Design of a X-band GaN oscillator: from the low frequency noise device characterization and large signal modeling to circuit design

Although GaN technologies were initially developed for solid state source amplifiers, it was recently demonstrated that AlGaN/GaN HEMT transistors were also suitable for low noise applications such as LNA (Tartarin et al., 2005). The frequency synthesis is not yet widely explored for these technologies. In this paper the design of a low phase noise X-band oscillator is proposed. The low frequency noise performance and the residual phase noise, as well as dynamic S-parameters were carried out on AlGaN/GaN HEMT grown on SiC. A large-signal modeling technique is also presented. The reduced complexity and the good accuracy of our large signal model permits an efficient circuit design, without intensive knowledge of the technological device parameters. These characterization and modeling tools are used for the design of an 1-stage oscillator working at 10 GHz delivering 20dBm