An Incremental-Charge-Based Digital Transmitter With Built-in Filtering
 
An Incremental-Charge-Based Digital Transmitter With Built-in Filtering ■
 
Pedro Emiliano Paro Filho, Pedro Emiliano Paro Filho, Pedro Emiliano Paro Filho, Mark Ingels, Mark Ingels, Mark Ingels, Piet Wamback, Piet Wamback, Piet Wamback, Jan Craninckx, Jan Craninckx, Jan Craninckx
 
Abstract ■

A fully integrated transmitter architecture operating in the charge-domain with incremental signaling is presented. The architecture provides improved out-of-band noise performance, thanks to an intrinsic low-pass noise filtering capability, reduced quantization noise scaled by capacitance ratios, and sinc 2 alias attenuation due to a quasi-linear reconstruction interpolation. With a respective unit and baseband capacitances of 2 fF and 45 pF, the architecture attains a potential 14 bit equivalent quantization noise with a 1024 unit capacitance array. Using four 10 bit charge-based DACs (QDACs) at 128 MS/s sampling rate, it achieves -155 dBc/Hz at 45 MHz offset from a 1 GHz modulated carrier. The incremental-charge-based operation also leads to an improved efficiency at back-off conditions. For an average output power of 1 dBm (20 MHz BW), total power consumption is 41.3 mW, of which only 0.5 mW corresponds to the system charge intake. The prototype is implemented using a 28 nm 0.9 V CMOS technology, with a core area of 0.25 mm 2 . With a reduced sampling frequency and number of bits, power and area consumption are among the best and will directly benefit from future technology scaling .