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EP-4199243-B1 - SPOOF SURFACE PLASMON POLARITON TRANSMISSION LINE STRUCTURE, CIRCUIT BOARD AND ELECTRONIC DEVICE

EP4199243B1EP 4199243 B1EP4199243 B1EP 4199243B1EP-4199243-B1

Inventors

  • LIANG, Yuan
  • GENG, DONGYU

Dates

Publication Date
20260513
Application Date
20210812

Claims (14)

  1. A spoof surface plasmon polariton transmission line structure (100), comprising a first dielectric substrate (10), a first metal strip (20), and a second metal strip (30), wherein the first metal strip (20) and the second metal strip (30) are respectively disposed on two opposite surfaces of the first dielectric substrate (10), the first metal strip (20) and the second metal strip (30) separately extend in a first direction, and a length of the first metal strip (20) in the first direction is less than a length of the second metal strip (30) in the first direction; and in the first direction, a cross-sectional area of the first metal strip (20) gradually decreases, and at least one side of the second metal strip (30) has a plurality of protrusion parts (31) spaced apart, wherein the spoof surface plasmon polariton transmission line structure (100) further comprises a second dielectric substrate (40) and a third metal strip (50), wherein the second dielectric substrate (40) is laminated on a surface that is of the first dielectric substrate (10) and on which the second metal strip (30) is disposed, and the third metal strip (50) is disposed on a surface that is of the second dielectric substrate (40) and that faces away from the first dielectric substrate (10); and the third metal strip (50) extends in the first direction, and a length of the third metal strip (50) in the first direction is less than the length of the second metal strip (30) in the first direction; and a cross-sectional area of the third metal strip (50) gradually decreases in the first direction.
  2. The spoof surface plasmon polariton transmission line structure (100) according to claim 1, wherein the second metal strip (30) comprises a first segment and a second segment in the first direction, areas of protrusion parts (31) disposed in the first segment gradually increase to a specified value, areas of protrusion parts (31) disposed in the second segment are equal and are all the specified value, and the second segment forms a spoof surface plasmon polariton transmission line having a single-layer metal structure.
  3. The spoof surface plasmon polariton transmission line structure (100) according to claim 1 or 2, wherein a plurality of protrusion parts (31) on a same side of the second metal strip (30) are evenly spaced apart.
  4. The spoof surface plasmon polariton transmission line structure (100) according to any one of claims 1 or 3, wherein protrusion parts (31) are separately disposed on two sides of the second metal strip (30).
  5. The spoof surface plasmon polariton transmission line structure (100) according to claim 4, wherein the first metal strip (20) and the third metal strip (50) each have a first end and a second end in the first direction; a first notch (21) is disposed at a second end of the first metal strip (20), the first notch (21) divides the first metal strip (20) into a first branch (22) and a second branch (23), and a width of the first branch (22) and a width of the second branch (23) gradually decrease in the first direction; and a second notch is disposed at a second end of the third metal strip (50), the second notch divides the third metal strip (50) into a third branch and a fourth branch, and a width of the third branch and a width of the fourth branch gradually decrease in the first direction.
  6. The spoof surface plasmon polariton transmission line structure (100) according to claim 4, wherein in the first direction, two side surfaces of the first metal strip (20) gradually approach each other and intersect, and/or two side surfaces of the third metal strip (50) gradually approach each other and intersect.
  7. The spoof surface plasmon polariton transmission line structure (100) according to claim 6, wherein in the first direction, a width of the first metal strip (20) stepwise decreases, a width of the first metal strip (20) linearly decreases, or a side surface of the first metal strip (20) comprises an arc surface; and/or in the first direction, a width of the third metal strip (50) stepwise decreases, a width of the third metal strip linearly decreases, or a side surface of the third metal strip (50) comprises an arc surface.
  8. The spoof surface plasmon polariton transmission line structure (100) according to any one of claims 4 to 7, wherein positions of the plurality of protrusion parts (31) on the two sides of the second metal strip (30) are opposite, or positions of the plurality of protrusion parts (31) on the two sides of the second metal strip (30) are staggered.
  9. The spoof surface plasmon polariton transmission line structure (100) according to any one of claims 1 or 3, wherein the first metal strip (20) and the third metal strip (50) each comprise a first side (24) and a second side (25), the first side (24) is a same side as a protrusion side, and the protrusion side is a side that is of the second metal strip (30) and on which the protrusion parts (31) are disposed: and a second side (25) of the first metal strip (20) gradually inclines toward a first side of the first metal strip (20) and intersects with the second side (25) of the first metal strip (20); and a second side (25) of the third metal strip (50) gradually inclines toward a first side (24) of the third metal strip (50) and intersects with the second side (25) of the third metal strip (50).
  10. The spoof surface plasmon polariton transmission line structure (100) according to any one of claims 1 to 9, wherein a vertical projection of the first metal strip (20) on the second dielectric substrate (40) overlaps the third metal strip (50).
  11. The spoof surface plasmon polariton transmission line structure (100) according to any one of claims 1 to 10, wherein the first metal strip (20) is attached to a surface of the first dielectric substrate (10), or the first metal strip (20) is embedded in a surface of the first dielectric substrate (10).
  12. The spoof surface plasmon polariton transmission line structure (100) according to any one of claims 1, 3 to 11, wherein the second metal strip (30) is attached between the first dielectric substrate (10) and the second dielectric substrate (40), or the second metal strip (30) is embedded in a surface of the first dielectric substrate (10) and/or a surface of the second dielectric substrate (40).
  13. The spoof surface plasmon polariton transmission line structure (100) according to any one of claims 1, 3 to 12, wherein the third metal strip (50) is attached to a surface of the second dielectric substrate (40), or the third metal strip (50) is embedded in a surface of the second dielectric substrate (40).
  14. A circuit board (300), comprising the spoof surface plasmon polariton transmission line structure (100) according to any one of claims 1 to 13.

Description

TECHNICAL FIELD This application relates to the field of microwave technologies, and in particular, to a spoof surface plasmon polariton transmission line structure, a circuit board, and an electronic device. BACKGROUND A spoof surface plasmon polariton (spoof surface plasmon polariton, SSPP for short) is a special electromagnetic wave mode excited on a surface of a specific periodic structure in a frequency band such as a microwave or a terahertz wave. Compared with a naturally existing surface plasmon polariton (surface plasmon polariton, SPP for short), the SSPP has features such as a high binding capability, a low loss, a short operating wavelength, and easy conformal transmission, and therefore attracts wide attention. A periodic metal structure for propagating the SSPP may be referred to as an SSPP transmission line. In recent years, with deepening of research, the SSPP transmission line gradually evolves from a three-dimensional structure into a two-dimensional structure, so that the SSPP transmission line can be processed by using a modem printed circuit board process, thereby promoting a low-cost, scaled, and practical process. The article by Yan Rui Ting et al, IEEE, Microwave and Wireless Components Letters, IEEE Service Center, New York, NY, US, vol. 30, no. 1, 23 December 2019 (2019-12-23), pages 23-26, XP011766351, refers to "A Broadband and High-Efficiency Compact Transition from Microstrip Line to Spoof Surface Plasmon Polaritons". The CN 110 718 731 refers to an artificial surface plasmon transmission line excitation apparatus based on micro-strip line interface. The article by Wang Meng et al, IEEE Transactions on Microwave Theory and Techniques, IEEE, USA, vol. 68, no. 2, 1 February 2020 (2020-02-01), pages 732-740, XP011769865, ISSN: 0018-9480, DOI: 10.1109/TMTT.2019.2952123, refers to a "Supercompact and Ultrawideband Surface Plasmonic Bandpass Filter". The CN 110 311 195 A refers to a micro ultra-wideband artificial surface plasmon bandpass filter. The WO 2020056546 A1 refers to a surface wave excitation device and printed wiring board. To connect the SSPP transmission line to an existing microwave transmission line, currently, a coplanar waveguide is usually used to perform conversion on the microwave transmission line, or a form of a transmission line such as a coaxial waveguide, a microstrip, or a slot line is used. A disadvantage of these transmission structures is that relatively large space needs to be occupied and an overall width is several times a width of the SSPP transmission line. This is not conducive to a compact integrated design of a device. SUMMARY This application provides a spoof surface plasmon polariton transmission line structure, a circuit board, and an electronic device, to reduce a size of the spoof surface plasmon polariton transmission line structure. The invention is set out in the appended set of claims. According to a first aspect, this application provides an SSPP transmission line structure, as defined in claim 1. The SSPP transmission line structure may include a first dielectric substrate, a first metal strip, and a second metal strip. The first dielectric substrate may be configured to support and fasten the first metal strip and the second metal strip. The first metal strip and the second metal strip are respectively disposed on two opposite surfaces of the first dielectric substrate. The first metal strip and the second metal strip separately extend in a first direction. In the first direction, a length of the first metal strip is less than a length of the second metal strip, and a cross-sectional area of the first metal strip gradually decreases until the cross-sectional area of the first metal strip is zero. At least one side of the second metal strip has a plurality of protrusion parts spaced apart, and the periodically disposed protrusion parts have corresponding signal operating frequencies. In a process in which the first metal strip gradually changes and disappears, original signal energy distributed between the first metal strip and the second metal strip is gradually coupled to the second metal strip, so that the second metal strip finally forms an SSPP transmission line having a single-layer metal structure. In the foregoing solution, the SSPP transmission line structure can couple signal energy in a vertical direction by using the first metal strip and the second metal strip that are spatially laminated, to finally concentrate the signal energy onto the second metal strip, so that the second metal strip forms an SSPP transmission line having a single-layer metal structure. Compared with a manner in which energy is coupled in a horizontal direction by using a coplanar waveguide in the conventional technology, in this solution, a width of the SSPP transmission line structure can be reduced, thereby achieving an effect of reducing occupied circuit space. The SSPP transmission line structure further includes a second dielectric substrate and