A. G. Koutinos

Dual-Band Fractal Semi-Printed Element Antenna Arrays for MIMO Applications

Novel dual-element antenna arrays suitable for small devices of multiple-input-multiple-output (MIMO) applications have been designed and fabricated. The antenna elements have semi-printed structure, are fractally shaped, and operate in ISM (2.4-2.489 GHz) band as well as between 5 and 6 GHz. Although the size of the designed antenna prototypes is small and the elements are positioned too close to each other, correlation coefficients lower than 0.1 and satisfactory levels of mean effective gain have been obtained.

A dual-feed rectangular patch antenna for bandwidth enhancement

A novel feeding mechanism for a rectangular patch antenna is introduced. A phase shift caused by path inequality between two possible symmetrical feeding points is introduced, in order to achieve wideband operation at the 2.4 GHz WiFi band. The idea is to create two separate resonances, by exploiting a phase shift in one of the feeds. Simultaneously activating the two feeds yields to an envelope formed by the separate resonances. This leads to a fractional bandwidth enhancement from 0.9% to about 1.8%. The feeding mechanism is furthermore folded on the back side of the patch, thus constructing an appropriate design for cellular applications, reducing its size. This configuration leads to an even better fractional bandwidth enhancement (53.07 MHz, i.e. 2.18%). The results are verified in terms of Return Loss, Input Impedance, VSWR and Antenna and Radiation Efficiency, all exhibiting satisfactory behaviour.

A novel quadruple-fed rectangular patch antenna with improved bandwidth performance

A novel quadruple feeding mechanism for a rectangular patch antenna is proposed. A successive phase shift caused by path inequality between four possible symmetrical feeding points is introduced, in order to achieve wideband operation at the 2 GHz frequency band. This work is an extension to the idea of acquiring a pair of resonances and forcing them to behave in a consolidated way. This concept is verified in previous work and is herein stretched to the limit that a rectangular patch could provide speaking in terms of symmetry, i.e. using four feeding points. The proposed antenna exhibits a fractional bandwidth of 3.46 %, almost four times as much as the conventional single-fed patch does. Furthermore, the antenna presents circular polarization and an elevationuniform radiation pattern. VSWR, Impedance matching as well as Antenna and Radiation Efficiency are also presented and annotated.

Bandwidth enhancement of a supershape patch antenna using multiple feeding technique

The technique of multiple points feeding in order to achieve improved bandwidth performance is here exploited and used to feed a supershape structured radiator. The achieved operating bandwidth, is an important advancement compared to the performance of the usual, single fed and regularly shaped patch antennas. The proposed antenna operates from 2.5 to 3.9 GHz with linear polarization and its behavior is investigated in terms of Return Loss, VSWR, input impedance, radiation pattern, electric field and efficiency.

Enhanced bandwidth 4×4 antenna array consisting of E-shaped elements

Regarding the increasing demand for bandwidth, as well as the need for reliable communications in terms of gain and polarization, an antenna array consisting of 16 E-shaped elements is proposed. The frequency band, in which the array operates, is allocated for aeronautical and maritime radio-navigation, radiolocation, satellite-conducted earth exploration and fixed satellite communications, namely from 9 to 11 GHz.

Polarization diversity performance of mobile terminals in multipath environment using MIMO channel characterization

Polarization diversity, a technique where different polarizations are used to provide diversity, has proved to be an efficient way of reducing the size and numbers of the antennas needed for a mobile terminal working in modern wireless networks. This method does not require any extra bandwidth or more space for physical separations between the antennas. It uses only one dual-polarized antenna and it takes advantage of the multipath propagation characteristics to receive separate uncorrelated signals and reduce fading. The applicability of polarization diversity for mobile terminals in a multipath environment can be evaluated using as figures of merit the signal cross correlation and cross polarization discrimination (XPD), while the effectiveness of the diversity system can be measured by diversity gain. Since the XPD may be crucial to polarization diversity, the antenna radiation patterns should always include co- and cross-polar field components. In a multipath rich environment, regardless of the original polarization of radiated waves, multiple reflections depolarize radio waves and couple some energy into the orthogonal polarized wave. As a result, both orthogonal wave components are received by the antenna of the mobile terminal.

Dual - feed rectangular patch antenna for satellite applications with increased bandwidth requirements

A feeding mechanism for a rectangular patch is proposed, leading to significant bandwidth augmentation. The bands where resonances are observed are allocated for fixed, mobile and satellite communications as well as radio astronomy and space research, according to European and U.S. frequency allocation charts.