Wireless polar receiver using two injection-locked oscillator stages for green radios

Direct-conversion receiver is the most prevalent receiver architecture today for wireless communications. However, it requires coherent demodulation using the phase-locked loop (PLL)-based carrier recovery techniques, which increases circuit complexity and power consumption of the receiver. This paper presents a novel polar receiver that utilizes two injection-locked oscillators (ILO) stages to extract the modulation envelope and phase components from a received non-constant envelope modulation signal without using carrier recovery circuitry. The implemented prototype can perform π/4 DQPSK and QPSK demodulation with error vector magnitudes (EVM) of 7.5% and 8.2%, respectively, both at 2 Msps and a received power of -40 dBm. Owing to its simplicity, the proposed receiver has great potential as an energy-efficient architecture with low cost for green radio applications.