Nagendra Kushwaha

Design of Slotted Ground Hexagonal Microstrip Patch Antenna and Gain Improvement with FSS Screen

Three hexagonal patch antennas are designed for circular polarization and experimentally validated. These antennas are labeled; simple hexagonal patch, hexagonal patch with slotted ground and hexagonal patch with parasitic element. The measured impedance bandwidths of the three antennas are 2% for the simple patch, 5.2% for the patch with slotted ground and 6.35% for the antenna with parasitic element. The axial ratio (measured) obtained is 4.73% for the patch with slotted ground and 3.33% for the hexagonal patch antenna with parasitic element. The measured radiation patterns of these antennas are found to be in good agreement with the simulated radiation patterns. The average gain of all the three antennas is also evaluated. A frequency selective surface (FSS) is proposed with dimensions smaller than that of a conventional FSS structure. The measured gain improvement with the proposed FSS is around 3dB in the operating band.

Study of different shape Electromagnetic Band Gap (EBG) structures for single and dual band applications

In this paper, single and dual band EBG structures for wider bandwidth are proposed. In each of the discussed EBGs, a metallic patch of regular geometry is chosen for the unit element. The patch is further modified by cutting slots to get extra inductance and capacitance which results into lower cut-off frequency and larger bandwidth. The proposed EBG structures are compared with the standard mushroom type EBG with respect to surface wave attenuation. The -20 dB cut-off frequencies and bandwidths of the various EBGs are compared. The effect of unit element size, gap between unit elements and via diameter on the transmission response is presented. Among the discussed EBGs, the swastika type structure is compact, single band and has wider bandwidth. The square patch with a single disconnected loop type slot EBG and the Fractal EBG are dual band. While square patch is more compact, the fractal EBG has wider bandwidth. All the EBGs can be useful in the design of antenna and other microwave circuits.

AN UWB FRACTAL ANTENNA WITH DEFECTED GROUND STRUCTURE AND SWASTIKA SHAPE ELECTROMAGNETIC BAND GAP

In this paper, an ultra wideband antenna employing a defected ground structure is presented. The radiating element is a circular patch on which a fractal based geometry is inscribed in the form of slots and excited by a tapered feed-line for impedance matching. The antenna has an impedance bandwidth of 8.2GHz (117% at centre frequency of 7GHz) and a peak gain around 6dB. To improve the impedance bandwidth and gain, a Swastika shape Electromagnetic band gap (EBG) structure is proposed. The unit cell of the proposed EBG has a compact size of 3mm£3mm and is obtained by introducing discontinuities in the outer ring of the Cross-Hair type EBG. The stop band (i20dB) achieved with this EBG is 3.6GHz (7.5GHz{11.1GHz) which is 1.6GHz more than that achieved by a standard mushroom- type EBG of the same size and same number of elements. After application of the proposed EBG, there is an improvement of 12% in the impedance bandwidth while the peak gain increases by about 2{ 3dB. The radiation of the antenna shows a dumb-bell shaped pattern in the E-plane and Omni-directional pattern in the H-plane. All the measured results are in good agreement with simulated results.

Design and Analysis of New Compact UWB Frequency Selective Surface and its Equivalent Circuit

A compact, low proflle, dual polarized, ultra wideband, frequency selective surface is proposed. It is designed by using two similar metallic array structures separated by dielectric material FR4. The simulated re∞ection bandwidth (with transmission < i20dB) for TE incident wave is 8GHz from 2.87GHz to 10.87GHz corresponds to 116%. The unit cell dimension and periodicity are of the order of 0:37‚ at the centre frequency. The overall thickness of the proposed FSS is 1.8mm. The proposed FSS has higher order of band-stop response and good angular stability. The measured transmission response of FSS is very close to simulated response. Design expressions for the resonance frequencies are proposed, and the calculated results are found to be in good agreement with the simulated ones. Finally, a parametric analysis of the proposed FSS is presented.

Design and analysis of CPW-fed wideband circularly polarized antenna for modern communication systems

A novel design for wideband circularly polarized antenna is presented. The proposed antenna is a coplanar waveguide structure. The slot in the ground plane is rectangular and placed asymmetric. The circular polarization is achieved by using a modified L-shape radiating patch and by adding inverted L-shaped strip at one corner. Axial ratio bandwidth (ARBW) of the antenna is greatly enhanced by connecting one end of the L-shaped patch to the ground via a slit and cutting additional slots in the ground plane. The measured impedance bandwidth and 3 dB ARBW is 3.4 GHz (2.2–5.6 GHz) and 1.97 GHz (2.2–4.17 GHz), respectively, which can cover WLAN (2.4 GHz band), RFID reader (2.45 GHz band), WiMAX (3.2–3.7 GHz band) other wireless communication applications. The average measured boresight gain is 3–4 dBi. The time domain analysis of the antenna is also performed. The measured group delay is nearly constant in the operating band. The system fidelity factor of the antenna is also measured for different azimuth angles.

Design of ultra wideband hexagonal patch slot antenna for high-gain wireless applications

In this paper, a CPW-fed modified rectangular slot antenna with ultra wideband characteristics is proposed. The slot has on one of its sides, a rectangular extension of smaller size which introduces asymmetry in the design. The CPW feed is terminated on a hexagonal-shape patch which protrudes into the slot centre and excites the slot. The antenna exhibits an impedance bandwidth of 134% at the centre frequency of 8.8 GHz. The radiation patterns of the antenna are simulated and measured and found to have omni-directional characteristics in the H-plane. In order to increase the gain of the antenna and make it directional, a multi-layer FSS is designed and fabricated. By implementing the FSS, the gain is enhanced by 3–4 dBi throughout the band. To verify the time domain performance of the antenna with and without the FSS, the group delay and fidelity factors (FF) are calculated. While the variations in the group delay are seen to be minimal, the FF are found to be within acceptable limits thus indicating good time domain characteristics with no significant loss of information in the received pulse.

Design and analysis of multi-band filters using slot loaded stepped impedance resonators

Two multi-band fllters operating in the 1{10GHz range are designed, analytically studied and experimentally verifled. The fllters are developed by making modiflcations to a series capacitively coupled, microstrip line fllter. The middle section of the microstrip line is widened and rectangular slots are etched on it. Widening increases the efiective dielectric constant which helps in miniaturization of the circuit. On the other hand, the rectangular slot cause various longitudinal, transverse and slot mode resonances to be excited resulting in multi-band operation. An extensive parametric analysis with respect to the physical parameters of the fllter leading to the development of a semi-empirical model is presented. The model can be used to predict the resonant frequencies with su-cient accuracy for a given geometrical structure. The model also predicts the limit of miniaturization achievable with the presented design. The proposed fllters besides being compact have good out of band rejection and are easy to design and fabricate without the need of additional matching circuits.

An UWB dual polarized microstrip fed L-shape slot antenna

In this paper, a microstrip fed, L-shape slot antenna for dual polarization is proposed. The two arms of the slot generate electric fields of orthogonal polarizations. By properly sectioning the slot and the feed line, ultra wideband (UWB) behavior is obtained. The measured impedance bandwidth ( S 11

On the design of elliptical shape fractal antenna for UWB applications

In this paper, a compact elliptical shaped UWB fractal antenna is proposed. The excitation is done with a double stepped coplanar waveguide feed. The frequency characteristics of proposed antenna consist of ultra wideband properties in the range 2.85 GHz to 15 GHz corresponding to the impedance bandwidth of 136.13%. The measured radiation patterns are bidirectional in E-plane and Omni-directional in H-plane. The simulated peak gain is 5dBi at 10.6 GHz. The areas of applications are modern wireless communication, penetrating radar, vehicular radar, and medical imaging.

Design of dual band and wideband circularly polarised slot antenna for wireless applications

ABSTRACT In this paper, two circularly polarised (CP) antennas are proposed. One is dual band CP (DBCP) while the other is wideband CP (WBCP). Both the slot antennas are coplanar waveguide-fed corner truncated structure with an L-shaped radiating patch. The CP bandwidth is significantly improved by connecting one end of the L-shaped patch to the ground plane which also resulted in miniaturisation of the antenna with a size of 48 × 43 mm. DBCP is generated by adding an extra rectangular stub to the ground plane while WBCP by cutting two additional slots in the ground plane. The dual band antenna has a measured impedance bandwidths (S11 < −10 dB) of 34% (2.2–3.1 GHz) and 42% (4.6–7.1 GHz) while the corresponding 3 dB axial ratio bandwidths (ARBWs) are 34% (2.2–3.1 GHz) and 28.6% (4.8–6.4 GHz). The measured impedance bandwidth and ARBW of the wideband antenna are 102% (2.2–6.8 GHz) and 93% (2.3–6.3 GHz), respectively.