Broadband antenna matching structure and working method and design method thereof

Abstract

The invention relates to the technical field of broadband antennas, and provides a broadband antenna matching structure and a working method and design method thereof, the broadband antenna matching structure comprises a radio frequency input interface Rfin, a power amplifier PA, a matching network, a directional coupler and an antenna which are connected in sequence; and the matching network is used for carrying out frequency band division, impedance matching and signal synthesis according to an antenna standing wave coefficient. According to the invention, the broadband antenna is divided into two or more sections, then low-frequency-band signals are connected with the antenna after passing through the matching network, and high-frequency-band signals are directly connected with the antenna. Signals are automatically shunted and converged according to the impedance of a designed matching network, a certain overlapping band exists between different frequency bands, broadband signals can work at the same time, theoretically, the circuit can be utilized to continue to expand and reduce the antenna standing wave coefficient of each frequency band, and the circuit can be applied to various radio frequency systems.

Description

Technical Field

[0001] The present invention relates to the technical field of broadband antennas, and in particular to a working method and a design method of a broadband antenna matching structure. Background Art

[0002] Power amplifiers and antennas are important components of communication test systems. Different application systems require different frequencies, ranging from a few kHz to over GHz, covering the VLF-UHF frequency band, and their power ranges from tens of watts to several kilowatts. The wider the bandwidth of the antenna, the more applicable it is to more scenarios and systems. For antennas, the power amplifier is usually directly connected to the antenna without matching in the middle. The standing wave coefficient of the antenna is relatively large in the low frequency band. If the power amplifier is directly connected to an unmatched antenna, the radiation efficiency will be low. Therefore, in the case of broadband, a matching method is needed to match the circuit between the power amplifier and the antenna. Summary of the invention

[0003] In order to achieve a good reflection coefficient in the low-frequency band of the antenna, the present invention aims to provide a broadband antenna matching structure, which is based on a fusion design of frequency overlap and utilizes a frequency selectivity to automatically distribute the radio frequency signal of the circuit to the corresponding frequency band according to this frequency selectivity. The low-frequency band is matched and then connected to the antenna, while the high-frequency band is directly connected to the antenna, thereby solving the problem of a large standing wave coefficient in the low-frequency band. Moreover, this matching network is adjustable. According to the reflection standing wave detection result of the directional coupler, the matching network is controlled by an external controller for adjustment, so that the standing wave is minimized within the frequency band or a relatively low standing wave is obtained.

[0004] The present invention provides a broadband antenna matching structure working method and design method, including a radio frequency input interface Rfin, a power amplifier PA, a matching network, a directional coupler and an antenna connected in sequence; The matching network is used to perform frequency band division, impedance matching and signal synthesis according to the antenna standing wave.

[0005] In some embodiments, the matching network includes an inter-frequency power division circuit, an inter-frequency synthesis circuit, and a matching circuit; The radio frequency input interface Rfin is connected to the input end of the heterofrequency power division circuit via the power amplifier PA; the first output end of the heterofrequency power division circuit is connected to the first input end of the heterofrequency synthesis circuit via the matching circuit; the second output end of the heterofrequency power division circuit is directly connected to the second input end of the heterofrequency synthesis circuit; the output end of the heterofrequency synthesis circuit is connected to the antenna via a directional coupler.

[0006] In some embodiments, the directional coupler is connected to a matching circuit via an external controller; The external controller is used to adjust the impedance of the matching circuit according to the forward and reverse powers detected by the directional coupler.

[0007] In some embodiments, there are multiple matching circuits; Each matching circuit is connected in parallel between the different-frequency power division circuit and the different-frequency synthesis circuit; Each matching circuit is controlled by an external controller.

[0008] In some embodiments, the matching circuit is composed of capacitor and inductor matching devices.

[0009] In some embodiments, the matching circuit is an L-type or Π-type matching circuit composed of capacitor and inductor matching devices.

[0010] In a second aspect, the working method of the broadband antenna matching structure includes: The RF input interface RFin inputs the RF signal, and after being amplified by the power amplifier, the signal is divided into two or more segments according to the frequency through the different-frequency power division circuit, at least into a low-frequency band signal and a high-frequency band signal; The high-frequency signal is directly input into the frequency synthesis circuit; the low-frequency signal enters the matching circuit, which is adjustable by an external controller to transform the impedance into the value required by the input, and then synthesized by the frequency synthesis circuit and the high-frequency signal; The synthesized signal enters the directional coupler to detect the forward and reverse powers, and is finally radiated through the antenna, wherein the forward and reverse powers detected by the directional coupler are fed back to the external controller.

[0011] In some embodiments, the low-frequency band signal and the high-frequency band signal have overlapping portions.

[0012] In a third aspect, the design method of the broadband antenna matching structure comprises the following steps: Step 1, obtain the S parameters of the antenna; Step 2: Divide the high and low frequency bands according to the standing wave coefficient of the antenna; Step 3: Determine the low-frequency target impedance according to the high and low frequency bands divided in step 2; Step 4: Perform impedance matching for the low-frequency target impedance, and finally determine the appropriate devices to form a matching circuit; Step 5: determine whether the matching circuit meets the matching requirements. If so, proceed to step 6; if not, return to adjust the matching circuit. Step 6, designing the different-frequency power division circuit and the different-frequency synthesis circuit; Step 7: According to the global impedance target, the matching network composed of the matching circuit, the different-frequency power division circuit and the different-frequency synthesis circuit is optimized as a whole; Step 8, determine whether the matching network meets the standing wave coefficient in the entire frequency band. If so, proceed to the next step; if not, redesign the inter-frequency power division circuit and inter-frequency synthesis circuit and optimize them; Step 9: Add the antenna to the final matching network and perform simulation; Step 10: Determine whether the indicators such as the standing wave coefficient meet the requirements based on the simulation results. If they do, complete the design. If not, return to step 4.

[0013] In some embodiments, in step 6, a non-isolated T-type connector is first used for connection, and then the parameters of the connection circuit are adjusted according to the design objectives, and finally the hetero-frequency power division circuit and the hetero-frequency synthesis circuit are obtained.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The present invention aims to solve the problem that the antenna has poor standing wave coefficient in the low frequency band. Directly connecting the antenna after the power amplifier will lead to poor antenna efficiency. Therefore, the broadband antenna is divided into two or more sections, and then the low-frequency signal is connected to the antenna through a matching network, while the high-frequency signal is directly connected to the antenna. The signal is automatically divided and converged according to the impedance of the designed matching network. There is a certain overlap between different frequency bands, which can meet the simultaneous operation of broadband signals. In theory, this circuit can be further expanded to reduce the standing wave coefficient of antennas in each frequency band, and can be applied to a variety of radio frequency systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of a broadband antenna matching structure in an embodiment of the present invention.

[0016] Figure 2 It is a schematic diagram of the frequency band division of the broadband antenna matching structure in an embodiment of the present invention.

[0017] Figure 3 It is a schematic diagram of the 9kHz~100MHz frequency band division of the broadband antenna matching structure in an embodiment of the present invention.

[0018] Figure 4 Schematic diagram of the structure of the matching network in an embodiment of the present invention.

[0019] Figure 5 Flow chart of a method for designing a broadband antenna matching structure in an embodiment of the present invention.

[0020] Figure 6 This is a standing wave curve diagram of the 9kHz~100MHz antenna in an embodiment of the present invention.

[0021] Figure 7 Schematic diagram of a Π-type matching circuit in an embodiment of the present invention.

[0022] Figure 8 This is a standing wave curve of the antenna after 9kHz~21kHz matching in an embodiment of the present invention.

[0023] Fig. 9This is a standing wave curve of the antenna after 20kHz~52kHz matching in an embodiment of the present invention.

[0024] Fig.10 This is a standing wave curve of the antenna after 50kHz~100MHz matching in an embodiment of the present invention.

[0025] Fig.11 Schematic diagram of the 9kHz~100MHz broadband antenna matching structure of two matching networks in an embodiment of the present invention.

[0026] Fig.12 Schematic diagram of a broadband antenna matching structure of multiple matching networks in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example like Figure 1 As shown, this embodiment proposes a broadband antenna matching structure, including a radio frequency input interface Rfin, a power amplifier PA, a matching network, a directional coupler and an antenna E1 connected in sequence; the matching network is used to perform frequency band division, impedance matching and signal synthesis according to the antenna standing wave.

[0030] In some embodiments, the matching network includes a heterofrequency power division circuit, a heterofrequency synthesis circuit and a matching circuit; the RF input interface Rfin is connected to the input end of the heterofrequency power division circuit via a power amplifier PA; the first output end of the heterofrequency power division circuit is connected to the first input end of the heterofrequency synthesis circuit via a matching circuit; the second output end of the heterofrequency power division circuit is directly connected to the second input end of the heterofrequency synthesis circuit; the output end of the heterofrequency synthesis circuit is connected to the antenna via a directional coupler.

[0031] In some embodiments, the directional coupler is connected to a matching circuit via an external controller; the external controller is used to adjust the impedance of the matching circuit according to the forward and reverse powers detected by the directional coupler.

[0032] Its working principle is as follows: the RF input interface RFin inputs the RF signal, and after being amplified by the power amplifier, the signal is divided into two or more segments according to the frequency through the heterofrequency power division circuit, at least divided into low-frequency band signals and high-frequency band signals, wherein the high-frequency band signal is directly input into the heterofrequency synthesis circuit, and the low-frequency band signal enters the matching circuit. The matching circuit is adjustable through an external controller to transform the impedance into the value required by the input, and then synthesized through the heterofrequency synthesis circuit and the high-frequency band signal. The synthesized signal enters the directional coupler to detect the forward and reverse power, and finally radiated through the antenna, wherein the forward and reverse power detected by the directional coupler is fed back to the external controller.

[0033] The power division and synthesis within the entire frequency band are realized by hardware circuits and do not require control. Signals of different frequencies automatically enter the corresponding circuits and are output after channel synthesis coupling. Even when the input signal spans two channels, they can work simultaneously. For the input and output ports, no operation or interference is required, and the internal multiple channel structure cannot be felt.

[0034] Figure 2 This is a frequency division diagram of a broadband antenna matching structure. The frequency bandwidth of the input RF signal is f1~f4. The signal is divided into low-frequency signals f1~f3 and high-frequency signals f2~f4 according to the frequency through the inter-frequency power division circuit, where f2 and f3 are -10dB power drop points. Path 1 is the low-frequency signal passing through the matching circuit, and path 2 is the high-frequency signal directly input into the inter-frequency synthesis circuit. There is a certain overlap between the f2~f3 frequency band of the low-frequency signals f1~f3 and the high-frequency signals f2~f4. The low-frequency signals f1~f3 enter the matching circuit (path 1). In the overlapping area, the power distribution varies with the frequency. There are more signals entering the matching circuit (path 1) at f2. As the frequency increases, the signals entering path 2 gradually increase, and there are more signals entering path 2 at f3. The division ratio is determined by the impedance of the hardware circuit. It can also work simultaneously for signals with a certain bandwidth. The low-frequency band signals f1~f3 pass through the matching circuit and the high-frequency band signals f2~f4 through the heterodyne synthesis circuit, and then the standing wave detection is performed through the directional coupler, and finally the signals of the f1~f4 frequency band are emitted through the antenna.

[0035] like Figure 3 As shown, take a broadband antenna covering 9kHz~100MHz as an example: The frequency of the RF signal input to the broadband antenna matching structure is 9kHz~100MHz. After passing through the heterodyne power division circuit, it is divided into two parts: a low-frequency signal of 9kHz~20MHz and a high-frequency signal of 1MHz~100MHz. The low-frequency signal of 9kHz~20MHz enters the matching circuit, and after impedance transformation, it is synthesized into a 9kHz~100MHz frequency band signal through the heterodyne synthesis circuit with the high-frequency signal of 1MHz~100MHz, and then transmitted through the antenna after passing through the directional coupler.

[0036] For signals in the 9kHz~1MHz frequency band, the loss of the matching circuit is very small, while the loss of direct connection is very large, so the signal is only transmitted through the matching circuit.

[0037] For signals in the 1MHz~20MHz frequency band, the signals are mixed and passed. At 1MHz, the loss of the matching circuit is very low, and the loss of the direct connection is very high. The signals in this frequency band are all transmitted through the matching circuit. In the process of gradually transitioning from 1MHz to 20MHz, the loss of the matching circuit gradually increases, and the corresponding loss of the direct connection gradually decreases, so part of the power will gradually be diverted from the matching circuit to the direct connection. At 20MHz, the loss of the matching circuit is very large, and the loss of the direct connection is very low, and the signals are all transmitted through the direct connection.

[0038] For signals in the 20MHz~100MHz frequency band, the direct connection loss is very small, while the matching circuit loss is very large, so the signal is transmitted directly through the transmission line.

[0039] like Figure 4 As shown in FIG. 1 , the inter-frequency power division circuit, the inter-frequency synthesis circuit and the matching circuit are connected through transmission lines to form a matching network. The main function of the matching network is to match the impedance to the target impedance of the antenna low frequency band. Figure 4 The matching network mainly works in the 9kHz~20MHz frequency band, so its form is an inductor-capacitor matching device, and the transmission line connection mainly works in the 1MHz~100MHz frequency band, so its form is a microstrip line. The common end (1, 6 ports) of the heterodyne power division circuit and the heterodyne frequency synthesis circuit is a system impedance of 50Ω, while the power division / synthesis port (2, 3, 4, 5 ports) is an impedance that changes with frequency. The design method is similar to that of the duplexer, but the difference is that there is no frequency interval.

[0040] There are two modes for the matching network of low-frequency capacitors and inductors. One is to directly look up the table to fix the starting value, and the other is to calculate and adjust according to a pre-given step.

[0041] For high frequency direct connection, 50Ω transmission line connection is mainly used.

[0042] like Figure 5 As shown, the design method of the broadband antenna matching structure includes the following steps: Step 1: Obtain the S parameters of the antenna. In some embodiments, the S parameters of the antenna can be obtained through the manufacturer's device data, simulation models, and testing of the actual object.

[0043] Step 2: Divide the high and low frequency bands according to the standing wave coefficient of the antenna.

[0044] Step 3: Determine the target impedance of the low frequency band according to the high and low frequency bands divided in step 2.

[0045] Step 4: Perform impedance matching for the low-frequency target impedance, and finally determine the appropriate capacitance and inductance values ​​to form an L-type or Π-type matching circuit.

[0046] Step 5: Determine whether the matching circuit meets the matching requirements. If so, proceed to step 6; if not, return to adjust the matching circuit.

[0047] Step 6. Design the inter-frequency power division circuit and inter-frequency synthesis circuit. The design method of the inter-frequency power division circuit and the inter-frequency synthesis circuit is similar to that of the duplexer, except that there is no frequency interval. First, use a non-isolated T-type connector for connection, and then adjust the parameters of the connection circuit according to the design goal. The final inter-frequency power division circuit and inter-frequency synthesis circuit are similar to the superposition of a low-pass filter and a high-pass filter.

[0048] Step 7: According to the global impedance target, the matching network composed of the matching circuit, the different-frequency power division circuit and the different-frequency synthesis circuit is optimized as a whole.

[0049] Step 8: Determine whether the matching network meets the standing wave coefficient in the entire frequency band. If so, proceed to the next step; if not, redesign the inter-frequency power division circuit and inter-frequency synthesis circuit and optimize them.

[0050] Step 9: Add the antenna to the final matching network and perform simulation; Step 10: Determine whether the indicators such as the standing wave coefficient meet the requirements based on the simulation results. If they do, complete the design. If not, return to step 6.

[0051] As Figure 6 Take the 9kHz~100MHz antenna standing wave as an example, where the horizontal axis is frequency and the vertical axis is standing wave. The antenna standing wave is very poor in the low frequency band 9kHz-50kHz. Therefore, the frequency band division is determined first. In this example, the frequency band is divided into three sections, namely 9kHz-21kHz, 20kHz-52kHz, and 50kHz-100MHz. Secondly, the target impedance of the low frequency band is determined. In this example, S parameters are used for matching. Then the design of the matching network for the 9kHz-21kHz frequency band and the 20kHz-52kHz frequency band is a Π-type matching network, such as Figure 7As shown. The 50kHz-100MHz frequency band is directly connected to the antenna. Finally, the antenna standing waves of the 9kHz-21kHz and 20kHz-52kHz frequency bands are obtained, as shown Figure 8 , Fig. 9 , Fig.10 As shown, the horizontal axis is frequency and the vertical axis is standing wave. The specific broadband antenna matching structure is as follows Fig.11 As shown above, it can be seen that the broadband antenna is divided into several frequency bands through the different-frequency power division circuit, and the standing wave in the low-frequency band with larger standing wave is lowered through the matching network, and the frequency band with small standing wave is directly connected to the power amplifier.

[0052] Based on this design method, more matching circuits can be synthesized using different-frequency power division circuits and different-frequency synthesis circuits to further expand the working bandwidth, such as Fig.12 There are n matching circuits shown.

[0053] From the above, it can be seen that the broadband antenna matching structure and design method provided by the present invention are aimed at the defect that the antenna has poor standing wave coefficient in the low frequency band. Directly connecting the antenna after the power amplifier will cause the antenna efficiency to deteriorate. Therefore, the broadband antenna is divided into two or more sections, and then the low-frequency band signal is connected to the antenna after passing through the matching network, while the high-frequency band signal is directly connected to the antenna. The signal is automatically shunted and converged according to the impedance of the designed matching network. There is a certain overlap between different frequency bands, which can meet the simultaneous operation of broadband signals. In theory, this circuit can be further expanded to reduce the standing wave coefficient of antennas in each frequency band, and can be applied to a variety of radio frequency systems.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A broadband antenna matching structure, characterized in that: It includes a radio frequency input interface Rfin, a power amplifier PA, a matching network, a directional coupler and an antenna which are connected in sequence; The matching network is used to perform frequency band division, impedance matching and signal synthesis according to the antenna standing wave.

2. The broadband antenna matching structure according to claim 1, characterized in that: The matching network includes a different-frequency power division circuit, a different-frequency synthesis circuit and a matching circuit; The radio frequency input interface Rfin is connected to the input end of the heterofrequency power division circuit via the power amplifier PA; the first output end of the heterofrequency power division circuit is connected to the first input end of the heterofrequency synthesis circuit via the matching circuit; the second output end of the heterofrequency power division circuit is directly connected to the second input end of the heterofrequency synthesis circuit; the output end of the heterofrequency synthesis circuit is connected to the antenna via a directional coupler.

3. The broadband antenna matching structure according to claim 2, characterized in that: The directional coupler is connected to a matching circuit via an external controller; The external controller is used to adjust the impedance of the matching circuit according to the forward and reverse powers detected by the directional coupler.

4. The broadband antenna matching structure according to claim 3, characterized in that: There are multiple matching circuits; Each matching circuit is connected in parallel between the different-frequency power division circuit and the different-frequency synthesis circuit; Each matching circuit is controlled by an external controller.

5. The broadband antenna matching structure according to claim 2, characterized in that: The matching circuit is composed of capacitor and inductor matching components.

6. The broadband antenna matching structure according to claim 5, characterized in that: The matching circuit is an L-type or Π-type matching circuit composed of capacitor and inductor matching components.

7. A method for operating the broadband antenna matching structure according to any one of claims 1 to 6, characterized in that: include: The RF input interface RFin inputs the RF signal, and after being amplified by the power amplifier, the signal is divided into two or more segments according to the frequency through the different-frequency power division circuit, at least into a low-frequency band signal and a high-frequency band signal; The high-frequency signal is directly input into the frequency synthesis circuit; the low-frequency signal enters the matching circuit, which is adjustable by an external controller to transform the impedance into the value required by the input, and then synthesized by the frequency synthesis circuit and the high-frequency signal; The synthesized signal enters the directional coupler to detect the forward and reverse powers, and is finally radiated through the antenna, wherein the forward and reverse powers detected by the directional coupler are fed back to the external controller.

8. The working method of the broadband antenna matching structure according to claim 7, characterized in that: The low-frequency band signal and the high-frequency band signal have overlapping parts.

9. A method for designing a broadband antenna matching structure according to any one of claims 1 to 6, characterized in that: The steps include: Step 1, obtain the S parameters of the antenna; Step 2: Divide the high and low frequency bands according to the standing wave coefficient of the antenna; Step 3: Determine the low-frequency target impedance according to the high and low frequency bands divided in step 2; Step 4: impedance matching is performed for the low-frequency target impedance, and the final determined devices form a matching circuit; Step 5: determine whether the matching circuit meets the matching requirements. If so, proceed to step 6; if not, return to adjust the matching circuit. Step 6, designing the different-frequency power division circuit and the different-frequency synthesis circuit; Step 7: According to the global impedance target, the matching network composed of the matching circuit, the different-frequency power division circuit and the different-frequency synthesis circuit is optimized as a whole; Step 8, determine whether the matching network meets the standing wave coefficient in the entire frequency band. If so, proceed to the next step; if not, redesign the inter-frequency power division circuit and inter-frequency synthesis circuit and optimize them; Step 9: Add the antenna to the final matching network and perform simulation; Step 10: Determine whether the standing wave coefficient meets the requirements based on the simulation results. If it does, complete the design. If not, return to step 4.

10. The method for designing a broadband antenna matching structure according to claim 9, characterized in that: In step 6, a non-isolated T-type connector is first used for connection, and then the parameters of the connection circuit are adjusted according to the design goal, and finally the hetero-frequency power division circuit and the hetero-frequency synthesis circuit are obtained.

Images