Digital Phase-Locked Loop for Intracranial Pressure Measurement
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Solution Overview
Problem
Existing methods for non-invasive measurement of intracranial pressure suffer from accuracy, precision, noise, and stability issues due to interference from measurement path elements and reflections, and are unable to provide linear phase difference measurements, leading to errors and uncertainties.
Innovation Solution
A system utilizing a constant frequency pulsed phase-locked loop (CFPPLL) with a digital oscillator module, linear phase detector, and tone-burst module, which generates and adjusts reference and measurement waveforms to determine phase differences accurately, allowing for continuous phase adjustment and precise measurement of intracranial dynamics and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quadrature phase detector is used to detect phase changes, then phase changes can be detected, but measurement accuracy deteriorates due to interference from measurement path elements and reflections
Solution Approach 1:
The patent extracts and removes the harmful elements (coaxial cables, amplifiers, signal splitters, ultrasonic transducers, and skull reflections) from the measurement path by using a digital signal processing approach that virtually eliminates these physical components, thereby eliminating their interfering effects on phase measurement accuracy
Solution Approach 2:
The patent replaces the physical quadrature phase detector with a digital phase detector that performs phase detection through digital signal processing, substituting the mechanical/electrical detection system with a computational approach that is not susceptible to the same interference problems
2Measurement precision
If quadrature phase detector is used, then phase changes can be detected, but measurement linearity deteriorates preventing numerical phase output
Solution Approach 1:
The patent replaces the non-linear quadrature phase detector with a digital phase detector that provides linear phase measurement output, enabling direct numerical representation of phase differences without the sinusoidal non-linearity inherent in quadrature detection methods
Solution Approach 2:
The patent changes the detection parameter from quadrature voltage output to direct phase difference measurement, transforming the measurement parameter to achieve linearity and enable numerical phase output
3Stability of the object's composition
If PPLL frequency adjustment is used to reestablish quadrature, then phase synchronization can be achieved, but measurement stability deteriorates due to frequency and phase uncertainties
Solution Approach 1:
The patent replaces the frequency-adjustment-based PPLL system with a digital phase-locked loop that maintains constant frequency while achieving phase lock through digital processing, eliminating the frequency drift and instability associated with analog frequency adjustment methods
Solution Approach 2:
The patent implements a digital feedback mechanism that continuously monitors phase difference and adjusts the digital oscillator accordingly, providing more stable and precise phase synchronization compared to the analog frequency adjustment feedback in traditional PPLL systems
4Reliability
If constant frequency operation is used, then measurement stability improves, but phase adjustment flexibility deteriorates
Solution Approach 1:
The patent replaces physical phase adjustment mechanisms with digital phase adjustment capability, allowing flexible phase modification through software control while maintaining constant operating frequency, thereby achieving both stability and adaptability
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 provides more accurate, robust, and stable measurements of intracranial pressure and skull expansion, enabling precise tracking of phase changes and improved bandwidth, allowing for reliable assessment of intracranial dynamics and physiological phenomena.
Implementation Method 1
a transducer (e.g. an ultrasonic transducer, such as a piezoelectric transducer) communicatively coupled to the tone-burst module
Implementation Method 2
such as a piezoelectric transducer
Implementation Method 3
a linear phase detector
Data Source
AI summary
Systems and methods for measuring phase dynamics and other properties (e.g. intracranial pressure) are disclosed. For example, the system may generate a reference waveform and a measurement waveform using digital synthesizers, each waveform having an identical constant frequency but also a relative phase shift. Next, system may send a tone-burst, via a transducer, into a sample (e.g. a skull or a bonded material), and then receive a reflected tone-burst in response. Then, a phase difference between the received tone-burst and the measurement waveform may be determined with a linear phase detector. Next, the phase shift of the measurement waveform may be adjusted, by the determined phase difference, such that there is no longer any phase difference between the received tone-burst and the adjusted measurement waveform generated by the appropriate digital synthesizer. A similar adjustment may occur after subsequent tone-bursts, allowing accurate monitoring of continuously variable phase relationships.