A frequency-flexible radio-frequency (RF) front end has long been desired, but faces a myriad of obstacles to its realization. In recent years, the use of switching power amplifiers (PA) as part of digital PAs and RF digital-to-analog converters (RFDACs) has become more common. The primary motivation of these RFDACs is to directly convert from digital baseband bits to RF output. This is useful in the realization of a frequency-flexible RF front end, but this is prevented by the generation of significant spectral emissions in the form of harmonics and quantization noise by RFDACs. These issues are both typically remedied with the usage of high-order fixed filters which are inherently not frequency flexible.

In this dissertation, we will discuss an approach to implement a frequency-flexible digital PA-based transmitter using programmable integrated filtering to suppress spectral emissions without the use of external filters. Two filtering techniques will be discussed, as well as their requirements and limitations. Additionally, design automation of core blocks within the transmitters using the Berkeley Analog Generator (BAG) framework will be discussed in detail. We will demonstrate two prototypes implemented in 65nm and 28nm processes achieving state of the art filtering performance at a peak power level of > 23 dBm across at least a 1 GHz - 2 GHz frequency range.