We present a new explicit construction of onesided bipartite lossless expanders of constant degree, with arbitrary constant ratio between the sizes of the two vertex sets. Our construction is simpler to state and analyze than the prior construction of Capalbo, Reingold, Vadhan, and Wigderson (2002). We construct our lossless expanders by imposing the structure of a constant-sized lossless expander "gadget" within the neighborhoods of a large bipartite spectral expander; similar constructions were previously used to obtain the weaker notion of unique-neighbor expansion. Our analysis simply consists of elementary counting arguments and an application of the expander mixing lemma.

翻译：我们提出了一种新的显式构造方法，用于构建具有恒定度数的单侧二分无损扩展图，其中两个顶点集的大小之比可为任意常数。与Capalbo、Reingold、Vadhan和Wigderson（2002）先前的构造相比，我们的构造更易于陈述和分析。我们通过在一个大型二分谱扩展图的邻域内嵌入恒定大小的无损扩展图“组件”结构来构建无损扩展图；类似构造此前曾被用于获得更弱的唯一邻居扩展概念。我们的分析仅包含基础计数论证及扩展引理（expander mixing lemma）的应用。