Browsing by Author "Elsayed, 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
Experimental investigations on the synthesis of W-Cu nanocomposite through spark plasma sintering
(ELSEVIER, 2015) Elsayed, Ayman; Li, Wei; El Kady, Omayma A.; Daoush, Walid M.; Olevsky, Eugene A.; German, Randall M.
Elemental powders of nanosized tungsten and chemically deposited nanosized copper were used for preparing tungsten/copper composites, which are used as electric contact components. A composite of 70 wt.%W/30 wt%Cu (52 vol%W/48 vol% Cu) composition was prepared by three powder metallurgy techniques. Elemental mixing, mechanical milling and electroless Cu coating on tungsten particles were used for the synthesis. The obtained powder blends underwent consolidation by rapid hot pressing using the spark plasma sintering (SPS) route at 950 degrees C under vacuum and by conventional vacuum pressureless sintering for comparison. The elemental powders and the sintered composites were investigated by optical microscopy and SEM. Electrical conductivity, hardness, transverse rupture strength, and wear properties were measured. Results show that the synthesis of the composite by the investigated route yields good performance. Samples prepared by SPS have shown better mechanical properties than those prepared by compaction and sintering due to their fine microstructure. (C) 2015 Elsevier B. V. All rights reserved.
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.
Measurement of continuous-time ΣΔ modulators: Implications of using spectrum analyzer
(IEEE, 2010) Ashry, Ahmed; K El-Shennawy, Ahmed; Elbadry, Mohammad; Elsayed, Ayman; Aboushady, Hassan
In this paper, The difference between getting the output spectrum directly using spectrum analyzer and obtaining the spectrum digitally in measuring clock jitter effect on continuous-time ΣΔ modulator is analyzed. It is shown that clock jitter can be seen as input-referred or output-referred, depending on the nature of the measurement tool. Quantization noise and jitter noise are analyzed and compared graphically using a simple approach. The presented analysis is verified with system-level simulation of a 4 th order bandpass continuous-time ΣΔ modulator.
∑-Δ based force-feedback capacitive micro-machined sensors: Extending the input signal range
(IEEE, 2017) H Ismail, Ayman; Elsayed, Ayman
Operating MEMS capacitive sensors in negative feedback mode results in improved bandwidth, and lower sensitivity to process and temperature variation. Feedback operation is achieved by applying a feedback voltage to the actuation electrodes of the sensor, generating a corresponding feedback-force on the sensor proof mass. To overcome, the non-linearity of the quadratic voltage-to-force relation in capacitive feedback, a two-level voltage feedback signal is often used. Therefore, a singlebit Σ-Δ modulator represents a practical way to implement force-feedback sensors interface systems. However, single-bit Σ-Δ modulators have a limited input-range that is less than the available full-scale dictated by the actuation voltage value. This is caused by quantizer overload, and the consequent reduction in quantizer effective gain as the input signal approaches full-scale. In this work, a solution is proposed that allows extending the input signal range of Σ-Δ based capacitive sensors beyond the limit imposed by single-bit operation. The proposed technique is applied to the design of a MEMS based accelerometer, and results in an increase in the input signal range from 35g to 40g, and an improvement in signal-to-noise ratio from 130.2dB to 137.3dB, at the same actuation voltage level.