CN117438768A - Multistage coupler, calibration device and base station antenna - Google Patents

Abstract

The present disclosure relates to a multistage coupler, comprising: a first coupler, comprising: a first primary transmission line electrically connected in series between an input port and an output port of the first coupler; a first secondary transmission line electrically connected in series between the coupling port and the isolation port of the first coupler; and a second coupler comprising: a second primary transmission line electrically connected in series between an input port and an output port of the second coupler; and a second secondary transmission line electrically connected in series between the coupling port and the isolation port of the second coupler, the coupling port of the first coupler and the input port of the second coupler being electrically connected to each other. In addition, the present disclosure also relates to a calibration device for a base station antenna and a related base station antenna.

Description

Multistage coupler, calibration device and base station antenna

Technical Field

The present disclosure relates to communication systems, and more particularly, to a multi-stage coupler, a calibration device, and a base station antenna.

Background

Couplers are widely used in microwave systems. The coupler may be configured as a power splitting device for splitting a radio frequency signal into multiple radio frequency signals having a predetermined amplitude and phase. The coupler may generally include four ports, i.e., an input port, an output port, a coupled port, and an isolated port. When a radio frequency signal is input from the input port with a predetermined input power, a predetermined proportion of the output power can be generated at the output port, a predetermined proportion of the coupling power can be generated at the coupling port, and no power output is required at the isolation port in an ideal coupler. In practice, however, there will always be some power leakage at the isolated ports. It will be appreciated that according to the principle of reciprocity, when a radio frequency signal is input from the "output port", the "output port" is then converted into an input port of the coupler, the "input port" is converted into an output port of the coupler, the "isolation port" is converted into a coupling port of the coupler, and the "coupling port" is converted into an isolation port of the coupler.

The coupler may have indicators of coupling, isolation, and directivity. Let a signal of power P1 be input at the input port, output power P2 at the output port, coupled power P3 at the coupled port, and leakage power P4 at the isolated port.

The "coupling degree" of the coupler can be expressed as the ratio of the coupling power P3 to the input power P1. The coupling degree of a coupler is typically expressed in dB and is typically negative. The larger the absolute value of the degree of coupling (the degree of coupling referred to below is understood to be the absolute value of the degree of coupling), the smaller the amount of power output via the coupling port.

The "isolation" of the coupler may be expressed as the ratio of leakage power P4 to input power P1. The isolation of the coupler is typically expressed in dB and is typically negative. The greater the absolute value of isolation (isolation, referred to below, is to be understood as the absolute value of isolation), the less the amount of power that is output via the isolated port leakage, and thus the less the energy loss of the coupler.

The "directivity" of the coupler may be expressed as the ratio of the coupled power P3 to the leakage power P4. Directivity is a measure of the ability of a coupler to discriminate between incident and reflected waves or quality factor. The following relationship may exist between the coupling degree, isolation degree, and directivity of the coupler: isolation = coupling + directivity. The degree of coupling and the directivity may be set according to the use requirement, and thus the desired value of the degree of isolation may be calculated according to the degree of coupling and the directivity. For example, coupling = 30dB, directivity = 25dB, then desired isolation = 30db+25db = 55dB.

In some application scenarios, there are strict requirements on the coupling degree of the coupler. For example, the coupling level needs to be higher than 35dB, 40dB or 43dB. The higher coupling degree not only can effectively improve the energy utilization rate, but also can effectively reduce the load of the radio frequency device at the downstream of the coupling port of the coupler. In addition, there may be stringent requirements on the directivity and/or isolation of the coupler. However, some known couplers are not satisfactory in terms of coupling, directivity, and/or isolation.

Disclosure of Invention

It is an object of the present disclosure to provide a multistage coupler, calibration device and base station antenna that overcome at least one of the drawbacks of the prior art.

According to a first aspect of the present disclosure, there is provided a multistage coupler comprising:

a first coupler, comprising: a first primary transmission line electrically connected in series between an input port and an output port of the first coupler; a first secondary transmission line electrically connected in series between the coupling port and the isolation port of the first coupler; and

a second coupler, comprising: a second primary transmission line electrically connected in series between an input port and an output port of the second coupler; and a second secondary transmission line electrically connected in series between the coupling port and the isolation port of the second coupler, wherein the coupling port of the first coupler and the input port of the second coupler are electrically connected to each other.

According to a second aspect of the present disclosure, there is provided a calibration device for a base station antenna, characterized in that the calibration device comprises:

a dielectric substrate;

calibration circuitry printed on a dielectric substrate, the calibration circuitry including a multi-stage coupler, a power combiner, and a calibration port according to some embodiments of the present disclosure.

According to a third aspect of the present disclosure, there is provided a base station antenna comprising:

a reflection plate;

a feeding plate disposed at a front side of the reflecting plate and a radiating element array mounted on the feeding plate;

a multistage coupler according to some embodiments of the present disclosure or a calibration device according to some embodiments of the present disclosure disposed on a rear side of the reflective plate.

Other features of the present disclosure and its advantages will become apparent from the following detailed description of exemplary embodiments of the disclosure, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure.

Fig. 1 is an exemplary plan layout of a multistage coupler according to some embodiments of the present disclosure.

Fig. 2A, 2B, 2C are exemplary variations of the multi-stage coupler of fig. 1 according to further embodiments of the present disclosure.

Fig. 3A, 3B, 3C, 3D are exemplary variants of coupling knuckles of a multi-stage coupler according to some embodiments of the present disclosure.

Fig. 4 is an exemplary variation of a multistage coupler according to further embodiments of the present disclosure.

Fig. 5 is a simplified schematic diagram of a base station antenna according to some embodiments of the present disclosure.

Fig. 6 is a schematic diagram of a calibration device in the base station antenna of fig. 5.

Note that in the embodiments described below, the same reference numerals are used in common between different drawings to denote the same parts or parts having the same functions, and a repetitive description thereof may be omitted. In some cases, like numbers and letters are used to designate like items, and thus once an item is defined in one drawing, no further discussion thereof is necessary in subsequent drawings.

For ease of understanding, the positions, dimensions, ranges, etc. of the respective structures shown in the drawings and the like may not represent actual positions, dimensions, ranges, etc. Accordingly, the present disclosure is not limited to the disclosed positions, dimensions, ranges, etc. as illustrated in the accompanying drawings.

Detailed Description

The present disclosure will be described below with reference to the accompanying drawings, which illustrate several embodiments of the present disclosure. It should be understood, however, that the present disclosure may be presented in many different ways and is not limited to the embodiments described below; indeed, the embodiments described below are intended to more fully convey the disclosure to those skilled in the art and to fully convey the scope of the disclosure. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide yet additional embodiments.

It should be understood that the terminology herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present disclosure. All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. Well-known functions or constructions may not be described in detail for brevity and/or clarity.

In this document, an element may be referred to as being "on," "attached" to, "connected" to, "coupled" to, "contacting" or the like another element, directly on, attached to, connected to, coupled to or contacting the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly on," "directly attached to," directly connected to, "directly coupled to," or "directly contacting" another element, there are no intervening elements present. In this context, one feature is disposed "adjacent" another feature, which may refer to a feature having a portion that overlaps or is located above or below the adjacent feature.

In this document, reference may be made to elements or nodes or features being "connected" together. Unless specifically stated otherwise, "connected" means that one element/node/feature may be mechanically, electrically, logically, or otherwise joined with another element/node/feature in a direct or indirect manner to allow interactions even though the two features may not be directly connected. That is, "connected" is intended to encompass both direct and indirect connection of elements or other features, including connection with one or more intermediate elements.

In this document, spatially relative terms such as "upper," "lower," "left," "right," "front," "rear," "high," "low," and the like may be used to describe one feature's relationship to another feature in the figures. It will be understood that the spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, when the device in the figures is inverted, features that were originally described as "below" other features may be described as "above" the other features. The device may also be otherwise oriented (rotated 90 degrees or at other orientations) and the relative spatial relationship will be explained accordingly.

In this document, the term "a or B" includes "a and B" and "a or B", and does not include exclusively only "a" or only "B", unless otherwise specifically indicated.

In this document, the term "exemplary" means "serving as an example, instance, or illustration," rather than as a "model" to be replicated accurately. Any implementation described herein by way of example is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, this disclosure is not limited by any expressed or implied theory presented in the preceding technical field, background, brief summary or the detailed description.

As used herein, the term "substantially" is intended to encompass any minor variation due to design or manufacturing imperfections, tolerances of the device or element, environmental effects and/or other factors. The term "substantially" also allows for differences from perfect or ideal situations due to parasitics, noise, and other practical considerations that may be present in a practical implementation.

In addition, for reference purposes only, the terms "first," "second," and the like may also be used herein, and are thus not intended to be limiting. For example, the terms "first," "second," and other such numerical terms referring to structures or elements do not imply a sequence or order unless clearly indicated by the context.

It will be further understood that the terms "comprises" and/or "comprising," when used herein, specify the presence of stated features, steps, operations, units, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, units, and/or components, and/or groups thereof.

The present disclosure relates to a multistage coupler for a base station antenna. The multi-stage coupler may include at least two cascaded couplers (each coupler may be configured as a four-port element, for example) to achieve high coupling (i.e., high absolute value of coupling) and/or high isolation (i.e., high absolute value of isolation) of the multi-stage coupler. The higher the degree of coupling, the less the amount of power output via the coupling port. The reduction of the power output via the coupling port not only can effectively increase the energy utilization rate, but also can effectively reduce the load of the radio frequency device downstream of the coupling port of the multistage coupler. In addition, higher isolation indicates higher energy utilization and less energy loss of the coupler.

In some embodiments, the coupling degree of the multi-stage coupler of the present disclosure may be higher than 30dB, 36dB, 40dB, 43dB, or 50dB. The directivity of the multistage coupler of the present disclosure may be higher than 10dB, 13dB, 15dB, 20dB. The isolation of the multi-stage coupler of the present disclosure may be higher than 40dB, 50dB, 55dB, or 60dB.

Aspects in accordance with the present disclosure will now be described in detail with reference to the accompanying drawings.

Fig. 1, 2A-2C are exemplary plan layout diagrams of a multi-stage coupler 10 according to some embodiments of the present disclosure.

As shown in fig. 1, the multi-stage coupler 10 may include a first coupler 20 and a second coupler 30 electrically coupled to the first coupler 20. The first coupler 20 may include: a first primary transmission line 21 (which may also be referred to as a first straight line), the first primary transmission line 21 being electrically connected in series between the input port p_in and the output port p_out of the first coupler 20; a first secondary transmission line 22 (which may also be referred to as a first coupled line), the first secondary transmission line 22 being electrically connected in series between the coupling port p_couple and the isolation port p_iso of the first coupler 20. The second coupler 30 may include: a second primary transmission line 31 (which may also be referred to as a second through line), the second primary transmission line 31 being electrically connected in series between the input port p_in and the output port p_out of the second coupler 30; a second secondary transmission line 32 (which may also be referred to as a second coupled line), the second secondary transmission line 32 being electrically connected in series between the coupling port p_couple and the isolation port p_iso of the second coupler 30. It should be understood that the input port p_in/output port p_out and the coupling port p_coupling/isolation port p_iso of each coupler may be adjusted according to the actual transmission direction of the radio frequency signal.

To achieve electrical coupling between the first coupler 20 and the second coupler 30, the coupling port p_coupling of the first coupler 20 and the input port p_in of the second coupler 30 may be electrically connected to each other. In the illustrated embodiment, the first secondary transmission line 22 may continuously transition to the second primary transmission line 31. That is, the first secondary transmission line 22 may be an integral radio frequency transmission line with the second primary transmission line 31. The input port p_in of the second coupler 30 may receive the coupling power from the coupling port p_coupling of the first coupler 20 to further distribute the input coupling power, thereby achieving a high coupling ratio of the multistage coupler 10.

In some embodiments, as shown in fig. 1, 2A and 2B, the input port p_in of the first coupler 20 may be configured as the radio frequency signal input port 81 of the multi-stage coupler 10, the output port p_out of the first coupler 20 may be configured as the radio frequency signal output port 82 of the multi-stage coupler 10, and the isolation port p_iso of the second coupler 30 may be configured as the radio frequency signal coupling port 83 of the multi-stage coupler 10. Therefore, the equivalent coupling degree of the multistage coupler 10 may be equivalent to the sum of the coupling degree of the first coupler 20 and the isolation degree of the second coupler 30. Since the isolation of the second coupler 30 is higher than the coupling of the second coupler 30, a high coupling degree of the multistage coupler 10 can be achieved. It should be understood that other ports of each coupler may be connected to termination impedance.

In other embodiments, as shown in fig. 2C, the coupling port p_coupling of the second coupler 30 may be configured as the radio frequency signal coupling port 83 of the multi-stage coupler 10. Therefore, the equivalent coupling degree of the multistage coupler 10 may be equivalent to the sum of the coupling degree of the first coupler 20 and the coupling degree of the second coupler 30.

Referring to fig. 1, 2A, 2B and 2C, a coupling stub 50 may be provided between the secondary transmission line 22, 32 and the respective primary transmission line 21, 31 for tuning the coupling characteristics between the secondary transmission line 22, 32 and the respective primary transmission line 21, 31.

In some embodiments, the multi-stage coupler 10 may be implemented on a printed circuit board onto which the individual couplers may be printed as metal patterns.

In other embodiments, the multi-stage coupler 10 may also be implemented on multiple printed circuit boards, with the first coupler 20 being printed on a first printed circuit board and the second coupler 30 being printed on a second printed circuit board, the electrical connection between the first coupler 20 and the second coupler 30 being implemented by some means known in the art, such as a coaxial connector.

In some embodiments, referring to fig. 1, 2A and 2C, the first coupler 20 and the second coupler 30 may be configured identical to each other. The primary transmission lines of the couplers may each be configured as a linear primary transmission line. The secondary transmission lines of the couplers may each be configured as a nonlinear secondary transmission line, for example comprising one or more bending sections. In other embodiments, the first coupler 20 and the second coupler 30 may be configured differently from each other. It should be appreciated that the first coupler 20 and the second coupler 30 may differ in a wide variety of ways. Referring to fig. 2B, the primary transmission lines 21 of the first couplers 20 may be respectively configured as nonlinear primary transmission lines, and the primary transmission lines 31 of the second couplers 30 may be respectively configured as linear primary transmission lines. In other embodiments, the coupling stub 50 of the first coupler 20 may be different from the coupling stub 50 of the second coupler 30. In other embodiments, the primary and/or secondary transmission line routing of the first coupler 20 may be distinguished from the second coupler 30.

In some embodiments, referring to fig. 3A, a nonlinear secondary transmission line may include a first coupling section 41 reactively coupled to a first portion of a corresponding primary transmission line, a second coupling section 42 reactively coupled to a second portion of the corresponding primary transmission line, and an intermediate section 43 electrically coupled in series between the first coupling section 41 and the second coupling section 42.

The intermediate section 43 of the secondary transmission line 22, 32 may be closer to the respective primary transmission line 21, 31 relative to the first coupling section 41 and the second coupling section 42. In other embodiments, the intermediate section 43 of the secondary transmission line 22, 32 may be further from the respective primary transmission line relative to the first coupling section 41 and the second coupling section 42.

The coupling stub 50 may be configured to tune the coupling characteristics between the secondary transmission lines 22, 32 and the respective primary transmission lines 21, 31. In some embodiments, the coupling knuckle 50 may be integrally formed with the secondary transmission line 22, 32, such as on the intermediate section 43 thereof.

Additionally or alternatively, other forms of coupling mechanisms, such as coupling slots, coupling holes, etc., may be provided between the secondary transmission lines 21, 31 and the primary transmission lines 22, 32 to couple a portion of the radio frequency power of the primary transmission lines into the secondary transmission lines. It is desirable that the radio frequency power coupled into the secondary transmission line 21, 31 is transferred in the secondary transmission line 21, 31 as far as possible towards the coupling port p_couple without leaking from the isolation port p_iso.

It should be understood that the embodiments of coupling knuckle 50 may be varied and are not limited to the examples listed in this disclosure. Referring to fig. 3A, 3B, 3C, 3D, some exemplary variations of coupling knuckle 50 are shown, respectively.

In some embodiments, referring to fig. 3A, 3B, 3C, 3D, the second coupling section 42 may be closer to the respective primary transmission line 21, 31 relative to the first coupling section 41 such that there is an asymmetry in reactive coupling between the first and second portions of the respective primary transmission line 21, 31 and the nonlinear secondary transmission line 22, 32. This asymmetry in reactive coupling can produce continuously changing even and odd mode speeds during operation, thereby increasing the directivity of the coupler. Advantageously, the degree of reactive coupling between the second coupling section 42 and the primary transmission line 21, 31 is greater than the degree of reactive coupling between the first coupling section 41 and the primary transmission line 21, 31.

Referring to fig. 4, an exemplary variation of the multi-stage coupler 10 according to further embodiments of the present disclosure. As shown in fig. 4, the multi-stage coupler 10 may include three cascaded couplers, and the third coupler 60 of the multi-stage coupler 10 may include: a third primary transmission line 61, the third primary transmission line 61 being electrically connected in series between an input port p_in and an output port p_out of the third coupler 60; a third secondary transmission line 62, said third secondary transmission line 62 being electrically connected in series between the coupling port p_coupling and the isolation port p_iso of the third coupler 60.

To achieve electrical coupling between the first coupler 20, the second coupler 30, and the third coupler 60, the coupling port p_coupling of the first coupler 20 may be electrically connected to the input port p_in of the second coupler 30, and the coupling port p_coupling or the isolation port p_iso of the second coupler 30 may be electrically connected to the input port p_in of the third coupler 60. In the illustrated embodiment, the first secondary transmission line 22 may continuously transition to the second primary transmission line 31 and the second secondary transmission line 32 may continuously transition to the third primary transmission line 61.

In some embodiments, as shown in fig. 4, the input port p_in of the first coupler 20 may be configured as the radio frequency signal input port 81 of the multi-stage coupler 10, the output port p_out of the first coupler 20 may be configured as the radio frequency signal output port 82 of the multi-stage coupler 10, and the isolation port p_iso or the coupling port p_coupling of the third coupler 60 may be configured as the radio frequency signal coupling port 83 of the multi-stage coupler 10. Thereby, a high degree of coupling of the multistage coupler 10 can be achieved.

Next, referring to fig. 5 and 6, the application of the multi-stage coupler 10 in the base station antenna 100 according to some embodiments of the present disclosure is described, wherein fig. 5 is a schematic diagram of the base station antenna 100 according to some embodiments of the present disclosure. Fig. 6 is a schematic diagram of the calibration device 130 in the base station antenna 100 of fig. 5.

As shown in fig. 5, the base station antenna 100 may include a feeding plate 110 disposed at a front side of a reflecting plate (not shown) and a radiating element array 120 mounted on the feeding plate 110. In addition, the base station antenna 100 may further include a calibration device 130 disposed at the rear side of the reflection plate. It should be noted that the actual base station antenna 100 may also have one or more of other components, such as connectors, cables, phase shifters, remote electronic tilting units, diplexers, etc. To avoid obscuring the gist of the present disclosure, the drawings are not shown and other components are not discussed herein.

In a beamforming antenna, calibration means 130 is typically required to compensate for phase and/or amplitude deviations of the radio frequency signals input at the different radio frequency ports due to uncontrolled errors in the design, manufacture or use of the radio frequency control system (e.g., remote radio unit "RRU") or the antenna feed network. This process is commonly referred to as "calibration".

As shown in fig. 5 and 6, the calibration device 130 may include: a dielectric substrate, a microstrip calibration circuit 140 disposed on a first surface of the dielectric substrate, and a grounded metal layer (not shown) disposed on a second surface of the dielectric substrate. The calibration circuit 140 may be used to identify any undesired variations in the amplitude and/or phase of the radio frequency signals input to the different radio frequency ports of the antenna.

As shown in fig. 6, calibration circuit 140 may include a calibration port 142, a power divider/combiner 143, and a multi-stage coupler 10 as described in this disclosure.

In some embodiments, the rf signal input port 81 of the multi-stage coupler 10 may receive an rf signal from a remote rf unit as an rf port. In some embodiments, the rf signal input port 81 of the multi-stage coupler 10 may be electrically connected to each other with a separate rf port to receive rf signals from a remote rf unit.

The radio frequency signal output port 82 of the multi-stage coupler 10 may be configured to output radio frequency signals to the radiating element array 120 to generate corresponding antenna beams by the radiating element array 120.

The rf signal coupling port 83 of the multi-stage coupler 10 may be configured to extract a portion of the rf signal from the rf signal input port 81 and combine the extracted rf signal into a calibration signal by the power combiner 143 for transmission of the combined calibration signal back to the remote rf unit via the calibration port 142. The remote radio frequency unit may adjust the amplitude and/or phase of the radio frequency signal to be input on the radio frequency port accordingly based on the calibration signal to provide an optimized antenna beam. It should be appreciated that the calibration device 130 may include any suitable configuration and/or mode of operation and is not limited to the embodiments described above.

Based on the high degree of coupling of the multi-stage coupler 10, the calibration device 130 may allow the radio frequency signal for the radiating element array to be extracted only a relatively small portion by the multi-stage coupler 10, so that the energy utilization of the antenna system may be effectively improved and the load of the calibration circuit 140 may be effectively reduced.

Although some specific embodiments of the present disclosure have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. The embodiments disclosed herein may be combined in any desired manner without departing from the spirit and scope of the present disclosure. Those skilled in the art will also appreciate that various modifications might be made to the embodiments without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims (10)

1. A multi-stage coupler, comprising:

a first coupler, comprising: a first primary transmission line electrically connected in series between an input port and an output port of the first coupler; a first secondary transmission line electrically connected in series between the coupling port and the isolation port of the first coupler; and

a second coupler, comprising: a second primary transmission line electrically connected in series between an input port and an output port of the second coupler; and a second secondary transmission line electrically connected in series between the coupling port and the isolation port of the second coupler, wherein the coupling port of the first coupler and the input port of the second coupler are electrically connected to each other.

2. The multi-stage coupler of claim 1, wherein the coupling port of the first coupler and the input port of the second coupler are electrically connected to each other such that the first secondary transmission line transitions continuously to the second primary transmission line.

3. The multi-stage coupler of claim 1, wherein the input port of the first coupler is configured as a radio frequency signal input port of the multi-stage coupler, the output port of the first coupler is configured as a radio frequency signal output port of the multi-stage coupler, and the isolation port of the second coupler is configured as a radio frequency signal coupling port of the multi-stage coupler.

4. The multi-stage coupler of claim 1, wherein the multi-stage coupler comprises a third coupler comprising: a third primary transmission line electrically connected in series between the input port and the output port of the third coupler; and a third secondary transmission line electrically connected in series between the coupling port and the isolation port of the third coupler, wherein the isolation port of the second coupler and the input port of the third coupler are electrically connected to each other.

5. The multi-stage coupler of claim 4, wherein the isolation port of the second coupler and the input port of the third coupler are electrically connected to each other such that the second secondary transmission line transitions continuously to the third primary transmission line.

6. The multi-stage coupler of claim 4, wherein the input port of the first coupler is configured as a radio frequency signal input port of the multi-stage coupler, the output port of the first coupler is configured as a radio frequency signal output port of the multi-stage coupler, and the isolation port of the third coupler is configured as a radio frequency signal coupling port of the multi-stage coupler.

7. The multistage coupler according to one of claims 1 to 6, characterized in that the degree of coupling of the multistage coupler is higher than 30dB; and/or

The coupling degree of the multistage coupler is higher than 36dB; and/or

The coupling degree of the multistage coupler is higher than 40dB; and/or

The directivity of the multistage coupler is higher than 10dB; and/or

The directivity of the multistage coupler is higher than 13dB; and/or

The directivity of the multistage coupler is higher than 15dB; and/or

Each coupler is configured to be substantially identical; and/or

The secondary transmission lines of the couplers are respectively configured as nonlinear secondary transmission lines; and/or

The nonlinear secondary transmission line includes a first coupling segment reactively coupled to a first portion of the corresponding primary transmission line, a second coupling segment reactively coupled to a second portion of the corresponding primary transmission line, and an intermediate segment electrically coupled in series between the first coupling segment and the second coupling segment; and/or

The intermediate section is closer to the respective primary transmission line than the first and second coupling sections; and/or

The nonlinear secondary transmission line includes a coupling stub disposed on the intermediate section to tune a coupling characteristic between the secondary transmission line and the corresponding primary transmission line; and/or

The first coupling section and the second coupling section are spaced apart from the corresponding primary transmission line by the same distance; and/or

The second coupling section is closer to the respective primary transmission line than the first coupling section such that there is an asymmetry in reactive coupling between the first and second portions of the respective primary transmission line and the nonlinear secondary transmission line; and/or

The multi-stage coupler is configured as a printed metal pattern.

8. Calibration device for a base station antenna, characterized in that it comprises:

a dielectric substrate;

calibration circuitry printed on a dielectric substrate, the calibration circuitry comprising a multi-stage coupler according to one of claims 1 to 7, a power combiner and a calibration port.

9. The calibration device of claim 8, wherein,

the radio frequency signal input port of the multistage coupler is configured to receive a radio frequency signal;

the radio frequency signal output port of the multistage coupler is configured to output radio frequency signals to the radiating element array;

the radio frequency signal coupling port of the multistage coupler is configured to extract a part of radio frequency signals from the radio frequency signal input port and combine the extracted radio frequency signals into a calibration signal through the power combiner so as to output the calibration signal through the calibration port; and/or

The calibration circuit is configured as a microstrip line calibration circuit.

10. A base station antenna, comprising:

a reflection plate;

a feeding plate disposed at a front side of the reflecting plate and a radiating element array mounted on the feeding plate;

a multistage coupler according to one of claims 1 to 7 or a calibration device according to one of claims 8 to 9 arranged on the rear side of the reflecting plate.