An X-Band Active Digital Step Attenuator With Complementary Phase Variation Compensation

An X-band active digital step attenuator (DSA) with a novel phase error minimization technique for phased-array applications is presented in this brief. Based on the analysis of the phase variation characteristic during gain tuning in the conventional current-steering variable gain amplifier (VGA), an inductive phase compensation unit with an opposite insertion phase response is developed herein, achieving an effective phase error reduction. The proposed active DSA is fabricated in SMIC 40-nm CMOS process, occupying a core area of 0.27 mm2. The measurement results exhibit an attenuation tuning range of 20 dB with 0.5 dB steps, while the root-mean-square (rms) gain error and rms phase error within 8–12 GHz are better than 0.34 dB and 1.85°, respectively. At the minimum attenuation state, the peak gain is −1.3 dB and the gain variation is less than 0.3 dB. In addition, the input 1 dB compression point (IP1dB) varies from 2.4 to 3.1 dBm while the power consumption is 13.6 mW.