TWI896408B - Circularly polarized antenna and communication system - Google Patents

Abstract

A circularly polarized antenna includes an antenna unit and a feeding unit, and the antenna unit and the feeding unit are stacked up and down; the antenna unit includes a first antenna subunit arranged on a top layer of the first substrate, a parasitic element arranged in a middle layer of the first substrate, and a second antenna subunit arranged on a bottom layer of the first substrate; the feeding unit includes a coupling slot group, arranged on a top layer of the second substrate; a matching microstrip line group, arranged on a middle layer of the second substrate; a feeding line group, arranged on a bottom layer of the second substrate; a branch line coupler, arranged on a bottom layer of the second substrate, wherein the matching microstrip line group is electrically connected between the feeding line group and the branch line coupler through a hole group. The present disclosure further provides a communication system.

Description

Circularly polarized antenna and communication system

The present invention relates to the field of antenna technology, and more particularly to a circularly polarized antenna and a communication system.

In recent years, phased array antenna technology has shifted from military applications to civilian applications, such as low-orbit satellite communications systems and radar systems. Consequently, traditional phased array antenna technology has evolved from planar T/R modules to highly integrated vertically integrated T/R modules, facilitating the reduction of electronic device size and weight. Therefore, designing the structure and impedance matching between the integrated tile-type unit antenna and the T/R module will be a key development focus. Antenna polarization has also shifted from linear to circular polarization. This is primarily due to the advantages of circularly polarized antennas, which do not require the same stringent alignment of radio wave polarization as linear polarization. Furthermore, circularly polarized antennas can transmit and receive signals at various angles and in various environments, effectively reducing multipath distortion. These antennas are ideally suited for use in low-orbit satellite phased array antennas, radar phased array antennas, and 5G base station phased array antennas. Furthermore, the increasing use of broadband transmission in wireless communications in recent years has posed new challenges in circularly polarized antenna technology development, such as miniaturization, wide bandwidth, high gain, and wideband axial ratio.

In view of this, the present invention provides a circular polarized antenna that meets the requirements of circular polarized antennas with wide bandwidth, high gain, and wideband axial ratio.

The present invention provides a circularly polarized antenna, comprising an antenna portion and a feeding portion stacked up and down, wherein the antenna portion is disposed on a first substrate, wherein the first substrate comprises a top layer, a middle layer, and a bottom layer, and wherein the antenna portion comprises: a first antenna unit, comprising a cross-shaped metal patch disposed on the top layer of the first substrate; a parasitic element, comprising four metal strips forming a square with four unconnected sides, disposed on the middle layer of the first substrate; and a second antenna unit, comprising a square metal patch disposed on the bottom layer. The bottom layer of the first substrate; the feeding part is arranged on the second substrate, the second substrate includes a top layer, a middle layer and a bottom layer, and the feeding part includes: a coupling slot, arranged on the top layer of the second substrate; a matching microstrip line, arranged on the middle layer of the second substrate; a feeding line, arranged on the bottom layer of the second substrate; a branch line coupler, arranged on the bottom layer of the second substrate, and the matching microstrip line is electrically connected between the feeding line and the branch line coupler through a via.

Preferably, the first substrate is welded to the second substrate.

Preferably, the high-frequency bandwidth of the operating frequency band is adjusted by adjusting the cut angle of the cross-shaped metal patch of the first antenna unit.

Preferably, adjusting the width of the four metal strips of the parasitic element adjusts the low-frequency bandwidth of the operating band.

Preferably, the coupling slot is used to couple the signal received by the antenna part and also to couple the signal transmitted by the feeding part; the coupling slot includes a first slot and a second slot, and the first slot and the second slot are combined into an eight-shaped shape.

Preferably, the branch line coupler includes: a first microstrip line in a closed loop shape; a receiving end connected to one side of the first microstrip line; a transmitting end connected to one side of the first microstrip line; a first feeding end connected to the other side of the first microstrip line; and a second feeding end connected to the other side of the first microstrip line.

Preferably, the feed line includes a first feed line and a second feed line, and the first feed line and the second feed line are combined in a figure eight shape; the matching microstrip line includes a first matching microstrip line and a second matching microstrip line, and the first matching microstrip line and the second matching microstrip line are combined in a figure eight shape; the first matching microstrip line is electrically connected between the first feed line and the first feed end of the branch line coupler through a first via and a second via; the second matching microstrip line is electrically connected between the second feed line and the second feed end of the branch line coupler through a third via and a fourth via.

Preferably, the first feed line excites a field pattern in a horizontal polarization direction; and the second feed line excites a field pattern in a vertical polarization direction.

Preferably, when the signal enters the branch line coupler from the transmitting end, a left-handed circular polarization field pattern can be excited; when the signal enters the branch line coupler from the receiving end, a right-handed circular polarization field pattern can be excited.

The present invention also provides a communication system comprising any of the circularly polarized antennas described above.

Compared to existing technologies, the circularly polarized antenna provided by the present invention comprises a stacked antenna section and a feed section, each of which is located on separate substrates. This makes the circularly polarized antenna reconfigurable, allowing for flexible replacement of the antenna module based on application requirements. The feed section's coupling slots, matching microstrip lines, feed lines, and branch line couplers are located on different layers of the second substrate. Layer replacement technology increases the substrate thickness, thereby increasing the achievable impedance range for impedance matching. This also increases gain bandwidth, axial ratio bandwidth, and return loss bandwidth, optimizing antenna performance.

To facilitate understanding and implementation of this application by those skilled in the art, the present application is further described below in conjunction with the accompanying drawings and embodiments. It should be understood that this application provides many applicable inventive concepts that can be implemented in a variety of specific forms. Those skilled in the art can utilize the details described in these or other embodiments, as well as other available structural, logical, and electrical variations, to implement the invention without departing from the spirit and scope of this application.

This specification provides different embodiments to illustrate the technical features of different embodiments of this application. The configuration of the components in the embodiments is for illustrative purposes only and is not intended to limit the present invention. Partial repetition of the figure numbers in the embodiments is for the purpose of simplifying the description and does not imply a correlation between different embodiments. The same element numbers used in the drawings and the specification represent the same or similar components. The illustrations in this specification are simplified and not drawn to exact proportions. For the sake of clarity and convenience, directional terms (such as top, bottom, up, down, and diagonal) are for the accompanying illustrations. The directional terms used in the following description are not intended to limit the scope of the present invention unless explicitly used in the scope of the application attached below.

Furthermore, in describing some embodiments of this application, the specification describes the methods and/or programs of this application in a specific order of steps. However, since the methods and programs are not necessarily implemented according to the specific order of steps described, they are not limited to the specific order of steps described. Those skilled in the art will recognize that other orders are also possible implementations. Therefore, the specific order of steps described in the specification is not intended to limit the scope of the patent application. Furthermore, the scope of the patent application for the methods and/or programs of this application is not limited to the order of execution of the steps as written, and those skilled in the art will understand that adjusting the order of execution of the steps does not depart from the spirit and scope of the invention.

Please refer to Figures 1 and 2. Figure 1 is a schematic diagram of the structure of a dual-polarization antenna according to one embodiment of the present invention. Figure 2 is a schematic diagram of the layered structure of the dual-polarization antenna according to one embodiment of the present invention. In this embodiment, the dual-polarization antenna 10 is primarily used in electronic devices such as satellite communication products and base stations. As shown in Figure 2, the dual-polarization antenna 10 is mounted on a circuit board 20. The circuit board 20 includes a top layer 201, a bottom layer 202, and a middle layer 203, the middle layer serving as a ground layer. As shown in Figure 1, a dual-polarization antenna 10 includes M array antenna units 100, a first polarization feed network 101, and a second polarization feed network 102. The M array antenna units 100 are disposed on a top layer 201 of a circuit board 20, where M is an integer greater than or equal to 1. Each array antenna unit 100 includes four antenna units (Anta-Antd), meaning that the dual-polarization antenna 10 is an M*4 array antenna. Each antenna unit is preferably a circular patch antenna, with the four antenna units disposed at the four corners of a square. To better illustrate the present invention, in this embodiment, M is set to 4, and a 4*4 array antenna unit is used as an example, but this is not limiting.

The first polarization feeding network 101 is disposed on the bottom layer 202 of the circuit board 20. The first polarization feeding network 101 includes a first feeding terminal F1 and four first feeding network sub-units 1011. The four first feeding network sub-units 1011 are connected via T-junctions. The first polarization feeding network 101 is used to divide the feed signal from the first feeding terminal F1 into 16 equal parts. Each first feeding network sub-unit 1011 corresponds to an array antenna unit 100. Each first feeding network sub-unit 1011 is electrically connected to the corresponding array antenna unit 100 through a first set of metal vias H1 (H1a-H1d). Each first feeding network sub-unit 1011 excites the corresponding array antenna unit through the first set of metal vias H1 to form a first polarization field.

The second polarization feed network 102 is disposed on the bottom layer 202 of the circuit board 20. The second polarization feed network 102 includes a second feed terminal F2 and four second feed network sub-units 1021. The four second feed network sub-units 1021 are connected via T-junctions. The second polarization feed network 102 is used to divide the feed signal from the second feed terminal F2 into 16 equal parts. Each second feeding network sub-unit 1021 corresponds to an array antenna unit 100. Each second feeding network sub-unit 1021 is electrically connected to the corresponding array antenna unit 100 through the second set of metal vias H2. Each second feeding network sub-unit 1021 excites the corresponding array antenna unit 100 through the second set of metal vias H2 (H2a-H2d), forming a second polarization field.

Specifically, in conjunction with Figure 3, Figure 3 is a schematic structural diagram of the first and second feeding network subunits of a dual-polarization antenna according to an embodiment of the present invention. As shown in the figure, each first feeding network subunit 1011 includes a first T-junction T1, a second T-junction T2, and a third T-junction T3. The first T-junction T1 includes an input end, a first output end, and a second output end. The first T-junction T1 is used to split the signal at the input end of the first T-junction into two equal parts. The second T-junction T2 includes an input end, a first output end, and a second output end. The input end of the second T-junction T2 is electrically connected to the first output end of the first T-junction T1 via a first microstrip line L1, and is used to split the output signal of the first output end of the first T-junction T1 into two equal parts. The third T-junction T3 includes an input, a first output, and a second output. The input of the third T-junction T3 is electrically connected to the second output of the first T-junction T1 via a second microstrip line L2, thereby splitting the output signal from the second output of the first T-junction T1 into two equal parts. The length of the first microstrip line L1 is equal to the length of the second microstrip line L2. The first and second outputs of the second T-junction T2 and the first and second outputs of the third T-junction T3 are electrically connected to the four antenna units in the array antenna unit 100 through metal vias. Referring to Figure 2 , the first and second output terminals of the second T-junction T2 of the first power-feeding network sub-unit 1011 are electrically connected to antenna units Anta and Antb via metal vias H1a and H1b, respectively. The first and second output terminals of the third T-junction T3 of the first power-feeding network sub-unit 1011 are electrically connected to antenna units Antc and Antd via metal vias H1c and H1d, respectively. The structure of the second power-feeding network sub-unit 1021 is identical to that of the first power-feeding network sub-unit 1011 and will not be further described here. As shown in the figure, the first output terminal and the second output terminal of the second T-junction T2a of the second feeding network sub-unit 1021 are electrically connected to the antenna units Anta and Antb respectively through metal vias H2a and H2b. The first output terminal and the second output terminal of the third T-junction T3a of the second feeding network sub-unit 1021 are electrically connected to the antenna units Antc and Antd respectively through metal vias H2c and H2d.

FIG4 is a schematic diagram illustrating the structure of the first polarization feeding network of a dual-polarization antenna according to one embodiment of the present invention. The first polarization feeding network 101 includes a first feeding terminal F1, a third feeding network subunit 1011a, a fourth feeding network subunit 1011b, a fifth feeding network subunit 1011c, a sixth network feeding subunit 1011d, a fourth T-junction T4, a fifth T-junction T5, and a sixth T-junction T6. The fourth T-junction T4 includes an input terminal, a first output terminal, and a second output terminal. The input terminal of the fourth T-junction T4 is electrically connected to the first feeding terminal F1 and is used to split the signal from the first feeding terminal F1 into two equal parts. The fifth T-junction T5 includes an input end, a first output end, and a second output end. The input end of the fifth T-junction T5 is electrically connected to the first output end of the fourth T-junction T4 via a third microstrip line L3. The first output end of the fifth T-junction T5 is electrically connected to the third feeding network sub-unit 1011a via a fifth microstrip line L5. The second output end of the fifth T-junction T5 is electrically connected to the fourth feeding network sub-unit 1011b via a sixth microstrip line L6. The sixth T-junction T6 includes an input, a first output, and a second output. The input of the sixth T-junction T6 is electrically connected to the second output of the fourth T-junction T4 via a fourth microstrip line L4. The first output of the sixth T-junction T6 is electrically connected to the fifth feed network sub-unit 1011c via a seventh microstrip line L7. The second output of the sixth T-junction T6 is electrically connected to the sixth feed network sub-unit 1011d via an eighth microstrip line L8. The first polarization feed network 101 divides the feed signal from the first feed port F1 into 16 equal parts. The third microstrip line L3 and the fourth microstrip line L4 are of equal length. Because the fifth and sixth microstrip lines L5 and L6 are not equal in length, the sixth microstrip line L6 is one wavelength longer than the fifth microstrip line L5. This ensures that the phase of the signal entering the third feeding network sub-unit 1011a is equal to the phase of the signal entering the fourth feeding network sub-unit 1011b. Similarly, the eighth microstrip line L8 is one wavelength longer than the seventh microstrip line L7.

In this embodiment, the structure of the second polarization feeding network 102 is the same as that of the first polarization feeding network 101 and will not be described again herein.

Please refer to Figure 5, which shows a schematic diagram of the S-parameter curve of a single antenna unit of a dual-polarization antenna according to an embodiment of the present invention. According to the S11 and S22 parameter curves, the return loss of a single antenna unit is below -10dB in the bandwidth covering the 24 GHz frequency band.

Please refer to Figure 6, which shows a schematic diagram of the S-parameter curve of a single array antenna unit of a dual-polarization antenna according to an embodiment of the present invention. According to the S11 and S22 parameter curves, the return loss of a single array antenna unit is below -10dB in the bandwidth covering the 24 GHz frequency band.

Please refer to Figure 7, which shows an S-parameter curve for a dual-polarization antenna according to an embodiment of the present invention. According to the S11 and S22 parameter curves, the dual-polarization antenna's return loss is below -10 dB across the 24 GHz frequency band.

Please refer to Figure 8, which shows the first polarization pattern of a dual-polarization antenna in the X-Z plane according to one embodiment of the present invention. As shown in the figure, the first polarization pattern has high directivity and high gain characteristics, meeting the performance requirements of an array antenna.

Please refer to Figure 9, which shows the first polarization pattern of a dual-polarization antenna in the Y-Z plane according to one embodiment of the present invention. As shown in the figure, the first polarization pattern has high directivity and high gain characteristics, meeting the performance requirements of an array antenna.

Please refer to Figure 10, which shows the second polarization pattern of a dual-polarization antenna in the X-Z plane according to one embodiment of the present invention. As shown in the figure, the second polarization pattern has high directivity and high gain characteristics, meeting the performance requirements of an array antenna.

Please refer to Figure 11, which shows the second polarization pattern of a dual-polarization antenna according to one embodiment of the present invention in the Y-Z plane. As shown in the figure, the second polarization pattern has high directivity and high gain characteristics, meeting the performance requirements of an array antenna.

Compared with the prior art, the dual-polarization antenna and electronic device provided by the embodiment of the present invention include M array antenna units, a first polarization feeding network and a second polarization feeding network. The M array antenna units are arranged on the top layer of the circuit board, and the first polarization feeding network and the second polarization feeding network are arranged on the bottom layer of the circuit board. The first polarization feeding network and the second polarization feeding network are fed by a probe through a metal via. The top-layer array antenna elements are excited to generate the first and second polarization patterns, achieving bipolarization without adding another array antenna. This reduces product size and meets the demand for miniaturization. The first and second polarization feed networks are also located on the same layer, achieving a bipolarization feed network layout using a single-layer design. This reduces the number of circuit board layers and lowers production costs. As shown in Figure 1, the circularly polarized antenna 10 comprises an antenna portion 100 and a feed portion 200 stacked on top of each other. The antenna portion 100 is mounted on a first substrate J1, which comprises a top layer T1, a middle layer M1, and a bottom layer B1. The antenna section 100 includes a first antenna unit Ant1, a parasitic element P1, and a second antenna unit Ant2. The first antenna unit Ant1 comprises a cross-shaped metal patch, located on the top layer T1 of the first substrate J1. The parasitic element P1, consisting of four metal strips forming a square with four disconnected edges, is located on the middle layer M1 of the first substrate J1. The second antenna unit Ant2 comprises a square metal patch, located on the bottom layer B1 of the first substrate J1.

The power supply unit 200 is mounted on the second substrate J2, which includes a top layer T2, a middle layer M2, and a bottom layer B2. In this embodiment, the first substrate J1 is soldered to the second substrate J2. Figure 2 shows the combined structure of the antenna and power supply units of a circularly polarized antenna according to one embodiment of the present invention. As shown, the bottom layer B1 of the first substrate J1 and the top layer T2 of the second substrate J2 are soldered together via BGA pads Pa, making the circularly polarized antenna 10 a reconfigurable antenna, allowing the antenna unit 100 to be flexibly replaced according to application requirements.

The feeding unit 200 includes a coupling slot S, a matching microstrip line L, a feed line F, and a branch-line coupler C. The coupling slot S is located on the top layer T2 of the second substrate J2, which is a grounded metal layer. The matching microstrip line L is located on the middle layer M2 of the second substrate J2. The feed line F is located on the bottom layer B2 of the second substrate J2. The branch-line coupler C is also located on the bottom layer B2 of the second substrate J2. The matching microstrip line L is electrically connected to the feed line F and the branch-line coupler C through vias.

In this embodiment, the coupling slot S can be used to couple signals received by the antenna unit 100 and signals transmitted by the feeding unit 200. The coupling slot S includes a first slot S1 and a second slot S2. The first slot S1 and the second slot S2 form an eight-shaped combination.

The branch line coupler C includes a first microstrip line A1, a receiving terminal RX, a transmitting terminal TX, a first feed terminal E1, and a second feed terminal E2. In conjunction with Figure 3, Figure 3 shows a schematic diagram of the structure of the branch line coupler C for a circularly polarized antenna according to one embodiment of the present invention. The first microstrip line A1 is in the shape of a closed loop. The receiving terminal RX is connected to one side of the first microstrip line A1, the transmitting terminal TX is connected to one side of the first microstrip line A1, the first feed terminal E1 is connected to the other side of the first microstrip line A1, and the second feed terminal E2 is connected to the other side of the first microstrip line A1.

In this embodiment, the feed lines F include a first feed line F1 and a second feed line F2. Together, they form a figure-eight shape. Regarding the signal transmitted by the antenna unit 100, the first feed line F1 and the second feed line F2 couple the transmitted signal to the first slot S1 and the second slot S2, respectively. This increases the isolation between the first and second feed lines F1 and F2. Furthermore, the shared ground metal layer between the first and second slots S1 and S2 shields the antenna pattern from interference from radiation from the feeding unit 200.

The matching microstrip line L includes a first matching microstrip line L1 and a second matching microstrip line L2. The first matching microstrip line L1 and the second matching microstrip line L2 form a figure-eight shape. The first matching microstrip line L1 is electrically connected between the first feed line F1 and the first feed end E1 of the branch line coupler C via a first via H1 and a second via H2. The second matching microstrip line L2 is electrically connected between the second feed line F2 and the second feed end E2 of the branch line coupler C via a third via H3 and a fourth via H4.

In this embodiment, the feed line F excites two polarization patterns through dual-feeding. The first feed line F1 is electrically connected to the first feed terminal E1, stimulating a horizontal polarization pattern, while the second feed line F2 is electrically connected to the second feed terminal E2, stimulating a vertical polarization pattern. For example, when a signal from the transmitter TX enters both sides of the first microstrip line A1, a signal with a 90-degree phase difference is generated at the output second feed terminal E2, and a signal with a 180-degree phase difference is generated at the first feed terminal E1. The phase difference between the two signals is 90 degrees, thus achieving a circular polarization phase condition. After passing through the matching microstrip line L, the signal enters the feed line F, where it excites two different polarization patterns. The first feed line F1 excites a horizontal polarization pattern, while the second feed line F2 excites a vertical polarization pattern. The signals excited by the feed line F in both polarization directions are then coupled to the first slot S1 and the second slot S2, and then to the second antenna element Ant2 of the antenna section 100. From the second antenna element Ant2, the signal is further coupled to the parasitic element P1 and the first antenna element Ant1, and finally radiates out to form a circularly polarized radiation pattern. The operating principle of the receiving end (RX) is similar to that of the transmitting end (TX). The antenna unit 100 first receives the radiated circularly polarized signal, which is then coupled to the feed unit 200 by the antenna unit 100. Finally, the signal is received by the receiving end (RX) of the coupler C. The transmitting end (TX) and receiving end (RX) of the branch-line coupler C do not operate simultaneously; only one can be transmitting or receiving at a time. The transmitting end (TX) and receiving end (RX) of the branch-line coupler C produce left-handed circularly polarized patterns and right-handed circularly polarized patterns, respectively. That is, when a signal enters the branch-line coupler C from the transmitting end (Tx), a left-handed circularly polarized pattern is generated. When a signal enters the branch-line coupler C from the receiving end (RX), a right-handed circularly polarized pattern is generated. To change the direction of the excited left-hand circular polarization pattern between right-hand and left-hand circular polarization, simply swap the transmitting end TX and the receiving end RX of the branch line coupler C. Therefore, regardless of whether the satellite station's antenna array has left-hand circular polarization or right-hand circular polarization, the circularly polarized antenna of the present invention can match it to obtain the same polarization direction, increasing the antenna's flexibility.

Please refer to Figures 4 and 5. Figure 4 shows a schematic diagram of the simulated and measured field patterns of the transmitting port of a circularly polarized antenna in the YZ plane, according to an embodiment of the present invention. Figure 5 shows a schematic diagram of the simulated and measured field patterns of the transmitting port of a circularly polarized antenna in the XZ plane, according to an embodiment of the present invention. Field measurements were taken at both the transmitting port TX and the receiving port RX. Because the transmitting port TX and the receiving port RX have symmetrical structures, the measured performance of the transmitting port and the receiving port RX are consistent. In this embodiment, using the transmitting port TX as an example, as shown in Figures 4 and 5, the measured gain and field patterns of the transmitting port TX are consistent with the simulated gain and field patterns. The measured gain values for the horizontal polarization feed end E1 on the XZ plane are 7dB, and for the vertical polarization feed end E2 on the YZ plane are 6.9dB, demonstrating that the circularly polarized antenna of the present invention achieves good results.

The radiation pattern of the circularly polarized antenna of this invention is ideal for use with satellites. This is primarily because the antenna's position relative to ground receiving stations and orbiting satellites is constantly shifting. If electromagnetic waves encounter reflection and refraction during propagation, their polarization direction deflects, leading to signal attenuation caused by polarization mismatch between the transmitter and receiver. However, circularly polarized x-ray signals experience minimal attenuation in inclement weather and can penetrate the ionosphere, unaffected by the Faraday effect generated by the Earth's north and south magnetic fields, thus ensuring communication quality.

Please refer to Figures 6, 7, and 8. Figure 6 shows a simulated and measured axial ratio curve for a circularly polarized antenna according to an embodiment of the present invention. Figure 7 shows a simulated and measured gain curve for a circularly polarized antenna according to an embodiment of the present invention. Figure 8 shows a simulated and measured echo loss curve for the transmitter TX of a circularly polarized antenna according to an embodiment of the present invention. As shown in Figure 6, the measured axial ratio bandwidth matches the simulation. The frequency range where the axial ratio is less than 3 dB is approximately 10.5 GHz to 14.6 GHz, and the axial ratio bandwidth is 4.1 GHz (32.8%). As shown in Figure 7, the simulated peak gain of the antenna exceeds 4 dB at frequencies between 10.5 GHz and 14.5 GHz. The measured results show that the peak gain exceeds 4 dB at frequencies between 10.4 GHz and 14.3 GHz, with a gain bandwidth of 3.9 GHz (31.2%). This bandwidth difference can be observed in the return loss curve. As shown in Figure 8, the measured return loss is slightly lower-frequency by approximately 200 MHz compared to the simulated one, which is consistent with the peak gain measurement results.

In this embodiment, the matching microstrip line L and the first feed line F1, the second feed line F2, and the branch line coupler C are arranged on different layers of the second substrate J2. The substrate thickness is increased by layer replacement technology, thereby increasing the achievable impedance range to achieve impedance matching.

Please refer to Figures 9-11. Figure 9 shows the structure with feed line F directly connected to branch line coupler C. Figure 10 shows the structure with feed line F and branch line coupler C connected via a matching microstrip line L with a layer swap. Figure 11 shows the gain curves for both the direct connection of feed line F and branch line coupler C and the layer swap connection of feed line F and branch line coupler C. As shown in Figure 11, when feed line F and branch line coupler C are directly connected, the antenna's peak gain bandwidth is greater than 4 dB (30.4%) from 10.7 GHz to 14.5 GHz. After swapping the layers of the feed line F and the branch line coupler C through the matching microstrip line L, the peak gain bandwidth is greater than 4 dB from 10.5 GHz to 14.5 GHz (32%), and the gain bandwidth has increased by 200 MHz.

Figure 12 shows the axial ratio curves when the feed line F is directly connected to the branch line coupler C and when the feed line F and branch line coupler C are connected after switching layers via the matching microstrip line L. As shown in the figure, when the feed line F and branch line coupler C are directly connected, the antenna's axial ratio bandwidth is less than 3 dB from 10.8 GHz to 14.5 GHz (29.6%). After switching layers via the matching microstrip line L, the axial ratio bandwidth is less than 3 dB from 10.5 GHz to 14.6 GHz (32.8%), increasing the axial ratio bandwidth by 400 MHz.

Figure 13 shows the return loss curves when the feed line F is directly connected to the branch line coupler C and when the feed line F and branch line coupler C are connected after switching layers via the matching microstrip line L. As shown in the figure, when the feed line F and branch line coupler C are directly connected, the frequency range where the antenna's return loss is less than 10 dB is 10.7 GHz to 14.4 GHz (29.6%). After switching layers via the matching microstrip line L, the frequency range where the return loss is less than 10 dB is 10.5 GHz to 14.5 GHz (32%), increasing the return loss bandwidth by 300 MHz.

By replacing the matching microstrip line L, the antenna's return loss bandwidth, gain bandwidth, and axial ratio bandwidth increased by 300 MHz, 200 MHz, and 400 MHz, respectively, optimizing antenna performance.

In this embodiment, the high-frequency operating bandwidth of antenna unit 100, which is not yet connected to branch line coupler C, is adjusted by adjusting the cut angle of the cross-shaped metal patch of the first antenna unit Ant1. Referring to Figures 14 and 15, Figure 14 is a schematic structural diagram of the first antenna unit of a circularly polarized antenna according to an embodiment of the present invention. Figure 15 is a frequency curve of the first antenna unit of a circularly polarized antenna according to an embodiment of the present invention with different cut angle sizes. As shown in the figure, when the cut angle C1 is 0 mm, i.e., no cut angle is present, no clear high-frequency point is obtained because the antenna's high-frequency impedance matching is poor without the cut angle. When the cut angle C1 is 1.15 mm, the high-frequency point is approximately 13.8 GHz. When the cut angle C1 is 1.65mm, the high-frequency point is approximately 14.3GHz. That is, within a certain range, the larger the cut angle C1, the higher the high-frequency point and the wider the bandwidth.

In this embodiment, the width of the four metal strips of parasitic element P1 is adjusted to adjust the low-band bandwidth of the operating band. Figures 16 and 17 are combined. Figure 16 is a schematic diagram of the structure of the parasitic element of a circularly polarized antenna according to an embodiment of the present invention. Figure 17 is a frequency curve of the metal strips of the parasitic element of a circularly polarized antenna according to an embodiment of the present invention at different widths. As shown in the figure, when the width W1 of the metal strips is 0, that is, when the parasitic element P1 is absent, the low-band point is approximately 12.2 GHz. When the width W1 of the metal strips is 1 mm, the low-band point is approximately 11.8 GHz. When the width W1 of the metal strip is 1.5mm, the low-frequency point is approximately 11.3GHz. That is, within a certain range, the larger the width W1 of the metal strip, the lower the low-frequency point and the wider the bandwidth.

Compared to existing technologies, the circularly polarized antenna provided by the present invention comprises a stacked antenna section and a feed section, each of which is located on separate substrates. This creates a reconfigurable antenna, allowing for flexible replacement of the antenna module based on application requirements. The feed section's coupling slots, matching microstrip lines, feed lines, and branch line couplers are located on different layers of the second substrate. Layer replacement technology increases the substrate thickness, thereby increasing the achievable impedance range for impedance matching. This also increases gain bandwidth, axial ratio bandwidth, and return loss bandwidth, optimizing antenna performance.

10: Circularly polarized antenna 100: Antenna section 200: Feed section J1: First substrate J2: Second substrate T1, T2: Top layers M1, M2: Middle layers B1, B2: Bottom layers Ant1: First antenna unit Ant2: Second antenna unit P1: Parasitic element Pa: Pad S: Coupling slot S1: First slot S2: Second slot L: Matching microstrip line L1: First matching microstrip line L2: Second matching microstrip line F: Feed line F1: First feed line F2: Second feed line C: Branch line coupler A1: First microstrip line RX: Receiver TX: Transmitter E1: First feed port E2: Second feed port H1-H4: First via - fourth via C1: Cutting Angle W1: Width

Figure 1 is a schematic diagram of the structure of a circularly polarized antenna according to an embodiment of the present invention. Figure 2 is a diagram showing the combined structure of the antenna portion and the power feeding portion of the circularly polarized antenna according to an embodiment of the present invention. Figure 3 is a schematic diagram showing the structure of the branch line coupler of the circularly polarized antenna according to an embodiment of the present invention. Figure 4 is a schematic diagram showing the simulated and measured field patterns of the transmitting port of the circularly polarized antenna in the YZ plane according to an embodiment of the present invention. Figure 5 is a schematic diagram showing the simulated and measured field patterns of the transmitting port of the circularly polarized antenna in the XZ plane according to an embodiment of the present invention. Figure 6 shows a simulated axial ratio curve and a measured axial ratio curve for a circularly polarized antenna according to an embodiment of the present invention. Figure 7 shows a simulated gain curve and a measured gain curve for a circularly polarized antenna according to an embodiment of the present invention. Figure 8 shows a simulated return loss curve and a measured return loss curve for the transmitting end of a circularly polarized antenna according to an embodiment of the present invention. Figure 9 shows a schematic diagram of a structure in which a feed line is directly connected to a branch line coupler according to an embodiment of the present invention. Figure 10 shows a schematic diagram of a structure in which a feed line is connected to a branch line coupler via a matching microstrip line layer switch according to an embodiment of the present invention. Figure 11 shows a schematic diagram of gain curves when the feed line is directly connected to the branch line coupler, and a schematic diagram of gain curves when the feed line and the branch line coupler are connected via a matching microstrip line after layer swapping, according to an embodiment of the present invention. Figure 12 shows a schematic diagram of axial ratio curves when the feed line is directly connected to the branch line coupler, and a schematic diagram of axial ratio curves when the feed line and the branch line coupler are connected via a matching microstrip line after layer swapping, according to an embodiment of the present invention. Figure 13 shows a schematic diagram of return loss curves when the feed line and the branch line coupler are directly connected, and a schematic diagram of return loss curves when the feed line and the branch line coupler are connected via a matching microstrip line after layer swapping, according to an embodiment of the present invention. Figure 14 is a schematic diagram of the structure of the first antenna unit of a circularly polarized antenna according to an embodiment of the present invention. Figure 15 is a graph showing the frequency curves of the first antenna unit of a circularly polarized antenna according to an embodiment of the present invention at different cut angles. Figure 16 is a schematic diagram of the structure of a parasitic element of a circularly polarized antenna according to an embodiment of the present invention. Figure 17 is a graph showing the frequency curves of the metal strip of the parasitic element of a circularly polarized antenna according to an embodiment of the present invention at different widths.

without

10: Circularly polarized antenna

100: Antenna Department

200: Feeding part

J1: First substrate

J2: Second substrate

T1, T2: Top floor

M1, M2: Middle layer

B1, B2: bottom layer

Ant1: First antenna unit

Ant2: Second antenna unit

P1: Parasitic Components

S: Coupling slot

S1: First slot

S2: Second slot

L: Matching microstrip line

L1: First matching microstrip line

L2: Second matching microstrip line

F: Feed Line

F1: First Feed Line

F2: Second feed line

C: Branch Line Coupler

H1-H4: First via - fourth via

Claims (10)

A circularly polarized antenna comprises an antenna portion and a power feeding portion stacked one above the other, wherein: The antenna portion is disposed on a first substrate, the first substrate comprising a top layer, a middle layer, and a bottom layer. The antenna portion comprises: A first antenna unit comprising a cross-shaped metal patch disposed on the top layer of the first substrate; A parasitic element comprising four metal strips forming a square with four unconnected sides disposed on the middle layer of the first substrate; A second antenna unit comprising a square metal patch disposed on the bottom layer of the first substrate; The power feeding portion is disposed on a second substrate, the second substrate comprising a top layer, a middle layer, and a bottom layer. The power feeding portion comprises: A coupling slot disposed on the top layer of the second substrate; A matching microstrip line disposed on the middle layer of the second substrate; A feed line is disposed on the bottom layer of the second substrate. A branch line coupler is disposed on the bottom layer of the second substrate. The matching microstrip line is electrically connected between the feed line and the branch line coupler through a via. The circularly polarized antenna as described in claim 1, wherein the first substrate is welded to the second substrate. The circularly polarized antenna as described in claim 1, wherein the high-frequency bandwidth of the operating frequency band is adjusted by adjusting the cut angle size of the cross-shaped metal patch of the first antenna unit. The circularly polarized antenna of claim 1, wherein adjusting the width of the four metal strips of the parasitic element adjusts the low-frequency bandwidth of the operating band. The circularly polarized antenna of claim 1, wherein: The coupling slot is used to couple signals received by the antenna portion and also to couple signals transmitted by the feeding portion; The coupling slot includes a first slot and a second slot, the first slot and the second slot forming a figure eight shape. The circularly polarized antenna of claim 1, wherein the branch line coupler comprises: a first microstrip line in a closed loop shape; a receiving end connected to one side of the first microstrip line; a transmitting end connected to one side of the first microstrip line; a first feed end connected to the other side of the first microstrip line; and a second feed end connected to the other side of the first microstrip line. The circularly polarized antenna of claim 6, wherein: the feed line comprises a first feed line and a second feed line, the first feed line and the second feed line forming a figure-eight shape; the matching microstrip line comprises a first matching microstrip line and a second matching microstrip line, the first matching microstrip line and the second matching microstrip line forming a figure-eight shape; the first matching microstrip line is electrically connected between the first feed line and the first feed end of the branch line coupler via a first via and a second via; the second matching microstrip line is electrically connected between the second feed line and the second feed end of the branch line coupler via a third via and a fourth via. The circularly polarized antenna of claim 7, wherein: a horizontal polarization pattern is excited by the first feed line; a vertical polarization pattern is excited by the second feed line. The circularly polarized antenna of claim 7, wherein: When a signal enters the branch line coupler from the transmitting end, a left-handed circular polarization pattern is excited; When a signal enters the branch line coupler from the receiving end, a right-handed circular polarization pattern is excited. A communication system comprises the circularly polarized antenna as claimed in any one of claims 1 to 9.