The Research Of Ultra Broadband 5-Bit MMIC Digital Attenuator

With the development of communication technology,communication systems are constantly upgrading. Communication products also are developing at many directions such as miniaturization,low-power and reliability. Due to its small size, good stability, capability, consistency and cheap in mass yield, Monolithic Microwave Integrated Circuit (MMIC) is becoming more and more important in the communication market. As the key component of system, attenuators are widely used in broadband communications, microwave radio communications, military radar, space communications and other electronic equipments.This paper mainly introduces the circuit design, layout design, testing results and analysis of an ultra broadband MMIC 5-bit digital attenuator.Firstly, this paper describes the characteristics of MMIC technology and application. Secondly, making a presentation of the development of MMIC attenuator and its significance, then discussed several basic structures for attenuator. Subsequently, specifically this paper introduces the design of this ultra-wideband attenuator: According to the specific requirements, we choose the best structure, using MOMENTUM co-simulation for optimization to design 1dB, 2dB, 4dB, 8dB, 16dB attenuation bit, and then achieve the desired attenuator by running simulation and optimization of the whole cascade circuit. Since the circuit has been taped-out and testing on board, finally we make a comprehensive analysis of the results and a discussion of the significance and shortcomings of our work.In the design, Advanced Design System 2006(ADS2006) is used as the EDA tool. Finally, the 5-bit digital attenuator was taped out with 0.25um pHEMT process. It has a good performance and operates at 5GHz-38GHz, has 31 dB dynamic range stepped by 1 dB; reference insertion loss:<7 dB; attenuation increments are 1.0±0.4 dB; input and output return loss:>12 dB. The chip size is only 2.4mm×1.2mm×0.1mm. As far as I know, the bandwidth of the attenuator is the broadest one yet reported in domestic literatures. It can be used for military electronic counter measures and civilian communications.