Fully digital-IF based RF-DAC Transmitter

This work presents the first digital-IF based RF-DAC transmitter. This approach uses a digital IF signal to up-convert the baseband data into the IF-band before mixing it with the LO signal based on the proposed technique. The systematic problems like LO-leakage and pulling effect of the VCO on the LO-signal of direct transmission based RF-DACs are eliminated in this new concept. Therefore, higher SNR within the desired bandwidth can be achieved which allows to use complex modulation schemes and, in return, increases the transmitted data rate of the overall system. The digital-IF based RF-DAC consists of unit cells with a segmented architecture and a resolution for 12-bit in the I and Q paths. The chip was designed in TSMC 65-nm CMOS technology. The core size of the chip is 0.4mm(2) and it consumes 150 mW. More than 53 dB of spurious free dynamic range (SFDR) can be handed based on the post-layout simulation results.