Reduction of harmonics and noise of microwave oscillators

Oscillators generate harmonics and noise which degrade the signal in many applications (e.g. mixers). To avoid these effects it is important to reduce the power of the harmonics and the phase noise of oscillators. Common methods use bandpass filter at the output of the oscillator to reduce the power of the harmonics. In other methods for decreasing the phase noise of the oscillator a bandpass filter with high quality factor is applied in the feed-back loop of the oscillator. In this paper we show two additional new approaches for reducing the power of the harmonics and the phase noise of the oscillators without the use of filters in the case of negative resistance oscillators.