WO2019184270A1 - Annular surface wave transmission line fed by coplanar waveguide - Google Patents

Abstract

Disclosed is an annular surface wave transmission line fed by a coplanar waveguide, comprising a dielectric substrate, two coplanar waveguides, two transition segments, and an annular surface plasmon structure. The two coplanar waveguides, the two transition segments, and the annular surface plasmon structure are disposed on the same layer of the dielectric substrate. The two coplanar waveguides and the two transition segments are in a one-to-one correspondence, both the two coplanar waveguides and the two transition segments are symmetrically disposed, and each of the coplanar waveguides is connected to one end of the annular surface plasmon structure via a corresponding transition segment. The present invention can transmit an electromagnetic wave in a surface plasmon mode at a microwave frequency, has the features of a simple structure, wide working bandwidth, convenient processing, and high integration degree, and has great application value in microwave integrated circuits and communication systems.

Description

Coplanar waveguide-fed annular surface wave transmission line Technical field

The invention relates to a transmission line, in particular to a coplanar waveguide feeding annular surface wave transmission line, belonging to the field of integrated circuits and surface wave technologies.

Background technique

Surface plasmon (SPP) is an electromagnetic wave propagating along the interface between metal and medium. It has a larger wave number than the light wave in the direction of propagation, and an exponential field with an exponential decay in the direction perpendicular to the direction of propagation. Limited to sub-wavelength sizes. SPP can be excited and propagated in the microwave and terahertz bands using periodic holed conductors. The surface plasmon transmission line designed according to the above method is a single-line structure, which has an ultra-wide working bandwidth, a moderately curved transmission line, constant transmission performance, and high integration.

Coplanar waveguide (CPW), the conduction band and the grounding floor are on the same level, with small dispersion, easy to realize compact balance circuit, small interference between signal line and ground line, etc., widely used in microwave integrated circuits. Therefore, with CPW feeding, the designed transmission line structure is easy to process and has high integration.

According to the survey and understanding, the existing technologies that have been disclosed are as follows:

1) In 2004, J.B. Pendry et al. published a speech entitled "Mimicking Surface Plasmons with Structured" in SCIENCE. Surfaces" article. The authors propose that in the microwave and terahertz frequency bands, surface surface plasmons can be observed on the electrically conductive surface of perforated conductors, and theoretical analysis of the SPP design method is performed. This is the surface and surface plasmon of the microwave and terahertz band. The research and application of the radicals laid the foundation.

2) In 2013, Ma Huifeng and others published the article entitled "Broadband and high-efficiency conversion" From the guide waves to spoof surface plasmon polaritons, it is proposed to use a copper-plated ultra-thin dielectric plate to make a fishbone-shaped surface plasmon transmission line structure. Using CPW as an input and output signal, a rectangular double-sided ripple metal strip structure transmits SPP. Achieve efficient conversion between the SPP and the conventional transmission line CPW.

technical problem

In the prior art, no special processing is performed on the working bandwidth of the transmission line, resulting in a narrow working bandwidth of the transmission line.

Technical solution

Coplanar waveguide-fed annular surface wave transmission line comprising a dielectric substrate, two coplanar waveguides, two transition segments and an annular surface plasmon structure, the two coplanar waveguides, two transition segments and a ring surface plasmon excitation The meta-structure is disposed on the same layer of the dielectric substrate, and the two coplanar waveguides and the two transition segments are in one-to-one correspondence, and the two coplanar waveguides and the two transition segments are symmetrically disposed, and each coplanar waveguide passes through the corresponding The transition section is connected to one end of the annular surface plasmon structure.

Beneficial effect

The transmission line of the invention is provided with a coplanar waveguide and a transition section on the left and right sides of the same layer of the dielectric substrate, and a ring surface plasmon structure is arranged in the middle, thereby realizing a planar circuit structure without metal, and the electromagnetic wave is from the coplanar waveguide in the transition section. The TEM wave becomes the TM wave of the surface plasmon, and the surface wave enters the annular surface plasmon structure from the transition section. Each coplanar waveguide is connected to one end of the annular surface plasmon structure through the corresponding transition section. The surface wave transmission line realizes the conversion between the coplanar waveguide and the annular surface plasmon structure, and has the characteristics of wide working bandwidth, low frequency conduction and high frequency cutoff.

DRAWINGS

1 is a schematic structural view of a surface acoustic wave transmission line of a coplanar waveguide feeding according to Embodiment 1 of the present invention.

2 is a graph showing the transmission efficiency of the frequency response of the surface acoustic wave transmission line of the coplanar waveguide feeding according to Embodiment 1 of the present invention.

3 is a schematic structural view of a semi-annular surface wave transmission line fed by a coplanar waveguide according to Embodiment 2 of the present invention;

4 is a graph showing the transmission efficiency of the frequency response of the semi-annular surface wave transmission line of the coplanar waveguide feeding according to the second embodiment of the present invention with or without step impedance.

In Fig. 1, a 1-dielectric substrate, a 2-first coplanar waveguide, a 3-second coplanar waveguide, a 4-first transition section, a 5-second transition section, a 6-ring surface plasmon structure, 7- First annular transition unit, 8-first metal unit, 9-first transfer portion, 10-second annular transition unit, 11-second metal unit, 12-second transfer portion, 13-ring unit.

In Fig. 3, a 1-dielectric substrate, a 2-first coplanar waveguide, a 3-second coplanar waveguide, a 4-first transition section, a 5-second transition section, a 6-half-ring surface plasmon structure, 7 - first half annular transition unit, 8-first metal unit, 9 - first transfer portion, 10 - second semi-annular transition unit, 11 - second metal unit, 12 - second transfer portion, 13 - semi-ring unit , 14 - first stepped impedance structure, 15 - second stepped impedance structure.

BEST MODE FOR CARRYING OUT THE INVENTION

Coplanar waveguide-fed annular surface wave transmission line comprising a dielectric substrate, two coplanar waveguides, two transition segments and an annular surface plasmon structure, the two coplanar waveguides, two transition segments and a ring surface plasmon excitation The meta-structure is disposed on the same layer of the dielectric substrate, and the two coplanar waveguides and the two transition segments are in one-to-one correspondence, and the two coplanar waveguides and the two transition segments are symmetrically disposed, and each coplanar waveguide passes through the corresponding The transition section is connected to one end of the annular surface plasmon structure.

As a preferred solution, each transition section includes a plurality of annular transition units and metal units located on opposite sides of the plurality of annular transition units, the plurality of annular transition units are sequentially connected together, and the two ends are respectively corresponding to the corresponding coplanar waveguides, One end of the annular surface plasmon structure is connected.

As a preferred solution, in each transition segment, the plurality of annular transition units gradually become larger from one end of the corresponding coplanar waveguide to the annular surface plasmon structure.

As a preferred solution, in each transition segment, the metal unit gradually moves away from the annular transition unit from the junction of the annular transition unit and the corresponding coplanar waveguide, and at the junction of the annular transition unit and the annular surface plasmon structure. disappear.

As a preferred solution, the annular transition unit in each transition section is cut into a semi-annular transition unit, and the annular surface plasmon structure is cut into a semi-annular surface plasmon structure, and each coplanar waveguide is loaded with Step impedance structure.

As a preferred solution, the annular surface plasmon structure is composed of a plurality of annular units arranged in a periodic manner and sequentially connected together, and the size of each annular unit is uniform.

As a preferred solution, the height, width and thickness of each annular unit and the distance between two adjacent annular units are adjusted according to the desired frequency application range.

As a preferred solution, the two coplanar waveguides are a first coplanar waveguide and a second coplanar waveguide, respectively, and the two transition segments are a first transition segment and a second transition segment respectively; the first coplanar waveguide And the second coplanar waveguide is bilaterally symmetric, the first transition segment and the second transition segment are bilaterally symmetric, the first coplanar waveguide corresponds to the first transition segment, the second coplanar waveguide corresponds to the second transition segment, and the first coplanar waveguide passes through the first A transition section is coupled to the left end of the annular surface plasmon structure, and the second coplanar waveguide is coupled to the right end of the annular surface plasmon structure via the second transition section.

Embodiments of the invention

Example 1:

As shown in FIG. 1 , this embodiment provides a coplanar waveguide-fed annular surface wave transmission line including a dielectric substrate 1 , a first coplanar waveguide 2 , a second coplanar waveguide 3 , and a first Transition section 4, second transition section 5 and annular surface plasmon structure 6, said first coplanar waveguide 2, second coplanar waveguide 3, first transition section 4, second transition section 5 and annular surface plasmon excitation The element structure 6 is disposed on the same layer of the dielectric substrate 1, and is disposed on the top layer in the embodiment, the bottom layer of the dielectric substrate 1 is not covered with copper, and the dielectric substrate 1 is preferably a PCB board; the first coplanar waveguide 2 and the The second coplanar waveguide 3 is bilaterally symmetric, the first transition section 4 and the second transition section 5 are bilaterally symmetric, and the first coplanar waveguide 2 corresponds to the first transition section 4, and the second coplanar waveguide 3 and the second transition Segment 5 corresponds.

The first transition section 4 includes a plurality of first annular transition units 7 and first metal units 8 located on opposite sides of the plurality of first annular transition units 7; left ends of the plurality of first annular transition units 7 and the first The coplanar waveguide 2 is connected, the right end is connected to the left end of the annular surface plasmon structure 6, the plurality of first annular transition units 7 are sequentially connected from left to right, and gradually become larger, and the first metal unit 8 is gradually changed from left to right. Small, that is, gradually away from the first annular transition unit 7 from the junction of the first annular transition unit 7 and the first coplanar waveguide 2, and at the junction of the first annular transition unit 7 and the left end of the annular surface plasmon structure 6 Disappearing, the first annular transition unit 7 can be changed according to the actual use occasion, the more the first annular transition unit 7 is, the smoother the conversion; the electromagnetic wave is in the first transition section 4 from the first transmission part of the first coplanar waveguide 2 TEM (Transverse Electric and Magnetic Field), which means that the electric field and the magnetic field of the electromagnetic wave are in a plane perpendicular to the propagation direction, the wave becomes the TM of the annular surface plasmon structure 6 (Transverse Magnetic). The TM wave enters the annular surface plasmon structure 6 from the first transition section 4, and is converted back to the TEM wave by the second transition section 5 to be transmitted to the second coplanar waveguide 3.

The second transition section 5 includes a plurality of second annular transition units 10 and second metal units 11 located on opposite sides of the plurality of second annular transition units 10; right ends and second ends of the plurality of second annular transition units 10 The coplanar waveguide 3 is connected, the left end is connected to the right end of the annular surface plasmon structure 6, the plurality of second annular transition units 10 are sequentially connected from right to left, and gradually become larger, and the second metal unit 11 is gradually changed from right to left. Small, that is, from the junction of the second annular transition unit 10 and the second coplanar waveguide 3, gradually away from the second annular transition unit 10, and at the junction of the second annular transition unit 10 and the left end of the annular surface plasmon structure 6 Disappearing, likewise, the second annular transition unit 10 can be changed according to the actual use occasion, and the more the second annular transition unit 10, the smoother the conversion; similarly, the electromagnetic wave is from the second coplanar waveguide in the second transition section 5. The TEM wave of the second transmission portion 12 of 3 becomes the TM wave of the annular surface plasmon structure 6, and the TM wave enters the annular surface plasmon structure 6 from the second transition portion 5, and is converted back through the first transition portion 4. TEM wave transmission 2 to the first coplanar waveguide.

The annular surface plasmon structure 6 is composed of a plurality of annular units 13 arranged in a periodic manner and sequentially connected together. The number of the annular units 13 is set according to actual needs, and the size of each annular unit 13 is Consistent, and the height, width and thickness of each annular unit and the distance between two adjacent annular units are adjusted according to the required frequency application range; the first coplanar waveguide 2, the first transition section 4, The annular surface plasmon structure 6, the second coplanar waveguide 3, and the second transition segment 5 are sequentially connected to form a surface wave transmission line.

As shown in FIG. 2, the transmission efficiency curve of the frequency response of the ring surface wave transmission line fed by the coplanar waveguide of the present embodiment can be seen, and the TM wave of the surface plasmon is efficiently transmitted in the range of 2 GHz to 12 GHz. The utility model has the advantages of wide working bandwidth and convenient processing.

Example 2:

As shown in FIG. 3, in the embodiment, the toroidal surface wave transmission line in Embodiment 1 can only intercept a semi-annular surface wave transmission line which can form a coplanar waveguide feeding line on the center line, and the semi-annular surface wave transmission line includes a dielectric substrate. 1. First coplanar waveguide 2, second coplanar waveguide 3, first transition section 4, second transition section 5 and semi-annular surface plasmon structure 6, said first coplanar waveguide 2, second coplanar The waveguide 3, the first transition section 4, the second transition section 5, and the semi-annular surface plasmon structure 6 are disposed on the same layer of the dielectric substrate 1, which is disposed on the top layer in this embodiment, and the underlying layer of the dielectric substrate 1 is free of copper. The first coplanar waveguide 2 and the second coplanar waveguide 3 are bilaterally symmetric, the first transition segment 4 and the second transition segment 5 are bilaterally symmetric, and the first coplanar waveguide 2 is coupled to the first transition segment 4 Correspondingly, the second coplanar waveguide 3 corresponds to the second transition section 5.

The first transition section 4 includes a plurality of first semi-annular transition units 7 and first metal units 8 located on opposite sides of the plurality of first semi-annular transition units 7; left ends of the plurality of first semi-annular transition units 7 Connected to the first coplanar waveguide 2, the right end is connected to the left end of the semi-annular surface plasmon structure 6, the first semi-annular transition unit 7 is sequentially connected from left to right, and gradually becomes larger, the first metal unit 8 is from left to The right gradually becomes smaller, that is, gradually away from the first semi-annular transition unit 7 from the junction of the first semi-annular transition unit 7 and the first coplanar waveguide 2, and plasmon on the first semi-annular transition unit 7 and the semi-annular surface The connection of the left end of the meta-structure 6 disappears, and the first semi-annular transition unit 7 can be changed according to the actual use occasion, and the more the first semi-annular transition unit 7 is, the smoother the conversion is; the electromagnetic wave is from the first transition section 4 from the first The TEM wave of the first transmission portion 9 of the coplanar waveguide 2 becomes the TM wave of the semi-annular surface plasmon structure 6, and the TM wave enters the semi-annular surface plasmon structure 6 from the first transition section 4, and passes through the second Transition section 5 is converted back to TEM wave transmission 3 to the second coplanar waveguide.

The second transition section 5 includes a plurality of second semi-annular transition units 10 and second metal units 11 located on opposite sides of the plurality of second semi-annular transition units 10; right ends of the plurality of second semi-annular transition units 10 Connected to the second coplanar waveguide 3, the left end is connected to the right end of the semi-annular surface plasmon structure 6, the second semi-annular transition unit 10 is sequentially connected from right to left, and gradually becomes larger, and the second metal unit 11 is from right to The left gradually becomes smaller, that is, from the junction of the second semi-annular transition unit 10 and the second coplanar waveguide 3 gradually away from the second semi-annular transition unit 10, and the second semi-annular transition unit 10 and the semi-annular surface plasmon The connection at the left end of the structure 6 disappears. Similarly, the second semi-annular transition unit 10 can be changed according to the actual use occasion, and the more the second semi-annular transition unit 10, the smoother the conversion; similarly, the electromagnetic wave is in the second transition section. The TEM wave from the second transmission portion 12 of the second coplanar waveguide 3 becomes a TM wave of the semi-annular surface plasmon structure 6, and the TM wave enters the semi-annular surface plasmon structure 6 from the second transition portion 5 And then pass the first 4 cross section TEM wave is converted back to the first coplanar waveguide transmission 2.

The semi-annular surface plasmon structure 6 is composed of a plurality of semi-annular units 13 arranged in a periodic manner and sequentially connected together. The number of the semi-annular units 13 is set according to actual needs, and each semi-annular ring The dimensions of the unit 13 are identical, and the height, width and thickness of each semi-annular unit and the distance between two adjacent semi-annular units are adjusted according to the required frequency application range; the first coplanar waveguide 2 The first transition section 4, the semi-annular surface plasmon structure 6, the second coplanar waveguide 3 and the second transition section 5 are sequentially connected to form a surface wave transmission line.

However, such a semi-annular surface wave transmission line cannot transmit the TM wave of the surface plasmon, and the transmission efficiency curve of the transmission line frequency response is poor. In order to re-reach the impedance matching of the semi-annular transmission line, the first transmission in the first coplanar waveguide 2 The portion 9 loads the first stepped impedance structure 14, and the second transmission portion 12 of the second coplanar waveguide 3 loads the second stepped impedance structure 15 from S11 to less than -10 dB from 4 GHz to 11.5 GHz, and S21 at 4.5 GHz to 7.5 GHz. More than -1.5dB, the high-efficiency conversion between the quasi-TEM wave on the coplanar waveguide and the TM wave on the surface plasmon can be completed within the working bandwidth; the circular surface wave transmission line of the above embodiment 1 is simple and symmetrical, and has a much larger The frequency passband range of the semi-annular surface wave transmission line, although the step impedance of the semi-annular surface wave transmission line can adjust the impedance of the coplanar waveguide and the surface plasmon to match, the performance of S11 is better, but the working bandwidth is compared with that of Embodiment 1 The circular surface wave transmission line is narrowed.

In summary, the transmission line of the present invention is provided with a coplanar waveguide and a transition section on the left and right sides of the same layer of the dielectric substrate, and a ring surface plasmon structure is disposed in the middle to realize a planar circuit structure without metal, and the electromagnetic wave is in transition. The TEM wave from the coplanar waveguide becomes the TM wave of the surface plasmon, and the surface wave enters the annular surface plasmon structure from the transition section. Each coplanar waveguide passes through the corresponding transition section and the annular surface plasmon structure. One end of the connection constitutes a surface wave transmission line, which realizes the conversion between the coplanar waveguide and the annular surface plasmon structure, and has the characteristics of wide working bandwidth, low frequency conduction and high frequency cutoff.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, and any person skilled in the art can disclose the patent according to the present invention within the scope disclosed by the present patent. The technical solutions and the inventive concepts thereof are equivalently replaced or changed, and are all within the scope of protection of the present invention.

Industrial applicability

1. The transmission line of the present invention is provided with a coplanar waveguide and a transition section on the left and right sides of the same layer of the dielectric substrate, and a ring surface plasmon structure is disposed in the middle, thereby realizing a planar circuit structure without metal ground, and electromagnetic waves are in common in the transition section. The TEM wave of the surface waveguide becomes the TM wave of the surface plasmon, and the surface wave enters the annular surface plasmon structure from the transition section, and each coplanar waveguide passes through the corresponding transition section and one end of the annular surface plasmon structure. The connection constitutes a surface wave transmission line, which realizes the conversion between the coplanar waveguide and the annular surface plasmon structure, and has the characteristics of wide working bandwidth, low frequency conduction and high frequency cutoff.

2. In the transmission line of the present invention, the transition section includes a plurality of annular transition units and metal units located on both sides of the annular transition unit, the annular transition units are sequentially connected and gradually enlarged, the metal unit gradually moves away from the annular transition unit, and finally disappears completely. The circular transition unit can be changed according to the actual use occasion, and the more transition units, the smoother the conversion.

3. In the transmission line of the present invention, the annular surface plasmon structure is composed of a plurality of ring units of the same size, and the number of the ring units can be set according to actual needs, which can be bent, so that the lines are more flexible and can be customized according to requirements. The frequency application range is adjusted for the height, width and thickness of each ring unit and the distance between two adjacent ring units. The geometric parameters of each ring unit can control the highest cutoff frequency.

4. In the transmission line of the present invention, a plurality of annular transition units in each transition section may be cut into semi-annular transition units, and the annular surface plasmon structure is cut into a semi-annular surface plasmon structure, at each The stepped impedance structure is loaded on the coplanar waveguide, and the step impedance structure can adjust the impedance of the coplanar waveguide and the surface plasmon to match. The simulation results show that S11 is less than -10dB from 4GHz to 11.5GHz, and S21 is at 4.5GHz~7.5. The GHz is greater than -1.5dB, and the efficient conversion between the quasi-TEM wave on the coplanar waveguide and the TM wave on the surface plasmon can be achieved within the operating bandwidth.

5. The invention can complete the efficient conversion between the conventional coplanar waveguide and the surface plasmon transmission line, and provides a basis for the wide application of the surface plasmon excitation component in the microwave integrated circuit and the communication system, and is easy to process, and the transmission line is moderately bent and transmitted. The performance remains the same, which has great potential for promoting the miniaturization, integration and scale development of circuits.

Claims (8)

1. Coplanar waveguide-fed annular surface wave transmission line, comprising a dielectric substrate, further comprising two coplanar waveguides, two transition segments and an annular surface plasmon structure, the two coplanar waveguides, two transitions The segment and annular surface plasmon structures are disposed on the same layer of the dielectric substrate, and the two coplanar waveguides and the two transition segments are in one-to-one correspondence, and the two coplanar waveguides and the two transition segments are symmetrically disposed, each of which is symmetrically disposed. The coplanar waveguide is connected to one end of the annular surface plasmon structure through a corresponding transition section.
2. The coplanar waveguide-fed annular surface wave transmission line according to claim 1, wherein each transition section comprises a plurality of annular transition units and metal units located on opposite sides of the plurality of annular transition units, and a plurality of annular transition units Connected together in sequence, and the two ends are respectively connected to one end of the corresponding coplanar waveguide, annular surface plasmon structure.
3. The coplanar waveguide-fed annular surface wave transmission line according to claim 2, wherein in each transition segment, the plurality of annular transition units are from a corresponding coplanar waveguide to a ring surface plasmon structure. One end gradually becomes larger.
4. The coplanar waveguide-fed annular surface wave transmission line according to claim 2, wherein in each transition segment, the metal unit starts to gradually move away from the annular transition unit from the junction of the annular transition unit and the corresponding coplanar waveguide. And disappears at the junction of the annular transition unit and the annular surface plasmon structure.
5. The coplanar waveguide-fed annular surface wave transmission line according to claim 2, wherein the annular transition unit in each transition section is cut into a semi-annular transition unit, and the annular surface plasmon structure is cut into A semi-annular surface plasmon structure with a stepped impedance structure applied to each coplanar waveguide.
6. The coplanar waveguide-fed annular surface wave transmission line according to any one of claims 1 to 4, wherein the annular surface plasmon structure is composed of a plurality of ring units, and the plurality of ring units are arranged in a cycle. And connected together in turn, each ring unit has the same size.
7. The coplanar waveguide-fed annular surface wave transmission line according to claim 6, wherein the height, the width and the thickness of each of the annular units and the distance between the adjacent two annular units are as required The frequency application range is adjusted.
8. The coplanar waveguide-fed toroidal surface wave transmission line according to any one of claims 1 to 4, wherein the two coplanar waveguides are a first coplanar waveguide and a second coplanar waveguide, respectively, The two transition sections are a first transition section and a second transition section, respectively;

   The first coplanar waveguide and the second coplanar waveguide are bilaterally symmetric, the first transition segment and the second transition segment are bilaterally symmetric, the first coplanar waveguide corresponds to the first transition segment, and the second coplanar waveguide corresponds to the second transition segment, first The coplanar waveguide is connected to the left end of the annular surface plasmon structure through the first transition section, and the second coplanar waveguide is connected to the right end of the annular surface plasmon structure through the second transition section.