Design And Implementation Of The Equivalent Sampling System Of Sampling Oscilloscope

Since the rapid development of electronic science and technology, the complexity and diversity of the characteristics of electronic signal transmission becomes more obvious, and thus these signals are increasingly demanding measurement conditions. As a measure instrument of the high-speed signals, sampling oscilloscope, which adopts its unique sampling structure and the principle of equivalent sampling, can reach ten times sampling rate and system bandwidth more than the real time oscilloscope.In this dissertation, the design of sampling oscilloscope is based on characteristic impedance analyzer platform which uses the same principle of equivalent sampling. Due to the existing platform can not conduct a multi-channel measurement, therefore multi-channel acquisition circuit and a differential processing circuit should be redesigned, and designed a differential processing circuit and filter circuit. Since there is not a gignal filtering circuit on the existing circuit, it is necessary to increase a filter ciucuit. In order to increase the two functions of offset process and gain process, bias ciucuit and gain circuit performed by DACs which are controlled by FPGA are designed. Meanwhile, the system clock circuit is redesigned to get a more stable clock signal. On this basis, the control code of FPGA is programed to realize the sequential equivalent sampling based on the theory of "coarse delay + fine delay", the average measurement function, multi-channel measurements, differential measure ment, adjustable bias function and variable gain function.The final design of the sampling oscilloscope sampling system can achieve the equivalent sequential equivalent-time sampling. In the test, the signal-to-noise rate reaches 64.68 d B, at the condition of using 100 GSPS equivalent sampling rate to sample a 100 MHz sine waveform, this means that high-speed sampling of the signal is achieved. In the Dual-channel test, data conformance is improved; the newly added average measurement funciton, multi-channel measurement, differential measurement, adjustable bias function and variable gain function has also been achieved. O n the test of the acquisition of AD9251 for 100 KHz, 400 millivolt peak-to-peak value sine wave signal signal input, the Signal Noise Ratio reaches 70.16 d B, and total harmonic distortion is-74 d B, this means the ability of data acquisition is better than before. The current design of the hardware platform of the equivalent sampling system and procedure have been applied in the latest instrument.