Ground Penetrating Radar Waveform Sampling Using Periodic Duty Cycles
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Solution Overview
Problem
Existing ground penetrating radar systems face challenges in high-speed and high dynamic range signal processing, managing large amplitude direct coupling signals, and limiting electromagnetic emissions, while also requiring expensive high-speed Analog-to-Digital Converters for full waveform digitization.
Innovation Solution
A real-time, low-cost Application Specific Integrated Circuit (ASIC) is used for partial-duty-cycle full-wave sampling in an Ultra-Wideband Impulse Ground Penetrating Radar system, sampling only the information-laden portion of the waveform at high speed and storing data in a discrete-time analog-amplitude memory buffer, with a modest-performance ADC digitizing during idle times, reducing the number of launch signals and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full waveform digitization is used with high-speed ADCs, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The waveform sampling process is segmented into two distinct phases: (1) high-speed sampling during the pulse duration to capture the information-laden portion with sufficient precision, and (2) low-speed sampling during the idle time to maintain continuous operation. This segmentation allows the system to achieve full waveform digitization without requiring expensive high-speed ADCs for the entire cycle, thereby reducing device complexity and cost while maintaining measurement precision for the critical signal portion.
Solution Approach 2:
The system employs periodic pulsed transmission with duty cycles typically less than 1%, where the transmitter operates at high power only during brief pulse intervals and remains idle for the majority of the cycle. The sampling operation is synchronized to this periodic action, performing high-speed acquisition during pulses and low-speed acquisition during idle periods. This periodic approach enables the use of modest-performance ADCs that can operate continuously at lower speeds, reducing device complexity while maintaining the ability to capture complete waveform information.
2Productivity
If high-power pulses are transmitted frequently, then productivity is improved, but electromagnetic emissions exceed regulatory limits
Solution Approach 1:
The system uses low-duty-cycle periodic pulsing where the transmitter operates at high power only during brief intervals (typically <1% duty cycle) and remains idle for the majority of the time. This periodic operation allows the system to maintain high productivity during active pulses while keeping average electromagnetic emissions below regulatory limits. The receiver operates continuously at low power during both pulse and idle periods, further reducing overall emissions while maintaining surveying capability.
Solution Approach 2:
The receiver is prepared and operating in advance during the idle period, with buffers pre-allocated and processing circuits ready, so that when the high-power pulse occurs, the system can immediately capture and process the return signal without interruption. This preliminary preparation during idle time enables high productivity during pulses without requiring continuous high-power transmission, thereby keeping electromagnetic emissions within regulatory limits.
3Measurement precision
If continuous high-speed sampling is performed, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The sampling operation is performed periodically at two different speeds: high-speed sampling during pulse intervals to capture the information-laden portion with maximum precision, and low-speed sampling during idle intervals to maintain continuous operation with minimal energy consumption. This periodic dual-speed approach allows the system to achieve high measurement precision when needed while dramatically reducing average power consumption during the majority of the cycle when no signal is present. The receiver can use modest-performance ADCs operating continuously at lower speeds, further reducing energy use compared to requiring high-speed ADCs to operate continuously.
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 the bandwidth requirements and costs, enabling efficient detection of subsurface features while complying with regulatory emission limits, achieving high-resolution and deep penetration capabilities with reduced radiation.
Implementation Method 1
Each system incorporates a transmitter having an antenna that radiates or emits a short pulse of radio frequency, typically in the frequency range from 1 MHz to 10 GHz, into the sub-surface medium
Implementation Method 2
Wherever there is a change in the electrical properties in the ground, part of the pulse is reflected and part of the pulse propagates into the next layer
Data Source
AI summary
An improved Ground Penetrating Radar (GPR) system is provided. The system advantageously employs full waveform digitization of a returning signal to significantly reduce the number of launch signals and allowing the amount of radiation emitted to stay within the limit set by the Federal Communications Commission (FCC), while producing a robust information detection signal. In addition, intermittent large latent-duty-cycle sampling employs a less expensive digitizer typically used in prior art GPRs. The system is scalable at low-cost to accommodate multi-antenna multi-static testing for subsurface tomographic imaging.