Wideband active bi-directional SiGe digital step attenuator using an active DPDT switch

A 6-bit active bi-directional silicon-germanium (SiGe) digital step attenuator (DSA) with multi-octave bandwidth using an active double-pole double-throw (DPDT) switch is demonstrated. To compensate the insertion loss (IL) and frequency dependent loss characteristics of conventional passive attenuators without using any additional amplifier and equalizer, the proposed attenuator employs active DPDT switches, which provide 4-way switching and bi-directional operation. The measured gain is 7.0-9.6 dB and the input and output return loss is better than 9 dB for 2-20 GHz. The measured root mean square (RMS) amplitude and phase errors in the major state are less than 0.4 dB and 3.0 degree, respectively. The chip size is 1.43 × 1.23 mm², including pads. The proposed active bi-directional DSA consumes 30 mA from a 2.5 V supply.