Fully Digital BPSK Demodulator and Multilevel LSK Back Telemetry for Biomedical Implant Transceivers

A novel fully digital binary-phase-shift-keying (BPSK) transceiver for forward data telemetry and a multilevel load-shift-keying (LSK) transceiver for passive back telemetry are implemented. The digital architecture for the BPSK demodulator allows for much less power consumption compared with prior art. The basic premise of the demodulation is to regenerate the incoming BPSK signal using a digital phase-locked loop. We demonstrate the silicon realization of the BPSK demodulator operating at 13.56 MHz in a 0.5-mum complementary metal-oxide-semiconductor process with power consumption of 2.3 mW. The silicon area is 536 times 546 mum². A novel multilevel LSK for passive back telemetry is implemented, and it works by modulating the load impedance at the implant to create distinct reflections at the primary coil of the reader. The reflections at the reader are decoded for data information using a discrete realization of highly sensitive LSK receiver. The simulation and measurement results indicate 2times improvement in data rate compared with conventional bilevel back telemetry. This brief also shows the implementation of a forward BPSK modulator based on a class-E power amplifier to complete a full biomedical implant transceiver implementation.