The High-Speed Signal Acquisition Based On The Equivalent Sampling Technology

In the fields of modern electronic measurement, communication systems, radar and electronic countermeasures etc, it is very often to sample and storage to the broadband analog signal, for data processing in the computer. According to Nyquist sampling theorem, in order to acquisition high-speed analog signals without distortion, the sampling frequency must more than two times than the input signal. That is, high-speed sampling techniques must be used to achieve the above purpose, and it also made high demands to the speed of the device, the structure of the circuit and the debugging of the system, thus increased the difficulty of achieving the system in a large degree. 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 sampling series by multi-trigger. It is easy to acquire high-speed broadband analog signal use a low conversion rate A/D converter based on the equivalent sampling, which not only reduces the difficulty of achieving the system, but also saving the cost of the system.This paper introduced the principle of high-speed data acquisition based on the equivalent time sampling, especially the application of ordinal sampling in the equivalent time sampling technology. It designed a circuit scheme of margin sampling, finished the circuit design and simulated to the main circuit. In this scheme, the margin sampling circuit uses difference output structure which reduced the interference of the common-mode noise in a large degree. The circuit used the closed-loop structure, enhanced the stability of the system. Furthermore, designed a kind of precision delay circuit use the complex programmable logic device (CPLD) and digitally programmable delayer (AD9501). It has high precision and easy to be controlled.