Based on the theory and practical method of time difference system with dual mixer presented by Allan, this paper analysed emphatically an 100MHz time difference system with dual mixer which was established at Shanghai Observatory.

• 本文根据Allan提出的双混频时差(DMTD)测量系统的原理和方法,着重对上海天文台建立的100兆赫双混频时差测量系统进行了分析。