Design Of High-speed Data Acquisition System Based On The Principle Of Random Equivalent Sampling

It is necessary for modern digital signal processing to deal with complex signals and to represent them in different forms. Since the input signal's time-domain and frequency-domain characteristic must be analyzed, nature affords signals in other forms, a prerequisite for digital signal processing is the conversion of signals into digital form. When the frequency of the input signal is high enough, parallel processing or equivalent sampling is used. Parallel processing acquires a wider signal band at the cost of slowing down the processing speed and adding the complexity of the circuit. At the same time, the expense of the system based on parallel process technology is high, while equivalent sampling technology is economical and effective. The prerequisite of a signal which can be sampled in equivalent sampling technology is that the signal must be a periodic signal. The input signal is reconstructed with several random sampling series by multi-trigger. That is, A low-speed ADC is used to capture wide-band ,high-speed periodic signal.The characters of random equivalent sampling system lie in high frequency of the input signal and the complex configuration of logic circuit. When the sampling band is constant, random equivalent sampling can ruduce the cost greatly, which is the merit of the system. The random sampling system introduced in this thesis can sample signals with frequency below lMhz in real-time and signals with frequency above lMhz in equivalent sampling. Some important techniques in system design are given in this thesis:(l) The double slope charge-decharge circuit which is the key of a random sampling system is designed , simulated and adjusted.(2)The design of the input attenuation-amplifier circuit under the control of encode switch is given.(3)The circuits revelent to data acquisition system such as trigger circuit,the circuit of short time generator in random sampling etc,are designed, simulated and adjusted.(4)The design of software revelent to data acquisition system such as real-time data acquirsition and random sampling arithmetic is given.(5)The design of PCB and the technology and experience in circuit adjustment are shown at last.