A RF broadband miniaturized coupler

Abstract

The present invention relates to a radio frequency broadband coupler, belonging to the field of radio frequency broadband technology. The invention solves the technical problem in the prior art that broadband couplers are required to have low insertion loss, high power capacity, good broadband characteristics and be miniaturized, thereby improving the application platform and scope of the coupler. The radio frequency broadband coupler comprises a transformer, a forward coupling adjustment circuit and a reverse coupling adjustment circuit. The forward coupling adjustment circuit and the reverse coupling adjustment circuit each comprise a plurality of resistors of equal resistance connected in parallel. One end of the forward coupling adjustment resistor is electrically connected to one end of the secondary coil of the transformer, and the other end is grounded. One end of the reverse coupling adjustment resistor is electrically connected to the other end of the secondary coil of the transformer, and the other end is grounded. The present invention adopts a combination of transformer coupling and resistor coupling to achieve a coupler with good broadband characteristics, high directivity and miniaturization.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency broadband technology, and in particular to a radio frequency broadband coupler. Background Art

[0002] With the continuous development of communication technology, modern communication systems and other microwave systems cover increasingly wider frequency bands. In RF broadband transmitter systems, directional couplers can detect output power and standing waves, enabling effective control of system functions and accurate evaluation of system performance. As power amplifiers are moving towards modularization and miniaturization, the demand for miniaturization of various components within the amplifiers is becoming increasingly urgent. There is a need to find a coupling circuit that can handle high power while also being compact.

[0003] Broadband couplers used in actual engineering applications generally have poor directivity when operating over a wide bandwidth, introducing large detection errors. From a broadband perspective, transformer coupling can operate across frequency bands and has a wide operating bandwidth, but when operating in weak coupling, the number of turns is large, and the inter-turn capacitance affects the upward expansion of the operating frequency. Other coupling methods are large in size at the low end of the frequency range and cannot be miniaturized. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a radio frequency broadband coupler, which uses a strip line and a magnetic core in a certain way to achieve transformer coupling, and combines it with a resistive coupling circuit to achieve a coupler with good broadband characteristics, high directivity and miniaturization.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] The present invention provides a radio frequency broadband coupler, which includes a transformer, a forward coupling adjustment circuit, and a reverse coupling adjustment circuit; the forward coupling adjustment circuit and the reverse coupling adjustment circuit each include a plurality of resistors with equal resistance values connected in parallel; one end of the forward coupling adjustment resistor is electrically connected to one end of the secondary coil of the transformer, and the other end is grounded; one end of the reverse coupling adjustment resistor is electrically connected to the other end of the secondary coil of the transformer, and the other end is grounded.

[0007] Furthermore, the transformer includes: a magnetic core, a primary coil and a secondary coil; wherein,

[0008] The magnetic core has a square outer structure and a rectangular through hole is provided in the middle.

[0009] The primary coil and the secondary coil are arranged on a printed circuit board. The printed circuit board passes through the rectangular through hole of the magnetic core, and the middle part of the printed circuit board is fixedly arranged in the rectangular through hole of the magnetic core.

[0010] Furthermore, the secondary coil includes copper foils arranged on the top and bottom layers of a printed circuit board. The copper foils on the top and bottom layers have the same structure, and both ends are connected to the ground via a forward coupling adjustment resistor and a reverse coupling adjustment resistor, respectively, to form a grounding metal strip with a stripline structure.

[0011] Furthermore, the primary coil includes a copper foil trace arranged in the middle layer of the printed circuit board. The copper foil trace is parallel to the ground metal strip of the stripline structure and has a width smaller than the width of the ground metal strip, forming an inner conductor structure of the stripline. The characteristic impedance of the copper foil trace is the same as the port characteristic impedance of the broadband coupler.

[0012] Furthermore, the distances between the rectangular through holes of the magnetic core and their corresponding surfaces on the magnetic core are equal.

[0013] Furthermore, the forward coupling end of the coupler also includes a first forward coupling resistor, and the reverse coupling end also includes a first reverse coupling resistor; vias are respectively provided at both ends of the inner conductor structure; one end of the inner conductor structure is connected to the forward input port of the coupler through the via, and the other end is connected to the reverse input port through the via.

[0014] One end of the grounding metal strip of the strip line is connected to the forward coupling port through a first forward coupling resistor, and the other end is connected to the reverse coupling port through a first reverse coupling resistor.

[0015] Furthermore, the forward coupling adjustment resistor and the reverse coupling adjustment resistor are arranged on the printed board in a left-right symmetrical and top-down mirrored structure; the number of the forward coupling adjustment resistors is 2n, wherein n resistors are arranged on the top layer of the forward coupling end of the printed board, and the remaining n resistors are arranged on the bottom layer of the printed board and the mirrored position of the top layer resistor; symmetrically, the number of the reverse coupling adjustment resistors is 2n, wherein n resistors are arranged on the top layer of the reverse coupling end of the printed board, and the remaining n resistors are arranged on the bottom layer of the printed board and the mirrored position of the top layer resistor; wherein n is a positive integer greater than 1.

[0016] Furthermore, the forward coupling end and the reverse coupling end also include a second forward coupling resistor and a second reverse coupling resistor; at the forward coupling end, the second forward coupling resistor is connected between the forward input port and the forward coupling port of the coupler; symmetrically, at the reverse coupling end, the second reverse coupling resistor is connected between the reverse input port and the reverse coupling port of the coupler.

[0017] Furthermore, the resistance of the 2n parallel-connected coupling adjustment resistors is 2n*R e , the equivalent resistance of 2n resistors in parallel is R eThe first forward coupling resistor and the first reverse coupling resistor have the same resistance value, and the equivalent resistance value is R; the second forward coupling resistor and the second reverse coupling resistor have the same resistance value, and the equivalent resistance value is R d , the equivalent resistance R, R d and R e Satisfies the relationship:

[0018] R 2 =R d *R e ,

[0019] Wherein R is also the port characteristic impedance value of the broadband coupler.

[0020] Furthermore, the coupling degree of the signal output from the same-direction coupling port satisfies the formula:

[0021] A c =-20lg(R / R e ).

[0022] Beneficial effects of this technical solution:

[0023] The present invention utilizes a method combining transformer coupling and resistor coupling to solve the technical problem of miniaturization of broadband couplers while ensuring detection accuracy. The coupling degree can be achieved by adjusting the corresponding resistance values, thereby broadening the application platform and scope of the coupler. The present invention has a simple circuit structure and low cost. The four ports have the same characteristic impedance, are all pure resistors, have a small standing wave, and are simple to process and debug.

[0024] The key technical points of the present invention are:

[0025] 1. The stripline structure is combined with a magnetic core to replace the 1:1 transformer coupling function, and combined with resistive coupling, a RF broadband coupler with good broadband characteristics and high directivity is realized.

[0026] 2. A bilaterally symmetrical coupling adjustment circuit is adopted. The four ports of the coupler have the same characteristic impedance, which are all pure resistances. At the same time, the port characteristics of the forward input port and the reverse input port are consistent, with port reciprocity characteristics, and simple processing and debugging.

[0027] 3. The purpose of miniaturization of the coupler is achieved by utilizing the reasonable layout and combination of the magnetic core with a rectangular outer structure and inner hole and the printed circuit board.

[0028] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description or be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0030] Figure 1 This is a circuit diagram of a radio frequency broadband coupler according to an embodiment of the present invention.

[0031] Figure 2 FIG. 4 is an equivalent circuit diagram of a radio frequency broadband coupler according to an embodiment of the present invention.

[0032] FIG3( a ) is a top-layer external view of a printed circuit board A according to an embodiment of the present invention;

[0033] FIG3( b ) is an outline diagram of the bottom layer of a printed circuit board A according to an embodiment of the present invention.

[0034] FIG4( a) is a bottom surface diagram of a printed circuit board B according to an embodiment of the present invention;

[0035] FIG4( b ) is a top-layer appearance diagram of a printed circuit board B according to an embodiment of the present invention.

[0036] FIG5(a) is a front view of a connection diagram of printed circuit board A and printed circuit board B according to an embodiment of the present invention;

[0037] FIG5( b ) is a reverse view of the connection diagram of printed boards A and B according to an embodiment of the present invention.

[0038] FIG6( a ) is a C-shaped core portion of a CI core according to an embodiment of the present invention;

[0039] FIG6( b ) is an I-type core portion of a CI core according to an embodiment of the present invention;

[0040] FIG6( c ) is a diagram of a CI core assembly according to an embodiment of the present invention.

[0041] FIG7(a) is an assembly diagram of printed circuit board A and printed circuit board B with the top layer facing upward and the magnetic core after connection according to an embodiment of the present invention;

[0042] FIG7( b ) is an assembly diagram of printed circuit board A and printed circuit board B with the bottom layer facing upward and the magnetic core after being connected in another embodiment of the present invention. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0044] The technical concept of the present invention is as follows: a 1:1 transformer coupling circuit has broadband characteristics in the frequency band below 1000MHz and low insertion loss; a resistor coupling circuit is simple to implement and has little influence from parasitic parameters; a corresponding coupling degree design formula can be derived by combining the two, and a desired coupling output can be achieved by properly selecting circuit parameters; at the same time, multiple resistors are evenly placed at the upper and lower mirror positions of the printed circuit board, and a magnetic core is used to increase the parallel inductance of the transformer T1, thereby greatly improving the transformer coupling coefficient; and a stripline combined with a magnetic core method can achieve miniaturization of the coupler.

[0045] Figure 1 A circuit diagram of an embodiment of the present invention.

[0046] A specific embodiment of the present invention, as Figure 1 As shown, a radio frequency broadband coupler is disclosed, which includes a transformer, a forward coupling adjustment circuit, and a reverse coupling adjustment circuit; the forward coupling adjustment circuit and the reverse coupling adjustment circuit each include a plurality of resistors of equal resistance connected in parallel; one end of the forward coupling adjustment resistor is electrically connected to one end of the secondary coil of the transformer, and the other end is grounded; one end of the reverse coupling adjustment resistor is electrically connected to the other end of the secondary coil of the transformer, and the other end is grounded.

[0047] By providing a forward coupling adjustment circuit and a reverse coupling adjustment circuit at the forward coupling end and the reverse coupling end, respectively, and configuring the appropriate resistance value of the coupling adjustment resistor, the required coupling degree of the coupler can be obtained. In addition, by adjusting the resistance value of the coupling adjustment resistor, the coupling degree can also be fine-tuned to offset the influence of parasitic parameters of components in the printed circuit board and the circuit.

[0048] Furthermore, the number of the forward coupling adjustment resistors and the reverse coupling adjustment resistors is 2n; the resistance values of the 2n resistors are 2n*R e ; R e is the equivalent resistance value of the coupling adjustment resistors connected in parallel; in order to improve the directionality of the coupler and achieve the coupling degree required by the system, a first forward coupling resistor is further provided at the forward coupling end (exemplarily, as Figure 1 R1 in) and a second forward coupling resistor (exemplary, such as Figure 1 Symmetrically, a first reverse coupling resistor is also provided at the reverse coupling end (exemplarily, as shown in FIG. Figure 1 R in 11 ) and a second reverse coupling resistor (exemplarily, as Figure 1 R in 12), the equivalent coupling resistance value R of the first forward coupling resistor and the first reverse coupling resistor is the port characteristic impedance value of the coupler; the equivalent coupling resistance value of the second forward coupling resistor and the second reverse coupling resistor is R d The equivalent resistance R e , R and R d Connect, and form forward coupling adjustment network and reverse coupling adjustment network at the forward coupling end and reverse coupling end respectively. The equivalent circuit diagram is as follows Figure 2 shown.

[0049] Preferably, as a specific embodiment of the present invention, the forward coupling end and the reverse coupling end both use 8 coupling adjustment resistors, namely R3 to R 10 and R 13 ~R 20 , the resistance value is 8*R e In addition, it also includes the first and second forward coupling resistors R1 and R2, the first and second reverse coupling resistors R 11 and R 12 .

[0050] The broadband coupler includes four ports, namely a forward input port 1, a forward coupling port 3, a reverse input port 2, and a reverse coupling port 4.

[0051] One end of the second forward coupling resistor R2 is electrically connected to the forward coupling port 3 of the coupler, and the other end is connected to one end of the secondary coil of the transformer; one end of the first forward coupling resistor R1 is connected to the port 1 of the coupler, and the other end is connected to the port 3;

[0052] Symmetrical to the forward coupling end, at the reverse coupling end of the coupler, the second reverse coupling resistor R 12 One end of the first reverse coupling resistor R is electrically connected to the port 4 of the coupler, and the other end is connected to the other end of the secondary coil of the transformer; 11 One end is connected to port 2 of the coupler, and the other end is connected to port 4.

[0053] It should be noted that if Figure 1 As shown, adjust the resistors R3 to R 10 The resistance values of these eight resistors can be used to fine-tune the forward coupling of the coupler to offset the influence of parasitic parameters of components in the printed circuit board and circuit. Similarly, adjusting the resistor R 13 ~R 20 The resistance values of these eight resistors can be used to fine-tune the reverse coupling degree, offsetting the effects of parasitic parameters of components in the printed circuit board and circuit. The circuit has a simple structure and is easy to debug. The impedance of all four ports is purely resistive, making it easy to test and use. Ports 1 and 2 have the same port characteristics, demonstrating port reciprocity.

[0054] A specific embodiment of the present invention, as Figure 2 As shown, the 2n resistance values are all 2n*R e The coupling adjustment resistor can be equivalent to the resistor R after parallel connection. e ; and R1=R 11 Equivalent to R d ; R2=R 12 Equivalent to R, that is, resistance R1 = R 11 =R, R2=R 12 =R d ; Equivalent resistance R, R d and R e Satisfies the relationship:

[0055] R 2 =R d *R e ,

[0056] The resistance value of R is the port characteristic impedance value of the coupler;

[0057] Furthermore, the coupling degree of the signal output from the same-direction coupling port satisfies the formula:

[0058] A c =-20lg(R / R e ),

[0059] It should be noted that according to the coupling degree required by the system, R e The resistance value of R d resistance value;

[0060] At the same time, adjust the resistor R e The resistance value can also be used to adjust the coupling degree of the system.

[0061] In a specific embodiment of the present invention, the broadband coupling circuit is a combination circuit of resistance coupling and transformer coupling, which is bilaterally symmetrical. The resistors R1 to R 10 Ten pure resistors form a resistor coupling network at the forward coupling end (port 3), and the resistance relationship is: R1 = R d , R2=R, R3=R4=R5=R6=R7=R8=R9=R 10 =8*R e , and satisfy the relationship:

[0062] R 2 =R d *R e ,

[0063] Resistor R 11 ~R 20Ten pure resistors form a resistor coupling network at the reverse coupling end (port 4), and the resistance relationship is: R 11 =R d , R 12 =R, R 13 =R 14 =R 15 =R 16 =R 17 =R 18 =R 19 =R 20 =8*R e , and satisfy the relationship:

[0064] R 2 =R d *R e .

[0065] Transformer T1 is a 1:1 transformer with a coupling coefficient K value of 0.99 or above. The first port of the primary coil and the first port of the secondary coil of T1 are connected to resistors R1 to R2 respectively. 10 The forward coupled resistor network consists of ten pure resistors. Similarly, the second port of the primary coil and the second port of the secondary coil of T1 are connected to the resistor R 11 ~R 20 , a reverse-coupled resistor network consisting of ten pure resistors; when the RF signal is input from port 1, the forward-coupled signal is output at port 3, and the resistance value satisfies: R 2 =R d *R e , the ideal transformer coupling coefficient K = 1, then the signal coupling degree A at port 3 output c =-20lg(R / R e ), and the signal output from port 4 is equal to 0; when the RF signal is input from port 2, the reverse coupled signal is output at port 4, and the resistance value satisfies: R 2 =R d *R e , then the signal coupling degree A at port 4 output is c =-20lg(R / R e ), and the signal output from port 3 is equal to 0.

[0066] In specific implementation, the coupler structure of the present application is realized by combining a printed circuit board and a magnetic core, wherein the printed circuit board has a three-layer structure.

[0067] The transformer secondary coil of the coupler includes copper foils arranged on the top and bottom layers of the printed circuit board. The copper foils of the top and bottom layers have the same structure, and their two ends are connected to the ground via a forward coupling adjustment resistor and a reverse coupling adjustment resistor, respectively, to form a grounded metal strip with a stripline structure. As a specific embodiment of the present invention, the copper foils of the top and bottom layers can be electrically connected through vias on the printed circuit board to form a grounded metal strip with a stripline structure. The primary coil includes a copper foil trace arranged on the middle layer of the printed circuit board. The copper foil trace is parallel to the grounded metal strip structure and has a width smaller than that of the grounded metal strip, forming an inner conductor structure.

[0068] Vias are provided at both ends of the inner conductor structure; one end of the inner conductor structure is connected to the forward input port 1 of the coupler through the via, and the other end is connected to the reverse input port 2 through the via.

[0069] One end of the grounding metal strip is connected to the forward coupling port 3 through a first forward coupling resistor arranged on the top layer of the printed circuit board, and is connected to the ground through 2n forward coupling adjustment resistors mirror-imaged on the top and bottom layers of the printed circuit board; the other end is connected to the reverse coupling port 4 through a first reverse coupling resistor placed on the top layer of the printed circuit board, and is connected to the ground through 2n reverse coupling adjustment resistors mirror-imaged on the top and bottom layers of the printed circuit board.

[0070] The top layer of the printed circuit board also includes a second forward coupling resistor and a second reverse coupling resistor, wherein the second forward coupling resistor is electrically connected between the forward input port and the forward coupling port through a copper foil trace; and the second reverse coupling resistor is electrically connected between the reverse input port and the reverse coupling port through the copper foil trace.

[0071] In a specific embodiment of the present invention, as shown in FIG3 and FIG4, for the convenience of debugging, the printed circuit board can be set to two to achieve a three-layer structure. This embodiment is described with printed circuit board A and printed circuit board B.

[0072] Printed circuit board A is narrow in the middle and wide at both ends, with a symmetrical structure. A top layer of intermediate copper foil and grounding copper foil is laid, as shown in Figure 3(a). The intermediate copper foil, adapted to printed circuit board A, has a narrow center and wide ends, with one end serving as a forward coupling terminal and the other as a reverse coupling terminal. N forward coupling adjustment resistors of equal resistance are placed relatively evenly between the intermediate copper foil and the grounding copper foil at the forward coupling terminal. Symmetrically, n reverse coupling adjustment resistors of equal resistance are placed relatively evenly between the intermediate copper foil and the grounding copper foil at the reverse coupling terminal. Specifically, this embodiment uses four coupling adjustment resistors as an example. One end of each coupling adjustment resistor is connected to the intermediate copper foil, and the other end is connected to ground via the grounding copper foil at both ends of the printed circuit board, for a total of eight.

[0073] The top layer of printed circuit board A further includes a first forward coupling resistor and a second forward coupling resistor at the forward coupling end, one end of the intermediate copper foil is connected to the forward coupling port through the first forward coupling resistor, one end of the second forward coupling resistor is connected to the forward coupling port through a copper foil trace, and the other end is respectively connected to the forward input port and one end of the inner conductor structure of the bottom layer of the printed circuit board through the copper foil trace and a via; symmetrically, the first reverse coupling resistor and the second reverse coupling resistor are further included at the reverse coupling end; the other end of the intermediate copper foil is connected to the reverse coupling port through the first reverse coupling resistor, one end of the second reverse coupling resistor is connected to the reverse coupling port through a copper foil trace, and the other end is respectively connected to the reverse input port and the other end of the inner conductor structure of the bottom layer of the printed circuit board through the copper foil trace and a via.

[0074] The bottom layer of the printed circuit board A is an inner conductor layer, wherein a copper foil trace is arranged in the middle thereof to form an inner conductor structure. The width of the inner conductor copper foil trace is smaller than the width of the copper foil of the top layer.

[0075] As a specific embodiment, as shown in Figure 3(b), preferably, the inner conductor structure has a strip-shaped routing structure in the middle, and the two ends can be designed as square copper foil routings, respectively, and are connected to the forward input port and the reverse input port through vias at both ends. The shape and size of the square copper foil routing are adjusted by simulation to reduce the port standing wave.

[0076] It should be noted that the copper foils on the top and bottom layers of the printed circuit board must completely cover the inner conductor and the square copper foils at the two ports, which can effectively prevent the signal leakage of the inner conductor and avoid the coupled signal from being interfered with by the leakage signal of the inner conductor; preferably, the width of the copper foils on the top and bottom layers of the printed circuit board is not less than 3 times the width of the copper foil trace in the middle part of the inner conductor; furthermore, after the copper foil area of the top and bottom layers is increased, it is convenient to place the coupling adjustment resistors R3 to R 10 and R 13 ~R 20 Connecting multiple resistors in parallel can improve the accuracy of the resistors, which is beneficial to improving the coupling accuracy of the coupler.

[0077] The outer structure of the printed circuit board B is the same as that of the printed circuit board A, except that the bottom layer is covered with copper foil. As shown in FIG4(a), its shape is consistent with the shape of the top layer of the copper foil of the printed circuit board A. Four resistors of the same resistance are placed on each of the left and right sides at mirror positions of the coupling adjustment resistors set on the top layer of the printed circuit board A. One end of the resistors is connected to the middle copper foil, and the other end is soldered to the ground through the grounding copper foil. There are eight resistors in total.

[0078] When assembling the printed circuit board A and the printed circuit board B, the inner conductor layer is arranged between the two printed circuit boards, and the two printed circuit boards are placed overlapping. Since both printed circuit boards are bilaterally symmetrical structures, the forward coupling end and the reverse coupling end do not need to be restricted in direction during assembly and can be placed in any corresponding position.

[0079] Furthermore, the characteristic impedance of the bottom inner conductor copper foil trace of the printed circuit board A is the same as the port characteristic impedance of the coupler. If the port characteristic impedance required by the system is 50Ω, the characteristic impedance of the inner conductor structure is 50 ohms.

[0080] It should be noted that the inner conductor structure of the bottom layer of printed board A can also be moved to the top layer of printed board B.

[0081] FIG5 is a connection diagram of printed circuit boards A and B according to an embodiment of the present invention.

[0082] In a specific embodiment of the present invention, as shown in Figures 5(a) and 5(b), the printed circuit board A and the printed circuit board B are stacked together with the top layer facing upward; the top copper foil of the printed circuit board A and the bottom copper foil of the printed circuit board B have the same structure, and both ends are connected to the ground through a forward coupling adjustment resistor and a reverse coupling adjustment resistor, respectively, to form a grounding metal strip with a stripline structure; as a specific embodiment of the present invention, for the convenience of debugging, the printed circuit board A and the printed circuit board B are designed with vias at corresponding positions for electrically connecting the top copper foil of the printed circuit board A and the bottom copper foil of the printed circuit board B to form a grounding metal strip with a stripline structure; vias are designed at both ends of the copper foil routing of the inner conductor layer, respectively for connecting the forward input port and the reverse input port of the coupler.

[0083] Furthermore, the structure of the grounding metal strip of the strip line can be designed to be I-shaped, wide at both ends and narrow in the middle, and the overall width of the grounding metal strip should be wider than the inner conductor to ensure that it can completely wrap the inner conductor line. This structure can effectively prevent radio frequency leakage and improve the transformer coupling coefficient.

[0084] In another embodiment of the present invention, the printed circuit board can be implemented using a single printed circuit board, wherein the top and bottom layers are both covered with copper foil, and the copper foil structures of the top and bottom layers are identical, with both ends connected to ground via a forward coupling adjustment resistor and a reverse coupling adjustment resistor, respectively, to form a grounded metal strip with a stripline structure. The copper foil is narrow in the middle and wide at both ends, with n coupling adjustment resistors of the same resistance placed relatively evenly on the left and right sides and in upper and lower mirror positions, forming a symmetrical structure. One end of the coupling adjustment resistor is connected to the middle copper foil, and the other end is soldered to ground. The middle layer of the printed circuit board is an inner conductor layer, with a copper foil trace arranged in the middle position to form an inner conductor structure. The width of the inner conductor copper foil trace is narrower than that of the copper foil of the top and bottom layers, so that it is completely wrapped by the grounded metal strip, effectively preventing radio frequency leakage and improving the coupling coefficient of the transformer.

[0085] Furthermore, on the top layer of the printed circuit board, a first forward coupling resistor and a second forward coupling resistor are respectively included at the forward coupling end, one end of the intermediate copper foil is connected to the forward coupling port through the first forward coupling resistor, one end of the second forward coupling resistor is connected to the forward coupling port through a copper foil trace, and the other end is respectively connected to the forward input port and one end of the inner conductor structure below the printed circuit board through the copper foil trace and a via. Symmetrically, a first reverse coupling resistor and a second reverse coupling resistor are also included at the reverse coupling end; the other end of the intermediate copper foil is connected to the reverse coupling port through the first reverse coupling resistor, one end of the second reverse coupling resistor is connected to the reverse coupling port through a copper foil trace, and the other end is respectively connected to the reverse input port and the other end of the inner conductor structure on the bottom layer of the printed circuit board through the copper foil trace and a via.

[0086] It should be noted that, in order to improve the directivity of the coupler, the coupling coefficient K value of the coupler must be increased first. The method of increasing the coupling coefficient K value of the present invention is: by using n equal resistances (n*R e ) in parallel, and multiple resistors are evenly placed in the upper and lower mirror positions of the printed circuit board to improve the coupling coefficient. The resistor positions are shown in Figure 5(a) and Figure 5(b).

[0087] FIG6 is an external view of a CI-type magnetic core according to an embodiment of the present invention.

[0088] In a specific embodiment of the present invention, as shown in FIG6 , the outer shape structure and the middle through hole of the magnetic core are both square. The magnetic core can adopt a CI structure or a CC structure. The present invention is illustrated by a CI-type magnetic core, which is divided into two parts. As shown in FIG6( a ), a rectangular groove is provided in the middle of the C-type structure. The shape and size of the rectangular groove are adapted to the outer shape and size of the narrower part in the middle of the printed circuit board, and is used to place the printed circuit board. As shown in FIG6( b ), the I-type structure is a rectangular parallelepiped, which is used to cooperate with the C-type structure to fix the printed circuit board in the middle of the CI-type magnetic core.

[0089] The distances between the rectangular through holes of the magnetic core and their corresponding surfaces on the magnetic core are equal.

[0090] It should be noted that the size of the magnetic core can be adjusted through simulation to obtain the effective magnetizing inductance of the magnetic core at the low end of the operating frequency of the coupler, so that it meets the coupling coefficient of the transformer not less than 0.95; in order to meet the needs of miniaturization, the outer structure of the magnetic core can be designed as a rectangular parallelepiped, with the corresponding outer surfaces parallel to each other, and the wall thickness between the rectangular through hole and its corresponding surface on the magnetic core is equal.

[0091] FIG7(a) is an assembly diagram of printed circuit board A and printed circuit board B with the top layer facing upward and the magnetic core after being connected according to one embodiment of the present invention; FIG7(b) is an assembly diagram of printed circuit board A and printed circuit board B with the bottom layer facing upward and the magnetic core after being connected according to another embodiment of the present invention.

[0092] In one specific embodiment of the present invention, after printed circuit board A and printed circuit board B are connected with their top layers facing upward, as shown in FIG7(a), the middle portion of the printed circuit board can be placed with its top layers facing upward into the groove of the magnetic core C structure. In another embodiment of the present invention, as shown in FIG7(b), the connected printed circuit board can also be placed with its bottom layers facing upward into the groove of the magnetic core C structure. Furthermore, a fixing glue is used to adhere the I-type magnetic core to the corresponding position of the C-type magnetic core. The CI magnetic core and the printed circuit board are installed as shown in FIG7(a) or FIG7(b). The combination of the CI-type magnetic core and the printed circuit board achieves a miniaturized coupler and ensures that the inductance of the transformer T1 reaches 200nH or more.

[0093] It should be noted that the shapes of the magnetic core and the printed circuit board can be designed as needed. The coupler designed with the CI-type magnetic core and the I-shaped printed circuit board of the specific embodiment of the present invention minimizes the height of the magnetic core and achieves a miniaturized effect.

[0094] The grounded metal strip, inner conductor and magnetic core combination of the stripline realizes a 1:1 transformer function; the magnetic core increases the parallel inductance of the transformer T1, effectively improves the coupling coefficient K, and further improves the directivity of the coupler.

[0095] In addition, multiple resistors at different positions are connected in parallel. The stripline form of this structure can be infinitely close to the coaxial line coupling form and has broadband performance.

[0096] Among them, the grounding metal strips on the top and bottom layers of the printed circuit board can be equivalent to the outer conductor of the coaxial cable, and the inner conductor line of the inner conductor layer of the printed circuit board can be equivalent to the inner conductor of the coaxial cable. The grounding metal strips, inner conductors and magnetic core of the strip line are combined to realize the coaxial cable coupling function.

[0097] The function of the transformer T1 in the present invention is to achieve 1:1 coupling, which can be achieved in two main circuit modes:

[0098] First, a twisted pair with a characteristic impedance of R is wound around a magnetic core. The circuit is simple and easy to process. However, because the coupling coefficient K of the transformer cannot be made very high, its working bandwidth and power capacity are limited, and the product consistency is also poor.

[0099] Secondly, when a coaxial line with a characteristic impedance of R passes through a toroidal core, the coupling coefficient K can be made very high, but the installation of the coupling adjustment resistor is difficult, and the toroidal core is too tall to be miniaturized. In applications where miniaturization is not required, a coaxial line can be used to replace the stripline function implemented by the printed circuit board, and transformer coupling can be performed with the magnetic core. This can also achieve the technical indicators of the invention, but it cannot achieve the miniaturization goal achieved by the present invention. The magnetic core of the coaxial line method can only be a toroidal core. In order to achieve broadband and low insertion loss indicators, the height of the magnetic ring must be relatively high. In addition, the coupling adjustment resistor needs to be welded into a disc shape around the outer shell of the coaxial line, which will make the coupler larger.

[0100] This solution has excellent broadband performance. It uses a matching combination of a magnetic core with a square outer structure and inner hole and a printed circuit board to realize the function of a stripline 1:1 impedance converter, with excellent broadband performance and a small size. Because the circuit form used is a coupling method that combines resistive coupling and transformer coupling, the working bandwidth is wide and processing and debugging are convenient.

[0101] In summary, the present invention discloses a radio frequency broadband coupler, which includes a transformer, a forward coupling adjustment circuit, and a reverse coupling adjustment circuit; the forward coupling adjustment circuit and the reverse coupling adjustment circuit each include a plurality of resistors of equal resistance connected in parallel; one end of the forward coupling adjustment resistor is electrically connected to one end of the secondary coil of the transformer, and the other end is grounded; one end of the reverse coupling adjustment resistor is electrically connected to the other end of the secondary coil of the transformer, and the other end is grounded. The present invention replaces the 1:1 transformer coupling function by combining a stripline structure with a magnetic core, and combines it with resistive coupling to achieve a radio frequency broadband coupler with good broadband characteristics and high directivity; and adopts a bilaterally symmetrical coupling adjustment circuit, with the four ports having the same characteristic impedance, all of which are pure resistors. At the same time, the port characteristics of the forward input port and the reverse input port are consistent, with port reciprocity characteristics, and simple processing and debugging; the present invention utilizes a magnetic core with a rectangular outer structure and inner hole, and a reasonable layout and combination with a printed circuit board to achieve the purpose of miniaturization of the coupler.

[0102] Those skilled in the art will appreciate that all or part of the process steps of the methods in the above embodiments can be implemented by instructing relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, such as a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0103] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A radio frequency broadband coupler, characterized in that: The invention comprises a transformer, a forward coupling adjustment circuit and a reverse coupling adjustment circuit; the forward coupling adjustment circuit and the reverse coupling adjustment circuit each comprise a plurality of resistors of equal resistance connected in parallel; as well as, One end of the forward coupling adjustment resistor corresponding to the forward coupling adjustment circuit is electrically connected to one end of the secondary coil of the transformer, and the other end is grounded; One end of the reverse coupling adjustment resistor corresponding to the reverse coupling adjustment circuit is electrically connected to the other end of the secondary coil of the transformer, and the other end is grounded; The transformer comprises: a magnetic core, a primary coil and the secondary coil; wherein, The magnetic core has a square shape and a rectangular through hole in the middle. The primary coil and the secondary coil are arranged on a printed circuit board, the printed circuit board passes through the rectangular through hole of the magnetic core, and the middle part of the printed circuit board is fixedly arranged in the rectangular through hole of the magnetic core; The secondary coil includes copper foils arranged on the top and bottom layers of a printed circuit board, the copper foils on the top and bottom layers have the same structure, and both ends are connected to the ground via the forward coupling adjustment resistor and the reverse coupling adjustment resistor, respectively, to form a grounding metal strip with a stripline structure; The primary coil includes a copper foil trace arranged on the middle layer of the printed circuit board. The copper foil trace is parallel to the ground metal strip of the stripline structure and has a width smaller than that of the ground metal strip, forming a stripline inner conductor structure. The characteristic impedance of the copper foil trace is the same as the port characteristic impedance of the broadband coupler.

2. The radio frequency broadband coupler according to claim 1, wherein: The distances between the rectangular through holes of the magnetic core and their corresponding surfaces on the magnetic core are equal.

3. The radio frequency broadband coupler according to claim 1, wherein: The forward coupling end of the coupler further includes a first forward coupling resistor, and the reverse coupling end further includes a first reverse coupling resistor; via holes are respectively provided at both ends of the inner conductor structure; one end of the inner conductor structure is connected to the forward input port of the coupler through the via hole, and the other end is connected to the reverse input port through the via hole; One end of the grounding metal strip of the stripline structure is connected to the forward coupling port via a first forward coupling resistor, and the other end is connected to the reverse coupling port via a first reverse coupling resistor.

4. The radio frequency broadband coupler according to claim 3, characterized in that: The forward coupling adjustment resistor and the reverse coupling adjustment resistor are arranged on the printed board in a left-right symmetrical and top-bottom mirrored structure; The number of the forward coupling adjustment resistors is 2n, wherein n resistors are arranged on the top layer of the forward coupling end of the printed circuit board, and the remaining n resistors are arranged at the mirror image position of the bottom layer of the printed circuit board and the top layer of the forward coupling end resistor; Symmetrically, the number of the reverse coupling adjustment resistors is 2n, of which n are arranged on the top layer of the reverse coupling end of the printed circuit board, and the remaining n are arranged at the mirror image position of the bottom layer of the printed circuit board and the top layer of the reverse coupling end resistor; Wherein, n is a positive integer greater than 1.

5. The radio frequency broadband coupler according to claim 4, characterized in that: The forward coupling end and the reverse coupling end further include a second forward coupling resistor and a second reverse coupling resistor respectively; At the forward coupling end, the second forward coupling resistor is connected between the forward input port and the forward coupling port of the coupler; Symmetrically, at the reverse coupling end, the second reverse coupling resistor is connected between the reverse input port and the reverse coupling port of the coupler.

6. The radio frequency broadband coupler according to claim 5, characterized in that: The resistance of 2n parallel coupling adjustment resistors is 2n*R e , the equivalent resistance of 2n resistors in parallel is R e The first forward coupling resistor and the first reverse coupling resistor have the same resistance value, and the equivalent resistance value is R; The second forward coupling resistor and the second reverse coupling resistor have the same resistance value, and the equivalent resistance value is R d , the equivalent resistance values R, R d and R e Satisfies the relationship: R 2 =R d *R e , Wherein R is also the port characteristic impedance value of the broadband coupler.

7. The radio frequency broadband coupler according to claim 6, characterized in that: The coupling degree of the signal output from the same-direction coupling port satisfies the formula: A c =-20lg(RR e )。

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