CN109216838B - Improved defected ground structure low-pass filter - Google Patents
Improved defected ground structure low-pass filter Download PDFInfo
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- CN109216838B CN109216838B CN201811085973.4A CN201811085973A CN109216838B CN 109216838 B CN109216838 B CN 109216838B CN 201811085973 A CN201811085973 A CN 201811085973A CN 109216838 B CN109216838 B CN 109216838B
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- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
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Abstract
The invention discloses an improved defected ground structure low-pass filter. The invention adopts a special two-step impedance structure unit, the step impedance unit adopts a structure mode that a narrow rectangular connection hexagonal structure unit is adopted, the length of the step impedance structure unit can be shortened under the condition of not reducing load Q, great freedom degree is provided on the structure and the design, and the miniaturization of the microwave device is easy to realize. In addition, the invention optimizes the defected ground structure at the bottom, changes the effective dielectric constant distribution of the substrate material, and further influences the current distribution of the grounding plate and the transmission characteristic of the microstrip transmission line. The inventive defected ground structure improves the low-pass filtering characteristic of the low-pass filter by improving the high-impedance frequency width and the out-of-band rejection strength of the low-pass filter. Moreover, the defected ground structure has the advantages of simple structure, convenience for electromagnetic field theoretical analysis and equivalent circuit modeling analysis, and suitability for practical application of integrated circuits.
Description
Technical Field
The invention belongs to the technical field of microwaves, and particularly relates to a defected ground structure low-pass filter.
Background
With the development of modern communication technology, the market has higher and higher requirements on the efficiency and the anti-interference of communication equipment, and research on high-performance microwave devices is correspondingly initiated. The low-pass filter can suppress harmonic signals and interference signals and provide a proper working bandwidth for the communication system. The traditional low-pass filter has large structure size, poor selectivity and weak out-of-band rejection capability, and is difficult to reject interference signals and higher harmonic signals. In recent years, a series of new structures such as a Photonic Band Gap (PBG), a stepped impedance cascade structure, an adjustable filter structure, and an Electromagnetic Band Gap (EBG) have been proposed internationally to solve the above problems. Although the structures improve the passband bandwidth and the out-of-band impedance suppression of the filter to a certain extent, the design and the processing of the structures are complex, and the engineering popularization and the application difficulty are high.
The Defected Ground Structure (DGS) is similar to the electromagnetic bandgap Structure, and the effective dielectric constant distribution of the substrate material is changed by etching a defect pattern on the Ground plate of the microstrip line, so that the current distribution of the Ground plate and the transmission characteristics of the microstrip transmission line are affected. The EBG structure needs to be loaded with a periodic structure, and is complex in modeling design and processing and difficult to miniaturize. Moreover, the band-stop characteristic parameters of the EBG structure are easily affected by various conditions, so the microwave device performance of the EBG structure is also unstable. The microstrip line of the DGS structure has band stop characteristic and slow wave characteristic, and compared with EBG, the DGS structure does not need a periodic structure and is relatively simple in structure. Moreover, the equivalent circuit and the electromagnetic field distribution of the DGS structure microstrip line are easy to model and analyze, so that the design, the processing and the application are convenient, and the miniaturization of the microwave device and the radio frequency circuit is easy to realize. Therefore, the development of microwave device design technology with new defected ground structure has a pressing need for miniaturization and integration of microwave circuit system.
Disclosure of Invention
The invention aims to provide an improved defected ground structure low-pass filter which has the advantages of easy integration, compact size, simple design, low cost and the like. Is convenient for mechanical processing and batch production, and can greatly promote the development of the industry.
The invention is realized by the following steps: the improved defected ground structure low-pass filter comprises a dielectric substrate, wherein a step impedance unit structure is arranged on the upper surface of the dielectric substrate, each side of the step impedance unit structure is provided with two steps, each step impedance unit structure consists of a rectangle and a hexagonal structure connected with the rectangle, and the rectangular structure part and the hexagonal structure part of each step impedance unit structure meet the requirement of impedance ratio in size and are connected to a transmission line; the lower surface of the medium substrate is provided with a metal grounding layer, the middle area of the metal grounding layer is provided with a defected ground structure, the defected ground structure comprises a longitudinal rectangular groove and three transverse rectangular grooves which are parallel to each other, the transverse rectangular grooves and the longitudinal rectangular grooves are staggered with each other, and the longitudinal rectangular grooves and the transverse rectangular grooves are directly communicated with the lower surface of the medium substrate.
The step impedance unit structure and the thickness of the metal layer are both 0.1 mm.
The dielectric substrate is made of a Rogers Ro4003 dielectric substrate material, the relative dielectric constant is 3.55, the loss tangent is 0.0027, and the thickness is 0.81 mm. The method has the characteristics of low dielectric loss, good cut-off adhesion of the conduction band metal and the substrate and the like.
Due to the adoption of the technical scheme, the microwave device adopts the special two-step impedance step structure unit, the impedance step unit adopts a structure mode of a hexagonal structure formed by connecting a narrow rectangular structure and a narrow rectangular structure, the length of the impedance step structure unit can be shortened under the condition of not reducing the load Q, great freedom is provided in structure and design, and the miniaturization of the microwave device is easy to realize. In addition, the invention optimizes the defected ground structure at the bottom, changes the effective dielectric constant distribution of the substrate material, and further influences the current distribution of the grounding plate and the transmission characteristic of the microstrip transmission line. The inventive defected ground structure improves the low-pass filtering characteristic of the low-pass filter by improving the high-impedance frequency width and the out-of-band rejection strength of the low-pass filter. Moreover, the defected ground structure has the advantages of simple structure, convenience for electromagnetic field theoretical analysis and equivalent circuit modeling analysis, and suitability for practical application of integrated circuits.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a bottom view of FIG. 1;
FIG. 3 is a top view of FIG. 1;
FIG. 4 is an equivalent circuit model of a DGS structure low-pass filter of the present invention;
FIG. 5 is an equivalent circuit simulation and HFSS simulation of the defected ground structure low pass filter of the present invention;
FIG. 6 is a diagram of HFSS simulation and actual measurement results of a defected ground structure according to the present invention.
Detailed Description
The embodiment of the invention comprises the following steps: the improved defected ground structure low-pass filter comprises a dielectric substrate 1, wherein a step impedance unit structure 2 is arranged on the upper surface of the dielectric substrate 1, two steps are arranged on each side of the step impedance unit structure 2, each step impedance unit structure 2 consists of a rectangular structure part 2-1 and a hexagonal structure part 2-2, the rectangular structure part and the hexagonal structure part of each step impedance unit structure 2 meet the requirement of impedance ratio in design, and the step impedance unit structure 2 is connected to a transmission line through the rectangular structure part 2-1; the lower surface of the dielectric substrate 1 is provided with a metal grounding layer 3, the middle area of the metal grounding layer 3 is provided with a groove to form a defected ground structure 4, the defected ground structure 4 comprises a longitudinal rectangular groove and three transverse rectangular grooves which are parallel to each other, the transverse rectangular grooves and the longitudinal rectangular grooves are staggered with each other, and the longitudinal rectangular grooves and the transverse rectangular grooves are directly communicated with the lower surface of the dielectric substrate 1. The thicknesses of the stepped impedance unit structure 2 and the metal layer 3 are both 0.1 mm.
The dielectric substrate 1 is made of Rogers Ro4003 dielectric substrate material, and has a relative dielectric constant of 3.55 and a loss tangent of 0.0027. The method has the characteristics of low dielectric loss, good cut-off adhesion of the conduction band metal and the substrate and the like.
In this embodiment, the dielectric substrate 1 is a RogersRo4003 dielectric substrate material with a relative dielectric constant of 3.55 and a loss tangent of 0.0027. The dielectric substrate has the characteristics of low dielectric loss, good cut-off adhesion between the conduction band metal and the substrate and the like, and is very suitable for being used as the dielectric substrate of the low-pass filter. The selection of the dielectric substrate 1 is important, and it is a propagation carrier of input and output signals, and directly affects important parameters such as transmission loss of signals, size of microwave devices, and power capacity of radio frequency circuits. Therefore, the selection of the dielectric substrate needs to be considered comprehensively, and particularly, the selection of the material and the size of the dielectric substrate need to be considered. The dielectric substrate 1 of the present embodiment is designed to have a thickness h of 0.81mm and a × b of 35mm × 28 mm.
The defected ground structure 4 of the invention enables the microstrip line formed by the DGS structure to have band stop characteristic and slow wave characteristic by changing the effective dielectric constant distribution of the substrate material, thereby influencing the current distribution of the ground plate and the transmission characteristic of the microstrip transmission line. This defected ground structure improves the low-pass filtering characteristic of the low-pass filter by increasing the high-impedance frequency width and the out-of-band rejection strength of the low-pass filter. Moreover, the defected ground structure has the advantages of simple structure, convenience for electromagnetic field theoretical analysis and equivalent circuit modeling analysis, and suitability for practical application of integrated circuits.
In fig. 2 and 3, the major structure size parameters of the inventive defected ground structure 4 low-pass filter are shown in table 1.
TABLE 1 defected ground structure low pass filter of the invention the main structure size parameter (unit: mm)
An equivalent circuit model is established by using ads (advanced designer summer), and the equivalent circuit model of the DGS structure low-pass filter is shown in fig. 4. L in equivalent circuit1，L3And C1，C2，C3Is the equivalent inductance and equivalent capacitance of the stepped impedance structure unit. Wherein C is4And L3The impedance circuit is formed to control the position of the notch point of the low pass filter of the defected ground structure 4. And an equivalent circuit model of the structural unit is researched, and a theoretical basis is laid for further designing a defected ground structure low-pass filter.
The input and output ports of the equivalent circuit are connected with a 50 ohm matching circuit, and the parameters of the equivalent circuit elements are shown in table 2.
TABLE 2 parameter table of equivalent circuit elements of defected ground structure system filter
The ADS simulation results of the present invention are shown in fig. 5 in comparison to ANSOFT HFSS simulation results. The test result shows that the simulation result of the equivalent circuit and the simulation result of ANSOFT HFSS have better consistency to a certain extent.
The test results and ANSOFT HFSS simulation results of the present invention are shown in fig. 6. From the return loss curve S of the filter in the figure11And insertion loss curve S21It can be seen that the pass band width of the filter is 0 GHz-1.4 GHz. The out-of-band rejection frequency width of the defected ground structure filter reaches 2.1 GHz-11 GHz, the out-of-band rejection capability in the stop band range is more than 15dB, and the defected ground structure low-pass filtering is greatly improvedThe filter characteristics of the filter.
The size design and parameters provided by the present invention are only a specific example, and those skilled in the art can make adaptive modifications to the size according to the parameter requirements.
Claims (2)
1. An improved defected ground structure low-pass filter, comprising a dielectric substrate (1), characterized in that: the upper surface of the dielectric substrate (1) is provided with a step impedance unit structure (2), each side of the step impedance unit structure (2) is provided with two steps, each step impedance unit structure (2) is composed of a rectangular structure part (2-2) and a hexagonal structure part (2-1), the size of each step impedance unit structure meets the requirement of impedance ratio, and the step impedance unit structures are connected to a transmission line; wherein the hexagonal structure part (2-1) is composed of a rectangle and a trapezoid when viewed from the plane, the long side of the trapezoid is coincident with the long side of the rectangle, and the rectangular structure part (2-2) is connected with the long side of the rectangular part in the hexagonal structure part (2-1); the medium substrate comprises a medium substrate (1), wherein a metal grounding layer (3) is arranged on the lower surface of the medium substrate (1), a defect ground structure (4) is arranged in the middle area of the metal grounding layer (3), the defect ground structure (4) is composed of a longitudinal rectangular groove and three parallel transverse rectangular grooves, the transverse rectangular grooves and the longitudinal rectangular grooves are mutually staggered, the longitudinal rectangular grooves and the transverse rectangular grooves are directly communicated to the lower surface of the medium substrate (1), and the defect ground structures (4) are distributed in an up-and-down symmetrical mode by taking the horizontal center line of the middle transverse rectangular groove as an axis.
2. The improved defected ground structure low pass filter according to claim 1, characterized in that: the dielectric substrate (1) is made of a Rogers Ro4003 dielectric substrate material, the relative dielectric constant is 3.55, the loss tangent is 0.0027, and the thickness is 0.7-0.9 mm.
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| CN109216838B true CN109216838B (en) | 2020-06-16 |
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| CN110729537A (en) * | 2019-10-30 | 2020-01-24 | 北京中石正旗技术有限公司 | Flexible low pass filter based on Pi type structure |
| CN111613502A (en) * | 2020-05-13 | 2020-09-01 | 南京信息工程大学 | Slow wave structure based on plane surface plasmon polariton |
| CN114883772B (en) * | 2022-07-07 | 2022-09-23 | 香港中文大学（深圳） | Transmission line module for rotary traveling wave oscillator and design method thereof |
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| CN102723542A (en) * | 2012-06-14 | 2012-10-10 | 重庆大学 | Ultra-broad stopband microstrip low-pass filter |
| CN103633399A (en) * | 2013-11-19 | 2014-03-12 | 华南理工大学 | Microstrip ultra wide stop band low pass filter |
| CN105896005A (en) * | 2016-04-28 | 2016-08-24 | 湖北大学 | Small-size low-loss wide-stop-band sharp cut-off microstrip low-pass filter |
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