A Compact, High Power Capable, and Tunable High Directivity Microstrip Coupler.

Area of Science:

• Electrical Engineering
• Electromagnetics
• Microwave Engineering

Background:

• Accurate radio frequency (RF) power monitoring is essential for real-time systems.
• The directivity of RF couplers directly impacts the precision of power measurements.
• Existing couplers may face limitations in achieving high directivity for specific applications.

Purpose of the Study:

• To propose and validate a microstrip coupler with a tunable high directivity circuit.
• To enhance the accuracy of reflected RF power measurements.
• To develop a compact and high-power coupler for magnetic resonance imaging (MRI) applications.

Main Methods:

• Design of a microstrip coupler incorporating a passive directivity tuner.
• The tuner adjusts phase and amplitude to cancel leakage signals.
• Experimental validation and simulation of the coupler's performance.

Main Results:

• The proposed microstrip coupler demonstrates a compact size (~ 0.07 λg x 0.05 λg).
• Achieved high directivities exceeding 40 dB at operating frequencies (297.3 MHz, 400 MHz, 447 MHz).
• Exhibits high power capability, supporting up to 1 kW.

Conclusions:

• The microstrip coupler with a directivity tuner offers a viable solution for accurate RF power monitoring.
• The design meets the stringent requirements for MRI applications.
• The tunable directivity circuit effectively improves measurement accuracy and system performance.