China Electronics Technology Group Corporation No.58 Research Institute
Abstract： In order to meet the high-precision design requirements of broadband microwave wireless communication systems, a five-bit digital controlled attenuator with low additional phase shift in the 12~30 GHz range was designed using GaAs 0.15 μm PHEMT technology in this paper. This attenuator can achieve an attenuation range of 0 dB to 15.5 dB with a minimum step of 0.5 dB by cascading five different attenuation bits. Among them, the 0.5 dB attenuation bit adopts a simplified T-type attenuation structure, while the 1 dB, 2 dB, 4 dB and 8 dB attenuation bits adopt a Lange coupler-based reflective structure. In the reflective attenuator structure, the stacked switch transistor technology and capacitor compensation technology are adopted to effectively reduce the additional phase shift within the ultra-wide frequency band and improve the attenuation percosopn. Electromagnetic simulation shows that within the 12~30GHz frequency band, the insertion loss of the reference state is less than 3.8 dB, the root mean square (RMS) error of the 32-state attenuation of the attenuator is less than 0.5 dB, its typical value is only 0.3 dB, the additional phase shift of the 32-state attenuator is less than ±3°, and the input and output return losses at the ports are both greater than 12 dB. The circuit size is only 2.95 mm×1.2 mm.
Key words : high precision；low additional phase shift；digital controlled attenuator；GaAs；reflective structure；stacked switch transistor；capacitor compensation；root mean square error
