A Design of Ultra-Wide Band Six-Bit Digital Attenuator with Low Phase Shift

In this paper, an ultra-wideband six-bit digital attenuator operating at frequencies ranging from DC to 40 GHz was designed and implemented in 0.15 µm GaAs pHEMT process. The control level of This six-bit attenuator is 0/-5 V, and achieves a step attenuation of 0.5 dB and a dynamic attenuation range of 31.5 dB. The attenuator circuit is composed of six basic attenuation units cascaded. In the design of large attenuation bit, a simple T -type structure which is opposite to the phase change trend of the original structure is added, so that the full state attenuation phase variation can be less than ±8.4°, which solves the problem of large additional phase shift in the high frequency part of UWB, the insertion loss is less than 5.5 dB, the root-mean-square of attenuation error from DC to 35 GHz is less than 1.6 dB. The chip size is 2.4 mmx0.7mmx0.1 mm.