CN115588831A - Band-pass filter with tunable stop band and hollowed-out bow-tie cell plasma excimer - Google Patents
Band-pass filter with tunable stop band and hollowed-out bow-tie cell plasma excimer Download PDFInfo
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Abstract
The invention provides a band-pass filter with tunable stop band and hollow bow-tie cells for plasmon polariton, which is sequentially provided with a metal grounding layer, a dielectric plate layer and a metal circuit top layer from bottom to top. The metal circuit top layer comprises a first coplanar waveguide transmission line, a first wave conversion transition region, a hollow bow-tie cell group, a second wave conversion transition region and a second coplanar waveguide transmission line which are sequentially connected along an axis. The top layer of the metal circuit is rectangular, and arc-shaped metal conductors are respectively arranged at four vertex angles of the top layer. The first wave conversion transition region and the second wave conversion transition region are both composed of a plurality of gradient-cut solid cells connected in series. The hollow bow-tie cell group consists of a plurality of hollow bow-tie cells, and each hollow bow-tie cell is obtained by excavating a bow-tie-shaped through hole from a solid cell. And the upper end and the lower end of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are cut off and connected by adding capacitors. The filter realizes dynamic adjustment of low-frequency cut-off frequency, pass-band internal resistance band suppression level, bandwidth and frequency.
Description
Technical Field
The invention relates to the technical field of microwave transmission, in particular to a band-pass filter with tunable stop band and hollow bow-tie cell plasmons.
Background
In recent years, surface Plasmon Polaritons (SPPs) have been attracting attention in various technical fields such as microwaves and photonics.
Surface plasmon is an electromagnetic wave mode caused by interaction of photons and free electrons on the surface of a metal, or excited by coupling of photons and free electrons at the interface of two materials with opposite signs, which may be, for example, a metal and an insulating medium. Surface plasmons have both photonic speed and electronic dimensions, and thus have received extensive attention and research.
In the optical wave band, surface plasmon can propagate along a metal-medium contact surface, an electric field is tightly bound near the contact surface, and a propagation constant exponentially increases with the increase of frequency. However, in the lower Terahertz (Terahertz, THz) and microwave frequency bands, because metal shows ideal conductor characteristics, the necessary condition that the dielectric constants of two materials are opposite in sign cannot be met, so that the application of surface plasmon is limited. Therefore, an artificial Surface Plasmon Polaritons (SSPPs) transmission structure with a periodic structure is produced, which breaks the limit of the application frequency band of the Surface Plasmon Polaritons, supports the excitation and transmission in the terahertz and microwave frequency bands, and still has the advantages of low crosstalk, extremely high field binding property and high-frequency harmonic signal interference suppression.
Although various microwave devices based on the artificial surface plasmon transmission structure are designed and proposed up to now, most circuits do not have dynamic regulation performance, and cannot be used for regulating complex circuit systems, which is also a main obstacle that the artificial surface plasmon microwave devices cannot be widely applied to reconfigurable integrated microwave systems and electrically controlled antenna feed networks.
Disclosure of Invention
In view of the above, the present invention provides a band-pass filter for band-pass tunable band-pass of a bowtie cell plasmon, the method can eliminate or improve one or more defects in the prior art, and solve the problem that the prior art cannot dynamically adjust the low-frequency cut-off frequency, the bandwidth of a stopband in a passband, and the frequency.
The invention provides a band-pass filter with tunable stop band and hollowed-out bow-tie cell plasma excimer, which comprises:
a metal ground layer;
a dielectric slab layer disposed above the metal ground layer;
the metal circuit top layer is arranged above the dielectric slab layer and comprises a first coplanar waveguide transmission line, a first wave conversion transition region, a hollow bow-tie cell group, a second wave conversion transition region and a second coplanar waveguide transmission line which are sequentially connected along an axis; the metal circuit top layer is rectangular, four top corners of the metal circuit top layer are respectively provided with arc-shaped metal conductors, and the arc-shaped metal conductors are connected with the metal grounding layer through metal through holes; the first wave conversion transition area and the second wave conversion transition area are both formed by connecting a plurality of gradient-cut solid cells in series; the hollow bow-tie cell group consists of a plurality of hollow bow-tie cell elements, and each hollow bow-tie cell element is obtained by excavating a bow-tie-shaped through hole from the solid cell element; and the upper end and the lower end of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are cut off and connected by adding a capacitor.
In some embodiments of the present invention, the upper and lower ends of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are cut off, and a variable capacitor is added at one end and a fixed capacitor is added at the other end.
In some embodiments of the present invention, the upper and lower ends of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are truncated, and variable capacitors are respectively added to the upper and lower ends; in a single hollow bow-tie cell, the capacitance values of variable capacitors at two ends are equal.
In some embodiments of the invention, the height of each solid cell in the first wave conversion transition region gradually increases along the first coplanar waveguide transmission line toward the hollow bow-tie cell group;
and the height of each solid cell in the second wave conversion transition region is gradually reduced along the direction from the hollow bow-tie cell group to the second coplanar waveguide transmission line.
In some embodiments of the present invention, the hollow bow tie cell group is formed by connecting 7 hollow bow tie cells in series, wherein the upper and lower ends of the middle 3 hollow bow tie cells are cut off and connected by adding a capacitor; the first and second wave-converting transition regions each comprise 5 solid cells connected in series.
In some embodiments of the invention, further comprising: the method comprises the steps that a direct current bias circuit is arranged to provide power for a hollow bow-tie cell added with a variable capacitor, and a plurality of alternating current isolation inductors are arranged in the direct current bias circuit.
In some embodiments of the present invention, a first dc blocking capacitor is disposed between the first coplanar waveguide transmission line and the first wave conversion transition region; and a second direct current blocking capacitor is arranged between the second wave conversion transition region and the second coplanar waveguide transmission line.
In some embodiments of the invention, the arc-shaped metal conductor is a quarter ellipse.
In some embodiments of the present invention, the dielectric layer has a dielectric constant of 3.66 and a loss constant of 0.0037.
In some embodiments of the invention, the solid cell periodically repeats within the circuit with a unit length of 6 millimeters.
The invention has the beneficial effects that at least:
the invention provides a band-pass filter with tunable stop bands for a plasma excimer of a hollow bow-tie cell, wherein a first coplanar waveguide transmission line, a first wave conversion transition area, a hollow bow-tie cell group, a second wave conversion transition area and a second coplanar waveguide transmission line are sequentially arranged on the top layer of a metal circuit along an axis, and arc-shaped metal conductors are respectively arranged at four top angles of the top layer of the metal circuit. The filter provided by the invention has a simple structure and is easy to realize.
Furthermore, the upper end and the lower end of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are cut off and connected by adding capacitors. Under the condition that a variable capacitor is added at one end of the hollow bow-tie cell element, and a fixed capacitor is added at the other end of the hollow bow-tie cell element, the filter has the advantages of low crosstalk, high field binding and deep high-frequency harmonic suppression, and can realize dynamic adjustment of low-frequency cut-off frequency, pass-band internal resistance band suppression level, bandwidth and frequency. Under the condition that the upper end and the lower end of the hollow bow-tie cell element are respectively added with the variable capacitors, the filter has the advantages of low crosstalk, high field constraint and deep high-frequency harmonic suppression, and can realize dynamic adjustment of low-frequency cut-off frequency, passband bandwidth and frequency. The invention lays a foundation for the wide application of the artificial surface plasmon microwave device in a reconfigurable integrated microwave system and an electric control antenna feed network.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
fig. 1 is an ideal simulation structure diagram of a band-pass filter with tunable stop bands for a plasma excimer of a hollow bow-tie cell according to an embodiment of the present invention.
Fig. 2 is a three-dimensional structure diagram of a solid cell and a hollow bow-tie cell and a near field radiation diagram of the solid cell and the hollow bow-tie cell according to an embodiment of the invention.
Fig. 3 is a dispersion curve graph of solid cells and hollow bow-tie cells as a function of predetermined parameters according to an embodiment of the present invention.
Fig. 4 is a three-dimensional structure diagram of a hollow bow-tie cell with a capacitor added thereto according to an embodiment of the invention.
Fig. 5 is a dispersion curve diagram of the hollow bow-tie cell after the capacitor is added according to the embodiment of the invention in the basic mode and the second-order mode along with the change of the capacitor value.
Fig. 6 is an ideal simulation S parameter comparison graph and a near-field radiation distribution graph of the band-pass filter with tunable stop bands.
Fig. 7 is a diagram illustrating an exemplary structure of a band-pass filter with tunable stop bands for a plasma excimer of a hollow bowtie cell according to an embodiment of the present invention.
Fig. 8 is a comparison graph of measured S parameters of the band-pass filter with tunable stop bands.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.
It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.
It is also noted herein that the term "coupled," if not specifically stated, may refer herein to not only a direct connection, but also an indirect connection in which an intermediate is present.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps.
In order to solve the problem that the prior art cannot dynamically adjust the low-frequency cut-off frequency, the bandwidth of a stopband in a passband, and the frequency, the invention provides a stopband tunable hollow bow-tie cell plasmon polariton bandpass filter, as shown in fig. 1, the ideal simulation structure diagram of the filter of the invention is shown, and the filter comprises:
and a metal grounding layer.
And the dielectric slab layer is arranged above the metal grounding layer.
And the metal circuit top layer is arranged above the dielectric plate layer. The metal circuit top layer comprises a first coplanar waveguide transmission line, a first wave conversion transition region, a hollow bow-tie cell group, a second wave conversion transition region and a second coplanar waveguide transmission line which are sequentially connected along an axis. The metal circuit top layer is rectangular, and four top angles of the metal circuit top layer are respectively provided with an arc-shaped metal conductor, wherein the arc-shaped metal conductors are connected with the metal grounding layer through metal through holes. The first wave conversion transition region and the second wave conversion transition region are both composed of a plurality of gradient-cut solid cells connected in series. The hollow bow-tie cell unit is composed of a plurality of hollow bow-tie cell units, and each hollow bow-tie cell unit is obtained by excavating a bow-tie-shaped through hole from a solid cell unit. And the upper end and the lower end of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are cut off and connected by adding capacitors.
In some embodiments, the dielectric slab layer is a Rogers RO4350B dielectric slab with a thickness of 0.508 mm, wherein the dielectric slab has a dielectric constant ε r It was 3.66, and the loss constant tan δ was 0.0037.
And arranging a large-area metal floor on the lower surface of the dielectric plate to form a metal grounding layer.
In some embodiments, the metal ground layer and the metal circuit top layer are each 0.035 millimeters thick.
In the top layer of the metal circuit, the first coplanar waveguide transmission line and the second coplanar waveguide transmission line are used as filter signal feeders and are respectively used for realizing the input and output of microwave signals in the filter. In some embodiments, the width w of the first coplanar waveguide transmission line and the second coplanar waveguide transmission line are each 1.08 millimeters.
The four top corners of the top layer of the metal circuit are respectively provided with arc-shaped metal conductors, and in some embodiments, each arc-shaped metal conductor is a quarter ellipse. A plurality of metal through holes are formed in each arc-shaped metal conductor, and the metal through holes are connected with the metal grounding layer to be grounded, so that the transmission insertion loss of signals is reduced, and the signal transmission efficiency is improved. And each circular arc-shaped metal conductor, the first coplanar waveguide transmission line and the second coplanar waveguide transmission line form a coplanar waveguide.
In some embodiments, the distance s between the circular arc-shaped metal conductor and the first coplanar waveguide transmission line and the second coplanar waveguide transmission line is 0.81 mm.
Electromagnetic waves are transmitted in a quasi-TEM Wave mode on the first coplanar waveguide transmission line and the second coplanar waveguide transmission line, and Transverse magnetic waves (TM waves) are polarized and excited on the artificial surface plasmon transmission structure, so that a first Wave conversion transition region and a second Wave conversion transition region are arranged between the first coplanar waveguide transmission line and the second coplanar waveguide transmission line and the hollow bow-tie cell group to realize Wave type transition, and the transmission efficiency of signals is improved. Simulation experiments prove that the solid cell elements which are cut in a gradient manner and connected in series in the first wave conversion transition region and the second wave conversion transition region are combined with the four arc-shaped metal conductors, so that the wave mode conversion of the electromagnetic waves from quasi-TEM waves to TM waves can be effectively completed.
In some embodiments, as shown in FIG. 1, the metal conductor side l is a circular arc r 37.5 mm long and another side w r 13.65 mm long, near l r One side of the edge is provided with 11 metal through holes.
In some embodiments, each solid cell in the first wave conversion transition region is cut in a gradient manner according to a preset angle, and the height of each solid cell gradually increases towards the hollow bow tie cell group along the first coplanar waveguide transmission line; and each solid cell in the second wave conversion transition area is also subjected to gradient cutting according to a preset angle, and the height of each solid cell is gradually reduced along the direction from the hollow bow node cell group to the second coplanar waveguide transmission line.
In some embodiments, as shown in fig. 1, the predetermined angle of cutting of each solid cell in the first wave-converting transition region and the second wave-converting transition region is according to w cut ＝3.1mm,l cut =30 mm.
In some embodiments, as shown in fig. 1, the hollow bow tie cell group is composed of 7 hollow bow tie cells connected in series, wherein the upper and lower ends of the middle 3 hollow bow tie cells are cut off and connected by adding a capacitor. The first and second wave-converting transition regions each comprise 5 solid cells connected in series.
As shown in fig. 2 (a), the left diagram is a structural diagram of a solid cell, and the right diagram is a structural diagram of a hollow bow-tie cell.
The cell is a periodic structure with a certain shape manufactured on a medium substrate by etching, laser engraving and other methods. As shown in fig. 2 (a), the unit length of each solid cell periodically repeated in the circuit in the present invention is represented by d. The hollow bow-tie cell is obtained by excavating a bow-tie-shaped through hole in the middle of a solid cell, so that the hollow bow-tie cell and the solid cell have the same outer contour dimension, the specific shape is shown in the right diagram of fig. 2 (a), and the hollow dimension of the hollow bow-tie cell is h 2 、b 2 And c 2 And (4) showing. The near field radiation patterns of the solid cell and the hollow bow-tie cell are shown in fig. 2 (b).
Fig. 3 is a graph showing the dispersion curves of solid cells and hollow bow-tie cells under varying periodicity length and hollow size. In an artificial surface plasmon transmission device realized by a periodic solid cell arrangement, the dispersion curve of a single solid cell falls in a slow wave region, wherein the slow wave region and a fast wave region are divided by the dispersion curve of light. As can be seen, the propagation constant increases exponentially with increasing frequency, so that a single solid cell has its own high frequency cutoff.
As shown in fig. 2 (b), the near field radiation pattern of the solid cell and the hollow bow-tie cell shows, the energy coupling at the center of the solid cell is weak, so after the metal at the center of the solid cell is hollowed out, as shown in fig. 3, the obtained hollow bow-tie cell is still in a slow wave region, and the high frequency cut-off frequency still exists, and at the same time, the high frequency cut-off frequency is hardly changed. The transmission device formed by the periodic arrangement of the solid cells and/or the hollow bow-tie cells has the performance of high-frequency harmonic signal interference suppression, the suppression performance of the transmission device is enhanced along with the increase of the number of the composition cells, and the transmission efficiency in a pass band is reduced along with the increase of the number of the composition cells.
For the periodic length d of the solid cell element and the hollow size h of the hollow bow-tie cell element 2 ,b 2 ,c 2 In a variation, as shown in fig. 3, the high frequency cutoff frequency decreases as the periodic length d of the solid cell and its corresponding hollow bow-tie cell increases. Changing the hollow size h of the hollow bow tie cell element under the condition of equal periodic length d 2 、b 2 And c 2 The high-frequency cut-off frequency of the hollow bow-tie cell element is almost unchanged, that is, the performance of the hollow cell element is not affected by the change of the hollow size. Therefore, the high frequency cut-off frequency of the solid cell and the hollow bow-tie cell with the same outline size are equal.
In some embodiments, in fig. 2 (a), the unit length d =6mm of the solid cell and the corresponding hollow bow-tie cell periodically repeated in the circuit, and other outline dimensions are: w =1.08mm 1 ＝1.8mm,c 1 ＝4.2mm,h 1 =3.6mm, the hollow size of the corresponding hollow bow tie cell is: b 2 ＝0.53mm,c 2 ＝2mm,h 2 ＝2.2mm。
In order to realize the tunability of the low-frequency cut-off frequency, the width of a stop band and the frequency of the filter, the upper end and the lower end of the hollow bow-tie cell are cut off, and a variable capacitor and/or a fixed capacitor are added at the cut-off position for reconnection.
When the hollow bow-tie cell is conducted by adding a capacitor, the dispersion curve is split into two propagation modes: the dispersion curves of the hollow bow-tie cell elements under the mode 1 and the mode 2 are different after the capacitors are added in the basic mode and the second-order mode. The fundamental mode is denoted as modulo 1 and the second order mode is denoted as modulo 2.
In some embodiments, as shown in fig. 4 (a), a variable capacitor C is added at one end of the hollow bow-tie cell 1 The other end is added with a fixed capacitor C 2 . Illustratively, choose C 2 =0.9pF, practical, C 1 The capacitance value of the capacitor can be changed and adjusted within the range of 0.3-1.8 pF, and is matched with C 2 The capacitance values of the capacitors are different.
The hollow bow tie cell is added with a variable at one endCapacitor C 1 The other end is added with a fixed capacitor C 2 The dispersion curves for the two modes of propagation are shown in fig. 5 (a), and the following conclusions can be drawn:
1. the low-frequency part of the dispersion curve of the hollow bow-tie cell element added with the capacitor is superposed with the light dispersion curve under two propagation modes, and the hollow bow-tie cell element deviates from the light dispersion curve after reaching the respective turning point along with the increase of the frequency and falls into a slow wave region and is gradually close to the high-frequency cut-off frequency of the hollow bow-tie cell element under the two propagation modes. But with variable capacitance C 1 The capacitance value is increased, the high-frequency cut-off frequency of the hollow bow-tie cell with the capacitor added is reduced under the mode 1, and the high-frequency cut-off frequency under the mode 2 is kept unchanged at 5.81 GHz.
2. When the dispersion curve of the hollow bow-tie cell element added with the capacitor is superposed with the dispersion curve of light, it is indicated that at this time, the electromagnetic wave is totally radiated into the external light, and the hollow bow-tie cell element does not support the transmission of signals on the surface thereof, so that in two transmission modes, the hollow bow-tie cell element added with the capacitor has a low-frequency cut-off frequency, and the frequency at each turning point corresponds to the respective low-frequency cut-off frequency.
3. When C is present 2 =0.9pF and C 1 When the capacity value of (C) is adjusted within the range of 0.3-1.8 pF, no matter C 1 How to adjust, the low-frequency cut-off frequency in the die 2 is always larger than the high-frequency cut-off frequency in the die 1, and a stop band in the pass band of the hollow bow-tie cell is formed. With variable capacitance C 1 The frequency of the formed stop band is increased; when C is present 1 The closer the capacitance value of (A) is to C 2 =0.9pF, the narrower the bandwidth of the stop band; in particular, when C 1 ＝C 2 =0.9pF, no stop band is present. Thereby achieving tunability of the stop band.
4. With variable capacitance C 1 The turning points under the die 1 slightly move downwards, namely the low-frequency cut-off frequency of the hollow bow-tie cell element added with the capacitor is slightly reduced, so that the low-frequency cut-off frequency can be tuned.
In the structure diagram of the ideal simulation of the filter shown in fig. 1, a tunable hollow bow-tie cell is adopted with a variable capacitor C added at one end 1 The other end is added with a fixed electrodeContainer C 2 In the case of the method (3), the filter is simulated, and an ideal simulation result of the S parameter of the filter is shown in fig. 6 (a), wherein the S parameter includes the return loss | S 11 I and insertion loss I S 21 L. the method is used for the preparation of the medicament. Return loss, also known as reflection loss, is the reflection of the link due to impedance mismatch. Return loss is a parameter that represents the reflection performance of a signal, indicating that a portion of the incident power is reflected back to the signal source, typically specified at the input and output. Insertion loss refers to the loss of load power that occurs somewhere in the transmission system due to the insertion of an element or device, and is expressed as the ratio in decibels of the power received at the load before the element or device is inserted to the power received at the same load after insertion.
Specifically, as can be seen from FIG. 6 (a), when a tunable hollow bowtie cell is added to a filter, a variable capacitor C is added at one end 1 ，C 1 Adjusting the voltage in the range of 0.3-1.8 pF, adding a fixed capacitor C at the other end 2 In the case of =0.9pF, a transmission stop band is generated in the pass band of the filter, and the frequency of the stop band is dependent on C 1 Is increased when the variable capacitance C is decreased 1 The closer the capacitance value of (C) is to the fixed capacitance C 2 The smaller the stopband bandwidth, the lower the suppression level. Exemplary, at C 1 When =0.7pF, the stop band is narrowest, only 0.08GHz, and the insertion loss | S 21 The | suppression level is about 20dB; at C 1 When =0.3pF, the stop band is widest and reaches 0.47GHz, and the insertion loss | S 21 The level of suppression exceeds 40dB. At the same time, with variable capacitance C 1 The low-frequency cut-off frequency of the filter is gradually reduced from 2.56GHz to 1.62GHz, and the high-frequency cut-off frequency of the filter is kept about 5.76GHz without being accompanied by C 1 Is varied.
As shown in FIG. 6 (C), the variable capacitor C corresponds to FIG. 6 (a) 1 The capacitance C is adjusted and fixed within the range of 0.3-1.8 pF 2 =0.9pF, and C 1 ≠C 2 With variable capacitance C 1 Adjusting the frequency within the range of 0.3-1.8 pF to obtain the frequency points of the filter at 1.0GHz, 2.95GHz, 3.1GHz, 3.5GHz, 3.8GHz, 4.3GHz and 8.0GHz7The near field radiation profile of the circuit. Regardless of the capacitance C 1 The value is that the circuit signal is interrupted at two frequency points of 1.0GHz less than the low-frequency cut-off frequency and 8.0GHz more than the high-frequency cut-off frequency. At 1.0GHz, because the hollow bow-tie cell added with the capacitor in the filter does not support the transmission of low-frequency signals, namely the frequency point is less than the low-frequency cut-off frequency of the hollow bow-tie cell added with the capacitor, the transmission of the signals is interrupted at the hollow bow-tie cell added with the capacitor at the 1.0GHz frequency point; the 8.0GHz frequency exceeds the high frequency cut-off frequency of the solid cell, the hollow bow-tie cell and the hollow bow-tie cell with the capacitor added, so that the signal transmission in the solid cell is interrupted in the first wave conversion transition region. With variable capacitance C 1 Adjust in 0.3 ~ 1.8pF within range, the signal interruption appears in corresponding stop band frequency point in the wave filter: when C is present 1 Interruption at 2.95GHz when =1.8 pF; when C is present 1 Interruption at 3.1GHz when =1.4 pF; when C is 1 Interruption at 3.5GHz when =0.7 pF; when C is 1 Interruption at 3.8GHz, =0.5 pF; when C is 1 And when =0.3pF, interrupt at 4.3 GHz. Meanwhile, as can be seen from fig. 6 (c), the electromagnetic waves are tightly bound to the surface of each metal cell, and there is almost no energy leakage, which indicates that the filter of the present invention has high field binding property; meanwhile, the characteristic ensures that the filter hardly causes signal interference to other circuits with close distances and has low crosstalk performance of the circuit.
In some embodiments, a dc bias circuit is provided on the basis of the ideal simulated structure diagram of fig. 1 to excite the variable capacitor to work normally, so as to verify the feasibility of the filter of the present invention, as shown in fig. 7, which is a complete structure diagram of the filter in implementation.
A first DC blocking capacitor is arranged between the first coplanar waveguide transmission line and the first wave conversion transition region; and a second DC blocking capacitor is arranged between the second wave conversion transition region and the second coplanar waveguide transmission line. The direct current blocking capacitor is used for preventing direct current signals loaded at two ends of the variable capacitor from entering microwave signal input and output equipment to cause instrument faults.
A plurality of alternating current isolating inductors are arranged in the direct current bias circuit. The alternating current isolating inductor is used for preventing a microwave signal from flowing into the bias circuit and influencing the power supply of the direct current voltage source.
Illustratively, as shown in FIG. 7, the variable capacitance C 1 The model number of the strain is SMV2019-097LF; fixed capacitor C 2 =0.9pF; DC blocking capacitor C bias =120//680pF, where the symbol "//" denotes that the capacitors are connected in parallel; first AC isolated inductance L bias1 =390nH; second alternating current isolating inductor L bias2 =180nH. According to the values, the circuit is actually tested, and as shown in FIG. 8, a comparison graph of the measured S parameters of the filter of the invention in the frequency range of 0.5-16 GHz is shown.
In particular, with a DC voltage V cc Increased, variable capacitance C of 1 And the capacitance value is reduced, the frequency band of the stop band is increased, and the low-frequency cut-off frequency is increased. When the variable capacitance C 1 The closer to C the capacitance value of 2 =0.9pF, the narrower the corresponding stop band bandwidth, i.e. the lower the suppression level. Exemplary, when C 1 =0.81pF, there is almost no stop band in the filter pass band. Thereby confirming the feasibility of practical application of the filter of the present invention.
At the same time, no matter the variable capacitance C 1 How the capacitance value of the filter is changed, the filter has better | S in a wide frequency range exceeding the high-frequency cut-off frequency 21 Level of harmonic suppression. Illustratively, | S in the frequency range of 6-16 GHz 21 All | is less than-30 dB, therefore, the filter has deep high-frequency harmonic suppression performance.
In some embodiments, as shown in fig. 4 (b), variable capacitors C are added to the upper and lower ends of the hollow bow-tie cell respectively 1 ' and C 2 '. In practice, C 1 ' and C 2 The capacitance of both can be changed and equal to C 1 '＝C 2 '。
The hollow bow-tie cell is respectively provided with a variable capacitor C at the upper end and the lower end 1 ' and C 2 In the case of' the dispersion curves for the two modes of propagation are shown in fig. 5 (b), and the following conclusions can be drawn:
1. the hollow bow-tie cell with the capacitor added is under two propagation modesThe low-frequency part of the dispersion curve is superposed with the light dispersion curve, deviates from the light dispersion curve after reaching the respective turning point along with the increase of the frequency, falls into a slow wave region and gradually approaches to the high-frequency cut-off frequency of the slow wave region under two propagation modes. But with variable capacitance C 1 ' and C 2 The capacitance value is increased, the high-frequency cut-off frequency of the hollow bow-tie cell provided with the capacitor under the mode 1 is reduced, and the high-frequency cut-off frequency under the mode 2 is kept unchanged at 5.81 GHz.
2. When the dispersion curve of the hollow bow-tie cell element added with the capacitor is superposed with the dispersion curve of light, it is indicated that at this time, the electromagnetic wave is totally radiated into the external light, and the hollow bow-tie cell element does not support the transmission of signals on the surface thereof, so that in two transmission modes, the hollow bow-tie cell element added with the capacitor has a low-frequency cut-off frequency, and the frequency at each turning point corresponds to the respective low-frequency cut-off frequency.
3. When C is present 1 '＝C 2 ' and C 1 ' and C 2 When the capacitance value of the hollow bow-tie cell is adjusted within the range of 0.6-1.2 pF, no matter how two variable capacitors are adjusted, the low-frequency cut-off frequency of the hollow bow-tie cell added with the capacitors under the mode 2 is the same as the high-frequency cut-off frequency in the mode 1, namely, an intersection point exists in two propagation modes, a stop band cannot be formed, and the hollow bow-tie cell is of a band-pass structure.
4. With C 1 ' and C 2 The turning points under the mode 1 slightly move downwards due to the increase of the capacitance value, namely the low-frequency cut-off frequency of the hollow bow-tie cell element added with the capacitor is slightly reduced, so that the tunability of the low-frequency cut-off frequency and the band-pass range is realized.
In the structure diagram of the ideal simulation of the filter shown in fig. 1, variable capacitors C are respectively added to the upper and lower ends of the tunable hollow bow-tie cell 1 ' and C 2 ' and C 1 '＝C 2 In the case of the' system, the ideal filter is simulated, and as shown in fig. 6 (b), S-parameter ideal simulation results of the filter are obtained.
Specifically, as can be seen from fig. 6 (b), when the capacitance values of the variable capacitors added to the upper and lower ends of the tunable hollow bowtie cell in the filter are the same, no transmission stop band exists in the pass band of the cell dispersion curve. With the increase of the two variable capacitors, the low-frequency cut-off frequency of the pass band is gradually reduced from 2.75GHz to 1.83GHz; the high-frequency cut-off frequency of the pass band is kept at about 5.76GHz all the time and is not changed along with the adjustment of the two variable capacitors.
In summary, the invention provides a band-pass filter with tunable stop band and hollow bow-tie cell plasmons, wherein a first coplanar waveguide transmission line, a first wave conversion transition region, a hollow bow-tie cell group, a second wave conversion transition region and a second coplanar waveguide transmission line are sequentially disposed on a top layer of a metal circuit along an axis, and arc-shaped metal conductors are disposed at four top corners of the top layer of the metal circuit. The filter provided by the invention has a simple structure and is easy to realize.
Furthermore, the upper end and the lower end of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are cut off and connected by adding capacitors. Under the condition that one end of the hollow bow-tie cell element is added with the variable capacitor and the other end of the hollow bow-tie cell element is added with the fixed capacitor, the filter has the advantages of low crosstalk, high field constraint and deep high-frequency harmonic suppression, and can realize dynamic adjustment of low-frequency cut-off frequency, pass-band internal resistance band suppression level, bandwidth and frequency. Under the condition that the upper end and the lower end of the hollow bow-tie cell element are respectively added with the variable capacitors, the filter has the advantages of low crosstalk, high field constraint and deep high-frequency harmonic suppression, and can realize dynamic adjustment of low-frequency cut-off frequency, pass band bandwidth and frequency. The invention lays a foundation for the wide application of the artificial surface plasmon microwave device in the reconfigurable integrated microwave system and the electric control antenna feed network.
Those of ordinary skill in the art will appreciate that the various illustrative components, systems, and methods described in connection with the embodiments disclosed herein may be implemented as hardware, software, or combinations of both. Whether this is done in hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments can be stored in a machine-readable medium or transmitted by a data signal carried in a carrier wave over a transmission medium or a communication link.
It is to be understood that the invention is not limited to the precise arrangements and instrumentalities shown. A detailed description of known methods is omitted herein for the sake of brevity. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present invention are not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications and additions or change the order between the steps after comprehending the spirit of the present invention.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments in the present invention.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made to the embodiment of the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The utility model provides a stop band tunable fretwork bow tie cell element plasmon polariton band-pass filter which characterized in that includes:
a metal ground layer;
a dielectric slab layer disposed above the metal ground layer;
the metal circuit top layer is arranged above the dielectric slab layer and comprises a first coplanar waveguide transmission line, a first wave conversion transition region, a hollow bow-tie cell group, a second wave conversion transition region and a second coplanar waveguide transmission line which are sequentially connected along an axis; the metal circuit top layer is rectangular, four top corners of the metal circuit top layer are respectively provided with arc-shaped metal conductors, and the arc-shaped metal conductors are connected with the metal grounding layer through metal through holes; the first wave conversion transition area and the second wave conversion transition area are both formed by connecting a plurality of gradient-cut solid cells in series; the hollow bow-tie cell group consists of a plurality of hollow bow-tie cell elements, and each hollow bow-tie cell element is obtained by excavating a bow-tie-shaped through hole from the solid cell element; and the upper end and the lower end of a set number of hollow bow-tie cells in the middle of the hollow bow-tie cell group are cut off and connected by adding capacitors.
2. The band-pass filter of claim 1, wherein upper and lower ends of a predetermined number of the hollow-bowtie cells in the middle of the group of hollow-bowtie cells are cut off, and a variable capacitor is added at one end and a fixed capacitor is added at the other end.
3. The band-pass filter of claim 1, wherein the upper and lower ends of a predetermined number of hollow-bow-tie cells in the middle of the set of hollow-bow-tie cells are cut off, and variable capacitors are respectively added to the upper and lower ends; and in a single hollow bow-tie cell, the capacitance values of the variable capacitors at the two ends are equal.
4. The band-pass filter of claim 1, wherein the height of each solid cell in the first wave-converting transition region gradually increases along the first coplanar waveguide transmission line toward the set of bowtie cells;
and the height of each solid cell in the second wave conversion transition region is gradually reduced along the direction from the hollow bow-tie cell group to the second coplanar waveguide transmission line.
5. The band-pass filter of claim 1, wherein the group of the hollow-bowtie cells is composed of 7 hollow-bowtie cells connected in series, wherein the upper and lower ends of the middle 3 hollow-bowtie cells are cut off and connected by adding a capacitor; the first and second wave-converting transition regions each comprise 5 solid cells in series.
6. The stop-band tunable notch-junction cell plasmon band pass filter of claim 2 or 3, further comprising: the method comprises the steps that a direct current bias circuit is arranged to provide power for a hollow bow-tie cell added with a variable capacitor, and a plurality of alternating current isolation inductors are arranged in the direct current bias circuit.
7. The band-pass filter of claim 1, wherein a first dc blocking capacitor is disposed between the first coplanar waveguide transmission line and the first wave-converting transition region; and a second DC blocking capacitor is arranged between the second wave conversion transition region and the second coplanar waveguide transmission line.
8. The band-pass filter of claim 1, wherein the arc-shaped metal conductor is a quarter-ellipse.
9. The band-pass tunable stop-band notch-bowtie cell plasmon band-pass filter of claim 1 wherein the dielectric plate layer has a dielectric constant of 3.66 and a loss constant of 0.0037.
10. The band-pass tunable band-pass filter of claim 1, wherein the unit length of the solid cell periodically repeated in the circuit is 6 mm.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116053735A (en) * | 2023-03-20 | 2023-05-02 | 电子科技大学 | Adjustable terahertz SSPPs transmission line |
| CN116937091A (en) * | 2023-09-19 | 2023-10-24 | 中国计量大学 | Reconfigurable band-pass filter of SSPP and SIW hybrid circuit |
-
2022
- 2022-10-13 CN CN202211255644.6A patent/CN115588831A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116053735A (en) * | 2023-03-20 | 2023-05-02 | 电子科技大学 | Adjustable terahertz SSPPs transmission line |
| CN116053735B (en) * | 2023-03-20 | 2024-03-08 | 电子科技大学 | Adjustable terahertz SSPPs transmission line |
| CN116937091A (en) * | 2023-09-19 | 2023-10-24 | 中国计量大学 | Reconfigurable band-pass filter of SSPP and SIW hybrid circuit |
| CN116937091B (en) * | 2023-09-19 | 2023-12-08 | 中国计量大学 | Reconfigurable band-pass filter of SSPP and SIW hybrid circuit |
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