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Research on mixed signal circuit design technology

research on mixed signal circuit design technology

in view of the special requirements of the miniaturization development of aerospace electronic systems, this paper proposes to design mixed signal circuits in spaceborne electronic systems, focuses on the problems faced by the mixed signal circuit design technology and its countermeasures, and takes the downlink channel design of spaceborne computers as an example, The mixed signal design of Aerospace Microelectronic system is preliminarily explored

key words: system level chip; Mixed signal; Design process; IP core


the demand of the aerospace market has driven the development of satellite technology. The research on micro, nano and even skin satellites has become a hot spot in aerospace technology research. The development of microelectronic technology, system integration technology, micro electro mechanical technology, micro assembly technology and light structural materials technology makes it possible to further miniaturize satellites. From the aspect of on-board electronic system, the integrated design of on-board microelectronics can technically better meet the current and long-term satellite application needs, and can meet the requirements of more economical, faster and better projects in terms of implementation. In this case, it is very necessary to study the mixed signal circuit design technology

research difficulties and key technologies of mixed signal circuit design

in mixed signal circuit design, the problems that need to be specially considered include analog signal circuit design, mixing mode, constraint management, design reuse, mixed simulation and verification, etc. the design process of mixed signal circuit can be determined on the basis of these problems

analog signal circuit design

compared with the design of digital circuit, analog signal design is very complex. It can only be described by voltage and current, which change with time under the influence of load conditions. The final success of analog signal circuit design largely depends on the designer's experience, inspiration, care and patience. Ignoring subtle practical factors (such as component parameter deviation, distribution parameters), wiring disorder and so on may lead to correct design but unable to work normally. Therefore, the design difficulty of analog signal circuit is the first problem to be solved in the design of mixed signal circuit

through the analysis of digital logic circuit design, people try to start from two aspects: programmable simulation and EDA tools: in programmable simulation, lattice company started earlier and made remarkable achievements. They are very confident that the PPAC series they launched allows designers to configure analog filters on the spot with on-chip amplifiers and passive devices; EDA companies are also trying to find the best algorithm for analog and mixed signal design, simulation and synthesis. Therefore, the mixed signal design is no longer just a piece of paper. In the near future, it can be described by using mixed signal description language, simulated and synthesized by using EDA tools, verified by using programmable devices, and so on, just like designing digital circuits

mixed mode

it is very important to choose a mixed mode for mixed signal design. It is related to the realizability of the design, the boundary of mixed signals between various cores and the selection of EDA tools. At present, the mixing mode of mixed signal circuit is extremely complex. People can use the mode of mixing behavior level digital signal and transistor level analog signal, or the mode of mixing digital rotary encoder driven by HDL language with one reference signal per revolution and analog signal driven by logic schematic diagram. This requires EDA tools to provide an open simulation environment. At present, there are not many EDA tools that can provide this open simulation environment. Therefore, the choice of hybrid mode is particularly important

constraint management

the commonly used constraints are physical property constraints and electrical property constraints. Because mixed signal circuit design uses different levels of abstraction and different modules in different design stages, the setting and management of various constraints is very critical to the continuity of the whole design process. The constraint management system must meet the following characteristics: it must manage different types of constraints in a unified format; Constraint performance must be verifiable and evaluable, which means that analysis and verification tools must be able to achieve verification accuracy; Various constraint strips must be provided to facilitate the mutual transformation between plastic materials and their finished products, including the mutual mapping from analog to digital and digital to analog, and the cross coupling limitation can be generated through noise constraints; It must be able to verify the validity of constraints and the consistency of executable specifications, and avoid unreasonable constraints as early as possible

design reuse

using design reuse technology and IP core reuse technology can reduce design difficulty and improve design efficiency. The purpose of design reuse is to establish a software and hardware module resource library containing different design levels (such as physical layer and system layer). When the physical layer description is modified, the system layer description is still valid. In addition, when selecting an IP core, attention must be paid to the compatibility of its functional indicators, interfaces, IP core processes and electrical parameters. At the same time, the development cost and product cost should be minimized. After the IP core is developed and selected, the system simulation and modification must be repeated before the mixed signal circuit architecture can be determined

hybrid simulation and verification

in previous designs, hybrid simulation and verification were started relatively late. During simulation and verification, not only the analog part and the digital part were separated, but also each design module was separated. This method is not only lack of systematization, but also will affect the final time to market of the product. Digital circuit designers who use HDL simulators are facing the growth of analog circuit behavior but suffer from the lack of model and simulation accuracy; While analog engineers using spice or fastspice are faced with the increase of digital complexity and scale, they suffer from the slow speed of only one control mode. Therefore, EDA simulation tools that can support ms-hdl language and unified D/a interface become necessary for designers. Mentor graphics' ADMS software has become a leader in mixed signal verification solutions

mixed signal circuit design process

through the discussion on the difficulties and key technologies of mixed signal circuit design, the developed design process is shown in Figure 1. It takes system level design, circuit level design, IP integration, physical implementation and final verification as the main line. At the same time, many factors such as design for testability, reliability analysis, power consumption analysis and so on should be considered in almost every link and physical verification should be carried out at the same time, Form a spiral process

the research and development of mixed signal circuits should first start from the needs of the market, select a research and development goal, and then determine the system definition and system indicators of mixed signal circuits. On this basis, develop and select appropriate algorithms, and carry out reasonable algorithm division. After the algorithm is determined, the system engineer maps it to a specific structure to facilitate the line design and overall verification of each module

mixed signal circuit design case analysis

the downlink channel of the satellite computer is shown in Figure 2. The downlink channel processing module performs parallel serial conversion, randomization (bypassable), frame synchronization flag and convolutional coding (bypassable) on the telemetry data sent by MPU, outputs the telemetry output code stream that meets the telemetry standard, and finally performs subcarrier modulation. By inputting clock pulses of different frequencies, code streams of different rates can be output. The randomization circuit and convolutional encoder can be removed or bypassed. The remaining circuits are mainly series parallel conversion module and DPSK modulation module, which can still complete the task of conventional telemetry downlink processing. The composition of the module includes not only the digital signal circuit (parallel serial conversion and time sequence control circuit), but also the analog signal circuit (filtering and carrier modulation circuit). Therefore, the research on the mixed signal circuit design of the module is representative

in the design of this module and the interface circuit with MPU module, the adaptability to telemetry tasks under different environments and requirements should be fully considered, and the hybrid design should be carried out to make it more flexible. The digital part adopts 16 bit parallel serial conversion module to convert the data on the bus into the control pulse of the analog switch according to the corresponding clock. The analog part converts the synchronous clock pulse into the sine wave of corresponding period through the second-order infinite gain multi-channel feedback bandpass filter. One circuit is directly connected to the analog switch, and the other circuit is connected to the analog switch through the inverter. The completion of the whole function requires accurate clock frequency division circuit and fine-tuning circuit

first, parallel serial conversion and clock control circuits can be designed through digital programmable logic devices (such as CPLD of Altera company), and band-pass filtering and phase inversion circuits can be designed with analog programmable devices (such as ispPAC device of lattice company). According to the mixed signal circuit design process, the whole circuit is described in Verilog AMS language, and the Da_ IC software is used for circuit module design, ADMS tool is used for mixed signal simulation, and then it is transformed into the corresponding CMOS circuit. Various parameter analysis and power consumption optimization are carried out to meet the later design requirements, and finally the circuit table required by the process manufacturer is generated


miniaturization, structural integration, intelligent interface, system integration, low power consumption and high performance are the common goals of commercial and military circuit systems, which also drive circuit design engineers to study solutions for integrated mixed signals. With the emergence of ms-hdl and other languages, as well as the introduction of mixed signal simulation software by major EDA companies, mixed signal design is bound to develop rapidly


1 kundert K. design of mixed signal systems-on-a-chip IEEE Trans. On Computed-Aided Design of Integrate Circuits and Systems, 2000,19(12)

2 Gen Chen . Speed up Mixed-Signal IC Design by using ADMS. Mingdao communication, 2004,2

3 Gao Tai, zhouzucheng. Hybrid SoC design. Semiconductor technology, 2002,2

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