Non-ideal modulation effects in Doppler frequency shift control using metasurface

In response to the poor modulation effect of metasurfaces in modulating Doppler frequency shifts due to non-ideal modulation waveforms, this paper proposes an analysis model for metasurface modulation effects based on non-ideal stepped voltage waveforms. Due to the interaction and coupling between nonlinear components such as PIN diodes and varactor diodes with metasurface structure, the non-ideal effects become more complex and difficult to analyze. This model simulates output conditions under various modulation frequencies using stepped voltage waveforms with different rise and fall times. According to the reflection coefficients of metasurfaces at different voltage values, within the modulation cycle, the voltage waveform is converted into the reflection coefficient sequence after metasurfaces modulation. After performing a Fourier transform, the spectrum is obtained, thereby enabling analysis of the impact of non-ideal modulation on each harmonic in the spectrum. An X-band 2-bit phase modulation metasurface prototype verified the effectiveness of the model. Simulation and test results show that this model accurately analyzes non-ideal modulation effects of metasurfaces in Doppler frequency shift control, providing theoretical support for further optimization of non-ideal modulation spectra.