Zhang Binzhen

Flexible dual-band band-stop metamaterials filter for the terahertz region

In this paper, we present a THZ MMs filter with two independent stop-bands based on periodic metallic resonant structures patterned on the top of a flexible polyimide wafer. The optimized geometry parameters were obtained by numerous simulations using full wave finite integration technology of CST 2015. The resonant frequencies of the filter were 126.32 GHZ and 177.32 GHZ with 3-dB bandwidths of 19.3 GHZ and 9.1 GHZ, respectively. The S21 parameters can reach to −47.38 dB and −56.69 dB corresponding to two resonant peaks, which indicate the excellent stop-band performance. The MMs filter in our design is insensitive to the polarization angle of the incident EM waves due to the symmetrical characteristic of the proposed resonance structure. In order to intensively understand the transmission performance of the proposed MMs filter, a large number of simulations were performed based on the different permittivity, period of the unit cell, dielectric thickness, and geometric dimensions. The electric field and surface current distributions were analyzed to understand the mechanism of the EM wave transmission. The proposed MMs filter was fabricated using a surface micromachining process and tested using a THZ-TDS system. Measured terahertz transmission responses of the proposed MMs dual-band band-stop filter have reasonable correspondence with those from simulations.

Temperature Effects of Piezoresistance Coefficient

A higher sensitivity is achieved by making use of a high electron mobility transistor (HEMT) as the piezoresistive device. The temperature dependence on the electromechanical coupling effect of accelerometers is reported. The current in the structure of our study decreases at the rate of 3.15 mA/°C with the temperature going up at every region, and piezoresistance coefficient decreases because of the shift of energy and expansion of lattice.