Upper critical field of complex superconducting networks in the continuum limit

We propose a simple method for calculating the superconducting upper-critical field of complex periodic two-dimensional networks in the continuum limit. Two specific lattices with space groups $P4\mathrm{gm}$ and $C2\mathrm{mm}$ are used to demonstrate this approach. We obtain the result that the ratio of the critical field of these networks to that of a uniform film is close to but larger than 2.