Bratin Ghosh

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.

A Loop Loading Technique for the Miniaturization of Non-Planar and Planar Antennas

A size reduction technique of non-planar and planar antennas using a self-resonant topology is highlighted. The antennas considered are the dipole, the monopole and the slot radiator. The dipole below its resonant frequency is known to possess a capacitive reactance. It is shown that the inductive reactance of a loop can be used to match a below-resonant dipole similar to the inductive load offered by a metamaterial shell. The configuration reduces the resonant frequency of the dipole by 26.01%, causing the dipole to almost reach the electrically small limit. Despite the loaded dipole touching the electrically small limit, the antenna needs no matching networks, offers a high efficiency and exhibits a bandwidth better than the unperturbed dipole. The radiation pattern is also seen to be unaffected by the presence of the loops. The concept is also demonstrated for the size-reduction of a monopole and for a planar slot.

Mode Excitation in the Coaxial Probe Coupled Three-Layer Hemispherical Dielectric Resonator Antenna

In this paper, a coax-probe excited multilayer dielectric resonator antenna (DRA) structure is rigorously analyzed from the modal perspective. The full-wave Greens function approach is presented for the analysis of such multilayer structures with an arbitrary number of layers with greatly reduced computational overhead. Additional reduction in computation time is demonstrated for a centered probe. Also, the modes of the multilayer DRA can be identified from the analysis, which can be used to explain the broadband nature of the coupling. The layer permittivities are optimized for broadband operation of the coax-fed DRA. The bandwidth enhancement for a centered and offset probe is seen to be due to a combination of several DRA modes and the probe resonance. Frequency tuning of the antenna structure is also demonstrated by exciting the antenna at a higher order mode, maintaining the broadband characteristics. The radiation characteristics of the antenna are also investigated.

Efficient Technique for the Analysis of Microstrip Slot Coupled Hemispherical Dielectric Resonator Antenna

In this letter, a novel method for the numerical evaluation of the Greens function for the microstrip slot coupled hemispherical dielectric resonator is presented. The proposed technique is very fast as compared to the conventional method of fourfold integration. In this technique, the homogeneous part of the dielectric resonator antenna (DRA) Greens function is manipulated in such a manner that its source and field terms are expressed in the absolute product form. Then, using method of moments (MoM), the absolute product form is numerically integrated by the product of two double integrations. The input impedance calculation using the proposed technique is almost 48 times faster than conventional technique. The method is very rigorous and general and should find applications in the other hemispherical DRA configurations.

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.

Miniaturization of Slot Antennas Using Wire Loading

The design of a miniaturized slot antenna based on wire-loading is presented. The miniaturization can be achieved with minimal increase in the lateral space along the slot width. Both the cases of a slot antenna on dielectric substrate and a slot antenna on ground plane are considered. For the former case, a miniaturization of 28.83% is achieved. The radiation characteristics of the size-reduced antenna are almost similar to the unloaded slot, with low cross-polarization levels. For the slot antenna on a ground plane, the miniaturization is affected by a cavity-backed design with the loading wires penetrated into the cavity. A 45.52% reduction in resonant frequency is achieved relative to the unloaded slot. The radiation characteristics in the upper hemisphere are almost unperturbed compared to the unloaded slot.

Guided Modes in a Metamaterial-Filled Circular Waveguide

Abstract In this article, characteristics of circular waveguides filled with metamaterials are studied. Also, for the first time, hybrid modes are investigated, and several new conclusions in hybrid mode behavior are drawn. Particularly, conditions under which the hybrid mode separates into the transverse electric and transverse magnetic (n = 0) modes are obtained. This condition eases mode excitation in the waveguide without power being coupled to the undesired modes. Frequency dispersive behavior of the modes under isotropic conditions is addressed with potential applications. The anisotropic implementation, which offers a good technique for the practical realization of metamaterial-filled circular guides, is also investigated.

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.

Coplanar Waveguide Feed to the Hemispherical DRA

In this communication, several coplanar waveguide topologies to the hemispherical DRA are presented. It is seen that the inductive and the circular-loop CPW feed configurations offer the flexibility to excite the fundamental TE 111 resonant mode of the hemispherical DRA close to the source free resonant frequency, due to the presence of metallization in the coupling region. Dual-band behavior is observed with the capacitive feed due to the DRA and slot resonant modes, which are displaced with respect to the unperturbed modes due to the uninterrupted slot. The radiation characteristics of the antenna are also explained.

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.