Time-Modulated Acoustic Beamforming for Interbeam Interference Control
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Solution Overview
Problem
Existing TMA systems do not adequately address design constraints such as interbeam interference, bearing-doppler ambiguity, spectra leakage interference, power amplifier source level, and cross-beam reverberation or clutter masking level in real-time operational conditions, particularly in noise-limited and clutter-limited environments.
Innovation Solution
A time-modulated array (TMA) system that generates a spatial distribution of acoustic transmitting frequencies for simultaneous multiple beam steering, incorporating a tapped delay line, mixers, bandpass filters, and transducer arrays, with design constraints to control bearing-target doppler ambiguity, uniform response, out-of-band spectra leakage interference, and cross-beam reverberation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple beams are steered simultaneously using TMA, then spatial coverage and detection capability are improved, but interbeam interference and cross-beam reverberation increase
Solution Approach 1:
The patent applies periodic time modulation to the array elements, where each element is modulated at a different duty cycle or pulse repetition frequency. This periodic action creates distinct frequency signatures for each beam, allowing simultaneous beamforming while separating them in the frequency domain, thereby reducing interbeam interference while maintaining spatial coverage
Solution Approach 2:
The patent changes the temporal parameters (duty cycle, pulse width, repetition frequency) of the modulation signals applied to different array elements. By varying these parameters, the system creates frequency-diverse beams that can be distinguished and processed separately, reducing mutual interference between simultaneously steered beams
2Measurement precision
If TMA systems operate in noise-limited environments, then detection sensitivity is improved, but bearing-doppler ambiguity increases
Solution Approach 1:
The patent introduces a temporal dimension through time modulation, adding a fourth dimension (time/frequency) to the traditional spatial beamforming. This allows the system to resolve bearing-Doppler ambiguities by exploiting frequency diversity created through time modulation, where ambiguous targets can be distinguished based on their frequency signatures rather than just spatial and Doppler characteristics
3Measurement precision
If TMA systems operate in clutter-limited environments, then target discrimination is improved, but cross-beam reverberation masking increases
Solution Approach 1:
The patent varies the temporal modulation parameters across different array elements to create frequency-diverse beams. This parameter change strategy causes reverberation from different beams to appear at different frequencies, allowing the receiver to filter and process each beam's reverberation separately, thereby reducing cross-beam reverberation masking and improving target discrimination in cluttered environments
4Device complexity
If receiver architecture is simplified, then system complexity is reduced, but signal processing capability may be compromised
Solution Approach 1:
The patent introduces an intermediary frequency domain processing stage that acts as a mediator between the simplified receiver architecture and the complex signal processing requirements. By transforming spatial-temporal signals into the frequency domain through Fourier transforms, the system can perform complex beam separation and target detection using relatively simple filter banks and spectral analysis, rather than requiring complex spatial processing hardware
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
Enhances target interrogation by minimizing receiver architecture complexity, reducing cross-beam clutter or reverberation masking, and optimizing beam steering under various geometric constraints, improving signal-to-masking ratio and detection accuracy.
Implementation Method 1
time-modulating each array element of a transducer array to produce simultaneous beam steering, where each beam is associated with a different carrier frequency
Implementation Method 2
acoustic transmissions
Data Source
AI summary
A method for generating a spatial distribution of acoustic transmitting frequencies by a time modulated array (TMA) of transducers includes generating, by a tapped delay line, a plurality of pulsed sampling signals, wherein each pulsed sampling signal includes a series of frequency harmonics and successive signals of the plurality of pulsed sampling signals are separated by a predetermined delay time; mixing each of the plurality of pulsed sampling signals with a time-limited information signal wherein a plurality of mixer output signals is generated; bandpass filtering each of the plurality of mixer output signals; generating a first plurality of simultaneous TMA beams from the plurality of filtered and weighted output signals by driving a plurality of acoustic transducers in a spatial array of acoustic transducers, wherein each beam of the first plurality of simultaneous beams is associated with one of a plurality of transmitting carrier frequencies