An expander code is a binary linear code whose parity-check matrix is the bi-adjacency matrix of a bipartite expander graph. We provide a new formula for the minimum distance of such codes. We also provide a new proof of the result that $2(1-\varepsilon) \gamma n$ is a lower bound of the minimum distance of the expander code given by a $(m,n,d,\gamma,1-\varepsilon)$ expander bipartite graph.

翻译：扩展码是一种二进制线性代码, 其对等检查矩阵是双边扩展图的双对称矩阵。 我们为这种代码的最小距离提供了一个新的公式。 我们还提供了一个新的证据, 证明2美元( 1-\ varepsilon)\ gamma n$ 是美元( m, n, d,\ gamma, 1-\ varepsilon) 的扩展码最小距离的下限, 由 $( m, n, d,\ gamma, 1-\ varepsilon) 的扩展双边图给出 。