A fluid switch is proposed for a frequency-agile Vivaldi antenna whose operating frequency band can be switched between two selected bands. A study of various ionized solutions of different concentrations is performed. A 2 mol KCl solution is selected as the fluid for the switch because of its relatively good properties in conductivity, relative permittivity, and loss tangent. The fluid-switched reconfigurable Vivaldi antenna can function well between two user-defined operating bands: 3.2 and 4.5 GHz with stable measured gain of 11 dBi in both bands and an isolation of 15 dB. This reconfigurable antenna demonstrates that a lowcost fluid switch may be an alternative device for reconfigurable antenna designs providing more flexibility.Index Terms-Ionized solutions, reconfigurable antennas.

In this letter, a dual band and dual polarization capacitive-fed slot patch antenna is investigated. The proposed antenna can operate at 1.575 GHz for Global Positioning System and 2.4 GHz for Wi-Fi system with the corresponding polarizations. A 90° hybrid coupler chip was used to excite the right hand circular polarization required for optimum GPS performance. For the high frequency band, a pair of linearly polarized arc-shaped slots radiating at 2.4 GHz are embedded in the circular patch. The operating bandwidths of the antenna are enhanced by the multi-layered geometry, and the capacitive disks feed points placed between the substrate layers. The measured impedance bandwidths at the lower and high bands are 320 MHz and 230 MHz respectively. The measured 3dB axial ratio bandwidth is 120 MHz.Index Terms-slot patch antenna, GPS, Wi-Fi, dualpolarization, capacitive feeding.

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A low-profile orthogonally linearly tripolarized antenna consisting of two thick-slot antennas and one half-mode substrate integrated waveguide (HMSIW) antenna has been investigated. The two thick-slot antennas radiate -and -directional linearly polarized waves, while the HMSIW antenna contributes to the -directional polarized wave. The low-profile geometry is achieved by utilizing the HMSIW antenna. Isolations between the three antennas measured are lower than 20 dB, which means that the proposed antenna geometry provides good diversity gain and the channel capacity can be increased by as much as three times.Index Terms-Mobile antennas, multiple-input-multiple-output (MIMO) systems, mutual coupling, polarization diversity.

This paper presents the latest development of the hybrid microwave-optical thermoregulation monitor for the muscle. It is capable of warming the muscle and measuring the subsequent blood volume changes, using a novel microwave applicator with integrated optical probes. The challenge is to measure the thermoregulation response in deep tissue while minimizing any effect from the skin layer. We have introduced a skin cooling device, an additional integrated optical Laser Doppler flow monitoring probe and a temperature sensor to measure skin blood flow and temperature, respectively. The result shows that skin cooling is essential to minimize skin flow changes during microwave warming. The hybrid probe was placed on a human thigh to measure oxy/deoxy/total haemoglobin concentration changes (ΔHbO₂/ΔHHb/ΔHbT), skin flux and temperature upon microwave warming. Without skin cooling, the skin temperature was elevated by 4 °C and both ΔHbO₂/ΔHbT and skin flux increased, showing microwave warming occurring in both the skin and muscle. With skin cooling, the skin temperature was kept relatively constant. While ΔHbO₂/ΔHbT increased, the skin flux was relatively stable, showing a preferential microwave warming in the muscle, rather than the skin.