Browsing by Author "Ismail, Ayman"

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Electronic compensation of capacitive micro-machined sensors parasitic modes in force-feedback interface systems
(United States Patent US8872683B2, 2014) Ismail, Ayman; Elshennawy, Ahmed; Mokhtar, Ahmed; Elsayed, Ayman
Operating capacitive sensors in force feedback mode has many benefits, such as improved bandwidth, and lower sensitivity to process and temperature variation. To overcome, the non-linearity of the voltage-to-force relation in capacitive feedback, a two-level feedback signal is often used. Therefore, a single-bit Σ-Δ modulator represents a practical way to implement capacitive sensors interface circuits. However, high-Q parasitic modes that exist in high-Q sensors (operating in vacuum) cause a stability problem for the Σ-Δ loop, and hence, limit the applicability of Σ-Δ technique to such sensors. A solution is provided that allows stabilizing the Σ-Δ loop, in the presence of high-Q parasitic modes. The solution is applicable to low or high order Σ-Δ based interfaces for capacitive sensors
A High-Performance Self-clocked Digital-Output Quartz Gyroscope
(IEEE, 2015) Ismail, Ayman; Ashraf, Khaled; Metawe, Ahmed; Mostfa, Islam; Saeed, Ahmed; Helal, Eslam; Essawy, Mostafa; Abdelazim, Mohamed; Ibrahim, Mostafa; Raafat, Ramy; Abdelbary, Eslam; Alaa, Islam; Nabil, Marawan; Mansour, Abdelrahman; Ibrahim, Bassem; Elsayed, Ayman
High-performance electro-static gyroscopes require expensive vacuum-packaging, to maintain the high-Q of the MEMS, and may require high actuation voltages. Piezo sensors, on the other hand, do not suffer from these shortcomings. In this work, the architecture and the measurements results of a high-performance quartz gyro are presented. The architecture of the gyroscope interface ASIC adopts a mostly-digital implementation, where the drive-loop processing, demodulation, and post-filtering are implemented in the digital domain. Furthermore, the ASIC clock is based on self-clocking scheme, where the gyro drive frequency drives all internal clocks. The digital implementation, combined with self-clocking, allows the read-out ASIC to interface to different quartz-gyro sensing elements, with a wide range of drivefrequencies. The ASIC is tested with a tuning fork quartz gyro sensing element. The complete gyro sensor module achieves a ±500 deg/s input range, and a noise-floor of 2.5 mdeg/s/√Hz.
Interface for MEMS inertial sensors
(Shenzhen Goodix Technology Co Ltd, 2013) Elsayed, Ayman; Elmallah, Ahmed; Elshennawy, Ahmed; Shaban, Ahmed; George, Botros; Elmala, Mostafa; Ismail, Ayman; Sakr, Mostafa; Mokhtar, Ahmed
In a high-performance interface circuit for micro-electromechanical (MEMS) inertial sensors, an excitation signal (used to detect capacitance variation) is used to control the value of an actuation signal bit stream to allow the dynamic range of both actuation and detection paths to be maximized and to prevent folding of high frequency components of the actuation bit stream due to mixing with the excitation signal. In another aspect, the effects of coupling between actuation signals and detection signals may be overcome by performing a disable/reset of at least one of and preferably both of the detection circuitry and the MEMS detection electrodes during actuation signal transitions. In a still further aspect, to get a demodulated signal to have a low DC component, fine phase adjustment may be achieved by configuring filters within the sense and drive paths to have slightly different center frequencies and hence slightly different delays.