WiXI: An Inter-Chip Wireless Bus Interface for Shape-Changeable Chiplet-Based Computers

Herein, we propose a wireless bus interface that can connect multiple chips to form a flexible system. In the proposed bus interface, on-chip coils are formed along the outer periphery of each chip, and high-speed wireless communication between multiple chips is enabled via horizontal inductive coupling between coils. Using the proposed interface, embedded computer systems can be realized by simply combining small chips with different functions as needed and arranging them in an adjacent manner. The proposed bus interface enables variation in the relative angle between adjacent chips during operation, can be implemented in complicated shapes, and facilitates chip replacement post fabrication to achieve flexible and robust computer systems; such systems can be applied in micro-robots and wearable interfaces. In this paper, we present a theoretical analysis of electromagnetic coupling between coils, electromagnetic field simulation results, and circuit simulation results of transmitter and receiver circuits. Through the simulation conducted using 45 nm CMOS technology, we realized high-speed communication of 14.3 Gb/s with a power efficiency of 0.55 pJ/b using the proposed bus interface. We also verified the data collision detection ability of the proposed bus interface using a collision detection circuit and packet transfer based on a SerDes circuit.