TWI645620B - Frequency reconfigurable circularly polarized antenna - Google Patents

Abstract

The invention provides a frequency reconfigurable circularly polarized antenna, which comprises a metal resonant cavity, an antenna substrate and an antenna radiation plate. The metal resonant cavity has an opening. The antenna substrate is disposed at an opening of the metal resonant cavity. The antenna radiant panel is disposed on the antenna substrate, wherein the antenna radiant panel comprises a plurality of slotted holes and a plurality of metal strip groups, wherein each of the two adjacent slotted holes has one of a plurality of metal strip groups.

Description

 Frequency reconfigurable circularly polarized antenna  

The present invention relates to a circularly polarized antenna, and more particularly to a frequency reconfigurable circularly polarized antenna.

The Internet of Things (IoT) is an important and booming industry. Microsoft founder Bill Gates first mentioned the idea of the Internet of Things in the book "The Road to the Future" published in 1955. The lost camera can Automatically send the location to the owner. In 2005, the concept of the Internet of Things was officially proposed by the International Telecommunication Union. The Internet of Things is a vast field of application of objects. The Internet of Things can be divided into three levels: the sensing layer, the network layer and the application layer. The Radio Frequency Identification (RFID) system is an important component in the sensing layer.

The components of the RFID system include a tag and a card reader. The tag is mainly attached to an object or a cargo. The card reader reads the data in the tag on the object or the goods, converts the information into a computer or a network cloud. And combined with the database to perform management and control, such as controlling the flow of goods, goods inventory or electronic wallet deduction. Because it is a convenient and low-cost way to automate operations through RFID systems, RFID systems are widely used in areas such as warehousing and logistics that require large inventory counts.

RFID systems have applications from the 125KHz to 5.8GHz frequency bands. Low-frequency RFID usually uses coil induction. High-frequency RFID usually uses a capacitive electric field effect. An antenna is needed to radiate and capture electromagnetic energy. Regarding the design of the antenna, because the regulatory frequency bands of different countries in the world are different, the broadband antenna design of the full frequency domain is generally adopted to reduce the antenna production and inventory, but the design of the broadband antenna usually causes the antenna to be bulky and easy to receive. The noise in the required frequency band requires an additional high performance filter to filter out these noises.

Taking China National Patent Publication No. M429184 as an example, it provides a circularly polarized antenna that can effectively reduce the size of an antenna without affecting the radiation performance of the antenna. The antenna is designed with a power splitter and thus has a circular polarization axis ratio. The advantage of wide bandwidth. Although the above patent can effectively reduce the size of the antenna, the antenna is double-sided radiation. If there are many metals around the environment, the antenna performance and working ability will be changed, and even the normal operation will not work.

China National Patent Publication No. 518800 is a circularly polarized antenna with adjustable frequency, which can adjust the operating frequency by changing the slot width. However, the frequency adjustment function cannot be achieved quickly and easily, and because the accuracy of the antenna volume is quite sensitive to the placement position of the antenna, it will be a challenge in mass production.

The circularly polarized antenna of the Republic of China Patent Publication No. I518989 is a miniaturized antenna that has many metals around the environment and does not affect the antenna performance. This antenna can be adjusted simply by modifying the structural parameters to adjust the antenna characteristics. However, once the antenna is finished, the antenna operating frequency is fixed. If the antenna is to be operated at different frequencies and the design needs to be re-modified, it will be a challenge in production and inventory.

The object of the present invention is to provide a circularly polarizable antenna with recombination frequency, which utilizes a metal resonant cavity and an antenna radiation plate thereon to achieve a circularly polarized antenna, and because the periphery of the antenna radiation plate is surrounded by the metal of the metal resonant cavity, Therefore, the tolerance for the use environment is good. After the production is completed, the operating frequency of the circularly polarized antenna can be reorganized by changing the connection pattern of the plurality of metal strip groups, and the change does not affect or have little influence on the circular polarization characteristics of the antenna.

The invention provides a frequency reconfigurable circularly polarized antenna, which comprises a metal resonant cavity, an antenna substrate, an antenna radiation plate and a plurality of metal strip groups. The metal resonant cavity has an opening. The antenna substrate is disposed at an opening of the metal resonant cavity. The antenna radiant panel is disposed on the antenna substrate, wherein the antenna radiant panel comprises a plurality of slotted holes and a plurality of metal strip groups, wherein each of the two adjacent slotted holes has one of a plurality of metal strip groups.

The above described features and advantages of the invention will be apparent from the following description.

100, 200‧‧‧ Frequency reconfigurable circularly polarized antenna

110‧‧‧Metal resonator

112‧‧‧Fixed structure

114‧‧‧Signal connector

120‧‧‧Antenna substrate

130‧‧‧Antenna radiation board

130a‧‧‧ Radiation Department

130b‧‧‧Feeding Department

132‧‧‧ slotted hole

134‧‧‧Feed into the slot

136‧‧‧Fixed slots

140, 240‧‧‧Metal strips

142, 242‧‧‧ metal strips

144‧‧‧Metal connectors

244‧‧‧ coarse metal joints

246‧‧‧ fine-tuned metal connectors

150‧‧‧ Signal Feeding Components

152‧‧‧Signal Department

154‧‧‧ Grounding Department

A-A’, B-B’‧‧‧ tangent

C1, C2, C3, C4, C5, C6, C7, C8‧‧‧ curves

SC‧‧‧Fixed parts

The aspects of the present disclosure can be better understood from the following detailed description when read in conjunction with the drawings. It should be emphasized that various features are not drawn to scale in accordance with standard practice in the industry. In fact, various features may be arbitrarily increased or decreased for clarity of discussion.

1 is a top view of a frequency reconfigurable circularly polarized antenna in accordance with a first embodiment of the present invention.

Fig. 2 is a cross-sectional view showing a frequency reconfigurable circularly polarized antenna taken along a line A-A' of Fig. 1 in accordance with a first embodiment of the present invention.

3A] [FIG. 3D] are top views of a frequency reconfigurable circularly polarized antenna having different metal strip connection patterns in accordance with a first embodiment of the present invention.

Fig. 4 is a graph showing the reflection coefficient vs. frequency response of the frequency reconfigurable circularly polarized antenna according to the first embodiment of the present invention, in the connection pattern of the different metal strips of Figs. 3A to 3D.

FIG. 5 is an axial ratio diagram of a frequency reconfigurable circularly polarized antenna according to a first embodiment of the present invention, in a connection pattern of different metal strips of FIGS. 3A to 3D.

Fig. 6 is a cross-sectional view showing a frequency reconfigurable circularly polarized antenna taken along a line C-B' of Fig. 1 in accordance with a first embodiment of the present invention.

Fig. 7 is a top view showing a frequency reconfigurable circularly polarized antenna in accordance with a second embodiment of the present invention.

8A] [Fig. 8C] are top views of a frequency reconfigurable circularly polarized antenna having different metal strip connection patterns in accordance with a second embodiment of the present invention.

Please refer to FIG. 1. FIG. 1 is a top view of a frequency reconfigurable circularly polarized antenna 100 in accordance with a first embodiment of the present invention. The frequency reconfigurable circularly polarized antenna 100 includes a metal resonant cavity 110, an antenna substrate 120, and an antenna radiating plate 130. The metal resonant cavity 110 has an opening, and the antenna substrate 120 is disposed at this opening. The antenna radiating plate 130 is disposed on the antenna substrate 120 and includes a plurality of notches 132 and a plurality of metal strip groups 140. There is one of a plurality of metal strip sets 140 between each two adjacent slotted holes 132. In the present embodiment, the antenna substrate 120 is an FR4 substrate, and the antenna radiation plate 130 is a metal plate, but the embodiment of the present invention is not limited thereto.

In the present embodiment, the slotted holes 132 are respectively located at four sides of the antenna radiation plate 130 and are symmetrically arranged with each other. However, embodiments of the invention are not limited thereto. In other embodiments of the invention, the slotted apertures 132 are only arranged around the center of the antenna radiant panel 130 and may achieve the desired antenna characteristics.

Referring to Figure 2, there is shown a cross-sectional view of a reconfigurable circularly polarized antenna 100 along the line A-A' of Figure 1 in accordance with a first embodiment of the present invention. The frequency reconfigurable circularly polarized antenna 100 further includes a signal feeding component 150. The signal feeding component 150 includes a signal portion 152 and a ground portion 154. The signal portion 152 is electrically connected to the antenna radiating plate 130, and the ground portion 154 is electrically connected to the metal resonant cavity 110.

Referring to FIG. 2 again, the outer surface of the metal resonant cavity 110 may be provided with a signal connector 114. The signal terminal of the signal connector 114 is electrically connected to the signal portion 152 of the signal feeding component 150. The ground terminal of the signal connector 114 is electrically connected to the metal resonant cavity 110.

Referring again to FIGS. 1 and 2, the antenna radiant panel 130 further has a feed slot 134 that is located on the diagonal of the antenna radiant panel 130. The feed slot 134 separates the antenna radiating plate 130 into a radiating portion 130a and a feeding portion 130b that are electrically isolated from each other. The signal feeding portion 130b is electrically connected to the signal end of the signal connector 114 via the signal portion 152 of the signal feeding component 150. The signal connector 114 receives the feeding signal to the feeding portion 130b, and then couples the feeding signal to the radiation by capacitive coupling. The portion 130a is thereby used to excite the circularly polarized antenna 100 whose frequency can be recombined. In the present embodiment, the signal connector 114 is an SMA connector that is connected to a coaxial cable to receive the feed signal, but the embodiment of the present invention is not limited thereto.

Returning to FIG. 1, in the present embodiment, each metal strip group 140 includes a plurality of metal strips 142 and a plurality of metal connectors 144. The metal connectors 144 are located between the metal strips 142 to electrically connect the metal strips 142. In other embodiments of the invention, each metal strip group includes a plurality of metal strips and a plurality of switches. The switch is located between the metal strips to electrically connect or electrically isolate the metal strip according to a control signal provided externally. In other embodiments of the invention, the switch can be a diode switch, although embodiments of the invention are not limited thereto.

Since the metal strip group 140 of the embodiment has the metal connecting body 144, the user can electrically isolate the metal strip 142 in the metal strip group 140 by removing the metal connecting body 144, thereby adjusting the frequency reconfigurable circularly polarized antenna 100. Operating frequency range. Several types of connecting metal strip connections will be listed below to illustrate changes in the operating frequency range.

Referring to Figures 3A-3D, there are shown top views of a frequency reconfigurable circularly polarized antenna 100 having different metal strip 142 connections in accordance with a first embodiment of the present invention. As shown in FIG. 3A, in the illustration of FIG. 3A, the metal connectors 144 of each of the metal strip groups 140 are removed, and the metal strips 142 are not connected to each other. As shown in FIG. 3B, in the illustration of FIG. 3B, the first metal strips 142 of each of the metal strip groups 140 are interconnected by a metal connecting body 144. As shown in FIG. 3C, in the illustration of FIG. 3C, the first two metal strips 142 of each of the metal strip groups 140 are interconnected by a metal connecting body 144. As shown in FIG. 3D, in the illustration of FIG. 3D, the metal strips 142 in each of the metal strip sets 140 are all connected by a metal connecting body 144.

Referring to FIG. 4, there is shown a reflection coefficient vs. frequency response diagram of the frequency reconfigurable circularly polarized antenna 100 according to the first embodiment of the present invention, in the connection pattern of the different metal strips 142 of FIGS. 3A-3D. The curve C1 in FIG. 4 shows the reflection coefficient versus frequency response of the frequency reconfigurable circularly polarized antenna 100 according to the connection pattern of the metal strip 142 of FIG. 3A; the curve C2 in FIG. 4 represents the frequency reconfigurable circularly polarized antenna. The reflection coefficient vs. frequency response diagram of the connection pattern of the metal strip 142 of FIG. 3B; the curve C3 of FIG. 4 represents the reflection coefficient of the frequency reconfigurable circularly polarized antenna 100 according to the connection pattern of the metal strip 142 of FIG. 3C. The frequency response map; the curve C4 in FIG. 4 shows the reflection coefficient versus frequency response of the frequency reconfigurable circularly polarized antenna 100 according to the connection pattern of the metal strip 142 of FIG. 3D. As can be seen from FIG. 4, when the metal strips 142 of the metal strip group 140 are connected to each other, since the current path becomes long, the operating frequency band of the frequency reconfigurable circularly polarized antenna drifts to the low frequency and is in the respective work. The return loss in the frequency band is less than 10dB, which has good antenna radiation efficiency.

Referring to FIG. 5, an axial ratio diagram of the frequency reconfigurable circularly polarized antenna 100 according to the first embodiment of the present invention, in the connection pattern of the different metal strips 142 of FIGS. 3A-3D, is shown. The curve C5 in FIG. 5 represents an axial ratio diagram of the frequency reconfigurable circularly polarized antenna 100 according to the connection pattern of the metal strip 142 of FIG. 3A; the curve C6 in FIG. 5 represents the frequency reconfigurable circularly polarized antenna 100 according to the diagram. The axial ratio diagram of the connection pattern of the metal strip 142 of 3B; the curve C7 in FIG. 5 shows the axial ratio diagram of the circularly polarizable antenna 100 of the recombination frequency according to the connection pattern of the metal strip 142 of FIG. 3C; Curve C8 represents an axial ratio of the frequency reconfigurable circularly polarized antenna 100 in accordance with the connection pattern of the metal strip 142 of FIG. 3D. As can be seen from FIG. 5, when the metal strips 142 of the metal strip group 140 are connected to each other, since the current path becomes long, the axis of the frequency reconfigurable circularly polarized antenna drifts toward the low frequency band and is in the respective work. The axial ratio is less than 3dB in the frequency band, and has good circular polarization radiation performance of the antenna.

It can be seen from the above description that the frequency reconfigurable circularly polarized antenna 100 of the first embodiment of the present invention can change the operating frequency range by removing the metal connecting body 144 in the metal strip group 140, so that the user can appropriately The metal connector 144 is removed to adjust the operating frequency range of the frequency reconfigurable circularly polarized antenna 100 to a desired target frequency range. How to adjust the operating frequency range of the frequency reconfigurable circularly polarized antenna 100 to a desired target frequency range will be described below.

Returning to Figures 3A-3D, in a first embodiment, the removal of the metal connector 144 can be used to adjust the frequency of the frequency reconfigurable circularly polarized antenna 100. As shown in FIG. 3D, when the user performs frequency adjustment, the four outermost metal connectors 144 may be removed first, so that the operating frequency range of the frequency reconfigurable circularly polarized antenna 100 approaches the target frequency range. As shown in Figure 3C. Then, if the operating frequency range of the frequency reconfigurable circularly polarized antenna 100 still has a large gap with the target frequency range, the four internal metal connectors 144 are further removed to adjust the frequency reconfigurable circular pole. The operating frequency range of the antenna 100 is as shown in FIG. 3B. Similarly, if the operating frequency range of the frequency reconfigurable circularly polarized antenna 100 still has a large difference from the target frequency range, then the four innermost metal connectors 144 are continuously removed to adjust the frequency recombinable circle. The operating frequency range of the polarized antenna 100 is as shown in FIG. 3A. In this way, the operating frequency range of the frequency reconfigurable circularly polarized antenna 100 is close to the target frequency range.

It is worth mentioning that in order to maintain the circularly polarized radiation effect of the circularly polarizable antenna 100 whose frequency can be recombined, the adjustment of the metal strip group 140 must be symmetrical. For example, when the user wants to make a working band adjustment, the metal connectors 144 in the strip set 140 must be removed symmetrically.

In addition, the number of the slotted holes 132, the metal strip group 140, the metal strips 142, and the metal connecting body 144 of the embodiment of the present invention is not limited to the first embodiment described above. In other embodiments of the present invention, the number of slotted holes 132, metal strip sets 140, metal strips 142, and metal connectors 144 may be varied according to actual needs of the user.

Referring to Figures 1 and 6, Figure 6 is a cross-sectional view of a frequency reconfigurable circularly polarized antenna taken along line C-B' of Figure 1 in accordance with a first embodiment of the present invention. In this embodiment, the antenna substrate 120 and the antenna radiating plate 130 further have fixing slots 136 for the fixing member SC to fix the antenna substrate 120 to the metal resonant cavity 110. In the embodiment, the fixing member SC is a screw that penetrates the fixing hole 136 of the antenna radiant panel 130 and the antenna substrate 120, and is locked in the fixing structure 112 of the metal resonant cavity 110. Since the fixing slot 136 is a tapered slot, when the fixing member SC is locked to the fixing structure 112, the fixing member SC does not contact the antenna radiating plate 130 to avoid affecting the antenna radiating plate 130.

By locking the antenna substrate 120 to the metal resonant cavity 110, displacement of the antenna radiation plate 130 over time can be avoided, resulting in changes in antenna characteristics.

The shape of the antenna radiating plate 130, the slotted hole 132, the feeding slot 134 and the fixing slot 136 is also not limited to the first embodiment described above, and in other embodiments of the present invention, it may be a regular geometry. . For example, the antenna radiant panel 130 may be square, circular, elliptical, triangular or polygonal. The slot 132, the feed slot 134 and the fixed slot 136 may each be square, circular, elliptical, triangular, semi-circular. Or a polygon. In the first embodiment of FIG. 1, the antenna radiant panel 130 has a regular geometry, and the slot 132, the feed slot 134, and the slot 136 are all circular.

Please refer to FIG. 7. FIG. 7 is a top view of a frequency reconfigurable circularly polarized antenna 200 in accordance with a second embodiment of the present invention. The frequency reconfigurable circularly polarized antenna 200 is similar to the frequency reconfigurable circularly polarized antenna 100, but differs in that the frequency reconfigurable circularly polarized antenna 200 has a plurality of metal strip sets 240, each metal strip set 240 A plurality of metal strips 242, a plurality of coarse metal joints 244, and a plurality of fine metal joints 246 are included. The coarse metal connection 244 is located between the metal strips 242, and the fine metal connection 246 is located in the metal strip 242 for electrically connecting the metal strips 242. In other embodiments of the invention, each metal strip group includes a plurality of metal strips and a plurality of switches. The switch is located between the metal strips and the metal strip to electrically connect or electrically isolate the metal strip according to a control signal provided externally. In other embodiments of the invention, the switch can be a diode switch, although embodiments of the invention are not limited thereto.

In addition, the number of the metal strip group 240, the metal strip 242, the coarse metal connecting body 244, and the fine metal connecting body 246 of the embodiment of the present invention is not limited to the second embodiment described above. In other embodiments of the present invention, the number of metal strip sets 240, metal strips 242, coarse metal joints 244, and fine metal joints 246 can be varied according to the actual needs of the user.

In the second embodiment of the present invention, the user can electrically isolate the metal strips 242 in the metal strip group 240 by removing the coarse metal connecting body 244 or the fine metal connecting body 246, thereby finely adjusting the frequency to be reconfigurable. The operating frequency range of the circularly polarized antenna 200. How to finely adjust the operating frequency range of the frequency reconfigurable circularly polarized antenna 200 to a desired target frequency range will be described below.

Referring to Figures 8A-8C, there are shown top views of a frequency reconfigurable circularly polarized antenna 200 having different metal strip 242 connections in accordance with a second embodiment of the present invention. In this embodiment, the removal of the coarse adjustment metal connector 244 can be used to substantially adjust the frequency reconfigurable circularly polarized antenna 200. The removal of the fine adjustment metal connector 246 can be used to adjust the frequency slightly. The frequency of the recombined circularly polarized antenna 200. As shown in FIG. 8A, when the user performs frequency adjustment, the four outermost four coarse metal connecting bodies 244 may be removed first, so that the operating frequency range of the frequency reconfigurable circularly polarized antenna 200 is substantially toward the target. The frequency range is close, as shown in Figure 8B. Then, if the operating frequency range of the frequency reconfigurable circularly polarized antenna 200 still has a large gap with the target frequency range, the internal coarse adjustment metal connector 244 is continuously removed to greatly adjust the frequency to be recombined. The operating frequency range of the circularly polarized antenna 200. On the other hand, if the operating frequency range of the frequency reconfigurable circularly polarized antenna 200 is not much different from the target frequency range, the user can then remove the fine adjustment metal connector 246 to make the frequency reconfigurable circularly polarized antenna 200 The operating frequency range is slightly close to the target frequency range, as shown in Figure 8C. In this way, the operating frequency range of the frequency reconfigurable circularly polarized antenna 200 is close to the target frequency range.

It is worth mentioning that in order to maintain the circularly polarized radiation effect of the circularly polarizable antenna 100 whose frequency can be recombined, the adjustment of the metal strip group 240 must be symmetrical. For example, when the user wants to make a large frequency adjustment, the coarse adjustment metal connector 244 must be removed symmetrically. As another example, when the user desires to make a small frequency adjustment, the fine adjustment metal connector 246 must be removed symmetrically. Based on the above description, the frequency reconfigurable circularly polarized antenna of the embodiment of the present invention adopts a patch antenna as a structure, and has a plurality of metal strip groups, and the current path is changed by changing the connection pattern of the metal strip group, and can be adjusted. The working frequency band of the circularly polarized antenna whose frequency can be recombined to reach the preset target frequency band. Secondly, the frequency reconfigurable circularly polarized antenna of the embodiment of the present invention may include a fixing member for fixing the antenna substrate to the metal resonant cavity, thereby avoiding the characteristic change of the frequency reconfigurable circularly polarized antenna. Furthermore, the frequency reconfigurable circularly polarized antenna of the embodiment of the present invention can adopt a single feed mode, and the feed signal is fed by the feed portion on the diagonal of the antenna radiant panel, and then capacitively coupled to the antenna radiant panel. The radiation part reaches the two vertical modes required for the recombination of the circularly polarized antenna, so that the frequency reconfigurable circularly polarized antenna has good tolerance to the use environment and allows the user to adjust the frequency by himself. The working frequency band of the reorganized circularly polarized antenna meets various antenna requirements.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and retouched without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

Claims (10)

A frequency reconfigurable circularly polarized antenna comprising: a metal resonant cavity having an opening; an antenna substrate disposed in the opening of the metal resonant cavity; and an antenna radiating plate disposed on the antenna substrate, wherein The antenna radiant panel includes a plurality of slotted holes and a plurality of metal strip groups, wherein each of the two adjacent slotted holes has one of the metal strip groups, wherein the slotted holes are opposite to the metal The plurality of sides of the resonant cavity are symmetrically disposed, wherein the plurality of metal strips are symmetrically disposed with respect to a plurality of angles of the metal resonant cavity, wherein the frequency is reconfigurable by changing a connection pattern of each of the metal strip groups An operating frequency of a circularly polarized antenna. The frequency reconfigurable circularly polarized antenna according to claim 1, further comprising a signal feeding component, wherein the two contacts of the signal feeding component are electrically connected to the antenna radiant panel and the metal resonance Cavity. The frequency reconfigurable circularly polarized antenna according to claim 2, further comprising a feeding slot, wherein the feeding slot and the signal feeding component are used to excite the frequency by capacitive coupling Reconfigurable circularly polarized antenna. The frequency reconfigurable circularly polarized antenna according to claim 1, wherein each of the metal strip groups comprises a plurality of metal strips And a plurality of metal connectors, the metal connectors are located between the metal strips to electrically connect the metal strips. The frequency reconfigurable circularly polarized antenna according to claim 1, wherein each of the metal strip groups includes a plurality of metal strips and a plurality of switches, the switches being located between the metal strips, according to A control signal electrically connects at least one of the metal strips. The frequency reconfigurable circularly polarized antenna according to claim 5, wherein the switches are diode switches. The frequency reconfigurable circularly polarized antenna according to claim 1, further comprising a fixing member, wherein the fixing member penetrates the antenna radiation plate and the antenna substrate to fix the antenna substrate to the metal resonant cavity on. The frequency-reconfigurable circularly polarized antenna according to claim 1, wherein the antenna substrate is made of a dielectric material. The frequency reconfigurable circularly polarized antenna according to claim 1, wherein the antenna radiant panel is a metal plate. The frequency reconfigurable circularly polarized antenna according to claim 3, wherein the antenna radiant panel, the slotted holes, and the feed The slotted holes are of a regular geometry.