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This letter presents an 11 b 200 MS/s 28 nm CMOS 2b/cycle successive‐approximation register (SAR) analogue‐to‐digital converter (ADC). The offset calibration technique is proposed to reduce the comparator offset mismatch that degrades the linearity of the high‐resolution 2b/cycle SAR ADC. The offset mismatch is reduced to within 0.25 least significant bit (LSB) by generating a compensation voltage from capacitor‐resistor (C‐R) hybrid digital‐to‐analogue converters (DACs). The prototype ADC implemented in a 28‐nm CMOS process demonstrates measured differential and integral non‐linearities within 0.6 LSB and 1.73 LSB at 11 b resolution, respectively. The measured signal‐to‐noise‐and‐distortion ratio (SNDR) and spurious‐free dynamic range (SFDR) are 50.9 dB and 66.2 dB at Nyquist, respectively. The prototype ADC occupies an active die area of 0.115 mm2 and consumes 3.98 mW at a 1.1‐V supply voltage. This letter presents an 11 b 200 MS/s 28‐nm CMOS 2b/cycle successive‐approximation register (SAR) analogue‐to‐digital converter (ADC). The proposed calibration technique reduces the comparator offset mismatch to within 0.25 LSB at 11 b resolution, enabling the implementation of high‐resolution 2b/cycle SAR ADC.

In wireless sensor networks, clustering is effectively used for many applications, including environment monitoring, because it promises efficient energy consumption for inexpensive battery-operated sensors. The most famous clustering protocol, LEACH (Low Energy Adaptive Clustering Hierarchy), enables the balanced consumption of energy to prolong a network lifetime. In LEACH, however, extra energy and time are consumed to reform clusters at the setup phase of every round. This side effect is worse as the number of clusters increases. This paper presents a novel energy-efficient clustering scheme called COTS (Clustering with One-Time Setup) which removes the cluster-reforming process required at every round after the first round. The proposed COTS allows that the role of the cluster head is rotated among members in a cluster without cluster reforming. By removing the cluster-reforming process, the number of transmissions per round is decreased accordingly. As a result, energy consumption is significantly reduced, resulting in prolonged network lifetime. The simulation study shows that the network performance and lifetime are much improved as the number of clusters is increased.