X-waveband radio frequency signal lightning protection device

Abstract

The invention provides an X-band radio frequency signal lightning protection device, and belongs to the technical field of lightning protection, the device comprises a microstrip line printed board and a lightning protection circuit welded on the microstrip line printed board, the lightning protection circuit comprises a 1 / 4 wavelength short-circuit line and an LTCC high-pass filter, the 1 / 4 wavelength short-circuit line and the LTCC high-pass filter are connected in series, and the LTCC high-pass filter is connected with the microstrip line printed board. And the 1 / 4 wavelength short-circuit line is grounded. The X-band radio frequency signal thunder and lightning protection device provided by the invention has the advantages that the number of components is small, miniaturization and light weight are realized, the circuit form is simple, and the portability is high; the protection device can meet the protection requirements of all thunder and lightning pulse grades 1-5, and the actually measured clamping voltages for the five-grade thunder and lightning pulse with the waveform of 5A reach + 3.9 V and-3.4 V.

Description

Technical Field

[0001] The present invention belongs to the technical field of lightning protection, and particularly relates to an X-band radio frequency signal lightning protection device. Background Art

[0002] Lightning is a common natural phenomenon and an important factor affecting the flight safety of aircraft. The destructive effects of lightning are divided into direct effects and indirect effects. The direct effect refers to the physical damage to the airframe structure caused by the high voltage and large current generated when lightning directly attaches to the aircraft surface. The indirect effect refers to the instantaneous surge voltage and current induced in the aircraft's internal electronic equipment by the lightning electromagnetic field flowing into the fuselage and the fuselage structure voltage during the lightning strike, resulting in equipment functional failures or permanent damage. Aircraft-mounted equipment is usually installed inside the aircraft, and its protection object is mainly the surge voltage and current generated by the indirect effect of lightning.

[0003] The main protection measures for the indirect effect of lightning are to set up protection circuits at the ports of the equipment to suppress the lightning surge voltage or discharge the surge current, and usually use protection devices such as gas discharge tubes, varistors, and transient suppression diodes. For the X-band radio frequency port of an airborne radar, due to the relatively large junction capacitance of varistors and transient suppression diodes, generally in the order of hundreds to thousands of nanofarads, they are not suitable for the lightning protection design of X-band radio frequency signals. Currently, there are two main radio frequency lightning protection methods. One is to use a gas discharge tube, whose inter-electrode capacitance is less than 5 pF, so the influence on radio frequency signals is relatively small. The disadvantage is that the response speed is slow, and its response time is generally in the microsecond level, making it difficult to meet the protection requirements for nanosecond-level lightning pulse waveforms. The other is to use a high-pass filter. The highest frequency component of the lightning pulse waveform is about 10 MHz, and the main energy is distributed below 30 kHz. A high-pass filter is used to filter the lightning pulse energy to achieve the lightning protection function.

[0004] Patent 202211222073.6, a radio frequency signal lightning protector, adopts a simple design principle of an L, C high-pass filter, and designs a high-pass filter circuit for lightning pulses composed of 1 capacitor element C and 1 inductor element L. By selecting devices with a withstand voltage > 600V to meet the requirements of lightning protection levels 3 and 4, the circuit structure is simple, but this circuit structure is difficult to meet the lightning protection requirements of the highest level 5. Due to the distribution parameter limitations of the filter elements, it is also difficult to expand to the X-band and even higher frequencies. According to the test data of lightning indirect effect waveforms 3 and 4 provided by this patent, the positive pulse clamping voltage of its waveform 3 is 78V, and the negative pulse clamping voltage is -80V; the positive pulse clamping voltage of waveform 4 is 13V, and the negative pulse clamping voltage is -12.8V. Therefore, the residual voltage of this lightning protection circuit is still relatively large and cannot meet the requirement that the lightning pulse residual voltage of low-power radio frequency devices < 5V.

[0005] Therefore, it is necessary to provide a protection device that can solve the problems that it is difficult to miniaturize and lightweight the protection design against the indirect lightning effect of level 5, the highest level, for the X-band RF port of airborne electronic equipment and the excessive residual voltage. Summary of the Invention

[0006] In order to solve the above problems, the object of the present invention is to provide an X-band RF signal lightning protection device that can meet the protection requirements for all lightning pulse waveform levels 1-5.

[0007] To achieve the above object, the present invention provides the following technical solution. An X-band RF signal lightning protection device, the device includes: a microstrip printed circuit board and a lightning protection circuit soldered on the microstrip printed circuit board. The lightning protection circuit includes a 1 / 4 wavelength short circuit line and an LTCC high-pass filter. The 1 / 4 wavelength short circuit line and the LTCC high-pass filter are connected in series, and the 1 / 4 wavelength short circuit line is grounded.

[0008] The X-band RF signal lightning protection device provided by the present invention also has the following characteristics. The line width w of the microstrip on the microstrip printed circuit board is greater than the fusing width W of the microstrip. fuse , the fusing width W of the microstrip fuse is obtained by calculating through the thickness T of the microstrip h , the transient current I required for the microstrip to fuse fuse and the time t required for the microstrip to fuse.

[0009] The X-band RF signal lightning protection device provided by the present invention also has the following characteristics. The fusing width W of the microstrip fuse is:

[0010]

[0011] where, T h is the thickness of the microstrip, I(t) is the lightning pulse current, and t is the time required for the microstrip to fuse.

[0012] The X-band RF signal lightning protection device provided by the present invention also has the following characteristics. The thickness Z of the dielectric layer of the microstrip printed circuit board 0 is obtained by calculating through the line width w of the microstrip.

[0013] The X-band RF signal lightning protection device provided by the present invention also has the following characteristics. The thickness h of the dielectric layer of the microstrip printed circuit board is obtained by the following formula:

[0014]

[0015] where, Z 0 is the characteristic impedance of the microstrip, εr is the relative permittivity of the dielectric layer, ε′ r is the effective relative permittivity, and h is the thickness of the dielectric layer.

[0016] The X-band RF signal lightning protection device provided by the present invention also has the following characteristics: a three-dimensional model of a microstrip line and a 1 / 4 wavelength short circuit line is established in simulation software, and the insertion loss and standing wave ratio indexes of the lightning protection circuit in the X-band are simulated and optimized to obtain the length of the 1 / 4 wavelength short circuit line.

[0017] The X-band RF signal lightning protection device provided by the present invention also has the following characteristics: the LTCC high-pass filter is arranged at the rear end of the 1 / 4 wavelength short circuit line, and the LTCC high-pass filter is an X-band LTCC high-pass filter.

[0018] The X-band RF signal lightning protection device provided by the present invention also has the following characteristics: the insertion loss of the X-band LTCC high-pass filter within the X-band passband does not exceed the design requirement value IL of the RF circuit S21 , and the standing wave ratio is not greater than the required value VSWR; the typical loss value in the stopband > 30 dB, and the minimum is not less than 20 dB.

[0019] Beneficial effects

[0020] The X-band RF signal lightning protection device provided by the present invention has a small number of component elements, realizes miniaturization and light weight, has a simple circuit form and high portability; this protection device can meet the protection requirements of all lightning pulse levels 1-5, and the measured clamping voltages for the waveform 5A level 5 lightning impulse reach +3.9V and -3.4V. Description of the drawings

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 is a schematic diagram of the composition of the protection device provided by the embodiment of the present invention;

[0023] Figure 2 is a 1 / 4 wavelength short circuit line model provided by the embodiment of the present invention;

[0024] Figure 3 is the insertion loss and standing wave ratio simulation curve of the 1 / 4 wavelength short circuit line model provided by the embodiment of the present invention;

[0025] Figure 4The measured curves of the insertion loss and voltage standing wave ratio of the 1 / 4-wavelength short-circuit line model provided by the embodiments of the present invention;

[0026] Figure 5 The positive pulse test residual voltage waveform diagram of the pin injection test of waveform 5A level 5 for the protection device provided by the embodiments of the present invention;

[0027] Figure 6 The negative pulse test residual voltage waveform diagram of the pin injection test of waveform 5A level 5 for the protection device provided by the embodiments of the present invention;

[0028] Figure 7 The test residual voltage waveform diagram of the pin injection test of waveform 3 level 5 for the protection device provided by the embodiments of the present invention. Detailed implementation manners

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be noted that these embodiments are not limitations on the present invention. Any equivalent transformation or substitution in terms of function, method, or structure made by those of ordinary skill in the art based on these embodiments shall fall within the protection scope of the present invention.

[0030] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0031] In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0032] The terms "mounted", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0033] Such asFigures 1-7 As shown in Figures 1-7 , an embodiment of the present invention provides an X-band radio frequency signal lightning protection device, which includes a microstrip printed circuit board and a lightning protection circuit soldered on the microstrip printed circuit board. The lightning protection circuit includes a 1 / 4 wavelength short circuit line and an LTCC high-pass filter. The 1 / 4 wavelength short circuit line and the LTCC high-pass filter are connected in series, and the 1 / 4 wavelength short circuit line is grounded.

[0034] In the above embodiment, the provided protection device uses a microstrip printed circuit board as a carrier, and consists of a 1 / 4 wavelength short circuit line and an LTCC high-pass filter to form a two-stage lightning protection circuit. The 1 / 4 wavelength short circuit line realizes the first-stage lightning pulse clamping circuit, and the LTCC high-pass filter realizes the clamping of the second-stage lightning pulse. Utilizing the 1 / 4 wavelength impedance transformation principle of the transmission line, the short circuit line with a length of 1 / 4 wavelength is equivalent to an open circuit for the radio frequency signal in the working frequency band, and is equivalent to a ground short circuit for the lightning pulse energy, so that the lightning pulse energy is discharged to the ground. This protection circuit can be used for the protection of X-band radio frequency signals against all lightning indirect effect pulse waveform levels 1-5, and its insertion loss is <2 dB and the voltage standing wave ratio is <2 in the frequency band of 8 GHz to 12 GHz.

[0035] In some embodiments, the line width w of the microstrip on the microstrip printed circuit board is greater than the fusing width W of the microstrip. fuse The fusing width W of the microstrip fuse is calculated through the thickness T of the microstrip, h the transient current I required for the microstrip to fuse, fuse and the time t required for the microstrip to fuse.

[0036] In the above embodiment, when a lightning pulse reaches the input port of the radio frequency lightning protection printed circuit board, if the energy of the lightning transient pulse exceeds the pulse energy limit that the microstrip can withstand, the microstrip will be fused. Therefore, the width of the microstrip that meets the requirements should be calculated according to the magnitude of the lightning pulse energy, and an appropriate margin should be designed to prevent the microstrip from being fused and causing the failure of lightning protection.

[0037] When a transient pulse current passes through the microstrip, the transient pulse energy required for the microstrip to fuse is shown in formula (1):

[0038]

[0039] In the formula, I fuse is the transient current required for the microstrip to fuse, t is the time required for the microstrip to fuse, and R is the resistance of the microstrip. Their calculation formulas are shown in formulas (2) to (4) respectively.

[0040] I fuse = 12277×A 0.75 (2)

[0041] t = 0.233 × A 0.5 (3)

[0042]

[0043] Wherein, A is the cross-sectional area of the microstrip line, ρ is the resistivity, and l is the length of the microstrip line.

[0044] When a lightning pulse current passes through the microstrip line, the calculation of the transient energy of the lightning pulse can be seen in formula (5):

[0045] E transient = ∫I 2 (t)Rdt (5)

[0046] Let the transient energies of formula (1) and formula (5) be equal, and substitute formula (2) and formula (3) at the same time. The line width when the microstrip line is fused under the action of this lightning pulse can be calculated as shown in formula (6):

[0047]

[0048] Wherein, W fuse is the fused line width of the microstrip line (mil), and T h is the thickness of the microstrip line (mil).

[0049] The double-exponential function calculation formulas of the lightning indirect effect pin injection test waveforms 4 and 5A are shown in formulas (7) and (8):

[0050]

[0051] When a lightning pulse passes through the microstrip line, the magnitude of the pulse current can be calculated by the following formula:

[0052]

[0053] Wherein, V residual represents the lightning residual voltage after passing through a 1 / 4-wavelength short circuit line, R s is the internal resistance of the lightning pulse source, R s = V OC / I SC , V OC is the open-circuit voltage, and I SC is the short-circuit current.

[0054] Since the magnitude of the residual voltage is much smaller than the pulse voltage amplitude of waveform 5A, for simplicity of calculation, the residual voltage V residualNeglected. Combining formulas (6) to (9), the widths of the microstrip fusing lines corresponding to waveforms 4 and 5A at the open-circuit voltages specified for different test levels can be calculated. The widths of the microstrip fusing lines corresponding to level 5 are shown in Table 1. Assuming the copper thickness of the printed circuit board is 1 oz (1.4 mil), the width of the microstrip fusing line is 56 mil. To increase the safety margin, a derating design of 65% is adopted, and the width of the microstrip line is designed to be 86 mil.

[0055] Table 1 Widths of the microstrip fusing lines corresponding to waveforms 4 and 5A at level 5

[0056]

[0057] In some embodiments, the thickness Z0 of the dielectric layer of the microstrip printed circuit board is obtained by calculating based on the width w of the microstrip line.

[0058] In some embodiments, the thickness h of the dielectric layer of the microstrip printed circuit board is obtained by the following formula:

[0059]

[0060] where Z 0 is the characteristic impedance of the microstrip line, ε r is the relative dielectric constant of the dielectric layer, ε′ r is the effective relative dielectric constant, and h is the thickness of the dielectric layer.

[0061] In some embodiments, assume the printed circuit board adopts a two-layer board structure, with the microstrip line laid on the Top layer and the Bottom layer being the ground plane layer. The material of the intermediate dielectric layer is Rogers4003, and its relative dielectric constant is 3.55. Assume the characteristic impedance of the microstrip line is 50 Ω. According to formulas (10) and (11), the thickness of the dielectric layer of the printed circuit board can be calculated to be 39 mil.

[0062] In some embodiments, a three-dimensional model of the microstrip line and a 1 / 4-wavelength short circuit line is established in the simulation software, as Figure 2 shown. This model adopts wave port excitation and ideal conductor boundary conditions, where the wave port excitation is set on the input and output end faces of the microstrip line. A semicircular short circuit line is set in the center of the microstrip line, and the other end is connected to the GND of the bottom layer of the printed circuit board through a via. The insertion loss and standing wave ratio indexes of the lightning protection circuit in the X-band are simulated and optimized to optimize the insertion loss and standing wave ratio indexes of the lightning protection circuit in the X-band, and the length of the 1 / 4-wavelength short circuit line is obtained. The optimal value of the radius R of the semicircular short circuit line in this model is 2.8 mm. At this time, the length of the short circuit line is 8.8 mm, and its insertion loss and standing wave ratio simulation curves are as Figure 3 shown.

[0063] In some embodiments, the LTCC high-pass filter is disposed at the rear end of the 1 / 4 wavelength short circuit line, and the LTCC high-pass filter is an X-band LTCC high-pass filter.

[0064] Setting an X-band LTCC high-pass filter at the rear end of the 1 / 4 wavelength short circuit line can further reduce the residual voltage of the lightning pulse, so that the residual voltage meets the index requirement of <5V under the action of the lightning pulse of the highest level 5 (such as 1600V / 1600A).

[0065] In some embodiments, the insertion loss of the X-band LTCC high-pass filter within the X-band passband does not exceed the design requirement value I LS21 of the RF circuit, and the voltage standing wave ratio is not greater than the requirement value VSWR; the typical loss value in the stopband >30dB, and the minimum is not less than 20dB.

[0066] Since most of the energy of the lightning surge is discharged through the 1 / 4 wavelength short circuit line, the voltage withstand requirement for the LTCC high-pass filter is relatively low. Select an X-band LTCC high-pass filter, whose insertion loss within the X-band passband does not exceed the design requirement value I LS21 of the RF circuit, and the voltage standing wave ratio is not greater than the requirement value VSWR; the typical loss value in the stopband >30dB, and the minimum is not less than 20dB.

[0067] In some embodiments, by selecting LTCC or cavity filters in the corresponding frequency bands, the operating frequency of the RF lightning protector can be extended to frequency bands such as L, S, C, and Ku.

[0068] In some embodiments, according to the design and simulation results, the printed circuit board is processed. The φ0.8mm copper wire is used as the 1 / 4 wavelength short circuit line and welded to the ground. The model of the RF connector at both ends of the microstrip line is SMA-KFD46B. After the 1 / 4 wavelength short circuit line is welded, the measured curves of its insertion loss and voltage standing wave ratio are as Figure 4 shown. In the X-band, the maximum insertion loss <0.38dB and the voltage standing wave ratio <1.3. After welding the ZHHF3216-7150 high-pass filter at the rear end of the 1 / 4 wavelength short circuit line, the pin injection tests of waveform 5A level 5 (1600V / 1600A) and waveform 3 level 5 (3200V / 128A) are carried out, and the measured residual voltage curves are as Figures 5-7 shown. The maximum residual voltage for the positive polarity pulse of waveform 5A level 5 is 3.9V, the maximum residual voltage for the negative polarity pulse of waveform 5A level 5 is -3.4V, and the maximum residual voltage for waveform 3 level 5 is 4.8V. Therefore, the residual voltage index of this X-band RF lightning protector meets the design requirement of <5V.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and variations can be made, and these improvements and variations should also be regarded as within the protection scope of the present invention.

Claims

1. An X-band radio frequency signal lightning protection device, characterized in that: The device comprises: a microstrip line printed board and a lightning protection circuit welded on the microstrip line printed board, The lightning protection circuit includes a 1 / 4 wavelength short-circuit line and a LTCC high-pass filter. The 1 / 4 wavelength short-circuit line and the LTCC high-pass filter are connected in series. The 1 / 4 wavelength short circuit is grounded.

2. The X-band radio frequency signal lightning protection device according to claim 1, characterized in that: The line width w of the microstrip line on the microstrip line printed board is greater than the fuse width W of the microstrip line fuse , the fuse width W of the microstrip line fuse The thickness T of the microstrip line h 、The transient current I required for the microstrip line to fuse fuse And the time t required for the microstrip line to fuse is calculated.

3. The X-band radio frequency signal lightning protection device according to claim 2, characterized in that: The fuse width W of the microstrip line fuse for: Among them, T h is the thickness of the microstrip line, I(t) is the lightning pulse current, and t is the time required for the microstrip line to fuse.

4. The X-band radio frequency signal lightning protection device according to claim 1, characterized in that: The thickness Z0 of the dielectric layer of the microstrip printed board is obtained by calculating the line width w of the microstrip line.

5. The X-band radio frequency signal lightning protection device according to claim 4, characterized in that: The thickness h of the dielectric layer of the microstrip printed circuit board is obtained by the following formula: Where Z0 is the characteristic impedance of the microstrip line, ε r is the relative dielectric constant of the dielectric layer, ε' r is the effective relative dielectric constant, and h is the thickness of the dielectric layer.

6. The X-band radio frequency signal lightning protection device according to claim 1, characterized in that: A three-dimensional model of the microstrip line and the 1 / 4 wavelength short-circuit line was established in the simulation software, and the insertion loss and standing wave ratio indicators of the lightning protection circuit in the X-band were simulated and optimized to obtain the length of the 1 / 4 wavelength short-circuit line.

7. The X-band radio frequency signal lightning protection device according to claim 1, characterized in that: The LTCC high-pass filter is arranged at the rear end of the 1 / 4 wavelength short-circuit line, and the LTCC high-pass filter is an X-band LTCC high-pass filter.

8. The X-band radio frequency signal lightning protection device according to claim 7, characterized in that: The insertion loss of the X-band LTCC high-pass filter in the X-band passband does not exceed the design requirement value IL of the RF circuit. S21 , the standing wave ratio is not greater than the required value VSWR; The typical loss in the stop band is >30dB, and the minimum is not less than 20dB.

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