24 GHz beam forming network for indoor positioning systems

In this paper, an innovative design for on-chip 8×8 Butler matrix in SiGe BiCMOS technology is proposed. The proposed component is designed for 24 GHz radar applications and it is implemented using the BiCMOS9MW ST Microelectronic process, which is a standard 0.09-μm SiGe BiCMOS technology. An innovative approach was taken into account by implementing the 90-degree hybrid through an on-chip transformer. Thanks to this solution, it was possible to achieve a considerable reduction of the chip area and an improvement of the Butler matrix performance both in terms of phase linearity and in terms of operating bandwidth. The resulting overall size of the Butler matrix is 714 um × 650 um.