This paper presents a compact-size tunable gainequalizer for X-Band Phased-Array RADAR applications in a 0.25µm SiGe BiCMOS technology. An isolated NMOS based variable resistance was used for the first time to tune the slope of the gain-equalizer. For NMOS, an isolated body created by a deep n-well was utilized to reduce insertion loss due to the substrate conductivity. Furthermore, the power-handling capability of the tunable gain-equalizer was improved thanks to the resistive bodyfloating technique. The designed tunable gain-equalizer operates in the frequency range from 8 to 12.5 GHz with a measured positive slope of 1 dB/GHz and 1 dB tunable slope. The effective chip area excluding the pads is 0.21 mm 2 , and the total area including pads is 0.31 mm 2. To authors best knowledge, this study is the first tunable gain-equalizer in SiGe technology presented for X-band phased-array RADAR applications.
In this study, the analysis, design and measured results of a fully integrated 7-Bit step attenuator implemented in a 0.25-µm Silicon-Germanium (SiGe) BiCMOS process technology, are described. The attenuator is designed based on delicately ordered and cascaded Π/T type attenuation blocks, which are comprised of series/shunt switches employing SiGe hetero-junction bipolar transistors (HBTs) with peak fT /fmax of 110/180 GHz. HBTs are employed as a series switch to decrease the insertion-loss of the attenuator. Moreover, to authors' best knowledge, this is the first study presenting the effect of employing reverse-saturated HBTs as a shunt switch for each attenuation blocks. Thanks to this advancement, the highest input-referred 1-dB compression point (IP 1dB ) is reported for Si-based similar studies. This method also decreases the insertion-loss of the proposed attenuator. The measurements result in the state-ofthe-art performance with 28.575 dB attenuation range by 0.225 dB gain steps while maintaining 7-bit amplitude resolution across 6.6 GHz to 12.8 GHz frequency band, where RMS phase error remains below 3.3 • and insertion loss (IL) is less than 12.4 dB. The measured IP 1dB of the attenuator is 13.5 dBm while drawing 8 mA from 3.3 V supply. The die occupies an area of 1.37 mm x 0.56 mm excluding pads.
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