This paper reports the theoretical and experimental investigations on the strain sensing effect of a two dimensions (2D) photonic crystal (PhC) nanocavity resonator. By using the finite element method (FEM) and finite difference time domain (FDTD) simulations, the strain sensitivity of a high quality factor PhC nanocavity was calculated. Linear relationships between the applied strain and the shift in the resonant wavelength of the cavity were obtained. A single-defect silicon (Si) PhC cavity was fabricated, and measurements of the strain sensitivity were performed. Good agreement between the experimental and simulation results was observed.

This paper proposes an effective technique to enhance the isolation in a closely-spaced multiple-input multipleoutput (MIMO) antenna system. In the proposed design, microstrip patches are closely arranged in the H- and E-plane configurations with an extremely small edge-to-edge spacing of 0.016λ at the center operating frequency. The self-decoupling effect is realized by exciting the coupling patch with a mode that is orthogonal to the operating mode of the radiating element. This is achieved by creating a meander patch edge such that the orthogonal TM ₀₂ mode has the same resonance frequency of the fundamental TM ₁₀ mode. Accordingly, very high isolation among MIMO elements is obtained without the use of any decoupling structure. Measurements of a fabricated MIMO antenna demonstrate the feasibility of the proposed concept. The prototype has good matching performance and high isolation of 35 dB at the center operating frequency of 4.8 GHz, which is about 29 dB improvement in comparison with the coupled MIMO antenna. Besides, the proposed self-decoupling method can work effectively in multi-port H-plane coupled MIMO array.

We present a micromachined gas sensor which can detect dilute NH3 gas at ppb (parts per billion) concentration based on chemoresistive effect of semiconducting tungsten trioxide (WO3). The sensor structure consists of a poly-Si diaphragm-heater suspended on four tiny beams, which are connected to a frame with overall chip size of 1ױװ.3 mm3. Thanks to the diaphragm-beam structure, the power loss due to thermal conduction effect decreases and uniformed temperature on whole diaphragm is obtained. The sensor has been fabricated and tested. Thermal efficiency of the heater was measured to be 10 oC/mW. The optimal working temperature was found to be around 300 oC, and the sensor could detect NH3 gas at ppb concentration in a background of wet air. The nano-gap effect of the interdigitated electrodes in improvement of the sensitivity was also confirmed. Our estimation based on the measurement results and system noise showed a limit-of-detection of NH3 gas could be down to 2.5 ppb concentration.Full Tex