This paper presents a passive wireless long-range displacement sensor that is based on the circular patch antenna, and the detecting range of the sensor can be customized. The sensor consists of a chipped circular antenna with two opened rectangular windows, a substrate, and a ground plate with a sloping channel. No bonding between the antenna and the ground plate allows for the chipped antenna to slide along the sloping channel. The channel will drive the current flow on the plate once the chip is activated, increasing the effective electrical length and, consequently, decreasing the resonant frequency of the circular antenna. The sensing mechanism equates the measuring displacement to the relative movement of the antenna with respect to the ground that achieves the measurement of long-range displacement and, thus, the proposed sensor can avoid stress damage to the antenna due to excessive deformation. Three different range sensors were simulated in the the Ansoft high frequency structure simulator (HFSS). The results show that the resonance frequency of the antenna has a linear relationship with the varying chute depth beneath the chip. Three sensors were fabricated, and the experimental results also validated that the sensitivity of the sensor can be adjusted.
This paper presents a capacitive displacement sensor based on a capacitively fed inverted-F antenna (CFIFA) for displacement detection. The sensor is composed of a grounded L-shape patch and a rectangular upper patch, forming a capacitor between them. The asymmetric dipole model is adopted to explain the frequency shift and current distribution of the proposed antenna sensor at its first-order resonance. The numerical simulation of the CFIFA using the Ansoft high-frequency structure simulator (HFSS) software is carried out to optimize the dimensional parameters, allowing the antenna to perform better. Two sets of CFIFAs are fabricated and tested for verification. Results show that the CFIFA has a good linear relationship between its first resonant frequency and the relative displacement, and is capable of a long range of displacement measuring.
Abstract-An open-loop switch-capacitor detection circuit with high resolution and low noise is proposed for a butterfly accelerometer. This paper introduced the composition and realization principle of the system, proposed a C/V detection structure and a filter with high Q value. The preamplifier adopted the folded cascode structure with the gain enhancement technology to achieve high GBW and improved the phase margin. The input common mode feedback helps to achieve a high linearity detection and have an ideal dynamic detection range. All of the voltage and current are supplied by the reference source with low temperature coefficient. Under the Cadence Design System, the spectre circuit simulation is performed based on the 0.6um CMOS standard process model. The results show the detection range of the Accelerometer is±0.1pF, sensitivity is 25V/pF, output noise is within 0.4uV/Hz1/2.
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