Equivalent Circuit Model for Varactor-Loaded Reconfigurable Intelligent Surfaces

Reconfigurable intelligent surfaces (RIS) have gained a lot of attention due to its ability to perform low-cost beam steering for applications in emerging smart radio environments. An equivalent circuit model for a varactor-loaded microstrip RIS element, covering a wide tuning range and providing accurate physics-based circuit model for both reflection phases and magnitudes for a normal incidence is developed and presented. The circuit model facilitates system level study of RIS-based wireless communication networks with realistic analytical RIS responses as parameter inputs.