6-bit Step Attenuators for Phased-Array System With Temperature Compensation Technique

This letter presents 6-bit differential step attenuators on SiGe BiCMOS for K- and Ka-bands with temperature compensation technique. A temperature-variant voltage source (TVVS) is applied to source and drain terminals of the switch MOSFETs. on-state resistance of MOSFETs, therefore, remains stable with temperature variation. With this technique, the root mean square (RMS) attenuation error will be stabilized under different ambient temperatures. Two attenuators for K- and Ka-bands are fabricated using 0.13-mu m IBM 8XP SiGe BiCMOS process; both attenuators have a maximum attenuation of 31.5 dB with a step of 0.5 dB. The attenuator working at 15-18 GHz exhibits a maximum RMS attenuation error of 0.3 dB from -55 degrees C to 125 degrees C, whereas the attenuator working at 19-24 GHz shows a maximum RMS attenuation error of 0.5 dB. To the authors' best knowledge, for the first time, a TVVS is added to a 6-bit differential step attenuator to achieve consistent attenuation accuracy during thermal variation.