No abstract

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 25 mm is investigated. In this configuration, mutual coupling is < −5 dB and < −10 dB over 2 GHz-3 GHz and 3 GHz-10.6 GHz, respectively. Mutual coupling is reduced by using 90 • angularly separated semicircular monopoles. With semicircular configuration, 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 modified and extended between the two elements to improve the impedance bandwidth and mutual coupling. Impedance bandwidth from 2.0 GHz-10.6 GHz with S 21 < −20 dB and −14 dB is achieved over 3.1 GHz-10.6 GHz and 2.0-3.1 GHz respectively. The antenna is fabricated using 46 mm × 37 mm RT Duroid substrate. Measurement results agree with the simulation ones. Radiation patterns are stable, and correlation coefficient is < 0.02 over 2.0-10.6 GHz.

A cross configuration of directional Ultra Wideband (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 20dB, with an impedance bandwidth (VSWR < 2) 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.

Abstract-A novel half Hemispherical Dielectric Resonator Antenna (HDRA) with an array of slots has been designed. The dielectric material used is Rogers TMM10, which is a ceramic thermoset polymer composite material having a dielectric constant of ε r = 9.2. Periodic holes lower down the Q factor of the antenna and hence enhance the impedance bandwidth. The measured value of the 10 dB bandwidth is close to 1 GHz (∼17.74%). The mode investigated is a TM 101 like mode. Further, the effect of increasing the probe length on the resonance and the radiation pattern is also studied. As the probe length is increased, a shift in the resonant frequency is observed and the Dielectric Resonator Antenna (DRA) behaves as a monopole antenna loaded with the DRA. The experimental results confirm that a wide bandwidth of 1.3 GHz (∼29%) with a high gain of 7.2 dBi can be obtained. The radiation pattern of such an antenna is directive in nature.

Abstract-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 1.6 mm 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 × 24 mm 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., 3.5 GHz-12 GHz frequency band. The radiation pattern produced by the proposed antenna is approximately omnidirectional with inphase excitation of Surface waves resulting in less cross-polarization level (less than 20 dB) compared to its co-polar component for the entire impedance band width. The maximum measured gain for the fabricated antenna is around 6.27 dBi with an average efficiency of above 90% throughout the bandwidth. A linear phase response (phase of S 21 ) accompanied by a constant group delay of 1 ns throughout the measured bandwidth makes the proposed antenna a good candidate for UWB applications.