Class E oscillator with electrically elongated feedback network

Class E oscillators are famous for their high efficiency. For their usage in modern electronic equipment, not just their power parameters but the noise characteristics are of interest. This paper describes a High Frequency oscillator design with Low Pass Filter (LPF) included into the feedback network. The LPF acts as a delay line, increasing the phase shift in the feedback network by the integer multiple of 360 degree. As a result, quality factor of the feedback network and frequency stability of the Class E oscillator increase. The phase shift in the proposed feedback network was studied theoretically and experimentally. The oscillator built on 2N7000 transistor showed output power of 0.54 W with efficiency 82% at 4.5 MHz frequency. For proposed oscillator, improved frequency stability with respect to disturbances was demonstrated in comparison with similar oscillators which utilize conventional feedback network.