X-band Phase Shift Monolithic Six-digit Attenuator Study

This paper mainly introduces the circuit design, layout design and simulationresult of X band MMIC 6-bit digital attenuator with low inserted phase shift,operating at 8.5-10.5GHz.Firstly, the theories of basic GaAs digital attenuator MMIC's configurations areresearched. Secondly, every possible configuration is contrasted by the author,subsequently, the appropriate topology is selected for each stage and the initial valuesof the resistors are calculated for different attenuation. Thirdly, by means ofADS2004A in designing stage, author chooses optimized function and sets theoptimized goals for attenuation accuracy, insertion loss and VSWR. Input and outputports all match to 50Ω. After each stage achieves high precision and low insertedphase shift as small-scale as possible, each attenuation bits cascades of six-stagecircuits and go into layout design stage.Finally, the X band MMIC digital attenuator achieves 0.5 dB LSB steps to 31.5dB, a high attenuation accuracy of±0.2 dB, insertion loss less than 4.5 dB, insertedphase shift less than 20°and VSWR less than 1.4 over the 8.5-10.5 GHz, die size only1.55mm×1.20mm×0.1mm. It accords with the performance index.