Shilpa Kharche

MIMO Antenna for Bluetooth, Wi-Fi, Wi-MAX and UWB Applications

A Multiple Input Multiple Output (MIMO) antenna consisting of two 90 - angularly separated semicircular monopoles with steps for Bluetooth, Wi-Fi, Wi-MAX and UWB applications is proposed. Initially, an array of two coplanar circular monopoles with element separation of 25mm is investigated. In this conflguration, mutual coupling is < i5dB and < i10dB over 2GHz{3GHz and 3GHz{10.6GHz, respectively. Mutual coupling is reduced by using 90 - angularly separated semicircular monopoles. With semicircular conflguration, though the mutual coupling is improved, impedance bandwidth is reduced due to reduction in electrical length. A step like structure is introduced in the semicircular monopoles, and ground plane is modifled and extended between the two elements to improve the impedance bandwidth and mutual coupling. Impedance bandwidth from 2.0GHz{10.6GHz with S21 < i20dB and i14dB is achieved over 3.1GHz{10.6GHz and 2.0{3.1GHz respectively. The antenna is fabricated using 46mm £ 37mm RT Duroid substrate. Measurement results agree with the simulation ones. Radiation patterns are stable, and correlation coe-cient is < 0:02 over 2.0{10.6GHz.

HIGH GAIN AND LOW CROSS-POLAR COMPACT PRINTED ELLIPTICAL MONOPOLE UWB ANTENNA LOADED WITH PARTIAL GROUND AND PARASITIC PATCHES

In this paper a low cost, high gain, low cross-polar and compact edge feed printed elliptical antenna with a partial ground plane and parasitic patches is proposed and investigated. The proposed antenna is fabricated on a 1.6mm thick FR4 substrate with dielectric constant of 4.4 and loss tangent of 0.025. The total planar area of the proposed antenna (L £ W) is 28 £ 24mm 2 . Both the simulated and experimental result shows that the proposed antenna provides a frequency range compatible with the ultra-wideband (UWB) standard, i.e., 3.5GHz{12GHz frequency band. The radiation pattern produced by the proposed antenna is approximately omnidirectional with in- phase excitation of Surface waves resulting in less cross-polarization level (less than 20dB) compared to its co-polar component for the entire impedance band width. The maximum measured gain for the fabricated antenna is around 6.27dBi with an average e-ciency of above 90% throughout the bandwidth. A linear phase response (phase of S21) accompanied by a constant group delay of 1ns throughout the measured bandwidth makes the proposed antenna a good candidate for UWB applications.

Cross-Configured Directional UWB Antennas for Multidirectional Pattern Diversity Characteristics

A cross configuration of directional ultrawideband (UWB) antennas for multidirectional pattern diversity characteristics is presented. Initially, a printed UWB circular monopole having an asymmetric curve shaped CPW feed is designed as a base antenna for obtaining a directional radiation pattern, direction of which remains fairly same for the entire UWB. This base antenna is attached to similar antennas, in a four element cross-configuration to achieve multidirectional pattern diversity characteristics. The proposed structure provides high inter-element isolation of more than 20 dB, with an impedance bandwidth of 19.7 GHz, i.e., 1.3 GHz to 20 GHz. Transmission and diversity characteristics of the proposed antenna are analyzed. Good agreement between simulated and measured results indicates that the proposed antenna is suitable for UWB pattern diversity applications.

BLUETOOTH/UWB DUAL-BAND PLANAR DIVERSITY ANTENNA WITH WiMAX AND WLAN BAND-NOTCH CHARACTERISTICS

In this paper, a stage wise realization of compact Bluetooth | UWB dual-band diversity antenna with WiMAX and WLAN band-notch characteristics is presented. The proposed structure consists of two co-planar semicircular dual band-notch monopole antennas, mounted with planar spiral. Individual antenna conflguration provides an impedance bandwidth (VSWR < 2) for dual- band i.e., both Bluetooth and UWB bands. For dual band-notch characteristic, two sets of spirals are capacitively coupled with the feed line of antenna. This conflguration provides band-notch (VSWR < 2) for WiMAX i.e., (3.3{3.6GHz) and WLAN (5.13{5.85GHz) bands. For enhancing reception capabilities of the proposed structure, twin coplanar antennas are used to fulflll diversity requirements. However, due to coplanar and close proximity to each other, there is high possibility of mutual coupling between coplanar antenna elements. To address the mutual coupling between elements, cross-strip variable- sized frequency selective structures are used. Antenna diversity of the proposed structure is validated by measuring radiation pattern characteristic and envelop co-relation factor (ECC). A good agreement between measured and simulated responses ensures that the proposed diversity antenna can be used for interference free Bluetooth/UWB dual-band applications.

Parallel metal plated high gain ultra wideband antenna with unidirectional radiation pattern

In this paper high gain parallel metal plated circular monopole UWB antenna with a planar reflector is proposed. The antenna is fabricated using 0.5 mm thick copper plate. Reflector of 50 mm × 60 mm is placed 10 mm below the antenna structure. VSWR = 2 and gain variation of 7.5-10.2 dBi are obtained over 4.1-10.6 GHz. The antenna offers unidirectional radiation patterns in both the planes with cross polarization <; -20dB and front to back ratio > 15 dB. The antenna offers nearly constant group delay. The structure is fabricated and tested. Measured results agree with simulation results.

Mutual coupling reduction by using tilted variable length srr like structure in uwb mimo antennas

In this paper mutual coupling reduction between two elements of ultra-wide band (UWB) MIMO antenna by using a tilted SRR like structure with variable length is proposed. The antenna consists of two modified elliptical shaped monopole antennas designed using 0.787 mm thick RT duroid. Near field distribution of the antenna structure is studied to understand the isolation mechanism. Tilted variable length SRR like structure is used to achieve S11 and S21 less than −10 dB and −22 dB respectively over 3.1–10.6 GHz. The proposed structure has a good diversity performance, nearly constant group delay and transfer function variation within 11 dB over UWB.

Broadband spiral diversityantenna with dielectric loading

In this paper, dielectric loading and scaling is used to achieve broadband circular polarization with compact size. The spirals are arranged in opposite configuration sense which is used for detection of circularly-polarized waves of either polarization sense. A wide band balun is designed to feed the antenna structure. Antenna is enclosed in elliptical shape housing. A broad impedance and AR bandwidth is obtained.

Mutual coupling reduction using shorting posts in UWB MIMO antennas

A multiple input multiple output (MIMO) antenna consisting of two hybrid shaped monopoles for UWB applications is presented. In the proposed antenna, a pair of rectangular strips terminated with shorting posts is used to achieve isolation ≥ 20 dB over UWB. The variations in group delay and transfer-function response are within 1 ns and 13 dB respectively. The envelope correlation coefficient < 0.05 over 3.1–10.6 GHz indicate that the proposed antenna is suitable for UWB MIMO applications.

Symmetric/asymmetric CPW feed compact UWB antenna with polarization diversity characteristic

A compact symmetric/asymmetric CPW feed UWB antenna with polarization diversity characteristic is presented. The proposed structure consists of two orthogonally placed UWB antennas. One of the antenna elements in the proposed structure is feed with symmetric CPW feed while another antenna is feed with asymmetric CPW feed. The proposed feeding techniques minimize the mutual coupling (≤ 20dB) between the antenna elements. The proposed structure provides an impedance bandwidth of more than 10 GHz, which covers Bluetooth/Wi-Fi bands along with UWB bandwidth. The transmission and diversity characteristics of the proposed antenna are measured and results are reported in terms of group-delay, transfer-function response, and Envelop-Correlation coefficient response. A good agreement between simulated and measured results shows that the proposed antenna can be used for UWB diversity application.

Ultra Wideband printed monopole antenna with curve shaped extended asymmetric CPW ground plane for stable unidirectional radiation pattern

This paper presents a CPW feed Ultra Wideband (UWB) printed circular monopole antenna, with a curved shaped extended asymmetric CPW ground plane for stable-unidirectional radiation pattern. Initially, the ground plane of a CPW feed planar monopole is elliptically tapered to enhanced its UWB bandwidth. This elliptically tapered ground plane is further modified in to a curve shape similar to circular monopole for achieving unidirectional radiation pattern. Simulated and measured results show that proposed antenna achieves an impedance bandwidth (VSWR<;2) of 20 GHz i.e. from 1GHz to 20 GHz, which covers all lower narrow microwave bands along with UWB bandwidth. Apart from UWB bandwidth, measured radiation patterns show that for complete impedance bandwidth, radiation patterns of proposed antenna are unidirectional (nearly end-fire) with high stability. The measured antenna gain and group delay also depicts stability for complete UWB bandwidth.