Spectral manipulation in a spoof plasmonic dimer under different excitation configurations

Excitation configuration is often overlooked in the study of a spoof plasmonic dimer (SPD), yet it can significantly influence their spectral response. In this work, we systematically investigate how distinct excitation schemes induce profound changes in the resonance characteristics of the coplanar SPD. Using the temporal coupled-mode theory (TCMT), analytical expressions for the transmission coefficient under different excitation configurations are derived, providing a clear explanation for the evolution of spectral line shapes. By introducing the excitation configuration as an additional degree of freedom in spectral modulation, we demonstrate that excitation conditions, coupling strength, and frequency detuning jointly determine the overall spectral response. The analytical predictions are in excellent agreement with full-wave simulations and experimental results, revealing that the excitation configuration plays a decisive role in shaping the Fano resonance profile. This work not only deepens the understanding of SPD but also offers potential applications in the design of filters, sensors, and integrated microwave devices.