A 2.4 GHz High-Efficiency Low Phase Noise Oscillator Using Combined Band Pass Filter for Harmonic Suppression

This paper examines an efficient low phase noise oscillator using a high Q resonator and harmonic suppression filter. The oscillator is designed using a combined bandpass filter (BPF), which is used as a feedback element to an amplifier. The filter consists of an embedded spur line filter in the L-shaped input and output section which encloses a perturbed square ring. All of these sections are assembled to form a combined BPF which gives an excellent suppression of second and third harmonics. Low phase noise oscillator results are evaluated at 2V power supply. The measured results show the fundamental frequency at 2.4 GHz, total output power of 14.92 dBm, phase noise -130.92 dBc/Hz at 1 MHz offset frequency, figure of merit (FOM) -175.64 dBc/Hz, reduction in 2nd and 3rd harmonics to below -45 dBm and DC-to-RF efficiency of 51.73%.