A broadband directional coupler

Abstract

The present invention discloses a broadband directional coupler comprising an input port, an output port, a coupling port, and a coupling assembly. The coupling assembly comprises a first coupling network and a compensation network; the first coupling network is connected to the input port, the output port, and the compensation network; and the coupling port is connected to the compensation network. The broadband directional coupler provided by this solution is suitable for high-power directional couplers with a flat coupling coefficient across the entire frequency range from 1kHz to 500MHz. It not only offers low insertion loss and stable operation, but also maintains good performance at low frequencies.

Description

Technical Field

[0001] The invention belongs to the technical field of coupling, and in particular relates to a broadband directional coupler. Background Art

[0002] A directional coupler is a commonly used RF component that can couple a portion of the power from the main transmission path and output it to a specific port, achieving the purpose of online monitoring of forward transmission power and reflected power.

[0003] In broadband, medium- and high-power RF measurement systems, directional couplers require not only low insertion loss, high power handling, and good directivity, but also extremely high bandwidth. Cavity-based directional couplers, with their high power handling, excellent directivity, and low mainline insertion loss, have been widely used in medium- and high-power systems. However, due to size limitations, cavity-based directional couplers struggle to cover lower frequency bands.

[0004] Existing low-insertion-loss directional couplers have a narrow bandwidth, while wide-bandwidth couplers struggle to achieve low insertion loss and have low power handling capabilities. Broadband, medium- and high-power measurement systems must employ multiple directional couplers to achieve wide frequency coverage. This increases errors introduced by frequent switching of test ports and hinders automated control of test systems. Therefore, existing low-insertion-loss directional couplers require further improvement and development. Summary of the Invention

[0005] The object of the present invention is to provide a broadband directional coupler in view of the above problems.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A broadband directional coupler comprises an input port, an output port, a coupling port and a coupling component, wherein the coupling component comprises a first coupling network and a compensation network;

[0008] The first coupling network is connected to the input port, the output port, and the compensation network;

[0009] The coupling port is connected to the compensation network.

[0010] In the above broadband directional coupler, the input port is connected to an input cable having an inner conductor and an outer conductor;

[0011] The first coupling network includes a second resistor R2, a third resistor R3 and a fourth resistor R4;

[0012] The inner conductor of the input cable is connected to one end of the second resistor R2 and the output port, and the end of the second resistor R2 away from the input port is connected to the compensation network;

[0013] The outer conductor of the input cable is connected to one end of the fourth resistor R4, the end of the fourth resistor R4 away from the input port is connected to the output port, and the fourth resistor R4 and the output port are connected to one end of the third resistor R3, and the end of the third resistor R3 away from the output port is connected to the compensation network.

[0014] In the above broadband directional coupler, the resistance of the second resistor R2 is 1K-10K ohms, the resistance of the third resistor R3 is 10 ohms-100 ohms, and the resistance of the fourth resistor R4 is 0.1-1 ohm.

[0015] In the above-mentioned broadband directional coupler, the fourth resistor R4 is formed by connecting a plurality of resistors in parallel, and the plurality of resistors connected in parallel make the resistance of the fourth resistor R4 be 0.1-1 ohm.

[0016] In the above-mentioned broadband directional coupler, the first coupling network includes a circuit board and a resistor integrated unit arranged on the circuit board, and the resistor integrated unit includes a resistor integrated area, an external conductive connection area, and a first through-hole and a second through-hole provided on the circuit board;

[0017] The plurality of resistors constituting the fourth resistor R4 are uniformly arranged circumferentially on the circuit board to form the resistor integration area in a ring shape;

[0018] The external conductive connection region is located within the annular region of the resistor integrated region, and the external conductive connection region has an annular structure, and the annular central axis of the external conductive connection region coincides with the annular central axis of the resistor integrated region;

[0019] The first through hole is opened at the center of the external conductor connection area;

[0020] The second through hole is formed outside the external conductive connection region and inside the resistor integrated region or extends inward from the ring line of the resistor integrated region;

[0021] A central connection line between the first through-hole and the second through-hole coincides with a symmetry axis of the resistor integrated region;

[0022] The outer conductor connection region is electrically connected to the resistor integrated region, and the outer conductor is electrically connected to the outer conductor connection region, so that the outer conductor is connected to the fourth resistor R4;

[0023] The inner conductor passes through the first through-hole and is connected to the second resistor R2 , and the inner conductor passes through the second through-hole and is connected to the compensation network.

[0024] In the above-mentioned broadband directional coupler, the compensation network includes a first compensation circuit and a second compensation circuit connected in series;

[0025] The first compensation circuit includes a first compensation resistor R11 and a second compensation resistor R12 connected in series. The first compensation resistor R11 and the second compensation resistor R12 are connected in parallel with a first compensation inductor L1. A first compensation capacitor C1 is connected between the first compensation resistor R11 and the second compensation resistor R12. An end of the first compensation capacitor C1 away from the first compensation resistor R11 and the second compensation resistor R12 is connected to a third compensation resistor R13. An end of the third compensation resistor R13 away from the first compensation capacitor C1 is grounded.

[0026] The second compensation circuit is a π-type compensation circuit including a fourth compensation resistor R14 , a fifth compensation resistor R15 , and a sixth compensation resistor R16 .

[0027] In the above broadband directional coupler, the input port, output port and coupling port are all grounded.

[0028] In the above-mentioned broadband directional coupler, the coupling assembly further includes a first ground isolation device T1 and a second ground isolation device T2;

[0029] The first ground isolation device T1 is located between the first coupling network and the output port;

[0030] The second ground isolation device T2 is located between the first coupling network and the compensation network.

[0031] In the above-mentioned broadband directional coupler, the coupling component further includes a second coupling network, and the first coupling network and the second coupling network are connected in a mirror-symmetrical relationship via the first ground isolation device T1;

[0032] The coupling port is connected to the first coupling network through the compensation network and the second ground isolation device T2;

[0033] The input port is connected to an end of the first coupling network away from the second coupling network, and the output port is connected to an end of the second coupling network away from the first coupling network;

[0034] The second coupling network corresponds to the first coupling network and is used for connecting one end of the coupling port to the output port via the second compensation network and the isolation port.

[0035] In the aforementioned broadband directional coupler, the second coupling network includes a sixth resistor R6, a seventh resistor R7, and a ninth resistor R9, which are mirror images of the second resistor R2, the third resistor R3, and the fourth resistor R4 of the first coupling network, respectively. The first and second coupling networks have the same network structure and resistor values. Similarly, the second compensation network has the same circuit structure as the compensation network.

[0036] The advantages of the present invention are that the broadband directional coupler provided by the present invention is applicable to high-power directional couplers with a flat coupling coefficient in the full frequency band of 1kHz~500MHz, has low insertion loss and stable use, and still has good performance in the low frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the connection relationship of the broadband directional coupler in the first embodiment of the present invention;

[0038] Figure 2 1 is a schematic diagram of the circuit structure of a broadband directional coupler in the first embodiment of the present invention;

[0039] Figure 3 Schematic diagram of the connection relationship of the compensation network of the broadband directional coupler in the first embodiment of the present invention;

[0040] Figure 4 1 is a schematic structural diagram of a coupling network of a broadband directional coupler in a first embodiment of the present invention;

[0041] Figure 5 Schematic diagram of the connection relationship of the broadband directional coupler in the second embodiment of the present invention;

[0042] Figure 6 1 is a schematic diagram of the circuit structure of a broadband directional coupler in the second embodiment of the present invention;

[0043] Figure 7 1 is a schematic diagram of the circuit structure of a broadband directional coupler in the third embodiment of the present invention;

[0044] Figure 8 Schematic diagram of the connection of the coupling network of the broadband directional coupler in the third embodiment of the present invention during simulation sampling;

[0045] Figure 9 This is the actual measurement result of the insertion loss of the broadband directional coupler of the present invention on a network analyzer;

[0046] Figure 10 This is the actual measurement result of the coupling degree of the broadband directional coupler of the present invention on a network analyzer;

[0047] Figure 11 This is the measured result of the low-frequency isolation of the broadband directional coupler of the present invention;

[0048] Figure 12 This is the compensation network frequency response result of the broadband directional coupler of the present invention during simulation sampling.

[0049] Reference numerals: input port 101 ; output port 102 ; coupling port 103 ; coupling network 104 ; compensation network 105 ; oscilloscope 106 ; isolation port 107 ; resistor integration region 201 ; external conductor connection region 202 ; first through-hole 203 ; second through-hole 204 . DETAILED DESCRIPTION Example 1

[0050] The broadband directional coupler provided in this solution includes an input port 101, an output port 102, a coupling port 103, and a coupling component. The input port 101, the output port 102, and the coupling port 103 are arranged on the coupler housing, and the coupling component is arranged inside the housing, which is a metal housing.

[0051] like Figure 1 As shown, the coupling assembly includes a coupling network 104 and a compensation network 105. The coupling network 104 is connected to the input port 101, the output port 102, and the compensation network, while the compensation network 105 is connected between the coupling port 103 and the coupling network 104. The input port 101, the output port 102, and the coupling port 103 are grounded, respectively. The coupling port 103 can be grounded by connecting to the housing.

[0052] Specifically, if Figure 2 As shown, the coupling network 104 includes a second resistor R2, a third resistor R3 and a fourth resistor R4. For ease of description, the second resistor R2, the third resistor R3 and the fourth resistor R4 are as follows: Figure 2 The end marked with a solid circle is called the input end of the corresponding resistor, and the other end is called the output end of the corresponding resistor.

[0053] The inner conductor of the input cable of the input port 101 is connected to the input end of the second resistor R2 and the output port 102. The output end of the second resistor R2 is connected to the compensation network 105. The outer conductor of the input cable of the input port 101 is connected to the input end of the fourth resistor R4. The output end of the fourth resistor R4 is connected to the output port 102. The input end of the third resistor R3 is connected between the fourth resistor R4 and the output port 102. The output end of the third resistor R3 is connected to the compensation network 105.

[0054] The resistance of the second resistor R2 is preferably a large resistance of several thousand ohms, such as 5000 ohms. The third resistor R3 is preferably a small resistance of several tens of ohms, such as 50 ohms. The fourth resistor R4 is preferably an even smaller resistance, such as 0.5 ohms.

[0055] Specifically, if Figure 3As shown, the compensation network 105 includes a first compensation circuit and a second compensation circuit, wherein the first compensation circuit and the second compensation circuit are connected in series. The first compensation circuit includes a first compensation resistor R11, a second compensation resistor R12, a third compensation resistor R13, a first compensation inductor L1, and a first compensation capacitor C1. The first compensation resistor R11 and the second compensation resistor R12 are connected in series, and the first compensation inductor L1 is connected in parallel with the first compensation resistor R11 and the second compensation resistor R12. The first compensation capacitor C1 is connected between the first compensation resistor R11 and the second compensation resistor R12. The end of the first compensation capacitor C1 away from the first compensation resistor R11 and the second compensation resistor R12 is connected to the third compensation resistor R13. The end of the third compensation resistor R13 away from the first compensation capacitor C1 is grounded.

[0056] The second compensation circuit is a π-type compensation circuit, specifically including a fourth compensation resistor R14, a fifth compensation resistor R15, and a sixth compensation resistor R16. The fifth compensation resistor R15 is connected in series with the first compensation circuit. The fourth compensation resistor R14 is connected between the fifth compensation resistor R15 and the first compensation circuit. The end of the fourth compensation resistor R14 not connected to the fifth compensation resistor R15 is grounded. The end of the fifth compensation resistor R15 away from the first compensation circuit is connected to the sixth compensation resistor R16, and the other end of the sixth compensation resistor R16 is grounded. Figure 3 The port on the left is connected to the coupling port 103, and the port on the right is connected to the resistors R2 and R3.

[0057] Furthermore, if Figure 4 As shown, the fourth resistor R4 is preferably formed by connecting several resistors in parallel. In this embodiment, it is composed of ten 5-ohm resistors connected in parallel. Specifically, the fourth resistor R4 is formed by integrating them into a resistor integration unit. The resistor integration unit includes a resistor integration region 201, an external conductive connection region 202, and a through-hole. The resistor integration region 201 is an annular region composed of ten 5-ohm resistors evenly distributed around the circumference. The ten 5-ohm resistors in the resistor integration region 201 are evenly distributed throughout the annular region. The external conductive connection region 202 is disposed within the annular region and is also annular in structure, coinciding with the central axis of the annular region. The through-hole is used for connecting components. A first through-hole 203 is disposed within the external conductive connection region 202, i.e., the first through-hole 203 is disposed at the center of the annular region, and the outer conductive connection region 202 surrounds the first through-hole 203. A conductive medium is disposed on the outer conductive connection region 202, and the conductive medium in the outer conductive connection region 202 is connected to one end of the ten parallel 5-ohm resistors in the resistor integration region 201, i.e., to the input terminal of the fourth resistor R4. When the outer conductor of the input cable of the input port 101 is connected to the conductive medium on the outer conductor connection area 202, the outer conductor of the input cable is connected to the fourth resistor R4. The ten 5 ohm resistors in the resistor integration area 201 can be chip resistors.

[0058] A 0.5-ohm resistor obtained by connecting ten 5-ohm resistors in parallel is used as resistor R4. On the one hand, the lower resistance value of R4 makes the circuit have better high-frequency characteristics. On the other hand, connecting multiple resistors in parallel can effectively improve the power capacity of the circuit.

[0059] When the outer conductor of the input cable of input port 101 is connected to the conductive medium on the outer conductor connection area 202, the inner conductor of the input cable of input port 101 passes through the first through-hole 203 of the resistor integrated unit. The inner conductor of the input cable passing through the first through-hole 203 is connected to one end of the second resistor R2.

[0060] A second through-hole 204 is provided in the resistor integrated region 201. The line connecting the first through-hole 203 and the second through-hole 204 forms an axis of symmetry for the resistor integrated region 201, referred to as the first axis of symmetry. Five 5-ohm resistors are distributed on each side of the resistor integrated region 201 on either side of the first axis of symmetry. The resistors on the resistor integrated region 201 on either side of the first axis of symmetry are evenly distributed throughout the resistor integrated region 201, thereby enhancing the coupler's high-frequency characteristics. No resistors are provided at positions symmetrical to the second through-hole 204 about the center of the first through-hole 203.

[0061] The output end of the second resistor R2 is connected to the output end of the third resistor R3 via a conductive medium, which connects the output end of the second resistor R2 to the output end of the third resistor R3 by passing through the second through-hole 204. Alternatively, the inner conductor of the input cable of the input port 101 passes through the second through-hole 204 and then connects to the input end of the second resistor R2, which is not specifically limited here. It should be noted that the second resistor R2 generates a lot of heat during operation due to its large resistance. Therefore, when the second resistor R2 is fixed, it is as close to the housing of the coupler as possible to ensure the heat dissipation effect of the second resistor R2. Based on the fixed position of the second resistor R2, it is determined whether the inner conductor of the input cable or the conductive medium connecting the output end of the second resistor R2 and the output end of the third resistor R3 passes through the second through-hole 204.

[0062] The resistor integrated unit is also provided with a fixing hole, which is used to fix the resistor integrated unit in the housing. The specific installation position is not limited here.

[0063] This solution ensures the accuracy of the coupling network 104 through the compensation network 105 and offsets the effect of the distributed parameters on the coupling coefficient, thereby ensuring the flatness of the coupling coefficient over the entire frequency band. Example 2

[0064] like Figure 5 and Figure 6As shown, this embodiment is similar to the first embodiment, except that the coupling component of this embodiment further includes a grounding isolation device, a first grounding isolation device T1 is connected between the coupling network 104 and the output port 102, and a second grounding isolation device T2 is connected between the coupling network 104 and the compensation network 105.

[0065] Specifically, the inner conductor of the input cable of the input port 101 is connected to the input end of the second resistor R2 and the first ground isolation device T1, and the other end of the first ground isolation device T1 is connected to the output port 102. The output end of the second resistor R2 is connected to the second ground isolation device T2.

[0066] The output end of the fourth resistor R4 is connected to the first ground isolation device T1. The input end of the third resistor R3 is connected between the output end of the fourth resistor R4 and the first ground isolation device T1. The output end of the third resistor R3 is connected to the second ground isolation device T2, which is connected to the compensation network. The output end of the second resistor R2 is connected to the output end of the third resistor R3 and then to the second ground isolation device T2. The ground isolation device can be a coaxial choke, a magnetic ring, or other anti-interference component used to suppress noise.

[0067] One end of the compensation network 105 is connected to the second ground isolation device T2 , and the other end is connected to the coupling port 103 .

[0068] The ground isolation device and its setting position proposed in this solution isolate the ground lines of the input port 101, the output port 102, and the coupling port 103, thereby isolating the low-frequency noise. The signal is returned along the outer sheath of the coaxial cable on the main transmission path. At the same time, the reference ground of the coupling port is connected to the metal housing of the coupler. In conjunction with the first embodiment, Figure 4 The coupling network structure shown is adapted to the main transmission line coaxial line and uses component packages with small parasitic parameters. When the frequency is low, the influence of the parasitic parameters on the coupling coefficient can be ignored. However, when the frequency exceeds 100MHz, the coupling coefficient will increase significantly with the increase of frequency. In this regard, the compensation network proposed in this scheme can offset the influence of the distributed parameters on the coupling coefficient, thereby ensuring the flatness of the coupling coefficient in the entire frequency band. Example 3

[0069] like Figure 7 As shown, this embodiment is similar to the second embodiment, except that the broadband directional coupler of this embodiment includes two coupling components connected in a mirror-image relationship with each other, and the first ground isolation device T1 is connected between the two coupling components to achieve the coupling output of the forward pass signal and the reflected signal at the same time. The two coupling components are referred to as the first coupling component and the second coupling component respectively. Figure 7In the figure, the left side is the first coupling component and the right side is the second coupling component.

[0070] The coupling network of the first coupling component is composed of R2, R3, and R4. Correspondingly, the coupling network of the second coupling component is composed of R6, R7, and R9. The second resistor R2 in the first coupling component is mirrored with the sixth resistor R6 in the second coupling component, and has the same value. The fourth resistor R4 in the first coupling component is mirrored with the ninth resistor R9 in the second coupling component, and has the same value. The third resistor R3 in the first coupling component is mirrored with the seventh resistor R7 in the second coupling component, and has the same value. For ease of description, Figure 7 In the figure, corresponding ends of the resistors R6, R7, and R9 corresponding to the second resistor R2, the third resistor R3, and the fourth resistor R4 are also marked with solid circles, and the ends marked with solid circles are also referred to as input ends of the corresponding resistors.

[0071] The first resistor R1 in the first coupling component is the internal resistance of the signal source V1 , the resistor R5 is the internal resistance of the coupling port 103 , the resistor R8 in the second coupling component is the internal resistance of the signal output end, and the resistor R10 is the internal resistance of the isolation port.

[0072] The output end of the first coupling component is connected to the part of the second coupling component corresponding to the output end of the first coupling component, that is, Figure 7 In the example, the input terminals of R2 and R3 are connected to the input terminals of R6 and R7. The portion of the second coupling component corresponding to the input terminal of the first coupling component is connected to output port 102, serving as the output terminal of the coupler. That is, the input terminals of resistor R6 and resistor R9 are connected to output port 102. The compensation network 105 of the second coupling component is connected to the isolation port, serving as the isolation port of the coupler.

[0073] This solution uses a broadband directional coupler with an isolated port for simulation experiments.

[0074] like Figure 8 As shown in the figure, the red arrow represents voltage coupling sampling, and the green arrow represents current coupling sampling. The two converge at the TC point to form a coupled signal.

[0075] The following describes the TC point voltage of the wide directional coupler in the present invention when it is unloaded and loaded:

[0076] R1 is the internal resistance of the signal source V1, R1=50 ohms; R5 is the internal resistance of the coupling port 103, R5=50 ohms; R8 is the internal resistance of the signal output end, R8=50 ohms; R10 is the internal resistance of the isolation port, R10=50 ohms.

[0077] The output voltage of signal source V1 when the load is matched is Vout=0.5*V1.

[0078] When the wide directional coupler is unloaded, S1 is open and the load is much larger than the 50 ohm source impedance, so it can be considered as unloaded. At this time, the current in the loop is very small, and the voltage drop across R4 can be ignored. The voltage at the TC point is:

[0079] VTC=V1*(R5 / / R3) / (R1+R2+R5 / / R3)=V1*25 / 5075=0.004926*V1;

[0080] Relative to the matched load,

[0081] VTC / Vout=0.009852=-40.13dB;

[0082] VTC is the voltage at point TC; Vout is the output voltage of signal source V1 when the load is matched.

[0083] When S1 is closed, the output of the broadband directional coupler is connected to the load. Ignoring the currents on R2 and R6, the current on the main transmission path is:

[0084] IMain=V1 / (R1+R8+R9+R4)=V1 / 101Ω;

[0085] The voltage drop across R4 is V1*R4 / 101Ω=V1*0.5 / 101Ω=0.004950 V1;

[0086] The component of the voltage drop on R4 at point TC is: VTC1=1 / 2*V1*R4 / 101=0.002475;

[0087] The voltage component on the right side of R1 at TC is:

[0088] VTC2=V1*(R8+R9+R4) / (R1+R8+R9+R4)*(R5 / / R3) / (R1+R2+R5 / / R3)=V1*51 / 101*25 / 5075=0.002487*V1;

[0089] VTC=VTC1+VTC2=0.004962*V1;

[0090] Relative to the matched load,

[0091] VTC / Vout=0.009904=-40.08dB;

[0092] IMain is the current on the main transmission path when loaded; VTC1 is the component of the voltage drop across R4 generated at point TC; VTC2 is the component of the voltage to the right of R1 generated at point TC.

[0093] From the above calculation results, it can be seen that when the no-load and load are matched, the coupling coefficient of the TC point is about -40dB.

[0094] Figure 9 、 Figure 10 、 Figure 11 These are the measured results on a network analyzer. Specifically, Figure 9 is the insertion loss on the main transmission path; Figure 10 It is the coupling degree of the coupling port relative to the input port. Since the frequency of the network analyzer cannot reach 1kHz, this test uses an oscilloscope. Figure 11 The isolation of this solution from 50Hz to 500kHz, measured using the Bode plot function of an oscilloscope, confirms the directivity better than 20dB at 1kHz mentioned below. As can be seen, the insertion loss of the directional coupler implemented in this solution is only approximately 0.2dB, the coupling coefficient is around -40dB, and the flatness is better than ±0.2dB. Furthermore, the test results show that this directional coupler maintains good performance at low frequencies, with a directivity better than 20dB at 1kHz, while typical low-loss directional couplers only achieve around 16dB.

[0095] like Figure 12 As shown, the red color is the frequency response of the compensation network insertion loss, and the rose red color is the frequency response of the compensation network input port return loss. The measured value of the coupling coefficient after the compensation network 105 is as follows: Figure 10 As shown, it can be seen that the flatness is better than ±0.2dB at this time, verifying that this scheme can ensure the flatness of the coupling coefficient.

[0096] In summary, the directional coupler provided by this solution has low insertion loss and high stability in the range of 1kHz~500MHz. In particular, it still has good performance in the low frequency band, with a directivity of better than 20dB at 1kHz and excellent flatness in the entire frequency band of 1kHz~500MHz, which is no higher than 0.2dB in the entire frequency band. Even if the input power is 200W, the total loss of the coupler does not exceed 10W. For modules with an aluminum alloy main structure, the heat dissipation pressure is very small. Therefore, a power capacity of 200W can be used to realize a directional coupler with wide bandwidth, low insertion loss and high power capacity. Therefore, the directional coupler of this solution is suitable for application scenarios of 1kHz~500MHz. In addition, this solution avoids the errors introduced by multiple switching of test ports, which facilitates the automated control of the test system.

[0097] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

[0098] Although this document frequently uses terms such as input port 101, output port 102, coupling port 103, coupling network 104, compensation network 105, oscilloscope 106, isolation port 107, resistor integrated region 201, external conductor connection region 202, first through-hole 203, and second through-hole 204, the use of other terms is not excluded. These terms are used solely to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations would be contrary to the spirit of the present invention.

Claims

1. A broadband directional coupler comprising an input port (101), an output port (102), a coupling port (103) and a coupling component, characterized in that: The coupling component includes a first coupling network (104) and a compensation network (105); The first coupling network (104) is connected to the input port (101), the output port (102), and the compensation network (105); The coupling port (103) is connected to the compensation network (105); The input port (101) is connected to an input cable having an inner conductor and an outer conductor; The first coupling network (104) includes a second resistor R2, a third resistor R3 and a fourth resistor R4; The inner conductor of the input cable is connected to one end of the second resistor R2 and the output port (102), and the end of the second resistor R2 away from the input port (101) is connected to the compensation network (105); The outer conductor of the input cable is connected to one end of a fourth resistor R4, the end of the fourth resistor R4 away from the input port (101) is connected to the output port (102), and the fourth resistor R4 and the output port (102) are connected to one end of the third resistor R3, and the end of the third resistor R3 away from the output port (102) is connected to the compensation network (105).

2. The broadband directional coupler according to claim 1, wherein The resistance of the second resistor R2 is 1K-10K ohms, the resistance of the third resistor R3 is 10-100 ohms, and the resistance of the fourth resistor R4 is 0.1-1 ohm.

3. The broadband directional coupler according to claim 2, wherein: The fourth resistor R4 is formed by connecting a plurality of resistors in parallel. The plurality of resistors connected in parallel make the resistance of the fourth resistor R4 be 0.1-1 ohm.

4. The broadband directional coupler according to claim 3, wherein: The first coupling network (104) includes a circuit board and a resistance integration unit arranged on the circuit board, and the resistance integration unit includes a resistance integration area (201) and an external conductive connection area (202); A plurality of resistors constituting the fourth resistor R4 are uniformly arranged circumferentially on the circuit board to form the resistor integration area (201) in a ring shape; The external conductive connection region (202) is located within the annular region of the resistor integrated region (201), and the external conductive connection region (202) is annular in structure, and the annular central axis of the external conductive connection region (202) coincides with that of the resistor integrated region (201); The resistor integrated unit further includes a first through hole (203) and a second through hole (204) provided on the circuit board; The first through hole (203) is opened at the center of the external conductive connection area (202); The second through hole (204) is opened outside the external conductive connection area (202) and inside the resistor integrated area (201) or extends inward from the ring line of the resistor integrated area (201); The central connection line between the first through-hole (203) and the second through-hole (204) coincides with the symmetry axis of the resistor integrated region (201); The outer conductor connection area (202) is electrically connected to the resistor integrated area (201), and the outer conductor is electrically connected to the outer conductor connection area (202), so that the outer conductor is connected to the fourth resistor R4; The inner conductor passes through the first through-hole (203) and is connected to the second resistor R2, and the inner conductor passes through the second through-hole (204) and is connected to the compensation network (105).

5. The broadband directional coupler according to claim 1, wherein: The compensation network (105) comprises a first compensation circuit and a second compensation circuit connected in series; The first compensation circuit includes a first compensation resistor R11 and a second compensation resistor R12 connected in series. The first compensation resistor R11 and the second compensation resistor R12 are connected in parallel with a first compensation inductor L1. A first compensation capacitor C1 is connected between the first compensation resistor R11 and the second compensation resistor R12. An end of the first compensation capacitor C1 away from the first compensation resistor R11 and the second compensation resistor R12 is connected to a third compensation resistor R13. An end of the third compensation resistor R13 away from the first compensation capacitor C1 is grounded. The second compensation circuit is a π-type compensation circuit including a fourth compensation resistor R14 , a fifth compensation resistor R15 , and a sixth compensation resistor R16 .

6. The broadband directional coupler according to claim 1, wherein The input port (101), the output port (102), and the coupling port (103) are all grounded; The resistance of the second resistor R2 is 5k ohms, the resistance of the third resistor R3 is 50 ohms, and the resistance of the fourth resistor R4 is 0.5 ohms.

7. The broadband directional coupler according to claim 6, wherein: The coupling assembly further includes a first grounding isolation device T1 and a second grounding isolation device T2; The first ground isolation device T1 is located between the first coupling network (104) and the output port (102); The second grounding isolation device T2 is located between the first coupling network (104) and the compensation network (105).

8. The broadband directional coupler according to claim 7, wherein: The coupling assembly further comprises a second coupling network, and the first coupling network (104) and the second coupling network are connected to each other in a mirror-symmetrical relationship via the first grounding isolation device T1; The coupling port (103) is connected to the first coupling network (104) through the compensation network (105) and the second ground isolation device T2; The input port (101) is connected to an end of the first coupling network (104) away from the second coupling network, and the output port (102) is connected to an end of the second coupling network away from the first coupling network (104); The second coupling network corresponds to the first coupling network (104) and is used to connect one end of the coupling port (103) to the output port (102) through the second compensation network and the isolation port (107).

9. The broadband directional coupler according to claim 8, wherein: The second coupling network comprises a sixth resistor R6, a seventh resistor R7, and a ninth resistor R9, which are mirror-symmetrical to the second resistor R2, the third resistor R3, and the fourth resistor R4 of the first coupling network (104), respectively, and the first coupling network (104) and the second coupling network have the same network structure and resistance values.

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