Study Of Digital_Analog Mixed-signal System

As the frequency of the digital circuits becomes higher than before, engineers are willing to digitize the analog circuits in higher frequency. Therefore the requirement of Analog and Mixed-signal design is attached much importance. Nowadays the methods of mixed-signal circuits design are classed to two ways: using simulation software such as Spice to design circuit from bottom to up, and using hardware description language to describe the circuit. There are two kinds of HDL: VHDL-AMS and Verilog-AMS. But no convenient circuit design software and compiler supports these two kinds of languages till now. So the analog design tools can be used to develop mixed-signal circuits. In this paper, a RF receiver with a filter which working frequency can be controlled is developed based on the RF circuit theory and software defined radio theory. In this design, the following circuits are designed: a RF power amplifier with the gain of 25dB a RF filter with -3dB ripple in passband and -20 dB attenuation in stopband a digital controlled 8-segment LC filter an IF amplifier with the gain of 50dB at least an 8-bit ADC ADS tool of Agilent, an Analog/RF palette, can be used to achieve the Analog and Mixed-signal design. In this design, some key points are resolved including the design of matching network of a high frequency power amplifier, the interface circuits design between analog and digital circuits, bias circuit design of IF amplifier and the ADC comparator. The design of voltage convertor, ADC and digital controlled multi-frequency filter realizes the mixed-signal concept in the RF receiver. Through the designing of RF receiver, ADS software is proved to be an available and feasible tool.