The selection of materials with different Dk values plays a crucial role in high-frequency applications. Insertion loss, a key factor in these applications, encompasses four components: conductor loss, dielectric loss, leakage loss, and radiation loss. Conductor loss is influenced by surface roughness, while dielectric loss is determined by the dissipation factor of the circuit material. Leakage loss is typically not a concern for high-frequency circuit materials due to their high volume resistivity. On the other hand, radiation loss, the amount of energy radiated off the circuit, is generally undesirable as it increases signal loss and can interfere with neighboring circuitry. Factors such as circuit design, substrate thickness, PCB fabrication anomalies, substrate Dk, and frequency impact radiation loss. High-frequency circuits using materials with lower Dk values tend to exhibit increased radiation loss, whereas those with higher Dk values experience reduced radiation loss. Additionally, Dk influences circuit size, with lower Dk materials corresponding to longer wavelengths. Coupled features in RF engineering, connected by electric fringing fields, are critical for various RF applications, and the strength and intensity of these coupled fields vary with Dk dependency. Considering these aspects, the choice of materials with different Dk values becomes essential to optimize performance and meet specific requirements in high-frequency applications.