Multi-branch circularly polarized antenna and communication equipment

Abstract

The invention provides a multi-branch circularly polarized antenna and communication equipment, the multi-branch circularly polarized antenna comprises a PCB and a plurality of branches arranged on the PCB, the center of the top layer of the PCB is provided with a feeding point, the feeding point is connected with a radio frequency port of the antenna through an impedance matching circuit, the top layer of the PCB is also provided with a reference ground plane, and the impedance matching circuit is connected with the radio frequency port of the antenna through the impedance matching circuit. Each branch knot comprises a straight line wire located on the top layer of the PCB and an oblique line wire located on the bottom layer of the PCB, the straight line wires and the oblique line wires are connected to form a continuous spiral broken line structure, and a tuning device is connected in series in the middle of a spiral broken line of each branch knot. The plurality of branches comprise at least one feed branch and at least two ground branches, the head end of the feed branch is connected with the feed point, and the tail end of the feed branch is suspended; the head ends of the at least two ground branches are jointly connected to the reference ground plane, and the tail ends are suspended. Through the broken line type routing design of the plurality of branches, the multi-band and circular polarization characteristics of the antenna are realized, and the antenna debugging flexibility is improved.

Description

Technical Field

[0001] This application relates to the field of wireless communication technology, and in particular to a multi-stub circularly polarized antenna and communication device. Background Technology

[0002] In the field of wireless communication, antennas are key components for transmitting and receiving electromagnetic waves in space, and their performance directly affects communication quality. Based on their polarization, antennas can be classified into three types: linear polarization, circular polarization, and elliptical polarization. Circularly polarized antennas are widely used in satellite communication because they effectively reduce the impact of interference signals such as reflections, thereby improving communication quality. For example... Figure 1 The image shows a commonly used traditional circularly polarized microstrip antenna, consisting of a bottom base plate and an upper square antenna plate, both made of metal. The feed point is located slightly below the center of the antenna plate. Two corners along one diagonal of the antenna plate are beveled to achieve circular polarization. The choice of bevel angle depends on whether the radiated electromagnetic wave requires left-hand or right-hand circular polarization. However, while this traditional circularly polarized microstrip antenna has a relatively simple structure, it suffers from large size and difficulties in subsequent debugging. Summary of the Invention

[0003] In view of this, this application proposes a multi-stub circularly polarized antenna and communication device, which realizes the multi-band and circular polarization characteristics of the antenna through the zigzag routing design of multiple stubs, thereby improving the flexibility of antenna debugging.

[0004] In a first aspect, this application provides a multi-stub circularly polarized antenna, including a PCB board and multiple stubs disposed on the PCB board. A feed point is disposed at the center of the top layer of the PCB board, and the feed point is connected to the radio frequency port of the antenna through an impedance matching circuit. A reference ground plane is also disposed on the top layer of the PCB board. Each stub includes a straight trace located on the top layer of the PCB board and a diagonal trace located on the bottom layer of the PCB board, and they are connected to form a continuous spiral broken line structure through vias at both ends of the traces. A tuning device is connected in series in the middle of the spiral broken line of each stub. The plurality of branches include at least one feed branch and at least two ground branches. The first end of the at least one feed branch is connected to the feed point, and the second end is suspended. The first ends of the at least two ground branches are connected to the reference ground plane, and the second ends are respectively suspended. When the feed branch is energized, an alternating electromagnetic field is generated around it, which excites the at least two ground branches to achieve circularly polarized radiation.

[0005] As described above, the multi-stub circularly polarized antenna provided in this application comprises multiple stubs consisting of at least one feed stub and at least two ground stubs arranged on a double-sided PCB board. Each stub adopts a unique spiral-shaped structure and is connected in series with a tuning device. The feed stub's first end is connected to the feed point and its last end is suspended. The ground stub's first end is connected to the reference ground plane and its last end is suspended. This unique asymmetric suspended-ground structure allows the feed stub to excite its corresponding ground stub after being powered on, resulting in a mode with equal amplitude and a preset phase angle, thus achieving circularly polarized radiation. This helps to improve the antenna's radiation performance and circular polarization characteristics. Furthermore, the tuning device in the middle of each stub can be individually adjusted to its resonant frequency, enabling the antenna to support multiple frequency bands.

[0006] Optionally, the impedance matching circuit is a Π-type matching circuit, which includes a first inductor connected in series in the signal path, a first capacitor connected in parallel between the signal path and the reference ground, and a second inductor.

[0007] In summary, by employing a Π-type matching circuit, an effective solution is provided for achieving broadband and efficient impedance matching between the antenna and the RF front-end within a compact structure. This circuit can flexibly compensate for the inductive or capacitive components in the antenna's input impedance, maximizing energy transfer efficiency, reducing return loss, and ensuring the antenna's radiation performance and effectiveness in the target frequency band.

[0008] Optionally, the plurality of branches includes three branches that are centrally symmetrically distributed, with an angle of 120 degrees between adjacent branches, and the three branches include one power supply branch and two ground branches; By configuring the parameters of the tuning device connected in series with two ground stubs to have a preset difference, the feed stub and the two ground stubs together generate two resonant modes with a preset angle and a preset phase difference in the target frequency band, thereby making the antenna exhibit circularly polarized radiation characteristics in the target frequency band.

[0009] As described above, by setting the tuning device parameters of the two ground stubs to a "preset difference," a slight split (one slightly higher, one slightly lower) can be artificially created between the two resonant mode frequencies generated by the coupling between the two ground stubs and the feed stub. At the center frequency, these two modes naturally form the desired preset phase difference, thereby reliably switching the antenna from linear polarization to circular polarization.

[0010] Optionally, the two ground nodes are designated as a first ground node and a second ground node, and the positive or negative relationship of the preset difference is used to control the rotation direction of the circular polarization radiation characteristics; specifically: When the tuning device parameter value of the first stub is greater than that of the tuning device parameter value of the second stub, the antenna exhibits circular polarization characteristics in the first direction in the corresponding target frequency band. When the tuning device parameter value of the first stub is less than that of the tuning device parameter value of the second stub, the antenna exhibits circular polarization characteristics in the corresponding target frequency band with a second rotation direction opposite to the first rotation direction.

[0011] As shown above, the circular polarization direction (left-handed LHCP or right-handed RHCP) is directly determined by setting the positive and negative relationship of the preset difference. This means that the circular polarization direction of the antenna can be reversed simply by swapping the parameter values ​​of the tuning devices on the two stubs. This allows the same antenna platform to be adapted to communication systems with different polarization requirements, greatly improving the versatility and application range of the antenna.

[0012] Optionally, the plurality of branches includes four branches arranged in a cross-shaped symmetrical distribution, wherein two adjacent branches are power supply branches and the other two branches are ground branches; In this configuration, a feed stub and a ground stub located on the same axis constitute an antenna resonant unit. The two antenna resonant units are configured to operate in different target frequency bands. By adjusting the parameters of the tuning devices connected in series, the two antenna resonant units generate two resonant modes with a preset angle and a preset phase difference in the target frequency band, thereby realizing the dual-frequency dual-circular polarization radiation characteristics of the antenna.

[0013] As described above, through a cross-symmetrical four-stub layout and parallel feeding design, the feed stubs and ground stubs located on the same axis constitute an antenna resonant unit, thereby constructing two relatively independent antenna resonant units. This enables the antenna to operate simultaneously in two different target frequency bands and generate circularly polarized waves in both frequency bands. Furthermore, the two antenna resonant units are spatially distributed at a preset angle, which helps to reduce mutual coupling interference between them and ensures the independence and performance stability of dual-frequency dual-mode operation.

[0014] Optionally, the tuning device is an inductor, a capacitor, or a tuning circuit composed of an inductor and a capacitor; The tuning circuit is composed of a third inductor and a second capacitor connected in series, and then connected in parallel with a fourth inductor.

[0015] As described above, the series-parallel connection of inductors and capacitors allows a single tuning circuit to exhibit the desired inductive or capacitive impedance at multiple different frequency points. This allows the antenna structure to support two or more discrete operating frequency bands within the same physical size, and to achieve circularly polarized radiation in each band through the aforementioned switching mechanism, thereby significantly improving the antenna's spectral efficiency and versatility in application scenarios.

[0016] Optionally, the tuning device is a switching tuning circuit, which is composed of a fifth inductor and a switching device connected in series, and then connected in parallel with a sixth inductor. The switching device is controlled by a controller, and the equivalent inductance value of the ground stub is adjusted by switching the on and off state of the switching device, so that the antenna switches between multiple frequency bands.

[0017] As described above, by replacing fixed tuning devices with controlled switching tuning circuits, the equivalent inductance of each stub can be switched in real time via electrical signals, thereby adjusting the resonant frequency of each stub. This upgrades the antenna from fixed multi-frequency to reconfigurable multi-frequency. By controlling all switches, the antenna can be selected to operate in up to eight preset frequency bands, or these frequency points can be combined to form an extremely wide bandwidth, dynamically adapting to different communication standards or frequency band requirements.

[0018] Optionally, adjusting the equivalent inductance of the ground stub by switching the on / off state of the switching device specifically includes: When the switching device is turned on, the fifth inductor and the sixth inductor are connected in parallel to form the first equivalent inductance value; When the switching device is disconnected, only the sixth inductor is connected to the circuit to form the second equivalent inductance value; By switching the state of the switching device, the ground stub can be switched between two resonant frequencies.

[0019] As described above, by controlling the parallel inductor combination or the connection of a single inductor through a switch, two discrete and significantly different equivalent inductance values ​​can be obtained. This circuit structure has advantages such as simplicity, reliability, fast switching speed, and clear control logic, ensuring flexible adjustment of the equivalent inductance of each branch.

[0020] Secondly, this application provides a communication device, including the aforementioned multi-stub circularly polarized antenna.

[0021] These and other aspects of this application will become more apparent in the description of the following embodiments(s). Attached Figure Description

[0022] Figure 1 This is a top view of the structure of a commonly used traditional circularly polarized microstrip antenna; Figure 2 A top view of a three-stub circularly polarized antenna provided in an embodiment of this application; Figure 3a This is a schematic diagram of the straight traces on the top layer of the PCB board in an embodiment of this application; Figure 3b This is a schematic diagram of the diagonal traces on the bottom layer of the PCB board in an embodiment of this application; Figure 4A circuit diagram of a first type of three-stalk circularly polarized antenna provided for embodiments of this application; Figure 5 A circuit diagram of a second type of three-stub circularly polarized antenna provided in an embodiment of this application; Figure 6 A circuit diagram of a third type of three-stalk circularly polarized antenna provided in an embodiment of this application; Figure 7 A top view of a four-stub circularly polarized antenna provided in an embodiment of this application; Figure 8a This is a schematic diagram of the straight traces on the top layer of the PCB board in an embodiment of this application; Figure 8b This is a schematic diagram of the diagonal traces on the bottom layer of the PCB board in an embodiment of this application; Figure 9 A circuit diagram of a first type of four-stub circularly polarized antenna provided for embodiments of this application; Figure 10 A circuit diagram of a second type of four-stub circularly polarized antenna provided in an embodiment of this application; Figure 11 A circuit diagram of a third type of four-stub circularly polarized antenna provided in an embodiment of this application; Figure 12 A top view of a five-stalk circularly polarized antenna provided in an embodiment of this application; Figure 13 This is a top view of a six-stalk circularly polarized antenna provided in an embodiment of this application.

[0023] It should be understood that the dimensions and shapes of the block diagrams in the above structural diagrams are for reference only and should not constitute an exclusive interpretation of the embodiments of this application. The relative positions and inclusion relationships between the block diagrams presented in the structural diagrams are only schematic representations of the structural relationships between the block diagrams, and are not intended to limit the physical connection methods of the embodiments of this application. Detailed Implementation

[0024] The technical solutions provided in this application will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the system architecture and business scenarios provided in the embodiments of this application are mainly for illustrating possible implementations of the technical solutions of this application and should not be construed as the sole limitation on the technical solutions of this application. Those skilled in the art will recognize that the technical solutions provided in this application are equally applicable to similar technical problems as system architectures evolve and new business scenarios emerge.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the scope of this application.

[0026] The solutions provided in this application will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] This application proposes a multi-segment circularly polarized antenna, specifically implementing an innovative antenna physical structure and tuning method. Utilizing double-sided printed circuit board (PCB) technology, the antenna is designed with five centrally symmetrically distributed spiral zigzag segments. By connecting tunable passive devices or switchable circuit networks in series in each segment, flexible configuration and reconfiguration of the antenna's operating frequency, bandwidth, polarization mode (linear / circular polarization), and circular polarization direction are achieved. This solution effectively solves the problems of large size, difficult tuning, and limited functionality of traditional circularly polarized antennas.

[0028] like Figures 2-3b As shown in the embodiment of this application, a three-stalk circularly polarized antenna is provided. This antenna is constructed based on a dielectric substrate (i.e., a PCB). A feed point and a reference ground plane are respectively disposed on the top layer of the PCB. The feed point is located on the top layer of the PCB, and the reference ground plane is located near the feed point. Three sets of radially distributed straight traces (such as...) are etched on the top layer of the PCB. Figure 3a As shown), three sets of diagonal traces corresponding to the top layer traces are etched on the bottom layer of the PCB board (e.g., Figure 3b As shown), each group of top-layer traces and the corresponding bottom-layer traces are electrically connected through metal vias at both ends, forming a continuous spiral zigzag structure with a spatial spiral feel. Each spiral zigzag structure is a branch, and a tuning device is connected in series in the middle of the spiral zigzag structure of each branch.

[0029] Of the three branches, the one located directly above (with) Figure 2 Taking the orientation shown as an example, one of the feed stubs is defined as the feed stub, and the other two stubs are distributed on both sides of the feed stub, defined as ground stub 1 and ground stub 2 respectively. The beginning of the feed stub (i.e., the starting point of the spiral broken line structure, near the center of the PCB board) is connected to the feed point located at the center of the top layer of the PCB board. This feed point is connected to an external RF port through an impedance matching circuit to match the input impedance of the antenna to the system standard impedance (usually 50Ω). The end of the feed stub (i.e., the end point of the spiral broken line structure) is left floating. The beginnings of the two ground stubs are connected to the reference ground plane, and the ends of the two ground stubs are left floating.

[0030] When the antenna is operating, the radio frequency signal directly excites the feed stub through the impedance matching circuit and the feed point, causing it to generate alternating current and an electromagnetic field. Since the two ground stubs are tightly coupled to the feed stub through space, their near fields overlap. Therefore, the electromagnetic field of the feed stub effectively excites the current on the two ground stubs. Each ground stub and the feed stub together form a resonant circuit, the resonant frequency of which is determined by the physical length (electrical length) of the feed stub and the ground stub themselves, as well as the values ​​of the tuning devices connected in series. By setting different tuning device parameters for different ground stubs, multiple different resonant frequency points can be formed by coupling them with the feed stub, thus enabling multi-band operation of the antenna.

[0031] To achieve good signal transmission, the impedance matching circuit in this application embodiment has been preferably designed. For example... Figure 4 As shown, the matching circuit can be specifically implemented as a Π-type matching circuit, which includes an inductor L1 connected in series in the signal path, a capacitor C1 connected in parallel between the signal path and the reference ground, and an inductor L2. By properly selecting the values ​​of L1, C1, and L2, the impedance flowing from Port1 (i.e., the RF port) to the antenna within the target operating frequency band can be made close to the standard impedance of 50Ω, thereby maximizing power transmission efficiency and improving the antenna's VSWR and return loss performance.

[0032] In some embodiments, the tuning devices in each branch can be selected as inductors, capacitors, or a combination of inductors and capacitors. For example... Figure 4 As shown, the tuning device can be an inductor, where L01 is the tuning device for the feed stub, and L02 and L03 correspond to the tuning devices for ground stubs 1 and 2, respectively. Port1 is connected to the antenna feed point through an impedance matching circuit. In actual use, the length and spacing of the broken lines are designed first according to the target antenna operating frequency and the required antenna size. The broken line spacing mainly affects the overall length of the antenna broken line trace. The lower the target antenna operating frequency, the longer the broken line trace needs to be. Therefore, the smaller the spacing, the more times the trace can be bent. The longer the trace, the closer the resonant frequency of the antenna trace alone is to the target frequency. The frequency is then supplemented by intermediate tuning devices to adjust the zigzag pattern to the target operating frequency. However, the smaller the spacing, the longer and denser the traces, resulting in poorer antenna radiation. The supplementary value of the tuning device can be smaller, and the device loss performance is lower. Conversely, the larger the zigzag spacing, the shorter the traces, and the better the zigzag radiation performance. However, larger tuning devices are required, and the device loss is greater. In actual use, the approximate antenna spacing is determined by comparing the best antenna radiation effect after different spacings and device supplementation. The length of the zigzag pattern is determined by the size of the antenna board. Try to fill the board as much as possible to maximize the trace area and improve the antenna radiation effect.

[0033] The following is based on Figure 2 Antenna structure and Figure 4The circuit structure is used to illustrate how to achieve circular polarization in a specific target frequency band: First, disconnect one of the ground stubs 2. Based on the target antenna operating frequency, determine the value of the tuning device L01 in the middle of the feed stub directly above and the tuning device L02 in the other ground stub 1. Make their device (usually inductor) values ​​similar, setting the inductance value to LN. Ensure the antenna operating frequency is at the target operating frequency f0. Then, based on the target circular polarization characteristics and rotation requirements (e.g., whether the antenna needs left-hand or right-hand circular polarization), if it's a right-hand circular polarization antenna design, set the tuning device value of the lower right ground stub 1 (slightly larger than LN) to be based on the inductance value LN, and set the tuning device value of the lower left ground stub 2 (slightly smaller than LN). With the inductance value LN, after this design, the feed stub directly above and the two ground stubs respectively form two antenna resonant modes with similar operating frequencies. The antenna resonant mode formed by the feed stub and the lower right ground stub 1 has an operating frequency slightly lower than the target operating frequency f0 by f0-k (k value is greater than zero and very small), and lags behind the phase at f0 frequency. The antenna resonant mode formed by the feed stub and the lower left ground stub 2 has an operating frequency slightly higher than the target operating frequency f0 by f0+k (k value is greater than zero and very small), and leads the phase at f0 frequency. Furthermore, the two resonant modes are rotated by 120 degrees. In this way, a right-hand circularly polarized antenna design with an operating frequency in the f0 band can be achieved.

[0034] Conversely, if the target antenna polarization is a left-hand circular polarization antenna, then simply reverse the left and right sides of the tuning devices L02 and L03 of the two ground stubs designed above. This will enable the design of a left-hand circular polarization antenna operating in the f0 frequency band.

[0035] This embodiment also enables the design of a dual-band antenna scheme. First, disconnect one ground stub 2. Adjust the value of the tuning device L02 of the other ground stub 1 to the operating frequency f1 of the antenna resonant mode formed by this ground stub and the tuning device L01 of the feed stub directly above. The values ​​of L01 and L02 are close. Then, disconnect this L02 path, connect the other ground stub 2, and adjust the value of the tuning device L03. Change the value of the tuning device L01 of the feed stub to the operating frequency f2 of the antenna resonant mode formed by this ground stub and the tuning device L01 of the feed stub directly above. At this point, the values ​​of L01 and L03 are close. Then, take two adjustments to the tuning device L01 of the feed stub. Keeping the average value near the baseline, while considering both frequency bands, readjust the L03 value to the antenna resonant mode operating frequency f2, which is the latest device value of the tuning device L01 in the feed stub directly above. Then, open port L03, reconnect the L02 path, and adjust the L02 value to the antenna resonant mode operating frequency f1, which is the latest device value of the tuning device L01 in the feed stub directly above. Then, simultaneously connect the stubs of L02 and L03 paths. In this way, a dual-band antenna design can be achieved, with the antenna operating at both f1 and f2. This expands the antenna bandwidth and adapts to a wider range of antenna usage scenarios. However, at this time, the antenna exhibits linear polarization antenna characteristics at both operating frequencies f1 and f2.

[0036] In some embodiments, if it is required that the antenna operates in two frequency bands, and both dual-band antennas are circularly polarized, it is only necessary to adjust the tuning devices of the above three branches as follows: Figure 5 Taking the feed branch as an example, the circuit design scheme replaces the fixed inductor L01 with a tuning network. This tuning network consists of inductor L11 and capacitor C11 connected in series, and then inductor L12 connected in parallel. The formula for calculating the equivalent impedance characteristic of this circuit is Im1=(ω2*L11*C11-1)L12C11 / (L11C11+L12C11-1), where ω=2*π*f (f is the operating frequency of the antenna target). Through this circuit design, the equivalent impedance of this circuit can achieve a larger inductance value at lower frequencies and a smaller inductance value at higher frequencies. Therefore, the tuning network is replaced with the above... Figure 4 All the tuning devices (L01, L02, L03) can enable each ground stub, feed stub, and tuning device network to form two antenna resonant modes with different operating frequencies. For example, the two resonant modes formed by the feed stub and the lower right ground stub have operating frequencies of f11+k1 and f21+k2 (k1 and k2 are both greater than zero and very small), and the two resonant modes formed by the feed stub and the lower left ground stub have operating frequencies of f11-k1 and f21-k2 (k1 and k2 are both greater than zero and very small). In this way, an antenna design with right-hand circular polarization in both the f11 and f21 dual-band frequencies can be achieved.

[0037] Conversely, if the target antenna polarization is two dual-band left-hand circularly polarized antennas, then it is only necessary to reverse the middle circuit of the two reference ground stubs as designed above, so as to realize the design of a left-hand circularly polarized antenna scheme with the operating frequency in the f0 band.

[0038] In some embodiments, the operating frequencies of the two resonant modes of the feed stub and ground stub can be adjusted to f11+k1 and f21-k2 (where k1 and k2 are both greater than zero and very small) respectively. The operating frequencies of the two resonant modes formed by the feed stub and the lower left ground stub can also be f11-k1 and f21+k2 (where k1 and k2 are both greater than zero and very small). This allows for the design of an antenna scheme with right-hand circular polarization at frequency f11 and left-hand circular polarization at frequency f21, thus achieving a dual-circular polarization dual-band antenna design. Alternatively, the two ground stubs can be adjusted to operate in two different frequency bands, allowing a total of four frequency bands to operate simultaneously. This achieves the effect of a three-stub antenna supporting up to four frequency bands, or simultaneously adjusting to adjacent frequency bands can greatly expand the antenna bandwidth.

[0039] To further enhance the flexibility and intelligence of antennas, this invention proposes a scheme to replace fixed tuning devices with switched tuning circuits, such as... Figure 6 As shown, taking ground stub 1 as an example, its fixed inductor L02 is replaced by a switching tuning circuit. This switching tuning circuit includes an inductor L32 connected in series with the stub trace and a branch connected in parallel with the inductor L32. This branch consists of an inductor L31 and a single-pole single-throw (SPST) switch S2 connected in series. The switch S2 is controlled by a GPIO pin of the controller U1. Based on the structure of this switching tuning circuit, when the controller U1 outputs a control signal to open the switch S2, the branch of inductor L31 is not connected, and only inductor L32 is connected in series with ground stub 1. Let the equivalent inductance at this time be Leq_off = L32, corresponding to a resonant frequency F_off; when the controller U1 outputs a control signal to open the switch S2, inductors L31 and L32 form a parallel relationship. The total equivalent value of the parallel inductors is Leq_on = (L31*L32) / (L31+L32), which is less than L32. Therefore, the equivalent inductance of ground stub 1 decreases, corresponding to another higher resonant frequency F_on.

[0040] By designing a switching tuning circuit, a single stub can electrically switch between two preset frequencies. Applying this switching circuit to all three stubs and independently controlling each switch using binary logic, the antenna can theoretically switch between various frequency combinations. Through careful design of the values ​​of the two inductors in the switching tuning circuit, it can be made to operate stably on four practically valuable frequency bands.

[0041] like Figures 7-8b As shown, this application embodiment also provides a four-stub circularly polarized antenna, which is constructed based on a dielectric substrate (i.e., a PCB board). A feed point and a reference ground plane are respectively disposed on the top layer of the PCB board. The feed point is located on the top layer of the PCB board, and the reference ground plane is located near the feed point. Four sets of radially distributed straight traces (such as...) are etched on the top layer of the PCB board. Figure 8a As shown), four sets of diagonal traces corresponding to the top layer traces are etched on the bottom layer of the PCB board (e.g. Figure 8b As shown), each group of top-layer traces and the corresponding bottom-layer traces are electrically connected through metal vias at both ends, forming a continuous spiral zigzag structure with a spatial spiral feel. Each spiral zigzag structure is a branch, and a tuning device is connected in series in the middle of the spiral zigzag structure of each branch.

[0042] The four branches are arranged in a cross-shaped symmetrical distribution. Two adjacent and perpendicular branches are connected in parallel, serving as both feed branches, while the other two branches serve as ground branches. The beginnings of the two feed branches (i.e., the starting points of the spiral-shaped structure, near the center of the PCB board) are connected to a feed point located at the center of the top layer of the PCB board. This feed point is connected to an external RF port through an impedance matching circuit to match the antenna's input impedance to the system's standard impedance (typically 50Ω). The ends of the two feed branches (i.e., the ending points of the spiral-shaped structure) are left floating. The beginnings of the two ground branches are connected to the reference ground plane, and the ends of the two ground branches are left floating. In the design of a dual-band antenna scheme, a feed stub and a ground stub located on the same axis are distributed to form an antenna resonant unit, thereby constructing two relatively independent antenna resonant units. The two antenna resonant units are configured to operate in different target frequency bands. By adjusting the parameters of the tuning devices connected in series, the two antenna resonant units can generate two resonant modes with a preset angle and a preset phase difference in the target frequency band, thereby realizing the dual-band dual-circular polarization radiation characteristics of the antenna.

[0043] like Figure 9As shown, when the antenna is operating, the radio frequency signal directly excites the two feed stubs through the impedance matching circuit and the feed point, causing them to generate alternating current and an electromagnetic field. This electromagnetic field, through a near-field coupling mechanism, excites the current on a nearby ground stub, thus forming effective radiation. For example, feed stub 1 and ground stub 1 on the same axis constitute one antenna operating mode (called mode A); feed stub 2 and ground stub 2 on the same axis constitute another antenna operating mode (called mode B). Since the physical length and trace spacing of the two sets of dual-stub structures can be designed independently, mode A and mode B can resonate at different frequencies, thereby achieving dual-frequency operation.

[0044] In some embodiments, if it is required that the antenna operates in two frequency bands, and both dual-band antennas are circularly polarized, it is only necessary to adjust the tuning devices of the above four stubs as follows: Figure 10 Taking feed stub 1 as an example, the fixed inductor L02 in the circuit design is replaced with a tuning network. This tuning network consists of inductor L21 and capacitor C21 connected in series, and then inductor L22 connected in parallel. The formula for calculating the equivalent impedance characteristic of this circuit is Im1=(ω2*L21*C21-1)L22C21 / (L21C21+L22C21-1), where ω=2*π*f (f is the operating frequency of the antenna target). Through this circuit design, the equivalent impedance of this circuit can be made to have a larger inductance value at lower frequencies and a smaller inductance value at higher frequencies. Therefore, the tuning network is replaced with the above... Figure 9 All the tuning devices (L02, L03, L04, L05) can enable each ground stub and the feed stub on the same axis to form two antenna resonant mode operating frequencies. The feed stub and ground stub on the same axis operate in two resonant modes, such as the f11+ or -k1 and f21+ or -k2 frequency bands. The feed stub and ground stub on the other axis operate in two resonant modes, such as the f11- or +k1 and f21- or +k2 frequency bands. This enables the design of a dual-frequency dual-circular polarization antenna scheme, and the antenna can achieve the same or different left-hand or right-hand circular polarization antenna characteristics at different frequencies.

[0045] In some embodiments, a switching tuning circuit can be used instead of a fixed tuning device, such as... Figure 11As shown, for example, the fixed inductor L03 can be replaced with a switching tuning circuit. This switching tuning circuit includes an inductor L32 connected in series with the stub trace, and a branch connected in parallel with the inductor L32. This branch consists of an inductor L31 and a single-pole single-throw (SPST) switch S2 connected in series. The switch S2 is controlled by a GPIO pin of the controller U1. Based on the structure of this switching tuning circuit, when the controller U1 controls the switch S2 to be open, the branch of inductor L31 is not connected, and only inductor L32 is connected in series with the ground stub 1. Let the equivalent inductance at this time be Leq_off = L32, corresponding to a resonant frequency F_off; when the controller U1 controls the switch S2 to be on, inductors L31 and L32 form a parallel relationship. The total equivalent value of the parallel inductors is Leq_on = (L31*L32) / (L31+L32), which is less than L32. Therefore, the equivalent inductance of ground stub 1 decreases, corresponding to another higher resonant frequency F_on.

[0046] By designing a switching tuning circuit, the feed stub and ground stub on the same axis can operate in two resonant mode frequency bands, such as f11+ or -k1 and f21+ or -k2, while the feed stub and ground stub on the other axis can operate in two resonant modes, such as f11- or +k1 and f21- or +k2. This enables the design of a four-stub dual-band dual-circular polarization antenna.

[0047] like Figure 12 As shown in the embodiment, the application also provides a five-segment circularly polarized antenna, which is also constructed based on a PCB board. The top layer of the PCB board has a feed point and a reference ground plane. Five sets of radially distributed straight traces are etched on the top layer of the PCB board, and five sets of diagonal traces corresponding to the top layer traces are etched on the bottom layer of the PCB board. Each set of top layer traces and the corresponding bottom layer traces are electrically connected through metal vias at both ends, forming a continuous spiral zigzag structure with a spatial spiral feel. Each spiral zigzag structure is a segment, and a tuning device is connected in series in the middle of the spiral zigzag structure of each segment.

[0048] Of the five branches, the one located directly above (with) Figure 12Taking the orientation shown as an example, one stub is defined as the feed stub, and the other four stubs are evenly distributed around it circumferentially, defined as ground stub 1, ground stub 2, ground stub 3, and ground stub 4, respectively. Ground stub 1 and ground stub 3 are spatially symmetrical about the feed stub, forming one pair; ground stub 2 and ground stub 4 are symmetrical about the left and right, forming another pair. This symmetrical layout provides the hardware physical basis for achieving good circular polarization characteristics. The starting end of each feed stub (i.e., the starting point of the spiral broken line structure, near the center of the PCB board) is connected to a feed point located at the center of the top layer of the PCB board. This feed point is connected to an external RF port through an impedance matching circuit to match the antenna's input impedance to the system standard impedance. The ending end of the feed stub (i.e., the ending point of the spiral broken line structure) is suspended. The starting ends of the four ground stubs are connected to the reference ground plane, and the ending ends of the four ground stubs are suspended.

[0049] When the antenna is operating, the radio frequency signal directly excites the feed stubs through the impedance matching circuit and the feed point, causing them to generate alternating current and electromagnetic fields. Since the four ground stubs are tightly coupled to the feed stubs in space, their near-fields overlap. Therefore, the electromagnetic field of the feed stubs effectively excites the current on the four ground stubs. Each ground stub and the feed stub together form a resonant circuit, the resonant frequency of which is determined by the physical length (electrical length) of the feed stub and ground stub themselves, as well as the values ​​of the tuning devices connected in series. By setting different tuning device parameters for different ground stubs, multiple different resonant frequency points can be formed by coupling them with the feed stubs, thus enabling multi-band operation of the antenna.

[0050] like Figure 13 As shown in the embodiment, the application also provides a six-stub circularly polarized antenna, which is also constructed based on a PCB board. The top layer of the PCB board has a feed point and a reference ground plane. Six sets of radially distributed straight traces are etched on the top layer of the PCB board, and six sets of diagonal traces corresponding to the top layer traces are etched on the bottom layer of the PCB board. Each set of top layer traces and the corresponding bottom layer traces are electrically connected through metal vias at both ends, forming a continuous spiral zigzag structure with a spatial spiral feel. Each spiral zigzag structure is a stub, and a tuning device is connected in series in the middle of the spiral zigzag structure of each stub.

[0051] Of the six branches, the one located directly above (with) Figure 13Taking the orientation shown as an example, two feed stubs are defined as feed stub 1 and feed stub 2, respectively. The remaining four stubs are evenly distributed around these two feed stubs in the circumference and are defined as ground stub 1, ground stub 2, ground stub 3, and ground stub 4, respectively. Ground stub 1 and ground stub 3 are symmetrically distributed on both sides of feed stub 1, with the same trace width and spacing. This three-stub structure constitutes the first operating state of the antenna. Ground stub 2 and ground stub 4 are symmetrically distributed on both sides of feed stub 2, with the same trace width and spacing. This three-stub structure constitutes the second operating state of the antenna. This symmetrical layout provides the hardware physical basis for achieving good circular polarization characteristics. In some embodiments, to achieve multi-frequency design, the trace width and spacing of the two sets of three-stub structures can be different. That is, the total trace length of one set of three-stub structures is shorter, suitable for high-frequency antenna operating states, while the total trace length of the other set of three-stub structures is longer, suitable for low-frequency antenna operating states, ensuring good antenna performance.

[0052] The two feed stubs (i.e., the starting points of the spiral-shaped structure, near the center of the PCB board) are connected to a feed point located at the center of the top layer of the PCB board. This feed point is connected to an external RF port through an impedance matching circuit to match the antenna's input impedance to the system's standard impedance (typically 50Ω). The ends of the two feed stubs (i.e., the ending points of the spiral-shaped structure) are left floating. The four ground stubs are connected to the reference ground plane, and their ends are left floating.

[0053] When the antenna is operating, the radio frequency signal directly excites the two feed stubs through the impedance matching circuit and the feed point, causing them to generate alternating current and electromagnetic fields, respectively. This electromagnetic field, through a near-field coupling mechanism, excites the currents on the two adjacent ground stubs, thus forming effective radiation. Feed stub 1, together with its symmetrically distributed ground stubs 1 and 3 on either side, constitutes one antenna operating mode (referred to as Mode A); feed stub 2, together with its symmetrically distributed ground stubs 2 and 4 on either side, constitutes another antenna operating mode (referred to as Mode B). Since the physical lengths and trace spacing of the two sets of three-stub structures can be designed independently, Mode A and Mode B can resonate at different frequencies, thus achieving dual-frequency operation.

[0054] In summary, the multi-stub circularly polarized antenna provided in this application involves multiple stubs, each consisting of at least one feed stub and at least two ground stubs, arranged on a double-sided PCB board. Each stub employs a unique spiral-shaped structure with a series tuning device. The feed stub's first end is connected to the feed point, while its last end is suspended. The ground stub's first end is connected to a reference ground plane, while its last end is suspended. This unique asymmetric suspended-grounded structure allows the feed stub to excite its corresponding ground stub after being powered on, resulting in a mode with equal amplitude and a preset phase angle, thus achieving circularly polarized radiation. This helps improve the antenna's radiation performance and circular polarization characteristics. Furthermore, the tuning device in the middle of each stub can be individually adjusted to its resonant frequency, enabling the antenna to support multiple frequency bands. This design has significant practical value and broad application prospects.

[0055] It should be noted that the embodiments described in this application are merely some embodiments, not all embodiments. The components of the embodiments of this application typically described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the above detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0056] The terms "first, second, third, etc." or similar terms such as module A, module B, module C, etc., used in the specification and claims are only used to distinguish similar objects and do not represent a specific ordering of objects. It is understood that a specific order or sequence may be interchanged where permitted so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0057] In the above description, the labels indicating the steps do not necessarily mean that the steps will be executed. They may include intermediate steps or be replaced by other steps. Where permissible, the order of the steps may be interchanged or executed simultaneously.

[0058] The term "comprising" as used in the specification and claims should not be construed as limiting itself to what follows; it does not exclude other elements or steps. Therefore, it should be interpreted as specifying the presence of the mentioned feature, integral, step, or component, but does not exclude the presence or addition of one or more other features, integrals, steps, or components, or groups thereof. Thus, the statement "device comprising means A and B" should not be limited to a device consisting solely of components A and B.

[0059] The terms "an embodiment" or "an embodiment" as used in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in at least one embodiment of this application. Therefore, the terms "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment, but may refer to the same embodiment. Furthermore, in the various embodiments of this application, unless otherwise specified or in case of logical conflict, the terminology and / or descriptions between different embodiments are consistent and can be mutually referenced. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0060] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present application has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A multi-stub circularly polarized antenna, characterized in that, The device includes a PCB board and multiple branches disposed on the PCB board. A feed point is disposed at the center of the top layer of the PCB board. The feed point is connected to the RF port of the antenna through an impedance matching circuit. A reference ground plane is also disposed on the top layer of the PCB board. Each branch includes a straight trace located on the top layer of the PCB board and a diagonal trace located on the bottom layer of the PCB board. They are connected to form a continuous spiral broken line structure through vias at both ends of the traces. A tuning device is connected in series in the middle of the spiral broken line of each branch. The plurality of branches include at least one feed branch and at least two ground branches. The first end of the at least one feed branch is connected to the feed point, and the second end is suspended. The first ends of the at least two ground branches are connected to the reference ground plane, and the second ends are respectively suspended. When the feed branch is energized, an alternating electromagnetic field is generated around it, which excites the at least two ground branches to achieve circularly polarized radiation.

2. The multi-stub circularly polarized antenna according to claim 1, characterized in that, The impedance matching circuit is Type matching circuit, this The matching circuit includes a first inductor connected in series in the signal path, a first capacitor and a second inductor connected in parallel between the signal path and the reference ground.

3. The multi-stub circularly polarized antenna according to claim 1, characterized in that, The plurality of branches include three branches that are centrally symmetrically distributed, with an angle of 120 degrees between adjacent branches. The three branches include one power supply branch and two ground branches. By configuring the parameters of the tuning device connected in series with two ground stubs to have a preset difference, the feed stub and the two ground stubs together generate two resonant modes with a preset angle and a preset phase difference in the target frequency band, thereby making the antenna exhibit circularly polarized radiation characteristics in the target frequency band.

4. The multi-stub circularly polarized antenna according to claim 3, characterized in that, The two ground nodes are the first ground node and the second ground node, respectively, and the positive and negative relationship of the preset difference is used to control the rotation direction of the circular polarization radiation characteristics; specifically: When the tuning device parameter value of the first stub is greater than that of the tuning device parameter value of the second stub, the antenna exhibits circular polarization characteristics in the first direction in the corresponding target frequency band. When the tuning device parameter value of the first stub is less than that of the tuning device parameter value of the second stub, the antenna exhibits circular polarization characteristics in the corresponding target frequency band with a second rotation direction opposite to the first rotation direction.

5. The multi-stub circularly polarized antenna according to claim 1, characterized in that, The plurality of branches includes four branches arranged in a cross-shaped symmetrical distribution, of which two adjacent branches are power supply branches and the other two branches are ground branches; In this configuration, a feed stub and a ground stub located on the same axis constitute an antenna resonant unit. The two antenna resonant units are configured to operate in different target frequency bands. By adjusting the parameters of the tuning devices connected in series, the two antenna resonant units generate two resonant modes with a preset angle and a preset phase difference in the target frequency band, thereby realizing the dual-frequency dual-circular polarization radiation characteristics of the antenna.

6. The multi-stub circularly polarized antenna according to claim 1, characterized in that, The tuning device is an inductor, a capacitor, or a tuning circuit composed of an inductor and a capacitor; The tuning circuit is composed of a third inductor and a second capacitor connected in series, and then connected in parallel with a fourth inductor.

7. The multi-stub circularly polarized antenna according to claim 1, characterized in that, The tuning device is a switching tuning circuit, which consists of a fifth inductor and a switching device connected in series, and then connected in parallel with a sixth inductor. The switching device is controlled by a controller, and the equivalent inductance value of the ground stub is adjusted by switching the on and off state of the switching device, so that the antenna switches between multiple frequency bands.

8. The multi-stub circularly polarized antenna according to claim 7, characterized in that, The method of adjusting the equivalent inductance of the ground stub by switching the on / off state of the switching device specifically includes: When the switching device is turned on, the fifth inductor and the sixth inductor are connected in parallel to form the first equivalent inductance value; When the switching device is disconnected, only the sixth inductor is connected to the circuit to form the second equivalent inductance value; By switching the state of the switching device, the ground stub can be switched between two resonant frequencies.

9. A communication device, characterized in that, Includes a multi-stub circularly polarized antenna as described in any one of claims 1 to 8.

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