FLEXIBLE PRINTED-CIRCUIT BOARDS (FPCBs) are increasingly being used to create lightweight, small-volume modules. At high frequencies, however, it is difficult to achieve stable and low-loss characteristics for FPCBsdespite the many substrate varieties that have been tried. By relying on a polyimide with micromachining fabrication technique, however, a fkexible RF transmitter module on an FPCB claims high fkexibility and low loss at microwave frequencies. This transmitter was developed by Seong-Sik Myoung, Seon-Il Kim, Joo-Yong Jung, Dae-Ho Lim, Jeensang Jang, Yong-Jun Kim, and Jong-Gwan Yoo from Seoul's Yonsei University.

This FPCB transmitter module is designed for a short-distance sensor network based on an orthogonal frequency division multiplexing (OFDM) system. For the proposed RF transmitter, the active devices are designed with an indium-gallium-phosphide (InGaP)/gallium-arsenide (GaAs), heterojunction-bipolar-transistor (HBT), monolithicmicrowave- integrated-circuit (MMIC) process. The passive devices, in contrast, are integrated on the FPCB. The fabricated, flexible transmitter provides conversion gain and error vector magnitude of 27 and -32 dB, respectively. See "A Flexible RF Transmitter Module Based on Flexible Printed Circuit Board by Using Micro-Machining Fabrication Process," Microwave And Optical Technology Letters, Dec. 2010, p. 2636.