CN110311195A - A Miniaturized Ultra-Wideband Artificial Surface Plasmon Bandpass Filter - Google Patents

Abstract

The invention discloses a miniaturized ultra-broadband artificial surface plasmon bandpass filter, which comprises an upper metal structure, a first dielectric substrate, a middle traditional plasmon waveguide, and a second dielectric substrate arranged sequentially from top to bottom And the lower metal structure, the middle of the upper metal structure is a single-conductor miniaturized plasmonic waveguide, the two ends of the waveguide are respectively connected to a transition section, and the other end of the transition section is connected to the first metal strip; the middle traditional plasmonic waveguide and The upper-layer single-conductor miniaturized plasmonic waveguide has the same length, including several artificial surface plasmon unit structures; the lower-layer metal structure includes two symmetrical structures that are not connected in the middle, and the symmetrical structures include a rectangular metal ground, a trapezoidal Metal ground transition structure and underlying artificial surface plasmon transition structure. The invention can reduce the electrical size to 26% of the traditional artificial surface plasmon structure, and expand the relative working bandwidth of the band-pass filter to 180%.

Description

A Miniaturized Ultra-Wideband Artificial Surface Plasmon Bandpass Filter

technical field

The invention relates to a band-pass filter, in particular to a miniaturized ultra-wideband artificial surface plasmon band-pass filter.

Background technique

Surface plasmons are optical surface waves excited by the interaction of photons and electrons at the metal/dielectric interface, which have unique advantages such as wavelength compression and near-field enhancement. However, such surface plasmons are essentially impossible when the operating frequency is scaled down to the microwave band, since metals behave as perfect electrical conductors. Instead, by periodically etching subwavelength artificial structures on metals, artificial surface plasmons can be excited and used to mimic optical surface plasmons at microwave wavelengths. Among them, the ultrathin two-dimensional artificial surface plasmon waveguide has attracted extensive attention because it is easier to integrate with traditional radio frequency circuits. Since the effective conversion method between artificial surface plasmon waveguides and traditional circuits was proposed, the application of ultrathin artificial surface plasmon waveguides in radio frequency circuits has been increasing. Because ultra-wideband bandpass filters are key components in modern broadband wireless communication systems, the design of ultrawideband bandpass filters using artificial surface plasmon waveguides has significant engineering value. Because of its high-frequency cut-off characteristics, the artificial surface plasmon waveguide is a natural low-pass filter. By introducing a low-frequency transmission zero point, the artificial surface plasmon waveguide bandpass filter can be designed.

Contents of the invention

Purpose of the invention: To provide a design method of an artificial surface plasmon bandpass filter, which has remarkable ultra-wideband and miniaturization effects.

Technical solution: In order to realize the above-mentioned invention purpose, the present invention adopts the following technical solutions:

A miniaturized ultra-wideband artificial surface plasmon bandpass filter, including an upper metal structure, a first dielectric substrate, a middle traditional plasmon waveguide, a second dielectric substrate and a lower metal structure arranged in sequence from top to bottom , wherein the upper metal structure includes two first metal strips, two transition sections of micro-slotted artificial surface plasmon units whose sawtooth height gradually increases, and a single conductor containing several micro-slotted artificial surface plasmon units The miniaturized plasmonic waveguide, the single-conductor miniaturized plasmonic waveguide is located in the middle, and its two ends are respectively connected to a transition section, and the other end of the transition section is connected to the first metal strip; the middle traditional plasmonic waveguide and The single-conductor miniaturized plasmonic waveguide has the same length, including several artificial surface plasmon unit structures, and the number of artificial surface plasmon unit structures is the same as that of the micro-grooved artificial surface in the single-conductor miniaturized plasmonic waveguide The number of plasmonic units is the same; the lower metal structure includes two disconnected symmetrical structures in the middle, and the symmetrical structure includes a metal ground, a metal ground transition structure and a lower artificial surface plasmon transition structure from one end to the middle.

Optionally, a number of "bow"-shaped grooves are longitudinally opened in the middle of the micro-slotted artificial surface plasmon unit, and a number of "bow"-shaped grooves are respectively opened horizontally at the upper and lower ends.

Optionally, the single-conductor miniaturized plasmonic waveguide coincides with the middle-layer traditional plasmonic waveguide on the x-y plane, and is separated by the first dielectric substrate in the z direction. Together, they form a dual-conductor miniaturized artificial surface plasmon waveguide. Exciton waveguide.

Optionally, the cutoff frequency of the dual-conductor miniaturized artificial surface plasmon waveguide is 4.25 GHz, and the corresponding cutoff wavelength is 66.7 mm.

Optionally, the upper metal structure and the lower metal structure together form a conversion structure between a microstrip line and a dual-conductor miniaturized artificial surface plasmon waveguide.

Optionally, the lower metal structure partially overlaps with the traditional middle-layer plasmonic waveguide on the x-y plane, and the overlapping position is on both sides of the middle-layer traditional plasmonic waveguide, and the range is one unit scale. separated.

Optionally, the metal ground in the lower metal structure is a rectangular structure, and the metal ground transition structure is a trapezoidal structure.

Optionally, the passband range of the bandpass filter is 0.23-4.25GHz, the relative bandwidth is as high as 180%, and the group delay within the passband range is between 1-1.8ns.

Beneficial effects: Compared with the prior art, the present invention can significantly increase the passband bandwidth of the bandpass filter, and greatly reduce the geometric size of the artificial surface plasmon waveguide, which is beneficial to the overall miniaturization of the application system. In addition, the invention is simple to manufacture, convenient to operate, easy to integrate, and only needs one-step photolithography process, which not only saves the cost, but also avoids processing errors caused by complex structures.

Description of drawings

Figure 1 is a schematic diagram of a miniaturized artificial surface plasmon bandpass filter, where (a) is the overall schematic diagram, and (b) is a layered display diagram;

Figure 2 shows the structure of the miniaturized artificial surface plasmon unit and the surface current distribution, where (a) is the schematic diagram of the structure, and (b) the surface current distribution diagram;

Figure 3 is a comparison of the dispersion curves of traditional and miniaturized surface plasmon units;

Fig. 4 is the S parameter of the miniaturized artificial surface plasmon bandpass filter;

Fig. 5 is the group delay of the miniaturized artificial surface plasmon bandpass filter;

Figure 6 is an experimental sample of a miniaturized artificial surface plasmon bandpass filter;

In the figure: 1 is the upper metal structure, 2 is the first dielectric substrate, 3 is the middle traditional plasmonic waveguide, 4 is the second dielectric substrate, 5 is the lower metal structure, 11 is the first metal strip, 12 is the transition Section 13 is a single-conductor miniaturized plasmon waveguide, 51 is a rectangular metal ground, 52 is a trapezoidal metal ground transition structure, and 53 is a lower artificial surface plasmon transition structure.

Detailed ways

The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1(a) is the overall model of the proposed miniaturized artificial surface plasmon bandpass filter, including two dielectric substrates, and a three-layer metal structure located between the two dielectric substrates and on the upper and lower surfaces. The dielectric constants of the dielectric substrates are the same, both being 3.48, and the thicknesses of the substrates are 0.762 mm and 0.101 mm, respectively. Figure 1(b) is a layered display of a three-layer metal structure, in which the upper metal structure 1 includes a first metal strip 11, two micro-slotted artificial surface plasmon unit transition sections 12 with gradually increasing sawtooth heights and A single-conductor miniaturized plasmon waveguide 13 comprising several micro-grooved artificial surface plasmon units, two transition sections 12 are respectively located at both ends of the upper metal strip, and the transition section is connected to the first metal strip, and It is arranged symmetrically on both sides of the upper metal strip, and the single-conductor miniaturized plasmonic waveguide is located between the transition sections. The traditional mid-level plasmonic waveguide 3 has the same length as the single-conductor miniaturized plasmonic waveguide, and is also composed of the same number of artificial surface plasmon units. The difference is that the artificial surface plasmon unit structure here is traditional No micro grooved form. The micro-slotted artificial surface plasmon unit is made of horizontal and vertical micro-slots on the traditional zigzag artificial surface plasmon structure, and there is a dislocation, so that the conductor structure is not truncated (forming a similar "bow" structure ). The upper-layer single-conductor miniaturized plasmonic waveguide and the middle-layer traditional plasmonic waveguide overlap on the x-y plane, and are separated by the first dielectric substrate in the z-direction. Together, they form a dual-conductor miniaturized artificial surface plasmon waveguide . The lower metal structure 5 is composed of two symmetrical parts, which are respectively located at two ends of the overall structure, and its components include a rectangular metal ground 51 , a trapezoidal metal ground transition structure 52 and a lower artificial surface plasmon transition structure 53 . The upper metal structure and the lower metal structure jointly constitute the conversion structure of the microstrip line and the miniaturized artificial surface plasmon waveguide of the double conductor. There is a cell-scale overlapping range between the lower metal structure and the middle traditional plasmonic waveguide on both sides, overlapping in the x-y plane, and separated by the second dielectric substrate in the z direction.

As shown in Fig. 1, the radio frequency signal is fed into the bandpass filter through the feeding structure composed of the first metal strip 11 and the rectangular metal ground 51 at one end, and passes through the artificial surface plasmon unit transition section 12 and the trapezoidal metal The ground transition structure 52 and the lower artificial surface plasmon transition structure 53 are converted into plasmon surface waves, and signals with frequencies within the bandpass frequency range will be transmitted to the other end, and other radio frequency signals will be reflected, so achieve an effective filtering effect.

The value of each parameter is: d=4.7mm, h1=1.2mm, h2=0.8mm, h3=0.4mm, h4=1mm, h5=0.7mm, h6=0.4mm, L1=8mm, L2=9.8mm, Wt = 12.8 mm.

As shown in Figure 2, (a) is the micro-grooved artificial surface plasmon unit structure proposed by the present invention, and (b) is the corresponding surface current distribution obtained by full-wave simulation. It can be seen that the micro-groove design on the surface of the unit greatly increases the conduction path of the current, thus forming a significant miniaturization effect.

The values of the parameters of the unit in Fig. 2(a) are: a=2.8mm, p=4.7mm, H=5.2mm, h=1.6mm, w _g =0.2mm, ts=0.762mm.

As shown in Figure 3, the eigensimulation simulation is performed on the miniaturized surface plasmon unit proposed by the present invention, where the abscissa represents the transmission frequency, and the ordinate represents the dispersion, and the cutoff frequency of the dispersion curve can be obtained as 4.25 GHz, corresponding to The cutoff wavelength is 66.7mm, as shown by the dotted line in the figure; in order to compare the effect of miniaturization, as shown by the solid line in Figure 3, the dispersion curve of the traditional single-layer unslotted plasmonic unit is also given here , whose geometric dimensions are the same as those of the miniaturized surface plasmon unit of the present invention, its cut-off frequency is 17 GHz, and the corresponding cut-off wavelength is 17.6 mm. Therefore, in terms of cut-off wavelength, the electrical size of the designed dual-conductor miniaturized artificial surface plasmon waveguide is reduced to 26% of the traditional structure, and the miniaturization effect is obvious.

Fig. 4 is the S parameter of the miniaturized artificial surface plasmon bandpass filter, wherein the abscissa represents the transmission frequency, and the ordinate represents the amplitude; Fig. 4 illustrates that the 3dB passband range of the designed bandpass filter (S11 <-10dB, S21>-3 dB) is 0.23-4.25GHz, the relative bandwidth is as high as 180%, which greatly exceeds the relative bandwidth of the traditional bandpass filter, and the insertion loss is only 0.1dB, highlighting the filter's Efficient transmission performance.

Figure 5 shows the group delay data of the miniaturized artificial surface plasmon bandpass filter. It can be seen that within the passband range, the group delay ranges from 1 to 1.8 ns. It shows that this filter has good signal fidelity characteristics.

Figure 6 is a physical picture of the fabricated sample, which shows the front and back photos of the filter. The sample size is only 11.2 cm ² (0.07λ ₀ ² ), where λ ₀ is the filter center operating frequency. The 1cm line segment is given in the figure, which proves the miniaturization effect of this design intuitively through comparison.

A miniaturized ultra-wideband surface plasmon bandpass filter of the invention. The filter is a three-layer metal structure separated by two dielectric substrates. The upper metal structure is a micro-slotted double-sided serrated artificial surface plasmon transmission line. In order to achieve a good match, the sawtooth height is designed from low to high. The middle layer metal structure is a section of plasmon transmission line with the same sawtooth height, which is located in the center and shorter than the upper layer transmission line, and the zigzag unit structure corresponds to the position of the upper layer structure one by one. The lower metal structure is divided into two sections with the same shape, which are symmetrically designed at both ends of the overall structure of the filter. Near both ends is a rectangular metal ground, which transitions to a section of truncated plasmon transmission line through a trapezoidal conversion structure. There is an overlapping range of cell size between the lower cut-off plasmon transmission line and the middle structure, which forms a capacitive coupling feeding effect, so as to realize the low-frequency suppression effect of the band-pass filter, and the high-frequency cut-off effect of the filter is determined by The natural low-pass characteristic of the artificial surface plasmon transmission line is realized. This design can reduce the electrical size to 26% of the traditional artificial surface plasmon structure, and expand the relative operating bandwidth of the bandpass filter to 180% for the first time.

Compared with the prior art, the invention can significantly increase the passband bandwidth of the bandpass filter, and greatly reduce the geometric size of the artificial surface plasmon waveguide, which is beneficial to the overall miniaturization of the application system. In addition, the invention is simple to manufacture, convenient to operate, easy to integrate, and only needs one-step photolithography process, which not only saves the cost, but also avoids processing errors caused by complex structures.

Claims (8)

1. A miniaturized ultra-broadband artificial surface plasmon bandpass filter, characterized in that: it includes an upper metal structure (1), a first dielectric substrate (2), a middle traditional plasma The excitonic waveguide (3), the second dielectric substrate (4) and the lower metal structure (5), wherein the upper metal structure includes two first metal strips (11), two artificial micro-slots with gradually increasing sawtooth heights A surface plasmon unit transition section (12) and a single-conductor miniaturized plasmon waveguide (13) comprising several micro-grooved artificial surface plasmon units, the single-conductor miniaturized plasmon waveguide is located in the middle, And its two ends are respectively connected to a transition section, and the other end of the transition section is connected to the first metal strip; the traditional plasmonic waveguide (3) in the middle layer has the same length as the single-conductor miniaturized plasmonic waveguide (13), including several Artificial surface plasmon unit structure, and the number of artificial surface plasmon unit structures is the same as the number of micro-slotted artificial surface plasmon units in a single-conductor miniaturized plasmon waveguide (13); the underlying metal structure It includes two disconnected symmetrical structures in the middle, and the symmetrical structure includes a metal ground (51), a metal ground transition structure (52) and a lower artificial surface plasmon transition structure (53) from one end to the middle. 2. A miniaturized ultra-wideband artificial surface plasmon bandpass filter according to claim 1, characterized in that: a number of "bow" shaped grooves are longitudinally opened in the middle of the micro-slotted artificial surface plasmon unit , there are a number of "bow" shaped grooves in the horizontal direction at the upper and lower ends. 3. A miniaturized ultra-wideband artificial surface plasmon bandpass filter according to claim 1, characterized in that: the single-conductor miniaturized plasmon waveguide and the middle traditional plasmon waveguide are on the x-y plane overlapped, separated by the first dielectric substrate in the z direction, and the two together form a double-conductor miniaturized artificial surface plasmon waveguide. 4. A miniaturized ultra-wideband artificial surface plasmon bandpass filter according to claim 3, characterized in that: the cut-off frequency of the dual-conductor miniaturized artificial surface plasmon waveguide is 4.25 GHz, and the corresponding The cutoff wavelength is 66.7mm. 5. A miniaturized ultra-wideband artificial surface plasmon bandpass filter according to claim 1, characterized in that: the upper metal structure and the lower metal structure together form a microstrip line and a dual-conductor miniaturized artificial surface, etc. Converting structure of excitonic waveguides. 6. A miniaturized ultra-wideband artificial surface plasmon bandpass filter according to claim 1, characterized in that: the lower metal structure and the middle traditional plasmon waveguide partially overlap on the x-y plane, and the overlapping position On both sides of the traditional plasmonic waveguide in the middle layer, the range is one unit scale, separated by the second dielectric substrate in the z direction. 7. A miniaturized ultra-wideband artificial surface plasmon bandpass filter according to claim 1, characterized in that: the metal ground in the lower metal structure is a rectangular structure, and the metal ground transition structure is a trapezoidal structure. 8. A miniaturized ultra-wideband artificial surface plasmon bandpass filter according to claim 1, characterized in that: the bandpass range of the bandpass filter is 0.23-4.25GHz, and the relative bandwidth is as high as 180%. The group delay in the passband range is between 1-1.8ns.