Disclosure of Invention
The invention aims to provide a dual-passband filter based on a quarter-wave resonator, which is used for solving the contradiction between the small size of the traditional dual-passband filter design and the independent adjustment of single passband parameter. The dual-band filter has the advantages that the quarter-wavelength resonator microstrip lines are folded and share the grounding through holes, so that the overall size is smaller on the basis of ensuring that parameters such as the bandwidth, the quality factor and the like of a single passband of the dual-band filter can be independently adjusted.
In order to realize the purpose, the invention adopts the following technical scheme:
a dual-band filter based on quarter-wave resonators, the dual-band filter being centrosymmetric with a ground via 103 as a center, comprising: the broadband antenna comprises an input port 1, an output port 2, two first passband resonators 111 and 112 and two second passband resonators 121 and 122, wherein the four resonators are all quarter-wavelength stepped impedance resonators; the high-order ladder impedance arms of the four resonators are vertically connected with each other, and the connection parts share the grounding through hole 103; the low-order ladder impedance arms of the four resonators are folded in the same direction by 90 degrees, wherein the low-order ladder impedance arm of the second passband resonator is vertically connected with the high-order ladder impedance arm of the second passband resonator, and the low-order ladder impedance arm of the first passband resonator is folded into a U shape and is vertically connected with the high-order ladder impedance arm of the first passband resonator;
the input port and the output port have the same structure and are formed by two L-shaped arms vertically connected by a long arm; a first coupling gap 101 is formed between one side of a long arm of the first L-shaped arm and the outer side of a low-order ladder impedance arm of the first passband resonator, and the other side of the first L-shaped arm is vertically connected with a short arm of the first passband resonator; a second coupling slot 102 is formed between one side of the long arm of the second L-shaped arm and the inner side of the low-order ladder impedance arm of the second passband resonator, and the other side is vertically connected with the short arm thereof.
The invention has the beneficial effects that:
the invention provides a dual-passband filter based on a quarter-wave resonator, which has the advantages that the overall size is smaller by means of folding the microstrip line of the quarter-wave resonator and sharing a grounding through hole on the basis of ensuring that parameters such as bandwidth, quality factor and the like of a single passband of the dual-passband filter can be independently adjusted; meanwhile, the invention can reduce the design complexity of the dual-passband filter and improve the design efficiency by adjusting the coupling gaps between the input and output ports and the resonators and the size of the grounding through hole positioned at the central position, adjusting the parameters such as the bandwidth, the quality factor, the coupling coefficient between the resonators and the like of the single passband of the dual-passband filter and adopting the centrosymmetric overall structure design.
Drawings
FIG. 1 is a schematic structural diagram of a dual-band filter based on quarter-wave resonators according to the present invention;
FIG. 2 is a schematic diagram of a quarter-wave resonator before folding in the dual-band-pass filter according to the present invention;
FIG. 3 is a diagram of the physical dimensions of a dual bandpass filter based on quarter-wave resonators in an embodiment of the invention;
FIG. 4 is a graph comparing simulation and test results of a dual-bandpass filter based on quarter-wave resonators according to an embodiment of the present invention;
wherein, 1, input port; 2. an output port; 101. a first coupling slot between the input-output port and the first pass-band resonator; 102. a second coupling gap between the input/output port and the second pass-band resonator; 103. a ground via; 111. a first band-on-band unit resonator; 112. a first through band two-unit resonator; 121. a second band-on-band unit resonator; 122. the second band-pass two-element resonator.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without any creative effort shall fall within the protection scope of the present invention.
This embodiment provides a dual-bandpass filter based on a quarter-wave resonator, whose structure is shown in fig. 1, where the dual-bandpass filter takes a ground via 103 as a center and is centrosymmetric, and includes: the broadband antenna comprises an input port 1, an output port 2, two first passband resonators 111 and 112 and two second passband resonators 121 and 122, wherein the four resonators are all quarter-wavelength stepped impedance resonators and are formed by connecting high-order stepped impedance arms and low-order stepped impedance arms; the high-order ladder impedance arms of the four resonators are mutually vertically connected, and the connection parts share the grounding through hole 103; the low-order ladder impedance arms of the four resonators are folded in the same direction by 90 degrees, wherein the low-order ladder impedance arm of the second passband resonator is vertically connected with the high-order ladder impedance arm of the second passband resonator, and the low-order ladder impedance arm of the first passband resonator is folded into a U shape and is vertically connected with the high-order ladder impedance arm of the first passband resonator;
the input port and the output port have the same structure and are both formed by a first L-shaped arm and a second L-shaped arm, and the first L-shaped arm is vertically connected with the long arm of the second L-shaped arm; a first coupling gap 101 is formed between one side of the long arm of the first L-shaped arm and the outer side of the U-shaped low-order ladder impedance arm of the first passband resonator, and the other side of the long arm of the first L-shaped arm is vertically connected with the short arm of the first L-shaped arm; a second coupling gap 102 is formed between one side of the long arm of the second L-shaped arm and the inner side of the low-order ladder impedance arm of the second passband resonator, and the other side of the long arm of the second L-shaped arm is vertically connected with the short arm of the second L-shaped arm.
Furthermore, in the input port and the output port, the short arm of the first L-shaped arm is correspondingly used as an input port and an output port, and the microstrip line impedances of the input port and the output port are fixed to be 50 ohms.
In terms of working principle, in the dual-passband filter, four resonators all adopt quarter-wavelength stepped impedance resonators, the first passband resonator 111 and the first passband resonator 112 form a first passband, the second passband resonator 121 and the second passband resonator 122 form a second passband, the high-order stepped impedance arms of the resonators of the first passband and the second passband are perpendicular to each other, and share the ground via 103, as shown in fig. 2; the ground vias may be used to adjust the coupling coefficient between the resonators and the bandwidth of the first and second pass-bands. In the invention, the design of microstrip line folding is adopted, and the low-order ladder impedance arms of the four resonators are folded by 90 degrees in the same direction, as shown in figure 1, on the basis of ensuring that parameters such as bandwidth, quality factor and the like of a single passband in the dual-passband filter can be independently adjusted, the whole size is greatly reduced; moreover, the central frequencies of the first passband and the second passband can be adjusted by adjusting the size of the microstrip line of the resonator. Meanwhile, in the invention, the input port (output port) adopts the design that the long arms of two L-shaped arms are vertically connected, so that the input port is coupled in parallel with the outer side of the left arm of the U-shaped low-order ladder impedance arm of the first passband resonator through the first coupling gap 101 and coupled in parallel with the inner side of the low-order ladder impedance arm of the second passband resonator through the second coupling gap 102; the quality factor of the first passband of the dual-passband filter can be adjusted by adjusting the width of the first coupling gap 101, and the quality factor of the second passband of the dual-passband filter can be adjusted by adjusting the width of the second coupling gap 102.
In conclusion, the dual-passband filter disclosed by the invention can ensure that the overall size is greatly reduced on the basis of independently adjusting parameters such as bandwidth, quality factor and the like of a single passband in the dual-passband filter; meanwhile, the overall structural design of central symmetry reduces the design complexity of the dual-passband filter and improves the design efficiency.
More specifically: in this embodiment, a dual-band filter based on a quarter-wave resonator according to the present invention is designed on a substrate Rogers 4350B, and as shown in fig. 3, the specific dimensions are as follows (unit: mm): l1=1.75,l2=4,l3=1.5,l4=2.2,l5=1.75,l6=3.15,l7=1,l8=2.75,l9=6.2,w1=0.5,w2=1,w3=0.5,w4=1,w5=0.5,s1=0.1,s2=0.1,r1=0.31。
The results of simulation tests on the dual-passband filter are shown in fig. 4, the center frequency of the dual-passband filter is 4.4GHz and 7.4GHz, the 3dB relative bandwidth is 10.2% and 6.4%, respectively, and two transmission zeros, TZ1 and TZ2, are arranged at 5.2GHz and 6.1 GHz; the electrical size of the dual-band filter based on the quarter-wave resonators in this embodiment is only 6X 7.5mm (0.41 lambda)g×0.18λg、λgA waveguide wavelength of a 50 ohm microstrip line at a center frequency of the first pass band).
While the invention has been described with reference to specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.