Abstract: This study presents the temporal Coupled-Mode Theory (CMT) analysis of a K-band MMIC (Microwave Monolithic Integrated Circuit) bandpass filter with dual orthogonal resonant modes. Two test methods are applied and compared in the filter response measurement. The dimensions of the MMIC filter, whose chip size is 1.9×1.35 mm, are optimized based on the FEM (Finite Element Method) simulation assisted temporal coupled-mode theory. As a two-port reciprocal system, the transmission and reflection responses of the filter are deduced. GaAs MMIC IPD (Integrated Passive Device) technology is applied for chip fabrication. The test results using a probe station fit well with the simulation results. A testing fixture is introduced to model the practical application scenario, whose measurement results, after de-embedment, have shown consistency with the simulation and the probe station test results.