Simultaneous TX-RX Antenna Signal Subtraction
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Solution Overview
Problem
Conventional magnetic-resonance (MR) machines face challenges in efficiently transmitting high-power RF signals while simultaneously receiving signals without overloading or damaging receive pre-amplifiers, due to the high power of the RF transmit signal and the need for significant coaxial cable losses, which limits the ability to wirelessly couple signals within the MR magnet bore.
Innovation Solution
The solution involves subtracting a subtractable version of the transmit signal from the received signal before preamplification to isolate the net received signal of interest, using a method that includes actively adjusting gains, frequencies, and phases of transmit signals and receive signals, and optionally using wireless connections and distributed power amplifiers to reduce losses and increase flexibility in coil positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high-power RF transmit signals are transmitted through coaxial cables to RF-coil devices, then the transmit signal can be delivered to the magnet bore, but significant signal loss occurs and the system requires heavy shielding and complex cabling
Solution Approach 1:
The system divides the RF coil device into separate transmit and receive coil assemblies, each with independent power amplifiers located at the magnet bore. This segmentation eliminates the need for high-power coaxial cable transmission, reducing signal loss and cabling complexity while allowing wireless coupling between transmit and receive coils
Solution Approach 2:
The patent replaces the mechanical coaxial cable transmission system with wireless electromagnetic coupling between transmit and receive coils. This substitution eliminates physical cable connections, reducing both signal loss and the mechanical complexity of cabling and shielding infrastructure
2Adaptability or versatility
If conventional separate transmit and receive coil assemblies are used, then wireless coupling is possible, but the receive pre-amplifiers are overloaded or damaged by the high-power transmit signal
Solution Approach 1:
The system performs preliminary signal subtraction by removing a subtractable version of the transmit signal from the received signal before it reaches the pre-amplifier. This preliminary action protects the receive pre-amplifiers from overload by eliminating the high-power transmit signal component while maintaining wireless coupling capability
Solution Approach 2:
The patent introduces an intermediary signal processing step that subtracts the transmit signal from the received signal before amplification. This intermediary process acts as a protective mechanism, allowing wireless coupling while preventing the transmit signal from damaging the receive pre-amplifiers
3Reliability
If signal subtraction is performed before preamplification, then receive pre-amplifiers are protected from high-power transmit signals, but the system requires precise signal matching and synchronization
Solution Approach 1:
The system uses feedback control to continuously monitor and adjust the subtractable transmit signal to match the actual transmit signal characteristics. This feedback mechanism ensures precise signal matching and synchronization while protecting receive pre-amplifiers, managing the complexity through active control rather than passive design
4Power
If multiple medium-to-high power amplifiers are used to generate high-power RF signals, then the transmit signal power is sufficient, but combiner circuits incur losses of up to 50% or more
Solution Approach 1:
The patent assigns separate power amplifiers to transmit and receive coil assemblies, eliminating the need for combiner circuits. Each amplifier operates independently at lower power levels, achieving sufficient total power without the 50% or more losses inherent in combiner-based systems
Solution Approach 2:
The system uses multiple lower-power amplifiers instead of fewer high-power amplifiers. This partial action approach distributes the power generation across multiple independent channels, avoiding the excessive losses of combiner circuits while maintaining sufficient total transmit power
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 more efficient and flexible transmission and reception of RF signals, reducing cable requirements, minimizing signal loss, and protecting receive pre-amplifiers, thereby enhancing the quality of MR imaging and spectroscopy data while increasing operational flexibility.
Implementation Method 1
a transmit coil (131) having a characteristic impedance at a respective frequency
Implementation Method 2
a receive coil (132) having a characteristic impedance at a respective frequency
Data Source
AI summary
Apparatus and method that are more efficient and flexible, and obtain and connect high-power RF transmit signals (TX) to RF-coil devices in an MR machine or other devices and simultaneously receive signals (RX) and separate net receive signals NRX) of interest by subtracting or filtering to remove the subtractable portion of the transmit signal (STX) from the RX and preamplifying the NRX and signal processing the preamplified NRX. In some embodiments, signal processing further removes artifacts of the transmitted signal, e.g., by digitizing the NRX signal, storing the digitized NRX signal in a memory, and performing digital signal processing. In some embodiments, the present invention also includes pre-distorting the TX signals in order to be better able to identify and/or remove the remaining artifacts of the transmitted signal from the NRX signal. This solution also applies to other high-power RF-transmit-antennae signals.