Wireless Interconnect in Electronic Systems

Abstract

Since conventional mechanical connectors have metal contacts that are susceptible to contamination, fatigue, and wear, they are unreliable and failure-prone components of systems. Signal integrity is also degraded due to an impedance discontinuity at the electrodes. To overcome such problems, various kinds of noncontact type wireless interconnection methods have been studied. Noncontact communications that use near-field coupling provide immunity to mechanical damages caused by vibration/friction and isolation from water/chemicals while reducing fabrication costs. A problem for conventional near-field communications such as inductive and capacitive couplings is poor signal integrity due to the impedance mismatch. This chapter introduces the basic concept and features of transmission line coupler (TLC), an impedance-matched and terminated wide-bandwidth coupler enabling signal branching without signal reflections. Two transmission lines are coupled to form TLC, same as microstrip filters. The broadband characteristics enable baseband communication. A 12 Gb/s data link was confirmed by experiments at a distance of 1 mm. A 12.5 Gb/s 8-drop multidrop bus system was also confirmed by experiments by using TLC at each signal branching point. Strong misalignment tolerance of TLC realizes high vibration tolerance too. Under the same vibration as satellite launching and vehicles, no change in the characteristics and no bit errors were confirmed. Analysis and design of coupler and transceiver are presented. Examples of applications are shown. Issues and countermeasures in each application are discussed.