Reverberation Cavity Time Reversal for High-Power Pulse Compression
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Solution Overview
Problem
Existing methods for generating high-power waves using reverberant cavities are limited by hardware constraints, reduced dynamics of filtering and clipping systems, and strong sampling frequency constraints, which restrict the achievable gains and the ability to produce carrier-modulated signals with steep wavefronts and controlled pulse durations.
Innovation Solution
A method involving cavity calibration and time reversal phases that utilize digital techniques to generate and transmit high-power signals, including steps such as generating Dirac distribution signals, digitizing impulse responses, and applying digital modulation and amplification to achieve improved signal generation and compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If direct synthesis of the returned signal is used, then the signal can be generated, but hardware constraints and reduced dynamics of filtering and clipping systems limit the achievable gains to 15 dB
Solution Approach 1:
The patent replaces direct analog synthesis with digital signal processing. The returned signal is generated digitally by convolving the transmitted signal with the measured cavity impulse response, then converted to analog form. This substitution of digital processing for analog filtering and clipping systems eliminates the hardware constraints that limited compression gains to 15 dB, enabling achievement of 20 dB or more.
2Power
If digital filtering generation and processing with DAC is used, then better signal processing is achieved, but strong constraints on sampling frequency limit the maximum frequency to half the sampling rate
Solution Approach 1:
The patent addresses the sampling frequency constraint by operating in the digital domain where sampling limitations can be overcome through appropriate filter design and signal processing techniques. The digital convolution approach allows the system to effectively handle frequencies up to the cavity bandwidth regardless of the DAC sampling rate, by processing the signal in the time domain and using anti-imaging filters to reconstruct the analog signal with the desired spectral characteristics.
3Device complexity
If analog generation is used, then the system is simpler, but reduced dynamics of filtering and clipping generation systems reduce achievable gains
Solution Approach 1:
The patent replaces the complex analog filtering and clipping systems with digital signal processing. Instead of using analog filters with limited dynamics range, the system uses digital convolution to generate the returned signal, which is then converted to analog form. This substitution maintains relative system simplicity while dramatically improving the achievable compression gains from 15 dB to 20 dB or more.
4Speed
If the cavity bandwidth is 1 GHz -10 GHz, then high frequency coverage is achieved, but direct synthesis limited to 5 GSPS only allows maximum frequency of 2.5 GHz
Solution Approach 1:
The patent operates in the digital time domain to generate the returned signal through convolution, then uses a DAC with anti-imaging filtering to reconstruct the analog signal. This approach allows the system to achieve the full 1 GHz -10 GHz cavity bandwidth coverage despite the 5 GSPS sampling rate limitation, because the digital processing can generate frequency components beyond the Nyquist frequency that are then properly reconstructed in the analog domain.
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 allows for increased bandwidth and frequency range, reduced sampling frequency constraints, and improved control over output waveforms, achieving compression gains beyond 20 dB and enabling the generation of high-power, impulsive signals with reduced complexity and relaxed amplifier dynamics.
Implementation Method 1
The principle is based on the time reversal technique illustrated in the Fig.1
Implementation Method 2
Method for generating a high power wave using a reverberation cavity system
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The invention relates to a method for generating and emitting a high-power signal composed of a plurality of Dirac distribution type signals, by means of a high-power signal generation and emission system equipped with a reverberating cavity, and comprising a cavity calibration phase over a calibration time and a time-reversal phase of a signal before its injection into the cavity.