Reconfigurable broadband multistandard transmitter


Recent and future portable devices support various standards like legacy GSM, GPRS or UMTS and modern OFDM based communication standards such as WLAN or 4th generation LTE. A reconfigurable high performance RF-frontend could replace multiple parallel radios on the same handheld reducing cost, area and implementation effort dramatically. Next generation mobile communication standards have high demands in linearity whereas nanoscale CMOS transistors are good high speed switches but have a very poor RF performance.

To improve reconfigurabily and at the same time allow compatibility to nanoscale CMOS processes, IAS conducts research on direct digital RF transmitters. These transmitters contain different Direct-Digital-to-RF-frontends which need no linear transistor behavior but fast switches to work properly. One evaluated frontend is the so called RF-DAC which combines DAC and upconversion mixer in a single building block. Thereby, all analog baseband processing blocks can be eliminated and replaced by high-performance, reconfigurable digital signal processing. However, unwanted spurious emissions that could disturb parallel running receivers in neighboring frequency bands are a major issue of this architecture. Therefore, sophisticated techniques to suppress these unwanted emissions are needed.

Bastian Mohr < >
Niklas Zimmermann < >