Capacitive Loaded Strip Research Articles

Investigation of Left-Handed Meta-Atom for Radio Frequency Shielding Application

A compact theta-shaped left-handed meta-atom based on an elliptical split ring resonator (ESRR) with a capacitive loaded strip (CLS), is presented in this paper. The elliptical split ring resonator is a changeover of conventional square split ring resonator (SRR). A CLS is introduced in the middle of the ESRR to increase the electrical length and coupling effect. Electromagnetic transmission characteristics of FR-4 and Rogers RO3010 substrate are investigated in a comparative manner for varying values of substrate parameters which are thickness, dielectric constant and dielectric loss tangent. The effective constitutive parameters are retrieved by using the transmission-reflection method. The proposed structure shows a double negative regime from 3.6 to 5.6 GHz (bandwidth of 2 GHz) for FR-4 and from 3.1 to 4.8 GHz (bandwidth of 1.7 GHz) for RO3010 in microwave frequency spectrum. An effective medium ratio (EMR) of 9.27 and 13.36, implies the novelty of the proposed structure. The proposed ESRR is found to reach the lowest resonance frequency while maintaining smallest electrical size, a highly desired property for miniaturization in RF design. Which makes it a prime candidate to reduce RF signal interference of electronic devices, equipment, and systems.

A Printed Xi-Shaped Left-Handed Metamaterial on Low-Cost Flexible Photo Paper.

A Xi-shaped meta structure, has been introduced in this paper. A modified split-ring resonator (MSRR) and a capacitive loaded strip (CLS) were used to achieve the left-handed property of the metamaterial. The structure was printed using silver metallic nanoparticle ink, using a very low-cost photo paper as a substrate material. Resonators were inkjet-printed using silver nanoparticle metallic ink on paper to make this metamaterial flexible. It is also free from any kind of chemical waste, which makes it eco-friendly. A double negative region from 8.72 GHz to 10.91 GHz (bandwidth of 2.19 GHz) in the X-band microwave spectra was been found. Figure of merit was also obtained to measure any loss in the double negative region. The simulated result was verified by the performance of the fabricated prototype. The total dimensions of the proposed structure were 0.29 λ × 0.29 λ × 0.007 λ. It is a promising unit cell because of its simplicity, cost-effectiveness, and easy fabrication process.

Microwave Imaging Sensor Using Compact Metamaterial UWB Antenna with a High Correlation Factor.

The design of a compact metamaterial ultra-wideband (UWB) antenna with a goal towards application in microwave imaging systems for detecting unwanted cells in human tissue, such as in cases of breast cancer, heart failure and brain stroke detection is proposed. This proposed UWB antenna is made of four metamaterial unit cells, where each cell is an integration of a modified split ring resonator (SRR), capacitive loaded strip (CLS) and wire, to attain a design layout that simultaneously exhibits both a negative magnetic permeability and a negative electrical permittivity. This design results in an astonishing negative refractive index that enables amplification of the radiated power of this reported antenna, and therefore, high antenna performance. A low-cost FR4 substrate material is used to design and print this reported antenna, and has the following characteristics: thickness of 1.6 mm, relative permeability of one, relative permittivity of 4.60 and loss tangent of 0.02. The overall antenna size is 19.36 mm × 27.72 mm × 1.6 mm where the electrical dimension is 0.20 λ × 0.28 λ × 0.016 λ at the 3.05 GHz lower frequency band. Voltage Standing Wave Ratio (VSWR) measurements have illustrated that this antenna exhibits an impedance bandwidth from 3.05 GHz to more than 15 GHz for VSWR < 2 with an average gain of 4.38 dBi throughout the operating frequency band. The simulations (both HFSS and computer simulation technology (CST)) and the measurements are in high agreement. A high correlation factor and the capability of detecting tumour simulants confirm that this reported UWB antenna can be used as an imaging sensor.

A Negative Index Metamaterial-Inspired UWB Antenna with an Integration of Complementary SRR and CLS Unit Cells for Microwave Imaging Sensor Applications.

This paper presents a negative index metamaterial incorporated UWB antenna with an integration of complementary SRR (split-ring resonator) and CLS (capacitive loaded strip) unit cells for microwave imaging sensor applications. This metamaterial UWB antenna sensor consists of four unit cells along one axis, where each unit cell incorporates a complementary SRR and CLS pair. This integration enables a design layout that allows both a negative value of permittivity and a negative value of permeability simultaneous, resulting in a durable negative index to enhance the antenna sensor performance for microwave imaging sensor applications. The proposed MTM antenna sensor was designed and fabricated on an FR4 substrate having a thickness of 1.6 mm and a dielectric constant of 4.6. The electrical dimensions of this antenna sensor are 0.20 λ × 0.29 λ at a lower frequency of 3.1 GHz. This antenna sensor achieves a 131.5% bandwidth (VSWR < 2) covering the frequency bands from 3.1 GHz to more than 15 GHz with a maximum gain of 6.57 dBi. High fidelity factor and gain, smooth surface-current distribution and nearly omni-directional radiation patterns with low cross-polarization confirm that the proposed negative index UWB antenna is a promising entrant in the field of microwave imaging sensors.

Gain Improvement of Microstrip Patch Antenna Using CLS Split Ring Resonator Metamaterial

AbstractMetamaterials are artificial materials with negative permittivity and permeability. Metamaterials due to their unique negative parameter are capable of focusing the electromagnetic energy incident upon them. This focusing of electromagnetic energy is used to increase the gain of microstrip patch antenna. A capacitive loaded strip (CLS)-loaded split ring resonator is used to form a multilayer array of metamaterial and used in front of microstrip patch antenna to enhance far-field gain of antenna. An accurate simulation model is created and analyzed using CST. The simulated model is then fabricated and measured in fully anechoic chamber for validation. The far-field gain of regular patch antenna with and without metamaterial is measured in anechoic chamber. The increase in gain by 4 dB is measured at 95 mm from antenna. The beam focusing property is also evident from 3 dB beamwidth of antenna which is reduced to 42.01°.

A Miniaturized Antenna with Negative Index Metamaterial Based on Modified SRR and CLS Unit Cell for UWB Microwave Imaging Applications.

A miniaturized antenna employing a negative index metamaterial with modified split-ring resonator (SRR) and capacitance-loaded strip (CLS) unit cells is presented for Ultra wideband (UWB) microwave imaging applications. Four left-handed (LH) metamaterial (MTM) unit cells are located along one axis of the antenna as the radiating element. Each left-handed metamaterial unit cell combines a modified split-ring resonator (SRR) with a capacitance-loaded strip (CLS) to obtain a design architecture that simultaneously exhibits both negative permittivity and negative permeability, which ensures a stable negative refractive index to improve the antenna performance for microwave imaging. The antenna structure, with dimension of 16 × 21 × 1.6 mm3, is printed on a low dielectric FR4 material with a slotted ground plane and a microstrip feed. The measured reflection coefficient demonstrates that this antenna attains 114.5% bandwidth covering the frequency band of 3.4–12.5 GHz for a voltage standing wave ratio of less than 2 with a maximum gain of 5.16 dBi at 10.15 GHz. There is a stable harmony between the simulated and measured results that indicate improved nearly omni-directional radiation characteristics within the operational frequency band. The stable surface current distribution, negative refractive index characteristic, considerable gain and radiation properties make this proposed negative index metamaterial antenna optimal for UWB microwave imaging applications.

Miniaturized Ultra-Wideband Antenna Using Microstrip Negative Index Metamaterial

A three left-handed metamaterial unit cell antenna is presented in this article for ultra-wideband applications. Each left-handed metamaterial unit cell is a combination of a modified octagonal split-ring resonator, an octagonal spiral resonator, a capacitance-loaded strip, and a wire in order to achieve a design that simultaneously exhibits both negative electrical permittivity and negative magnetic permeability, which promises an extraordinary index of negative refraction to enhance the radiated power of the antenna, consequently improving the antenna system. The antenna design was etched on an FR4 epoxy substrate (Farnell Electronic Components Limited, Selangor D.E., Malaysia) with an evident compact size of 25 × 25 × 1.6 mm 3 . Return loss measurements demonstrated that this antenna achieves 94% bandwidth for a voltage standing wave ratio less than 2 over the frequency band of 5.2–13.9 GHz, with a maximum gain and directivity of 3.85 dBi and 5.45 dB, respectively, at 10.5 GHz. These measurement results show good agreement with those of the simulations as well as good omni-directional characteristics within its operating frequency band. The proposed metamaterial antenna is compact and highly directive and has a tunable operational frequency especially for ultra-wideband applications.

Parametric studies on left-handed metamaterial consist of modified split-ring resonator and capacitance loaded strip

This paper describes a new structure of left-handed metamaterial (LHM) based on parametric studies using Computer Simulation Technology (CST) software. The LHM structure is a combination of the modified square rectangular split ring (MSRR) and the capacitance loaded strip (CLS). In this paper, the parametric studies are used to see the effect of frequency and the negative value range of permeability (μr) and permittivity (er) toward changes of LHM parameters. The changes in the dimension of MSSR and CLS affect the S11 and S21 of the LHM structure which will affect the values of permeability and permittivity. The values of permeability and permittivity were extracted from the reflection and transmission coefficient data. The studies proved that the LHM structure can be designed within the frequency range of interest.

MICROSTRIP ANTENNA'S GAIN ENHANCEMENT USING LEFT-HANDED METAMATERIAL STRUCTURE

The design, simulation and fabrication of a left-handed metamaterial (LHM) structure is presented. The combination of the modifled square rectangular Split Ring Resonator (SRR) and the Capacitance Loaded Strip (CLS) were used to obtain the negative value of permeability, and the negative permittivity, . Nicolson- Ross-Wier approach was used to identify the double negative region. A good agreement between simulated and measured results has been achieved. Upon incorporation with a single patch microstrip antenna, the performance of the antenna was improved where the gain of the microstrip antenna was increased up to 4dB, and its bandwidth widens from 2.9% to 4.98%. These improvements are due to the negative refraction characteristics of the LHM structure that acts as a lens when placed in front of the antenna.