Design of an RF-DAC in 65nm CMOS for multistandard, multimode transmitters

This work presents a radiofrequency digital-to-analog converter (RF-DAC) in 65 nm CMOS. The RF-DAC combines DAC and mixer functionality in a single building block. It is the basis for a `direct-digital´ vector modulator used in reconfigurable broadband multistandard transmitters for mobile communications. After introducing the basic idea of the RF-DAC, an appropriate transmitter architecture is discussed. Subsequently, a novel RF-DAC circuit implementation based on a Sooch cascode current mirror is presented. The design is optimized for high output power and high efficiency over a broad output power range. Based on the RF-DAC a vector modulator architecture is developed. Simulation results show the feasibility of the concept.