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In this Letter, a differential piezoresitive wind speed sensor on a flexible substrate is proposed. Two piezoresistors with the same size are fabricated on the front surface and back surface of the substrate, respectively. When the wind blows towards the device, the flexible substrate is bent, increasing the resistance on the front surface and reducing that on the back surface. The proposed sensor is fabricated on a polyethylene terephthalate substrate. Wind speed experiments are performed in the wind tunnel and the results demonstrate that the sensor can measure the wind speed up to about 20 m/s. [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents an X-band Wilkinson power divider which is completely compatible with GaAs monolithic microwave integrated circuit (MMIC). The novelty is that, GaAs is chosen for the realization for substrate because of its excellent microwave performance, and Au is used to fabricate transmission lines and air bridges due to its good electric properties. The measured return loss of port 1 is about −32 dB at the center frequency of 9 GHz and less than −16 dB over X-band. The insertion loss of port 2 and 3 is close to 3.3 dB at 8-12 GHz. The measured bandwidth for which the input return loss is less than −20 dB is about 3.2 GHz. For the miniaturized power divider, the measured return loss of port 1 is about −23 dB at the center frequency of 11 GHz and less than −13 dB over the band of 8-12 GHz. The measured insertion loss of port 2 and 3 is close to 3.5 dB over the X-band. The measured bandwidth of the miniaturized divider is less than 1.6 GHz. Comparison between the Wilkinson power divider and the miniaturized one shows that the shorter the quarter-wave transmission line is, the larger the impedance is. Meanwhile, the chip area reduction also leads to narrowed bandwidth of the power divider. The experiments demonstrate that the MMIC chip area of the power divider has been reduced by nearly 50% by capacitive loading, whereas the bandwidth is also narrowed by 50%. Therefore, the Wilkinson power divider applies to the situation if wide bandwidth is needed, while the miniaturized one is a better solution for small chip area. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:700-705, 2014 [ABSTRACT FROM AUTHOR]

A high dynamic range microwave power sensor compatible with the gallium arsenide monolithic microwave integrated circuit process is presented. The power sensor consists of a thermoelectric power sensor and a capacitive power sensor for low and high power detection, respectively. To improve the dynamic range and optimise the impedance matching characteristic, the curled cantilever beam is utilised and the slot width of the coplanar waveguide transmission line is modified. The measured return loss is lower than –25.5 dB at 8–12 GHz. The output of the power sensor shows good linearity with the incident radio frequency power. For the incident power from 0.1 to 100 mW, the obtained sensitivities by a thermoelectric power sensor are about 0.0842, 0.0752 and 0.0701 mV/mW at 8, 10 and 12 GHz, respectively. For the incident power from 100 to 400 mW, the measured sensitivities by the capacitive power senor are about 0.0400, 0.0301 and 0.199 fF/mW at 8, 10 and 12 GHz, respectively. [ABSTRACT FROM AUTHOR]