CMOS Piezoelectric Oscillator Calibration for Temperature-Stable Clocks
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Solution Overview
Problem
Existing piezoelectric transceiver systems face challenges in maintaining temperature independence and stability of oscillators, which is crucial for reliable time and frequency maintenance across varying temperatures, especially in CMOS integrated clock generators used in RF communications.
Innovation Solution
A CMOS device integrated with a temperature-insensitive, stable, and calibrated oscillator system that includes a voltage-controlled oscillator generating RF frequency pulses, piezoelectric transducers, and temperature-dependent programmed delays, utilizing resistors and CMOS circuits to minimize temperature dependence and achieve a fixed frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ultrasonic pulse transmit and receive architecture is used, then oscillator stability is improved, but temperature independence deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the received ultrasonic pulse triggers the next transmit pulse, forming a closed-loop oscillator system. This feedback approach stabilizes the oscillation frequency by using the actual pulse transit time as the timing reference, thereby improving oscillator stability while the temperature compensation techniques maintain temperature independence
Solution Approach 2:
The patent employs temperature compensation techniques that involve changing operational parameters to counteract temperature effects. By adjusting the trigger threshold and timing parameters based on temperature conditions, the system maintains temperature independence despite the inherent temperature sensitivity of ultrasonic propagation in silicon
2Reliability
If diffraction-based pulse distribution is utilized, then delay stability is improved, but temperature coefficient control becomes more difficult
Solution Approach 1:
The patent utilizes the diffraction pattern created by the finite aperture transducer, where different spatial regions (diffraction orders) produce pulses with different arrival times. By selectively using specific diffraction orders or regions, the system achieves stable delay while the temperature compensation addresses the temperature coefficient variations
Solution Approach 2:
The system dynamically adjusts the trigger threshold and selection of diffraction orders based on operating conditions to maintain optimal delay stability. The dynamic triggering mechanism adapts to temperature variations by adjusting when the received pulse triggers the next cycle, thereby managing the temperature coefficient control complexity
3Measurement precision
If fixed frequency oscillation is implemented, then RF communication accuracy is improved, but fabrication variation sensitivity increases
Solution Approach 1:
The oscillator system uses the actual ultrasonic pulse transit time through the silicon substrate as its own frequency reference. This self-service approach means the oscillator frequency is determined by the physical propagation time rather than external components, automatically compensating for fabrication variations in the silicon substrate while achieving accurate fixed frequency operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves a temperature coefficient of 0.667 ppm/K over a range of -20° to 125° C, ensuring stable clock generation and frequency accuracy, enabling effective temperature-independent operation for RF communications.
Implementation Method 1
Planar thin-film piezoelectric transducers are used to transmit and receive the pulses
Implementation Method 2
a piezoelectric receiver spaced from the piezoelectric transducer and configured to receive the plurality of short pulses
Implementation Method 3
The transmitted ultrasonic pulse undergoes diffraction, given that the aperture of the transducer is of finite width. Diffraction results in the distribution of the pulses in different angles from the transmitters
Implementation Method 4
an envelope detector or a RF mixer configured to convert the plurality of short pulses to an amplified signal
Data Source
AI summary
A temperature insensitive oscillator system. The system includes a substrate having a first surface and an opposing second surface, a CMOS device with one or more CMOS circuits attached to the first surface of the substrate, one or more piezoelectric transducers attached to an outer surface of the CMOS device, a voltage-controlled oscillator generating a RF frequency, which is transmitted as a plurality of short pulses to the one or more piezoelectric transducers, and one or more delays and oscillators using resistor and active components arranged alongside the piezoelectric transducers or on the CMOS device such that the voltage-controlled oscillator has minimal dependence on temperature, and has minimal deviation from a programmed frequency.