Spoof Surface Plasmon Polaritons Transmission Research Articles

Wideband Millimeter-Wave Antenna With Low Cross Polarization Based on Spoof Surface Plasmon Polaritons

A novel wideband millimeter-wave antenna with low cross polarization based on spoof surface plasmon polaritons (SPPs) is proposed in this letter. Periodic metallic grooves operate as an SPP transmission line with high electromagnetic field confinement. The concept of dielectric tapered rod antenna is employed to design an SPP rod antenna with linear-tapered groove depth, converting the confined energy to radiation mode. Meanwhile, the tapered structure only affects the $E_{z}$ component on the transverse plane, and thus it can achieve low cross polarization. This prototype is fabricated by three-dimensional printing technique and surface metallization process. The radiating length of the linear-tapered SPP antenna is 29.2 mm, and the measured | S 11| is below −15.6 dB from 50 to 75 GHz. Experimental results show that the linear-tapered antenna can achieve an average gain of 14.95 dBi with ±1.45 dBi variation and better than −25.6 dB cross-polarization level for E -plane radiation.

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.

Circularly Polarized Antenna With Spoof Surface Plasmon Polaritons Transmission Lines

A circularly polarized (CP) antenna with spoof surface plasmon polaritons (SSPPs) transmission lines is proposed in this letter. The feeding network is based on the SSPP waveguides and parallel transmission lines. According to the dispersion characteristics of an SSPP unit and a parallel transmission line unit, a phase difference can be tuned by changing the groove depth of the SSPP unit. As a result, a feeding network is designed with SSPP waveguides to realize CP radiation. In addition, two pairs of tightly coupled dipoles are introduced as a compact radiator. The radiator and feeding network are printed on both sides of an FR4 substrate with dimensions of 85 mm × 85 mm $(0.425{{\boldsymbol{\lambda }}_0} \times 0.425{{\boldsymbol{\lambda }}_0})$ . A radiation structure is backed by a metallic ground to provide a unidirectional radiation pattern. To validate this design, the proposed antenna is simulated and measured. Measured results show that a wide impedance bandwidth of 49.4% from 1.19 to 1.97 GHz with a return loss of higher than 10 dB and a 3 dB axial-ratio bandwidth of 18.8% from 1.45 to 1.75 GHz is achieved.

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.

A novel spoof surface plasmon polariton structure to reach ultra-strong field confinements

Ultrathin corrugated metallic structures have been proved to support spoof surface plasmon polariton (SPP) modes on two-dimension (2D) planar microwave circuits. However, to provide stronger field confinement, larger width of strip is required to load deeper grooves, which is cumbersome in modern large-scale integrated circuits and chips. In this work, a new spoof SPP transmission line (TL) with zigzag grooves is proposed. This new structure can achieve stronger field confinement compared to conventional one with the same strip width. In other words, the proposed spoof SPP TL behaves equivalently to a conventional one with much larger size. Dispersion analysis theoretically indicates the negative correlation between the ability of field confinement and cutoff frequencies of spoof SPP TLs. Numerical simulations indicate that the cutoff frequency of the proposed TL is lower than the conventional one and can be easily modified with the fixed size. Furthermore, two samples of the new and conventional spoof SPP TLs are fabricated for experimental demonstration. Measured S-parameters and field distributions verify the ultra-strong ability of field confinement of the proposed spoof SPP TL. Hence, this novel spoof SPP structure with ultra-strong field confinement may find wide applications in microwave and terahertz engineering.

Shielding Spoof Surface Plasmon Polariton Transmission Lines Using Dielectric Box

Local leaky electromagnetic (EM) waves can impact the performance of the whole systems obviously due to the compact arrangement of integrated systems, including circuits based on spoof surface plasmon polaritons (SPPs). However, the widely used metallic shielding box in the traditional EM compatibility technology will affect the propagation of SPP modes dramatically. In this letter, we propose the double-layer dielectric shielding box made by materials with high permittivity, which can reduce leaky EM waves without affecting the transmission efficiency of SPP transmission lines (TLs). We demonstrate in simulation and experiment that the dielectric-shielded SPP TLs perform better in propagation than metallic-shielded SPP TLs. The effectiveness of the dielectric shielding boxes is investigated as well, and the calculated and measured results indicate that the double-layer dielectric structure can produce outstanding shielding effectiveness.

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.

High‐efficiency circularly polarised leaky‐wave antenna fed by spoof surface plasmon polaritons

A circularly polarised (CP) periodic leaky-wave antenna excited by spoof surface plasmon polaritons (SPPs) is proposed. It is based on an SPP transmission line loaded by periodic rectangular patches on both sides with 90° phase shift, which converts the SPPs mode to CP propagating waves in the air. Due to the dispersion nature of SPPs waveguide, this leakywave antenna exhibits a beam scanning feature. Both simulated and measured results demonstrate that the proposed antenna has an impedance bandwidth of 33% for |S 11 | <; - 10dB and a 3 dB axial ratio bandwidth of 15%. The average gain and radiation efficiency are about 10 dBic and 87% from 5.5 to 6.4 GHz, respectively.

Tunneling of spoof surface plasmon polaritons through magnetoinductive metamaterial channels

In this work, we realize tunneling propagation through spoof surface plasmon polariton transmission lines loaded with magnetoinductive metamaterial channels above a high cutoff frequency. Magnetoinductive metamaterial channels consist of split-ring resonators, and two different structures are proposed. Samples are fabricated, and both measurements and simulations indicate a near-perfect tunneling propagation around 17 GHz. The proposed methodology could be exploited as a powerful platform for investigating tunneling surface plasmons from radio frequencies to optical frequencies.

A novel power divider with ultra-wideband harmonics suppression based on double-sided parallel spoof surface plasmon polaritons transmission line

A novel power divider with ultra-wideband harmonics suppression based on double-sided parallel spoof surface plasmon polaritons transmission line

An ultra-compact rejection filter based on spoof surface plasmon polaritons

In this paper, we propose a scheme to construct a new type of ultra-compact rejection filter by loading split-ring resonators (SRRs) on the transmission line of spoof surface plasmon polaritons (SPPs). From the dispersion analysis of the spoof SPP transmission line with and without the SRR loading, we clearly reveal the mechanism of the rejection characteristic for this compact filter. Meanwhile, we fabricate two spoof SPPs waveguides loaded with different amounts of metamaterials particles, and experimentally test them using an Agilent Vector Network Analyzer (VNA) and a homemade near-field scanning system. Both the simulated and measured results agree well with our theoretical analysis and demonstrate the excellent filtering characteristics of our design. The isolation of both filters can be less than −20 dB, and even reach −40 dB at rejection frequencies. The proposed rejection and stop-band filters show important potentials to develop integrated plasmonic functional devices and circuits at microwave and terahertz frequencies.

Reduction of radiation loss at small-radius bend using spoof surface plasmon polariton transmission line

Spoof surface plasmon polariton (SPP) has been realized at low frequencies through corrugated metallic structures. As two-dimensional application, the ultrathin SPP transmission lines (TLs) have been proposed with great potentials for microwave compact circuits due to the strong field confinement and enhancement, as well as controllable dispersive properties. In this paper, we examine the radiation loss at small-radius bend, which may cause severe crosstalk in highly-integrated circuits or systems, for the SPP TLs. We theoretically analyze that the SPP TL has essential merit of low radiation loss, and show better performance of SPP TL than the conventional microstrip line through numerical simulations and experiments. Both simulated and measured results demonstrate that the new type of transmission line can efficiently suppress the radiation loss at small-radius bend, and hence reduce the crosstalk in circuits and systems.

A Wide-Angle and Circularly Polarized Beam-Scanning Antenna Based on Microstrip Spoof Surface Plasmon Polariton Transmission Line

In this letter, a wide-angle beam-scanning antenna with circular polarization (CP) characteristic is proposed. The antenna consists of two layers. Microstrip spoof surface plasmon polariton (SPP) is introduced on the bottom layer as a slow-wave feeding line. A series of circular patches are placed on the top layer as radiating elements. Simulated and measured results indicate that beam-scanning angle of the proposed antenna is improved and CP beam-scanning ability is obtained by introducing perturbation on the radiating elements. In the operating band of 11–15 GHz, measured scanning angle of the fabricated antenna is from –32° to +34°. The antenna axial ratio (AR) is below 3 dB at the corresponding beam direction, and gain is above 12.8 dBi over the whole band. It has potential applications in radar and wireless communication systems for simple structure, low-cost fabrication, wide beam-steering, and CP properties.

Smaller-loss planar SPP transmission line than conventional microstrip in microwave frequencies.

Transmission line is a basic component in all passive devices, integrated circuits, and systems. Microstrip is the most popular transmission line in the microwave and millimeter-wave frequencies, and has been widely used in current electronic devices, circuits, and systems. One of the important issues to be solved in such applications is the relatively large transmission loss of microstrip. Here, we propose a method to reduce the loss of microwave transmission line based on the designable wavenumber of spoof surface plasmon polaritons (SPPs). Using this characteristic, we analyze and experimentally demonstrate the low-loss feature of the SPP transmission line through the perturbation method and S-parameter measurements, respectively. Both simulation and experimental results show that the SPP transmission line has much smaller transmission loss than traditional microstrip with the same size in the microwave frequencies. Hence, the spoof SPP transmission line may make a big step forward in the low-loss circuits and systems.

Compact Feeding Network for Array Radiations of Spoof Surface Plasmon Polaritons.

We propose a splitter feeding network for array radiations of spoof surface plasmon polaritons (SPPs), which are guided by ultrathin corrugated metallic strips. Based on the coupled mode theory, SPP fields along a single waveguide in a certain frequency range can be readily coupled into two adjacent branch waveguides with the same propagation constants. We propose to load U-shaped particles anti-symmetrically at the ends of such two branch waveguides, showing a high integration degree of the feeding network. By controlling linear phase modulations produced by the U-shaped particle chain, we demonstrate theoretically and experimentally that the SPP fields based on bound modes can be efficiently radiated to far fields in broadside direction. The proposed method shows that the symmetry of electromagnetic field modes can be exploited to the SPP transmission network, providing potential solutions to compact power dividers and combiners for microwave and optical devices and systems.