Debasis Mitra

Miniaturization of Slot Antennas Using Slit and Strip Loading

The design of a miniaturized slot antenna with slit loading fed by the CPW line is proposed. It is seen that the loading slits can be located only on the feed side without degradation in cross-pol performance, unlike the microstrip-fed case. This releases the ground plane area above the slot for accommodating electronic circuitry and effectively reduces the antenna size. In addition, the resonant frequency in this case is reduced by a further 4.60%, compared to the slits on both sides. Another topology of the miniaturized antenna is investigated with the slits replaced by strips of metallization on the reverse side of the substrate, which leaves the ground plane area completely free. A high reduction in the slot resonant frequency is also observed in this case, with a reflector being used to increase the forward radiation.

BANDWIDTH ENHANCEMENT OF MICROSTRIP LINE AND CPW-FED ASYMMETRICAL SLOT ANTENNAS

In this paper, a bandwidth enhancement technique of asymmetrical slot antenna with two difierent excitation methods is presented. One method of excitation is the microstrip line feed, and the other is the coplanar waveguide feed. The rectangular slot excited by microstrip line feed gives an impedance bandwidth of 14.76% (jS11j < i10dB). When the rectangular slot is excited by a coplanar waveguide (CPW), it gives an impedance bandwidth of 26.61%. Both impedance and radiation characteristics of these antennas are studied.

A Miniaturized Ring Slot Antenna Design With Enhanced Radiation Characteristics

The design of a miniaturized CPW-fed ring slot antenna using interdigitated slits is presented. The fundamental resonant frequency of the ring slot antenna was reduced significantly using an interdigitated slit-loaded structure. A further reduction in resonant frequency to 54.46% of the unloaded resonant frequency of the ring slot antenna was also achieved using multiple interdigitated slits inside the ring, causing the antenna to almost reach the electrically small limit. Thereafter, the antenna characteristics of the electrically small antenna is significantly enhanced using a low impedance metamaterial slab design working under normal incidence, leading to a considerable reduction in superstrate height. Particularly, the directivity and efficiency of the electrically small antenna is significantly improved with the incorporation of the low-profile superstrate. In addition, good matching characteristics are obtained for the miniaturized antenna without the necessity of a matching network together with improved bandwidth.

Metal loaded miniaturized CPW fed DRA

Recently, there has been an increased interest in the realization of miniaturized and high capacity transceiver systems. The dielectric resonator antenna ( DRA ) has been an ideal candidate for low-loss and broadband microwave and millimeter wave applications. The coplanar waveguide ( CPW ) feed has been proposed as an efficient feed topology to the DRA due to its low loss, dispersion, ease of active integration and uniplanar configuration. This paper presents a novel, high gain and miniaturized rectangular dielectric resonator antenna using a metallic slab as a loading element, integrated with the CPW feed. The rectangular DRA is fed with a CPW (Capacitive type) feed to ensure efficient coupling. The unloaded and loaded DRA resonance frequencies are 4.55 GHz and 3.80 GHz respectively, achieving a 16.48% reduction in resonance frequency. The gain of the unloaded and the loaded DRAs are 6.34 dBi and 6.95 dBi respectively. As a result, a 8.77% increase in gain is obtained with the loaded configuration. In addition, despite the high reduction in resonance frequency and conductor loading, it is observed that there is no significant change in efficiency of the loaded antenna relative to the original structure. Also, it is seen that the coupling performance, cross-polarization and front-to-back ratio in the radiated fields of the size-reduced antenna remain essentially unchanged relative to the unloaded configuration.

Mutual coupling reduction in planar antenna by graphene metasurface for THz application

Abstract This paper presents an effective approach to mitigate mutual coupling between two densely packed planar antenna operating at the lower THz frequency band by incorporating a graphene-based metasurface. The graphene metasurface has been designed using Electric inductive capacitive (ELC) resonator on the both sides of a silicon substrate. The metasurface is designed to provide band stop functionality in the operating bandwidth of the antenna. Here, surface impedance model of the graphene is used for analysing the metasurface layer. Throughout the operating band of the antenna, coupling suppression of 8–12 dB is obtained with element separation of less than . Thus, this proposed approach can be utilized to mitigate mutual coupling between antennas in THz application.

Design of UWB Planar Monopole Antennas with Etched Spiral Slot on the Patch for Multiple Band-Notched Characteristics

Three types of Ultrawideband (UWB) antennas with single, double, and triple notched bands are proposed and investigated for UWB communication applications. The proposed antennas consist of CPW fed monopole with spiral slot etched on the patch. In this paper single, double, and also triple band notches with central frequency of 3.57, 5.12, and 8.21 GHz have been generated by varying the length of a single spiral slot. The proposed antenna is low-profile and of compact size. A stable gain is obtained throughout the operation band except the three notched frequencies. The antennas have omnidirectional and stable radiation patterns across all the relevant bands. Moreover, relatively consistent group delays across the UWB frequencies are noticed for the triple notched band antenna. A prototype of the UWB antenna with triple notched bands is fabricated and the measured results of the antenna are compared with the simulated results.

Design of Compact and High Directive Slot Antennas Using Grounded Metamaterial Slab

In this letter, a simple and compact approach for directivity enhancement of slot antenna using a grounded metamaterial slab is proposed. This approach has been applied in two different configurations. In the first configuration, two dielectric layers are used for designing antenna and metamaterial slab. Despite the directivity enhancement, an improved bandwidth of about 10.74% is obtained for this configuration. It is also shown that, over the whole working band, a significant broadside directivity improvement is maintained compared to the unloaded slot. In the second configuration, only a single layer of dielectric is used for designing both antenna and metamaterial slab. Thus, in this case, the total thickness of the loaded antenna is noticeably reduced to 0.5 mm, or 0.014 λ0 at resonance.

Miniaturized C-slot patch antenna for wireless communication

In this paper a new technique for reducing the resonance frequency is proposed using two C-slots on the patch which giving the capacitive effect. The unloaded patch antenna has resonance frequency of 3.96 GHz where as the loaded C-slot patch antenna has resonance frequency of 3.28 GHz. The unique features of our proposed C-slot patch antenna are similar radiation patterns with respect to unloaded patch antenna, high gain, 17.17% reduction in resonance frequency and very good front to back ratio. From the E-Field distribution on patch it can be observed that concentration of electric field is more on the two C-slots on patch antenna which producing capacitive effect and this capacitive effect nullifying the inductance at 3.28 GHz which can be shown from Input impedance curve.

Reduction of leaky wave coupling in a superstrate loaded antenna using metamaterial

ABSTRACT In this paper, an approach is presented for reducing leaky wave coupling of superstrate loaded slot array using zero index metamaterial structure. The dielectric superstrate generally aims at increasing the directivity of the antenna by the generation of leaky wave. In another aspect, the leaky wave reduces the isolation between radiating elements in multiple antenna system. Here, the metamaterial has been used to mitigate the mutual coupling by reducing the generation of the leaky wave. By the help of this approach, the isolation is improved throughout the operational bandwidth and maximum 15 dB isolation improvement is achieved with an edge to edge distance of 4 mm between radiating elements.

MINIATURIZATION AND BANDWIDTH ENHANCEMENT OF A CPW-FED ANNULAR SLOT ANTENNA USING RIS

In this paper a CPW-fed annular slot antenna is miniaturized with enhanced impedance bandwidth using a reactive impedance surface (RIS) substrate. The RIS is realized by patterning 3× 3 array of circular elements over an inexpensive FR-4 substrate which is backed by a circular metallic plane. Due to the compensation of electric and magnetic energy stored by antenna and RIS substrate respectively, the antenna resonance frequency is shifted by 53.6% compared with a simple annular slot antenna. By the inclusion of such reactive surface, input impedance of the antenna is reduced, and a remarkable improvement in impedance bandwidth from 11.66% to 64.26% is also noticed. Therefore, both miniaturization and bandwidth enhancement are achieved simultaneously with the present loading technique. The directivity of the RIS loaded antenna is increased further by loading a concentric metallic ring over the RIS loaded structure at a height above the RIS plane. The Ring & RIS loaded structure is fabricated for measurement purpose. A good agreement is obtained between the simulated and measured results for both RIS loaded and Ring & RIS loaded configurations. The ring loading over the RIS antenna provides improvement in directivity about 5 dB. The peak gain and bandwidth are measured at −1.03 dBi and 58.62%, respectively.