A structure for single-stage high-order bandpass sigma-delta modulators (BPSDMs) is presented. The proposed structure introduces an additional internal path in each resonator, thus, adding one degree of freedom in coefficient determination. Coefficient spread can therefore be reduced, resulting in significantly reduced capacitance area in switched-capacitor BPSDM circuits. High-order BPSDMs with different quality factors (Q) are demonstrated. It shows that coefficient spread is significantly reduced, especially for high-Q applications. For comparable eighth-order 3-bit BPSDMs, the maximum coefficient spread are respectively 15369 and 7693 for conventional cascade-of-resonator-with-feedback (CRFB) and cascade-of-resonator-with-feedforward (CRFF) designs, and 114 for the proposed structure. For an eighth-order 1-bit example, these respective values are 8994, 2638, and 74. With coefficient mismatch, peak signal-to-noise ratio (PSNR) degradation of the proposed structure is less than those of the CRFB and CRFF structures, demonstrating reduced sensitivity to component mismatch. Hence, the proposed structure can reduce chip area and ease circuit implementation of BPSDMs.
A flexible Ti/Cr/Ti multilayer strain gauge have been successfully developed based on polyimide substrate. The pure Ti metal strain gauge have shown the hysteresis phenomenon at the relationship between resistance and strain during tensile test. The experimental results of multilayer strain gauge show that adding Cr interlayer can improve the recovery and stability of the sensing electrode. When the interlayer Cr thickness was increased from 0 to 70 nm, the resistance decreased from 27 to 8.8 kΩ. The gauge factor (GF) value also decreased from 4.24 to 2.31 with the increase in the thickness of Cr interlayer from 30 to 70 nm, and the hysteresis phenomenon disappeared gradually. The multilayer Ti/Cr/Ti film has feasible application for strain sensor.
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