Abstract: This paper describes the design,fabrication,and testing of an MMIC digital attenuator covering the range of 50MHz～20GHz and also describes in detail how to realize an ultra-broad attenuator.This attenuator is fabricated in a 0.5μm ion-implanted process.The attenuator shows exceptional performance,with an insertion loss of reference state of less than 5dB.The input and output VSWRs are better than 15∶1 over all states and the entire frequency range.The attenuation accuracy is within ±0.3dB (the actual attenuation-the attenuation setting).The phase variation (reference to insertion state) is between -5°～20°.The 1dB compression point is 22dBm(at 10GHz).

Key words: ultra-broad band, GaAs, digital attenuator, MESFET