A Wideband Flexible Power Upconverter for Software Defined Radios

Abstract— In a multi-standard radio transmitter it is common practice to use multiple narrowband PA’s and filters: one for each standard and a switch before them. With the ever increasing number of different standards to be supported, this architecture becomes increasingly unpractical, as support for every new frequency band requires adding a dedicated external filter. Use of these discrete filters reduces the level of integration, thus making it difficult to realize low cost multi-radios on a single RF chip. This paper presents a polyphase multipath technique to relax or eliminate filters by canceling harmonics and sidebands. Using this technique, a wideband and flexible power upconverter with a clean output spectrum is designed in a 0.13μm CMOS for a software defined radio application. Additionally, a 33% duty cycle is used to cancel the problematic 3rd harmonic of the LO. The demonstrator prototype of the proposed power upconverter operates from DC to 2.4GHz with spurs <-40dBc over more than a decade in frequency. It can deliver 8dBm of power to a 100Ω load and consumes 228mW from a 1.2V supply. It uses no filters but only digital circuits and mixers, and no tuning of components is required.