Abstract: The equivalent circuit model of planar grid is obtained based on the analysis of quasioptical grid arrays using EMF method. The complete transmission line circuit model of the planar grid oscillator arrays is analyzed using the equivalent circuit model of the active device. The loop-gain is obtained by node-analysis method. A developed software is on the platform of Windows 95. for designing planar grid oscillator arrays. The results come out to be a good agreement with theoretical analysis and reports from home and foreign documents.