Converting a Monopole Emission into a Dipole Using a Subwavelength Structure

Directional emission of sound waves is critical in imaging and communication, yet is held back by the inefficient emission of a small source. This study designs a hybrid resonant structure that converts a monopole emission to a dipole field, improving efficiency while maintaining subwavelength dimensions for the source. The design scheme also enables the flexibility of tuning the working frequency by adjusting the structure's geometrical parameters. This work offers a practical path toward miniaturization in applications that demand efficient emission, such as sonar, loudspeakers, or ultrasound transducers.