A 180nm CMOS wireless transceiver by utilizing guard band for narrowband IoT applications

A fully-integrated wireless transceiver (TRX) is presented for 750~960MHz narrowband IoT applications by utilizing the guard band of mobile communication systems. The TRX consists of a low-IF receiver with 180 kHz signal bandwidth, a mixed-signal polar transmitter with 3.75 kHz signal bandwidth and a fractional-N frequency synthesizer. Current passive mixer is employed in the low-IF receiver to achieve lower 1/f noise and higher linearity. The on-chip I/Q imbalance calibration is integrated to improve the image rejection ratio (IRR) which could be realized automatically cooperated with one FPGA. The transmitter features polar architecture and inverse class-D PA to achieve high output power and efficiency. The thermometer coding and binary-coding-based array placement simplify the DPA layout and reduce the mismatch between the DPA cells. The RX achieves 4.01dB NF, 48dB IRR and 5~65dB dynamic range. The DPA provides 23.2dBm maximum saturation power with 44.5% PAE. Furthermore, TX system verifications demonstrate 3.87% EVM for 891MHz n/4-DQPSK signals at 18.87dBm output power with -40dBc out-of-band rejection. The transmitter achieves a dynamic range from -35dBm to 20dBm while the demodulation threshold of the system is 10% (EVM).