Balanced UWB Coupler Layout for Low-Reflection Mono-Static GPR
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Solution Overview
Problem
Conventional ground-penetrating radar (GPR) scanners with separate transmit and receive antennas are limited in size due to physical dimensions, and existing directional couplers are not optimized for GPR antennas with specific impedance requirements, leading to higher internal reflections and reduced performance.
Innovation Solution
A balanced ultra-wide band (UWB) directional coupler optimized for mono-static GPR antenna designs, featuring a configuration with balanced ports and waveguide structures to reduce internal reflections and interface with 100-Ohm impedance, while maintaining immunity to external interferences and achieving identical directivity and coupling performance as unbalanced setups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate transmit and receive antennas are used in a bi-static arrangement, then the GPR scanner achieves proper signal transmission and reception performance, but the physical dimensions of the antennas limit the ability to reduce the size of the GPR scanner
Solution Approach 1:
The patent combines separate transmit and receive antennas into a single mono-static antenna that performs both functions. The antenna is designed with specific geometric parameters (width W=10mm, length L=30mm, spacing D=20mm) to enable it to both transmit and receive signals effectively, thereby reducing the overall scanner size while maintaining signal performance
Solution Approach 2:
The patent introduces a directional coupler as an intermediary device to separate transmit and receive signals within the mono-static antenna system. The coupler with specific coupling coefficients (C12=-10dB, C21=-20dB) acts as a mediator that directs signals appropriately, enabling the single antenna to function as both transmitter and receiver without interference
2Volume of moving object
If a single antenna is used for both transmit and receive functions in a mono-static design, then the GPR scanner size is significantly reduced, but internal reflections from antenna interfaces increase and performance deteriorates
Solution Approach 1:
The directional coupler serves as an intermediary device that separates transmit and receive signal paths within the mono-static antenna system. By introducing this intermediate component with specific coupling characteristics (C12=-10dB, C21=-20dB), the system reduces internal reflections and interference between transmit and receive functions
Solution Approach 2:
The patent optimizes specific geometric parameters of the antenna (width W=10mm, length L=30mm, spacing D=20mm) and the directional coupler (coupling coefficients C12 and C21) to minimize internal reflections. By carefully adjusting these parameters, the system achieves reduced harmful reflections while maintaining the compact mono-static design
3Adaptability or versatility
If standard 50-Ohm impedance directional couplers are used with GPR antennas, then the directional coupler provides standard interface compatibility, but the impedance mismatch with GPR antennas (100-Ohm) results in higher internal reflections and reduced dynamic range
Solution Approach 1:
The patent changes the impedance parameter of the directional coupler from the standard 50-Ohm to 100-Ohm to match the GPR antenna impedance. This parameter change eliminates impedance mismatch, thereby reducing internal reflections and improving dynamic range while maintaining interface compatibility through the adapted impedance design
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
The solution enables a more compact and performant GPR scanner with reduced internal reflections, improved noise rejection, and enhanced dynamic range, facilitating superior compactness and performance over existing implementations.
Implementation Method 1
To separate TX signals from RX signals, the use of a directional coupler is known in the technical field of radio frequency (RF).
Implementation Method 2
keeping the advantage of the balanced scheme about the 'immunity' from external interferences
Data Source
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AI summary
The invention relates to a ground-penetrating radar (GPR) scanner for investigating a sub-surface, wherein the GPR scanner comprises an antenna assembly (12) configured for transmitting and receiving ultra-wide band (UWB) signals. The GPR scanner further comprises a directional coupler (10), a UWB signal generator (11) configured for providing outgoing UWB signals through the directional coupler to the antenna assembly, a UWB signal sampling unit (13) configured for receiving incoming UWB signals from the antenna assembly through the directional coupler, and an impedance (14). The directional coupler (10) is configured as a balanced UWB directional coupler. It comprises a first port (16) configured for receiving positive outgoing UWB signals from the UWB signal generator and a second port (17) configured for receiving negative outgoing UWB signals from the UWB signal generator (11), wherein the second port is balanced with the first port. A third port (20) and a fourth port (21) are both connected to the impedance (14), wherein the fourth port is balanced with the third port. A fifth port (18) is configured for outputting the positive outgoing UWB signals to the antenna assembly and for receiving positive incoming UWB signals from the antenna assembly, wherein a sixth port (19) is configured for outputting the negative outgoing UWB signals to the antenna assembly (12) and for receiving negative incoming UWB signals from the antenna assembly, the sixth port being balanced with the fifth port. A seventh port (22) is configured for outputting the positive incoming UWB signals to the UWB signal sampling unit (13) and an eighth port (23) is configured for outputting the negative incoming UWB signals to the UWB signal sampling unit (13), wherein the eighth port is balanced with the seventh port.