Calibration Circuit, Calibration Network and Smart Antenna

Abstract

The present invention relates to a calibration circuit, a calibration network, and a smart antenna, including a power distribution network module and a plurality of directional couplers. Each branch port of the power distribution network module is electrically connected to one end of each directional coupler in one-to-one correspondence. The directional coupler includes a first coupling section and a second coupling section that are coupled to each other. The first coupling section is used to be electrically connected between the smart antenna port and the antenna array. One end of the second coupling section is electrically connected to the branch port of the power distribution network module, and the other end of the second coupling section is grounded. Wherein, the characteristic impedance of the first coupling section is less than that of the second coupling section, and the electrical length of the first coupling section is greater than that of the second coupling section. By transforming each directional coupler in the calibration circuit, an asymmetric directional coupler composed of two coupling sections with different characteristic impedances and different electrical lengths is formed, and a new calibration circuit is formed with the power distribution network module, greatly improving the miniaturization degree of the calibration network.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly to a calibration circuit, a calibration network, and a smart antenna. Background Art

[0002] With the development of mobile communication technologies, mobile communication has entered the 5G era. After the widespread commercial use of 5G, the coexistence of 4G and 5G networks will last for a relatively long time. The 4G network standards are mainly FDD (Frequency Division Duplexing) and TDD (Time Division Duplexing). The mobile 4G network is mainly of the TDD standard, and a large number of smart antennas are required for TDD standard communication coverage. Therefore, the application demand for these smart antennas will still remain at a relatively high level.

[0003] In a smart antenna, the calibration network is a core component of the smart antenna, which is used to collect the amplitude and phase signals of the unit antennas in the smart antenna to compensate for the amplitude and phase deviations generated when the base station processor is connected to the antenna. The calibration networks of traditional smart antennas mostly adopt a planar PCB (Printed Circuit Board) structure. However, in the process of implementing the present invention, the inventors found that the traditional calibration network has the problem of low miniaturization level. Summary of the Invention

[0004] Based on this, it is necessary to provide a calibration circuit, a calibration network, and a smart antenna that can significantly improve the miniaturization level of the calibration network in view of the problems existing in the traditional calibration network.

[0005] To achieve the above object, the embodiments of the present invention provide the following technical solutions:

[0006] On the one hand, a calibration circuit is provided, which includes a power distribution network module and a plurality of directional couplers. Each branch port of the power distribution network module is electrically connected to one end of each directional coupler in one-to-one correspondence;

[0007] The directional coupler includes a first coupling section and a second coupling section that are coupled together. The first coupling section is used to be electrically connected between the smart antenna port and the antenna array. One end of the second coupling section is electrically connected to the branch port of the power distribution network module, and the other end of the second coupling section is grounded;

[0008] Wherein, the characteristic impedance of the first coupling section is less than that of the second coupling section, and the electrical length of the first coupling section is greater than that of the second coupling section.

[0009] In one embodiment, the above calibration circuit further includes a grounding resistor, and the other end of the second coupling section is grounded through the grounding resistor.

[0010] In one embodiment, the characteristic impedance of the first coupling section is 50 ohms, and the grounding resistance is a 100-ohm resistor.

[0011] In one embodiment, the electrical length of the first coupling section is a general design length, and the electrical length of the second coupling section is equal to or less than one-fourth of the general design length.

[0012] In one embodiment, the power distribution network module includes a plurality of cascaded power dividers, and the branch port of the power divider at the end of the cascade is electrically connected to one end of the second coupling section.

[0013] In one embodiment, the power divider is a Wilkinson power divider.

[0014] In one embodiment, the above calibration circuit further includes a plurality of phase-shifting stub arrays, and each phase-shifting stub array is respectively arranged at the connection part between each branch port of the power distribution network module and one end of each corresponding second coupling section.

[0015] On the other hand, a calibration network is further provided, including a signal splitting circuit and the above calibration circuit, and the calibration port of the calibration circuit is electrically connected to the signal splitting circuit.

[0016] In one embodiment, the calibration circuit and the signal splitting circuit are arranged on one side of the circuit board.

[0017] On yet another aspect, an intelligent antenna is further provided, including the above calibration network.

[0018] One of the above technical solutions has the following advantages and beneficial effects:

[0019] For the above calibration circuit, calibration network and intelligent antenna, by transforming each directional coupler in the calibration circuit, an asymmetric directional coupler is composed of two coupling sections with different characteristic impedances (one large and one small) and different electrical lengths, and a new calibration circuit is formed with the power distribution network module. Since in the two coupling sections of the directional coupler, the second coupling section is a high-impedance coupling section and its electrical length is shortened, the strip width of the second coupling section can be effectively reduced, and the coupling gap width between the two coupling sections is greatly reduced, optimizing the layout and routing of the strip line, thereby greatly reducing the space occupied by the coupler, significantly saving the space on the antenna surface, making the structure of the calibration circuit more compact, and being able to greatly improve the miniaturization degree of the entire calibration network; moreover, the directional coupler with the above structure can reduce the generation of surface waves and has stronger anti-interference ability. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of a directional coupler used in a traditional calibration network;

[0021] Figure 2 is the first structural schematic diagram of the calibration circuit in an embodiment;

[0022] Figure 3 is the second structural schematic diagram of the calibration circuit in an embodiment;

[0023] Figure 4 is the third structural schematic diagram of the calibration circuit in an embodiment;

[0024] Figure 5 is the fourth structural schematic diagram of the calibration circuit in an embodiment;

[0025] Figure 6 is the circuit structural schematic diagram of the calibration network in an embodiment;

[0026] Figure 7 is the circuit structural schematic diagram of the calibration network in another embodiment. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] It should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific implementation manners and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0029] Such as Figure 1The structure diagram of the directional coupler used in the traditional calibration network is shown. It can be seen that the traditional directional coupler is composed of two coupling sections with the same electrical length and the same characteristic impedance, wherein P1 to P4 represent the ports of the directional coupler respectively, and S1 represents the coupling gap width of the directional coupler. Generally, the two coupling sections of the traditional directional coupler are coupling sections with an electrical length of one-quarter wavelength, and in some applications, the coupling sections are also processed into non-linear coupling sections, such as sawtooth coupling sections, cross-finger linear coupling sections or wavy coupling sections, so as to increase the coupling electrical length of the directional coupler, so as to reduce the phase velocity imbalance caused by the mixed medium of the microstrip line, increase the directivity of the directional coupler, reduce the influence of the energy feedback at the antenna end on the coupling degree of the calibration network, and thus improve the directivity of the calibration network, as well as the amplitude and phase anti-interference; the traditional directional coupler reasonably utilizes the strip line layout of the power distribution network module to achieve a certain degree of compact structure and miniaturization design effect. However, with the continuous development of technology in the field and the improvement of application requirements, the defect of the low degree of miniaturization of the traditional calibration network has become increasingly prominent. To this end, the present application provides the following technical solutions:

[0030] See also Figure 2 In one embodiment, a calibration circuit 100 is provided, comprising a power distribution network module 12 and a plurality of directional couplers 14. Each branch port of the power distribution network module 12 is electrically connected to one end of each directional coupler 14 in a one-to-one correspondence. The directional coupler 14 comprises a first coupling section 142 and a second coupling section 144 coupled to each other. The first coupling section 142 is used to electrically connect between the smart antenna port and the antenna array. One end of the second coupling section 144 is electrically connected to the branch port of the power distribution network module 12, and the other end of the second coupling section 144 is grounded. The characteristic impedance of the first coupling section 142 is less than the characteristic impedance of the second coupling section 144, and the electrical length of the first coupling section 142 is greater than the electrical length of the second coupling section 144.

[0031] It can be understood that the power distribution network module 12 is a power distribution circuit that divides one input signal power into two or more output signal powers. The power distribution network module 12 can also combine two or more output signal powers into one input signal power. The power distribution network module 12 can be composed of a power divider in the art. The power distribution network module 12 includes a merging port and a plurality of branch ports. The merging port of the power distribution network module 12 is used to electrically connect the signal shunt circuit in the calibration network. The power distribution network module 12 cooperates with each directional coupler 14 to realize the calibration function of the smart antenna.

[0032] The directional coupler 14 is a device capable of coupling signals, and can couple the signals transmitted by the smart antenna port and output them to the power distribution network module 12. The first coupling section 142 can adopt the coupling section of the traditional directional coupler in the art, while the second coupling section 144 adopts a coupling section with a characteristic impedance higher than that of the first coupling section 142 and a shortened electrical length, so that an asymmetric coupling structure is formed after the first coupling section 142 and the second coupling section 144 are coupled together. The strip width of the second coupling section 144 is reduced, and the coupling gap between the first coupling section 142 and the second coupling section 144 can also be reduced. Finally, the strip width of the directional coupler 14 is effectively reduced, which is beneficial to reducing the area of the calibration network required for application.

[0033] The electrical connection manner between any directional coupler 14 and the smart antenna port and the antenna array can be understood by analogy with the electrical connection manner between the traditional directional coupler and the smart antenna port and the antenna array in the art, and will not be described in detail in this specification. Similarly, the electrical connection manner between the power distribution network module 12 and the signal shunt circuit can also be understood by analogy with the electrical connection manner between the traditional power distribution network module 12 and the signal shunt circuit in the art. The smart antenna port can be used to transmit the radio frequency signals transmitted by the base station processor. The antenna array is a device capable of effectively radiating or receiving radio waves in the art. The antenna array can include 1 oscillator or multiple oscillators, and can be specifically determined by the design requirements of the smart antenna in actual application.

[0034] Specifically, in actual application, the base station processor accesses the calibration circuit 100 through the smart antenna port, and sends radio frequency signals to the first coupling section 142 of the directional coupler 14. The radio frequency signals are transmitted to the antenna array through the first coupling section 142 for transmission. During the process of transmitting the radio frequency signals to the antenna array by the first coupling section 142, based on the coupling effect between the first coupling section 142 and the second coupling section 144, part of the radio frequency signals are coupled and transmitted to the power distribution network module 12 for calibrating the smart antenna. Since each directional coupler 14 is a coupler with an asymmetric coupling structure, during the process of transmitting the radio frequency signals, the directional coupler 14 can reduce the generation of surface waves, making the anti-interference performance of the calibration circuit 100 stronger.

[0035] The above calibration circuit 100 is formed by transforming each directional coupler 14 in the calibration circuit. The asymmetric directional coupler 14 is composed of two coupling sections with different characteristic impedances (one large and one small) and different electrical lengths, and forms a new calibration circuit with the power distribution network module 12. Since in the two coupling sections of the directional coupler 14, the second coupling section 144 is a high-impedance coupling section and its electrical length is shortened, the strip line width of the second coupling section 144 can be effectively reduced, and the coupling gap width between the two coupling sections is greatly reduced, optimizing the layout and routing of the strip line. As a result, the space occupied by the coupler is greatly reduced, significantly saving the roof space, making the structure of the calibration circuit 100 more compact, and greatly improving the miniaturization degree of the entire calibration network. Moreover, the directional coupler 14 with the above structure can reduce the generation of surface waves and has stronger anti-interference ability.

[0036] Please refer to Figure 3 , in one embodiment, the above calibration circuit 100 further includes a grounding resistor 16. The other end of the second coupling section 144 is grounded through the grounding resistor 16.

[0037] It can be understood that the second coupling section 144 can achieve high impedance by terminating with a grounding resistor 16. The resistance value of the grounding resistor 16 can be determined according to the characteristic impedance of the first coupling section 142, as long as the characteristic impedance of the second coupling section 144 can be made higher than that of the first coupling section 142 to achieve the required coupling effect. For example, but not limited to, if the first coupling section 142 adopts a traditional coupling section design with a 50-ohm match, the characteristic impedance of the second coupling section 144 can be selected to be greater than 50 ohms. By selecting a grounding resistor 16 with a resistance value greater than 50 ohms and terminating it with the second coupling section 144, the characteristic impedance of the second coupling section 144 can be made higher than that of the first coupling section 142.

[0038] By terminating the second coupling section 144 with the grounding resistor 16, the effect of reducing the strip line width can be achieved in the way of terminating with a high impedance, and the coupling effect of the directional coupler 14 can be effectively improved.

[0039] In one embodiment, the characteristic impedance of the first coupling section 142 is 50 ohms, and the grounding resistor 16 is a 100-ohm resistor. It can be understood that in this embodiment, the first coupling section 142 adopts a typical coupling section design in the art, that is, a 50-ohm match, which is convenient for impedance matching with the antenna array. Correspondingly, by using a resistor with a typical value of 100 ohms for the grounding resistor 16, the electrical length of the second coupling section 144 can be made much smaller than that of the first coupling section 142, which is convenient for the layout and routing of the strip line, while reducing the inter-line coupling gap and reducing the generation of surface waves, with stronger anti-interference ability, and can better achieve the impedance matching of the entire calibration circuit.

[0040] In one embodiment, the electrical length of the first coupling section 142 is a general design length, and the electrical length of the second coupling section 144 is equal to or less than one - quarter of the general design length.

[0041] It can be understood that the general design length refers to the typical electrical length adopted by the directional coupler 14 in a traditional calibration network. It can be one value, or two or more values. For example, for the directional coupler 14 with a characteristic impedance of 50 ohms mentioned above, the electrical lengths of its two coupling sections are both one - quarter wavelength. Thus, the general design length can be one - quarter wavelength.

[0042] In this way, the electrical length of the second coupling section 144 can be equal to one - quarter of the general design length or shorter, for example, it can be one - sixteenth wavelength or shorter. As the characteristic impedance of the second coupling section 144 of the directional coupler 14 increases and the electrical length decreases, the strip - line width of the second coupling section 144 can become smaller. Therefore, the coupling gap formed when coupled to the first coupling section 142 can be adjusted to be smaller. Taking the electrical length of the first coupling section 142 as one - quarter wavelength and the electrical length of the second coupling section 144 as one - sixteenth wavelength as an example, if the two coupling sections of a traditional directional coupler are symmetric and the coupling gap width is S1, then the coupling gap width S of the directional coupler 14 after the adjusted design in this embodiment can be reduced to three - tenths of S1, greatly reducing the line width of the coupling section, thereby more effectively reducing the space occupied by the directional coupler 14 and improving the miniaturization degree of the calibration circuit.

[0043] Please refer to Figure 4 , in one embodiment, the power distribution network module 12 includes a plurality of cascaded power dividers 122. The branch port of the power divider 122 at the end of the cascade is electrically connected to one end of the second coupling section 144.

[0044] It can be understood that each power divider 122 can include a combining port and two or more branch ports. The power divider 122 at the end of the cascade refers to the last - stage power divider 122 in the cascade; the last - stage in the cascade includes at least four power dividers 122. Opposite to the end of the cascade is the beginning of the cascade. The beginning of the cascade refers to the first - stage power divider 122 in the cascade, and the beginning of the cascade includes one power divider 122. The power divider 122 can be a three - port power splitter or bridge in the art, or a power splitter or bridge with more than three ports, which can be specifically determined according to actual application requirements.

[0045] Specifically, the branch port of the power divider 122 at the end of the cascade is connected to one end of the second section; the combining port of the power divider 122 at the beginning of the cascade is connected to the signal splitting circuit. For example, as Figure 4As shown, in this embodiment, the number of directional couplers 14 is 8, and the power distribution network module 12 is formed by cascading 7 power dividers 122. Among them, the cascaded end of the power distribution network module 12 includes 4 power dividers 122, and the branch ports of the 4 power dividers 122 are respectively and correspondingly connected to one end of the second coupling section 144 of each directional coupler 14.

[0046] It should be noted that in other application examples, other combinations of the number of directional couplers 14 and power dividers 122 can also be used as long as the required calibration function and miniaturization requirements can be effectively achieved, and no further detailed discussion will be carried out here. Through the combined design of the cascaded power dividers 122 and each directional coupler 14, the calibration function of the smart antenna can be effectively supported, and at the same time, the calibration performance can also be effectively improved.

[0047] In one embodiment, as Figure 4 shown, the power divider 122 is a Wilkinson power divider. It can be understood that in this embodiment, the commonly used Wilkinson power divider in the art is used for cascaded application. Taking the two-way Wilkinson power divider as an example, seven two-way Wilkinson power dividers are cascaded to form an eight-way Wilkinson power distribution network structure, and one end of the second coupling section 144 of each directional coupler 14 is respectively electrically connected to the branch port of the Wilkinson power divider at the cascaded final stage.

[0048] The Wilkinson power divider includes an input strip line 1222, a differential impedance transformation section 1224, an isolation resistor 1226, and an output strip line 1228. The output strip line 1228 of the previous-level Wilkinson power divider is connected to the input strip line 1222 of the next-level Wilkinson power divider, and is cascaded in sequence to form an eight-way Wilkinson power distribution network. The end of the eight-way Wilkinson power distribution network is connected to one end of the second coupling section 144 of the directional coupler 14, and the other end of the second coupling section 144 is electrically connected to the grounding resistor 16 to complete the matching of the entire calibration circuit.

[0049] Through the cascading of the above Wilkinson power dividers and the combined application of each directional coupler 14, the circuit structure of the calibration circuit 100 can be simplified, and the amplitude-phase anti-interference performance can be improved.

[0050] Please refer to Figure 5 , in one embodiment, the above calibration circuit 100 further includes a plurality of phase adjustment stub arrays 18. Each phase adjustment stub array 182 is respectively arranged at the connection part between each branch port of the power distribution network module 12 and one end of each corresponding second coupling section 144.

[0051] It can be understood that the phase modulation stub array 182 is a stub array composed of commonly used phase modulation stubs in the art, which may include multiple phase modulation stubs, and the specific number can be determined according to the required phase modulation effect. Each phase modulation stub can be a microstrip line structure. At the connection part between any branch port and one end of the second coupling section 144, the ends of the phase modulation stubs in the phase modulation stub array 182 are connected to the connection part, and the phase modulation stubs can be evenly distributed on the same side of the connection part, or can be divided into two parts and evenly distributed on both sides of the connection part respectively.

[0052] Specifically, taking the above-mentioned Wilkinson power divider as an example, in this embodiment, the calibration circuit 100 can be formed by networking seven Wilkinson power dividers, eight directional couplers 14 and eight phase modulation stub arrays 182. The phase modulation stub array 182 is arranged on the connection part between the branch port of the power distribution network module 12 and one end of the directional coupler 14, so that the phase error caused by welding and cable cutting can be adjusted during actual production, the phase adjustment of each signal channel of the calibration circuit 100 can be realized, and the calibration effect can be further improved.

[0053] In one embodiment, the phase modulation stub array 182 includes a first phase modulation stub, a second phase modulation stub, a third phase modulation stub and a fourth phase modulation stub. The ends of the first phase modulation stub and the second phase modulation stub are respectively electrically connected to one side of the connection part; the ends of the third phase modulation stub and the fourth phase modulation stub are respectively electrically connected to the other side of the connection part. Among them, the first phase modulation stub, the second phase modulation stub, the third phase modulation stub and the fourth phase modulation stub are respectively microstrip line structures. The first phase modulation stub and the second phase modulation stub can be symmetrically arranged based on the connection part; the third phase modulation stub and the fourth phase modulation stub can be symmetrically arranged based on the connection part. In another application scenario, the first phase modulation stub, the second phase modulation stub, the third phase modulation stub and the fourth phase modulation stub can also be evenly distributed on the same side of the connection part, as long as the required phase modulation function can be realized.

[0054] In this embodiment, by arranging the phase modulation stub array 182 (including the first phase modulation stub, the second phase modulation stub, the third phase modulation stub and the fourth phase modulation stub) on the connection part between the branch port of the power distribution network module 12 and one end of the directional coupler 14, the phase of each signal channel of the calibration circuit 100 in this solution is adjusted, and the calibration effect is improved.

[0055] Please refer to Figure 6 , in one embodiment, a calibration network 200 is further provided, which includes a signal splitting circuit 21 and the above-mentioned calibration circuit 100. The calibration port of the calibration circuit 100 is electrically connected to the signal splitting circuit 21.

[0056] It can be understood that the signal splitting circuit 21 is a splitting unit for radio frequency signals and RCU (Remote Control Unit) control signals, and can be a signal splitting circuit 21 existing in the art. The electrical connection manner between the signal splitting circuit 21 and the calibration port of the calibration circuit can be understood by analogy with the circuit connection manner between the traditional signal splitting circuit 21 and the power distribution network module 12, and will not be elaborated here one by one.

[0057] Regarding the specific explanation of the calibration circuit 100 in this embodiment, it can be understood by analogy with the corresponding explanations in the specific embodiments of the above calibration circuits 100, and will not be elaborated one by one in this embodiment and the subsequent embodiments.

[0058] Specifically, the signal splitting circuit 21 may include an AC coupling capacitor 212, a high-impedance transmission line 214, a low-impedance transmission line 216, a bypass filter capacitor 218, and a gas discharge tube 219. The AC coupling capacitor 212 is disposed between the calibration port of the calibration circuit and the high-impedance transmission line 214, and is used to isolate the DC RCU control signal entering from the calibration port, so that the AC radio frequency signal can pass through. The high-impedance transmission line 214 and the low-impedance transmission line 216 are connected in series, and the electrical lengths of both the high-impedance transmission line 214 and the low-impedance transmission line 216 are about one-quarter wavelength. The bypass filter capacitor 218 and the gas discharge tube 219 are disposed on the low-impedance transmission line 216 and are connected to the metal ground 23 to form a complete filter circuit, which is used to filter out the high-frequency AC signals mixed in the DC RCU control signal.

[0059] After the radio frequency signal and the RCU control signal entering from the same calibration port enter the signal splitting circuit 21, the signal splitting circuit 21 separates these two signals from each other, so that the radio frequency signal is transmitted to the calibration circuit 100, while the RCU control signal is transmitted to the RCU control circuit, and the two signals do not interfere with each other. In some application examples, the number of AC coupling capacitors 2121 connected in the signal splitting circuit 21 can be but is not limited to 1, the number of bypass filter capacitors 218 connected can be more than two, and the number of gas discharge tubes 219 connected can be 1, which is used to provide the lightning protection function required by the calibration network and protect the backend circuit system.

[0060] The above calibration network 200, by combining and applying the above calibration circuit 100 and signal splitting circuit 21, can effectively optimize the layout and routing of each transmission line in the network, thereby greatly reducing the space occupied by the couplers in the network, significantly saving the rooftop space, making the structure of the calibration network 200 more compact, and capable of greatly improving the miniaturization degree of the entire calibration network 100; moreover, the directional coupler 14 with the above structure can reduce the generation of surface waves, has stronger anti-interference ability, higher calibration performance, and lower manufacturing cost.

[0061] Please refer to Figure 7, in one embodiment, the calibration circuit 100 and the signal shunt circuit 21 are disposed on one surface of the circuit board 30.

[0062] It can be understood that the circuit board can be a ceramic circuit board, an aluminum-based circuit board, a PCB (Printed Circuit Board) board, etc. Taking the circuit board as a PCB board as an example, specifically, the calibration circuit 100 and the signal shunt circuit 21 can be integrally integrated on the same surface of the PCB board, so that the calibration network 100 is more integrated, the overall structure is more compact and the manufacturing cost can be reduced, achieving the effect of further improving the miniaturization degree.

[0063] In one embodiment, there is also provided an intelligent antenna including the above-mentioned calibration network 200.

[0064] It can be understood that for the specific explanations of the calibration network 200 in this embodiment, reference can be made to the corresponding explanations in the specific embodiments of the above calibration networks 200 for the same understanding, and details will not be elaborated here. It should be noted that those skilled in the art can understand that the intelligent antenna may further include other components, such as, but not limited to, an antenna array, which can be specifically determined according to the composition structure of the intelligent antenna in actual applications.

[0065] By applying the above-mentioned calibration network 200, the above intelligent antenna can effectively achieve the miniaturized design of the entire antenna and reduce the manufacturing cost. Based on the structural optimization design of the above calibration network 200, the amplitude-phase consistency of the intelligent antenna can also be effectively improved.

[0066] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0067] The above embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A calibration circuit, characterized in that, it includes a power distribution network module and a plurality of directional couplers, and each branch port of the power distribution network module is electrically connected to one end of each of the directional couplers in one-to-one correspondence; the directional coupler includes a first coupling section and a second coupling section that are coupled together, the first coupling section is used for electrical connection between the smart antenna port and the antenna array, one end of the second coupling section is electrically connected to the branch port of the power distribution network module, and the other end of the second coupling section is grounded; wherein, the characteristic impedance of the first coupling section is less than that of the second coupling section, and the electrical length of the first coupling section is greater than that of the second coupling section; the calibration circuit further includes a grounding resistor, and the other end of the second coupling section is grounded through the grounding resistor.

2. The calibration circuit according to claim 1, characterized in that, the characteristic impedance of the first coupling section is 50 ohms, and the grounding resistor is a 100-ohm resistor.

3. The calibration circuit according to any one of claims 1 to 2, characterized in that, the electrical length of the first coupling section is a general design length, and the electrical length of the second coupling section is equal to or less than one-fourth of the general design length.

4. The calibration circuit according to claim 3, characterized in that, the power distribution network module includes a plurality of cascaded power dividers, and the branch port of the power divider at the cascaded end is electrically connected to one end of the second coupling section.

5. The calibration circuit according to claim 4, characterized in that, the power divider is a Wilkinson power divider.

6. The calibration circuit according to claim 1, characterized in that, it further includes a plurality of phase adjustment stub arrays, and each of the phase adjustment stub arrays is respectively arranged at the connection part between each branch port of the power distribution network module and one end of each corresponding second coupling section.

7. A calibration network, characterized in that, it includes a signal splitting circuit and the calibration circuit according to any one of claims 1 to 6, and the calibration port of the calibration circuit is electrically connected to the signal splitting circuit.

8. The calibration network according to claim 7, characterized in that, the calibration circuit and the signal splitting circuit are arranged on one side of the circuit board.

9. A smart antenna, characterized in that, it includes the calibration network according to claim 7 or 8.

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