Q-PLL Pitch Perception Circuit for Stable Complex Sound Locking
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Solution Overview
Problem
Existing technologies face challenges in accurately modeling and emulating the pitch perception of complex sounds, particularly in auditory devices, leading to instability and inefficiency in signal processing, which affects robotics applications and aids for hearing-impaired individuals.
Innovation Solution
A Quasi-Periodic Locked Loop (Q-PLL) circuit based on non-linear dynamical systems, utilizing three-frequency resonances to stabilize frequency locking for quasi-periodic input signals, even under noise or deterministic perturbations, by implementing a feedback system that selects and locks to main resonances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PLL circuits are used for pitch tracking, then the circuit can operate with simple structure, but it fails to achieve stable frequency locking for quasi-periodic input signals with noise or deterministic perturbations
Solution Approach 1:
The patent segments the frequency locking problem by introducing multiple resonators with different natural frequencies instead of using a single PLL circuit. Each resonator targets specific frequency components, and their combined output achieves stable pitch tracking for quasi-periodic signals. This segmentation allows the system to handle complex input signals by dividing the frequency spectrum into manageable segments.
Solution Approach 2:
The patent applies local quality by giving each resonator specific tuning characteristics tailored to its target frequency range. The resonators are designed with different quality factors and frequency responses optimized for their respective segments of the input signal spectrum. This localized optimization enables each component to contribute effectively to the overall stable pitch tracking performance.
2Adaptability or versatility
If the circuit uses wide range of control parameters to improve adaptability, then it can handle diverse input frequencies, but it becomes more sensitive to noise and non-harmonic frequencies
Solution Approach 1:
The patent converts the harmful effect of noise and non-harmonic frequencies into beneficial information by using resonators that are specifically tuned to resonate with the fundamental pitch frequency. The resonators filter out noise and non-harmonic components while amplifying the desired pitch signal through resonant enhancement. This approach transforms the challenging wide frequency range into an advantage by using the resonant properties to selectively enhance the fundamental frequency while suppressing unwanted components.
3Measurement precision
If the circuit implements exact pitch detection for complex sounds, then it achieves high measurement precision, but it requires complex signal processing that reduces efficiency
Solution Approach 1:
The patent implements self-service by using the input signal itself to drive the resonators at their natural frequencies. The resonators automatically tune to the fundamental pitch frequency through self-sustained oscillations, eliminating the need for complex external control circuits or iterative algorithms. This self-organizing behavior achieves exact pitch detection while maintaining high processing efficiency, as the system naturally converges to the correct frequency without requiring intensive computational resources.
Data Source
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AI summary
Circuit for modeling and emulating the pitch perception of complex sounds comprising: • a sample and hold circuit (2) arranged to receive and sample a quasi-periodic input signal (IN) comprising at least two predetermined frequencies (fI, f2), thus obtaining a sampled signal; • a multiplier (8), connected to the sample and hold circuit (2), arranged to multiply the input signal (IN) with the sampled signal, thus obtaining a multiplied signal; • a low-pass filter (10), connected to the multiplier (8), arranged to filter the multiplied signal, thus obtaining a filtered signal; • a voltage control oscillator (4), connected to the low-pass filter (10), arranged to provide an output signal which represents a response frequency of the circuit, said output signal emulating the pitch of the quasi-periodic input signal (IN); • a discretization block (6), connected to the voltage control oscillator (4), arranged to discretize the output signal, thus obtaining a discretized signal, said discretized signal being arranged to enter the sample and hold circuit (2) in order to provide the sampling frequency of the sample and hold circuit (2); wherein the filtered signal makes the voltage control oscillator frequency to lock to a main resonance of the circuit fR = (fI+f2)/(p +q), where fI and f2 are the two predetermined frequencies, and p / q is one of the possible convergent of fI/f2.