Electronic oscillator | EPFL Graph Search

An electronic oscillator is an electronic circuit that produces a periodic, oscillating or alternating current (AC) signal, usually a sine wave, square wave or a triangle wave, powered by a direct current (DC) source. Oscillators are found in many electronic devices, such as radio receivers, television sets, radio and television broadcast transmitters, computers, computer peripherals, cellphones, radar, and many other devices. Oscillators are often characterized by the frequency of their output signal: *A low-frequency oscillator (LFO) is an oscillator that generates a frequency below approximately 20 Hz. This term is typically used in the field of audio synthesizers, to distinguish it from an audio frequency oscillator. *An audio oscillator produces frequencies in the audio range, 20 Hz to 20 kHz. *A radio frequency (RF) oscillator produces signals above the audio range, more generally in the range of 100 kHz t

Networks of Coupled VO2 Oscillators for Neuromorphic Computing

Elisabetta Corti

Neuromorphic computing is a wide research field aimed to the realization of brain-inspired hardware, apt to tackle computation of unstructured data more efficiently than currently done with standard computational units. Oscillatory neural networks are known for their associative memory capability, which enables to retrieve the information stored in the system from noisy or incomplete data. The development of phase-transition materials such as vanadiumdioxide (VO2) allows to design compact relaxation oscillator units which can be coupled in frequency and phase to realize an oscillatory neural network in hardware. In this thesis, we investigate the oscillatory neural network technology from the realization of the basic oscillator components with VO2 to the exploitation of the coupled oscillators as analog filters in convolutional neural networks applications. VO2 phase-transition devices are realized in a CMOS compatible process in two geometries, a planar and a crossbar configuration. The impact of the polycrystallinity of the VO2 film on the insulator-to-metal transition of the device is analyzed; through the contacting of a single grain we demonstrate the realization of a VO2 device with a single, sharp phase transition. The VO2 devices are connected in circuits to build networks of coupled oscillators. Through coupling with resistive and capacitive elements, experimental demonstrations of a 4-VO2 coupled oscillator network is shown. The network encodes the input and output information in the relative phase of the oscillators. The associative memory capability of the system is used to extract features from hand-written digits. By expanding the network to a 3×3 coupled oscillator system, we demonstrate in simulations how an oscillatory neural network can replace up to five digital filters in a convolutional neural network, retaining the same image processing capabilities.

EPFL2021

A Cryo-CMOS Oscillator With an Automatic Common-Mode Resonance Calibration for Quantum Computing Applications

Edoardo Charbon, Yue Chen, Fabio Sebastiano

This article presents a 4-to-5 GHz LC oscillator operating at 4.2K for quantum computing applications. The phase noise (PN) specification of the oscillator is derived based on the control fidelity for a single-qubit operation. To reveal the substantial gap between the theoretical predictions and measurement results at cryogenic temperatures, a new PN expression for an oscillator is derived by considering the shot-noise effect. To reach the optimum performance of an LC oscillator, a common-mode (CM) resonance technique is implemented. Additionally, this work presents a digital calibration loop to adjust the CM frequency automatically at 4.2K, reducing the oscillator's PN and thus improving the control fidelity. The calibration technique reduces the flicker corner of the oscillator over a wide temperature range (10 x and 8 x reduction at 300K and 4.2K, respectively). At 4.2K, our 0.15-mm(2) oscillator consumes a 5-mW power and achieves a PN of -153.8dBc/Hz at a 10MHz offset, corresponding to a 200-dB FOM. The calibration circuits consume only a 0.4-mW power and 0.01-mm(2) area.

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

Cryogenic single chip electron spin resonance detectors

Gabriele Gualco

Methods based on the electron spin resonance (ESR) phenomenon are used to study paramagnetic systems at temperatures that ranges from 1000 to below 1 K. Commercially available spectrometers achieve spin sensitivities in the order of 10^(10) spins/¿Hz at room temperature on sample with volumes in the order of few µl. This results can be improved by cooling the system at cryogenic temperatures, where the larger magnetization of paramagnetic samples cause the detected signal to increase. Furthermore operation at high field (frequency) turns as well in an improved spin sensitivity. For what it concern the spin sensitivity operation at cryogenic temperature and high frequency are thus beneficial. In 2008 the group of Dr. G. Boero proposed a novel detection method based on the integration of all the element responsible for the sensitivity on a single silicon chip. The methodology allowed to study sample with nanoliter scale volume with spin sensitivity that were at least 2 orders of magnitude better than the best commercial spectrometer. The proposed method has performance that are comparable with the one obtained on similar scales with micro-resonator based spectroscopy tool. During this thesis I have investigated the possibility of extending the use of the detection method from frequency that goes from 20 to 200 GHz and temperatures that range from 77 to 4 K. In this frame several domains were touched. First of all the design of CMOS silicon oscillators operating at frequency which are closed to the most modern technology frequency limit. The lack of model valid for the target frequencies and the needs of limiting the power consumption for matching the limited cooling power of cryogenic systems, made the subject a challenging and interesting research topic itself. The study produces a remarkable result of a system operating at about 170 GHz with a power consumption of about 3 mW at room temperature and about 1.5 mW at 4 K. With the realized devices the first measurements of integrated silicon CMOS LC oscillators at temperature below 77 K were performed. From this measurements we could confirm the presence of expected effect, such as minimum power consumption reduction and oscillator frequency increase. In addition to that, by measuring the frequency-bias characteristic, it's been noticed a succession of smooth region and sharp transitions. This jumps are tentatively attributed to the random telegraph signal (RTS) effect that is supposed to be the main responsible for the flicker noise in sub-micrometer MOS devices. Since the impact of RTS on the performance of highly scaled transistor performance is expected to grow with the technology scale down, measurement methods based on LC oscillator, that shows better sensitivity if compared with nowadays employed methods, might allow to better understand the mechanism governing the effect and to develop technological strategy for lowering the impact on the future CMOS technology node. The realized devices have finally demonstrated ESR performances that are comparable with the most recent publication done with miniaturized resonators on mass-limited samples. In fact sensitivity of about 10^(7) spins/¿Hz at 50 GHz and 300 K and of about 10^(6) spins/¿Hz at 28 GHz and 4 K, at least 3 orders of magnitude better then commercially available state of the art devices, have been proven.

EPFL2015

Cryogenic single chip electron spin resonance detectors

Gabriele Gualco

EPFL2015