CN118137091B - Dual-frequency balanced filter based on four-mode rectangular resonant cavity - Google Patents
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Abstract
The invention belongs to the technical field of radio frequency passive circuits, and particularly relates to a double-frequency balanced filter based on a four-mode rectangular resonant cavity, which comprises a rectangular resonant cavity, four pairs of dielectric posts arranged on the inner wall of the rectangular resonant cavity, and an input end PCB feed structure and an output end PCB feed structure which are symmetrically connected to the two side walls of the rectangular resonant cavity; the input end PCB feed structure comprises two parallel input end microstrip lines and two input end coaxial probes; the output end PCB feed structure comprises two parallel output end microstrip lines and two output end coaxial probes, and two input end coaxial probes or output end coaxial probes on the same side are arranged into differential pairs. The invention adopts a PCB feed network and a tuning medium column mode, can realize differential mode excitation and common mode suppression of four modes in a rectangular resonant cavity, completes the design of a balanced filter with double pass bands based on one rectangular resonant cavity, has common mode suppression higher than 50 dB, and has the advantages of miniaturization, high common mode suppression and the like.
Description
Technical Field
The invention belongs to the technical field of radio frequency passive circuits, and particularly relates to a double-frequency balanced filter based on a four-mode rectangular resonant cavity.
Background
Under the continuous change of communication technology, wireless communication is rapidly developed towards high frequency, high integration and high performance, the high integration design of a radio frequency circuit is becoming a trend, however, the further reduction of the circuit volume also aggravates the problems of signal interference, noise and the like, and the balanced filter has the effect of suppressing common mode interference and out-of-band noise.
At present, the design of the balance filter is mainly based on microstrip lines, low-temperature co-fired ceramics, dielectric integrated waveguides and other technologies, but the planar circuit has the defects of low quality factor and power capacity, so that the passband loss of the filter circuit is high. Rectangular cavities have high quality factors and are widely used for designing passive circuits such as high-performance filters, diplexers, magic ts and the like, and low-loss, multi-band and high-selectivity cavity circuits are widely used in the communication fields such as satellites, radars and the like. However, the design of the filter based on the cavity resonator generally adopts a waveguide feed structure, an external flange is required, and the design of the balanced filter requires four feed ports in a circuit, so that the volume is large and the structure is complex. In addition, the cavity resonator has a plurality of modes, and the balanced filter needs to realize multi-mode coupling regulation, namely differential mode excitation and common mode suppression, so that the design of the balanced filter based on the cavity resonator faces difficulties in aspects of size, structure, multi-mode regulation and the like.
In summary, the conventional balanced filter is practically limited in various aspects.
Disclosure of Invention
The invention aims to provide a double-frequency balanced filter based on a four-mode rectangular resonant cavity so as to solve the problems in the background technology.
The invention realizes the above purpose through the following technical scheme:
a dual-frequency balanced filter based on a four-mode rectangular resonant cavity comprises a rectangular resonant cavity, four pairs of dielectric columns arranged on the inner wall of the rectangular resonant cavity, and an input end PCB feed structure and an output end PCB feed structure which are symmetrically connected to the two side walls of the rectangular resonant cavity; wherein,
The input end PCB feed structure comprises two parallel input end microstrip lines and two input end coaxial probes; the output end PCB feed structure comprises two parallel output end microstrip lines and two output end coaxial probes, and two input end coaxial probes or output end coaxial probes on the same side are arranged to be differential pairs.
The dielectric constant of the dielectric column is 36.5, the dielectric constants of the input end microstrip line and the output end microstrip line are 2.2, and the rectangular resonant cavity is made of silver-plated aluminum oxide.
The further improvement is that the metal grounds of the input end PCB feed structure and the output end feed structure are used as metal walls of the rectangular resonant cavity and are positioned at the outermost side of the rectangular resonant cavity.
The input end microstrip line and the output end microstrip line are coupled with the inner cavity of the rectangular resonant cavity, projections of the input end microstrip line and the output end microstrip line on any parallel surface of the input end microstrip line and the output end microstrip line are intersected with each other, and characteristic impedance of the input end microstrip line and the output end microstrip line is 50Ω.
The further improvement is that the two input end coaxial probes are perpendicular to the two input end microstrip lines, and the two output end coaxial probes are perpendicular to the two output end microstrip lines; the coaxial probes in the input end PCB feed structure and the output end PCB feed structure are connected with the microstrip line for differential feed so as to excite the fundamental mode TE 011、TE101 and the higher-order mode TE 012、TE102, and synchronous common mode suppression of four modes is realized during common mode excitation.
The four pairs of dielectric columns are different in size and symmetrically distributed on the inner wall of the rectangular resonant cavity, and the length and the position of the dielectric columns are adjustable and are used for regulating and controlling the frequency and the coupling of the double-passband.
The invention has the beneficial effects that:
The microstrip line is adopted as the feed network of the cavity resonator, the feed structure is embedded in the resonator, the volume is small, the integration is easy, the microstrip line structure is changeable, the design is flexible, and the design flexibility of the cavity resonator is improved.
According to the invention, the four modes of the fundamental mode TE 011、TE101 and the higher-order mode TE 012、TE102 are excited in a differential mode by directly connecting the microstrip line with the resonant cavity, and are distributed in two pass bands, a double-frequency pass band is formed by using only a single cavity resonator, the pass band loss is lower than 0.23 and dB, and the low-loss and miniaturized design is realized.
The invention can realize synchronous common mode rejection of four modes when excited by common mode, and realize common mode rejection effect higher than 50 dB when a single resonator is used.
The invention introduces a dielectric column tuning structure, and can regulate and control the frequency and the coupling of the double-pass band by regulating the position and the size of the dielectric column, thereby increasing the design flexibility and the regulation and control independence of the double-frequency pass band.
Drawings
Fig. 1 is a schematic structural diagram of a dual-frequency balanced filter based on a four-mode rectangular resonant cavity according to the present invention.
Fig. 2 is a front view of a dual-frequency balanced filter based on a four-mode rectangular resonant cavity according to the present invention.
Fig. 3 is a schematic diagram of an inner side surface structure of an input end PCB board in the present invention.
Fig. 4 is a schematic diagram of the inner side surface structure of the output end PCB board in the present invention.
FIG. 5 is a schematic representation of the position of two pairs of mutually perpendicular media pillars in the present invention.
Fig. 6 is a plot of the S-parameter response under differential and common mode signal excitation in the present invention.
In fig. 1:1. a rectangular resonant cavity; 2. an input end PCB feed structure; 3. an output end PCB feed structure; 4. a dielectric column; 21. an input microstrip line; 22. an input end coaxial probe; 31. an output microstrip line; 32. the output end is coaxial with the probe.
Detailed Description
The present application will be described in further detail with reference to the accompanying drawings, wherein it is to be understood that the following detailed description is for the purpose of further illustrating the application only and is not to be construed as limiting the scope of the application, as various insubstantial modifications and adaptations of the application to those skilled in the art can be made in light of the foregoing disclosure.
Example 1
As shown in fig. 1-6, the present embodiment proposes a dual-frequency balanced filter based on a four-mode rectangular resonant cavity, which includes a rectangular resonant cavity 1, four pairs of dielectric pillars 4 disposed on the inner wall of the rectangular resonant cavity 1, and an input end PCB feed structure 2 and an output end PCB feed structure 3 symmetrically connected to two sidewalls of the rectangular resonant cavity 1.
In fig. 1, the input PCB feed structure 2 and the output PCB feed structure 3 are symmetrically disposed on two sidewalls of the rectangular resonant cavity 1 in the horizontal direction, and the present invention is not limited to the direction in which the two feed structures are disposed.
The input-end PCB feed structure 2 comprises two parallel input-end microstrip lines 21 and two input-end coaxial probes 22; the output PCB feed structure 3 comprises two parallel output microstrip lines 31 and two output coaxial probes 32, and two input coaxial probes 22 or output coaxial probes 32 on the same side are arranged as differential pairs.
Correspondingly, the microstrip line and the coaxial probe inside the rectangular resonant cavity 1 are directly connected for feeding, the input microstrip line 21 and the input coaxial probe 22 form an input PCB feeding network, and the output microstrip line 31 and the output coaxial probe 32 form an output PCB feeding network.
As a further preferable scheme, the dielectric constant of the dielectric pillar 4 is 36.5, the dielectric constants of the input microstrip line 21 and the output microstrip line 31 are 2.2, and the rectangular resonant cavity 1 is made of silver-plated alumina.
As a further preferred solution, the metallic grounds of the input PCB feed structure 2 and the output feed structure 3 serve as metallic walls of the rectangular resonator 1, being located at the outermost side of the rectangular resonator 1.
More specifically, the metal ground of the input-end PCB feed structure 2 is also used as a metal wall of the rectangular resonant cavity 1, and is located at the outermost layer of the whole structure, and the input-end microstrip line 21 is disposed inside the rectangular resonant cavity 1 and directly coupled with the rectangular resonant cavity. The metal ground of the output end PCB feed structure 3 is also used as the metal wall of the rectangular resonant cavity 1 and is positioned at the outermost layer of the whole structure, and the output end microstrip line 31 is arranged inside the rectangular resonant cavity 1 and is directly coupled with the rectangular resonant cavity.
As a further preferable scheme, the input end microstrip line 21 and the output end microstrip line 31 are coupled with the inner cavity of the rectangular resonant cavity 1, and the characteristic impedance of the input end microstrip line 21 and the output end microstrip line 31 is 50Ω.
In this embodiment, the input microstrip line 21 and the output microstrip line 31 are coupled with the cavity of the rectangular resonant cavity 1, and the projections of the input microstrip line 21 and the output microstrip line 31 on any parallel plane thereof are intersected with each other, and the characteristic impedance of the input microstrip line 21 and the output microstrip line 31 is 50Ω. As shown in fig. 3, the input microstrip line 21 rotates reversely in the horizontal directionAs shown in fig. 4, the output microstrip line 31 rotates forward in the horizontal directionDegree.
As a further preferable scheme, the two input end coaxial probes 22 are perpendicular to the two input end microstrip lines 21, and the two output end coaxial probes 32 are perpendicular to the two output end microstrip lines 31; the coaxial probes in the input end PCB feed structure 2 and the output end PCB feed structure 3 are connected with the microstrip line for differential feed so as to excite the fundamental mode TE 011、TE101 and the higher-order mode TE 012、TE102, and synchronous common mode suppression of four modes is realized during common mode excitation.
As a further preferable scheme, four pairs of dielectric columns 4 are symmetrically distributed on the inner wall of the rectangular resonant cavity 1, more specifically, the dielectric columns 4 are centrosymmetric in the rectangular resonant cavity 1, two pairs of dielectric columns 4 which are mutually perpendicular on the same side are different in size, and the length and the position of the dielectric columns 4 are adjustable and are used for regulating and controlling the frequency and the coupling of the double-passband.
In this embodiment, as shown in fig. 1-5, four pairs of dielectric pillars 4 are disposed in the rectangular resonant cavity 1, two pairs of dielectric pillars 4 are respectively inserted at two sides symmetrical along the center of the resonant cavity, the two pairs of dielectric pillars 4 are perpendicular to each other but have different dimensions, and the dielectric constant of the dielectric pillars 4 is 36.5. In a specific implementation process, the invention introduces a dielectric column tuning structure, and can regulate and control the frequency and the coupling of the double-pass band by regulating the position and the size of the dielectric column, thereby increasing the design flexibility and the regulation and control independence of the double-frequency pass band.
Further simulation tests were performed in connection with the filters in the above embodiments.
According to an embodiment of the present invention, as shown in fig. 2-5, a dual-frequency balanced filter in this example is subjected to simulation test, where the parameters are as follows:
The length L1 of the rectangular resonant cavity 1 is 17.5mm, the width W1 is 17.5mm, and the height H1 is 40mm; the lengths L2 of the input microstrip line 21 and the output microstrip line 31 are 10.1mm, the widths W2 are 1.2mm, and the angles with the horizontal direction are formed 40 Degrees; the diameter D2 of the dielectric column 4 embedded in the inner wall of the rectangular resonant cavity 1 is 2.5mm, the length H2 of the dielectric column 4 in the horizontal direction is 2.1mm, and the length H3 of the dielectric column 4 in the vertical direction is 2.5mm; the dielectric substrates of the input microstrip line 21 and the output microstrip line 31 are made of Rogowski 5880 plates, the dielectric constant is 2.2, the thickness is 0.787mm, and the dielectric loss tangent is 0.0009; the wall thickness D1 of the rectangular resonant cavity 1 is 4mm, and the rectangular resonant cavity 1 is made of silver-plated aluminum.
The test results are shown in FIG. 6, FIG. 6 comprisingThree response curves, the dual-frequency balanced filter excites four modes in a single rectangular cavity in a differential mode to form two pass bands, wherein the first pass band mode is a fundamental mode TE 011、TE101, and the second pass band mode is a higher order mode TE 012、TE102. The first passband has a center frequency of 9.1 GHz, an insertion loss of 0.23 dB, a return loss of less than 21 dB, and the second passband has a center frequency of 10.7 GHz, an insertion loss of 0.17 dB, and a return loss of less than 20 dB. The common mode rejection in the first passband is higher than 70 dB and the common mode rejection in the second passband is higher than 53 dB. The lower side frequencies of the two pass bands are provided with a transmission zero point, so that the filter has good selectivity.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the application has been described in detail with reference to the foregoing embodiments, it will be appreciated by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not drive the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (5)
1. The double-frequency balanced filter based on the four-mode rectangular resonant cavity is characterized by comprising a rectangular resonant cavity (1), four pairs of dielectric columns (4) arranged on the inner wall of the rectangular resonant cavity (1), and an input end PCB feed structure (2) and an output end PCB feed structure (3) which are symmetrically connected to the two side walls of the rectangular resonant cavity (1); wherein,
The four pairs of dielectric columns (4) are respectively arranged on the four inner walls of the rectangular resonant cavity (1), and the dielectric columns (4) are centrally symmetrical in the rectangular resonant cavity (1);
The input end PCB feed structure (2) comprises two parallel input end microstrip lines (21) and two input end coaxial probes (22); the output end PCB feed structure (3) comprises two parallel output end microstrip lines (31) and two output end coaxial probes (32), and two input end coaxial probes (22) or output end coaxial probes (32) on the same side are arranged as differential pairs;
The metal grounds of the input end PCB feed structure (2) and the output end PCB feed structure (3) are used as metal walls of the rectangular resonant cavity (1) and are positioned at the outermost side of the rectangular resonant cavity (1);
The input end microstrip line (21) and the output end microstrip line (31) are coupled with the inner cavity of the rectangular resonant cavity (1), and projections of the input end microstrip line (21) and the output end microstrip line (31) on any parallel surfaces thereof are mutually intersected.
2. A four-mode rectangular resonator based dual-frequency balanced filter according to claim 1, wherein: the dielectric constant of the dielectric column (4) is 36.5, the dielectric constants of the input end microstrip line (21) and the output end microstrip line (31) are 2.2, and the rectangular resonant cavity (1) is made of silver-plated aluminum oxide.
3. A four-mode rectangular resonator based dual-frequency balanced filter according to claim 1, wherein: the characteristic impedance of the input microstrip line (21) and the output microstrip line (31) is 50Ω.
4. A four-mode rectangular resonator based dual-frequency balanced filter according to claim 1, wherein: the two input end coaxial probes (22) are perpendicular to the two input end microstrip lines (21), and the two output end coaxial probes (32) are perpendicular to the two output end microstrip lines (31); the coaxial probes in the input end PCB feed structure (2) and the output end PCB feed structure (3) are connected with the microstrip line for differential feed so as to excite the fundamental mode TE 011、TE101 and the higher order mode TE 012、TE102, and synchronous common mode suppression of four modes is realized during common mode excitation.
5. A four-mode rectangular resonator based dual-frequency balanced filter according to claim 1, wherein: four pairs of medium columns (4) are different in size and symmetrically distributed on the inner wall of the rectangular resonant cavity (1), and the length and the position of the medium columns (4) are adjustable and used for regulating and controlling the frequency and the coupling of the double-passband.
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CN106910970A (en) * | 2017-03-03 | 2017-06-30 | 华南理工大学 | A kind of mode filter of cavity four |
CN109411855A (en) * | 2018-06-27 | 2019-03-01 | 华南理工大学 | A kind of double frequency filtering balun based on cavity |
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CN117458104B (en) * | 2023-11-03 | 2024-07-09 | 安徽大学 | Frequency bandwidth adjustable filter based on single cavity resonator |
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CN106910970A (en) * | 2017-03-03 | 2017-06-30 | 华南理工大学 | A kind of mode filter of cavity four |
CN109411855A (en) * | 2018-06-27 | 2019-03-01 | 华南理工大学 | A kind of double frequency filtering balun based on cavity |
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