A micropower CMOS, direct-conversion, VLF receiver chip for magnetic-field wireless applications

A micropower CMOS, direct-conversion VLF receiver is described for receiving low-level magnetic fields from resonant sensors. The single-chip, PLL-synthesized receiver covers a frequency range of 10-100 kHz and provides both analog and digital 9-bit I and Q baseband outputs. Lateral bipolar transistors are utilized for low flicker noise and low DC offsets, and special attention is given to isolating the internal local oscillator signals from the low-level RF input (0.3 /spl mu/V noise floor, 300 Hz BW). The 100% duty-cycle receiver, intended for long-battery life wireless applications, operates at 360 /spl mu/W from a 6-V battery.