Antenna polarization mode switching circuit, switching method, storage medium and program product

Abstract

The application relates to the technical field of communication, and provides an antenna polarization mode switching circuit, a switching method, a storage medium and a program product. The antenna polarization mode switching circuit comprises a control unit, a radio frequency system and a polarization switching module. One end of a first double-pole double-throw switch in the polarization switching module is connected with a single-pole triple-throw switch, and the other end is connected to a bridge. The other end of the bridge is connected to a second double-pole double-throw switch. The other end of the second double-pole double-throw switch is respectively connected to two feed points of a dual-polarized antenna. The radio frequency system is connected to the first double-pole double-throw switch or any one of the two feed points of the dual-polarized antenna through the single-pole triple-throw switch, and is used for receiving an antenna signal or transmitting a radio frequency signal. The control unit is used for outputting a control signal to the switches in the polarization switching module, so as to realize polarization mode switching of the dual-polarized antenna by switching the connection state of the switches. The antenna polarization mode switching circuit can guarantee the communication effect between two wireless communication devices.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to an antenna polarization switching circuit, switching method, storage medium, and program product. Background Technology

[0002] In wireless communication equipment, the antenna is a crucial component. Antennas can be categorized into linearly polarized and circularly polarized antennas based on their polarization. Linearly polarized antennas are further classified into vertically polarized and horizontally polarized antennas based on the direction of their electric field vector, while circularly polarized antennas are classified into left-handed and right-handed circularly polarized antennas based on the direction of their electric field vector rotation. Two wireless communication devices communicate by transmitting and receiving signals through their antennas. Theoretically, when two terminal devices using vertically or horizontally polarized antennas communicate, the polarization loss attenuation of the electromagnetic wave signal is so significant that communication is almost impossible. Similarly, theoretically, when two terminal devices using left-handed or right-handed circularly polarized antennas communicate, the polarization loss attenuation is also so significant that communication is almost impossible. When two wireless communication devices using linearly or circularly polarized antennas communicate, the polarization loss causes a signal attenuation of 3 dB. Even with linearly polarized antennas, inconsistent polarization angles will also lead to signal attenuation. Electromagnetic signal polarization loss attenuation is minimized only when the antenna polarization methods and polarization angles of two wireless communication devices are identical. Therefore, the antenna polarization method is crucial when two wireless devices communicate, significantly impacting signal communication performance.

[0003] Currently, antenna polarization is fixed. For example, when a vertically polarized antenna is used in a wireless communication device, the optimal communication method for the paired wireless communication device is for its antenna to also be vertically polarized. However, if the wireless communication device rotates, the direction of its antenna's electric field vector will change, causing a change in polarization. For instance, if the wireless communication device rotates its antenna by 90 degrees, the vertically polarized antenna becomes a horizontally polarized antenna, severely affecting communication performance. For example, when using a portable device or communicating with an unknown device, it's impossible to guarantee that the antenna polarizations of the two wireless communication devices will match, affecting signal quality or causing unstable communication in practical use.

[0004] When two circularly polarized antennas communicate, for two circularly polarized antennas with matched rotation, such as both being left-hand circularly polarized antennas, when the signal from one device is reflected by a wall, the polarization rotation will change, becoming a right-hand circularly polarized antenna. Therefore, the reflected signal cannot be received by the other wireless communication device, sacrificing communication signal energy.

[0005] As a result, when two wireless communication devices communicate based on conventional antenna designs, the mismatch in antenna polarization can easily affect the quality of the communication signal, leading to poor communication performance. Summary of the Invention

[0006] This application aims to at least solve one of the technical problems existing in the related art. To this end, this application proposes an antenna polarization switching circuit, switching method, storage medium, and program product to solve the problem that the communication signal quality is affected by the mismatch of antenna polarization when two wireless communication devices are communicating, thereby ensuring the communication effect between the two wireless communication devices.

[0007] An antenna polarization switching circuit according to a first aspect of this application includes a control unit, a radio frequency system, and a polarization switching module.

[0008] The polarization switching module includes a first double-pole double-throw switch, a bridge, a second double-pole double-throw switch, and a single-pole triple-throw switch; wherein, one end of the first double-pole double-throw switch is connected to the single-pole triple-throw switch, and the other end is connected to the bridge; the other end of the bridge is connected to the second double-pole double-throw switch; the other end of the second double-pole double-throw switch is respectively connected to the two feed points of the dual-polarized antenna;

[0009] The radio frequency system is connected to either the first double-pole double-throw switch or any of the two feed points of the dual-polarized antenna via the single-pole triple-throw switch, for receiving antenna signals or transmitting radio frequency signals;

[0010] The control unit is used to output a control signal to the switch in the polarization switching module so as to switch the polarization mode of the dual-polarized antenna by switching the connection state of the switch.

[0011] According to one embodiment of this application, the polarization switching module further includes a first single-pole double-throw switch and a second single-pole double-throw switch;

[0012] The other end of the second double-pole double-throw switch is connected to the two feed points of the dual-polarized antenna through the first single-pole double-throw switch and the second single-pole double-throw switch, respectively.

[0013] The radio frequency system is connected to the corresponding feed point of the two feed points of the dual-polarized antenna via the single-pole triple-throw switch, the first single-pole double-throw switch, or the second single-pole double-throw switch.

[0014] According to one embodiment of this application, the two pins of the bridge are respectively connected to two different pins of the second double-pole double-throw switch via transmission lines of different lengths.

[0015] According to one embodiment of this application, the two different pins of the second double-pole double-throw switch are respectively connected to the first single-pole double-throw switch and the second single-pole double-throw switch via transmission lines of different lengths.

[0016] According to one embodiment of this application, the bridge is a 90-degree bridge.

[0017] According to one embodiment of this application, a resistor is also connected to one end of the first double-pole double-throw switch that is connected to the single-pole triple-throw switch.

[0018] According to a second aspect of this application, an antenna polarization switching method applied to any of the antenna polarization switching circuits described above includes:

[0019] The radio frequency system in the control antenna polarization switching circuit is connected to the first feed point of the two feed points of the dual-polarized antenna, and the strength and phase of the first received signal of the radio frequency system based on the antenna signal feedback are determined.

[0020] The radio frequency system in the control antenna polarization switching circuit is connected to the second feed point of the two feed points of the dual-polarized antenna, and the strength and phase of the second received signal of the radio frequency system based on the antenna signal feedback are determined;

[0021] The radio frequency system in the control antenna polarization switching circuit is connected to the first feed point of the two feed points of the dual-polarized antenna, and the third signal phase of the radio frequency system is determined based on the antenna signal feedback;

[0022] Based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase, and the third signal phase, the polarization mode of the antenna corresponding to the incoming signal is determined;

[0023] Based on the polarization mode of the antenna corresponding to the incoming wave signal, the antenna polarization mode switching circuit is controlled to switch the antenna polarization mode.

[0024] According to one embodiment of this application, determining the polarization mode of the antenna corresponding to the incoming signal based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase, and the third signal phase includes:

[0025] Based on the first signal phase, the second signal phase, and the third signal phase, the signal phase difference between the first feed point and the second feed point is determined;

[0026] Based on the first received signal strength, the first signal phase, the second received signal strength and the second signal phase, the amplitude of the left-hand circular polarization component electric field, the amplitude of the right-hand circular polarization component electric field and the axial ratio of the incoming wave signal are determined;

[0027] Based on the signal phase difference, the electric field amplitude of the left-hand circular polarization component of the incoming signal, the electric field amplitude of the right-hand circular polarization component, and the axial ratio, the polarization mode of the antenna corresponding to the incoming signal is determined.

[0028] According to a third aspect of the present application, the storage medium is a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the antenna polarization switching method as described above.

[0029] A computer program product according to a fourth aspect of this application includes a computer program that, when executed by a processor, implements the antenna polarization switching method as described above.

[0030] The above-described one or more technical solutions in the embodiments of this application have at least the following technical effects:

[0031] This invention provides an antenna polarization switching circuit comprising a control unit, a radio frequency system, and a polarization switching module. The polarization switching module includes a first double-pole double-throw switch, a bridge circuit, a second double-pole double-throw switch, and a single-pole triple-throw switch. One end of the first double-pole double-throw switch is connected to the single-pole triple-throw switch, and the other end is connected to the bridge circuit. The other end of the bridge circuit is connected to the second double-pole double-throw switch. The other end of the second double-pole double-throw switch is connected to two feed points of the dual-polarized antenna. The radio frequency system is connected to either the first double-pole double-throw switch or one of the two feed points of the dual-polarized antenna via the single-pole triple-throw switch, for receiving antenna signals or transmitting radio frequency signals. The control unit outputs control signals to the switches in the polarization switching module. Therefore, the polarization mode of the dual-polarized antenna can be switched by switching the connection state of the switch through the control signal sent by the control unit. In this application, the dual-polarized antenna can be switched between six polarization modes, namely left-hand circular polarization, right-hand circular polarization, vertical polarization, horizontal polarization, positive 45-degree linear polarization, and negative 45-degree linear polarization, in order to match the polarization mode of the antenna of another wireless communication device. Thus, the radio frequency system can receive or transmit signals through the antenna with the matching polarization mode, avoiding affecting the communication signal quality between the two wireless communication devices and ensuring the communication effect.

[0032] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the antenna polarization switching circuit provided in the embodiments of this application.

[0035] Figure 2 This is a top view of a schematic diagram showing the antenna feed point setting in the antenna polarization switching circuit provided in this application embodiment.

[0036] Figure 3 This is a side view of a schematic diagram showing the antenna feed point setting in the antenna polarization switching circuit provided in this application embodiment.

[0037] Figure 4 This is one of the link diagrams in the antenna polarization switching circuit provided in the embodiments of this application.

[0038] Figure 5 This is the second link diagram in the antenna polarization switching circuit provided in the embodiments of this application.

[0039] Figure 6 This is the third link diagram in the antenna polarization switching circuit provided in the embodiments of this application.

[0040] Figure 7 This is the fourth link diagram in the antenna polarization switching circuit provided in the embodiments of this application.

[0041] Figure 8 This is a flowchart illustrating the antenna polarization switching method provided in the embodiments of this application.

[0042] Figure 9 This is a schematic diagram showing the comparison of right-hand circular polarization gain in the simulation results of the antenna polarization switching circuit provided in the embodiments of this application.

[0043] Figure 10 This is a schematic diagram of the right-hand circular polarization axis ratio from the simulation results of the antenna polarization switching circuit provided in the embodiments of this application.

[0044] Figure 11 This is a schematic diagram showing the vertical line polarization gain comparison of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application.

[0045] Figure 12 This is a schematic diagram of the vertical polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application.

[0046] Figure 13 This is a schematic diagram comparing the left-hand circular polarization gain of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application.

[0047] Figure 14 This is a schematic diagram of the left-hand circular polarization axis ratio from the simulation results of the antenna polarization switching circuit provided in the embodiments of this application.

[0048] Figure 15 This is a schematic diagram showing the horizontal polarization gain comparison of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application.

[0049] Figure 16 This is a schematic diagram of the horizontal polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application.

[0050] Figure 17 This is a schematic diagram showing the comparison of linear polarization gain at a positive 45-degree angle in the simulation results of the antenna polarization switching circuit provided in the embodiments of this application.

[0051] Figure 18 This is a schematic diagram of the positive 45-degree linear polarization axis ratio in the simulation results of the antenna polarization switching circuit provided in the embodiments of this application.

[0052] Figure 19 This is a schematic diagram showing the comparison of negative 45-degree linear polarization gain in the simulation results of the antenna polarization switching circuit provided in the embodiments of this application.

[0053] Figure 20 This is a schematic diagram of the negative 45-degree linear polarization axis ratio in the simulation results of the antenna polarization switching circuit provided in the embodiments of this application. Detailed Implementation

[0054] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but should not be used to limit the scope of this application.

[0055] In the description of the embodiments of this application, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0056] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0057] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0059] This application discloses an antenna polarization switching circuit, switching method, storage medium, and program product.

[0060] Figure 1 This is a schematic diagram of the antenna polarization switching circuit provided in the embodiments of this application, as shown below. Figure 1 As shown, the antenna polarization switching circuit of this application may include a control unit, a radio frequency system, and a polarization switching module.

[0061] The polarization switching module includes a first double-pole double-throw switch, a bridge, a second double-pole double-throw switch, and a single-pole triple-throw switch. One end of the first double-pole double-throw switch is connected to the single-pole triple-throw switch, and the other end is connected to the bridge. The other end of the bridge is connected to the second double-pole double-throw switch. The other end of the second double-pole double-throw switch is connected to the two feed points of the dual-polarized antenna.

[0062] The radio frequency system is connected to either the first double-pole double-throw switch or either the two feed points of the dual-polarized antenna via a single-pole triple-throw switch, for receiving antenna signals or transmitting radio frequency signals;

[0063] The control unit outputs control signals to the switches in the polarization switching module to switch the polarization mode of the dual-polarized antenna by changing the connection state of the switches. Specifically, the control unit can be a central processing unit (CPU) control unit.

[0064] It should be further noted that the polarization switching module also includes a first single-pole double-throw switch and a second single-pole double-throw switch.

[0065] The other end of the second double-pole double-throw switch is connected to the two feed points of the dual-polarized antenna through the first single-pole double-throw switch and the second single-pole double-throw switch, respectively.

[0066] Furthermore, the radio frequency system is connected to the corresponding feed point of the two feed points of the dual-polarized antenna via a single-pole triple-throw switch, through a first single-pole double-throw switch or a second single-pole double-throw switch.

[0067] Furthermore, the two pins of the bridge are connected to two different pins of the second double-pole double-throw switch via transmission lines of different lengths. In this application, the bridge can be a 90-degree bridge.

[0068] Furthermore, the two different pins of the second double-pole double-throw switch are connected to the first single-pole double-throw switch and the second single-pole double-throw switch respectively via transmission lines of different lengths.

[0069] Furthermore, a resistor is also connected to the end of the first double-pole double-throw switch that is connected to the single-pole triple-throw switch.

[0070] Specifically, in the antenna polarization switching circuit of this application, the RF system is connected to one of the antenna feed points of Port1 via pin 2 of a single-pole triple-throw switch S3. Port1 is connected to pin 1 of a double-pole double-throw switch 1 (which can be defined as the first double-pole double-throw switch in this application, hereinafter referred to as DPDT1). Pin 2 of DPDT1 is connected to a 50-ohm resistor to ground for bridge port matching at the back end. Pin 3 of DPDT1 is connected to pin 1 of a 90-degree bridge 1 (hereinafter referred to as bridge 1) operating in the target frequency band (wherein the target frequency band can be set according to actual usage requirements) via a transmission line. Pin 4 of DPDT1 is connected to the 90-degree bridge 1 via a transmission line of the same length as that connected to pin 3. Pin 4, the control signal pin 1 of the CPU control unit, is connected to the control port of DPDT1. Based on the polarization of the antenna corresponding to the incoming wave signal (the process of determining the antenna polarization can be found in the subsequent section on antenna polarization switching), it outputs a low-level 0 or high-level 1 control signal to control the DPDT1's state switching. Specifically, when the CPU control unit outputs a low-level 0 (control signal 1 connected to DPDT1), pins 1 and 3 of DPDT1 are on, pins 2 and 4 are on, and the other pins of DPDT1 are off. When the CPU control unit outputs a high-level 1 (control signal 1 connected to DPDT1), pins 1 and 4 of DPDT1 are on, pins 2 and 3 are on, and the other pins of DPDT1 are off.

[0071] Pin 2 of the 90-degree bridge 1 is connected to a transmission line of length L1, and pin 3 of the 90-degree bridge is connected to a transmission line of length L2 (shorter than L1). When pin 1 of bridge 1 is powered, pin 2 is a coupling port with a phase of 0 degrees relative to pin 1, and pin 3 is a through port with a phase lag of 90 degrees relative to pin 1. Similarly, when pin 4 of bridge 1 is powered, pin 3 is a coupling port with a phase of 0 degrees relative to pin 4, and pin 2 is a through port with a phase lag of 90 degrees relative to pin 4.

[0072] A transmission line of length L1 connected to the 90-degree bridge 1 is then connected to pin 1 of another double-pole double-throw switch 2 (which can be defined as the second double-pole double-throw switch in this application, hereinafter referred to as DPDT2). The transmission line of length L2 connected to the 90-degree bridge 1 is connected to pin 2 of DPDT2. Pin 3 of DPDT2 is connected to a transmission line of length L3 (which can be the same length as L2), and then to a single-pole double-throw switch S1 (which can be defined as the first single-pole double-throw switch in this application), making it... After the switch is switched to the on state of pins 1 and 2, it connects to the P1 feed point of a dual-polarized antenna operating in the target frequency band. Pin 4 of DPDT2 is connected to the P2 feed point of this dual-polarized antenna via a transmission line of length L4 (which can be the same as L1), and then to a single-pole double-throw switch S2 (which can be defined as a second single-pole double-throw switch in this application). After its switch is switched to the on state of pins 1 and 2, it connects to the P2 feed point of this dual-polarized antenna. The phase differences of the electrical lengths of the four transmission line segments L1 / L2 / L3 / L4 are respectively ψ L1 / ψ L2 / ψ L3 / ψ L4 (Unit: degrees), the phase difference relationship is:

[0073] ψ L1 +ψ L3 =ψ L2 +ψ L4 ;

[0074] ψ L1 +ψ L4 =ψ L2 +ψ L3 +90°;

[0075] ψ L1 -ψ L2 =ψ L3 -ψ L4 =45°.

[0076] The CPU control unit's control signal pin 2 is connected to the DPDT2's control port. Based on the polarization of the antenna corresponding to the incoming wave signal, it outputs a low level (0) or a high level (1) to control the DPDT2's state switching. That is, when the CPU control unit outputs a low level (0) for the DPDT2's control signal pin 2, pins 1 and 3 of the DPDT2 are turned on, pins 2 and 4 are turned on, and the other pins of the DPDT2 are not turned on. When the CPU control unit outputs a high level (1) for the DPDT2's control signal pin 2, pins 1 and 4 of the DPDT2 are turned on, pins 2 and 3 are turned on, and the other pins of the DPDT2 are not turned on.

[0077] In this application, the dual-polarized antenna operating in the target frequency band can be a circular microstrip antenna. Figure 2This is a top view of a schematic diagram showing the antenna feed point setting in the antenna polarization switching circuit provided in this application embodiment. Figure 3 This is a side view of a schematic diagram showing the antenna feed point setting in the antenna polarization switching circuit provided in this application embodiment, as shown below. Figure 2 and Figure 3 As shown, this application takes a dual-polarized circular microstrip antenna as an example, with its feed points P1 and P2 being on the orthogonal crossing lines of the circular microstrip antenna, as shown in the figure. Figure 3 As shown, the lines connecting P1 and P2 to the center of the circle form a 90-degree angle and are equidistant from the center.

[0078] Therefore, when the CPU control unit is connected to DPDT1 and DPDT2, and the control signal 1 and control signal 2 respectively output different low level 0 or high level 1, the relative phase difference and antenna polarization of the corresponding antenna feed points P1 and P2 are as follows: Figure 4 As shown, Figure 4 This is one of the link diagrams in the antenna polarization switching circuit provided in the embodiments of this application. Figure 4 Instructions: When both DPDT1 and DPDT2 control signal levels are low (0), the antenna feed point Port1 connection path is as follows: Figure 4 As shown, P2 lags P1 by 90 degrees in phase, and the antenna switches to a right-hand circularly polarized antenna.

[0079] Figure 5 This is the second link diagram in the antenna polarization switching circuit provided in the embodiments of this application. Figure 5 Instructions: When the DPDT1 control signal level is low (0) and the DPDT2 control signal level is high (1), the antenna feed point Port1 connection path is as follows: Figure 5 As shown, P2 and P1 are in phase, and the antenna is switched to a vertically polarized antenna.

[0080] Figure 6 This is the third link diagram in the antenna polarization switching circuit provided in the embodiments of this application. Figure 6 Instructions: When the DPDT1 control signal level is high (1) and the DPDT2 control signal level is low (0), the antenna feed point Port1 connection path is as follows: Figure 6 As shown, P1 lags P2 by 90 degrees in phase, and the antenna is switched to a left-hand circularly polarized antenna.

[0081] Figure 7 This is the fourth link diagram in the antenna polarization switching circuit provided in the embodiments of this application. Figure 7 Instructions: When both DPDT1 and DPDT2 control signal levels are high (level 1), the antenna feed point Port1 connection path is as follows: Figure 7 As shown, P2 lags P1 by 180 degrees in phase, and the antenna switches to a horizontally polarized antenna.

[0082] Thus, by using control signal 1 and control signal 2 from the CPU control unit to output different high and low level signals, DPDT1 and DPDT2 are controlled to switch the feed network to different states, so that the signal amplitude at the two orthogonal feed points P1 and P2 of the dual-polarized antenna fed by Port1 is the same and the phase can be switched to different design schemes. Finally, an antenna scheme design is realized that the antenna can switch between four different polarization modes: left-hand circular polarization, right-hand circular polarization, vertical line polarization and horizontal line polarization.

[0083] Furthermore, the feed port1 point is connected to pin 2 of a single-pole triple-throw switch s3 via a transmission line to communicate with the radio frequency system. In this way, the radio frequency system can connect to port1 point and control DPDT1 and DPDT2 to switch between different high or low levels through the CPU control unit, so as to realize the switching of antenna scheme status for four different polarization modes: left-hand circular polarization, right-hand circular polarization, vertical line polarization and horizontal line polarization.

[0084] Meanwhile, when the RF system switches to pins 1 and 3 or 4 via a single-pole triple-throw switch s3, and the corresponding switches s1 and s2 switch to pins 1 and 3 respectively, when the RF system is connected to the feed point P1 or P2 of the dual-polarized circular microstrip antenna, the corresponding antenna polarization mode is switched to positive 45-degree linear polarization (connected to P1) or negative 45-degree linear polarization (connected to P2).

[0085] Specifically, even if the incoming wave from a wireless communication device is a linearly polarized antenna, polarization attenuation will still occur if the angle of arrival is inconsistent with the antenna polarization direction. The specific amount of polarization attenuation can be calculated using the following formula:

[0086] E θ =E cosθ;

[0087] P x =1-cos 2 θ.

[0088] θ is the angle between the direction of the received signal (i.e., the angle of arrival) and the antenna polarization direction, and E is the electric field value in the direction of the received signal. θ P represents the electric field component in the direction of the received incoming signal along the antenna polarization direction. x The polarization loss power attenuation ratio is the ratio of attenuated power to incoming signal power.

[0089] As can be seen from the above formula, the larger the angle θ between the incoming wave direction and the antenna polarization direction, the greater the polarization loss attenuation; the smaller the angle θ between the incoming wave direction and the antenna polarization direction, the smaller the polarization loss attenuation. Therefore, when the Port1 channel switches the antenna polarization mode to either vertical polarization or horizontal linear polarization, the maximum angle between the incoming wave signal and the antenna polarization angle can reach 45 degrees, and the maximum polarization attenuation can reach 50%.

[0090] This application uses switch s3 to switch the feed point P1 or P2 directly connected to the antenna, supplementing the antenna polarization mode as a positive 45-degree linearly polarized antenna (connected to P1) or a negative 45-degree linearly polarized antenna (connected to P2), reducing the maximum angle between the incoming wave signal and the antenna polarization angle to 22.5 degrees, effectively reducing the polarization loss attenuation caused by the angle of incoming wave of the linearly polarized antenna.

[0091] Thus, this application enables the switching of six antenna polarization states, including left-hand circular polarization, right-hand circular polarization, vertical polarization, horizontal polarization, positive 45-degree linear polarization, and negative 45-degree linear polarization, allowing for arbitrary switching of antenna polarization modes.

[0092] Therefore, this application designs two DPDT switches and a 90-degree bridge to design an antenna feed network with different electrical lengths and phase differences connecting the transmission lines. The DPDT switches can switch the antenna feed network, enabling the CPU control unit to control and switch the antenna of the wireless communication device to four different polarization modes: left-hand circular polarization, right-hand circular polarization, vertical linear polarization, and horizontal linear polarization. Combined with the original antenna's P1 and P2 points, positive 45-degree linear polarization and negative 45-degree linear polarization are achieved, realizing the switching design of six antenna polarization states: left-hand circular polarization, right-hand circular polarization, vertical linear polarization, horizontal linear polarization, positive 45-degree linear polarization, and negative 45-degree linear polarization.

[0093] This application uses a circular microstrip antenna with two vertical points as feeds. In fact, the above-mentioned feed network, combined with any other dual-polarization dual-feed antenna scheme, can realize an antenna scheme design with four different polarization modes that can be switched: left-hand circular polarization, right-hand circular polarization, vertical linear polarization, and horizontal linear polarization.

[0094] Furthermore, the feeder network design in this application is simple, with low link loss, which can effectively improve antenna communication performance.

[0095] Furthermore, this application also provides a method for switching antenna polarization modes.

[0096] Figure 8 This is a flowchart illustrating the antenna polarization switching method provided in an embodiment of this application, as shown below. Figure 8As shown, the antenna polarization switching method of this application may include:

[0097] Step 810: Connect the radio frequency system in the antenna polarization switching circuit to the first feed point of the two feed points of the dual-polarized antenna, and determine the first received signal strength and the first signal phase of the radio frequency system based on the antenna signal feedback;

[0098] Step 820: Connect the radio frequency system in the antenna polarization switching circuit to the second feed point of the two feed points of the dual-polarized antenna, and determine the strength and phase of the second received signal based on the antenna signal feedback of the radio frequency system;

[0099] Step 830: Connect the RF system in the antenna polarization switching circuit to the first feed point of the two feed points of the dual-polarized antenna, and determine the third signal phase of the RF system based on the antenna signal feedback;

[0100] Step 840: Based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase, and the third signal phase, determine the polarization mode of the antenna corresponding to the incoming signal;

[0101] Step 850: Based on the polarization mode of the antenna corresponding to the incoming wave signal, control the antenna polarization mode switching circuit to switch the antenna polarization mode.

[0102] Further, based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase, and the third signal phase, the polarization mode of the antenna corresponding to the incoming signal is determined, including:

[0103] Based on the first signal phase, the second signal phase, and the third signal phase, the signal phase difference between the first feed point and the second feed point is determined;

[0104] Based on the first received signal strength, the first signal phase, the second received signal strength and the second signal phase, the amplitude of the electric field of the left-hand circular polarization component, the amplitude of the electric field of the right-hand circular polarization component, and the axial ratio of the incoming signal are determined.

[0105] The polarization mode of the antenna corresponding to the incoming signal is determined based on the signal phase difference, the electric field amplitude of the left-hand polarization component of the incoming signal, the electric field amplitude of the right-hand polarization component, and the axial ratio.

[0106] It should be noted that the antenna polarization switching method in this application can be applied to the antenna polarization switching circuit mentioned above, and more specifically, it can be applied to the control unit in the antenna polarization switching circuit.

[0107] After completing the design of the antenna polarization switching circuit, it is also necessary to know the polarization of the incoming signal in order to control the antenna to switch to the corresponding polarization state (i.e., polarization mode) through the CPU control unit. The specific process is as follows:

[0108] Control signal 5 from the CPU control unit controls the single-pole triple-throw switch s3 connected to the RF system to switch pins 1 and 3 to conduct. Simultaneously, control signal 3 controls switch s1 to switch pins 1 and 3 to conduct. At this time, the RF system can receive the incoming signal (i.e., the antenna signal) at point P1 of the dual-polarized antenna, detecting the received signal strength PO1 (which can be defined as the first received signal strength in this application) and the signal phase ψ1 (which can be defined as the first signal phase in this application). Then, the CPU control unit controls switch s3 to switch pins 1 and 4 to conduct, and control signal 4 controls switch s2... When pins 1 and 3 are switched on, the RF system can receive the incoming signal from point P2 of the dual-polarized antenna and detect the received signal strength PO2 (which can be defined as the second received signal strength in this application) and the signal phase ψ2 (which can be defined as the second signal phase in this application). Then, the CPU control unit controls switch s3 to switch pins 1 and 3 on, and control signal 3 controls switch s1 to switch pins 1 and 3 on. At this time, the RF system can receive the incoming signal from point P1 of the dual-polarized antenna and detect the received signal phase ψ3 (which can be defined as the third signal phase in this application).

[0109] Furthermore, considering the impact of switch switching and signal processing time on the phase of the received signal, the phase difference between the received signals of P1 and P2 is: ψ is calculated using the following formula:

[0110] ψ2-ψ1= ψ+ψ x ;

[0111] ψ3-ψ2=- ψ+ψ x ;

[0112] ψ=(2 ψ2-ψ3-ψ1) / 2;

[0113] Where, ψ x When determining the phase difference between the received signals of P1 and P2, phase detection errors are caused by factors such as switch switching time and system calculation time.

[0114] This application detects the phases of three signals by switching the signals three times, and eliminates ψ using the above formula. x The effect of this is used to obtain the actual phase difference between the received signals of P1 and P2. ψ.

[0115] Furthermore, based on the following polarization gain calculation formula, the amplitudes of the left-hand and right-hand circular polarization electric fields, as well as the axial ratio AR, of the wave signal can be calculated:

[0116] Im(E PO1 )=PO1 cosψ1,Re(E PO1 )=PO1 sinψ1;

[0117] Im(E PO2 )=PO2 cosψ2,Re(E PO2 )=PO2 sinψ2;

[0118] E LHCP =((1 / 2) (Im(E PO1 )+Re(E PO2 ))2+(1 / 2) (Re(E PO1 )-Im(E PO2 ))2)0.5;

[0119] E RHCP =((1 / 2) (Im(E PO1 )-Re(E PO2 ))2+(1 / 2) (Re(E PO1 )+Im(E PO2 ))2)0.5;

[0120] AR=20 LOG(((E LHCP / E RHCP )+1) / ((E LHCP / E RHCP )-1)).

[0121] Where Im(E) PO1 Re(E) represents the real part of the electric field of the signal received at point P1. PO1 ) represents the imaginary part of the electric field of the received signal at point P1, Im(E) PO2 Re(E) represents the real part of the electric field of the signal received at point P2. PO2 E represents the imaginary part of the electric field of the signal received at point P2. LHCP E represents the amplitude of the left-handed polarization component of the electric field. RHCP This represents the amplitude of the right-handed polarization component electric field.

[0122] According to the maximum polarization attenuation of the linearly polarized antenna in this application, P is... x =1-cos2 22.5° = 14.6%, corresponding to the ratio of the axial ratio of the main polarization attenuation and the ratio of the major axis component of elliptic polarization. Combined, it is determined that when the axial ratio is less than or equal to 10, this application can use circular polarization to receive the incoming signal, resulting in lower polarization loss. Furthermore, based on the above formula, when E... LHCP >E RHCP When E is determined to be a left-hand circularly polarized wave, it is determined that the received incoming signal is a left-hand circularly polarized wave. LHCP <E RHCP At that time, the received incoming wave signal is determined to be a right-hand circularly polarized wave.

[0123] According to the maximum polarization attenuation of the linearly polarized antenna in this application, P is... x =1-cos 2 22.5° = 14.6%, corresponding to the ratio of the axial ratio of the main polarization attenuation and the ratio of the major axis component of the elliptic polarization. Based on this, when the axial ratio is greater than 10, this application can use linear polarization to receive the incoming signal, resulting in lower polarization loss. Next, we further determine the linear polarization angle of the incoming signal when the axial ratio is greater than 10. According to the received signal phase as described above, a. When PO1 = PO2, When ψ=0, the received signal is determined to be a vertically polarized wave; b. When PO1=PO2, When ψ=180, the received signal is determined to be a horizontally polarized wave; c. When PO1 is much greater than PO2 (for example, the difference between PO1 and PO2 is greater than a positive threshold set in advance according to actual needs), the received signal is determined to be a positive 45-degree linearly polarized wave; d. When PO1 is much less than PO2 (for example, the difference between PO1 and PO2 is less than another negative threshold set in advance according to actual needs), the received signal is determined to be a negative 45-degree linearly polarized wave.

[0124] Based on the above method, the RF system can determine the polarization of the incoming signal by detecting the amplitude and phase of the signals at antenna points P1 and P2. The CPU control unit can then calculate this polarization. Therefore, regardless of the polarization of the incoming signal from the other wireless communication device's antenna, the system can first detect and determine the polarization of the received signal. Then, the CPU control unit controls the dual-polarized antenna to intelligently switch to the optimal polarization matching mode among six antenna polarization modes: left-hand circular polarization, right-hand circular polarization, vertical linear polarization, horizontal linear polarization, positive 45-degree linear polarization, and negative 45-degree linear polarization. This ensures minimal polarization loss attenuation for both wireless communication devices, effectively improving communication performance.

[0125] Based on the antenna polarization switching circuit, this application connects antenna points P1 and P2 respectively through the radio frequency system to detect the amplitude and phase of the received signal. Then, it determines the polarization mode of the received incoming wave signal through a formula algorithm, and controls the communication antenna to switch to the best matching received signal polarization mode among the six polarization modes, thereby improving the communication performance of the device.

[0126] Furthermore, this application also establishes a model of the aforementioned antenna polarization switching circuit using three-dimensional antenna simulation software, as shown above. Figure 2 As shown, simulation evaluation demonstrates the design of a switchable polarization antenna scheme achieved by switching the antenna feed network link in this application.

[0127] First, the original simulation results of the dual-polarized circular microstrip antenna designed in this application are obtained, and then:

[0128] a. When both DPDT1 and DPDT2 are input at a low level (0), the corresponding P2 phase lags P1 by 90 degrees as the feed network. The feed network is then connected to the original antenna simulation results for post-processing fitting to obtain the final antenna total gain, right-hand circular polarization component gain, and axial ratio. According to the simulation results, the antenna axial ratio is very small, indicating that the antenna is circularly polarized. Furthermore, the right-hand circular polarization component gain is close to the total gain, indicating that the antenna is a right-hand circularly polarized antenna. Specific simulation results are as follows: Figure 9 and Figure 10 As shown ( Figure 9 This is a schematic diagram comparing the right-hand circular polarization gain of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application. Figure 10 This is a schematic diagram of the right-hand circular polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application. The data is summarized in Table 1 below:

[0129] Table 1. Comparison of Antenna Polarization Gain and Axial Ratio Results

[0130]

[0131] b. Similarly, based on the same original antenna simulation results, when the DPDT1 control signal level is low (0) and the DPDT2 control signal level is high (1), P2 and P1 are considered to be in phase. The feed network is then connected to the original antenna simulation results for post-processing fitting to obtain the final antenna total gain, vertical polarization component gain, and axial ratio. The simulation results show a very large axial ratio, indicating that the antenna is linearly polarized. Furthermore, the vertical polarization component gain is close to the total gain, indicating that the antenna is vertically linearly polarized. Specific simulation results are as follows: Figure 11 and Figure 12 As shown ( Figure 11 This is a schematic diagram comparing the vertical line polarization gain of the simulation results in the antenna polarization switching circuit provided in this application embodiment. Figure 12 This is a schematic diagram of the vertical polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application), and the data is summarized in Table 1 above.

[0132] c. Similarly, based on the same original antenna simulation results, when the DPDT1 control signal level is high (1) and the DPDT2 control signal level is low (0), the corresponding P1 phase lags P2 by 90 degrees as the feed network. The feed network is then connected to the original antenna simulation results for post-processing fitting to obtain the final antenna total gain, left-hand circular polarization component gain, and axial ratio. The simulation results show a very small axial ratio, indicating that the antenna is circularly polarized. Furthermore, the left-hand circular polarization component gain is close to the total gain, indicating that the antenna is a left-hand circularly polarized antenna. The specific simulation results are as follows: Figure 13 and Figure 14 As shown ( Figure 13 This is a schematic diagram comparing the left-hand circular polarization gain of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application. Figure 14 This is a schematic diagram of the left-hand circular polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application. The data is summarized in Table 1 above.

[0133] d. Similarly, based on the same original antenna simulation results, when both DPDT1 and DPDT2 control signal levels are high (level 1), the corresponding P2 phase lags P1 by 180 degrees as the feed network. The feed network is then connected to the original antenna simulation results for post-processing fitting to obtain the final antenna total gain, horizontal polarization component gain, and axial ratio results. The simulation results show a very large axial ratio, indicating that the antenna is a linearly polarized antenna. Furthermore, the horizontal polarization component gain is close to the total gain, indicating that the antenna is a horizontally linearly polarized antenna. The specific simulation results are as follows: Figure 15 and Figure 16 As shown ( Figure 15 This is a schematic diagram comparing the horizontal polarization gain of the antenna polarization switching circuit provided in the embodiments of this application. Figure 16 This is a schematic diagram of the horizontal polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application), and the data is summarized in Table 1 above.

[0134] e. Similarly, based on the same original antenna simulation results, we then examine the original antenna simulation results for antenna P1. The simulation results show a very large axial ratio, indicating that the antenna is a linearly polarized antenna. Furthermore, the polarization component gain in the positive 45-degree direction is close to the total gain, indicating that the antenna is a positive 45-degree linearly polarized antenna. The specific simulation results are as follows: Figure 17 and Figure 18 As shown ( Figure 17 This is a schematic diagram comparing the simulation results of the antenna polarization switching circuit provided in this application embodiment, showing the gain of the positive 45-degree linear polarization. Figure 18This is a schematic diagram of the positive 45-degree linear polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application. The data is summarized in Table 1 above.

[0135] f. Similarly, based on the same original antenna simulation results, we then examine the simulation results of the original antenna P2. The simulation results show a very large axial ratio, indicating that the antenna is a linearly polarized antenna. Furthermore, the polarization component gain in the negative 45-degree direction is close to the total gain, indicating that the antenna is a negative 45-degree linearly polarized antenna. The specific simulation results are as follows: Figure 19 and Figure 20 As shown ( Figure 19 This is a schematic diagram comparing the negative 45-degree linear polarization gain of the antenna polarization switching circuit provided in the embodiments of this application. Figure 20 This is a schematic diagram of the negative 45-degree linear polarization axis ratio of the simulation results in the antenna polarization switching circuit provided in the embodiments of this application. The data is summarized in Table 1 above.

[0136] Therefore, through the above simulation evaluation, it is confirmed that the switchable feed network and antenna scheme design of this application can realize the switching of multi-polarization mode, that is, the design of this application is feasible and effective.

[0137] In another aspect, embodiments of this application also provide a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the methods provided in the above embodiments, including, for example, controlling the connection of the radio frequency system in the antenna polarization switching circuit to the first feed point of the two feed points of the dual-polarized antenna, and determining the first received signal strength and the first signal phase of the radio frequency system based on the antenna signal feedback;

[0138] The radio frequency system in the control antenna polarization switching circuit is connected to the second feed point of the two feed points of the dual-polarized antenna, and the strength and phase of the second received signal of the radio frequency system based on the antenna signal feedback are determined;

[0139] The radio frequency system in the control antenna polarization switching circuit is connected to the first feed point of the two feed points of the dual-polarized antenna, and the third signal phase of the radio frequency system is determined based on the antenna signal feedback;

[0140] Based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase, and the third signal phase, the polarization mode of the antenna corresponding to the incoming signal is determined;

[0141] Based on the polarization mode of the antenna corresponding to the incoming wave signal, the antenna polarization mode switching circuit is controlled to switch the antenna polarization mode.

[0142] In another aspect, embodiments of this application also provide a computer program product having a computer program stored thereon. When the computer program is executed by a processor, it implements the methods provided in the above embodiments, such as: controlling the connection of the radio frequency system in the antenna polarization switching circuit to the first feed point of the two feed points of the dual-polarized antenna, and determining the first received signal strength and the first signal phase of the radio frequency system based on the antenna signal feedback.

[0143] The radio frequency system in the control antenna polarization switching circuit is connected to the second feed point of the two feed points of the dual-polarized antenna, and the strength and phase of the second received signal of the radio frequency system based on the antenna signal feedback are determined;

[0144] The radio frequency system in the control antenna polarization switching circuit is connected to the first feed point of the two feed points of the dual-polarized antenna, and the third signal phase of the radio frequency system is determined based on the antenna signal feedback;

[0145] Based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase, and the third signal phase, the polarization mode of the antenna corresponding to the incoming signal is determined;

[0146] Based on the polarization mode of the antenna corresponding to the incoming wave signal, the antenna polarization mode switching circuit is controlled to switch the antenna polarization mode.

[0147] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0148] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, can be embodied in the form of software products. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate this application and are not intended to limit this application. Although this application has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of this application do not depart from the spirit and scope of the technical solutions of this application.

Claims

1. An antenna polarization mode switching circuit, characterized by, The antenna polarization mode switching circuit comprises a control unit, a radio frequency system and a polarization switching module. The polarization switching module comprises a first double-pole double-throw switch, a bridge, a second double-pole double-throw switch and a single-pole triple-throw switch. One end of the first double-pole double-throw switch is connected to the single-pole triple-throw switch, and the other end is connected to the bridge. The other end of the bridge is connected to the second double-pole double-throw switch. The other end of the second double-pole double-throw switch is connected to the two feed points of the dual-polarized antenna through the first single-pole double-throw switch and the second single-pole double-throw switch. The radio frequency system is connected to the first double-pole double-throw switch or any one of the two feed points of the dual-polarized antenna through the single-pole triple-throw switch, for receiving antenna signals or transmitting radio frequency signals. The control unit outputs control signals to the switches in the polarization switching module to switch the polarization mode of the dual-polarized antenna by switching the connection state of the switches. The polarization switching module further comprises a first single-pole double-throw switch and a second single-pole double-throw switch. The other end of the second double-pole double-throw switch is connected to the two feed points of the dual-polarized antenna through the first single-pole double-throw switch and the second single-pole double-throw switch.

2. The antenna polarization switching circuit of claim 1, wherein The radio frequency system is connected to the corresponding feed point of the two feed points of the dual-polarized antenna through the single-pole triple-throw switch, the first single-pole double-throw switch or the second single-pole double-throw switch.

3. The antenna polarization switching circuit of claim 1, wherein The two pins of the bridge are connected to the two different pins of the second double-pole double-throw switch through transmission lines with different lengths.

4. An antenna polarization switching method applied to the antenna polarization switching circuit according to any one of claims 1 to 3, characterized by, The two different pins of the second double-pole double-throw switch are connected to the first single-pole double-throw switch and the second single-pole double-throw switch through transmission lines with different lengths. The bridge is a 90-degree bridge. One end of the first double-pole double-throw switch connected to the single-pole triple-throw switch is also connected to a resistor. The antenna polarization mode switching circuit comprises a control unit, a radio frequency system and a polarization switching module. The radio frequency system is connected to the first feed point of the two feed points of the dual-polarized antenna, and determines the first received signal strength and the first signal phase based on the antenna signal feedback. The radio frequency system is connected to the second feed point of the two feed points of the dual-polarized antenna, and determines the second received signal strength and the second signal phase based on the antenna signal feedback.

5. The antenna polarization mode switching method of claim 4, wherein, The radio frequency system is connected to the first feed point of the two feed points of the dual-polarized antenna, and determines the third signal phase based on the antenna signal feedback. Based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase and the third signal phase, the polarization mode of the incoming wave signal corresponding antenna is determined. Based on the polarization mode of the incoming wave signal corresponding antenna, the antenna polarization mode switching circuit is controlled to switch the antenna polarization mode. The determination of the polarization mode of the incoming wave signal corresponding antenna based on the first received signal strength, the first signal phase, the second received signal strength, the second signal phase and the third signal phase comprises: determining a signal phase difference between the first feeding point and the second feeding point based on the first signal phase, the second signal phase and the third signal phase; determining a left-handed polarization component electric field amplitude, a right-handed polarization component electric field amplitude and an axial ratio of the incoming wave signal based on the first received signal strength, the first signal phase, the second received signal strength and the second signal phase; determining a polarization mode of an antenna corresponding to the incoming wave signal based on the signal phase difference, the left-handed polarization component electric field amplitude, the right-handed polarization component electric field amplitude and the axial ratio of the incoming wave signal.

6. A storage medium, which is a non-transitory computer-readable storage medium, having stored thereon a computer program, characterized in that, The computer program is executed by a processor to implement the antenna polarization mode switching method according to any one of claims 4-5.

7. A computer program product comprising a computer program, characterized in that, The computer program is executed by a processor to implement the antenna polarization mode switching method according to any one of claims 4-5.

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