Spoof Surface Plasmon Polaritons Transmission Line Research Articles

A compact wideband antenna with high gain based on spoof surface plasmon polaritons

In this paper, a novel wideband antenna with a simple structure and low profile based on spoof surface plasmon polaritons (SSPPs) is proposed. The structure consists of periodically modulated corrugated metal strips as transmission lines, a CPW feed, and a ground metal plate as an antenna reflector. The SSPP transmission line is used to convert quasi-TEM to SSPP mode and achieve optimal impedance matching. The prototype of the end-fire antenna has been designed and fabricated. The simulation results show that this antenna can achieve a gain of 10.19 dB, a bandwidth of 146%, and an efficiency of 90% in a wide operating band from 7 to 45 GHz. The proposed design illustrates great potential that includes high efficiency, good directivity, high gain, wide bandwidth, and easy manufacturing.

A low-profile high-isolation endfire MIMO antenna based on spoof surface plasmon polaritons for X-band applications

This work proposes a three-port, low-profile, coplanar endfire multiple-input-multiple-output (MIMO) antenna based on spoof surface plasmon polaritons (SSPPs). The proposed antenna comprises a coplanar waveguide (CPW)-fed SSPPs transmission line (TL). A transition to transform the CPW quasi-TEM mode to the SSPPs mode. The radiator section with asymmetric discontinuities converts the bounded SSPPs waves into radiating waves. The proposed MIMO antenna exploits the inherent feature of high isolation in the SSPPs TL due to its strong field confinement competency. Wider beamwidths for ample azimuth and elevation coverage with a stable pattern in the endfire direction are achieved in the 9.52–11.23 GHz operating band. In the operating band, the MIMO antenna has an average realized gain of 6 dBi. Mainly, it has high isolation below -35 dB (measured) in the operating range, a maximum envelope correlation coefficient (ECC) of 1.5 × 10−3, and a total active reflection coefficient (TARC) value below 0.3. The measured results are closely matched with the simulated ones in terms of S-parameters, radiation pattern, ECC, TARC, and CCL.

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.

Spoof Surface Plasmon Polariton Based Frequency Scanning Antennas

Frequency scanning antennas realized by loading the radiating elements on both sides of the microstrip, asymmetrically corrugated spoof surface plasmon polariton (SSPP), and symmetrically corrugated SSPP transmission lines are discussed in this paper. Both traveling and standing wave antennas are considered and performance in terms of S-parameters, radiation pattern, scan range, and gain is reported. Additionally, the crosstalk between two transmission lines is observed in all cases. Based on the analysis, it was proved that the crosstalk was minimum in the case of symmetrically corrugated SSPP transmission lines. The proven advantages of the SSPP lines find better signal integrity, high gain, and wide-angle scan frequency scanning antennas.

Wideband Vertically Polarized Planar Endfire Antenna Based on Spoof Surface Plasmon Polaritons

A novel wideband vertically polarized planar end-fire antenna based on the first and the second high-order modes of Spoof Surface Plasmon Polaritons (SSPPs) is proposed in this letter. A double-sided SSPP transmission line (TL) is used to produce vertically polarized radiation. By replacing the uniform stub in the conventional SSPP cells with a step-impedance-resonator (SIR) shaped stub, the bandgap between the first and the second high-order modes is eliminated. The double-sided SIR-shaped SSPP cells are tilted to make the maximum radiation point in the end-fire direction. Dielectric covers perforated with air vias are added to the top and bottom surfaces of the SSPP TL to generate end-fire radiation and enhance antenna gain. A grounded coplanar waveguide to double-sided parallel-strip line transition is designed to feed the radiator. A prototype of the proposed antenna has been fabricated and measured. The proposed antenna achieves a fractional bandwidth of 91.6% from 12.9 GHz to 34.6 GHz and a peak gain of 17.3 dBi.

Ultra-Thin Flexible Uniplanar Antenna Based on SSPP for B5G Radio Stripe Network

In this letter, a flexible and ultra-thin uniplanar endfire antenna employing spoof surface plasmon polariton (SSPP) is proposed. The single-metal layered groundless structure is an inherent advantage of the SSPP. At the SSPP transmission line's end, a metallic strip is added asymmetrically for wideband radiation, resulting in an observed tilting of the main lobe in the azimuthal plane. Three C-shaped directors are used to enhance the directivity. The proposed antenna is fabricated and measured over flat and curved surfaces of brick wall and wood with two different radii. The proposed antenna has a low profile of 0.0017λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and a small volume of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.0058{\lambda }_0^3$</tex-math></inline-formula> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at the center frequency of the operating bandwidth. The antenna has an impedance bandwidth of 33.7% with a peak gain of 8.5 dBi. Measurements indicate no significant degradation in the proposed antenna's performance in different scenarios. Due to features like flexibility, ultrathin profile, very low volume, tilted beam with high gain, and wideband operation, the proposed antenna is highly suitable for beyond fifth-generation (B5G) radio stripe applications.

Triple-Beam Leaky-Wave Antenna Based on Spoof Surface Plasmon Polaritons With Hybrid Periodic Modulation

In this letter, a triple-beam leaky wave antenna (LWA) based on modulated spoof surface plasmon polaritons (SSPPs) transmission line (TL) with hybrid period is presented. The one side of SSPPs TL is modulated sinusoidally with period of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> 1, and another side is modulated with composite period of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> 2 and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> 3. The analysis of dispersion curves indicates that the modulated periods at each side of the TL is independent and hence the radiation beams can be controlled independently by adjusting the modulation periods. In this design, the LWA radiates three beams simultaneously. From 7.8 to 9.1GHz, the gain difference of beams is lower than 3-dB. which have cover range from 49º to 149º. To validate the performance of the designed LWA, a prototype is fabricated and measured. The measured results are in good agreement with the simulated ones.

A novel and ultra-compact plasmonic filter with a fully controlled rejection band

In this article, we propose a novel approach to develop an ultra-compact spoof surface plasmon polariton (SSPP) band-rejection filter by loading T-shaped grooves on the SSPP transmission line (TL). This scheme is based on the interaction between two types of grooves, i.e. rectangular grooves of the SSPP TL and T-shaped grooves. This form of interaction has never been addressed before in order to achieve a highly efficient SSPP band-rejection filter. The working principle of this band-rejection filter is clearly revealed via investigation of the dispersion behavior of the SSPP TL in the presence and absence of T-shaped groove loading. Meanwhile, we simulate an SSPP TL loaded with T-shaped grooves. As proof of concept, we fabricate the filter in the microwave regime and perform an experiment which characterizes its functionality. The simulated and experimental results confirm the excellent filtering phenomena exhibited by our structure. The isolation of the filter can be less than −15 dB at rejection frequencies with excellent transmission efficiency in both passbands, before and after the rejection band. Furthermore, simulated near-electric-field results are also presented to demonstrate the authenticity of the filter. When the question of generating a highly efficient SSPP band-rejection filter arises, the proposed method facilitates us with T-shaped grooves, which are declared as an excellent alternative to metamaterial particles in this regard. The proposed band-rejection filter based on SSPPs demonstrates an outstanding capability to take part in the progress and the advancement of integrated plasmonic structures and systems at microwave frequencies.

A novel beam-steering device based on spoof surface plasmon polaritons

In this paper, an ultra-compact T-shaped component is proposed in order to achieve a spoof surface plasmon polariton (SSPPs) dual-functional device with beam steering and multiple band-rejection filtering functions. The newly introduced T-shaped component provides an excellent multiple band-rejection filter response when combined with the SSPP transmission line (TL), and can be regarded as an excellent alternative to metamaterial particles to conceive multi-band rejection of spoof SPP waves. Multi-band rejection filters are designed by introducing different intervals among the symmetric T-shaped components. Furthermore, we designed a compact SSPP beam-steering device integrated with a multiple band-rejection filtering function. The multiple band-rejection integrated beam-steering device can also be realized by incorporating different intervals among the T-shaped components, as mentioned in the case of linear filters. Integration of the SSPP beam-steering device and band-rejection filter offers compact areas and controllable passband features, which broadens the application range of SSPPs. In conclusion, the proposed T-shaped component is an outstanding addition toward the advancement of highly efficient ultra-compact dual-functional plasmonic devices.

PSO-Algorithm-Assisted Design of Compact SSPP Transmission Line

This letter proposes a compact spoof surface plasmon polariton (SSPP) transmission line (TL) structure. The particle swarm optimization (PSO) algorithm is utilized to numerically optimize the traditional rectangular groove SSPP structure. The SSPP unit cell is pixelated into 23 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 9 pixels with a resolution of 0.2 mm, and the asymptotic frequency is reduced to 5.4 GHz through optimization. The developed SSPP TL exhibits a compact structure, and its electrical dimension is only about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.842\lambda _{g} \times 0.28\lambda _{g}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{g}$ </tex-math></inline-formula> is the wavelength of the cutoff frequency. A prototype of the developed SSPP TL is fabricated and tested, and the experimental result agrees well with the simulated one. The proposed optimization approach is applicable to both single- and dual-conductor SSPP structures. The results are of great significance to the miniaturization of components and circuits based on SSPP.

A Wideband Transition from Microstrip Line to Microstrip Spoof Surface Plasmon Polariton Line for Microwave/Millimeter-Wave Applications

In this article, a wideband transition from a microstrip transmission line to a microstrip spoof surface plasmon polariton (SSPP) transmission line is reported. The proposed transition is realized to achieve better performance starting from low frequencies up to 40 GHz. The proposed shape of the unit cell is taken in such a manner that the momentum, impedance, and polarization of the microstrip line can be matched with that of the SSPP transmission line. The wide operating band of the transition can be achieved by perturbing only the shape of the unit cell. Extra care is taken in choosing the shape of the unit cell so that the fabrication of the circuit becomes easier, especially at millimeter-wave frequencies. The proposed transition has a good transition-occupation ratio and transmission efficiency. The achieved transition-occupation ratio and transition efficiency for all three designed cases are excellent, and it is 34.18%, 44%, and 39% for p = 1 mm, 2 mm, and 3 mm, respectively. It is a potential candidate for realizing millimeter-wave antennas and devices due to its attractive properties, such as compact layout, low fabrication cost, ease of fabrication even at millimeter-wave frequencies, and good operational characteristics.

Ultra-Wideband Planar End-Fire Antenna Based on High-Order Modes of Spoof Surface Plasmon Polaritons

In this article, an ultrawideband planar end-fire antenna based on high-order modes of spoof surface plasmon polaritons (SSPPs) is proposed. First, a quad-band end-fire antenna is designed by using the first four high-order SSPP modes. An SSPP transmission line with gradually decreasing groove depth is used to radiate the high-order modes. Moreover, to improve the gain and sidelobe level at high frequencies, the SSPP units in the quad-band antenna are tilted. Then, an SSPP structure consisting of a periodic array of metal strips is proposed. By adding two arrays of tilted I-shaped strip resonators to the quad-band antenna, the first two bandgaps are eliminated. The proposed antenna achieves a fractional bandwidth of 140.8% from 6.9 to 39.7 GHz. Minimum and maximum measured gains of 6.4 and 15.2 dBi are achieved at 6.9 and 38 GHz, respectively. The proposed antenna has a great potential for applications in imaging and wireless communication.

Measurement Method for the Dispersion Curves of a Spoof SPP Transmission Line Using a Single Sample

Research works on spoof surface plasmon polariton (SPP) transmission lines (TLs) have been carried out toward the goal of achieving flexible control of dispersion. The existing measurement methods for the dispersion of the spoof SPPs require two SPP TL samples with different numbers of units and transition structures, which makes the process more difficult and expensive. This work proposes a new approach for measuring the dispersion curve of a spoof SPP TL by using experimental near-field data. A mathematical model is presented to describe the relation between the wavenumber <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> and the near-field data by considering the presence of reflected waves. The high efficiency and accuracy of this method are verified by the good agreement obtained between the measured dispersion curve and the eigenmode simulation result for a typical spoof SPP TL. Hence, the proposed method makes it possible to measure the dispersion curve of a spoof SPP TL based on a single sample, providing significant progress toward decreasing testing error and cost.

Bendable transmission line and amplifier of spoof surface plasmon polaritons at microwave frequencies.

A bendable transmission line (TL) of spoof surface plasmon polaritons (SSPPs) is presented, which can maintain good transmission performance despite of the deformation caused by bending. Such a TL consists of flexible dielectric substrate and ultrathin metallic strip with zigzag decorations that are designed to support the propagation of SSPPs with strong field confinement and low radiation loss. Furthermore, the proposed SSPP TL is used to excite an amplifier chip efficiently, reaching high and stable gains with nearly no degradation of amplification in the bending states. Numerical and experimental results are demonstrated to verify the bendable merits of both passive TL and active amplifier from 12 GHz to 18 GHz. The flexible and stable characteristics of this design may find utility in novel applications like wearable electronics and conformal plasmonic circuits in the microwave frequencies.

Wideband high‐gain planar end‐fire antenna based on spoof surface plasmon polaritons and loaded with I‐shaped resonators

A wideband high-gain millimeter-wave planar end-fire antenna based on spoof surface plasmon polaritons (SSPPs) is proposed. A symmetric SSPP transmission line is used to adjust the phase of the wave on the outer edges. By loading metal strips with I-shaped resonators, a transmission line which exhibits a SSPP-like behavior is formed. It is used to extend the lower limit of the working bandwidth from 34.75 to 24 GHz. The measured working bandwidth covers the frequency band from 24 to 40 GHz, which includes the whole Ka band, and the n257, n258, n260 bands in 5G communication. And the measured peak gain is 18 dBi. Therefore, the proposed antenna is suitable for millimeter-wave communication applications.

Reconfigurable dual‐beam leaky‐wave antenna based on spoof surface plasmon polariton

AbstractIn this paper, a reconfigurable leaky‐wave antenna (LWA) based on spoof surface plasmon polariton (SSPP) transmission line (TL) is proposed. Patches placed nearby the SSPP TL effectively convey the energy from the transmission mode to the radiation mode. SSPP units are loaded with variable capacitors, which enable the antenna to achieve free switching between fixed‐beam and beam scanning. When the antenna is working on a fixed beam in broadside, operating at 7.6–8.6 GHz, and the beam deviation is within ±1° by adjusting the capacitors. When the proposed antenna operates at fixed frequencies, up to 28° scanning range can be obtained with a stable gain. The antenna is fabricated and proved effective in the experiment. The proposed SSPP LWA provides a solution to narrow‐band and point‐to‐point communication systems.

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.

Reconfigurable leaky wave antenna with low sidelobe based on spoof surface plasmon polariton

A low sidelobe leaky wave antenna (LWA) based on Spoof Surface Plasmon Polariton (SSPP) with switchable right/left-handed circular polarization (CP) and linear polarization (LP) radiation function by controlling the status of two PIN diodes is proposed. Two symmetrical SSPP transmission lines (TLs) are connected through two PIN diodes, and the ON–OFF of diodes constitute three different transmission modes. Two rows of the tapered arranged elliptical patches are loaded periodically around the TL to break the original stable transmission structure for radiation, and suppress the antenna sidelobe levels to less than −10 dB. After experimental verification, the reconfigurable antenna can reach three functionalities: (1) Mode 1: 22°right-handed CP beam scanning from 8.3 to 9.0 GHz; (2) Mode 2: 22°left-handed CP beam scanning from 8.3 to 9.0 GHz; (3) Mode 3: 78°LP beam scanning from 8.3 to 10.3 GHz. In Mode 1 and 2, the axial ratios (ARs) are lower than 3 dB, and the average gain can reach 11.6 dBi, while 13.4 dBi in Mode 3. A leaky wave antenna that can switch the radiation function of linear/circular polarization with favorable performance characteristics, such as wide scanning range, high gain, low sidelobe levels, and high efficiency, makes it an ideal candidate for wireless communication.

Compact Folded SSPP Transmission Line and Its Applications in Low-Pass Filters

This paper proposes two compact folded spoof surface plasmon polariton (SSPP) transmission lines (TL) with single-sided grooves (Type A) and double-sided grooves (Type B), and their cut-off frequencies are 17.55 GHz and 19.52 GHz, respectively. Due to large number of units, the proposed SSPP TLs have steep sideband and excellent upper band suppression (<-48 dB). The compact folding solution could reduce the lateral size to nearly 2/5 of the original one, and to a certain extent solve the layout difficulties associated with traditional SSPP TLs due to their slender structure. The cut-off frequency can be independently regulated by stub length and width. The proposed components are fabricated and tested. The experimental results are in good agreement with the simulated results, demonstrating the possibility of compact folded SSPP TLs and greatly improving the potential of SSPP use in miniaturized and highly integrated circuit systems.

A metamaterial sensor for detecting the location of a sub-wavelength object

A metamaterial sensor is proposed to detect the random location of a sub-wavelength metallic object. The sensor is composed of a transmission line (TL), which supports the propagation of spoof surface plasmon polaritons (SSPPs) with localized electromagnetic (EM) field, and a complementary spiral resonator (CSR) that resonates strongly at designed frequencies around 0.9 and 2.7 GHz. Based on the shift of the resonance frequencies, this sensor is able to detect the location of a sub-wavelength metallic object (whose diameter is smaller than 0.6 mm) randomly attached to the CSR. A prototype of the sensor is fabricated and tested. In practice, the CSR is excited through the EM coupling of the SSPP TL, and the location of the metallic object is obtained through the transmission coefficient (S21). To improve the accuracy, a retrieval curve for locating is generated and calibrated. It is proved that the random location of the sub-wavelength object can be accurately detected inside an area of 9π mm2 with a low error of 2‰.