A novel hybrid two-stage IM2 cancelling technique for IEEE 802.15.6 HBC standard

Body channel communication (BCC) is one of the best candidates for facilitating communications among multiple sensors in a wireless body area network (WBAN). The low transmission loss and antenna-less communication makes it well suited for wearable wireless biomedical sensors. The IEEE 802.15.6 standard for Human Body Communication (HBC) placed a very stringent requirement on transmit spectral mask, i.e., -120 dBr at frequencies lower than 1 MHz. As a result, the second-order intermodulation (IM2) products of the transmitting signal must be reduced to satisfy the given HBC spectral mask. In this work, we proposed a novel hybrid two-stage IM2 cancelling technique for the body surface driver. The first stage uses homogeneous transistors to remove part of the IM2 distortion. The second stage utilizes complementary NMOS and PMOS transistors to cancel the residual of IM2 products from the first stage. Designed in 0.35 μm CMOS process under a supply voltage of 1.8V, the proposed driver achieves a spectrum mask of -122 dBr at 1 MHz, which satisfies the IEEE 802.15.6 HBC spectral mask requirement.