Research on a novel 2∼18 GHz PHEMT MMIC digital attenuator with low insertion phase shift

A novel ultra broadband (2 ~ 18 GHz) 6-bit monolithic microwave integrated circuit(MMIC) digital attenuator with low insertion phase shift is presented. Phase compensation techniques were used in the MMIC design to reduce the insertion phase shift when the attenuation state varies. Performance redundancy optimization strategy was used to get the best performance. This attenuator is fabricated with 0.5μm GaAs PHEMT process. On-wafer measurement results of the developed MMIC chips in the 2-18-GHz band show that the 6-bit MMIC digital attenuator has 0.5 dB resolution and 31.5 dB dynamic attenuation range, input and output VSWR<; 1.8 for all attenuation states, and attenuation accuracy: +2.31dB/-0.51dB; insertion phase shift: +6.28°/-1.53° referenced insertion loss: <;-5.71dB; the chip size is 2.89mm×1.22mm×0.1mm. To ensure high yield, Performance redundancy optimization strategy is used in design, and PCM (Process Control Map) and SPC(Statistics Process Control) technology are used in fabrication. The yield is more than 85%.