1-bit Digital Phase Shifter Active RIS Element Based on Dual-Input Ka-band LNA in 130 nm SiGe BiCMOS Technology

In this paper a novel 1-bit phase shifter topology based on dual input Low Noise Amplifier (LNA) for Active Reflective Intelligent Surfaces (Active RIS) is presented. The proposed solution is advantageous when the LNA has to be switched between two different radio-frequency (RF) sources. In particular, the Active RIS receiving (RX) patch antenna has two opposite feed points in order to obtain a 0° and 180° phase shifted signals entering the dual input LNA. A 1-bit digital enable (EN) signal is used to select one of the two inputs at a time, making the LNA behaves as pseudo-switch. Experiments were carried out on a fabricated prototype. The reported results show good agreement with simulations, thus validating the LNA operation. The LNA is based on a 130 nm SiGe BiCMOS technology, operating between 20 and 30 GHz with a 13 dB gain and 3 dB noise figure.