A Colpitts-Type Crystal Oscillator for Gigahertz Frequency

Recent research shows that stable frequency is required to improve efficiency in the high frequency range. A high frequency oscillator has been required for the development of radio communications, measurement equipment, etc. Generally, the crystal oscillator is excellent in short-term frequency stability, and is being applied to telecommunication equipment, information technology, etc. On the other hand, the quartz resonator, which was developed for high frequency range, is aimed at being used in systems for the next generation. The quartz resonator with the high frequency range requires a steady oscillator to oscillate in high frequency range. Therefore, it is very difficult to use a Colpitts-type crystal oscillator in the high frequency range. It requires more negative resistance on the crystal oscillator circuit. In this paper, we suggest a method to decrease Miller capacitance of the transistor used for the conventional Colpitts-type crystal oscillator. Next, we show a new Colpitts-type crystal oscillator, which can obtain a negative resistance value in a gigahertz frequency band. Analyzing the equivalent circuit clarifies the effects of the proposed circuit compared to the conventional Colpitts-type crystal oscillator