dc.description.abstract | Abstract
Recently, the rapid expansion of the biomedical-electronic market has necessitated low-power and low-voltage biomedical systems [1], [2]. Since battery power is used for most of the portable biomedical devices. Expanding battery lifetime through the topology of low power dissipation systems is very crucial. In the digital hearing-aid applications, the battery is typically made of zinc–air and should offer a life span of at least two weeks at 10 hours use per day [3]. Moreover, the digital hearing aid requires wide dynamic range, high performance, more programmability, and small form factor. Hence, it is necessary to achieve low power dissipation, high performance, and programmability to expand battery lifetime and to offer convenient hearing to the users.
Due to low-amplitude and non-stationary properties of biomedical signals, high resolution and low-power consumption are necessary for the analog-to-digital (A/D) convector (ADC). Sigma-Delta Modulator has good performance in the resolution and power consumption. In this thesis, Sigma-Delta Modulator (SDM) for a biomedical electronic system is proposed. Basically, the switched-capacitor (SC) technique and the Feedforward(FF) technique can be used to implement SDM. The proposed SDM was simulated with TSMC 0.18 ?m 1P6M CMOS technologies. The signal bandwidth is 10 KHz and its clock rate is 2.56 MHz i.e. the over-sampling ratio (OSR) is equal to 128. Hence, it can achieve 75.75 dB signal-to-noise and distortion ratio (SNDR), and higher than 10 bits resolution in 2nd orders SDM. Moreover, the power consumption is about 358 ?W in 12 bits resolution under normal operation and the dynamic range is 85 dB with a single 1.8V power supply.
Basically, an SDM ADC consists of an Analog SDM and Digital Decimation filter. Therefore, we can take the advantage of low power consumption of the implanted SDM to integrate two SDM adaptively with one digital decimation filter. Then we can easily to monitor 1 or 2 biomedical signals at the sample time and save the total chip area.
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