A Dielectric Resonator-Based Microwave Plasma Jet

This study introduces a cylindrical dielectric resonator placed on a metallic ground plane, which is excited by a slot etched through the ground plane. A simple feeding mechanism based on microstrip technology is utilized to couple the input microwave energy to the resonator. Achieving impedance matching is accomplished by adjusting the position of the microstrip line relative to the slot. By effectively suppressing radiation, the energy surrounding the device experiences a significant enhancement, which, combined with a controlled gas flow through the device, leads to gas breakdown. Consequently, a highly efficient atmospheric pressure microwave plasma jet is formed.

Compared to previous studies, the proposed device exhibits several significant advantages: It is highly compact, fully planar, and has a low profile, making it suitable for integration and compatible with printed circuit board fabrication techniques. Additionally, the device offers a cost-effective solution. One notable feature of the proposed device is its frequency reconfigurability, allowing it to operate across a wide frequency range. The final prototype of the device was developed to operate at 890 MHz, achieving a compact size of just 0.1λ. The agreement between numerical simulations and experimental results of the reflection coefficient confirms the device's performance reliability. The simulations reveal a highly concentrated electric field of up to 5×10⁶ V/m in the desired region. This enables the device to operate at low power levels while maintaining a high electron density through controlled gas flow rates. With its low profile, electronic frequency tunability, low operating power requirements, and minimal heat generation, the proposed device is an excellent candidate for high-density plasma jet applications in medicine and agriculture.