A 0.65V 1.2mW 2.4GHz/400MHz dual-mode phase modulator for mobile healthcare applications

Abstract

A 0.65V 2.4GHz/400MHz digital-intensive phase modulator is implemented in 65nm CMOS. In ultra-low voltage design, the two-point modulator suffers a lot from the DCO nonlinearity. In this work, we employ a 2.4GHz semidigital fractional-N PLL with an FIR filter embedded 1-bit high-pass modulation to overcome the nonlinearity problem in the conventional two-point modulator. The 400MHz modulator performs an FIR-embedded OQPSK modulation to reduce the spectral regrowth in high frequencies. For compact area and low voltage design, an inverter based phase interpolator with a harmonic filtering technique is designed after generating multiphase signals directly from the 2.4GHz output. The 1Mb/s GFSK 2.4GHz and the 10Mb/s OQPSK 400MHz modulators consume 0.94mW and 1.2mW and achieve the EVM values of 5.7% and 6.4% respectively.