The mixers in the device are designed to combine different frequencies of waves together. By carefully adjusting the phase shift between the mixers and the powe

The mixers in the device are designed to combine different frequencies of waves together. By carefully adjusting the phase shift between the mixers and the powers of the local oscillator (LO) applied to each mixer, a specific phase relationship is created for the up-converted signals (upper and lower sidebands) produced by the mixers. When these signals are combined again in a subsequent mixer, they interact in a way that results in different phase relationships for waves traveling in different directions. This means that the waves are in-phase (in sync) for one direction but out-of-phase (out of sync) for the opposite direction. This phase relationship difference causes an asymmetry in how the waves propagate through the device. Waves traveling in the desired direction experience constructive interference, meaning they reinforce each other and can pass through the device. On the other hand, waves traveling in the opposite direction experience destructive interference, meaning they cancel each other out and are blocked from passing through.