A switchable sense circular polarized antenna and communication device

Abstract

The application provides a switchable circular polarization antenna and a communication device. The switchable circular polarization antenna comprises a PCB board and three branches. A top layer of the PCB board is provided with a feed point and a reference ground plane. The three branches comprise a feed branch, a first ground branch and a second ground branch. The feed branch is connected to the feed point through a first end after being connected with a first tuning device in series, and a tail end of the feed branch is suspended. The top layer of the PCB board is further provided with a double-pole double-throw switch. The double-pole double-throw switch is controlled by a controller. A first fixed end of the double-pole double-throw switch is connected to the reference ground plane after being connected with a second tuning device in series. A second fixed end of the double-pole double-throw switch is connected to the reference ground plane after being connected with a third tuning device in series. A first end of the first ground branch is connected to a first moving end of the double-pole double-throw switch. A first end of the second ground branch is connected to a second moving end of the double-pole double-throw switch. Tail ends of the first ground branch and the second ground branch are suspended.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to a circularly polarized antenna with switchable rotation direction and a communication device. BACKGROUND

[0002] In the field of wireless communication, the antenna is a key component for transmitting and receiving spatial electromagnetic waves, and its performance directly affects the communication effect. According to the different polarization modes, the antenna can be divided into linear polarization, circular polarization and elliptical polarization. Circularly polarized antennas are widely used in satellite communication because they can effectively reduce the influence of reflected and other interference signals and improve communication quality. Figure 1 As shown in a commonly used traditional circularly polarized microstrip antenna, it is composed of a bottom plate and an upper square antenna plate, both of which are made of metal material. The feed point is located at a position slightly below the center of the antenna plate. Two corners of one diagonal line of the antenna plate are cut at an angle to realize the design of the circularly polarized microstrip antenna. The selection of the cut angle is determined by the requirement of the circular polarization direction of the radiated electromagnetic wave, which is left-handed or right-handed circular polarization. However, the structure of the traditional circularly polarized microstrip antenna is relatively simple, but it has the problems of large size and difficult debugging in the later stage. Especially if you want to change the circular polarization rotation direction of the antenna from left-handed to right-handed or vice versa, you need to redesign and manufacture it, which brings trouble to the operation and application. SUMMARY

[0003] Therefore, the present application provides a circularly polarized antenna with switchable rotation direction and a communication device. Through the design of three branch folded line traces, the antenna realizes the characteristics of multi-band and switchable rotation direction of circular polarization, and improves the flexibility of antenna debugging.

[0004] In the first aspect, the present application provides a circularly polarized antenna with switchable rotation direction, which includes a PCB board and three branches arranged on the PCB board. The center of the top layer of the PCB board is provided with a feed point, and the feed point is connected to the radio frequency port of the antenna through an impedance matching circuit. The top layer of the PCB board is also provided with a reference ground plane. Each branch includes a straight line trace on the top layer of the PCB board and an inclined line trace on the bottom layer of the PCB board, and is connected to a continuous spiral folded line structure through the vias at both ends of the trace.

[0005] The three branches include a feed branch and a first ground branch and a second ground branch distributed on both sides of the feed branch. The feed branch is connected to the feed point through its first end after being connected in series with a first tuning device, and its last end is suspended.

[0006] The top layer of the PCB board is further provided with a double-pole double-throw switch controlled by a controller, a first fixed end of the double-pole double-throw switch is connected to the reference ground plane in series with a second tuning device, a second fixed end of the double-pole double-throw switch is connected to the reference ground plane in series with a third tuning device, a first end of the first ground branch is connected to a first moving end of the double-pole double-throw switch, a first end of the second ground branch is connected to a second moving end of the double-pole double-throw switch, and the last ends of the first and second ground branches are left hanging.

[0007] When the feed branch is powered on, an alternating electromagnetic field is generated around it to excite the two ground branches, and the controller switches the conduction state of the two moving ends and the two fixed ends of the double-pole double-throw switch to achieve switchable circularly polarized radiation.

[0008] From the above, in the switchable circularly polarized antenna provided by the application, three branches composed of a feed branch and two ground branches are arranged on a double-sided PCB board, and each branch adopts a unique spiral broken line structure, wherein the first end of the feed branch is connected to a feed point and the last end is left hanging, and the first end of the ground branch is connected to the ground and the last end is left hanging. The unique asymmetric hanging-ground structure enables the feed branch to excite the ground branches when powered on, excite modes with equal amplitudes and a preset included angle, achieve circularly polarized radiation, and set a double-pole double-throw switch (DPDT) between the ground branches and the tuning devices. By switching the conduction state of the moving ends and the fixed ends of the double-pole double-throw switch, the series connection state of the ground branches and the tuning devices is switched, the circularly polarized rotation direction (left-handed or right-handed) of the antenna radiation field is dynamically and reversibly changed, the defects of the traditional circularly polarized antenna, such as fixed polarization direction and the need for redesign and production, are overcome, a hardware foundation is provided for the antenna equipment to adapt to different polarized electromagnetic wave environments, and the tuning devices in the middle of each branch can be individually adjusted to support multiple frequency bands.

[0009] Optionally, when the lengths of the two ground branches are the same and the parameters of the second tuning device and the third tuning device are configured to have a preset difference, the feed branch and the two ground branches together generate two resonant modes with a preset phase difference and a preset included angle at a target frequency band, so that the antenna exhibits circularly polarized radiation characteristics at the target frequency band.

[0010] From the above, by configuring the parameters of the tuning devices of the two ground branches to have a preset difference (such as L±Δ), two resonant modes with equal amplitudes and a phase difference at a certain angle are accurately excited at a target frequency band. This is the core physical mechanism for generating high-quality circularly polarized radiation, which ensures that the antenna has good axial ratio and circular polarization purity at the required frequency band, rather than simple elliptical polarization or linear polarization.

[0011] Optionally, the implementation of switchable circularly polarized radiation specifically includes:

[0012] When the controller outputs a first level, the double-pole double-throw switch makes the first movable terminal and the first fixed terminal conductive to make the first ground stub connect the second tuning device in series, and the second movable terminal and the second fixed terminal conductive to make the second ground stub connect the third tuning device in series, so that the antenna works in a first circular polarization direction;

[0013] When the controller outputs a second level, the double-pole double-throw switch makes the first movable terminal and the second fixed terminal conductive to make the first ground stub connect the third tuning device in series, and the second movable terminal and the first fixed terminal conductive to make the second ground stub connect the second tuning device in series, so that the antenna works in a second circular polarization direction opposite to the first circular polarization direction.

[0014] Therefore, by controlling the output of the controller to be high or low, the tuning devices connected by the two ground stubs can be reliably exchanged, the phase relationship of the two resonance modes is systematically reversed, and the left-handed circular polarization (LHCP) and the right-handed circular polarization (RHCP) are switched deterministically and repeatedly, which is simple and reliable.

[0015] Optionally, the impedance matching circuit is a Π type matching circuit, and the Π type matching circuit comprises a first inductor connected in series on a signal path, and a first capacitor and a second inductor connected in parallel between the signal path and a reference ground, respectively.

[0016] Therefore, by using the Π type matching circuit, an effective solution is provided for the antenna to achieve wideband and high-efficiency impedance matching with the radio frequency front end in a compact structure. The circuit can flexibly compensate for the inductive or capacitive components in the input impedance of the antenna, maximize the energy transmission efficiency, reduce the return loss, and ensure the radiation performance and use effect of the antenna in the target frequency band.

[0017] Optionally, the first tuning device, the second tuning device, and the third tuning device are tuning circuits, and the tuning circuit is composed of a third inductor and a second capacitor connected in series, and a fourth inductor connected in parallel. By adjusting the inductance values of the three tuning circuits, the antenna supports at least two operating frequency bands.

[0018] Therefore, by using the series-parallel structure of inductors and capacitors, a single tuning circuit can exhibit the required inductive or capacitive impedance at multiple different frequency points. This allows the antenna structure to support two or more discrete operating frequency bands in the same physical size, and to achieve circularly polarized radiation in each frequency band through the switching mechanism, thereby significantly improving the spectral utilization rate of the antenna and the versatility of the application scenarios.

[0019] Optionally, the first tuning device, the second tuning device and the third tuning device are switch tuning circuits, each of which comprises a fifth inductor and a switch device connected in series, and a sixth inductor connected in parallel with the fifth inductor, the switch device being controlled by the controller, and the equivalent inductance value of the ground branch being adjusted by switching the on-off state of the switch device, and the circular polarization rotation characteristic of the antenna at each of the multiple operating frequency bands being independently switchable by switching the conduction state of the two movable terminals and the two fixed terminals of the DPDT switch.

[0020] As described above, by replacing the fixed tuning device with a controlled switch tuning circuit, the equivalent inductance of each branch can be switched in real time by an electrical signal, thereby adjusting the resonant frequency of each branch, and by controlling the DPDT switch and the switch device in each tuning circuit by the controller, the antenna can not only operate at multiple preset frequency bands, but also dynamically switch between these frequency bands and independently control the polarization rotation at each frequency band. This achieves reconfigurability in two dimensions of frequency and polarization.

[0021] Optionally, the adjustment of the equivalent inductance value of the ground branch by switching the on-off state of the switch device specifically comprises:

[0022] When the switch device is on, the fifth inductor and the sixth inductor are connected in parallel to form a first equivalent inductance value;

[0023] When the switch device is off, only the sixth inductor is connected to the circuit to form a second equivalent inductance value;

[0024] By switching the state of the switch device, the switching of the ground branch between two resonant frequencies is realized.

[0025] As described above, by switching the parallel inductor combination or the single inductor connection under the control of the switch, two discrete and distinct equivalent inductance values are obtained. This circuit structure is simple and reliable, has fast switching speed, clear control logic and other advantages, and ensures the flexible adjustment of the equivalent inductance of each branch.

[0026] Optionally, the projections of the three branches on the PCB board are centrally symmetrically distributed, and the included angle between adjacent branches is 120 degrees.

[0027] As described above, by the strict geometric constraint of 120-degree central symmetry, the perfect balance of the three branches in space is ensured. This symmetry is crucial for generating circularly polarized waves with symmetric radiation patterns and excellent axial ratio performance, effectively suppressing undesired cross-polarization components, improving the radiation efficiency of the antenna, and ensuring the consistency of performance under different polarization switching states.

[0028] In a second aspect, the present application provides a communication device comprising the switchable rotation circularly polarized antenna described above.

[0029] These and other aspects of the present application will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein: BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A top view of a structure of a conventional circularly polarized microstrip antenna;

[0031] Figure 2 A top view of a structure of a switchable circularly polarized antenna provided in an embodiment of the present application;

[0032] Figure 3a A schematic diagram of straight-line traces on a top layer of a PCB in an embodiment of the present application;

[0033] Figure 3b A schematic diagram of diagonal traces on a bottom layer of a PCB in an embodiment of the present application;

[0034] Figure 4 A circuit diagram of a first switchable circularly polarized antenna provided in an embodiment of the present application;

[0035] Figure 5 A circuit diagram of a second switchable circularly polarized antenna provided in an embodiment of the present application;

[0036] Figure 6 A circuit diagram of a third switchable circularly polarized antenna provided in an embodiment of the present application;

[0037] Figures 7a-7c A schematic diagram of results of a simulation experiment provided in an embodiment of the present application;

[0038] Figures 8a-8c A schematic diagram of results of another simulation experiment provided in an embodiment of the present application.

[0039] It should be understood that in the above structural schematic diagrams, the sizes and shapes of the blocks are for reference only and should not be construed as exclusive interpretation of the embodiments of the present application. The relative positions and inclusion relationships between the blocks presented in the structural schematic diagrams are only used to schematically represent the structural association between the blocks, and do not limit the physical connection manner of the embodiments of the present application. DETAILED DESCRIPTION

[0040] The technical solutions provided by the present application will be further described below in conjunction with the drawings and embodiments. It should be understood that the system structures and service scenarios provided in the embodiments of the present application are mainly used to illustrate possible implementation manners of the technical solutions of the present application, and should not be interpreted as the only limitation of the technical solutions of the present application. Those skilled in the art can know that the technical solutions provided by the present application are also applicable to similar technical problems as the system structure evolves and new service scenarios appear.

[0041] 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. If there is a conflict between the definitions in the specification and those in the patent specification, the definitions in the specification are intended to prevail. In addition, the terms used herein are for the purpose of describing embodiments of the present application only and are not intended to limit the present application.

[0042] Hereinafter, the scheme provided by the present application will be described in detail in conjunction with the accompanying drawings and embodiments.

[0043] The embodiment of the present application provides a circularly polarized antenna with switchable rotation direction, specifically realizes an innovative antenna physical structure and a tuning method. The antenna utilizes double-sided printed circuit board (PCB) technology, designs three spiral folded branches in central symmetry, connects tunable passive devices or switchable circuit networks in each branch in series, and innovatively integrates double-pole double-throw switch (DPDT) in the connection path of two ground branches and tuning devices. By controlling the switch state to exchange the tuning devices connected by the two ground branches, the phase distribution of the radiation field of the antenna is systematically changed, and the quick and reliable switching between left-handed circular polarization and right-handed circular polarization is realized. The scheme effectively solves the problems of large size, difficult debugging and single function of the traditional circularly polarized antenna.

[0044] As shown in Figures 2-3b The circularly polarized antenna with switchable rotation direction provided by the embodiment of the present application is constructed based on a dielectric substrate (i.e. a PCB board). The top layer of the PCB board is respectively provided with a feed point and a reference ground plane. The feed point is located on the top layer of the PCB board, and the reference ground plane is located near the feed point. Three groups of radial linear traces are etched on the top layer of the PCB board (as shown in Figure 3a Three groups of inclined traces corresponding to the top layer traces are etched on the bottom layer of the PCB board (as shown in Figure 3b Each group of top layer traces and corresponding bottom layer traces are electrically connected by metal vias at both ends, and together form a continuous spiral folded line structure with spatial spiral sense. Each spiral folded line structure is a branch.

[0045] Among the three branches, the uppermost branch is a left-handed circularly polarized antenna, the lowermost branch is a right-handed circularly polarized antenna, and the middle branch is a left-handed circularly polarized antenna. Figure 2Taking the indicated orientation as an example, one stub is defined as a feed stub, and the other two stubs are evenly distributed around it, defined as ground stub 1 and ground stub 2 respectively. The feed stub is connected in series with the tuning device L01 and then connected to the feed point located at the center of the top layer of the PCB board through its first end (i.e., the starting point of the spiral broken line structure, near the center of the PCB board). This feed point is connected to the RF port of the antenna 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 first ends of ground stub 1 and ground stub 2 are respectively connected to the two moving ends of a double-pole double-throw switch (DPDT), and the ends are left floating. The control end of the DPDT is connected to a controller and controlled by the controller. The two fixed ends of the DPDT are connected in series with the tuning devices L02 and L03 respectively and then connected to the reference ground plane of the top layer of the PCB board.

[0046] 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 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, and its resonant frequency is determined by the physical length (electrical length) of the feed stub and the ground stub themselves, as well as the value of the tuning device connected in series. The controller switches the conduction states of the two moving terminals and two fixed terminals of the double-pole double-throw switch. For example, when the controller outputs a first level, the double-pole double-throw switch connects the first moving terminal to the first fixed terminal, so that the ground stub 1 is connected in series with the tuning device L02, and the second moving terminal connects to the second fixed terminal, so that the ground stub 2 is connected in series with the tuning device L03, and the antenna operates in the first circular polarization direction. When the controller outputs a second level, the double-pole double-throw switch connects the first moving terminal to the second fixed terminal, so that the ground stub 1 is connected in series with the tuning device L03, and the second moving terminal connects to the first fixed terminal, so that the ground stub 2 is connected in series with the tuning device L02, and the antenna operates in the second circular polarization direction opposite to the first circular polarization direction, thereby realizing the switchable circular polarization radiation of the antenna.

[0047] 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.

[0048] 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. L02 and L03 are connected to pins 1 and 2 of a double-pole double-throw switch (DPDT), respectively. Pins 3 and 4 of the DPDT are connected to ground stubs 1 and 2, respectively. The control signal of the CPU is connected to the control port CTL of the DPDT to control its switching state. When the CPU's control signal outputs a low level, pins 1 and 3 of the DPDT are turned on, tuning device L02 is connected to ground stub 1, pins 2 and 4 of the DPDT are turned on, and tuning device L03 is connected to ground stub 2. When the CPU's control signal outputs a high level, pins 1 and 4 of the DPDT are turned on, tuning device L02 is connected to ground stub 2, pins 2 and 3 of the DPDT are turned on, and tuning device L03 is connected to ground stub 1. Port 1 is connected to the feed point through an antenna impedance matching circuit. In actual use, firstly... Based on the target antenna's operating frequency and size requirements, the length and spacing of the broken lines are designed. The spacing of the broken lines mainly affects the overall length of the antenna's broken line traces. The lower the target antenna's operating frequency, the longer the broken line traces need to be. Therefore, the smaller the spacing, the more bends the traces can make, and the longer the traces, the closer the resonant frequency of the antenna traces is to the target frequency. With the addition of intermediate series tuning devices, the broken line can be adjusted to the target operating frequency. However, the smaller the spacing, the longer and denser the traces, the worse the antenna radiation effect. The tuning device supplement value can be smaller, and the device loss performance is lower. Conversely, the larger the broken line spacing, the shorter the traces, and the better the broken line radiation performance. However, a larger tuning device is 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 broken line length is determined by the antenna board size. Try to fill the board as much as possible to make the trace area larger, and the antenna radiation effect will be better.

[0049] The following is based on Figure 2 Antenna structure and Figure 4 The circuit structure is used to illustrate how to achieve switchable circular polarization in a specific target frequency band:

[0050] First disconnect the ground branch 2, and through the CPU control port output low level control DPDT switch foot 1 and foot 3 conduction, tuning device L02 connected ground branch 1, DPDT switch foot 2 and foot 4 conduction, tuning device L03 connected ground branch 2, but because the ground branch 2 is disconnected, so this path does not work, according to the target antenna operating frequency to determine the tuning device L01 value of the positive above feed branch and the tuning device L02 value of the ground branch 1 connected to make the device (usually inductance) value close to the device value LN, and the antenna operating frequency at the target operating frequency f0, then according to the inductance value LN, the middle tuning device L03 connected to the ground branch 2 is determined to be slightly larger than the inductance LN value of the inductance device value LN+∆ (∆ is a small positive deviation value), the tuning device L02 value connected to the ground branch 1 is changed to be slightly smaller than the inductance LN value of the inductance device value LN-∆, through this design, the positive above feed branch and the two ground branches, respectively, form two antenna resonance modes with similar operating frequencies, the antenna resonance mode formed by the feed branch and the ground branch 2 has an operating frequency of f0-k (k value greater than zero and very small) slightly lower than the target operating frequency f0, and the phase lags at f0 frequency, the antenna resonance mode formed by the feed branch and the ground branch 1 has an operating frequency of f0+k (k value greater than zero and very small) slightly higher than the target operating frequency f0, and the phase leads at f0 frequency, and the two resonance modes are rotated by 120 degrees, so as to realize the left-handed circularly polarized antenna design in the f0 frequency band.

[0051] Conversely, when the control port of the CPU outputs high level, the foot 1 and the foot 4 of the DPDT are conduction, the tuning device L02 is connected to the ground branch 2, the foot 2 and the foot 3 of the DPDT are conduction, the tuning device L03 is connected to the ground branch 1, that is, the tuning devices L02 and L03 connected to the ground branch 2 and the ground branch 3 are reversed, and the antenna is switched to the right-handed circularly polarized antenna, so as to realize the circularly polarized antenna design of the three branches of the application which can be switched to left-handed or right-handed circular polarization according to the demand of the antenna rotation direction, by controlling the CPU to output high level or low level control signal, thereby controlling the DPDT to switch different connection states.

[0052] In some embodiments, if the antenna needs to work in two frequency bands, and both of the dual-band antennas are circularly polarized, only the tuning device in the middle of the three groups of broken lines needs to be adjusted as Figure 5The circuit design scheme, taking the feed branch as an example, the fixed inductance L01 is replaced by a tuning network composed of inductance L11 and capacitance C11 in series, and inductance L12 in parallel. The equivalent impedance characteristic calculation formula of this circuit is Im1=(ω2*L11*C11-1)L12C11 / (L11C11+L12C11-1), wherein ω=2*π*f (f is the target working frequency of the antenna), through this circuit design, the equivalent impedance of the circuit can have larger inductance value characteristics at lower frequency and smaller inductance value characteristics at higher frequency, so that the tuning network is replaced by all tuning devices (L01, L02, L03) in Figure 4 , that is, each ground branch and the feed branch and the tuning device network together form two working frequency antenna resonance modes. When the control port of the CPU outputs a low level, the feet 1 and 3 of the DPDT are conductive, and the feet 2 and 4 are conductive, that is, the two resonance mode working frequencies of the feed branch and the ground branch 1 are f11+k1 and f21+k2 (k1 and k2 are greater than zero and very small), and the two resonance mode working frequencies of the feed branch and the ground branch 2 are f11-k1 and f21-k2 (k1 and k2 are greater than zero and very small), so that the antenna working frequency in the dual-frequency band of f11 and f21 is a left-handed circularly polarized antenna scheme design.

[0053] Conversely, when the control port of the CPU outputs a high level, the feet 1 and 4 of the DPDT are conductive, the ground branch 1 is connected to the tuning network 3, the feet 2 and 3 of the DPDT are conductive, and the ground branch 2 is connected to the tuning network 2, that is, the tuning networks connected by the ground branch 2 and the ground branch 3 are reversed, and the antenna is switched to a right-handed circularly polarized antenna. By controlling the control signal output by the CPU, the different communication states of the DPDT are switched, and the application three-branch switchable left-handed or right-handed dual-band circularly polarized antenna scheme design is realized.

[0054] The above-mentioned dual-frequency circularly polarized antenna switching mode can also realize the antenna working mode of one frequency working in left-handed circular polarization and the other frequency working in right-handed circular polarization, that is, different rotation directions, by adjusting the values of the tuning devices. The DPDT switch switching connection is reversed again to realize the right-handed and left-handed rotation characteristics.

[0055] To further improve the flexibility and intelligent level of the antenna, the application embodiment also proposes a scheme of replacing the fixed tuning device with a switch-type tuning circuit, as shown in Figure 6As shown, for example, the fixed inductor L02 is replaced by a switchable tuning network, which includes an inductor L32 connected in series with pin 1 of the DPDT switch, and a branch connected in parallel with the inductor L32, the branch being formed by an inductor L31 and a single-pole single-throw (SPST) switch S2 connected in series, the switch S2 being controlled by a GPIO pin of the controller (e.g. the CPU 1). Based on the structure of the switchable tuning network, when the CPU 1 outputs a control signal to make the switch S2 open, the inductor L31 branch is not connected, and only the inductor L32 is connected in the switchable tuning network. Assuming that the equivalent inductance at this time is Leq off = L32, corresponding to a resonant frequency F off; when the CPU 1 outputs a control signal to make the switch S2 conduct, the inductor L31 and the inductor L32 form a parallel relationship. The total equivalent value of the parallel inductance is Leq on = (L31*L32) / (L31+L32), which is smaller than L32. Therefore, the equivalent inductance in the switchable tuning network becomes smaller, corresponding to another higher resonant frequency F on.

[0056] Through the design of the switchable tuning network, a single stub can be electrically switched between two preset frequencies. By applying such a switch circuit to all three stubs and independently controlling all switches in binary, the antenna can theoretically be switched between a plurality of different frequency combination states.

[0057] In some embodiments, the three-stub switchable left-handed or right-handed dual-band dual-circularly polarized antenna design of the present application can be achieved by controlling the on-off of each SPST switch and DPDT switch. For example, when the control port of the CPU outputs a low level, pins 1 and 3 of the DPDT switch are conductive, and pins 2 and 4 are conductive, i.e. the switchable tuning network 2 formed by the feed stub and the ground stub 1 is connected, and the two resonant mode operating frequencies are f11+k1 and f21+k2 (k1 and k2 are both greater than zero and very small), the switchable tuning network 3 formed by the feed stub and the ground stub 2 is connected, and the two resonant mode operating frequencies are f11-k1 and f21-k2 (k1 and k2 are both greater than zero and very small), so as to realize the antenna operating frequency in the two dual-band frequency bands f11 and f21 as a left-handed circularly polarized antenna design.

[0058] Conversely, when the control port of the CPU outputs a high level, pins 1 and 4 of the DPDT switch are conductive, the ground stub 2 is connected to the switchable tuning network 2, pins 2 and 3 of the DPDT switch are conductive, and the ground stub 1 is connected to the switchable tuning network 3, i.e. the switchable tuning networks connected by the ground stub 2 and the ground stub 3 are reversed, the antenna is switched to a right-handed circularly polarized antenna, and by controlling the CPU to output a high level or a low level control signal, different connection states of the DPDT switch are controlled, and the three-stub switchable left-handed or right-handed dual-band circularly polarized antenna design of the present application is realized.

[0059] The above dual-frequency circularly polarized antenna switching mode can also be realized by adjusting the tuning device value to work at one frequency in left-handed circular polarization and the other frequency in right-handed circular polarization, i.e., different antenna working modes of the same antenna, and the DPDT switch is switched to reverse the right-handed and left-handed rotation characteristics.

[0060] To verify the feasibility and effect of the present application, a three-branch antenna model as shown in Figure 2 Fig. 4 can also be established by using three-dimensional electromagnetic simulation software. Taking the antenna target working frequency of 400 MHz as an example, the simulation verifies the feasibility of the antenna, and the PCB board diameter is set to 75 mm, which is much smaller than the length size of the conventional half-wave dipole antenna in the 400 MHz frequency band.

[0061] First, when the CPU control signal port outputs a low level to the DPDT switch, the tuning device L01 of the feed branch is connected with an inductance value of 50 nH, the ground branch 1 is connected with the tuning device L02 with an inductance value of 50 nH, the ground branch 2 is connected with the tuning device L03 with an inductance value of 56 nH, and through the matching circuit L1 position in series with an inductance of 8 nH and C1 position in parallel with a capacitance of 12 pF, the simulation obtains the antenna evaluation results as shown in Figures 7a-7c Fig. 5, wherein the antenna reflection coefficient S11 reflects the antenna working frequency at the target frequency of 400 MHz, and the maximum gain (Max Gain) curve in the antenna gain graph and the left-handed (LHCP) and right-handed (RHCP) polarization component gain curve results show that the left-handed polarization component and the maximum gain result are similar at 400 MHz, indicating that the present application can realize the left-handed circularly polarized antenna design of the antenna working at 400 MHz, and the antenna axial ratio (AR) graph shows that the antenna axial ratio is 1.9 at 400 MHz, indicating that the antenna axial ratio performance designed by the present application scheme is very good.

[0062] Then, when the CPU control signal port outputs a high level to the DPDT switch, the tuning device L01 of the feed branch is unchanged with an inductance value of 50 nH, the ground branch 1 is switched to the tuning device L03 (with an inductance value of 56 nH) through the DPDT, the ground branch 2 is switched to the tuning device L02 (with an inductance value of 50 nH) through the DPDT, and the matching circuit is unchanged. Through simulation, the antenna evaluation results are as shown in Figures 8a-8cAs shown in the figure, the antenna reflection coefficient S11 reflects the antenna operating frequency at the target frequency of 400MHz, the maximum gain (Max Gain) curve in the antenna gain figure and the left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) component gain curve results show that the right-handed circular polarization component is similar to the maximum gain result at 400MHz, which indicates that the application can realize the antenna operating at 400MHz by switching the antenna handedness to the right-handed circularly polarized antenna design through the DPDT switch, and the antenna axial ratio (AR) figure shows that the antenna axial ratio is 1.8 at 400MHz, indicating that the axial ratio performance of the antenna designed by the application scheme is very good.

[0063] In summary, the circularly polarized antenna with switchable handedness provided by the embodiments of the application realizes one-key electrically controlled switching of circular polarization handedness on a compact PCB three-dimensional structure by ingeniously combining a DPDT switch with a tuning device (or network). By replacing different types of tuning networks, it can be easily extended to multi-band operation and "band-polarization" dual construction and other advanced functions. The scheme is flexible to debug, easy to integrate, and cost controllable, and is very suitable for application in modern wireless systems such as satellite communication, Internet of Things, mobile terminals and the like that require adaptive polarization matching.

[0064] It should be noted that the embodiments described in the present application are only part of the embodiments of the present application, not all embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations. Therefore, the above detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0065] The words "first, second, third, etc." or modules A, B, C, and the like in the specification and claims are only used to distinguish similar objects, and do not represent a specific order of the objects. It can be understood that the specific order or sequence can be interchanged as allowed, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0066] In the above description, the labels indicating the steps involved do not necessarily mean that the steps will be performed in this order, and can include intermediate steps or be replaced by other steps, and the order of the preceding and subsequent steps can be interchanged as allowed, or performed simultaneously.

[0067] The term "comprising" as used in the specification and in claims includes everything within its meaning. It should be interpreted as specifying the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, the term "comprising" as used in the specification and in claims should not be interpreted as a limitation on what can be claimed but rather as an indication that the disclosure contemplates several embodiments.

[0068] The term "one embodiment" or "an embodiment" as used in the specification means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, but can refer to different embodiments. Furthermore, the terms "comprising", "including", containing" or "having" and variations thereof as used in this application are intended to be equivalent to the term "consisting of" or "consisting essentially of", unless otherwise indicated. Therefore, unless the context clearly indicates otherwise, the use of these terms in the specification and claims is not intended to limit or narrow the scope of the application, but to expand the scope of the application to encompass additional methods, apparatus and compositions.

[0069] It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the application. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. It is appreciated that features of the application that are, individually, known in the art can be ascribed to this application when, in connection with the application, new features have emerged.

Claims

1. A switchable rotation direction circularly polarized antenna, characterized in that, The device includes a PCB board and three 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, which are connected to form a continuous spiral zigzag structure through vias at both ends of the traces. The three branches include a power supply branch and a first ground branch and a second ground branch distributed on both sides of the power supply branch. The power supply branch is connected in series with the first tuning device and then connected to the power supply point through its head end, and its end is suspended. The top layer of the PCB board is also provided with a double-pole double-throw switch. The double-pole double-throw switch is controlled by a controller. The first fixed terminal of the double-pole double-throw switch is connected in series with a second tuning device and then connected to the reference ground plane. The second fixed terminal of the double-pole double-throw switch is connected in series with a third tuning device and then connected to the reference ground plane. The first end of the first ground branch is connected to the first moving terminal of the double-pole double-throw switch. The first end of the second ground branch is connected to the second moving terminal of the double-pole double-throw switch. The ends of the first ground branch and the second ground branch are suspended. After the power supply stub is energized, an alternating electromagnetic field is generated around it to excite the two ground stubs respectively. The controller switches the conduction state of the two moving ends and the two fixed ends of the double-pole double-throw switch to achieve switchable rotation direction circular polarization radiation.

2. The switchable rotation direction circularly polarized antenna according to claim 1, characterized in that, When the trace lengths of the two ground stubs are the same and the parameters of the second and third tuning devices are configured 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.

3. The switchable rotation direction circularly polarized antenna according to claim 1 or 2, characterized in that, The implementation of switchable rotation direction circular polarization radiation specifically includes: When the controller outputs the first level, the double-pole double-throw switch connects the first moving end to the first fixed end, so that the first ground stub is connected in series with the second tuning device, and the second moving end is connected to the second fixed end, so that the second ground stub is connected in series with the third tuning device, and the antenna operates in the first circular polarization rotation direction; When the controller outputs the second level, the double-pole double-throw switch connects the first moving end to the second fixed end, so that the first ground stub is connected in series with the third tuning device, and the second moving end is connected to the first fixed end, so that the second ground stub is connected in series with the second tuning device, and the antenna operates in the second circular polarization direction opposite to the first circular polarization direction.

4. The switchable rotation direction circularly polarized antenna according to claim 1, characterized in that, 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 and a second inductor connected in parallel between the signal path and the reference ground.

5. The switchable rotation direction circularly polarized antenna according to claim 1, characterized in that, The first, second, and third tuning devices are tuning circuits. Each tuning circuit is composed of a third inductor and a second capacitor connected in series, and then connected in parallel with a fourth inductor. By adjusting the inductance values ​​of the three tuning circuits, the antenna can support at least two operating frequency bands.

6. The switchable rotation direction circularly polarized antenna according to claim 1, characterized in that, The first, second, and third tuning devices are switching tuning circuits. Each switching tuning circuit 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 the controller. By switching the on / off state of the switching device, the equivalent inductance value of the ground stub is adjusted. By switching the conduction state of the two moving terminals and the two fixed terminals of the double-pole double-throw switch, the antenna has independently switchable circular polarization rotation characteristics in multiple operating frequency bands.

7. The switchable rotation direction circularly polarized antenna according to claim 6, 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.

8. The switchable rotation direction circularly polarized antenna according to claim 1, characterized in that, The projections of the three branches on the PCB are centrally symmetrical, and the included angle between adjacent branches is 120 degrees.

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

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