Mode-Diverse Wave-in-Substrate Antenna for Coexisting Travelling and Standing Waves

Future wireless systems aiming at digital-twin and integrated sensing and communication (ISAC) scenarios require antennas capable of supporting multiple functions within compact platforms. This work presents a mode-diverse wave-in-substrate antenna that exploits the natural dielectric image line (DIL) geometry to host coexisting transverse-magnetic (TM) and transverse-electric (TE) modes for the first time. An improved perturbation structure enhances their separation, allowing the TM mode to form a controllable travelling-wave radiation channel while the TE mode establishes a stable standing-wave resonance. Based on the modal analysis, a prototype incorporating 16 standing-wave elements and a continuous TM branch is developed, achieving approximately 55° forward scanning range with two complementary beam-forming regimes. The results verify that the substrate itself can act as a multifunctional electromagnetic region once its internal mode diversity is properly harnessed. The proposed approach provides a compact and versatile solution toward multimode, multifunctional antennas for next-generation intelligent wireless front-ends. © 2025 IEEE.