Ashif Fathnan

National Research and Innovation Agency

Metasurfaces can implement a wide variety of wave-manipulation functions with sub-wavelength layers. They are typically created from resonant elements, thus their refraction properties depend strongly on frequency. The resulting chromatic aberration is undesirable for most applications, motivating recent efforts in the development of achromatic met...

Metasurfaces have emerged as a promising technology for the manipulation of electromagnetic waves within a thin layer. In planar ultrathin metasurfaces, there exist rigorous design methods, based on the equivalent surface impedance of patterned metallic layers on dielectric substrates. In this work, we derive a limit on bandwidth achievable in thes...

Matching magnetic and electric responses has proven key to achieving high‐efficiency transmissive Huygens’ metasurfaces. However, the complex frequency dependence of the required magnetic and electric responses is difficult to control, causing inevitable mismatch and undesired narrowband responses. Here, a rigorous design methodology is proposed to...

Wireless communications and sensing have notably advanced thanks to the recent developments in both software and hardware. Although various modulation schemes have been proposed to efficiently use the limited frequency resources by exploiting several degrees of freedom, antenna performance is essentially governed by frequency only. Here, we present...

Wave phenomena can be artificially engineered by scattering from metasurfaces, which aids in the design of radio-frequency and optical devices for wireless communication, sensing, imaging, wireless power transfer and bio/medical applications. Scattering responses vary with changing frequency; conversely, they remain unchanged at a constant frequenc...

We present an effective method for transmitting electromagnetic waves as surface waves with a tape-based metasurface design. This design incorporates silver square patches periodically patterned on an adhesive tape substrate. Specifically, our study proposes a strategy to enhance the efficiency of power transfer in high-frequency bands by guiding s...

Comprehensive numerical tools to investigate and analyze the surface wave attenuation on a metasurface waveguide that consists of periodic patches deposited on a dielectric substrate are presented. The surface wave attenuation is evaluated in both waveguide and open‐space environments at high frequencies around the 28‐GHz band. Two approaches inclu...

In this paper, a design scheme for a dual‐band waveform‐selective metasurface absorber (MSA) is presented based on the combination of two metal resonator structures loaded with nonlinear circuits. Dual‐band MSAs with four different configurations are constructed by loading capacitor/inductor‐based nonlinear circuits into the gaps of two square‐patc...

A passive, low‐cost, paper‐based intelligent reflecting surface (IRS) is designed to reflect a signal in a desired direction to overcome non‐line‐of‐sight scenarios in indoor environments. The IRS is fabricated using conductive silver ink printed on paper with a specific nanoparticle arrangement, yielding a cost‐effective paper‐based IRS that can e...

In this study, we present a design method to realize waveform-selective metasurface absorbers operating in more than one frequency band, which is validated both numerically and experimentally. The waveform-selective metasurface absorbers could preferentially absorb target electromagnetic waves of the same frequency in accordance with the incident w...

In this correspondence, we present a reconfigurable intelligent surface (RIS) that reflects an incident signal to the desired direction, depending on the pulse width. This unique reconfigurability emerges by virtue of the transient response of the embedded nonlinear circuits within the RIS unit cells. The RIS does not need any control lines connect...

Microwave absorbers play an important role in protecting sensitive electronic devices from electromagnetic (EM) interference by absorbing the energy of incoming waves and reducing unnecessary reflection or transmission. Here, we numerically and experimentally demonstrated two types of waveform-selective microwave metasurface absorbers (MMAs) with a...

We present a new concept of metasurface filters to preferentially extract pulsed waveforms at a constant frequency from a complex superimposed input signal. This filtering capability is realized using circuit-based metasurfaces, denoted waveform-selective metasurfaces, that behave according to the pulse duration of the incident wave. Importantly, o...

Wave phenomena can be artificially engineered by scattering from metasurfaces, which aids in the design of radio-frequency and optical devices for wireless communication, sensing, imaging, wireless power transfer and bio/medical applications. Scattering responses vary with changing frequency; conversely, they remain unchanged at a constant frequenc...

In this study, we numerically demonstrate how the response of recently reported circuit-based metasurfaces is characterized by their circuit parameters. These metasurfaces, which include a set of four diodes as a full wave rectifier, are capable of sensing different waves even at the same frequency in response to the incident waveform, or more spec...

In this study, we numerically demonstrate how the response of recently reported circuit-based metasurfaces is characterized by their circuit parameters. These metasurfaces, which include a set of four diodes as a full wave rectifier, are capable of sensing different waves even at the same frequency in response to the incident waveform, or more spec...

In this correspondence, we present a reconfigurable intelligent surface (RIS) that reflects an incident signal to the desired direction, depending on the pulse width. This unique reconfigurability emerges by virtue of the transient response of the embedded nonlinear circuits within the RIS unit cells. The RIS does not need any control lines connect...

Abstract The authors present metasurface‐inspired maintenance‐free Internet of things (IoT) tags that can be characterised not only by frequency‐domain profiles but also by time‐domain profiles. In particular, time‐domain characterisation is made possible by implementing the waveform‐selective mechanisms of recently developed circuit‐based metasurf...

With their self-tuned time-varying responses, waveform-selective metasurfaces embedded with nonlinear electronics have shown fascinating applications, including distinguishing different electromagnetic waves depending on the pulse width. However, thus far they have only been realized with a spatially homogeneous scattering profile. Here, by modelin...

We present metasurface-inspired maintenance-free IoT tags that can be characterised not only by frequency-domain profiles but also by time-domain profiles. In particular, time-domain characterisation is made possible by implementing the waveform-selective mechanisms of recently developed circuit-based metasurfaces that behave differently, even at t...

With their self-tuned time-varying responses, waveform-selective metasurfaces embedded with nonlinear electronics have shown fascinating applications, including distinguishing different electromagnetic waves depending on the pulse width. However, thus far they have only been realized with a spatially homogeneous scattering profile. Here, by modelin...

Wireless communications and sensing have notably advanced thanks to the recent developments in both software and hardware. Although various modulation schemes have been proposed to efficiently use the limited frequency resources by exploiting several degrees of freedom, antenna performance is essentially governed by frequency only. Here, we present...

Anisotropic impedance surfaces have been used to control surface wave propagation, which has benefited applications across a variety of fields including radio-frequency (RF) and optical devices, sensing, electromagnetic compatibility, wireless power transfer, and communications. However, the responses of these surfaces are fixed once they are fabri...

We report the characterization of an achromatic focusing metasurface at oblique incident angles. We show that in addition to the inherent off-axis aberrations that occur due to the hyperbolic phase profile of the metasurface, the focusing performance is significantly degraded due to the meta-atoms’ angular dispersion. To obtain insights into how th...

We report the characterization of an achromatic focusing metasurface at oblique incident angles. We show that in addition to the inherent off-axis aberrations that occurs due to the hyperbolic phase profile of the metasurface, the focusing performance is significantly degraded due to the meta-atoms' angular dispersion. To obtain insights into how t...

We develop broadband achromatic metasurfaces suited for microwave frequencies, by tailoring LC resonances in series and parallel configurations. We present a synthesis method for a transmissive metasurface and discuss limits on their realizable bandwidth.

Metasurfaces have emerged as a promising technology for the manipulation of electromagnetic waves within a thin layer. Initially based on narrowband design principles, the field has since expanded to include broadband achromatic designs, which maintain reflection or refraction angles over some bandwidth, and broadband dispersive designs, which main...

We propose a new metamaterial antenna on electro-optic (EO) modulator for wireless terra-hertz detection through radio-over-fibre (ROF) technology. By wireless terra-hertz signal irradiation to the proposed device, strong terra-hertz electric field can be induced on the electric- LC metamaterial resonator. The induced terra-hertz electric field can...

High sensitivity environmental sensors with a simple and compact structure are required to monitor unwanted pollution such as liquid waste. In this research, a component of environmental sensor based on optical channel waveguide Mach-Zehnder interferometer (MZI) has been designed and also simulated. The materials used in the design were titanium di...

Optimization of tapioca wastewater treatment by electrocoagulation has been conducted. Taguchi design experiment was used to calculate the optimum condition. Electrode distance, an electrical resistance of the wastewater and time of operation were used as the parameters. The results show that the electrocoagulation using bipolar stainless steel ele...

Investigations on the electromagnetic coupling effect of rectangular split ring resonators (SRRs) coupled to coplanar waveguide (CPW) are presented. Rectangular SRRs shape alteration and its effect to transmission line performance has been studied by changing its vertical and horizontal 2-d orientation. We observe that the confined magnetic field p...

In this paper, we present a metamaterial coplanar waveguide (CPW) filter with performance improvement utilizing horizontal rectangular split ring resonators (SRRs). The filter is designed for S-Band frequency operation of 2.3 GHz allowing application in many microwave communication systems. We study S-parameter results and find that improvement of...

Microstrip antenna is a shaped thin board of antenna and capable for working at high frequencies. Microstrip antenna has a pattern strip shape in a various form , one of which is a rectangular shape. Microstrip antennas have some shortcomings which have narrow bandwidth and small gain, to cover the shortfall , the antenna is made using an array to...

We report current research progress on a metamaterial antenna integrated to an optical modulator for millimeter-wave-photonic links. The metamaterial antennas are composed by an array of electric-LC resonators on a LiNbO3 optical crystal. Large electric field is induced across the capacitance gaps of the resonators due to free-space millimeter-wave...

We propose and discuss a compact bandpass filter in coplanar waveguide (CPW) loaded with rectangular split-ring resonators (SRRs). The proposed device is designed on a planar structure where the rectangular SRRs and CPW are arranged in the different side. Basic characteristics of the proposed device such as Q-factor, insertion loss, and out of band...

A microstrip exponential-square patch antenna have been proposed and simulated in this paper. It consists of an exponential-square patch, a substrate, a square ground plane and probe feed. The exponential-square patch shape is modified from conventional square geometry with two parallel side replaced by two exponential curve. From simulation result...

We propose and present millimeter-wave antennas using metamaterial ELC resonators on electro-optic substrates for wireless millimeter-wave receivers and optical modulators. Analysis for the antenna characteristics of the proposed device are discussed for millimeter-wave frequency of 100GHz.

This paper discusses a novel structure of deep trench capacitor with breakdown voltage of 10V and capacitance density of 527nF/mm 2 , serving for Low Dropout Voltage regulator in IC power management. The structure is presented using 3D & 2D Sentaurus Synopsys simulation, with RIE etching and high quality LPCVD is deployed on the equivalent process....

This paper presents an analytical model of y-parameters for trench capacitors devices. 2-d poisson's solution is used, which gives the closed form solutions of the potential and electrical field distributions as a function of the structure parameters and top electrode bias. Dependence of substrate equivalent series resistance on current path length...

Indonesia as the largest country organizing the hajj, have strong reason to continue to improve the system of national pilgrimage (Hajj). With the large amount of pilgrims, the ha.i.i organizing has to be managed properly by the government, both at the time of execution or before departure. One of the governments provided facilities for pilgrims be...