Hybrid-pair ratio adjustable power splitters for add-on RF shimming and array-compressed parallel transmission

Area of Science:

• Electrical Engineering
• Radio Frequency (RF) Engineering
• Magnetic Resonance Imaging (MRI)

Background:

• Ratio adjustable power splitter (RAPS) circuits are crucial for advanced RF applications like shimming and parallel transmission.
• Previous RAPS designs relied on custom-built components, limiting performance and manufacturability.

Purpose of the Study:

• To introduce a novel hybrid-pair RAPS (HP-RAPS) circuit design.
• To enhance performance and manufacturability using commercially available components.

Main Methods:

• Replaced custom Wilkinson splitters and hybrid couplers with two commercial hybrid couplers.
• Utilized interchangeable microstrip lines instead of connectorized coaxial cables.
• Derived splitting ratio and phase shift relationships for HP-RAPS and investigated ratio generation using microstrip lines.

Main Results:

• Fabricated HP-RAPS circuits demonstrated accurate splitting ratios with <4% deviation.
• Achieved low insertion loss (0.33 dB), high output isolation (-26 dB), and good impedance matching (-16 dB).
• Generated transmit fields that closely matched predicted fields in MRI experiments.

Conclusions:

• Developed a novel, easy-to-fabricate HP-RAPS circuit.
• Preserves RAPS features like ratio adjustability and small footprint.
• Offers improved performance, including lower insertion loss, compared to previous designs.