Coupled relaxation oscillators for frequency multiplication

Relaxation oscillators with microbridges as hysteretic elements are investigated in a frequency range of up to 1 GHz. The signal form of the voltage pulses and the resulting frequency versus bias current dependence are calculated, as well as the frequency spectrum of the harmonics. To demonstrate the possibility of a frequency multiplication, several relaxation oscillators are coupled in a serial or ring configuration. Superconducting delay lines are used to synchronize the oscillators to each other with the proper phase shift. As our measurements show, a frequency multiplication, or at least an enhancement in the power of the desired harmonic is possible in this way.