Proposing a non‐linear microwave ring resonator for efficient multi‐tone generation

This research proposes a microstrip non‐linear ring resonator (MNLRR) as a frequency comb generator. Due to multiple circulations of waves along the ring, they interact with the non‐linear components several times; thus, in comparison with a microstrip non‐linear transmission line with the same number of non‐linear components, the MNLRR achieves a higher harmonic‐conversion‐efficiency. Furthermore, we distinguish three regimes of multi‐tone generation for the proposed MNLRR. In the first regime of operation, generation of harmonics at integer multiples of the excitation frequency is observed. In the second regime, one recognises generation of spectral lines at the resonance frequencies of MNLRR in addition to degenerate four‐wave mixing tones. Furthermore, we have shown that integer multiples of these spectral components are also excited. In the third regime, we encounter the generation of frequency components whose frequencies are input‐power dependent. According to our measurement results, a higher level of excitation power is required for this regime. Here, the number of components increases while their spacing reduces by growing power level.