A novel BPSK demodulator for biological implants

A novel binary phase-shift keying (BPSK) demodulator architecture is presented. The design employs a phase frequency detector based phase-locked loop allowing for robust performance compared to prior art. Two different circuit implementations for the novel demodulator architecture are proposed. Based on theoretical analysis, the maximum data rate of the demodulator is derived to be 1/8th of the carrier frequency. For experimental validation, a prototype was implemented for a 13.56-MHz BPSK demodulator in a 0.5-[micro]m CMOS technology. The circuit occupies 1 [mm.sup.2] chip area and consumes 3-mW power without any circuit optimization and can be further improved. Bit-error rate measurements have also been presented for a 20-kbs data rate. Index Terms--Biological implant, biomedical implant, binary phase-shift keying (BPSK) demodulator, charge-pump (CP) phase-locked loop (PLL), wireless implant.