Abstract
With the growing need to understand our surroundings and improved means of sensor manufacturing, the concept of Internet of Things (IoT) is becoming more interesting. To enable continuous monitoring and event detection by IoT, the development of low power sensors and interfaces is required. In this work we present a novel, switched inductor based acoustic sensor interface featuring a bandpass filter and envelope detector, perform a sensitivity, frequency selectivity, and power consumption analysis of the circuit, and present its design parameters and their qualitative influence on circuit characteristics. We develop a prototype and present experimental characterization of the interface and its operation with input signals up to 20 mV peak-to-peak, at low acoustic frequencies from 100 Hz to 1 kHz. The prototype achieves a sensitivity of approximately 2 mV/mV in the passband, a four times lower sensitivity in the stopband, and a power consumption of approximately 3.31 µW. We compare the prototype interface to an interface consisting of an active bandpass filter and a passive voltage doubler using a prerecorded speedboat signal.
Highlights
The growing need to understand and manage our surroundings, coupled with advances in sensor technologies and manufacturing processes [1], has led to an increased interest in the concept of Internet of Things (IoT), which envisions sensor networks consisting of hundreds of thousands of small, robust sensor nodes utilized to continuously monitor real-world events and processes [2,3,4]
In [17] we studied the impact of the envelope detector on sensitivity and power consumption of the wake-up sensor interface in the lower audio frequency range
In order to increase the sensitivity of low-power acoustic wake-up sensor interfaces, and at the same time lower their power consumption, in this work we propose a novel approach, utilizing an electrically switched inductor as a replacement for conventionally used bandpass filter and envelope detector functional blocks
Summary
The growing need to understand and manage our surroundings, coupled with advances in sensor technologies and manufacturing processes [1], has led to an increased interest in the concept of Internet of Things (IoT), which envisions sensor networks consisting of hundreds of thousands of small, robust sensor nodes utilized to continuously monitor real-world events and processes [2,3,4]. Acoustic sensors present an attractive choice for IoT applications because they generate signals that are rich in information and can be processed using relatively simple hardware [6,7,8] that powers up the rest of the sensor node only upon detection of an event of interest [4,5], thereby reducing the power consumption of an acoustic sensor node. These wake-up sensor interfaces utilize bandpass filtering, envelope detection, quantization, and some rudimentary form of classification to determine if an event of interest occurred. The power consumption of the bandpass filter and the envelope detector is reported as 8.25 μW in [9] and 20.74 μW in [10]
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