We propose a universal magnetic-free scheme to achieve phase nonreciprocity. The scheme requires only two tunable phase shifters and a proper length of the delay line. The phase shifter can be tuned to provide phase shifts $\delta$ and $\delta +\pi$ over a wide bandwidth. When passing through the two phase shifters, in the forward direction, signals acquire the same phase shift, $\delta$ or $\delta +\pi$. However, in the backward direction, signals acquire different phase shifts; one is $\delta$, and the other is $\delta +\pi$. We use superconducting elements to build up such a gyrator and use it as the nonreciprocal path in a circulator. The circulator can achieve 15-dB isolation across the 4.92–8.76-GHz band. We can cascade two such circulators to get an isolator of more than 20-dB isolation in the frequency range of 4.16–9.33 GHz. The scheme can be easily applied to other platforms such as rf communication systems and nanophotonics.

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• Quantum circuits
• Superconducting RF
• Superconducting devices