Low Phase Noise Operation of Microwave

In this paper, we describe a theoretical basis, leading to new results, on the general conditions to be ful- filled by oscillator circuits to achieve a very low phase noise. Three main conditions must be fulfilled by a transistor os- cillator circuit to reach the minimum phase noise. The energy stored in the resonator must be maximum. Its transfer to the controlling voltage port of the tran- sistor current source must be first maximized. A possible conversion noise at the transistor output port will be also minimized by maximizing the energy transferred to that port. The proposed method has been applied to an experimen- tal oscillator set up with PHEMT transistor. A state-of-the- art phase noise of-80 dBc/Hz at 100 Hz offset from carrier with a 1 3 slope has been measured at room temperature with a 9.2-GHz oscillator. The application of these new re- sults to free-running oscillator circuits with one-stage then multistage transistor amplifiers demonstrate clearly the va- lidity of the design method. The efficiency of this design method and its ease of use represent a real breakthrough in the field of low noise transistor oscillator circuit design.