least one-seven-hundredth of the operating wavelength, and the starting point of the comb branch is at least one-two-hundredth of the operating wavelength from the feed point.

[0012] Due to the adoption of the above technical solutions, the present invention has the following beneficial technical effects:

[0013] 1) The overall dimensions of this single-planar electrically small magnetic dipole microstrip antenna are 0.19λ0×0.16λ0×0.003λ0 (ka=0.77<1, which meets the requirements for electrically small size), where λ0 is the wavelength corresponding to the operating frequency of 915MHz; the antenna has good impedance matching characteristics and a gain of 2.24dBi at the operating frequency (0.915GHz);

[0014] 2) This single-plane electric small magnetic dipole microstrip antenna has advantages such as miniaturization, single-plane structure, low cost and ease of manufacturing. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some examples of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the single-plane electrically small magnetic dipole microstrip antenna described in this invention;

[0017] Figure 2 This is a planar structural diagram of the single-plane electrically small magnetic dipole microstrip antenna patch described in this invention;

[0018] Figure 3 The reflection coefficient of the single-plane electric small magnetic dipole microstrip antenna described in this invention;

[0019] Figure 4 This is a schematic diagram of the current distribution on the surface of the single-plane electric small magnetic dipole microstrip antenna described in this invention;

[0020] Figure 5 This is the three-dimensional radiation pattern of the single-plane electric small magnetic dipole microstrip antenna described in this invention at the operating frequency (915MHz);

[0021] Figure 6 The main polarization (E) of the single-plane electrically small magnetic dipole microstrip antenna described in this invention in the E-plane (i.e., the xoy plane) θ and cross-polarization picture;

[0022] Figure 7 The main polarization (E) of the single-plane electrically small magnetic dipole microstrip antenna described in this invention in the H-plane (i.e., the yoz plane) is... θ and cross-polarization picture.

[0023] In the figure: 1-Dielectric substrate; 2-Rectangular aperture ring; 21-Upper edge of rectangular aperture ring; 22-Left edge of rectangular aperture ring; 23-Lower edge of rectangular aperture ring; 231-Lower microstrip line; 232-Lower coupling stub; 24-Right edge of rectangular aperture ring; 3-Parallel transmission line; 31-Front-end parallel microstrip line; 32-Dressing structure; 33-Rear-end parallel microstrip line; 4-Aperture; 5-Excitation port. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention discloses a single-plane electrically small magnetic dipole microstrip antenna. Figure 1 and Figure 2 This is a schematic diagram of a single-plane electric small magnetic dipole microstrip antenna operating at 915MHz, according to an embodiment. It includes a dielectric substrate 1 and an antenna radiating element attached to the upper surface of the dielectric substrate 1. The antenna has the characteristic of being single-plane.

[0026] The dielectric substrate 1 is made of polytetrafluoroethylene (PTFE), with a relative permittivity of 2.2, a relative permeability of 1.0, a loss tangent of 0.0009, and a thickness of 1 mm.

[0027] like Figure 1 and Figure 2 As shown, the antenna radiating element includes a rectangular open loop 2 and a parallel transmission line 3; the opening 4 of the rectangular open loop is located on the upper edge 21 of the rectangular open loop 2. The two ends of the lower edge 23 of the rectangular open loop are bent upwards at 90°, forming a lower microstrip line 231 and a lower coupling stub 232. The lower edge 23 of the rectangular open loop is connected to the left side 22 and the right side 24 of the rectangular open loop via coupling. The parallel transmission line 3 is connected to the excitation port 5.

[0028] The length of the lower microstrip line 231 of the rectangular open-loop is at least one-eighth of the operating wavelength; the width of the upper edge 21 of the rectangular open-loop is at least one-three-hundredth of the operating wavelength; the width of the lower edge 23 of the rectangular open-loop is at least one-two-hundredth of the operating wavelength; the length of the left edge 22 and the right edge 24 of the rectangular open-loop is at least one-tenth of the operating wavelength, and the width is at least one-three-hundredth of the operating wavelength; the length of the lower coupling stub 232 of the rectangular open-loop is at least one-thirtieth of the operating wavelength, and the width is at least one-two-hundredth of the operating wavelength; the distance between the lower coupling stub 232 and the corresponding left or right edge is at least one-three-thousandth of the operating wavelength.

[0029] The parallel transmission line 3 consists of two parallel microstrip lines with a comb structure, namely, a front parallel microstrip line 31, a comb structure 32, and a rear parallel microstrip line 33. The parallel transmission line 3 extends from the opening of a rectangular open ring into the rectangular open ring. Preferably, the length of the parallel transmission line 3 is at least one-fourteenth of the operating wavelength, wherein the length of the comb structure 32 is at least one-thirtieth of the operating wavelength, the width of each of the two microstrip lines is at least one-three-hundredth of the operating wavelength, the spacing is at least one-seven-hundredth of the operating wavelength, and the starting point of the comb branch is at least one-two-hundredth of the operating wavelength from the feed point.

[0030] After the initial design, high-frequency electromagnetic simulation software was used for simulation. The optimized parameters and dimensions are shown in the table below:

[0031] Table 1 Optimal Dimensions for Each Parameter of the Invention

[0032]

[0033]

[0034] Where L is the overall length of the antenna, l1 is the length of the upper side 21 of the rectangular opening ring, l2 is the length of the left side 22 and the right side 24 of the rectangular opening ring, l3 is the length of the microstrip line 231 in the lower side 23 of the rectangular opening ring, l4 is the length of the coupling stub 232 formed by the upward 90° bend in the lower side 23 of the rectangular opening ring, l5 is the length of the parallel transmission line 3, l6 is the length of the front section of the parallel microstrip line 31 in the parallel transmission line, l7 is the length of the comb structure 32 in the parallel transmission line, l8 is the length of the rear section of the parallel microstrip line 33 in the parallel transmission line, and W is the overall length of the antenna. The widths are as follows: w1 is the width of the upper edge 21 of the rectangular open ring; w2 is the width of the left edge 22 and the right edge 24 of the rectangular open ring; w3 is the width of the microstrip line 231 and the coupling stub 232 in the lower edge 23 of the rectangular open ring; w4 is the width of the coupling gap between the coupling stub 232 formed by bending upwards at 90° in the lower edge 23 of the rectangular open ring and the left edge 22 or the right edge 24 of the rectangular open ring; w5 is the width of the front section of the parallel microstrip line 31 in the parallel transmission line; w6 is the width of the gap in the comb structure 32 in the parallel transmission line; and w7 is the spacing between the parallel transmission lines.

[0035] Based on the above parameters, the reflection coefficient |S| of the designed single-plane electrically small magnetic dipole microstrip antenna is... 11 Simulation analysis was performed on the current distribution and radiation pattern, and the results are as follows:

[0036] Figure 3 This is a graph showing the reflection coefficient of the single-planar electrically small magnetic dipole microstrip antenna in this invention as a function of frequency. From... Figure 3As can be seen from the simulation (actual measurement), the resonant frequency of the single-plane electric small magnetic dipole microstrip antenna is 915MHz (900MHz), and the corresponding reflection coefficient is -23.8dB (-30dB). The single-plane electric small magnetic dipole microstrip antenna has good impedance matching characteristics.

[0037] Figure 4 This is a current distribution diagram of a single-plane electrically small magnetic dipole microstrip antenna at the resonant frequency of 915MHz. Figure 4 In this diagram, Jsurf represents the surface current density, measured in A / m. On the rectangular open loop, the currents on the top and bottom sides are approximately equal in magnitude and opposite in direction. The currents on the left and right sides are equal in magnitude and opposite in direction. The current on the bottom coupling stub is in the same direction as the current on the coupling side. In general, the currents on all four sides of the rectangular open loop are roughly equal in magnitude, and the currents form a loop in a counter-clockwise direction, thus constituting a current loop antenna. This can be equivalent to a magnetic dipole antenna perpendicular to the loop.

[0038] from Figure 4 As can be further seen, the current amplitude on parallel transmission line 3 is also very large, but the currents on parallel transmission line 3 are opposite in direction and the spacing is very small, so the radiation cancels each other out. Therefore, its existence has almost no effect on the radiation pattern of the current loop antenna.

[0039] Figure 5 The three-dimensional radiation pattern of the electrically small magnetic dipole microstrip antenna at the resonant frequency of 915 MHz is shown. Its maximum radiation direction is located in the plane corresponding to theta = 90° (xoy plane), and the gain is 2.24 dBi. The radiation pattern is very close to that of an ideal magnetic dipole antenna.

[0040] Figure 6 The dominant polarization (E) of the electrically small magnetic dipole microstrip antenna of this invention at the resonant frequency of 915MHz in the E-plane (xoy plane) θ and cross-polarization Figure. Solid line E θ The θ component of the electric field, i.e., the radiation pattern of the principal polarization, is represented by the dashed line. Representing electric field The component is the radiation pattern of the cross-polarization. It can be seen that the principal polarization of the E-plane is a circle with a non-circularity of only 0.66 dB.

[0041] Figure 7 The dominant polarization (E) of the electrically small magnetic dipole microstrip antenna of this invention at the resonant frequency of 915MHz is the main polarization (E) of the H-plane (yoz plane). θ and cross-polarization Figure. Solid line E θ This represents the radiation pattern of the principal polarization, indicated by the dashed line. This represents the radiation pattern of cross-polarization. It can be seen that the principal polarization of the H-plane is an inverted figure-eight shape.

[0042] In summary, this invention presents a single-planar electrically small magnetic dipole microstrip antenna based on a rectangular open-loop design. The rectangular open-loop is fed using a parallel transmission line with a comb structure, achieving impedance matching. By adjusting the current magnitude on each side of the rectangular open-loop through a coupling structure, it exhibits the characteristics of a quasi-uniform current loop, thus effectively functioning as a magnetic dipole antenna. Ultimately, the designed antenna possesses advantages such as simple structure, small size, low manufacturing cost, and excellent performance, making it highly promising for a wide range of applications.

[0043] Of course, those skilled in the art should be able to make various corresponding changes and modifications based on the present invention without departing from its spirit and essence, but all such changes and modifications should fall within the protection scope of the appended claims.

Claims

1. A single-planar electrically small magnetic dipole microstrip antenna, comprising a dielectric substrate and an antenna radiating element attached to the upper surface of the dielectric substrate; characterized in that, The antenna radiating element includes a rectangular open loop and a parallel transmission line; the parallel transmission line is placed at the opening of the rectangular open loop and is used to excite the dipole to work. The opening of the rectangular open ring is located at the top of the rectangular open ring. The bottom of the rectangular open ring is not directly connected to its left and right sides, but is connected by coupling. The two ends of the bottom of the rectangular open ring are bent upward at 90° and coupled to the left and right sides of the rectangular open ring respectively.

2. The single-plane electrically small magnetic dipole microstrip antenna according to claim 1, characterized in that, The circumference of the rectangular open ring is one wavelength.

3. The single-planar electrically small magnetic dipole microstrip antenna according to claim 1, characterized in that, The total length of the rectangular open ring is at least two-fifths of the working wavelength; wherein, the length of the top and bottom sides is at least one-eighth of the working wavelength, the width of the top side is at least one-three-hundredth of the working wavelength, and the width of the bottom side is at least one-two-hundredth of the working wavelength; the length of the left and right sides is at least one-tenth of the working wavelength, and the width of the left and right sides is at least one-three-hundredth of the working wavelength; the length of the lower coupling branch is at least one-thirtieth of the working wavelength, the width is at least one-two-hundredth of the working wavelength, and the distance between the coupling branch and the left and right sides is at least one-three-thousandth of the working wavelength.

4. The single-plane electrically small magnetic dipole microstrip antenna according to claim 1, characterized in that, The parallel transmission line consists of two parallel microstrip lines that extend into the rectangular open ring to feed the rectangular open ring.

5. The single-planar electrically small magnetic dipole microstrip antenna according to claim 1, characterized in that, A comb structure is introduced into the parallel transmission line.

6. The single-planar electrically small magnetic dipole microstrip antenna according to claim 5, characterized in that, The total length of the parallel transmission lines is at least one-fourteenth of the operating wavelength, the width of each of the two microstrip lines is at least one-three-hundredth of the operating wavelength, and the spacing between them is at least one-seven-hundredth of the operating wavelength.

7. The single-planar electrically small magnetic dipole microstrip antenna according to claim 5, characterized in that, The length of the comb structure is at least one-thirtieth of the working wavelength, and the starting point of the comb branch is at least one two-hundredth of the working wavelength from the feed point.

8. The single-plane electrically small magnetic dipole microstrip antenna according to claim 5, characterized in that, The antenna has an overall length of 62.6 mm and an overall width of 51.22 mm. The length of the top edge of the rectangular opening loop is 51.66 mm, the lengths of the left and right edges of the rectangular opening loop are 37 mm, the length of the microstrip line in the lower edge of the rectangular opening loop is 46.85 mm, the length of the coupling stub formed by the upward 90° bend in the lower edge of the rectangular opening loop is 16.58 mm, the length of the parallel transmission line is 27.7 mm, the length of the front section of the parallel transmission line microstrip line is 8.33 mm, the length of the comb structure in the parallel transmission line is 16.37 mm, and the length of the rear section of the parallel transmission line is... The length of the parallel microstrip line is 3 mm. The width of the upper edge of the rectangular open ring is 2.13 mm. The width of the left and right edges of the rectangular open ring is 2.13 mm. The width of the microstrip line and coupling stub at the bottom edge of the rectangular open ring is 2.6 mm. The width of the coupling gap between the coupling stub formed by the upward 90° bend at the bottom edge of the rectangular open ring and the left or right edge of the rectangular open ring is 0.27 mm. The width of the parallel microstrip line at the front of the parallel transmission line is 2 mm. The width of the gap in the comb structure of the parallel transmission line is 0.4 mm. The spacing between the parallel transmission lines is 2 mm.

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