Distributed broadband multi-frequency filter

Abstract

The invention provides a distributed broadband multi-frequency filter, relates to the technical field of broadband multi-frequency filters, and realizes dynamic adaptation of dielectric constants in a broadband through collaborative design of a gradient dielectric substrate and asymmetric coupling, remarkably reduces signal transmission loss and improves multi-frequency isolation performance. The cross coupling module generates controllable transmission zero points on the two sides of a passband, and the out-of-band rejection capability boundary of a traditional filter is broken through. The defect ground array accurately suppresses parasitic resonance and ensures the integrity of high-frequency signals; the conformal packaging structure achieves thermal stability and mechanical robustness under high power through thermal-mechanical coupling optimization. The collaborative optimization problems of broadband impedance matching, multi-frequency interference suppression, high power reliability and the like are optimized, and the development trend of high-frequency systems such as 5G / 6G communication, satellite internet and the like is better met.

Description

Technical Field

[0001] The present invention relates to the technical field of broadband multi - frequency filters, and particularly to a distributed broadband multi - frequency filter. Background Art

[0002] Current broadband multi - frequency filters face multiple technical bottlenecks in 5G communication, satellite payloads, and radar systems: due to the single dielectric constant of traditional uniform dielectric substrates, the surface wave loss in the high - frequency band is significant (>1.5 dB / cm), and when multi - frequency signals are transmitted synergistically, the in - band ripple deterioration (more than ±1.2 dB) is likely to be caused by impedance mismatch; the stepped matching network is limited by the fixed unit size and it is difficult to achieve continuous impedance transformation in the 1 - 6 GHz wide - frequency band, and the insufficient isolation degree between frequency bands (<30 dB) causes channel crosstalk; the symmetric coupling structure can only generate limited transmission zeros on one side of the passband, and the out - of - band rejection slope is low (<60 dB / GHz), which cannot meet the requirements of adjacent - frequency interference suppression in the millimeter - wave band; in addition, due to the thermal expansion mismatch of traditional metal packaging, thermal stress deformation is likely to occur in power scenarios above 30W, resulting in an excessive temperature drift of the filter (>50 ppm / ℃). These defects seriously restrict the channel capacity and reliability of high - frequency communication devices in scenarios such as Massive MIMO base stations and low - earth - orbit satellite phased arrays.

[0003] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present disclosure, and thus it may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide a distributed broadband multi - frequency filter to solve the problems raised in the above - mentioned background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A distributed broadband multi - frequency filter specifically includes: A high - dielectric - constant substrate module, which includes a gradient dielectric layer and a silver - plated carrier board, and is used to realize the electromagnetic field constraint and heat conduction of the whole multi - frequency filter; A multi - frequency matching module, which is arranged on the surface of the high - dielectric - constant substrate module and includes four groups of independent matching network units, and is used to process signals of different frequencies; A cross - coupling module, which is arranged between the four groups of matching network units and is used to generate transmission zeros; A DGS suppression module, which is etched on the back of the silver - plated carrier board of the high - dielectric - constant substrate module and is used to suppress parasitic resonance; A conformal packaging module, which covers the surface of the high - dielectric - constant substrate module and is used to improve the overall power capacity of the multi - frequency filter.

[0006] Preferably, the gradient dielectric layer in the high-dielectric substrate module is composed of three layers of composite dielectrics, and the distribution of the dielectric constant along the thickness direction satisfies: ; In the formula represents the dielectric constant at the vertical coordinate of , represents the vertical coordinate, , where represents the total thickness of the dielectric, , in mm, represents the top-layer dielectric constant, , represents the change in dielectric constant, , represents the attenuation coefficient, .

[0007] Preferably, all four groups of the matching network units adopt an exponentially tapered microstrip line structure, and the characteristic impedance change satisfies: ; where represents the characteristic impedance corresponding to the microstrip line length of , represents the preset initial impedance, represents the taper coefficient, , represents the microstrip line length; The unit spacing between adjacent two groups of the matching network units needs to be greater than the minimum spacing, and the calculation method of the minimum spacing is: ; In the formula represents the minimum spacing, represents the preset center frequency, represents the speed of light, represents the center frequency difference between adjacent two groups of the matching network units, , both represent scale factors, and their value ranges are both between 0.2 and 0.3, where satisfies: , represents the effective dielectric constant of the high-dielectric substrate module.

[0008] Preferably, the calculation method of the effective dielectric constant is: ; In the formula represents the electric field distribution function in the direction perpendicular to the substrate of the high-dielectric substrate module, expressed as: ; In the formula and represent the boundary electric field and satisfy: ; In the formula represents the operating voltage of the entire multi - frequency filter, represents the microstrip line width.

[0009] Preferably, the cross - coupling module includes several groups of L - shaped stub units, and the calculation methods of the stub length and coupling spacing are respectively: ; ; In the formula and respectively represent the stub length and coupling spacing of the L - shaped stub unit, and respectively represent the length adjustment coefficient and spacing adjustment coefficient, , , represents the voltage standing - wave ratio, represents the quality factor, and .

[0010] Preferably, a cross - slot array is provided in the DGS suppression module, and the calculation methods of the slot length and slot width of each group of cross - slots are respectively: ; ; In the formula and respectively represent the slot length and slot width of the cross - slot, and , , represents the parasitic resonance frequency, , and respectively represent the frequency adjustment factor and the width - to - length ratio coefficient, , .

[0011] Preferably, the conformal packaging module uses an aluminum nitride ceramic housing with a wall thickness of 0.2 - 0.5 mm and a surface roughness less than 0.1 μm, and the calculation method of its thermal expansion coefficient matching degree is: ; In the formula represents the thermal expansion matching degree, and respectively represent the thermal expansion coefficients of the conformal encapsulation module and the high-dielectric substrate module, and the matching degree of the thermal expansion coefficient of the conformal encapsulation module satisfies .

[0012] Preferably, the aluminum nitride ceramic housing is processed by a laser-activated metallization process, wherein the bonding strength of the metallization layer is greater than 45 MPa, specifically including: a titanium-tungsten bonding layer with a thickness of 0.5 um ± 0.05 um; a nickel-vanadium barrier layer with a thickness of 1 um ± 0.1 um; a gold bonding layer with a thickness of 0.5 um ± 0.15 um.

[0013] Compared with the prior art, the beneficial effects of the present invention are: Through the collaborative design of the gradient dielectric substrate and the asymmetric coupling, the present invention realizes the dynamic adaptation of the dielectric constant within a wide frequency band, significantly reduces the signal transmission loss and improves the multi-frequency isolation performance; the cross-coupling module generates controllable transmission zeros on both sides of the passband, breaking through the out-of-band rejection ability boundary of the traditional filter; the defected ground array precisely suppresses the parasitic resonance to ensure the high-frequency signal integrity; the conformal encapsulation structure achieves thermal stability and mechanical robustness under high power through thermo-mechanical coupling optimization. The present invention optimizes the collaborative optimization problems such as wide-band impedance matching, multi-frequency interference suppression, and high-power reliability, and is more in line with the development trend of high-frequency systems such as 5G / 6G communication and satellite Internet. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of the overall structure of the present invention; Figure 2 is a schematic diagram of the simulation structure of the present invention; Figure 3 is the simulation waveform of the present invention; Figure 4 is the measured waveform of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0016] It should be noted that unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left" and "right" are only used to represent relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0017] Embodiment: Please refer to Figures 1 to 4 , the present invention provides a technical solution: A distributed broadband multi-frequency filter, specifically including: a high-dielectric substrate module, a multi-frequency matching module, a cross-coupling module, a DGS suppression module, and a conformal packaging module.

[0018] The high-dielectric substrate module includes a gradient dielectric layer and a silver-plated carrier board, and is used to realize the electromagnetic field constraint and heat conduction of the overall multi-frequency filter.

[0019] The gradient dielectric layer in the high-dielectric substrate module is composed of three layers of composite dielectrics, and the distribution of its dielectric constant along the thickness direction satisfies: ; In the formula represents the dielectric constant at the vertical coordinate of , represents the vertical coordinate, , where represents the total thickness of the dielectric, , with the unit of mm, represents the top-layer dielectric constant, , represents the change in dielectric constant, , where the top-layer dielectric constant and the change in dielectric constant can be determined by the composite dielectric optimization theory in materials science and verified by high-frequency electromagnetic simulation, so as to ensure a smooth transition of the dielectric gradient, represents the attenuation coefficient, , which can be optimized by the simulation of the electromagnetic field energy distribution to balance the requirements of surface wave suppression and electric field constraint.

[0020] In this step, the dielectric constant of the high-dielectric substrate module is described by the Gaussian attenuation mode, which can significantly reduce the reflection at the dielectric layer interface, enhance the electromagnetic field confinement ability, and achieve low-loss transmission within a wide frequency band. Compared with the traditional uniform dielectric structure, this solution improves the cooperative working stability of multi-frequency signals, provides an ideal electromagnetic environment basis for the multi-frequency matching network, and can also establish the mapping relationship between the dielectric gradient - field distribution, laying the foundation for multi-frequency cooperation.

[0021] The multi-frequency matching module is arranged on the surface of the high-dielectric substrate module and includes four groups of independent matching network units for processing signals of different frequencies. All four groups of matching network units adopt the exponential tapered microstrip line structure, and the characteristic impedance change satisfies: ; where represents the characteristic impedance corresponding to the microstrip line length of , represents the preset initial impedance, represents the gradient coefficient, which can be determined by using the multi-objective optimization algorithm by combining the impedance matching theory and the standing wave ratio simulation results. Specifically, its value range is generally within , represents the microstrip line length; The unit spacing between adjacent two groups of matching network units needs to be greater than the minimum spacing, and the calculation method of the minimum spacing is: ; In the formula represents the minimum spacing, represents the preset center frequency, represents the speed of light, represents the center frequency difference between adjacent two groups of matching network units, , both represent the scaling factors, and their specific sizes can be determined based on the electromagnetic coupling strength analysis and optimized by the parameter scanning method. And the value ranges of both are between 0.2 and 0.3. Among them satisfies: , represents the effective dielectric constant of the high-dielectric substrate module.

[0022] The calculation method of the effective dielectric constant is: ; The exponential tapered structure can achieve continuous impedance transformation within a wide frequency band, breaking through the bandwidth limitation of the traditional stepped impedance transformer. Dynamically adjusting the unit spacing effectively suppresses the crosstalk between frequency bands, provides a physical isolation guarantee for independent processing of multi-frequency signals, and significantly improves the purity of the passband signal.

[0023] In the formula represents the electric field distribution function in the direction perpendicular to the substrate of the high-dielectric substrate module, and is expressed as: ; In the formula and represent the boundary electric field and satisfy: ; In the formula represents the operating voltage of the entire multi-frequency filter, represents the width of the microstrip line.

[0024] In this step, the exponential gradient structure realizes continuous impedance transformation within a wide frequency band, breaking through the bandwidth limitation of the traditional stepped impedance transformer. Dynamically adjusting the unit spacing effectively suppresses crosstalk between frequency bands, provides physical isolation guarantee for independent processing of multi-frequency signals, significantly improves the purity of passband signals, and can be optimized by genetic algorithm for multi-objectives and verified by time domain reflectometer measurement to achieve the Pareto optimum of impedance matching bandwidth and isolation.

[0025] The cross-coupling module is arranged between four groups of matching network units and is used to generate transmission zeros.

[0026] The cross-coupling module includes several groups of L-shaped stub units, and the calculation methods of the stub length and coupling spacing are respectively: ; ; In the formula and respectively represent the stub length and coupling spacing of the L-shaped stub unit, and respectively represent the length adjustment coefficient and spacing adjustment coefficient, which can be jointly calibrated through the coupling coefficient analysis model and full-wave electromagnetic simulation and are used to optimize the position of the transmission zero. Specifically, their value ranges are generally in , , represents the voltage standing wave ratio, represents the quality factor, and , The value constraint is derived based on the resonant cavity energy loss theory to ensure the out-of-band rejection performance.

[0027] In this step, the asymmetric coupling design introduces controllable transmission zeros on both sides of the passband, which can break through the frequency selectivity bottleneck of the traditional symmetric coupling structure. By dynamically adjusting the geometric parameters of the stub, the out-of-band rejection ability is adaptively improved, significantly enhancing the frequency roll-off characteristic of the filter. Moreover, after analyzing through the coupled-mode theory and scanning the HFSS full-wave simulation parameters, the position of the transmission zero can be accurately controlled, breaking through the theoretical limit of out-of-band rejection.

[0028] The DGS suppression module is etched on the back of the silver-plated carrier of the high-dielectric substrate module to suppress parasitic resonance.

[0029] The DGS suppression module is provided with a cross-slot array. The calculation methods of the slot length and slot width of each group of cross-slots are as follows: ; ; In the formula and respectively represent the slot length and slot width of the cross-slot, and , , represents the parasitic resonance frequency, , , respectively represent the frequency adjustment factor and the width-to-length ratio coefficient. Specifically, the values of the two can be determined by the parasitic resonance mode analysis and experimental calibration method, and are dynamically adapted in combination with the dielectric characteristics of the substrate. , .

[0030] In this step, the cross-slot array can accurately suppress the parasitic resonance in a specific frequency band, breaking through the limitation of the single-frequency point suppression of the traditional DGS structure. The periodic defected ground design reconstructs the current distribution, significantly improving the steepness of the passband edge and providing guarantee for the signal integrity in the high-frequency band.

[0031] The conformal packaging module covers the surface of the high-dielectric substrate module to improve the overall power capacity of the multi-band filter.

[0032] The conformal packaging module uses an aluminum nitride ceramic shell with a wall thickness of 0.2 - 0.5 mm and a surface roughness less than 0.1 μm. The calculation method of its thermal expansion coefficient matching degree is as follows: ; In the formula represents the thermal expansion matching degree, and respectively represent the thermal expansion coefficients of the conformal packaging module and the high-dielectric substrate module, which can be optimized based on the material thermodynamics property database and then verified by the finite element thermal stress simulation for the matching degree. And the thermal expansion coefficient matching degree of the conformal packaging module satisfies .

[0033] The aluminum nitride ceramic housing is processed using a laser-activated metallization process, where the bonding strength of the metallization layer is greater than 45 MPa. Specifically, the thickness of the metallization layer is determined through an electronic packaging reliability model and process tolerance analysis, specifically including: A titanium-tungsten bonding layer with a thickness of 0.5 um ± 0.05 um; A nickel-vanadium barrier layer with a thickness of 1 um ± 0.1 um; A gold bonding layer with a thickness of 0.5 um ± 0.15 um.

[0034] In this step, the co-design of the thermal expansion of heterogeneous materials can significantly reduce the temperature cycle stress and overcome the problem of deterioration of the high-temperature performance of traditional packaging structures. The optimization of the multi-layer metallization interface can not only improve the heat dissipation efficiency and mechanical stability, but also, through the matching of the material thermal expansion coefficient database and COMSOL thermal stress simulation, can achieve the thermodynamic stability design of the heterogeneous material interface, providing a reliable guarantee for high-power application scenarios.

[0035] Specifically, a common I / O port (COM) and four groups of independent RF I / O ports (RF1~RF4) are provided on the high-dielectric substrate module. Four mutually independent matching network units (F1~F4) are respectively arranged between the common I / O port and the RF I / O ports. The L-shaped stub units (P1~P6) of the cross-coupling module are used to connect the four mutually independent matching network units. Figure 3 This is the measured waveform of the present invention in the simulation state, Figure 4 This is the measured waveform after the actual production of the present invention. Referring to its simulation waveform and measured waveform, it can be seen that the difference between the two is not large, and it can well achieve the functional indicators required by the design, realizing the optimization goals of multi-band, ultra-wideband, and low loss.

[0036] In summary, through the co-design of the gradient dielectric substrate and asymmetric coupling, the present invention realizes the dynamic adaptation of the dielectric constant within a wide frequency band, significantly reduces the signal transmission loss and improves the multi-frequency isolation performance; the cross-coupling module generates controllable transmission zeros on both sides of the passband, breaking through the out-of-band rejection ability boundary of traditional filters; the defected ground array precisely suppresses parasitic resonance to ensure the integrity of high-frequency signals; the conformal packaging structure achieves thermal stability and mechanical robustness under high power through thermo-mechanical coupling optimization. It optimizes the collaborative optimization problems such as wideband impedance matching, multi-frequency interference suppression, and high-power reliability, and is more in line with the development trend of high-frequency systems such as 5G / 6G communication and satellite Internet.

[0037] The above formulas are all dimensionless and take their numerical values for calculation. The formula is obtained by collecting a large amount of data for software simulation to obtain a formula that is closest to the real situation. The preset parameters in the formula are set by those skilled in the art according to the actual situation.

[0038] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. Those skilled in the art will realize that the units and algorithm steps of the examples described in connection with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0039] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units. They may be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0040] As described above, only the specific implementation manners of this application are provided, but the protection scope of this application is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and all of them should be covered by the protection scope of this application.

Claims

1. A distributed broadband multi-frequency filter, characterized in that: Specifically include: A high dielectric substrate module, comprising a gradient dielectric layer and a silver-plated carrier plate, for achieving electromagnetic field confinement and heat conduction of the multi-frequency filter as a whole; A multi-frequency matching module, which is arranged on the surface of the high dielectric substrate module and includes four groups of independent matching network units for processing signals of different frequencies; A cross-coupling module, which is arranged between four groups of matching network units and is used to generate a transmission zero point; A DGS suppression module, which is etched on the back of the silver-plated carrier of the high-dielectric substrate module to suppress parasitic resonance; A conformal packaging module covers the surface of the high dielectric substrate module to improve the overall power capacity of the multi-frequency filter.

2. A distributed broadband multi-frequency filter according to claim 1, characterized in that: The gradient dielectric layer in the high dielectric substrate module is composed of three layers of composite dielectrics, and the distribution of its dielectric constant along the thickness direction satisfies: ； In the formula The vertical coordinate is The dielectric constant at represents the vertical coordinate, ,in Indicates the total thickness of the medium, , unit is mm, represents the top dielectric constant, , represents the change in dielectric constant, , represents the attenuation coefficient, .

3. A distributed broadband multi-frequency filter according to claim 2, characterized in that: The four groups of matching network units all adopt an exponential gradient microstrip line structure, and the characteristic impedance change satisfies: ； in The length of the microstrip line is The corresponding characteristic impedance is represents the preset initial impedance, represents the gradient coefficient, , represents the length of the microstrip line; The unit spacing between two adjacent sets of matching network units needs to be greater than the minimum spacing. The minimum spacing is calculated as follows: ； In the formula Indicates the minimum spacing, Indicates the preset center frequency. represents the speed of light, It represents the difference between the central and western frequencies of two adjacent matching network units. , Both represent proportional factors, and their value ranges are between 0.2 and 0.

3. satisfy: , Indicates the effective dielectric constant of the high dielectric substrate module.

4. A distributed broadband multi-frequency filter according to claim 3, characterized in that: The effective dielectric constant is calculated as: ； In the formula It represents the electric field distribution function of the high dielectric substrate module in the direction perpendicular to the substrate, which is expressed as: ； In the formula , represents the boundary electric field, satisfying: ； In the formula Represents the overall operating voltage of the multi-frequency filter, Represents the width of the microstrip line.

5. A distributed broadband multi-frequency filter according to claim 3, characterized in that: The cross-coupling module includes a plurality of groups of L-shaped branch units, and the branch length and coupling spacing thereof are calculated as follows: ； ； In the formula , represent the branch length and coupling spacing of the L-type branch unit, , They represent the length adjustment coefficient and the spacing adjustment coefficient respectively. , , represents the voltage standing wave ratio, represents the quality factor, and .

6. A distributed broadband multi-frequency filter according to claim 3, characterized in that: The DGS suppression module is provided with a cross slot array, and the slot length and slot width of each group of cross slots are calculated as follows: ； In the formula , Respectively represent the slot length and slot width of the cross slot, and , , represents the parasitic resonant frequency, , , denote the frequency adjustment factor and the aspect ratio coefficient respectively, , .

7. A distributed broadband multi-frequency filter according to claim 1, characterized in that: The conformal packaging module adopts an aluminum nitride ceramic shell with a wall thickness of 0.2-0.5 mm and a surface roughness of less than 0.1 um. The calculation method of the thermal expansion coefficient matching is: ； In the formula Indicates the thermal expansion matching degree, , They represent the thermal expansion coefficients of the conformal packaging module and the high dielectric substrate module, respectively, and the thermal expansion coefficient matching degree of the conformal packaging module satisfies .

8. A distributed broadband multi-frequency filter according to claim 7, characterized in that: The aluminum nitride ceramic shell is processed by a laser activated metallization process, wherein the bonding strength of the metallization layer is greater than 45 MPa, specifically comprising: Titanium-tungsten bonding layer, thickness 0.5um±0.05um; Nickel-vanadium barrier layer, thickness 1um±0.1um; Gold bonding layer, thickness is 0.5um±0.15um.

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