3.5-ghz-band Low-bias-current Operation 0/20-db Step Linearized Attenuators Using Gaas-hbt Compatible, Ac-coupled, Stack Type Base-collector Diode Switch Topology

摘要

This paper describes two different types of GaAs-HBT compatible, base-collector diode 0/20-dB step attenuators - diode-linearizer type and harmonics-trap type - for 3.5-GHz-band wireless applications. The two attenuators use an AC-coupled, stacked type diode switch topology featuring high power handling capability with low bias current operation. Compared to a conventional diode switch topology, this topology can improve the capability of more than 6 dB with the same bias current. In addition, successful incorporation of a shunt diode linearizer and second- and third-harmonic traps into the attenuators gives the IM3 distortion improvement of more than 7 dB in the high power ranging from 16 dBm to 18 dBm even in the 20-dB attenuation mode when IM3 distortion levels are basically easy to degrade. Measurement results show that both the attenuators are capable of delivering power handling capability (P_(0.2dB)) of more than 18 dBm with IM3 levels of less than -35 dBc at an 18-dBm input power while drawing low bias currents of 3.8 mA and 6.8 mA in the thru and attenuation modes from 0/5-V complementary supplies. Measured insertion losses of the linearizer-type and harmonics-trap type attenuators in the thru mode are as low as 1.4dB and 2.5 dB, respectively.