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CMOS Systems and Interfaces for Microgyroscopes
Published in Krzysztof Iniewski, Circuits at the Nanoscale, 2018
Ajit Sharma, Mohammad F. Zaman, Farrokh Ayazi
The drive loop electronics are responsible for starting and sustaining vibrations along the reference axis at constant amplitude. It is essential that constant drive amplitude is maintained, as any variations in the drive amplitude manifests as a change in velocity of the mechanical structure, resulting in false rate output. The drive loop uses an automatic level control (ALC) circuit to achieve and maintain constant drive amplitude. There are two approaches to implement the drive loop: An electromechanical oscillator: Here the drive mode oscillations are started and sustained by using a positive feedback loop that satisfies the Barkhausen’s criteria (loop gain = 1, loop phase shift = 0°). The gyroscope forms the frequency-determining element of the electromechanical oscillator. A high mechanical quality factor for the drive resonant mode (QDRV) can significantly ease the design of the drive oscillator, enabling the drive oscillations to be built up, and sustained, using much smaller AC voltage levels.A phase-locked loop (PLL) oscillator: Here the PLL center frequency and capture range are set close to the drive resonant frequency of the gyroscope. On power up, the PLL locks on to the output of the front-end I–V converter. The PLL output is amplified or attenuated to achieve the desired voltage amplitude and is used to drive the microgyroscope. The PLL-oscillator relies on the precise 90° phase shift occurring at drive resonance. A variable gain amplifier is used to implement ALC.
CMOS Systems and Interfaces for Sub-Deg/Hr Microgyroscopes
Published in Vikas Choudhary, Krzysztof Iniewski, MEMS, 2017
Ajit Sharma, Mohammad Faisal Zaman, Farrokh Ayazi
The drive loop electronics is responsible for starting and sustaining vibrations along the reference axis, at constant amplitude. It is essential that constant drive amplitude is maintained, as any variations in the drive amplitude manifests a change in velocity of the mechanical structure, resulting in false rate output. The drive loop uses an automatic level control (ALC) circuit to achieve and maintain constant drive amplitude. There are two approaches to implement the drive loop: An electromechanical oscillator: Here the drive mode oscillations are started and sustained by using a positive feedback loop that satisfies the Barkhausen criteria (loop gain = 1, loop phase shift = 0°). The gyroscope forms the frequency-determining element of the electromechanical oscillator. A high mechanical quality factor for the drive resonant mode (QDRV) can significantly ease the design of the drive oscillator, enabling the drive oscillations to be built up, and sustained, using much smaller AC voltage levels.A phase-locked-loop (PLL) oscillator: Here the PLL center frequency and capture range are set close to the drive resonant frequency of the gyroscope. On power up, the PLL locks on to the output of the front-end I–V converter. The PLL output is amplified or attenuated to achieve the desired voltage amplitude and is used to drive the microgyroscope. The PLL oscillator relies on the precise 90° phase shift occurring at drive resonance. A variable gain amplifier is used to implement ALC.
Portable High-Frequency Ultrasound Imaging System Design and Hardware Considerations
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Insoo Kim, Hyunsoo Kim, Flavio Griggio, Richard L. Tutwiler, Thomas N. Jackson, Susan Trolier-McKinstry, Kyusun Choi
The TGC provides time-varying gain for the reflected ultrasound signal whose attenuation varies as a function of depth and the attenuation coefficient of the medium. From Equation 16.1, ultrasound waves attenuate on a logarithmic scale rather than a linear scale. This means that the TGC should express a variable linear gain range in the decibel scale. The TGC can be a variable gain amplifier (VGA).
Efficient recursive least squares parameter estimation algorithm for accurate nanoCMOS variable gain amplifier performances
Published in International Journal of Electronics, 2020
Houda Daoud, Sawssen Lahiani, Samir Ben Salem, Mourad Loulou
The variable gain amplifier (VGA) is an indispensable building block in modern wireless transceiver designs since it ensures the receiver gain regulation. In fact, the VGA controls the signal power level and maximises the dynamic range of the communication links, where the variation in the received signal strength is significant owing to the channel fading. In a wireless communication receiver, the VGA is typically used in a feedback loop to achieve an automatic gain control (AGC). Thanks to the VGA topology, a constant signal power is provided to a baseband analog-to-digital converter for unpredictable received signal strengths (Dogus Gungordu & Tarim, 2018). In this section, we focused on predicting the VGA performances during the process scaling using the proposed RLS algorithm.