A MURS Band Digital Quadrature Transmitter With Class-B I/Q Cell Sharing for Long Range IoT Applications

This brief presents a quadrature digital transmitter operating in the multiuse radio service (MURS) frequency band for low power and long-range Internet of Things applications. We introduce a narrowband modulation scheme compliant with the MURS band as an alternative solution for low data-rate wide-area coverage. We present a transmitter architecture based on switched-current power amplifier cells that uses a digital class-B input codeword profile in combination with 25% duty cycled LOs to achieve high efficiency at low transmitted power levels. The transmitter is implemented in a 65-nm CMOS process and its performance is measured for single-tone and multitone transmissions at 5 and 384 kb/s, respectively. It operates from a 1.2-V supply and delivers a peak efficiency of 41% at a peak output power of 0 dBm. The error vector magnitude at 384 kb/s is 4.2%.