A Readout circuit for resonant MEMS temperature sensors

Asadi, Hamed
High precision is the dominant advantage that resonant sensors have over other types of analog sensors (sensors with a subsequent analog-to-digital converter). The resolution of these precise sensors is determined by both frequency resolution and sensitivity of the sensor. The sensitivity is highly related to the sensitivity of the MEMS resonator. However, the frequency resolution is dominantly defined by the closed-loop circuitry if noise contribution of the resonator is assumed to be smaller than that of the electronic circuitry. In this thesis, resolution reduction of a closed-loop resonant sensor is intended to be accomplished. The DETF (double-ended tuning-fork) MEMS resonator used in this study is already designed and fabricated in METU MEMS. The TCF (temperature coefficient of frequency) of this resonator is 53 ppm/K which results in a sensitivity of 9.27 Hz/K with 174.818 kHz resonant frequency. This implies that the sensitivity is fixed and the only remaining parameter to achieve a better resolution for the sensor is the frequency resolution of the closed-loop circuitry. Since closed-loop with an AGC (automatic gain control) block has superior far-from-carrier phase noise performance in comparison to a closed-loop circuit with a limiter (e.g., comparator), this scheme is chosen to be implemented in XFAB 0.35um CMOS process. For the implemented closed-loop circuit in CMOS technology, the minimum achievable noise floor at the steady state oscillation is obtained to be -107 dBc/Hz. Based on the simulation results, when the "white phase" noise is filtered out, the sensor resolution is obtained to be around 0.021 degrees Celsius. To verify the functionality of the design in the CMOS technology, the closed-loop circuit is implemented again by discrete components. The stability and resolution evaluations of the implemented circuit are achieved by Allan deviation. The bias instability point is measured to be about 0.0045 degrees Celsius with 5.28 second averaging time. In this thesis, the main goal of the design, especially in XFAB 0.35um CMOS Process, is to study and characterize the noise and phase noise performances of the closed loop circuit. Thus, the resolution improvement can be accomplished by minimizing the noise in the loop. 


Resonance-based MEMS temperature sensors for temperature compensation of mems capacitive accelerometer
Demirhan, Gülşah; Akın, Tayfun; Department of Electrical and Electronics Engineering (2016)
The idea of the proposed study is using the resonator structure as a temperature sensor together with controller circuitry. That is to say, the study consists of two branches; one is PI controller output which would be used as a temperature sensor and the other is preamplifier output which would be used as carrier generator to the accelerometer readout circuitry. The proposed resonator is analyzed in detail in terms of dynamics, simulation models and theoretical investigations. The implemented resonator is ...
A Capacitive MEMS Accelerometer Readout with Concurrent Detection and Feedback Using Discrete Components
Terzioglu, Yunus; Alper, Said Emre; Azgın, Kıvanç; Akın, Tayfun (2014-05-08)
This paper presents an analog readout method for capacitive MEMS accelerometers in which the feedback actuation and capacitive detection are achieved simultaneously on the same electrode set. The presented circuit operates in closed-loop for improved linearity, and it is constructed in a hybrid platform package in which off-the-shelf discrete components are used together with the silicon-on-glass micro-accelerometer. The system is developed as a practical solution to reduce the complexity of the readout cir...
A New Baseband Equivalent Model for Sense Mode Dynamics and Its Effects on Force-Feedback Controller Design for MEMS Gyroscopes
Eminoglu, Burak; Alper, Said Emre; Akın, Tayfun (2011-10-31)
his paper introduces a new baseband equivalent model for the sense mode dynamics of a MEMS gyroscope providing a more accurate force-feedback controller design applicable to high-performance sensors with a small frequency separation between drive and sense modes. This new baseband equivalent model for sense dynamics correctly models the step response of the system allowing both “true prediction of the system bandwidth”, with an error less than 1%, and “proper control of the transient behavior” such as ringi...
Comparative design of millimeter wave RF-MEMS phase shifters
Kobal, Enis; Demir, Şimşek; Department of Electrical and Electronics Engineering (2016)
Phase shifters are widely used for electronic beam steering for various antenna applications. This thesis presents design and comparison of 3 di erent 3-bit transmission type phase shifters, which are switch-line, Distributed MEMS Transmission Line (DMTL) and triple stub phase shifters, realized with capacitive contact Radio Frequency (RF) Micro-Electro-Mechanical Systems (MEMS) switches for Ka-Band applications. For the design of switch-line phase shifter reducing the sensitivity of the electrical performa...
A High performance automatic mode-matched MEMS gyroscope
Sönmezoğlu, Soner; Demir, Şimşek; Department of Electrical and Electronics Engineering (2012)
This thesis, for the first time in the literature, presents an automatic mode-matching system that uses the phase relationships between the residual quadrature and drive signals in a gyroscope to achieve and maintain the frequency matching condition, and also the system allows controlling the system bandwidth by adjusting the closed loop parameters of the sense mode controller, independently from the mechanical sensor bandwidth. There are two mode-matching methods, using the proposed mode-matching system, p...
Citation Formats
H. Asadi, “A Readout circuit for resonant MEMS temperature sensors,” M.S. - Master of Science, Middle East Technical University, 2016.