Sekhar Ranjan Bhadra Chaudhuri

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 Novel Tri-Band Hexagonal Microstrip Patch Antenna Using Modified Sierpinski Fractal for Vehicular Communication

The present paper analyses and documents the merits of incorporating fractal design in microstrip antenna intended to be mounted on and integrated into the design of smart vehicles. A novel design is proposed for a compact tri-band hexagonal microstrip antenna to be integrated with the body of a smart vehicle for short range communication purpose in an Intelligent Transport System (ITS). This antenna can be used at 1.575 GHz of GPS L1 band for vehicle to roadside communication, at 3.71 GHz of mobile WiMAX band (IEEE 802.16e-2005) for blind spot detection and at 5.9 GHz of DSRC band (IEEE 802.11p) for vehicle to vehicle communication. At 3.71 GHz, the two major lobes of the antenna radiation beam, tilted by 35 ◦ on both sides from its broadside direction, help the vehicle to detect blind spots efficiently. The largest dimension of the proposed antenna corresponds to the lowest resonating frequency, 1.575 GHz. Compared to the conventional hexagonal patch, the modified Sierpinski fractal proposed herein reduces the overall area, at 1.575 GHz, by 75%, with 5.2 dBi gain. In comparison with other popular fractals, the proposed fractal structure achieves demonstrably better antenna miniaturization. When the antenna is mounted on the vehicle, considered an electromagnetically larger object, the simulated and on-vehicle experimental results show antenna gains of more than 5.5 dBi at 1.575 GHz, 8 dBi at 3.71 GHz and 9 dBi at 5.9 GHz in the desired direction with negligible amount of electromagnetic interference inside the car.

ULTRA-WIDEBAND PERFORMANCE OF PRINTED HEXAGONAL WIDE-SLOT ANTENNA WITH DUAL BAND-NOTCHED CHARACTERISTICS

In this paper, ultra-wideband characteristics of a hexagonal wide slot antenna with dual band-notched property have been proposed and experimentally investigated. By etching a pair of L-shaped slots and embedding a pair of parallel strip conductors, dual band-notched properties in WiMAX/C-Band satellite application and WLAN band are achieved respectively. Good impedance matching is obtained over a wide band by designing the feed structure with a 50› microstripline loaded by a tuning stub. The stub is proposed to have one hexagonal section and one straight section. The proposed antenna operates over 2.0GHz{10.7GHz range, for VSWR • 2, excluding the two rejection bands from 3.4GHz to 4.3GHz and 5.12GHz to 6.4GHz having rejection level VSWR of 7.84 and 6.5 respectively. The impedance bandwidth of the antenna is 5.35 : 1. The proposed ultra- wideband structure also exhibits constant group delay, satisfactory gain and high radiation e-ciency in the pass band.

Mutual Coupling Reduction Between Closely Placed Microstrip Patch Antenna Using Meander Line Resonator

An approach of reducing Mutual Coupling between two patch antennas is proposed in this paper. Here, a meander line resonator is placed in between the radiating elements. By inserting the meander line resonator between the patch antennas with the edge-to-edge distance less than λ/18, about 8 dB reduction of Mutual Coupling throughout the 10-dB bandwidth has been achieved without degrading the radiation pattern. The circuit model of the proposed configuration is carried out in this paper. The envelope correlation coefficient investigation has been done and the results are presented. The proposed structure has been fabricated and measured.

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.

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.

Design of a compact triple-band metamaterial absorber with wide angle of incidence using connected resonator topology

A compact triple band metamaterial absorber is presented in this paper. The triple band absorbance is achieved by combining a meander line loaded rectangular close ring resonator with an electric field driven LC resonator within a single unit cell. A more compact unit cell having a size reduction of 14.47% and triple band absorption has been realized as an advantage over close ring metamaterial absorber. The artificially engineered structure has triple band absorbance with one band laying in C-band and another two in Ku and K band respectively. This triple band design can be used for stealth technology such as the C-band airborne radar and battlefield applications. Moreover, the absorber can perform well over a wide angle of incidence.

Analysis of a rectangular slot on a microstrip patch antenna with an equivalent circuit model

The effects of parametric variation of a rectangular slot on a square microstrip patch antenna (MSPA) have been analyzed from physical perspective, along with an equivalent circuit model.

Design of an extremely wideband monopole antenna with triple notches

Three notch bands are created in a CPW fed extremely wideband printed monopole antenna to avoid interference from other existing systems while providing multiple wireless services. The base antenna shows 2:1 VSWR bandwidth from 1.6 Ghz to over 26 Ghz. By incorporating a slot on the patch, another slot on the ground plane and a T-shaped metal strip at the back side of the substrate, three band notches are introduced in the VSWR bandwidth to prevent interference from WLAN (3.5 Ghz and 5.2 Ghz) and C-band satellite communication systems around 7.3 GHz. Gain remains fairly constant over the entire bandwidth with very low gain at the notched bands.