Embedded Digital Lock-in Amplifier Based On TMS320C6701EVM

The theory of weak signal detect is the key technology in signal detect field, which is an integrated technology based on electronics,information theory,physics and computer science. The parameter estimation of sine-wave flooded in strong noise background is an important and practical technique, and it is the base theory of spectrum analysis estimation. Weak sine-wave signal detect is widely applied in physics,chemistry,optics,biophysics,astronomy,geognosy physic and so on. Lock-in amplifier is a very efficient detect instrument used to recover weak signal from strong noise. The theory of detection bases on synchronous correlation technology for the un-correlation character between the period signal and the random noise. Since 1962, the first lock-in amplifier was produced in America, which was successfully used to detect the Auger's energy in strong electrons background. Many types of lock-in amplifiers were produced all over the world and played an important role in science research and social production. Especially, American EG&G Company (the primary Stanford Research System) is in the lead in lock-in amplifiers'study, and have produced series of analog and digital lock-in amplifiers (DLIA). In our country, although few institutes have taken part in study in it, there are no commercial instruments being developed. So developing digital lock-in amplifier with own intelligence potency and fitting for native condition is very important and will bring great social economic benefit. Based on analog circuit, the analog lock-in amplifier has a lot of shortcomings, for example: hard to synchronize, short integral time, and so on. While DLIA can easily overcome those shortcomings, with the technology of the microelectronics and digital signal processing (DSP). Besides, DLIA that based on DSP is flexible in function and has powerful signal processing ability because of programmable digital technique. TMS320C6701 is a type of high performance floating digital signal processor of TI Corp., which has eight parallel function units, advance Harvard architecture, several level pipelines, and peak speed up to 1 GFLOPS. The DLIA based on TMS320C6701 provides powerful processing capacity,high data throughput and real time response. This paper summarizes the theory of parameter estimation and the method of sine-wave signal estimation which is flooded in white-noise background. Basing on analog lock-in amplifier structure and function, the paper also gives the mathematic model of DLIA. At the same time, some factors which may directly affect the lock-in performance of DLIA are analyzed in detail, included: integral time constant, the frequency difference of DLIA system, the choice of sample frequency, the system dynamic range and the date type of digital...