Creating PDA for {xy such that |x|=|y| and x ≠ y}

Question

I'm trying to create a PDA for $\{xy \mid |x|=|y| \text{ and } x \ne y\}$ over the alphabet $\Sigma = \{a, b\}$. But I don't know how the PDA will know if the two strings $x$ and $y$ are not equal. Please help me create this PDA step by step.