Single-conductor co-planar quasi-symmetry unequal power divider based on spoof surface plasmon polaritons of bow-tie cells

In this paper, the spoof surface plasmon polaritons (SSPPs) transmission line (TL) of periodical grooved bow-tie cells is proposed. The complex propagation constant and characteristic impedance of the SSPPs TLs and microstrip lines (MLs) are extracted using the analytical method of generalized lossy TL theory. The properties of the SSPPs TLs with different substrates and the same geometrical configuration are experimented. Then, for comparison, two ML counterparts are also experimented, which shows that the SSPPs TL is less sensitive to the thickness, dielectric constant and loss tangent of the chosen substrate below the cutoff frequency, compared with the ML ones. The single-conductor co-planar quasi-symmetry unequal power divider based on this SSPPs TL is presented in microwave frequencies. For experimental validation, the 0-dB, 2-dB, and 5-dB power dividers are designed, fabricated, and measured. Both simulated and measured results verify that the unequal power divider is a flexible option, which offers massive advantages including single-conductor co-planar quasi-symmetry structures, wide-band operation, and convenient implementations of different power-dividing ratios. Hence, it can be expected that the proposed unequal power dividers will inspire further researches on SSPPs for future design of novel planar passive and active microwave components, circuits and systems

Design, Analysis and Characterisation of Spoof Surface Plasmon Polaritons based Wideband Bandpass Filter at Microwave Frequency

This paper presents the wideband bandpass filter (BPF) in the microwave frequency domain. The realisation approach is based on spoof surface plasmon polaritons (SSPPs) phenomenon using plasmonic metamaterial. A novel unit cell is designed for filter design using an LC resonator concept. Then SSPPs BPF is realised using an optimised mode converter and five unit cells. This paper includes a brief design detail of the proposed novel unit cell. The passband of BPF is achieved at approximately 1.20 - 5.80 GHz, 3dB bandwidth is tentatively 4.60 GHz and the insertion loss is less than 2 dB approximately over the passband. The overall dimension of fabricated filter is (90 x 45) mm. A basic schematic of transmission line representation is also proposed to evaluate the BPF structure

Spoof Surface Plasmon Polariton Leaky-Wave Antennas using Periodically Loaded Patches above PEC and AMC Ground Planes

This letter proposes two spoof surface plasmon polariton (SSPP) leaky-wave antennas using periodically loaded patches above perfect electric conductor (PEC) and artificial magnetic conductor (AMC) ground planes, respectively. The SSPP leaky-wave antenna is based on an SSPP transmission line, along which circular patches are periodically loaded on both sides to provide an additional momentum for phase matching with the radiated waves in the air. The PEC and AMC ground planes underneath the antenna reflect the radiated waves into the upward space, leading to an enhanced radiation gain. Both PEC- and AMC-grounded antenna prototypes are fabricated and measured in comparison with the one without any ground plane. The experimental results show that the PEC and AMC ground planes increase the radiation gain by approximately 3 dB within the operational frequency range 4.5-6.5 GHz. It also demonstrates that the AMC-grounded leaky-wave antenna, with a thickness of 0.08λ₀ at 6 GHz, features more compact profile than the PEC-grounded one (with a thickness of 0.3λ₀ at 6 GHz)

Planar-Goubau-line components for terahertz applications

Terahertz-wave technology has a broad range of applications, including radio astronomy, telecommunications, security, medical applications, pharmaceutical quality control, and biological sensing. However, the sources, detectors, and components are less efficient at this frequency band due to parasitic effects and increased total losses, which hinder the performance of terahertz systems. A common platform for terahertz systems is planar technology, which offers good integration, ease of fabrication, and low cost. However, it also suffers from high losses, which must be minimised to keep the system\u27s performance. A pivotal choice to reduce losses is using power-efficient waveguides, and single-conductor waveguides have shown promisingly high power efficiencies compared to multi-conductor planar waveguides. The planar Goubau line (PGL) is a planar single-conductor waveguide consisting of a metal strip on top of a dielectric substrate which propagates a quasi-transverse magnetic surface wave, similarly to Sommerfeld\u27s wire and the Goubau line, a conducting wire coated with a dielectric layer. Some limitations of the PGL, which complicate the design of components, are the lack of a ground plane and the weak dependence of impedance with the metal strip width of the line.This thesis presents the development of PGL technology and components for terahertz frequencies. It developed design strategies to maximise the power efficiency, using electrically-thin substrates, which drastically drop radiation losses compared to thick substrates. The first PGL calibration standards were developed, which de-embeds the transition needed to excite the propagation mode and sets the calibration plane along the line, allowing the direct characterisation of PGL components. This work also presents several PGL components with a straightforward design procedure, including a stopband filter based on capacitively-coupled λ/2 resonators, an impedance-matched load based on an exponentially-tapered corrugated line, and a power divider based on capacitive-gap coupled lines to a standing wave in the input port. Finally, the PGL was integrated with a microfluidic channel to measure changes in the complex refractive index of a high-loss aqueous sample (water/isopropyl alcohol) as the first step toward a biological sensor

Metamaterial

In-depth analysis of the theory, properties and description of the most potential technological applications of metamaterials for the realization of novel devices such as subwavelength lenses, invisibility cloaks, dipole and reflector antennas, high frequency telecommunications, new designs of bandpass filters, absorbers and concentrators of EM waves etc. In order to create a new devices it is necessary to know the main electrodynamical characteristics of metamaterial structures on the basis of which the device is supposed to be created. The electromagnetic wave scattering surfaces built with metamaterials are primarily based on the ability of metamaterials to control the surrounded electromagnetic fields by varying their permeability and permittivity characteristics. The book covers some solutions for microwave wavelength scales as well as exploitation of nanoscale EM wavelength such as visible specter using recent advances of nanotechnology, for instance in the field of nanowires, nanopolymers, carbon nanotubes and graphene. Metamaterial is suitable for scholars from extremely large scientific domain and therefore given to engineers, scientists, graduates and other interested professionals from photonics to nanoscience and from material science to antenna engineering as a comprehensive reference on this artificial materials of tomorrow

Diversified Fluid Antenna Designs for Mobile Communications

In current mobile communications, massive MIMO is an essential technology, especially for mm-wave 5G and future 6G mobile systems. However, implementing MIMO antennas for such applications is challenging due to the physical limitations of mobile devices. To address this issue, this study proposes novel surface wave-based fluid antennas. The proposed antennas achieve radiation pattern reconfigurability with a compact design of 10 mm x 33 mm 5 mm at a frequency range of 24 to 30 GHz, which is small enough for portable equipment. These antennas use only one feeding port, simplifying the feeding mechanism compared to MIMO systems that may require multiple RF chains. The fluid channel can also be easily scaled for different shapes and sizes with the proposed surface wave launcher. The proposed fluid antennas were simulated, fabricated, assembled, and measured within UCL facilities. Results show that these antennas achieve radiation pattern diversity, with an average RPDR (radiation pattern dynamic range) of up to 10 dB in the targeted mm-wave 5G frequency bands from 24 to 30 GHz. Radiation pattern dynamic range is a new indicator used to evaluate the proposed fluid antennas' radiation pattern reconfigurability. The proposed antennas offer several notable contributions. Firstly, they demonstrate the successful development of fluid antennas with radiation pattern reconfigurability. Secondly, the antennas feature a relatively simple structure, utilizing a 3D-printed container and PCB board, which enables cost-effective manufacturing and makes the antennas accessible to a wider range of users. Thirdly, the proposed fluid antenna incorporates a fluid control system and a comprehensive measurement setup specifically tailored for fluid antennas. These additions enhance the overall viability and practicality of the antenna design. Lastly, the introduction of the RPDR indicator provides a valuable tool for analyzing the radiation pattern reconfigurability of similar antennas. This indicator facilitates performance comparisons and aids in the refinement of future antenna designs

Passive Planar Microwave Devices

The aim of this book is to highlight some recent advances in microwave planar devices. The development of planar technologies still generates great interest because of their many applications in fields as diverse as wireless communications, medical instrumentation, remote sensing, etc. In this book, particular interest has been focused on an electronically controllable phase shifter, wireless sensing, a multiband textile antenna, a MIMO antenna in microstrip technology, a miniaturized spoof plasmonic antipodal Vivaldi antenna, a dual-band balanced bandpass filter, glide-symmetric structures, a transparent multiband antenna for vehicle communications, a multilayer bandpass filter with high selectivity, microwave planar cutoff probes, and a wideband transition from microstrip to ridge empty substrate integrated waveguide

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium