X-band High-precision Monolithic Five-digit Attenuator

This paper mainly introduces the circuit design, layout design and simulation results of X band MMIC 5-bit digital attenuator with high precision, operating at 7GHz -11GHz.Firstly, the theories of basic GaAs digital attenuator MMIC's configurations are researched. Secondly, every possible configuration is contrasted by the author, subsequently, the appropriate topology is selected for each stage and the initial values of the resistors are calculated for different attenuation. Thirdly, by means of ADS2005A in designing stage, author chooses optimized function and sets the optimized goals for attenuation accuracy, insertion loss and VSWR. Input and output ports all match to 50Ω. After each stage achieves high precision and low inserted phase shift as small-scale as possible, each attenuation bits cascades of five-stage circuits and go into layout design stage.Finally, the X band MMIC digital attenuator achieves 0.75dB LSB steps to 23dB, a high attenuation accuracy of±0.2dB, insertion loss less than 4dB, inserted phase shift less than 20°over the 7GHz -11GHz, die size only 1.39mm×0.95mm.It accords with the performance index.