In this paper, a digital step X-type attenuator with low process variations is demonstrated using 90 nm CMOS technology. The X-type attenuator uses MOSFETs as voltage controlled resistors, which influenced by process parameters. And a compensation circuit associated with the threshold voltage is employed to mitigate the process influence. The attenuator have a maximum attenuation range of 32 dB with 0.5 dB steps. The rms amplitude error and rms phase error are 0.42 dB and 3.1° over 23.5–30 GHz respectively, and the insertion losse is 9.77 dB at 25 GHz. The core chip size is 0.48 mm2.
2017 by The Institute of Electronics, Information and Communication Engineers