Abstract
This paper presents a low-power fully integrated quadrature signal generator for system-on-chip (SoC) impedance spectroscopy applications. It has been designed in a 0.18 μm-1.8 V CMOS technology as a self-contained oscillator, without the need for an external reference clock. The frequency can be digitally tuned from 10 to 345 kHz with 12-bit accuracy and a relative mean error below 1.7%, thus supporting a wide range of impedance sensing applications. The proposal is experimentally validated in two impedance spectrometry examples, achieving good magnitude and phase recovery results compared to the results obtained using a commercial LCR-meter. Besides the wide frequency tuning range, the proposed programmable oscillator features a total power consumption lower than 0.77 mW and an active area of 0.129 mm2, thus constituting a highly suitable choice as stimulation module for instrument-on-a-chip devices.
Highlights
Recent advances in microsensing techniques are leading to a growing need for on-chip electronic instrumentation, providing the required performances and simultaneously complying with the constraints of low power and compact size, to fully satisfy the emerging market demands and potential applications of portable and wearable sensing devices
Synchronous demodulation [11,12] can be implemented in CMOS technology [13,14] using phase sensitive detection (PSD) or quadrature modulators, which extract the signal amplitude and phase information at a specific frequency f o while noise signals at other frequencies are rejected
This paper presents implementation experimental results versatile signal generation circuit suitable forforportable of a versatile signal generation circuit suitable portablePSD
Summary
Recent advances in microsensing techniques are leading to a growing need for on-chip electronic instrumentation, providing the required performances and simultaneously complying with the constraints of low power and compact size, to fully satisfy the emerging market demands and potential applications of portable and wearable sensing devices. New transduction techniques in micro-integrated sensors include resonant detection and complex impedance characterization, as in surface acoustic wave sensors [1], gas sensors [2,3,4,5], laser interferometry [6], brain monitoring [7], non-invasive light detection [8] or biological impedance measurement [9,10] For these transducers, a suitable interrogation approach, which presents advantages compared to other electronic readout techniques due to its characteristics, is synchronous demodulation. Digitally soso that cancan be adjusted according to the application This oscillator generates a quadrature signal pair (VS , VC ) with a phase shift of 90° [15].
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