A multi-channel OOK/BFSK transmitter with FoM of 99.99/91.2 and HD3/5 <−40 dBc

Abstract

A 423.5–450 MHz low-power OOK/BFSK wireless transmitter (TX) is presented for biomedical applications. The TX utilizes injection locking, frequency multiplication, and harmonic rejection techniques. A frequency synthesizer based on low-frequency phase rotation enables multi-channel support and BFSK modulation. High-frequency quantization noise introduced by the delta-sigma modulator (DSM) is filtered out using an N-path filter and dual multi-phase injection-locked ring oscillators (ILROs). Finally, a harmonic-rejection edge combiner (HREC) is used to achieve 5X frequency multiplication, effectively lowering the operating frequency of other circuits and significantly reducing the system’s power consumption. The HREC provides rejection of the $3\mathrm{rd}$/$5\mathrm{th}$ harmonics while generating the desired carrier frequency. The TX is designed using a 65 nm CMOS process with a core area of 0.0625 ${\mathrm{mm}}^2$. The simulation results show that the TX consumes 985 $\mu$W at 1 V supply voltage and can provide −6.62 dBm output power to a $50\Omega$ load without any on-chip or off-chip inductance, which reduces the chip area. The TX achieves $<$−40 dBc rejection for both $3\mathrm{rd}$ and $5\mathrm{th}$ harmonics, supports data rates of 45/6 Mbps under OOK/BFSK modulation, respectively, achieving energy efficiency of 21.8/164 pJ/bit and FoM of 99.99/91.2.