A cavity coupler

Abstract

The present invention provides a cavity coupler, including a main body, and a coupling structure and an active compensation circuit fixedly connected to the main body via a printed circuit board. The main body is a shell having a cavity inside, and an inner conductor penetrating the cavity is arranged inside the main body; the coupling structure is a metal conductor arranged inside the cavity and fixedly connected to the printed circuit board; the active compensation circuit includes a passive compensation network and an active amplification circuit, and the active compensation circuit adjusts the first coupling coefficient with a span value greater than 60dB output by the coupling structure to a second coupling coefficient with a fixed value A and a flatness of ±1dB. The present invention provides a cavity coupler, which realizes a high-power ultra-wideband directional coupler of 1MHz~1.2GHz by using a weak coupling method with an active compensation circuit. At the same time, an active amplification circuit is added after the passive compensation network to reduce the complexity of the passive compensation network.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency communication technology, and more specifically, to a cavity 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, thereby achieving the purpose of online monitoring of forward transmission power and reflected power.

[0003] In medium and high power RF measurement systems, in order to reduce the insertion loss on the main transmission path, the coupling coefficient of the directional coupler is usually small, generally between -60dB and -40dB. The cavity structure directional coupler has the characteristics of large power capacity, good directivity, and small main line insertion loss, and has been widely used. Since the coupling coefficient of the coupling structure output of the cavity directional coupler increases by 6dB per octave, the bandwidth of high-power directional couplers on the market is generally less than 50 octaves, which means that if the working bandwidth of the coupler is to cover 1MHz~1.2GHz, it usually requires more than 2 coupler combinations, such as splitting into two modules of 1MHz~30MHz and 25MHz~1.2GHz, which brings a lot of inconvenience and more measurement uncertainty to users.

[0004] Therefore, the problems existing in the prior art need to be further improved and developed. Summary of the invention

[0005] (I) Purpose of the invention: In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a cavity coupler, which adjusts the first coupling coefficient with a coupling structure span value greater than 60dB to a second coupling coefficient close to a fixed value with a flatness of ±1dB, so as to facilitate access to the existing system and realize a high-power ultra-wideband directional coupler of 1MHz~1.2GHz.

[0006] (II) Technical solution: In order to solve the above technical problems, the present technical solution provides a cavity coupler, comprising a main body, and a coupling structure and an active compensation circuit fixedly connected to the main body through a printed circuit board, wherein the main body is a shell having a cavity inside, and an inner conductor penetrating the cavity is arranged inside the main body; the coupling structure is a metal conductor arranged inside the cavity and fixedly connected to the printed circuit board;

[0007] The active compensation circuit includes a passive compensation network and an active amplification circuit, and the active compensation circuit adjusts the first coupling coefficient output by the coupling structure with a span value greater than 60 dB to a second coupling coefficient with a fixed value A and a flatness of ±1 dB;

[0008] The output of the coupling structure is connected to the passive compensation network, which includes a plurality of LCR circuits connected in series, each LCR circuit being a parallel circuit composed of a capacitor, an inductor, and a resistor in parallel. By adjusting the values ​​of the capacitor, the inductor, and the resistor, the signal is adjusted in turn when passing through each adjustment module to adjust the coupling coefficient. The passive compensation network adjusts the first coupling coefficient whose span value is greater than 60 dB output by the coupling structure to a coupling coefficient that fits the fixed value A;

[0009] The output of the passive compensation network is connected to the input of the active amplifier circuit, and the active amplifier circuit includes a low-noise broadband amplifier module and a power supply module; the active amplifier circuit adjusts the coupling coefficient of the fixed value A output by the passive compensation network to a flatness of ±1dB.

[0010] A cavity coupler, wherein both ends of the main body have openings, support seats are provided at the openings at both ends of the main body, the inner conductor passes through the cavity and both ends of the inner conductor are fixed and pass through the support seats, the support seats at both ends of the main body are respectively connected to an input port and an output port, and the cavity and the inner conductor between the input port and the output port constitute an air dielectric transmission line with a characteristic impedance of 50 ohms.

[0011] A cavity coupler, wherein the main body is made of hard aluminum alloy, the diameter of the cavity is 23.5 mm, the diameter of the inner conductor is 10 mm, and the support seat is made of polytetrafluoroethylene.

[0012] A cavity coupler, wherein the printed circuit board is a high-frequency printed circuit board, the coupling structure and the active compensation circuit are fixedly connected to the printed circuit board by welding; the coupling structure is in an arc or rectangular shape, and the material of the coupling structure is gold-plated copper or silver-plated copper.

[0013] A cavity coupler, wherein the adjustment range of the capacitance value in the LCR circuit is 1pF to 1nF, the adjustment range of the inductance value in the LCR circuit is 10nH to 3.3uH, and the adjustment range of the resistance value in the LCR circuit is 10 ohms to 2k ohms.

[0014] A cavity coupler, wherein a matching resistor is fixedly connected to the printed circuit board, the matching resistor is connected to the coupling structure to ensure the matching of the signal during transmission; the rated power of the matching resistor is 10W.

[0015] A cavity coupler, wherein the span range of the first coupling coefficient is -85dB~-22dB, and the numerical range of the fixed value A of the second coupling coefficient is -63dB~-50dB.

[0016] A cavity coupler, wherein the low-noise broadband amplification module is a low-noise transistor or an integrated circuit, comprising a radio frequency input port and a radio frequency output port, a signal is input into the low-noise broadband amplification module from the radio frequency input port, and is output through the radio frequency output port after amplification.

[0017] A cavity coupler, wherein the active compensation circuit is provided with a power processing module, the power processing module is a circuit composed of a magnetic bead, a filter inductor, and a low-noise low-voltage dropout linear regulator connected in series, and provides a stable power supply voltage and bias voltage for the active amplifier circuit; the magnetic bead presents high impedance to high-frequency current and low impedance to low-frequency current, and suppresses high-frequency noise on the power line; the low-noise low-voltage dropout linear regulator stably outputs the input power supply voltage as a constant voltage;

[0018] The low-noise low-voltage dropout linear regulator includes an input terminal, an output terminal, a ground terminal, a control terminal and a bypass capacitor connection point; the input terminal receives an input voltage from a power supply, the output terminal provides a stable output voltage to a load, the ground terminal provides a reference potential for the low-noise low-voltage dropout linear regulator, the control terminal is used to control the on and off of the low-noise low-voltage dropout linear regulator, and the bypass capacitor connection point is connected to a bypass capacitor and grounded to filter out high-frequency noise and interference at the output terminal of the low-noise low-voltage dropout linear regulator.

[0019] A cavity coupler, wherein in the active compensation circuit, a coupling coefficient adjustment module is arranged after the active amplification circuit, and the coupling coefficient adjustment module is a T-type attenuation network with a three-resistance series-parallel structure, or a Pi-type attenuation network with a three-resistance series-parallel structure; a fixed attenuator is arranged between the coupling structure and the passive compensation network.

[0020] (III) Beneficial effects: The present invention provides a cavity coupler, which adjusts the first coupling coefficient of the coupling structure with a span value greater than 60dB to a fixed value and a second coupling coefficient with a flatness of ±1dB through a weak coupling method with an active compensation circuit, thereby realizing a high-power ultra-wideband directional coupler of 1MHz~1.2GHz. At the same time, an active amplifier circuit is added to the passive compensation network. The gain of the active amplifier circuit is large at low frequencies, and the gain decreases as the frequency increases. This is complementary to the fact that the coupling coefficient of the coupling structure increases with the frequency, which can reduce the complexity of the passive compensation network. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic cross-sectional structure diagram of a cavity coupler of the present invention;

[0022] Figure 2It is a frequency response curve diagram of a first coupling coefficient output by a coupling structure in a simulation model of a cavity coupler of the present invention;

[0023] Figure 3 It is a schematic diagram of the principle of an active compensation circuit of a cavity coupler of the present invention;

[0024] Figure 4 It is a typical structural schematic diagram of the passive compensation network of the present invention;

[0025] Figure 5 It is a typical structural schematic diagram of the active amplifier circuit of the present invention;

[0026] Figure 6 It is a typical structural schematic diagram of the power processing module of the present invention;

[0027] Figure 7 It is a typical structural schematic diagram of the coupling coefficient adjustment module of the present invention;

[0028] Figure 8 It is a schematic diagram of the principle of an active compensation circuit with a fixed attenuator of a cavity coupler of the present invention;

[0029] Fig. 9 It is a frequency response curve diagram of a second coupling coefficient output by an active amplifier circuit in a simulation model of a cavity coupler of the present invention;

[0030] Figure numbers: 1-main body, 2-coupling structure, 3-active compensation circuit, 4-printed circuit board, 5-matching resistor, 11-cavity, 12-support base, 13-inner conductor, 14-input port, 15-output port. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with preferred embodiments. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0032] The accompanying drawings are schematic diagrams of embodiments of the present invention. It should be noted that the drawings are only examples and are not drawn to scale, and should not be used to limit the actual protection scope of the present invention.

[0033] Medium and high power measurement systems usually require the coupling coefficient of the coupler to be relatively fixed and have a small fluctuation value; however, the coupling coefficient of the high power 1MHz~1.2GHz coupler has a large span, usually exceeding 60dB, and cannot be applied in the existing measurement system. Only by adjusting the original coupling coefficient with a large span to a relatively fixed value with a small fluctuation, such as -60dB±1dB, can it be connected to the existing system, where ±1dB represents the fluctuation of the coupling coefficient, that is, flatness; -60dB±1dB means that the coupling coefficient is relatively fixed at -60dB, and its fluctuation is less than or equal to 1dB.

[0034] The present invention provides a cavity coupler, such as Figure 1 As shown, it includes a main body 1, and a coupling structure 2 and an active compensation circuit 3 fixedly connected to the main body 1 through a printed circuit board (PCB) 4.

[0035] Preferably, the main body 1 is a shell having a cavity 11 inside, and the two ends of the main body 1 have openings, and support seats 12 are arranged at the openings at the two ends of the main body 1, and an inner conductor 13 penetrating the cavity 11 is arranged inside the main body 1, and the two ends of the inner conductor 13 are fixed and penetrated on the support seat 12. Preferably, the main body 1 of the present invention can be a cylindrical shell, the material of the main body 1 is hard aluminum alloy, the diameter of the cavity 11 is 23.5mm, the diameter of the inner conductor 13 is 10mm, and the material of the support seat 12 is polytetrafluoroethylene; the support seats 12 at the two ends of the main body 1 of the present invention are respectively connected to the input port 14 and the output port 15, and the cavity 11 and the inner conductor 13 between the input port 14 and the output port 15 constitute an air dielectric transmission line with a characteristic impedance of 50 ohms, and serve as the main transmission path.

[0036] The radio frequency signal is input into the cavity coupler of the present invention from the input port 14 and output from the output port 15 , wherein the coupling structure 2 can extract a part of the input signal for monitoring the signal.

[0037] Preferably, in the present invention, the printed circuit board 4 may be a high-frequency printed circuit board.

[0038] Preferably, a printed circuit board 4 is disposed on the side of the cavity 11 of the main body 1, and a coupling structure 2 is fixedly connected to one side of the printed circuit board 4 facing the cavity 11, and an active compensation circuit 3 is fixedly connected to the other side. Preferably, the coupling structure 2 and the active compensation circuit 3 are fixedly connected to the printed circuit board 4 by welding.

[0039] Preferably, the coupling structure 2 is a metal conductor arranged inside the cavity 11 and fixedly connected to the printed circuit board 4, and the coupling structure 2 is not in direct contact with the inner conductor 13. The coupling structure 2 is in an arc or rectangular shape, and the material of the coupling structure 2 is gold-plated copper or silver-plated copper. The coupling coefficient output by the coupling structure 2 of the present invention is a first coupling coefficient, and the first coupling coefficient increases with the increase of the operating frequency in the range of -85dB to -22dB.

[0040] A cavity coupler of the present invention is simulated using simulation software. In the simulation model, the frequency response curve of the first coupling coefficient output by the coupling structure 2 is as follows: Figure 2 As shown, the horizontal axis in the figure is the operating frequency of a cavity coupler of the present invention, the unit is Hz, and it is displayed in a logarithmic manner; the vertical axis is the coupling coefficient output by the coupling structure 2, the unit is dB, and it is displayed in a logarithmic manner. Five marking points are selected from the operating frequency, namely the first marking point m1, the second marking point m2, the third marking point m3, the fourth marking point m4, and the fifth marking point m5. The operating frequency of the first marking point m1 is 1.000MHz, the operating frequency of the second marking point m2 is 1.600MHz, the operating frequency of the third marking point m3 is 10.00MHz, the operating frequency of the fourth marking point m4 is 100.0MHz, and the operating frequency of the fifth marking point m5 is 1.200GHz. It can be seen from the figure that when the working frequency is 1.000MHz, the coupling coefficient output by the coupling structure 2 is -84.576dB, when the working frequency is 1.600MHz, the coupling coefficient output by the coupling structure 2 is -80.494dB, when the working frequency is 10.00MHz, the coupling coefficient output by the coupling structure 2 is -64.577dB, when the working frequency is 100.0MHz, the coupling coefficient output by the coupling structure 2 is -44.577dB, and when the working frequency is 1.200GHz, the coupling coefficient output by the coupling structure 2 is -22.992dB. It can be seen from the figure that the first coupling coefficient output by the coupling structure 2 is roughly in the range of -85dB~-22dB and shows an upward trend with the increase of the working frequency.

[0041] Preferably, the printed circuit board 4 is also fixedly connected with a matching resistor 5, and the matching resistor 5 is connected to the coupling structure 2, which is used to further optimize the performance of the circuit and ensure the matching of the signal during the transmission process, which can effectively reduce the reflection and loss of the signal and improve the overall transmission efficiency. Preferably, the resistance value of the matching resistor 5 is 50 ohms and the rated power is 10W. More preferably, a resistor heat sink is installed on the matching resistor 5, and the resistor heat sink is fixed between the printed circuit board 4 and the outer shell of the main body 1 by screws, which accelerates the heat dissipation by increasing the heat exchange area between the resistor and the surrounding environment, thereby keeping the temperature of the resistor within a safe range.

[0042] In medium and high power RF measurement systems, the typical value of the power on the main transmission path is 1kW. The insertion loss introduced by coupling structure 2 mainly includes three parts: mismatch loss, transmission loss and coupling loss. The maximum frequency of the directional coupler with cavity structure is within 1.2GHz, the standing wave can be within 1.05, and the sum of transmission loss and mismatch loss is less than 0.05dB. If the total insertion loss is required to be no higher than 0.1dB, the coupling loss of coupling structure 2 must be less than 0.05dB. Figure 2 It can be seen from the frequency response curve that the higher the frequency, the greater the coupling coefficient and coupling loss. If the design power capacity of the directional coupler at the highest operating frequency is 1kW, according to design experience, the coupling coefficient should not exceed -22dB when the highest operating frequency is 1.2GHz. At this time, the output power of the coupling structure 2 is 5W, and the matching resistor 5 also consumes 5W of power, and the total coupling loss is 10W.

[0043] Preferably, the active compensation circuit 3 is as follows: Figure 3 As shown, it includes a passive compensation network and an active amplifying circuit. The output of the coupling structure 2 is connected to the input of the passive compensation network, and the output of the passive compensation network is connected to the input of the active amplifying circuit. The active compensation circuit is used to adjust the first coupling coefficient with a span value greater than 60dB output by the coupling structure 2 to a second coupling coefficient that fits a fixed value A and a flatness of ±1dB, that is, the coupling coefficient finally output by the cavity coupler of the present invention. The passive compensation network preliminarily adjusts the change of the coupling coefficient, and the active amplifying circuit compensates for the change of the coupling coefficient of the coupling structure 2 through the characteristic that its gain changes with frequency, thereby ensuring the stability of the coupling coefficient in the entire frequency band. The second coupling coefficient output by the active compensation circuit 3 gradually fits the fixed value A, with a flatness of ±1dB, and the numerical range of A is -63dB~-50dB. In a specific embodiment of the present invention, the fixed value A of the second coupling coefficient output by the active compensation circuit 3 is A=-60dB, and the flatness is ±1dB.

[0044] Preferably, the passive compensation network includes a plurality of LCR circuits connected in series, each LCR circuit is a parallel circuit composed of a capacitor, an inductor, and a resistor in parallel, and the values ​​of the capacitor, the inductor, and the resistor can be adjusted. By adjusting the values ​​of the capacitor, the inductor, and the resistor, the signal is adjusted in turn when passing through each adjustment module, and the coupling coefficient is gradually adjusted. The passive compensation network is used to adjust the first coupling coefficient of the coupling structure output with a span value greater than 60dB to a coupling coefficient that fits the fixed value A.

[0045] Preferably, the adjustment range of the capacitance value in the LCR circuit is 1pF to 1nF, the adjustment range of the inductance value in the LCR circuit is 10nH to 3.3uH, and the adjustment range of the resistance value in the LCR circuit is 10 ohms to 2k ohms.

[0046] A first preferred embodiment of the present invention is as follows Figure 4 As shown, the passive compensation network includes a first LCR circuit LCR1, a second LCR circuit LCR2 and a third LCR circuit LCR3 connected in series between a first input port IN1 and a first output port OUT1, wherein the first LCR circuit LCR1, the second LCR circuit LCR2 and the third LCR circuit LCR3 are parallel circuits composed of capacitors, inductors and resistors in parallel, and the values ​​of the capacitors, inductors and resistors can be adjusted. A resistor-capacitor grounding branch is arranged after each LCR circuit, and the resistor-capacitor grounding branch is a branch composed of capacitors and resistors connected in series to ground. Specifically, a first resistor-capacitor grounding branch LC1 is arranged after the first LCR circuit LCR1, a second resistor-capacitor grounding branch LC2 is arranged after the second LCR circuit LCR2, and a third resistor-capacitor grounding branch LC3 is arranged after the third LCR circuit LCR3. More preferably, an additional resistor R1 is also arranged between the first input port IN1 and the first LCR circuit LCR1.

[0047] In this embodiment, the first LCR circuit LCR1, the second LCR circuit LCR2 and the third LCR circuit LCR3 are connected in series between the first input port IN1 and the first output port OUT1. This series structure allows the signal to be adjusted in sequence when passing through each adjustment module, thereby gradually adjusting the coupling coefficient.

[0048] In this embodiment, each LCR circuit is composed of a capacitor, an inductor and a resistor in parallel. This parallel structure enables the capacitor, the inductor and the resistor to function independently, and by adjusting their values, the impedance characteristics of the module and the energy storage and consumption mode can be changed, thereby affecting the coupling coefficient.

[0049] In this embodiment, an additional resistor R1 is provided between the first input port IN1 and the first LCR circuit LCR1. The additional resistor R1 can play the role of current limiting, voltage dividing, etc., further adjust the characteristics of the input signal, and provide suitable input conditions for the subsequent LCR circuit. The resistance value of the additional resistor R1 can be adjusted.

[0050] In this embodiment, the input signal enters from the first input port IN1, and first passes through the additional resistor R1 for preliminary current and voltage adjustment. Then, the signal passes through the first LCR circuit LCR1, the second LCR circuit LCR2 and the third LCR circuit LCR3 in sequence. In each module, the parallel combination of capacitors, inductors and resistors adjusts the signal according to its specific parameter values, changes the impedance, energy distribution and phase characteristics of the signal, thereby affecting the coupling coefficient. By adjusting the values ​​of the capacitors, inductors and resistors in these modules, the coupling coefficient can be adjusted from a state with a large span to a relatively flat state.

[0051] The active amplifier circuit is mainly composed of a low-noise broadband amplifier module and a power supply module, and its function is to amplify the smaller signal output by the passive compensation network to a suitable power. The active amplifier circuit has the characteristics of high low-frequency gain and low high-frequency gain, and is complementary to the coupling coefficient output by the coupling structure 2, and can be combined to reduce the complexity of the passive compensation network. The active amplifier circuit is used to adjust the coupling coefficient of the fixed value A output by the passive compensation network to a flatness of ±1dB.

[0052] A second preferred embodiment of the present invention is as follows Figure 5 As shown, the active amplifier circuit is mainly composed of a low-noise broadband amplifier module LNA and a power supply module V. The signal enters the active amplifier circuit from the second input port IN1 of the active amplifier circuit through the first output port OUT1 of the passive compensation network. The power supply module V provides a stable DC power supply for the low-noise broadband amplifier module LNA and other circuit elements. The main function of the low-noise broadband amplifier module LNA is to amplify the input weak RF signal while reducing the noise introduced by itself as much as possible. The low-noise broadband amplifier module LNA can be a low-noise transistor or an integrated circuit. The low-noise broadband amplifier module LNA has a RF input port RF-IN and a RF output port RF-OUT. The signal is input into the low-noise broadband amplifier module LNA from the RF input port RF-IN and output through the RF output port RF-OUT after amplification. The low-noise broadband amplifier module LNA is provided with a plurality of ground pins. Figure 5 The low-noise broadband amplifier module LNA shown in FIG. 1 has two ground pins, a first ground pin G1 and a second ground pin G2 .

[0053] Preferably, in this embodiment, an impedance matching circuit is integrated inside the low-noise broadband amplifier module LNA. The impedance matching circuit is a simple circuit structure composed of an inductor and a capacitor, and can achieve matching of a specific impedance.

[0054] Preferably, in this embodiment, a radio frequency choke RFC is further provided between the power supply module and the low noise broadband amplifier module LNA to prevent radio frequency interference signals from entering the power supply module, thereby ensuring the stability and purity of the power supply.

[0055] Preferably, in order to improve the stability of the active amplifier circuit, a power supply processing module is further provided in the active compensation circuit 3 to provide a stable power supply voltage and bias voltage for the active amplifier circuit. The power supply processing module is a circuit composed of a magnetic bead, a filter inductor, a low-noise low-dropout linear regulator (Low Dropout Regulator, LDO) and the like in series, which converts an external DC power supply into a low-noise, amplitude-stable power supply to power the amplifier circuit.

[0056] A third preferred embodiment of the present invention is as follows Figure 6 As shown, the power processing module is a circuit composed of a filter inductor L1, a magnetic bead FB and a low-noise low-dropout linear regulator LDO in series. The filter inductor L1 mainly attenuates noise of a specific frequency, and can reduce ripple and noise in the power supply through the energy storage and filtering effects of the inductor. The magnetic bead FB is an electronic component made of ferrite material, which presents high impedance to high-frequency current and low impedance to low-frequency current. When high-frequency noise current passes through the magnetic bead, the magnetic bead will generate a magnetic field, which will hinder the passage of high-frequency noise current, thereby converting the high-frequency noise into heat energy and consuming it. In this way, the magnetic bead can effectively suppress the high-frequency noise on the power line and improve the power quality of the low-noise broadband amplifier module LNA.

[0057] The low-noise low-voltage dropout linear regulator LDO is the core part of the power processing module, which can stably output the input power supply voltage as a lower and constant voltage. In this embodiment, the low-noise low-voltage dropout linear regulator LDO preferably includes an input terminal IN, an output terminal OUT, a ground terminal GND, a control terminal / SHDN and a bypass capacitor connection point BP. The input terminal IN receives the input voltage from the power supply, the output terminal OUT provides a stable output voltage to the load, the ground terminal GND provides a reference potential for the low-noise low-voltage dropout linear regulator LDO, and the control terminal / SHDN is used to control the opening and closing of the low-noise low-voltage dropout linear regulator LDO. When the control terminal / SHDN is at a low level, the low-noise low-voltage dropout linear regulator LDO is turned off and the output voltage is zero; when the control terminal / SHDN is at a high level, the low-noise low-voltage dropout linear regulator LDO is turned on and the output voltage is normal. The bypass capacitor connection point BP is connected to a bypass capacitor and grounded, that is, a capacitor is connected in series between the capacitor connection point BP and the ground to filter out high-frequency noise and interference at the output end of the low-noise low-dropout linear regulator LDO.

[0058] Preferably, the power supply of the power supply module is input into the power processing module through the voltage input port VIN, converted into a low-noise, amplitude-stable power supply through the filter inductor L1, the magnetic bead FB and the low-noise low-dropout linear regulator LDO, and output through the voltage output port VCC to power the amplifier circuit.

[0059] Preferably, in the power processing module, the voltage input port VIN, the voltage output port VCC, the filter inductor L1, the magnetic bead FB and the low-noise low-dropout linear regulator LDO, a capacitor grounding branch is connected between every two adjacent components, that is, a capacitor is connected in series between the component and the ground, which provides a low-resistance loop for the AC noise signal in the power supply.

[0060] Due to the influence of the processing accuracy of the cavity coupler and the discrete type of device parameters, the coupling coefficient adjusted by the passive compensation network and the active amplifier circuit has a certain deviation from the expected value. Preferably, a coupling coefficient adjustment module can be set after the active amplifier circuit to fine-tune the output of the active amplifier circuit to ensure that the coupling coefficient at the output port of the coupler of the present invention is close to a fixed value and meets the flatness requirement of ±1dB.

[0061] Preferably, the coupling coefficient adjustment module of the present invention is composed of an attenuation network, which fine-tunes the coupling coefficient to reduce fluctuations introduced by differences in component parameters, so that the coupling coefficients of cavity couplers produced in the same batch are consistent, and the value of the resistor in the attenuation network can be adjusted.

[0062] Preferably, Figure 7As shown, the coupling coefficient adjustment module can be a T-type attenuation network with a three-resistance series-parallel structure, or a Pi-type attenuation network with a three-resistance series-parallel structure, and the present invention does not limit this.

[0063] The present invention is preferably, Figure 8 As shown, since the output power of the coupling structure is relatively large, a fixed attenuator can be added between the coupling structure 2 and the passive compensation network to match the rated power of the active compensation circuit 3 and optimize the distribution of the coupling power. By introducing a fixed attenuator in the circuit to consume part of the energy of the input signal, the attenuation control of the signal is achieved. The fixed attenuator can reduce the output power of the coupling structure 2 and increase the flexibility of the passive compensation network in selecting LCR devices.

[0064] In a fourth preferred embodiment of the present invention, the active compensation circuit 3 adjusts the first coupling coefficient -85dB to -22dB with a span value greater than 60dB output by the coupling structure 2 to a second coupling coefficient close to a fixed value -60dB with a flatness of ±1dB. In a simulation model of a cavity coupler of the present invention, the frequency response curve of the second coupling coefficient output by the active compensation circuit 3 is as follows: Fig. 9 As shown, the horizontal axis of the figure is the operating frequency of a cavity coupler of the present invention, in Hz, and is displayed in a logarithmic manner; the vertical axis is the coupling coefficient output by the active compensation circuit 3, in dB, and is displayed in a logarithmic manner. Figure 2 , select 5 marking points in the working frequency, namely the first marking point m1, the second marking point m2, the third marking point m3, the fourth marking point m4, and the fifth marking point m5. The working frequency of the first marking point m1 is 1.000MHz, the working frequency of the second marking point m2 is 1.600MHz, the working frequency of the third marking point m3 is 10.00MHz, the working frequency of the fourth marking point m4 is 100.0MHz, and the working frequency of the fifth marking point m5 is 1.200GHz. Figure 5 It can be seen that when the operating frequency is 1.000MHz, the coupling coefficient output by the active compensation circuit 3 is -60.791dB, when the operating frequency is 1.600MHz, the coupling coefficient output by the active compensation circuit 3 is -59.177dB, when the operating frequency is 10.00MHz, the coupling coefficient output by the active compensation circuit 3 is -59.717dB, when the operating frequency is 100.0MHz, the coupling coefficient output by the active compensation circuit 3 is -59.503dB, and when the operating frequency is 1.200GHz, the coupling coefficient output by the active compensation circuit 3 is -59.175dB. The second coupling coefficient output by the active compensation circuit 3 is basically maintained within the range of the fitted fixed value -60dB and the flatness ±1dB.

[0065] The present invention provides a cavity coupler, which realizes a high-power ultra-wideband directional coupler of 1MHz~1.2GHz through a weak coupling method with an active compensation circuit. At the same time, an active amplifier circuit is added after the passive compensation network. The gain of the active amplifier circuit is large at low frequencies, and the gain decreases as the frequency increases. This is complementary to the increase in the coupling coefficient of the coupling structure as the frequency increases, which can reduce the complexity of the passive compensation network.

[0066] The above content is an explanation of the preferred embodiments of the present invention, which can help those skilled in the art to more fully understand the technical solution of the present invention. However, these embodiments are merely illustrative, and it cannot be determined that the specific implementation methods of the present invention are limited to the description of these embodiments. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and transformations can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A cavity coupler, characterized in that: The invention comprises a main body, a coupling structure and an active compensation circuit fixedly connected to the main body through a printed circuit board, wherein the main body is a shell having a cavity inside, and an inner conductor penetrating the cavity is arranged inside the main body; the coupling structure is a metal conductor arranged inside the cavity and fixedly connected to the printed circuit board; The active compensation circuit includes a passive compensation network and an active amplification circuit, and the active compensation circuit adjusts the first coupling coefficient output by the coupling structure with a span value greater than 60 dB to a second coupling coefficient with a fixed value A and a flatness of ±1 dB; The output of the coupling structure is connected to the passive compensation network, which includes a plurality of LCR circuits connected in series, each LCR circuit being a parallel circuit composed of a capacitor, an inductor, and a resistor in parallel, and by adjusting the values ​​of the capacitor, the inductor, and the resistor, the signal is adjusted in turn when passing through each adjustment module, and the passive compensation network adjusts the first coupling coefficient of the coupling structure output having a span value greater than 60 dB to a coupling coefficient that fits a fixed value A; the passive compensation network includes a first LCR circuit, a second LCR circuit, and a third LCR circuit connected in series between a first input port and a first output port, and a resistor-capacitor grounding branch is arranged after each LCR circuit, and the resistor-capacitor grounding branch is a branch composed of a capacitor and a resistor connected in series to ground, and an additional resistor is also arranged between the first input port and the first LCR circuit; The output of the passive compensation network is connected to the input of the active amplifier circuit, and the active amplifier circuit includes a low-noise broadband amplifier module and a power supply module; The low-noise broadband amplification module has a radio frequency input port and a radio frequency output port. The signal is input into the low-noise broadband amplification module from the radio frequency input port and output through the radio frequency output port after amplification. The low-noise broadband amplification module is provided with a plurality of ground pins. An impedance matching circuit is also integrated inside the low-noise broadband amplification module. The impedance matching circuit is composed of an inductor and a capacitor. A radio frequency choke is also provided between the power supply module and the low-noise broadband amplification module. The active amplification circuit adjusts the coupling coefficient of the fixed value A output by the passive compensation network to a flatness of ±1dB.

2. A cavity coupler according to claim 1, characterized in that: The main body has openings at both ends, and support seats are arranged at the openings at both ends of the main body. The inner conductor passes through the cavity and the two ends of the inner conductor are fixed and pass through the support seats. The support seats at both ends of the main body are respectively connected to the input port and the output port.

3. A cavity coupler according to claim 2, characterized in that: The material of the main body is hard aluminum alloy, the diameter of the cavity is 23.5 mm, the diameter of the inner conductor is 10 mm, and the material of the support seat is polytetrafluoroethylene.

4. A cavity coupler according to claim 1, characterized in that: The printed circuit board is a high-frequency printed circuit board, and the coupling structure and the active compensation circuit are fixedly connected to the printed circuit board by welding; the coupling structure is in an arc or rectangle shape, and is made of gold-plated copper or silver-plated copper.

5. The cavity coupler according to claim 1, characterized in that: The adjustment range of the capacitance value in the LCR circuit is 1pF to 1nF, the adjustment range of the inductance value in the LCR circuit is 10nH to 3.3uH, and the adjustment range of the resistance value in the LCR circuit is 10 ohms to 2k ohms.

6. A cavity coupler according to claim 1, characterized in that: A matching resistor is fixedly connected to the printed circuit board, and the rated power of the matching resistor is 10W.

7. The cavity coupler according to claim 1, characterized in that: The span range of the first coupling coefficient is -85dB~-22dB, and the numerical range of the fixed value A of the second coupling coefficient is -63dB~-50dB.

8. The cavity coupler according to claim 1, characterized in that: The low-noise broadband amplification module is a low-noise transistor or an integrated circuit.

9. The cavity coupler according to claim 1, characterized in that: The active compensation circuit is provided with a power processing module, which is a circuit composed of a magnetic bead, a filter inductor, and a low-noise low-voltage dropout linear regulator connected in series, and provides a stable power supply voltage and bias voltage for the active amplifier circuit; The low-noise low-voltage dropout linear regulator includes an input terminal, an output terminal, a ground terminal, a control terminal and a bypass capacitor connection point; the input terminal receives an input voltage from a power supply, the output terminal provides a stable output voltage to a load, the ground terminal provides a reference potential for the low-noise low-voltage dropout linear regulator, the control terminal controls the on and off of the low-noise low-voltage dropout linear regulator, and the bypass capacitor connection point is connected to a bypass capacitor and grounded to filter out high-frequency noise and interference at the output terminal of the low-noise low-voltage dropout linear regulator.

10. The cavity coupler according to claim 1, characterized in that: In the active compensation circuit, a coupling coefficient adjustment module is arranged after the active amplification circuit, and the coupling coefficient adjustment module is a T-type attenuation network with a 3-resistance series-parallel structure, or a Pi-type attenuation network with a 3-resistance series-parallel structure; a fixed attenuator is arranged between the coupling structure and the passive compensation network.

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