Non-linear Chirp Signal Shaping for Ultrasonic Sensing
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Solution Overview
Problem
Existing ultrasonic sensor systems using chirp signals face inefficiencies due to significant spectral overlap and bandwidth requirements, leading to signal distortion and reduced amplitudes, particularly when center frequencies need to be separated to minimize overlap, resulting in operation below resonance frequencies and increased damping.
Innovation Solution
Implementing non-linear chirp signals with varying frequency change speeds, allowing for narrower spectra and reduced bandwidth requirements without worsening the signal/noise ratio, by adjusting the current pulse frequency over time according to specific equations and maintaining alignment with the resonance frequency for optimal transmission power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chirp-up and chirp-down signals are used with large bandwidth time products, then orthogonal signal shapes are achieved, but spectral overlap increases and bandwidth requirements become excessive
Solution Approach 1:
The patent applies parameter changes by modifying the chirp signal characteristics - specifically using different frequency sweep patterns (chirp-up vs chirp-down), adjusting the bandwidth time product, and optimizing the center frequency separation. These parameter adjustments enable achieving orthogonality with reduced spectral overlap and lower bandwidth requirements compared to conventional approaches.
Solution Approach 2:
The patent implements dynamics by using time-varying frequency modulation where the instantaneous frequency changes continuously during the pulse duration. The chirp signals dynamically sweep through different frequency ranges, with the frequency modulation index and sweep rate optimized to achieve orthogonal correlation properties while minimizing spectral occupancy.
2Reliability
If center frequencies are pulled apart to reduce spectral overlap, then signal distortion decreases, but operation occurs below resonance frequencies resulting in increased damping
Solution Approach 1:
The patent optimizes the center frequency separation parameter to find the optimal balance between reducing spectral overlap and maintaining operation near resonance frequencies. By carefully controlling the frequency offset and chirp parameters, the system achieves sufficient signal separation while keeping the center frequencies positioned to minimize damping and maximize transmission efficiency.
3Ease of manufacture
If linear chirp signals are used, then simple signal generation is achieved, but spectral width is excessive and side lobe interference increases
Solution Approach 1:
The patent applies curvature by using non-linear frequency modulation where the instantaneous frequency follows a curved trajectory rather than a straight line. Specifically, the frequency modulation incorporates quadratic or higher-order terms, creating a curved frequency-time relationship that compresses the spectral width and reduces side lobe levels while maintaining signal generation feasibility.
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
This approach reduces spectral overlap, minimizes bandwidth needs, and enhances signal amplitudes and noise ratio, maximizing the range of ultrasonic systems in applications like ultrasonic parking assistance systems, while maintaining high transmission power and reducing side lobe interference.
Implementation Method 1
a transducer (7) having a membrane (8) and being configured to transmit ultrasonic signals through the membrane (8) when a corresponding voltage is applied
Implementation Method 2
the membrane in the first ultrasonic sensor and the membrane in the second ultrasonic sensor have the same resonance frequency (f)
Data Source
AI summary
A method to operate an ultrasonic sensor includes the step of sending an ultrasonic burst as a series of ultrasonic pulses that have a pulse length and a pulse spacing. The sum of the pulse length and pulse spacing represents the pulse period length. The ultrasonic burst starts at a first time and ends at a second time. The current pulse frequency corresponds to an inverse of the current pulse length. The current pulse frequency, during a first time period passes through a first frequency range, in a following middle time period a middle frequency range and in a following second time period a second frequency range. The length of time of the middle time period is equal to or longer than the sum of the first time period and the second time period.