Ferrite and solid state combined amplitude limiting circuit and high-power microwave front door protection device

Abstract

The invention discloses a ferrite and solid state combined amplitude limiting circuit and a high-power microwave front door protection device, and belongs to the field of microwave devices.The combined amplitude limiting circuit comprises a ferrite substrate, and a ferrite amplitude limiting circuit and a solid state amplitude limiting circuit which are connected with each other are arranged on the front face of the ferrite substrate. The solid-state amplitude limiting circuit comprises two amplitude limiting diodes and two transmission lines, an inductor is arranged between the two transmission lines, one amplitude limiting diode is connected with an output transmission line, and the other amplitude limiting diode is connected with the output of the microstrip amplitude limiting circuit through the transmission line; the high-power microwave front door protection device has high power capacity (hundred kW magnitude), fast response and recovery time (several ns) and high amplitude limiting isolation (higher than 32 dB) in the HPM electromagnetic environment, the ideal high-power microwave front door comprehensive protection effect is achieved, the size of the device is small, and the device can be applied to microwave receiver strong electromagnetic pulse engineering protection.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave devices, and in particular to a ferrite and solid-state combined limiter circuit and a high-power microwave front door protection device composed of the same. Background Art

[0002] High-power microwave (HPM) is an electromagnetic pulse electromagnetic wave with a short duration, a narrow frequency band, and a high peak power. The average power of the electromagnetic pulse exceeds 1 MW, or the peak power exceeds 100 MW, and the frequency range is 300 MHz to 300 GHz.

[0003] A microwave receiver is a device for receiving communication signals, mainly composed of an antenna, a filter, a low-noise amplifier, a mixer, an analog-to-digital converter, etc. Among them, semiconductor devices such as low-noise amplifiers and mixers are sensitive to power and are easily burned out by the narrow-spectrum HPM received by the antenna. In order to protect the sensitive circuit devices at the front end of the receiver, HPM protection is required for the front end of the receiver.

[0004] At present, the HPM front door protection technologies mainly include energy selective surface technology, plasma limiter technology, solid-state limiter technology, and ferrite limiter technology. The energy selective surface is based on the antenna limiter idea. This technology has a large insertion loss when applied at high frequencies and also affects the insertion loss of the transmitting link at the same time. The plasma limiter has a high power capacity, but the recovery time is as long as the μs level and the volume is relatively large. The solid-state limiter has a fast response speed and good integration, but the power it can withstand is limited. The ferrite limiter works on the principle of passive absorption. The ferrite material can withstand high power and has a moderate insertion loss. CN119171031A proposed a new ferrite limiter technology, but the limiter isolation in this scheme still needs to be further improved to meet the application scenarios of higher-intensity electromagnetic pulse protection technologies at the front end of the receiver. The inventor's research found that: if only the ferrite limiter protects the sensitive devices at the back end at the front end of the receiver system, when the input power of the receiving system is too high, the remaining microwave pulse energy after the flat top leakage is still relatively high, which may cause degradation or damage to the sensitive devices at the front end. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a ferrite and solid-state combined limiter circuit to solve the above problems.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A ferrite and solid-state combined limiting circuit, the combined limiting circuit comprising a ferrite substrate, on the front of which are arranged a ferrite limiting circuit and a solid-state limiting circuit connected to each other, wherein the solid-state limiting circuit comprises two limiting diodes, two sections of transmission lines are arranged between the two limiting diodes, an inductor is arranged between the two sections of transmission lines, one limiting diode is connected to the output transmission line, and the other limiting diode is connected to the output of the microstrip limiting circuit through the transmission line.

[0008] The solid-state limiter has a lower turn-on threshold than the ferrite limiter and is highly integrated. It is organically combined with the ferrite limiter. The front-stage ferrite limiter bears most of the power protection pressure, and the rear-stage solid-state limiter can well make up for the insufficient isolation of the single-stage ferrite limiter. At the same time, the fast response characteristics of the solid limiter can also achieve the advantage of a lower combined limiting threshold. The ferrite and solid-state combined limiting circuit can perfectly solve the high-power microwave protection power capacity while achieving high isolation and low turn-on threshold.

[0009] Wherein, the ferrite limiting circuit is selected from one of a standing wave circuit and a traveling wave circuit limiting circuit.

[0010] As one of the preferred technical solutions, the standing wave circuit is a parallel coupled limiting circuit structure, which includes n transmission lines and an input microstrip line, 2≤n≤15, and the front and rear sections of each transmission line are separated and parallel but not connected, and the input microstrip line is connected to a connector or a bonding wire.

[0011] The ferrite limiting circuit generally selects a parallel coupled microstrip structure. The spacing and length of two adjacent long microstrip lines are selected according to the resonant frequency. The higher the frequency, the shorter the length of the microstrip line. The larger the dielectric constant of the ferrite material, the shorter the length of the microstrip line. The spacing of the ferrite microstrip lines is strongly related to the working bandwidth of the ferrite limiting circuit. The wider the working bandwidth of the limiting circuit, the closer the distance between the limiting circuits.

[0012] The parallel microstrip coupled lines are standing wave structures. There is an electromagnetic field concentration at the antinode of the wave. The RF magnetic field intensity excited under high power state is 2-15 times higher than the RF magnetic field excited by the uniform transmission line structure. The excitation RF magnetic field multiple is related to the thickness of the ferrite material, the length of the short transmission line, and the working bandwidth. The thinner the ferrite material thickness, the greater the excitation RF magnetic field intensity multiple, the wider the working bandwidth, the stronger the magnetic coupling between the transmission lines, and the nonlinear effect threshold in the HPM electromagnetic environment can also be reduced, further improving the limiting isolation.

[0013] As another preferred technical solution, the traveling wave circuit is a straight transmission line with a length of 20 to 50 mm; or a folded microstrip circuit structure consisting of 2 to 15 segments. The number of segments is strongly related to the limiting isolation index. The more segments there are, the stronger the limiting isolation, and an input microstrip line.

[0014] As a preferred technical solution, the solid-state limiting circuit is arranged as follows: drill holes with a diameter of 0.5 mm to 1.5 mm on the ferrite substrate, then install the bare chip diode in the holes and interconnect it with the ferrite substrate through a micro-assembly process;

[0015] As a preferred technical solution, the solid-state limiting circuit is arranged by soldering a surface-mounted packaged diode on the ferrite substrate.

[0016] That is, the output of the microstrip limiting circuit is connected to the solid-state limiting circuit. The solid-state limiting circuit and the microstrip limiting circuit are arranged on the same ferrite substrate. If a packaged limiting diode is used, a limiting diode pad is designed on the substrate, and then the limiting diode is soldered on the ferrite substrate; if it is a bare chip limiting diode, drill holes in the ferrite, then bury the bare chip diode in the holes, and then connect the input and output of the diode to the ferrite transmission line through bonding wires. The inductor on the solid-state limiting circuit is realized by designing microstrip wires on the ferrite. The microstrip wires can be straight lines, folded lines, spiral lines, or lumped parameter inductors, and can be selected and designed according to actual space requirements.

[0017] The index allocation between ferrite limiting and solid-state limiting follows that the maximum output energy of ferrite limiting is less than the upper limit of the power capacity that the solid-state limiting can withstand by more than 3 dB, preventing the output power of the ferrite limiter from burning out the limiting diode.

[0018] As a preferred technical solution, the ferrite substrate is made of YIG ferrite material, with a ground layer on the back and a circuit pattern layer on the front of the ferrite substrate. The YIG ferrite material can be a pure YIG material or a YIG material doped with rare earth elements. Preferably, it is a microwave ferrite material with a large saturation magnetization intensity, a low resonance line width, and a low spin wave damping. Further preferably, the saturation magnetization intensity of this material is 4πMs = 1800 Gauss, the resonance line width ΔH ≤ 23 Oe, the spin wave line width ΔHk ≤ 2 Oe, the relative dielectric constant εr = 14.5, and the loss tangent tanδ ≤ 0.0002.

[0019] This is a typical ferrite material applied in the present invention, which can be understood by those of ordinary skill in the art. Other ferrite materials are also feasible.

[0020] The number of transmission line segments of the ferrite limiter circuit is strongly related to the limiter turn-on threshold, limiter isolation, and solid-state limiter isolation. The ferrite limiter isolation is obtained by simulation calculation based on the spin-wave linewidth, dielectric constant, saturation magnetization, and the shape of the ferrite material.

[0021] The limiter diode of the present invention is a PIN limiter diode well-known in the art, and its structure is composed of a P-type semiconductor, an intrinsic semiconductor (I layer), and an N-type semiconductor. The limiter isolation of the solid-state limiter is strongly related to the I layer of the limiter diode. The thicker the I layer, the stronger the power-bearing capacity of the diode, but the insertion loss will increase. The thickness of the I layer of the limiter diode needs to be comprehensively selected according to the requirements of the insertion loss. Using typical materials (4πMs = 1800 Gauss, resonance linewidth ΔH ≤ 23 Oe, spin-wave linewidth ΔHk ≤ 2 Oe, relative dielectric constant εr = 14.5, loss tangent tanδ ≤ 0.0002), X-band signal with a pulse width of 35 ns, power-bearing capacity of 10 kW, limiter isolation of 25 dB, ferrite substrate size of 6 mm * 18 mm * 0.3 mm, and the number of parallel-coupled line segments is 4. The materials used in the following embodiments are typical materials, and other types of ferrite materials can also be used.

[0022] As a preferred technical solution, the thickness of the ferrite substrate is 0.1 - 1 mm.

[0023] The second object of the present invention is to provide a high-power microwave front-door protection device composed of the above-mentioned ferrite and solid-state combined limiter circuit. The technical solution adopted is that it includes the above-mentioned ferrite and solid-state combined limiter circuit, and also includes a cavity and a permanent magnet. Among them, the ferrite and solid-state combined limiter circuit is assembled at the bottom of the cavity, the permanent magnet is two pieces, which are respectively arranged on opposite sides of the cavity, and it also includes input and output connectors. One end of the input and output connectors is connected to the input and output microstrip lines of the ferrite and solid-state combined limiter circuit

[0024] The combined protection technology of ferrite pre-stage limiting and solid-state reflective post-stage limiting of the present invention combines the advantages of ferrite limiting and solid-state limiting. It should be emphasized that the present invention is not just a simple combination of the two technologies, but at least the following difficulties need to be overcome: accurate calculation of the limiting thresholds of the ferrite limiting circuit and the diode limiting circuit, and precise allocation of the limiting thresholds of the solid-state limiting and ferrite limiting, as well as the limiting isolation and insertion loss indicators in the combined protection to achieve effective protection; if the allocation of the two technical indicators is unreasonable, the combined protection technology will fail to provide protection, resulting in a serious accident of burning out the receiving system. For example, when the output of the ferrite limiting is higher than the rated power of the solid-state limiting, the diode circuit will be burned out, causing the entire receiving system to be interrupted. This application requires integrating the ferrite limiting circuit and the solid-state limiting circuit on the same substrate, and in the microwave circuit manufacturing process, it is necessary to overcome the mechanical processing vulnerability of the thin ferrite substrate and the reliable interconnection bonding technology.

[0025] On the premise of reasonable allocation of the indicators of the two technologies, the two circuits sharing the ferrite substrate in the limiting device can achieve fast high-power microwave protection, maximize the limiting isolation within the power capacity and controllable insertion loss range, and at the same time have a relatively small volume, greatly improving the matching with the subsequent microwave circuit, and having great practical value in the field of high-power microwave front-door protection.

[0026] The working principle of the high-power microwave front-door limiting protection device of the present invention is as follows:

[0027] When a high-power microwave signal enters the device, under the action of the bias magnetic field and the high-power microwave, according to the non-linear effect mechanism of high-power loss of ferrite, the energy higher than the ferrite limiting threshold power will be absorbed, and the remaining absorbed energy is still higher than the threshold of the solid-state limiting circuit, and the remaining energy will be completely reflected back by the solid-state limiting circuit (such as Figure 6 f1 in the figure), thus achieving overall limiting of the high-power microwave. When the high-power signal is lower than the ferrite limiting threshold and higher than the solid-state limiting threshold, the high-power absorption effect of the ferrite limiting is very weak, mainly showing the characteristic of small loss, and the solid-state limiting will reflect all the remaining energy back (such as Figure 6 f2 in the figure); when the input power is lower than the solid-state limiting threshold, the energy loss of the microwave signal only shows the characteristic of small loss and has no limiting characteristic, and most of the signals are transmitted to the subsequent receiver circuit (such as Figure 6 f3 in the figure).

[0028] The mechanism of the energy loss of the ferrite circuit absorption limiter is the nonlinear loss effect brought about by the spin wave instability of the ferrite at high power. When high-power microwaves first enter the ferrite, the ferrite is in a thermal equilibrium state. After the relaxation time, the amplitude of the spin wave increases sharply. The half-frequency spin wave couples with the ferrite lattice, causing the ferrite lattice to vibrate and dissipating the energy in the form of heat. Solid-state reflection limiter is when the power exceeds the limiter threshold, the limiter diode conducts, resulting in circuit mismatch and causing the high-power signal to be reflected back.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] In the working frequency band of the present invention, the nonlinear loss effect of the ferrite is utilized to absorb and limit high-power microwaves. The unabsorbed high-power microwaves will be reflected back by the solid-state limiter circuit. The combined protection technology of ferrite and solid-state limiter has both the ability of the ferrite to withstand high power and the high sensitivity of the solid-state limiter, with a short limiter response time, and the size of the device is small. It can open the front-door protection in the HPM electromagnetic environment and has a good limiter effect, which is conducive to integration and application in microwave receivers.

[0031] The present invention has a high power capacity (in the order of hundreds of kW), fast response and fast recovery time (several ns), and high limiter isolation (better than 32 dB) in the HPM electromagnetic environment, achieving an ideal comprehensive front-door protection effect for high-power microwaves. Moreover, the size of the device is small, which is beneficial for the engineering protection application of microwave receivers against strong electromagnetic pulses. Brief Description of the Drawings

[0033] Figure 1 is the circuit schematic diagram of the high-power microwave front-door protection device of the present invention;

[0034] Figure 2 is the exploded view of the high-power microwave front-door protection device of Embodiment 1 of the present invention;

[0035] Figure 3 is Figure 2 the assembly and sectional view of;

[0036] Figure 4 is the combined circuit diagram of parallel-coupled ferrite limiter and solid-state limiter of Embodiment 1 of the present invention;

[0037] Figure 5 Schematic diagram of the limiter protection effect of the combined protection technology;

[0038] Figure 6 The simulation results of the insertion loss and return loss of Embodiment 1 of the present invention under small signals;

[0039] Figure 7Simulation results of the 30ns HPM limiting isolation degree of the protection device with pulse width combination at 9.5GHz frequency in Embodiment 1 of the present invention.

[0040] Figure 8 It is the circuit diagram of the combined ferrite limiting and solid-state limiting with a folding structure in Embodiment 2 of the present invention;

[0041] Figure 9 Simulation results of the insertion loss and return loss under small signals in Embodiment 2 of the present invention;

[0042] Figure 10 Simulation results of the 30ns pulse width HPM limiting isolation degree of the combined protection device at 9.5GHz frequency in Embodiment 2 of the present invention.

[0043] In the figure: 1. Combined ferrite and solid-state limiting circuit; 1-1. Ferrite substrate; 1-2. Ferrite limiting circuit; 1-3. Limiting diode a; 1-4. Limiting diode b; 1-5. Distributed parameter inductor; 1-6. Transmission line a; 1-7. Transmission line b; 1-8. Bonding wire; 1-9. Input microstrip line; 1-10. Output microstrip line; 2. Cavity; 3. Permanent magnet; 4. Cover plate; 5. Connector. Detailed implementation manners

[0045] The present invention will be further described below in conjunction with the accompanying drawings.

[0046] Embodiment 1:

[0047] A high-power microwave front door protection device, the circuit principle of which can be referred to Figure 1 and the overall structure can be referred to Figure 2 and Figure 3 From Figure 2 and Figure 3 it can be seen that it includes a combined ferrite and solid-state limiting circuit 1, a cavity 2, a permanent magnet 3, a cover plate 4 and a connector 5.

[0048] Among them, the combined ferrite and solid-state limiting circuit is arranged on the ferrite substrate 1-1, the combined ferrite and solid-state limiting circuit 1 is assembled at the bottom of the cavity 2, there are two permanent magnets 3, which are bonded or welded to both sides of the cavity 2, and a connector 5 is also included. The connector 5 is connected to the input and output microstrip lines of the combined ferrite and solid-state limiting circuit 1;

[0049] Among them, the combined ferrite and solid-state limiting circuit 1 is the core unit of the limiting protection device;

[0050] The cavity 2 is used for the installation of the ferrite and solid-state combined limiter circuit 1 and the fixation of the input and output connectors. The shape of the cavity 2 is designed according to the size and actual required shape of the ferrite and solid-state combined limiter circuit 1. The cover plate 4 is used for the sealing of the whole circuit and is generally fixed to the cavity by welding or screws;

[0051] The permanent magnets 3 are arranged on both sides of the cavity 2. The magnetic field of the permanent magnets 3 is parallel to the microwave magnetic field and is used to magnetize the ferrite substrate, which is a key component of the limiter protection device;

[0052] The connector 5 in this embodiment is a glass insulator, and its function is to provide connections for the input and output of the signals of the ferrite and solid-state combined limiter circuit 1. In the case where no connector is required, bonding and other methods can be used to provide the input and output connections of the microwave signals;

[0053] In this embodiment, the ferrite limiter circuit in the ferrite and solid-state combined limiter circuit 1 is a parallel-coupled circuit, as Figure 4 shown, including a ferrite substrate 1-1. Starting from the input microstrip line 1-9 on the ferrite substrate 1-1, there are four sections of parallel-coupled line ferrite limiter circuits 1-2. This part (the four sections of parallel-coupled line ferrite limiter circuits 1-2) is the ferrite limiter part. The output of the ferrite limiter circuit is connected to the solid-state limiter circuit. The limiter diode a 1-3 and the limiter diode b 1-4 are installed in the holes drilled in the ferrite substrate 1-1. The diameter of the holes is just larger than that of the limiter diodes. The limiter diode b 1-4 is connected to the output of the ferrite limiter circuit through a bonding wire 1-8. The output of the limiter diode and the transmission line a 1-6 are connected through a bonding wire 1-8. The output end of the transmission line a 1-6 is directly connected to the transmission line b 1-7. There is a distributed parameter inductor 1-5 between the transmission line a 1-6 and the transmission line b 1-7. The distributed parameter inductor 1-5 is connected to the back ground plane through a ferrite metallized via. Usually, there is a pad for the metallized via, and the pad is 0.05 mm larger than the metallized hole. The transmission line b 1-7 is connected to the limiter diode a 1-3 through a bonding wire 1-8. The limiter diode a 1-3 is installed in the hole drilled in the ferrite substrate 1-1. The output of the limiter diode a 1-3 is connected to the output microstrip line 1-10 of the limiter through a bonding wire 1-8;

[0054] The ferrite substrate 1-1 of this embodiment uses polycrystalline ferrite material, gadolinium yttrium garnet (YGdIG). The product used in this embodiment is a commercially available product from Southwest Applied Magnetics Research Institute, with the model number 18F6. Its saturation magnetization intensity 4πMs = 1800 Gauss ± 5%, resonance linewidth ΔH = 23 Oe ± 5%, spin wave linewidth ΔHk = 2 Oe ± 5%, relative dielectric constant εr = 14.5 ± 5%, loss tangent angle tanδ = 0.0002 ± 5%; the thickness t of the ferrite substrate is 0.3 mm, the length is 18 mm, the width w is 6 mm, and the order of the parallel coupled line is fourth order, as Figure 4 shown;

[0055] Two holes with a diameter of 0.6 mm are drilled on the ferrite substrate for installing the limiter diode chip, and a hole with a diameter of 0.4 mm is used for metallization grounding. A layer of copper is sputtered on the front and back, and the front circuit pattern is processed through photolithography and etching processes. Then, about 1.5 μm of copper is electroplated on the front and back to thicken the copper layer thickness, and then about 2.5 μm of gold is plated;

[0056] The ferrite and solid-state combined limiter circuit 1 of this embodiment is installed at the bottom of the cavity 2, and permanent magnets 3 are placed on both sides of the cavity 2 to provide a DC bias magnetic field. The permanent magnets 3 are installed on the cavity 2 by bonding; the connector 5 (glass insulator) is connected to the input microstrip line 1-9 and the output microstrip line 1-10 of the ferrite limiter circuit, and the connector 5 is fixed by welding on the cavity 2. The connection process is shown in Figure 3 ;

[0057] In this embodiment, the input microstrip line 1-9 and the input microstrip line 1-10 are jointly designed for 50Ω matching with the connector 5 (glass insulator). The widths of the input microstrip line and the output microstrip line are 0.19 mm. The lengths of the middle two parallel coupled lines are 5.26 mm respectively, and the lengths of the two parallel coupled lines at both ends are 4.66 mm respectively. The minimum distance between the parallel coupled lines is obtained through S-parameter simulation design.

[0058] The center frequency of the passband of this embodiment is 9.5 GHz, and the bandwidth is 1.2 GHz. Figure 6 shows the calculation results of the frequency-domain S-parameters of this embodiment. The return loss in the passband (8.9 GHz - 10.1 GHz) is greater than 17 dB, and the insertion loss is less than 1.1 dB.

[0059] In this invention, through the non-linear loss effect of ferrite in the band, absorption limiting of high-power microwaves and reflection limiting by turning off the limiter diode are carried out. To illustrate the limiting characteristics of this embodiment, Figure 7 gives the variation trend of the limiting isolation degree of the limiting combination device with the input power when the input is a 30 ns pulse-width HPM with a bias magnetic field of 1000 Gauss. As Figure 7As shown, the limiting isolation within an input HPM power of 13 dBm reflects the loss characteristics. When the input HPM power exceeds 20 dBm, the limiting isolation increases sharply. The limiting isolation is 11.4 dB at an input HPM power of 30 dBm, 19 dB at an input HPM power of 37 dBm, and 34 dB at an input HPM power of 53.5 dBm. This shows that the present invention can activate the front-door protection at a very low power in the HPM electromagnetic environment, has a good high-power limiting effect, and also has a high power tolerance.

[0060] Example 2

[0061] Compared with Example 1, in this embodiment, the ferrite limiting circuit in the ferrite and solid-state combined limiting circuit 1 is a folded circuit structure, as Figure 8 shown. The rest is the same as in Example 1. The folded limiting circuit includes a ferrite substrate 1-1. Starting from the input microstrip line 1-9 on the ferrite substrate 1-1, there is a folded ferrite limiting circuit 1-2. This part (the four long transmission lines and the four short transmission lines are connected end to end) is the ferrite limiting part. The lengths of the short transmission lines and the long transmission lines need to be determined according to the S-parameter simulation results. The greater the return loss in the S-parameters, the better. On the premise of ensuring the return loss, the length of the short transmission lines should be shortened as much as possible. This is beneficial to the concentration of the energy of the microwave field and is more conducive to improving the limiting isolation.

[0062] The center frequency of the passband in this embodiment is 9.5 GHz, and the bandwidth is 4 GHz. Figure 9 Shows the calculated results of the frequency-domain S-parameters of this embodiment. The return loss within the passband (8 GHz - 12 GHz) is greater than 20 dB, and the insertion loss is less than 1 dB.

[0063] In the present invention, through the non-linear loss effect of the ferrite in the band, absorptive limiting of high-power microwaves and limiting by the turn-off reflection of the limiting diode are carried out. To illustrate the limiting characteristics of this embodiment, Figure 10 the variation trend of the limiting level with the input power when a 30-ns pulse-width HPM is incident on the limiting device at a bias magnetic field of 900 Gauss in this embodiment is given. As Figure 10 shown, within an input power of 13 dBm, the limiting characteristics mainly reflect the loss characteristics. When the input power is greater than 20 dBm, the limiting isolation increases sharply. The limiting isolation is 23.8 dB at an input power of 40 dBm and 33.5 dB at an input power of 50 dBm.

[0064] The above embodiments are only for illustrating the technical concept and features of the present invention, and are only used for a specific description of the present invention, so that those skilled in the art can understand the content of the present invention and implement it accordingly. It is not intended to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the content of the present invention should be covered within the protection scope of the present invention.

Claims

1. A ferrite and solid-state combined limiter circuit, characterized in that, The combined limiting circuit includes a ferrite substrate, on the front of which a ferrite limiting circuit and a solid-state limiting circuit are interconnected. Among them, the solid-state limiting circuit includes two limiting diodes, between which there are two transmission lines, and an inductor is arranged between the two transmission lines. One of the limiting diodes is connected to the output transmission line, and the other limiting diode is connected to the output of the microstrip limiting circuit through a transmission line.

2. The ferrite and solid-state combined limiter circuit according to claim 1, characterized in that The ferrite limiting circuit is a parallel-coupled limiting circuit structure, which includes n transmission lines and an input microstrip line, where 2 ≤ n ≤ 15. Each previous transmission line is separated from and parallel to the subsequent one but not connected, and the input microstrip line is connected to a connector or a bonding wire.

3. The ferrite and solid state combined limiter circuit according to claim 1, wherein The ferrite limiting circuit is a straight transmission line with a length of 20 - 50 mm, or a folded microstrip circuit structure, which includes n transmission lines and an input microstrip line, where 2 ≤ n ≤ 15.

4. The ferrite and solid-state combined limiter circuit according to claim 1, characterized in that, The setting method of the solid-state limiting circuit is: drill holes with a diameter of 0.5 mm - 1.5 mm on the ferrite substrate, then install the bare chip diode in the holes and interconnect it with the ferrite substrate through a micro-assembly process.

5. The ferrite and solid-state combined limiter circuit according to claim 1, wherein The setting method of the solid-state limiting circuit is: weld the surface-mounted packaged diode on the ferrite substrate.

6. The ferrite and solid-state combined limiter circuit according to claim 1, characterized in that, The ferrite material used for the ferrite substrate has a saturation magnetization intensity of 4πMs = 1800 Gauss, a resonance line width of ΔH ≤ 23 Oe, a spin-wave line width of ΔHk ≤ 2 Oe, a relative dielectric constant of εr = 14.5, and a loss tangent of tanδ ≤ 0.0002.

7. The ferrite and solid state combined limiter circuit according to claim 1, wherein The thickness of the ferrite substrate is 0.1 - 1 mm.

8. A high-power microwave front door protection device composed of the ferrite according to any one of claims 1 to 7 and a solid-state combined limiter circuit, characterized in that, It includes the ferrite and solid-state combined limiting circuit as described above, and also includes a cavity and a permanent magnet. Among them, the ferrite and solid-state combined limiting circuit is assembled at the bottom of the cavity, there are two permanent magnets respectively arranged on opposite sides of the cavity, and it also includes an input-output connector, one end of which is connected to the input-output microstrip line of the ferrite and solid-state combined limiting circuit.

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