Ferrite amplitude limiting circuit and high-power microwave front door amplitude limiting protection device composed of ferrite amplitude limiting circuit

Abstract

The invention discloses a ferrite amplitude limiting circuit and a high-power microwave front door amplitude limiting protection device composed of the ferrite amplitude limiting circuit, and belongs to the technical field of microwaves. The ferrite amplitude limiting circuit comprises a ferrite substrate, and a centrosymmetric microstrip circuit structure is arranged on the front face of the ferrite substrate; the micro-strip circuit structure comprises long transmission lines, short transmission lines and input and output micro-strip lines, and all the long transmission lines and the short transmission lines are of a periodic folding structure or a quasi-periodic folding structure as a whole; absorption type amplitude limiting is carried out on high-power microwaves in the band through the nonlinear loss effect of the ferrite, front door protection can be started in the HPM electromagnetic environment, the good amplitude limiting effect is achieved, the size of the device is small, and application in a microwave receiver is facilitated.

Description

Technical Field

[0001] The invention relates to the field of microwave technology, in particular to a ferrite limiting circuit and a high-power microwave front door limiting protection device composed of the ferrite limiting circuit. Background Art

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

[0003] A microwave receiver is a device for receiving communication signals, and is mainly composed of an antenna, a filter, a low-noise amplifier, a mixer, an analog-to-digital converter, a digital processing unit, etc. Among them, semiconductor devices such as low-noise amplifiers and mixers can withstand low power and are easily burned by the HPM received by the "front door" antenna. In order to protect devices such as low-noise amplifiers and mixers that have poor power tolerance, the receiver needs to be protected from HPM.

[0004] HPM front door protection technology mainly includes energy selective surface technology, plasma limiting technology, solid-state limiting technology, and ferrite limiting technology. Energy selective surface is an antenna limiting technology. This technology has large insertion loss and affects both the receiver and the transmitter. Plasma limiters and solid-state limiters have limited power tolerance. Ferrite limiters are absorption limiters and passive devices. Ferrite materials can withstand high power, so ferrite limiters can withstand high power. At the same time, ferrite limiters can also have low limiting thresholds.

[0005] There are two types of ferrite limiters: waveguide loading and planar loading. Among the planar loading limiters, the planar ferrite limiter based on the resonant structure has the filtering characteristics of the filter and also has limiting performance. However, the Q value of a single resonant unit of the resonant structure is low and the loss will be relatively large; the more resonant units there are, the greater the loss will be. At the same time, the overall area of ​​the device is large, which is not conducive to application in microwave receivers. Summary of the invention

[0006] One of the purposes of the present invention is to provide a ferrite limiter circuit to solve the above-mentioned problem.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a ferrite limiting circuit, the ferrite limiting circuit includes a ferrite substrate, and a centrally symmetrical microstrip circuit structure is arranged on the front side of the ferrite substrate, the microstrip circuit structure includes n long transmission lines, n or n+1 or n-1 short transmission lines, and input and output microstrip lines, 3≤n≤18, wherein the input and output microstrip lines are arranged at both ends of the microstrip circuit structure, the long transmission line and the short transmission line are arranged in the middle of the microstrip circuit structure, each section of the long transmission line is cross-arranged with each section of the short transmission line and connected end to end, two adjacent sections of the long transmission line are arranged in parallel, and two adjacent sections of the short transmission line are arranged in parallel, and all the long transmission lines and the short transmission lines are generally in a periodic folding structure or a quasi-periodic folding structure.

[0008] As a preferred technical solution, the ferrite material used in the ferrite substrate has a saturation magnetization of 4πMs=1800Gauss, a resonance line width ΔH≤23Oe, a spin wave line width ΔHk≤2Oe, a relative dielectric constant εr=14.5, and a loss tangent angle tanδ≤0.0002. This is a typical ferrite material used in the present invention, and of course, other ferrite materials are also feasible.

[0009] As a further preferred technical solution, the thickness of the ferrite substrate is 0.1-0.7 mm.

[0010] As a further preferred technical solution, when the thickness of the ferrite substrate is ≤0.35mm, the total length of the long transmission line and the short transmission line is 6-30mm; when the thickness of the ferrite substrate is >0.35mm and ≤1mm, the total length of the long transmission line and the short transmission line is 10-45mm.

[0011] The number of transmission line segments is strongly correlated with the threshold of the limit isolation, and the total length of the transmission line is strongly correlated with the limit isolation. Under the premise of a given limit isolation, the thinner the ferrite material thickness, the smaller the total length of the long transmission line and the short transmission line required; the more folds, the smaller the total length of the transmission line. The limiting isolation is calculated based on the spin wave line width, dielectric constant, saturation magnetization, and ferrite material shape simulation of the ferrite material, using typical materials (4πMs=1800Gauss, resonance line width ΔH≤23 Oe, spin wave line width ΔHk≤2Oe, relative dielectric constant εr=14.5, loss tangent tanδ≤0.0002), X-band 10kW power, signal 120ns pulse width, 10dB limiting isolation, ferrite substrate size 4mm*6mm*0.2mm, total transmission line length (the sum of all long transmission lines and short transmission lines) is about 2cm, then the folded long transmission line is 15 sections and the short transmission line is 14 sections. The material used in the following embodiment is a typical material, and other types of ferrite materials can also be implemented.

[0012] The ferrite limiting circuit of the present invention comprises a ferrite substrate made of microwave YIG ferrite material, a back grounding layer and a front circuit pattern layer of the ferrite substrate, wherein the YIG ferrite material can be a pure YIG material or a YIG material doped with rare earth elements, and preferably a microwave ferrite material with low resonance line width, low spin wave damping and low dielectric loss.

[0013] As a preferred technical solution, the periodic folding structure is as follows: the distances between two adjacent long transmission lines are equal, and the widths of two adjacent short transmission lines are equal.

[0014] As a further preferred technical solution, the distance between two adjacent long transmission lines is 0.152 mm, and the width of two adjacent short transmission lines is 0.111 mm.

[0015] As a preferred technical solution, the quasi-periodic folding structure is: the distances between at least two adjacent long transmission lines are not equal.

[0016] The RF magnetic field excited by the periodic folded structure transmission line is more than 2-8 times the RF magnetic field excited by the uniform transmission line structure. The multiple of the excited RF magnetic field is related to the thickness of the ferrite material and the length of the short transmission line. The thinner the ferrite material, the greater the multiple of the excited RF magnetic field, and the shorter the short transmission line, the greater the multiple of the excited RF magnetic field. On the other hand, the periodic or quasi-periodic folded line structure is N times longer than the equivalent microwave transmission path length of the uniform structure transmission line, where N is the number of folds, which greatly increases the utilization rate of the ferrite substrate material and can also reduce the threshold of nonlinear effects in the HPM electromagnetic environment, further improving the limiting isolation.

[0017] The second object of the present invention is to provide a high-power microwave front door limiting protection device composed of the above-mentioned ferrite limiting circuit, and the technical scheme adopted is, including the ferrite limiting circuit, and also including a cavity and a permanent magnet, wherein the ferrite limiting circuit is arranged on a ferrite substrate, and the ferrite limiting circuit is assembled at the bottom of the cavity, and the permanent magnet is divided into two pieces, which are respectively arranged on opposite sides of the cavity, and a magnetic circuit plate for clamping the permanent magnet and the cavity is also provided, and also includes a glass insulator and a connector, one end of the glass insulator is connected to the input and output microstrip lines of the ferrite limiting circuit, and the other end is connected to the connector.

[0018] The working principle of the high-power microwave front door limiting protection device of the present invention is as follows: When a high-power microwave signal enters the device, under the action of the bias magnetic field and high-power microwave, according to the nonlinear effect mechanism of high power loss of ferrite, the frequency energy corresponding to the power higher than the limiting threshold will be absorbed (such as Figure 5f3, f4), the signal energy after the absorbed energy is lower than the limiting threshold, and the energy signal below the limiting threshold can pass (such as Figure 5 f3, f4), while the frequency components below the threshold power (such as Figure 5 f1 and f2 in the band will not be attenuated, thus achieving high-power microwave limiting. The specific energy loss mechanism is the nonlinear loss effect caused by the spin wave instability under high power of ferrite. When high-power microwaves enter the ferrite, the ferrite is in thermal equilibrium. The high-power microwaves with a spin wave amplitude within the passband will excite the half-frequency spin wave on the ferrite substrate (the spin wave frequency is half of the incident microwave frequency). After the relaxation time, the spin wave amplitude increases sharply, and the half-frequency spin wave couples with the ferrite lattice, causing the ferrite lattice to vibrate and dissipate energy in the form of heat.

[0019] Compared with the prior art, the advantages of the present invention are: the present invention realizes absorption limiting of high-power microwaves through the nonlinear loss effect of ferrite within the band, the front door protection can be opened in the HPM electromagnetic environment, and it has a good limiting effect, and the size of the device is small, which is conducive to application in microwave receivers. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the basic structure of the ferrite limiting protection device according to an embodiment of the present invention; Figure 2 for Figure 1 Assembly drawing of Figure 3 It is a schematic diagram of the characteristics of the front circuit of the folded structure ferrite limiter according to an embodiment of the present invention; Figure 4 It is a schematic diagram of the circuit characteristics of the side and back sides of the folded structure ferrite limiter according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the limiting principle of the ferrite limiting protection device; Figure 6 Static small signal simulation results of folded structure limiter; Figure 7 The simulation results of the isolation of different pulse widths at different input powers at 10 GHz frequency in the implementation example of the present invention.

[0021] In the figure: 1. Ferrite limiting circuit; 11. Long transmission line; 12. Short transmission line; 13. Input and output microstrip lines; 21. Upper cavity; 22. Cover plate; 3. Permanent magnet; 4. Magnetic circuit board; 5. Connector; 6. Screw; 7. Glass insulator. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings.

[0023] Example:

[0024] A high-power microwave front door limiting protection device, the structure of which is shown in Figure 1 and Figure 2 , including a ferrite limiting circuit 1, a cavity 2 and a permanent magnet 3, wherein the ferrite limiting circuit is arranged on a ferrite substrate, the ferrite limiting circuit 1 is assembled at the bottom of the cavity, the permanent magnet 3 is two pieces, respectively arranged on opposite sides of the cavity, and a magnetic circuit plate 4 is provided for clamping the permanent magnet 3 and the cavity through screws 6, and also includes a glass insulator 7 and a connector 5, one end of the glass insulator 7 is connected to the input and output microstrip line 13 of the ferrite limiting circuit 1, and the other end is connected to the connector 7, Among them, the ferrite limiting circuit 1 is the core unit of the limiting protection device; The cavity is composed of an upper cavity 21 and a cover plate 22, and is used for installing the ferrite limiter circuit 1, the input and output connectors 5, and the glass insulator 7. The shape of the cavity is designed according to the size of the ferrite limiter circuit 1 and the actual required shape; The permanent magnets 3 are placed on both sides of the cavity. The magnetic field of the permanent magnets 3 is parallel to the microwave magnetic field and is used to magnetize the ferrite substrate. It is a key component of the limiting protection device. The magnetic circuit plate 4 is used for magnetic conduction, so that the magnetic field of the permanent magnet 3 is focused on both sides of the cavity; The connector 5 of this embodiment is an SMA connector, and the glass insulator 7 is used to provide a connection for the input and output of the ferrite limiter circuit 1 signal. In scenarios where a connector is not required, a method such as gold wire bonding can be used to provide a microwave signal input and output connection; In this embodiment, the ferrite limiting circuit 1 includes a ferrite substrate, and a centrally symmetrical microstrip circuit structure is arranged on the front of the ferrite substrate. The microstrip circuit structure of this embodiment includes fifteen long transmission lines 11, fourteen short transmission lines 12 and input and output microstrip lines 13, and its structure is as follows: Figure 3 and Figure 4 As shown, the input and output microstrip lines 13 are arranged at both ends of the microstrip circuit structure, the fifteen long transmission lines 11 and the fourteen short transmission lines 12 are arranged in the middle of the microstrip circuit structure, each long transmission line is arranged crosswise with each short transmission line and connected end to end, two adjacent long transmission lines 11 are arranged in parallel, and two adjacent short transmission lines 12 are also arranged in parallel, and all the long transmission lines 11 and the short transmission lines 12 are in a periodic folding structure or a quasi-periodic folding structure as a whole; The front microstrip circuit is composed of periodic or quasi-periodic folded transmission lines. The long transmission lines are parallel to each other. The length of each long transmission line is l. Assume that the vertical distance between the first long transmission line 11 and the second long transmission line 11 is s1, the vertical distance between the second long transmission line 11 and the third long transmission line 11 is s2, and so on. The vertical distance between the fourteenth long transmission line 11 and the fifteenth long transmission line is s14. Assume that the adjacent The widths of the two short transmission lines 12 are w1 and w2 respectively. When s1=s2=s3=s4=s5=s6=s7=s8=s9=s10=s11=s12=s13=s14, and w1=w2, it is a periodic structure. When two or more of s1, s2, s3, s4, s5, s6, s7, s8, s9, s10, s11, s12, s13, and s14 are not equal, it is called a quasi-periodic structure. When the overall standing wave of the periodic structure is not good, the standing wave is generally less than -15dB. Adjusting the length of s1, s2, s3, s4, s5, s6, s7, s8, s9, s10, s11, s12, s13, and s14 can optimize the standing wave under small signals. Randomly select 1 to 3 sections to lengthen or shorten them. The length of the side becomes shorter according to the change of the standing wave. When the standing wave is better than -15dB, stop adjusting and change from a periodic structure to a quasi-periodic structure. Specifically, the thickness t of the ferrite substrate is generally between 0.1-1 mm, and the length and width a and b of the ferrite substrate can range from a few millimeters to a few centimeters; The ferrite substrate of this embodiment adopts polycrystalline ferrite material, gadolinium yttrium garnet (YGdIG), and this embodiment adopts the commercially available product of Southwest Institute of Applied Magnetism, brand 18F6, whose saturation magnetization intensity 4πMs=1800Gauss, resonance line width ΔH=23Oe±5%, spin wave line width ΔHk=2Oe±5%, relative dielectric constant εr=14.5±5%, loss tangent angle tanδ=0.0002±5%; the thickness t of the ferrite substrate is 0.2mm, the length b is 6mm, the width a is 4mm, and the total length of the transmission line (the sum of the lengths of all long transmission lines 11 and short transmission lines 12) is 2cm, as shown in FIG. Figure 4 As shown; A layer of copper is sputtered on the front and back of the ferrite substrate, and the front circuit pattern is processed through photolithography and etching processes, and then copper is electroplated on the front and back by about 1.5μm, the copper layer thickness is thickened, and then gold is plated by about 2.5μm; A centrosymmetrical microstrip circuit structure is arranged on the front of the ferrite substrate. The microstrip circuit structure of this embodiment includes fifteen long transmission lines 11, fourteen short transmission lines 12, input and output microstrip lines 13 and related reference grounds; a ferrite limiting circuit 1 is installed at the bottom of the cavity, permanent magnets 3 are placed on both sides of the cavity to provide a DC bias magnetic field, and an iron magnetic circuit plate 4 is used to clamp the permanent magnet 3 and the cavity together; a glass insulator 7 is connected to the input and output microstrip lines 13 of the ferrite limiting circuit, and the other side of the glass insulator 7 is connected to the SMA connector 5. The glass insulator 7 and the SMA connector 5 are both assembled and fixed on the cavity. The connection process is shown in FIG. Figure 2 Middle AA section view; In this embodiment, the input and output microstrip lines 13 (see Figure 3 The "wp" segment in the transmission line 12 is combined with a glass insulator to perform a 50Ω matching design. The width of the input and output microstrip line 13 is w, and the widths of the two adjacent short transmission lines 12 are w1 and w2, respectively. In this embodiment, w=w1=w2=0.111mm, s1=s2=s3=s4=s5=s6=s7=s8=s9=s10=s11=s12=s13=s14=0.152mm, l=1.74mm, wp=1.02mm, a=4mm, b=6mm, t=0.2mm; The passband center frequency of this embodiment is 10 GHz, and the bandwidth is 1 GHz. Figure 6 The frequency domain S parameter calculation results of this embodiment are shown. The return loss in the passband (9GHz-11GHz) is greater than 20dB and the insertion loss is less than 1dB.

[0025] The present invention realizes absorption-type limiting of high-power microwaves through the nonlinear loss effect of ferrite in the band. The nonlinear magnetic field threshold of ferrite is different under different bias magnetic fields and high-power microwave incident signals with different pulse widths, so the limiting power threshold is also different.

[0026] To illustrate the limiting characteristics of this embodiment, Figure 7 The variation trend of the limiting level with input power when HPM signals with different pulse widths are incident when the bias magnetic field is 800 Gauss is given. The wider the incident microwave pulse width, the greater the saturation limiting isolation. Figure 7 As shown, taking 90ns as an example, the limiting isolation of 10W input power is -1.3dB; the limiting isolation of 100W input power is -4.47dB; the limiting isolation of 1kW input power is -10.86dB; the limiting isolation of 200kW input power is -19.4dB; when the input power is greater than 50W and the pulse width is short (the pulse width is less than 240ns), the limiting isolation increases sharply with the increase of the pulse width. This shows that the present invention can open the front door protection in the HPM electromagnetic environment and has a good limiting effect.

[0027] 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 people familiar with the technology can understand the content of the present invention and implement it accordingly. They cannot be used to limit the protection scope of the present invention. All 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 limiting circuit, characterized in that: The ferrite limiting circuit includes a ferrite substrate, and a centrally symmetrical microstrip circuit structure is arranged on the front side of the ferrite substrate. The microstrip circuit structure includes n long transmission lines, n or n+1 or n-1 short transmission lines, and input and output microstrip lines, 3≤n≤18, wherein the input and output microstrip lines are arranged at both ends of the microstrip circuit structure, the long transmission line and the short transmission line are arranged in the middle of the microstrip circuit structure, each section of the long transmission line is arranged crosswise with each section of the short transmission line and connected end to end, two adjacent sections of the long transmission line are arranged in parallel, and two adjacent sections of the short transmission line are arranged in parallel, and all the long transmission lines and the short transmission lines are overall in a periodic folding structure or a quasi-periodic folding structure.

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

3. The ferrite limiting circuit according to claim 2, characterized in that: The thickness of the ferrite substrate is 0.1-1 mm.

4. The ferrite limiting circuit according to claim 3, characterized in that: When the thickness of the ferrite substrate is ≤0.35mm, the total length of the long transmission line and the short transmission line is 6-30mm; when the thickness of the ferrite substrate is >0.35mm and ≤0.7mm, the total length of the long transmission line and the short transmission line is 10-45mm.

5. The ferrite limiting circuit according to claim 1, characterized in that: The periodic folding structure is such that the distances between two adjacent long transmission lines are equal, and the widths of two adjacent short transmission lines are equal.

6. The ferrite limiter circuit according to claim 5, characterized in that: The distance between two adjacent long transmission lines is 0.152 mm, and the width of two adjacent short transmission lines is 0.111 mm.

7. The ferrite limiting circuit according to claim 1, characterized in that: The quasi-periodic folding structure is that the distances between at least two adjacent long transmission lines are not equal.

8. A high-power microwave front door limiting protection device composed of the ferrite limiting circuit according to any one of claims 1 to 7, characterized in that: It includes the ferrite limiting circuit, a cavity and a permanent magnet, wherein the ferrite limiting circuit is arranged on a ferrite substrate, the ferrite limiting circuit is assembled at the bottom of the cavity, the permanent magnet is in two pieces, and is respectively arranged on two opposite sides of the cavity, a magnetic circuit plate for clamping the permanent magnet and the cavity is also provided, and a glass insulator and a connector are also provided, one end of the glass insulator is connected to the input and output microstrip lines of the ferrite limiting circuit, and the other end is connected to the connector.

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