Publication
Active retrodirective antenna arrays find a variety of use in applications involving wireless communication and sensing systems. This article presents a novel active version of the phase-conjugating Rotman lens with negative conductance amplifiers for applications requiring high retrodirective gain or modulation capability. Implementation challenges and limitations of extending the existing passive retrodirective Rotman lens into this enhanced active mode are described. In order to retain system stability when electrically connecting multiple potentially unstable devices, a narrowband negative conductance is designed specifically for augmenting onto the lens. The measurements demonstrate an eleven-antenna element lens with a phase-conjugating gain of 19.2-25.4 dB across a 32 scanning range at 5.15 GHz when loaded with nine amplifiers tuned to approximate to 6.5-dB reflection gain. The entire system consumes only 2.4 mW of power. The circuits implemented are easily scalable to higher frequency applications. Therefore, this proof-of-concept phase-conjugating system is a step toward designing very high-gain retrodirective arrays for mm-wave applications.
Sandro Carrara, Diego Ghezzi, Gian Luca Barbruni