A Broadband Fundamental Mode Negative Group Rate SSPP Unit Structure

Abstract

A broadband SSPP (Surface Plasmon Polariton) unit structure with negative group velocity of the fundamental mode is disclosed, belonging to the field of microwave technology. Based on artificial surface plasmon polariton (SSPP) generating a base film negative group velocity, a broadband SSPP unit structure with negative group velocity of the fundamental mode is achieved. The structure includes a dielectric substrate and an etched metal pattern on one side of the substrate. The metal pattern includes straight conductor strips and a folded spiral ring assembly on one side, formed by iterating the spiral ring basic unit structure four times. The straight conductor strips are used to achieve efficient forward transmission of SSPP. The spiral ring basic unit consists of eight rectangular metal strips bent into semi-rings, with the semi-rings symmetrically connected to form a complete spiral ring basic unit. The folded spiral ring assembly is used to achieve the negative group velocity effect of SSPP. It features wide bandwidth, negative group velocity, and high integration. It has broad application prospects in 5G communication, imaging systems, vehicle radar communication, and satellite navigation.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology, specifically relating to an SSPP unit structure with broadband fundamental mode negative group velocity. Background Technology

[0002] Surface plasmon polaritons (SPPs) are a physical phenomenon in optics: when free-space light shines on a metal surface, the free electrons in the metal oscillate, and the electromagnetic field is confined at the boundary between free space and the metal surface, decaying exponentially in the direction perpendicular to the interface. Artificial surface plasmon polaritons (SSPPs) are electromagnetic metamaterials with negative permittivity or negative permeability in the microwave and millimeter-wave bands, offering the possibility of realizing surface plasmon polaritons at low frequencies. This new plasmonic metamaterial shares similar dispersion characteristics and field localization capabilities with optical SPPs, exhibiting low-pass characteristics and near-field enhancement, surface confinement, and deep subwavelength characteristics near the cutoff frequency. The electromagnetic properties of artificial surface plasmon polaritons can be easily controlled by changing their geometry.

[0003] Group velocity is typically used to describe the speed of envelope movement; therefore, under normal dispersion conditions, the group velocity is always positive. However, under anomalous dispersion, the group velocity can not only exceed the speed of light (i.e., superluminal), but can even be negative (negative group velocity, NGV). Negative group velocity or superluminal phenomena mainly occur under anomalous dispersion and evanescent wave electromagnetic environments, and their theoretical basis comes from the leading potential in the general solution of the Maxwell-D'Alembert equation. To achieve dispersion compensation based on negative group velocity, anomalous dispersion must first be generated. Utilizing this characteristic of negative group velocity has significant advantages in meeting the requirements of broadband high-speed wireless communication and the low latency of current fifth-generation mobile communication. Furthermore, it has broad application prospects in many fields such as improving microwave device performance, achieving signal integrity transmission, and improving array antenna performance, thus possessing significant research significance and application value. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems mentioned in the background section by providing an SSPP cell structure with broadband fundamental mode negative group speed.

[0005] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0006] An SSPP cell structure with broadband fundamental mode negative group velocity includes a high-frequency dielectric substrate. A metal pattern of a straight conductor strip and a folded spiral ring on one side of the substrate is etched on the surface of the high-frequency dielectric substrate to form the SSPP cell structure. The metal pattern includes a straight conductor strip and a folded spiral ring assembly on one side. The bottom of the folded spiral ring assembly is connected to the metal straight conductor strip. The folded spiral ring assembly is formed by iterating the spiral ring basic cell structure four times.

[0007] The straight conductor strip is used to achieve efficient forward transmission of SSPP.

[0008] The basic unit of the spiral ring is composed of 8 rectangular metal strips bent into a semi-ring, and the semi-rings are symmetrically connected to form a complete basic unit of the spiral ring.

[0009] The SSPP unit structure is composed of four basic spiral ring units.

[0010] The high-frequency dielectric substrate can be made of FR4 high-frequency dielectric substrate with a relative permittivity εr = 2.2.

[0011] The length of the straight conductor strip is equal to the width of the dielectric substrate.

[0012] The folded spiral ring assembly is used to achieve the negative group velocity effect of SSPP.

[0013] Compared with existing technologies, this unit structure has the following advantages:

[0014] Combining the characteristics of SSPP and negative group velocity, this invention proposes an SSPP unit structure with broadband fundamental mode negative group velocity. This invention uses a bottom straight conductor strip structure, and the basic unit structure of the assembly consists of two symmetrical semi-rings, iterated multiple times to form the SSPP unit structure. The negative group velocity of SSPP is achieved through a spiral ring assembly, which, compared with previous design methods, can achieve a negative group velocity with a larger bandwidth and significantly simplifies the design process compared to existing technologies. Its negative delay effect can be applied to microwave circuits. This SSPP unit structure can be used to achieve broadband fundamental mode negative group velocity. Based on negative group delay compensation, the overall delay after equalization can be reduced over a wide frequency band, which is of great significance for communication systems such as 5G that require extremely low latency. Based on the negative group delay of SSPP, it also helps to realize highly integrated circuits. The fundamental mode of this structure exhibits anomalous dispersion in the 2.28–3.5 GHz frequency band after reaching the cutoff frequency, with a negative group velocity and a large bandwidth. Attached Figure Description

[0015] Figure 1 This is a three-dimensional schematic diagram of the structural composition of an embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of the dimensions of the SSPP structural unit according to an embodiment of the present invention.

[0017] Figure 3 This is a schematic diagram of the dimensions and structure of a single folded spiral ring according to an embodiment of the present invention.

[0018] Figure 4 The simulation results of the dispersion curves for the three SSPP modes in this embodiment of the invention are shown.

[0019] Figure 5 The simulation results are for the normalized group velocity of the fundamental mode of the unit structure in an embodiment of the present invention.

[0020] Figure 6 The simulation results show the transmission coefficient and reflection coefficient of the unit structure in this embodiment of the invention.

[0021] Figure 7 The simulation results are for the phase of the unit structure S21 in this embodiment of the invention.

[0022] Figure 8 These are the transmission group delay parameters for the unit structure in this embodiment of the invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] See Figures 1-3 The SSPP unit structure with broadband fundamental mode negative group velocity described in this embodiment of the invention includes: a high-frequency dielectric substrate 1, a straight conductor strip 2, and a folded spiral ring assembly 3; the straight conductor strip 2 and the folded spiral ring assembly 3 are metal pattern layers etched on one side of the dielectric substrate; the folded spiral ring assembly 3 is formed by iterating the spiral ring basic unit structure four times.

[0025] The high-frequency dielectric substrate 1 uses F4B high-frequency dielectric with a relative permittivity of 2.2, a length of Ls = 15 mm, a width of P = 2.2 mm, and a thickness of 0.8 mm. The straight conductor strip 2 has a length equal to the width of the dielectric substrate and a width of W = 1 mm. The bottom of the folded spiral assembly 3 is connected to the metal straight conductor strip 2, and the distance D = 1.98 mm from the bottom right side of the dielectric substrate. Both the straight conductor strip and the spiral ring basic unit are composed of a metal layer with a thickness of 0.035 mm.

[0026] The basic unit of the spiral ring consists of two symmetrical semi-rings, which are the same size and connected end to end. Each semi-ring is composed of eight rectangular metal strips joined at 90° angles. The width of each rectangular metal strip in a semi-ring is W1 = 0.15mm, and the lengths are L1 = 1.5mm, L2 = 0.5mm, L3 = 1.2mm, L4 = 0.5mm, L5 = 0.5mm, L6 = 0.6mm, and L7 = 1.2mm, respectively.

[0027] See Figure 4 The dispersion curves of the three modes of the SSPP unit structure in the embodiment were simulated and analyzed, where k is the phase constant and p is the period of the SSPP unit structure. The dispersion curves of the fundamental mode and the two higher-order modes of the SSPP unit structure obtained by the simulation all have a cutoff frequency extreme value. After reaching the cutoff frequency, the dispersion curves show a significant downward trend. To the right of the cutoff frequency, the lower the frequency, the smaller the phase velocity, and there is an anomalous dispersion frequency band of 2.28 to 3.5 GHz with a large bandwidth and a negative group velocity.

[0028] See Figure 5 The normalized group velocity of the fundamental mode of the unit structure in this embodiment was simulated and analyzed. The frequency band of the fundamental mode coincides with the anomalous dispersion band in the dispersion curve.

[0029] See Figure 6 The transmission coefficient and reflection coefficient of the unit structure based on the waveguide transmission method were simulated and analyzed in this embodiment. The simulation results show that the reflection coefficient reaches a maximum value of -5.88dB at a frequency of 2.8GHz, and the corresponding transmission coefficient is -6.6dB at this point. This indicates that the energy flow transmission is limited near 2.8GHz, which is consistent with the anomalous dispersion frequency band in the dispersion curve.

[0030] See Figure 7 A simulation analysis of the transmission phase of the unit structure based on the waveguide transmission method was performed on this embodiment. The simulation results show that the phase of S21 is negative group velocity in the 2.28-3.5GHz band. The leading phase cancels the phase lag effect under normal dispersion, thereby reducing the overall lag effect.

[0031] See Figure 8 The transmission group delay of the SSPP unit structure in this embodiment was simulated and analyzed. The simulation results show that the group delay is less than zero in the range of 2 to 3.5 GHz, that is, anomalous dispersion generates a leading wave.

[0032] This invention features wide bandwidth, negative group velocity, and high integration. The ultra-wideband filter of this invention has broad application prospects and enormous market value in fields such as 5G communication, imaging systems, vehicle-mounted radar communication, and satellite navigation.

[0033] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the described embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. An SSPP cell structure with broadband fundamental mode negative group rate, characterized in that... The system includes a high-frequency dielectric substrate, on which a metal pattern is etched to form an SSPP unit structure. The metal pattern includes a straight conductor strip and a folded spiral ring assembly on one side. The bottom of the folded spiral ring assembly is connected to the straight metal conductor strip. The folded spiral ring assembly is formed by iterating the spiral ring basic unit structure four times. The spiral ring basic unit consists of two half-rings of the same size, connected end to end. Each half-ring is formed by connecting eight rectangular metal strips. The folded spiral ring assembly is used to realize the negative group velocity effect of SSPP.

2. The SSPP cell structure with broadband fundamental mode negative group rate as described in claim 1, characterized in that... The straight conductor strip is used to achieve efficient forward transmission of SSPP.

3. The SSPP cell structure with broadband fundamental mode negative group rate as described in claim 1, characterized in that... The high-frequency dielectric substrate is made of FR4 high-frequency dielectric substrate with a relative permittivity εr = 2.

2.

4. The SSPP cell structure with broadband fundamental mode negative group rate as described in claim 1, characterized in that... The length of the straight conductor strip is equal to the width of the dielectric substrate.

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