The letter presents a high dB-linear attenuator based on variable gain amplifier (VGA) for ultra-wideband phased array systems. An effective dB-linear compensation structure is proposed to improve the gain range and accuracy. The bandwidth and gain flatness of the proposed VGA are increased by the emitter resistor-capacitor negative feedback and transistor segmentation technique. The proposed VGA is implemented with the 0.18 μm SiGe bipolar complementary metal oxide semiconductor (BiCMOS) process. The measured results show that the VGA can operate from 6 to 18 GHz with a controlled variable gain range of 20 dB, the root-mean-square gain error is less than 0.55 dB. The input 1 dB compression point (IP1dB) of the fabricated VGA is more than À5 dBm. The proposed VGA consumes 71 mW and occupies a chip area of 0.98 mm  0.98 mm.

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