Abstract: This paper gives the particular description of a theoretical analysis and practical design for high IF frequency millimeter-wave subharmonic mixer with three one-dimensional photonic bandgap (PBG) cells. Base on computer aided design, a Ka-band 4th harmonic mixer has been designed and tested. When IF frequency is 3 GHz, and RF frequency varied from 34~35.8 GHz, the conversion loss is less than 14.5 dB and the least is 11 dB. The results of simulation and test show that the formulas are correct and the scheme is practicable.