Susanta Kumar Parui

Quasi-elliptic filter characteristics of an asymmetric defected ground structure

An asymmetric defected ground structure (DGS) with respect to a microstrip line is proposed. Its unit cell consists of two square slots connected with a rectangular slot by meandered transverse slots. The simulated, measured and equivalent circuit responses have been presented. The unit DGS pattern under microstrip line produces wide rejection bandwidth and high sharpness factor. Its elliptic band-reject filter response is modelled by appropriate LC equivalent circuit. Two such DGS cells under a microstrip line produce 3-pole quasi-elliptic bandstop filter response, which shows deeper attenuation without appreciable change in pole frequencies in comparison to single cell structure. Unit DGS pattern under coupled gap microstrip lines produces band-accept filtering characteristics. The frequency characteristics show a quasi-elliptic highpass filtering characteristics with sharp lower transition knee. Accordingly, an LC equivalent circuit is proposed. A cascaded band-accept and band-reject filter is proposed for designing a wideband bandpass filter. The bandwidth and centre frequency of the bandpass filter can be varied by choosing different set of DGS dimensions.

Performance Enhancement of Microstrip Open Loop Resonator Band Pass Filter By Defected Ground structures

A selective bandpass filter is presented by using a pairs of open loop resonators, each has a perimeter about half-wavelength. For the improvement of bandwidth, we have used a DGS under coupled area. A prototype filter circuit of center frequency at 1.8 GHz has been fabricated with PTFE substrate. Measured result shows bandwidth of 200 MHz with insertion loss of 0.2 dB at center frequency of 1.95 GHz. We have used defected ground structures under feed lines for extra stopband rejection mode to the 2nd and 3rd harmonics of the filter with attenuation losses over than -25 dB, without affecting the center frequency and insertion loss of the originally designed filter.

SIW based compact and dual-band equilateral triangular antennas

Abstract In this paper, a substrate integrated waveguide (SIW)-based equilateral compact and dual band triangular antennas have been proposed. A SIW-based coaxial fed equilateral triangular antenna has been initially considered. The antenna is found to resonate at 5.28 GHz corresponding to U-NII-2 WLAN band. Two sides of the said antenna are made perfect electrical conductor wall with array of metallic vias and the third side is kept open which acts like a perfect magnetic conductor (PMC) wall. A single slit has been introduced on the PMC wall of the initial antenna which causes a decrease in resonating frequency from 5.28 to 4.29 GHz. The antenna has been further miniaturized by introducing another parallel extra slit on the PMC wall which leads to a decrease in the resonating frequency to 3.3 GHz. The former antenna with single slit is found to exhibit 33% miniaturization while the latter with double slits reflects 56% miniaturization. By changing the coaxial feed location of the initial antenna at off-axis position, a dual band antenna has been realized. The dual band antenna is found to excite both TE101 and TE202 modes efficiently with corresponding resonating frequencies at 4.18 and 8.85 GHz. The prototypes have been fabricated on Arlon AD270 substrate and simulated results are compared with the measured ones. A good agreement has been observed between the simulated and measured results.

Mutual Coupling Reduction of a Dual-Frequency Microstrip Antenna Array by Using U-Shaped DGS and Inverted U-Shaped Microstrip Resonator

A compact U-shaped defective ground structure (DGS) and an inverted U-shaped resonator are introduced in order to reduce the mutual coupling (MC) between two slotted microstrip antennas at two difierent resonance frequencies. The proposed DGS and resonator have the same electrical length and both are placed in between two patch antennas, as a technique to suppress the occurrence of MC at two difierent frequency bands. The DGS and the resonator ofier stop bands at 2.45GHz and 4.5GHz respectively. Simulated results show a reduction in MC of 20dB at 2.45GHz band and 1dB at 4.5GHz band. We have developed experimental models that have proved this concept of MC reduction. Finally, the in∞uence of other parameters of the proposed antenna at the presence of the combination of DGS and resonator in the array system has been studied. Prototype antennas for difierent combinations of DGS and resonator and two-element array integrated with DGS and resonator have been fabricated, measured and the idea has been verifled. A good agreement is observed between measured and the simulated results.

Performance Enhancement of a Dual-Band Monopole Antenna by Using a Frequency-Selective Surface-Based Corner Reflector

In this paper, we enhance the performance of a dual-band wire monopole antenna operating at 3 and 5.5 GHz by using a frequency-selective surface (FSS)-based corner reflector. In the proposed design, two reflective FSS screens resonating at 5.5 GHz are placed at an angle of 90° and kept at a specific distance from the antenna. The reflector improves the impedance bandwidth (-10 dB) of the antenna from 20% to 44%, as well as its gain, thereby leading to more directive radiation at 5.5 GHz while maintaining omnidirectional radiation at around 3 GHz. A theoretical study is carried out and presented to estimate the enhancement in the electric field of the composite structure in the desired frequency band compared with the absence of a corner reflector in far field. A significant improvement of 8-10 dBi in antenna gain is achieved over 4.5-6.5 GHz; this is maintained at around 12.5 dBi, with a variation of ±1.5 dBi. Experimental measurements are provided in each case. The proposed design can be used as an omnidirectional radiator at around 3 GHz and as a high-gain directional radiator in the 4.5-6.5-GHz band.

High Gain Circularly Polarized Rectangular Dielectric Resonator Antenna Array with Helical - Like Exciter

A novel (2£2) high gain circularly polarized rectangular dielectric resonator antenna array integrated with helical-like exciter is proposed. The array ofiers a maximum gain of 12.9dBi at the operating frequency. The circular polarization is obtained by incorporating helical-like exciter in the array structure. A prototype of the proposed conflguration integrated with helical-like exciter has been fabricated and tested, and the idea has been verifled. A good agreement has been obtained between the measured and simulated results.

Frequency-Dependent Directive Radiation of Monopole-Dielectric Resonator Antenna Using a Conformal Frequency Selective Surface

Development of a conformal frequency selective surface (FSS) for radiation diversity of hybrid monopole-dielectric resonator antenna has been demonstrated in this paper. In the proposed method, a planar FSS screen with meandered unit cell is designed to be reflective at 5 GHz followed by its mapping on a cylindrical surface of flexible dielectric material. The proposed conformal reflector when kept at a specific distance from the radiating element improves the bandwidth of the antenna from 26.8% to 53.67% in 4–6 GHz band. A significant enhancement of 5–6 dBi in gain is also achieved over this band. Gain of the antenna with reflector is maintained around 9.5 dBi with a variation of ±1.5 dB. On the other hand, omni-directional radiation of the antenna is maintained at an upper band of 7–9 GHz. Simulations have been performed using ANSYS High Frequency Structure Simulator (HFSS). Experimental measurements of the fabricated prototype have been provided. The proposed design is useful to achieve pattern diversity in multiband antenna system.

A wearable button antenna with FSS superstrate for WLAN health care applications

In this article a compact miniaturized wearable antenna with the appearance of a button on clothing for WLAN applications is presented. The radiating elements of the antenna are made of copper sheet, whilst a transparent acrylic fiber sheet material is used as substrate and fed by a coaxial line through the ground plane. The proposed antenna is simulated by Ansoft HFSS FEM based EM simulator and has been optimized to operate within the WLAN frequency bands with centre frequency of 5.25 GHz (5250-5850 MHz). A split ring-shaped slot based frequency selective surface (FSS) is designed to enhance the gain of the proposed antenna. The peak gain of the antenna is enhanced from 2.1dBi to 5.1dBi with the superstrate along with a bandwidth enhancement of 290MHz. The antenna gets miniaturized around 34% by the slit.

High Gain Circularly-Polarized Dielectric Resonator Antenna Array with Helical Exciter

A novel (2£2) high-gain circularly-polarized cylindrical dielectric resonator antenna array integrated with helical exciter is proposed. The array ofiers a maximum gain of 13.8dBi at the operating frequency. The circular polarization is obtained by incorporating helical exciter in the array structure. A prototype of the proposed conflguration integrated with helical exciter has been fabricated, tested and the idea has been verifled. A good agreement has been obtained between the measured and the simulated results.

Design of SIW series fed cylindrical dielectric resonator linear array antenna

A wideband cylindrical dielectric resonator antenna (DRA) linear array fed by substrate integrated waveguide (SIW) is proposed in this paper. The array antenna is designed to operate at 14.1-14.7 GHz with 5.1% bandwidth. The resonant frequency of slots and the resonant frequency of DRAs are merged to achieve wideband characteristics. But, total gain decreases when broadband characteristics is achieved using SIW-fed dielectric resonator antenna(DRA) array compared to that of SIW-fed slot antenna array. The proposed antenna has very low level of cross-polarization and maximum gain 7.14 dBi for both E-plane and H-plane is observed.