Surface Plasmon Polaritons Transmission Line Research Articles

A terahertz metamaterial biosensor based on spoof surface plasmon polaritons transmission line for avian influenza virus detection

A highly sensitive terahertz biosensor based on spoof surface plasmon polaritons for avian influenza virus detection is presented in this paper. The sensor utilizes a grating structure to support spoof plasmon modes with high-quality factors, enabling detection at 1.93 THz with a Q-factor of 690. The slow-wave transmission lines (SWTL) are connected to a metamaterial unit cell to achieve strong field confinement and resonance at terahertz frequencies. Various types of the H1N1, H5N2, and H9N2 are considered as material under test which is placed over the sensor. The main elements for controlling the resonance and increasing the Q-factor are the width of the gap and the unit-cell and the parametric studies show that the selected dimensions are optimum for this sensor. The high sensitivity is attributed to the excitation of spoof plasmons that concentrate the terahertz field within micro-scale regions, interacting with minute amounts of analyte. The full-wave method of the finite integrated technique (FIT) as a high-accuracy time domain method is used for the simulation of the proposed structure and it is compared with the finite element method (FEM) for confirming the results. Moreover, the transmission line model (TL) and circuit model (results) are extracted which prove the truth of the full-wave results. The average sensitivity (Savg) of this sensor for material in the range of 1.1 to 1.5 is obtained up to 8 %. This work demonstrates the application of plasmonic metamaterials to terahertz biosensing for virus detection with high sensitivity.

Wearable Full-Textile Spoof Surface Plasmon Polariton Transmission Line for Secured Communication in Wireless Body Area Network

Wearable Full-Textile Spoof Surface Plasmon Polariton Transmission Line for Secured Communication in Wireless Body Area Network

Single-Conductor Spoof Surface Plasmon Polaritons Transmission Line With Bandpass Feature Based on Embedded Cross-Shaped Resonators

In this brief, cross-shaped resonators (CSRs) are integrated in spoof surface plasmon polaritons (SSPPs) unit, and a novel compact single-conductor SSPPs transmission line (TL) with bandpass feature is proposed. In this design, a unit structure based on classical SSPPs structure embedded with a CSR is proposed. To analyze the proposed unit structure, scattering parameters and ABCD-matrix theories are used. After the theoretical analysis, a SSPPs TL with bandpass filtering property is designed. The simulated passband is from 7.9 to 12.2 GHz with a relative bandwidth of 42%. A prototype is fabricated and measured. The measured results are in agreement well with the simulated ones. This proposed structure is attractive and useful for the design of high integrated SSPPs circuits.

Compact effective surface plasmon polariton transmission line with undiminished bandwidth and enhanced field confinement.

In this work, we propose a compact effective surface plasmon polariton (CESPP) transmission line (TL) based on a structural dispersion-induced surface plasmon polaritons (SPPs) mode, which can enhance confinement while ensuring that the working bandwidth is not reduced. The dispersion relation of the CESPPs proposed in this article indicates that the shallower the groove, the stronger the confinement. Furthermore, the CESPPs may facilitate longitudinal miniaturization, since the configuration of the unit cell is simple. The coupling effect between two CESPP TLs has been well studied, revealing that excellent cross talk suppression can be achieved. The measurement results exhibit strong agreement with full-wave simulations, suggesting that the proposed CESPP TL holds significant potential for valuable applications in modern high-speed circuits.

60 GHz Electronically Tunable Leaky-Wave Antenna Based on Annular Surface Plasmon Polariton Media for Continuous Azimuth Scanning

This article proposes a single-layered electronically tunable annular surface plasmon polariton (SPP)-based leaky-wave antenna at 60 GHz for continuous azimuthal beam scanning. Initially, the groundless annular SPP transmission line is designed having specialized feeding mechanism which is operational at 60 GHz under SPP mode. Periodic radiating semicircular patches are incorporated into the vicinity of the TL that form an additional momentum caused to convert the slow-wave SP mode to radiating leaky-mode and placement of extra metallic ground makes the radiated beam unidirectional. Furthermore, implementation of the varactor diodes with imposed suitable switching conditions make the geometry electronically tunable to achieve a continuous complete azimuth coverage. The theoretical predictions, numerical simulations and the experimental validations of the proposed structure show good agreement. The proposed antenna show an overall scanning range of 275°, peak gain of 19.9 dBi with average sidelobe level of −10 dB and minimum cross polar level of −20 dB. Availing the benefits from the low-profile compactness and improved performance, the proposed groundless LWA appears as a promising candidate for integration in 60-GHz mm-wave applications.

Ultra-compact on-chip spoof surface plasmon polariton transmission lines with enhanced field confinements

On-chip transmission lines (TLs) for spoof surface plasmon polariton (SSPPs) have been proved to suppress on-chip channel crosstalk in terahertz band due to their field confinement property. But the contradiction between strong field confinement and miniaturization limits the application of the on-chip SSPP TLs in millimeter and terahertz bands. Here, an ultra-compact on-chip SSPP TL with strong field confinement is proposed using 0.18 μm CMOS technology. The proposed SSPP TL reduces the cutoff frequency down to 435 GHz in a very limited TL width. Broadband feeding without using gradient transition structures is presented to guarantee the compact size. Compared to microstrip and the typical SSPP TLs, outstanding field confinement of the novel on-chip SSPP TL is demonstrated by the electrical-field- intensity distributions. Measured result matches to simulated one well. It is shown that the proposed on-chip SSPP TL possesses the lowest cutoff frequency and the smallest width relative to the cutoff wavelength, compared to the microstrip and the typical SSPP TLs. Thus the ultra-compact on-chip SSPP TL with strong field confinement may be widely used in the future miniaturized monolithic microwave integrated circuits.

An Ultra‐Compact Spoof Surface Plasmon Polariton Transmission Line and Its Signal Integrity Analysis

An ultra‐compact spoof surface plasmon polariton (UCSSPP) transmission line (TL) based on a meander line is proposed, which can achieve almost the same transmission performance as the conventional rectangular‐groove SSPP TL, but the linewidth is greatly reduced by more than 40%. The coupling effect between two UCSSPP TLs in different line arrangements has been well studied, revealing that excellent crosstalk suppression can be achieved when two TLs are arranged back‐to‐back, while strong coupling occurs when they are arranged face‐to‐back or face‐to‐face. The signal integrity of back‐to‐back UCSSPP TLs is analyzed and demonstrated, which shows that the signal integrity can be greatly improved compared with microstrip (MS) TLs. In addition, based on the principle of mode mismatch, MS and UCSSPP TLs are arranged alternately to solve the mutual coupling problem in multi‐line systems. In contrast, benefiting from the strong coupling of face‐to‐face UCSSPP TLs, an ultra‐miniaturized SSPP coupler working at 9 GHz is designed, whose size can be reduced by over 75% compared with conventional MS coupler. The measurement results show good agreement with full‐wave simulations, indicating that the proposed UCSSPP TL has significant advantages in signal integrity and device miniaturization over previously reported SSPP TLs.

T-shaped double-strip spoof surface plasmon polariton transmission lines and application to microwave resonators

A microwave double-strip spoof surface plasmon polariton (DS SSPP) is proposed for high-speed interconnects and high-performance microwave circuits. Based on the dispersion analysis, a T-shaped double-strip structure is designed to provide strong surface- and slow-wave properties from very low to very high frequencies (~ 40 GHz). It allows the tight field confinement and greatly reduces the electromagnetic wave leakage. It exhibits broadband performance with reduced ripples in the insertion loss. It also shows more constant group delay and impedance than counterpart single-strip SSPP. The compact coaxial-to-microstrip-to-DS SSPP transition are designed using gradient grooves. The measurement shows that the DS SSPP lines can exhibit the lower coupling and lower insertion loss than the microstrip lines, so that the former is well-suited for the densely packed high-speed interconnects. The designed DS SSPP is utilized for high quality (Q)-factor microwave ring resonator. The measured unloaded Q-factor is 107.9 at the resonant frequency of 8.7 GHz, which is 1.3 times higher than the microstrip ring resonator. It is found to be caused by the reduction of the radiation loss, according to the loss analysis. The size is also reduced due to the short wavelength, occupying 56.8% of that of the microstrip ring resonator. Therefore, the proposed T-shaped DS SSPP can be also applied for high-performance miniaturized microwave circuits.

High-Efficiency Excitation of Spoof Surface Plasmon Polaritons Through Rectangular Waveguide Using Dipole Antenna

In this communication, a high-efficiency rectangular waveguide-to-spoof surface plasmon polaritons transmission line (SSPPs TL) transition operating within terahertz frequencies is demonstrated. Terahertz signal fed by the rectangular waveguide is first coupled to the planar circuit through the dipole antenna. And then a taper and double-sided SSPPs TL are used to transform the resonant mode in the dipole antenna to the SSPPs mode and achieve impedance and momentum matching. The high transmission performance of the SSPPs TL is obtained by etching a series of periodically corrugated grooves on the metal strip in the top layer and a ground pad connected to the convexity of the rectangular waveguide is employed in the bottom layer. A back-to-back transition prototype was fabricated on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\mu \text{m}$ </tex-math></inline-formula> -thickness quartz substrate and designed for a terahertz device with WR-4.3 standard rectangular waveguide. The measured results show that the insertion loss is lower than 2 dB from 195 to 250 GHz, and the in-band return loss is better than 10 dB. To the best of our knowledge, this work presents the rectangular waveguide-to-SSPPs TL transition using a dipole antenna for the first time, which has potential applications for plasmonic-integrated circuits and systems in the terahertz range.

Embroidered Spoof Surface Plasmon Polariton Transmission Line for Wireless Body Sensor Network

A wearable Spoof Surface Plasmon Polariton Transmission Line (SSPP TL) operating at 2.45 GHz designed for embroidery production and on-body communication is proposed. The SSPP TL supports both even and odd modes launched by near field coupling with a dipole antenna perpendicular and parallel to the TL, respectively. First, the experimental dispersion curves and transmission for the even and odd modes are favourably compared to simulations. Then, experimental transmission for each mode is compared with the Line-Of-Sight (LOS) transmission between two parallel-oriented antennas. At 2.45 GHz, a transmission enhancement of 16 dB is measured for the even mode and it reaches up to 37 dB for the odd mode. A transmission enhancement of 30 dB is also measured at 2.45 GHz between two antennas with orthogonal orientations. Performances of the SSPP TL for Wireless Body Sensor Network are evaluated. Transmission is sustained for the SSPP TL under curvature and right angle bending. Transmission measured when both an arm and a copper plate obstacle between antennas were surrounded by the curved SSPP TL is compared with the obstructed LOS transmission. Measurements show a transmission enhancement up to 22 and 25 dB for the even and odd modes, respectively.

Design of Compact Sub-Terahertz Spoof Surface Plasmon Polariton Transmission Line Based on InP Technology

Design of Compact Sub-Terahertz Spoof Surface Plasmon Polariton Transmission Line Based on InP Technology

Annular Surface Plasmon Polariton-Based Frequency-Scanning Leaky-Wave Antenna for Full Azimuth Coverage

This article presents a single-layered annular surface plasmon polariton (SPP)-based leaky-wave antenna (LWA) for full azimuth beam scanning in 60 GHz applications. The groundless annular SPP transmission line (TL) has a special feeding mechanism that can be operated at 60 GHz in the SPP mode. Periodically radiating circular patches with gradually smaller sizes near the TL create an additional momentum that helps convert the slow wave SP mode into the radiating leaky mode. This results in frequency-dependent continuous beam scanning in the azimuth plane. The theoretical, numerical, and experimental results of the proposed device agree well. The antenna has an overall scanning range of 268°, −10 dB impedance BW of 15.33%, and a peak gain of 19.7 dBi with an average sidelobe level (SLL = −10 dB) and a cross-polar level of −20 dB. Owing to the low-profile compactness and improved performance, the proposed single-layered LWA is a promising candidate for 60 GHz V-band millimeter (mm)-wave applications.

Generation of dual-band rejection filtering function in two frequency bands developed by spoof surface plasmon polaritons

In this paper, we propose the generation of dual-band rejection filters based on the interaction between spoof surface plasmon polaritons transmission line and -type resonator cells. By selecting a suitable value of spacing inside them, the -type resonator cells generate excellent dual-band band rejection filter on combining with spoof SPP transmission line in lower frequency band. A simple parametric calculation based on varying the value of spacing inside -type resonator cells, has been performed for the conversion of dual-band band rejection filter from lower frequency band to higher frequency band. Greater value of spacing results in larger LC coupling which deteriorate filtering performance by leaving us with dual-band rejection filtering function in lower frequency band. By choosing smaller value of spacing converts it into dual-band rejection filtering function in upper frequency band because of significant reduction in LC coupling, and hence leading to much improved broadband filtering performance. In short, the formation of dual-band rejection filter in lower frequency band and its conversion into dual-band rejection filter in upper frequency band can be fully controlled by just adjusting the value of vertical width inside -type resonator cells. The simulation results demonstrate the outstanding performance of the proposed filters and can play a crucial role in developing integrated plasmonic circuits at microwave and terahertz frequencies.

Short-circuited stub-loaded spoof surface plasmon polariton transmission lines with flexibly controllable lower out-of-band rejections.

This Letter proposes an approach to develop a spoof surface plasmon polariton (SSPP) transmission line (TL) by loading short-circuited (SC) shunt stubs. Lower out-of-band rejections can be flexibly controlled without affecting the upper cutoff frequency by independently modifying the stubs. Dispersion analysis of the SSPP unit is realized by theoretical calculation and circuit simulation to predict the upper cutoff frequency of the proposed SSPP TL simultaneously. Also, parametric sweeping of the SC shunt stubs is performed based on circuit simulation to investigate their impacts on the lower and upper out-of-band rejections of the proposed SSPP TL. In addition, electric field distributions of different types of TLs are simulated and compared to study the transmission characteristics of the proposed SSPP TL. The lower cutoff frequency can be flexibly tuned in a wide range, from 1.2 to 2.1 GHz, in the simulations. The measured 3-dB fractional bandwidth is about 128.1%, covering a range from 1.19 to 5.43 GHz. The numerical and experimental results are compatible, which verifies the feasibility of the proposed approach. This approach can offer more convenience and flexibility for controlling the rejections of the SSPP by introducing up to four tuning parameters. More importantly, the proposed SSPP TL avoids using the substrate integrated waveguide (SIW) technique, which shows the potential to decrease the transverse width (0.44λg), especially at lower frequencies (e.g., 1.2 GHz), and to reduce the complexity in designing the high-efficiency transition. This work paves the way for the development of novel SSPP-based microwave devices.

Spoof surface plasmon polariton transmission line with reduced line‐width and enhanced field confinement

This article proposes a compact spoof surface plasmon polaritons (SSPPs) transmission line, by introducing capacitive loading metal strips to manipulate the dispersion characteristics and electromagnetic field confinement. Results validate that, compared with conventional rectangular-grooved SSPP structure, the proposed SSPP transmission line features a line-width reduction up to 53%, and moreover a tighter field confinement, that is, 67% reduction of confinement area. This proposed structure can be further implemented in silicon process with multiple metal layers for on-chip transmission of terahertz signals.

Tunable spoof surface plasmon polariton transmission line based on ferroelectric thick film

Spoof surface plasmon polaritons (SSPPs) provide a high field confinement in the sub-wavelength scale and low transmission loss in the propagation, which are widely used in microwave functional devices. In this paper, we first propose a tunable SSPP transmission line (TL) based on ferroelectric thick film. The ferroelectric thick film associated with the SSPP planar waveguide can provide an electrically tunable transmission phase. Two electric-field-coupled inductive–capacitive (ELC) resonators are added in the configuration to inspire the coupling between ELC resonant modes and SSPPs, enabling the tunable TL to work in the frequency-selective transmission passband. It is demonstrated that the SSPP mode can be designed in higher or lower confinement to modulate the electromagnetic field strength inside the ferroelectric thick film. This property promotes a balanced design between low transmission loss and large phase change for tunable TL. As a result, this study provides an alternative route to design tunable SSPP devices based on ferroelectric thick film, which may open up new applications in tunable microwave devices.

Effective bandpass filtering for spoof surface plasmon polariton transmission lines

Effective spoof surface plasmon polariton (SSPP) bandpass filtering with a simple structure based only on SSPP transmission lines (TLs) is proposed, which has a different working principle from previous versions. SSPP sections are placed beside a main SSPP TL, introducing resonances leading to transmission zeros to the main SSPP TL. By utilizing the SSPP TL sections’ strong dispersion characteristics to merge transmission zeros, a continuous stopband is obtained ensuring good out-of-band rejection and selectivity at the lower band. A domino SSPP working in the microwave band is adopted to demonstrate the idea. A prototype is designed and fabricated to confirm the validity of the proposed method.

A Novel Three-Dimensional Integrated Spoof Surface Plasmon Polaritons Transmission Line

In this paper, a novel three-dimensional integrated spoof surface plasmon polaritons (SSPPs) transmission line (TL) is proposed. The controlled slow surface wave can propagate along unit cells that are planted on a metal strip periodically, which is similar to the typical SSPPs TLs. The dispersion characteristics and high-order modes of the proposed TL are studied. In order to verify the transmission performance of the proposed TL, a two-dimensional (2D) structure is utilized to do like the conversion. We have designed the proposed TL and give the simulated results from 10-25GHz, which show good propagation performance. The ohmic losses and dielectric losses of the proposed TL and typical 2D SSPPs TLs are simulated and compared with the microstrip line, coplanar waveguide. The measured data for the proposed TL indicates that the measured results are close to the simulations. The low-loss and highly integrated characteristics of the proposed TL plays an important role in the microwave and terahertz SSPPs transmission and integrated circuits.

Frequency splitter based on spoof surface plasmon polariton transmission lines

We propose a frequency splitter based on spoof surface plasmon polariton (SSPP) transmission lines (TLs). The device consists of two bent domino SSPP TLs with different geometric parameters, leading to different passbands, forming two frequency band branches. A transition from a rectangular waveguide to the two SSPP TLs is designed for frequency splitting. To achieve efficient transition for both branches in their respective frequency bands, different transition lengths of the two branches and a shifted placement from the center are adopted. Furthermore, for the high frequency band branch, to obtain satisfactory out-of-band rejection below the lower cut-off frequency, an SSPP bandstop structure is introduced by placing SSPP TL sections along the main SSPP TL. A prototype is designed, fabricated, and evaluated. The results prove the feasibility of the proposed SSPP frequency splitter.

A Circularly Polarized Frequency Beam-Scanning Antenna Fed by a Microstrip Spoof SPP Transmission Line

In this letter, a planar frequency beam-scanning antenna with a circularly polarized (CP) radiation property is proposed. The beam scans along the narrow side and in lateral plane of the antenna. The antenna consists of two layers: Eight periodic symmetrical patches are presented on the top layer as radiation elements to generate CP beam, while microstrip spoof surface plasmon polariton transmission line is used as the feeding line, which improves the beam scanning range. The antenna has been fabricated and measured to verify the theory analysis. Measured results indicate that the main beam scans from –5° to +37° in a lateral plane within the operating frequency band from 12 to 16.5 GHz, of which an excellent CP characteristic is also realized. The peak gain of the antenna is about 9.5 dBi over the whole band.