摘要： In the microwave system, the performance of the up-converter and the down-converter play a key role in the whole system. The theory and design of the X-band up-down frequency converter are researched in this thesis. The major job in this thesis is to design and manufacture a microwave up-convert system and a down-convert system to realize the frequency conversion performance. The up-convert system can convert the signal from the UHF-band to the X-band, and then the output power up to 20 watts. In the same way, the down-convert system can convert the signal from the X-band to the UHF-band. According to the technical requirements, we do the schematic design, the feasibility analysis and the unit circuit’s index estimation respectively, and achieve the circuit design by using a variety of computer-aided software. Finally we have completed the assembly, debugging and testing of the systems. All above achieve the purpose that the theoretical research and engineering application are combined by each other. The kinds Of unit circuit used in the microwave conversion components include the filter, frequency conversion and amplification circuit (the selected MMIC of amplifier, mixer, switch), power circuit and digital logic circuit. The measurement results of the Frequency-conversion front-end TR module have a good agreement with the simulation results. The up-converter system achieved output power better than 43dBm and spurs rejection better than 50dBc. The down-convert system achieved noise figure less than 3dB noise figure and conversion gain bigger than 55dB.