Study On Broad Band Time Domain Acquisition System

With the continuous development of the electronics and information technology,the frequency of system clock has multiplied, the timing margin has decreased sharply,and the instantaneous signal and abnormal phenomenon has become prominent; the signal bandwidth increases very rapidly.The complication of the signal presents time domain test equipment represented by digital oscilloscope a new challenge,sufficient high performance of signal real-time acquisition and the capability of broad band sampling,will be the two development orientation of the broad band time domain acquisition system.However,due to the restriction of the device and the manufacturing level,etc, under the condition of existing hardware,how to maximize the singal real time capture capability and improve the real time sampling rate as much as possible without distortion, is a major problem encountered in the research filed of broad band time domain acquisition system.This paper combines the tasks of military electronic equipment and civilian cooperation projects undertaken during the PhD research,and in view of the technology implementation of the high performance test equipment such as digital 3D oscilloscope,broad band parallel acquisizion DSO,etc, does some research on the following aspects in depth:1. Method to improve the signal real-time capture capability----technology of digital 3D mapping.The basic model of digital 3D mapping is found and varieties of factors influencing the efficiency of digital 3D mapping are analyzed deeply,as a result, the improved mapping array models are arrived,and calculating formulas of the oscilloscope waveform capture rate for the different mathematical model are put forward,respectively.For two differernt mapping models, based on 1GSPS acquisition system of 2 channel,the corresponding waveform mapping systems of the digital 3D oscilloscope are designed and implemented.2. Method to test the waveform capture rate of the digital 3D oscilloscope.The relationship between the waveform capture rate and the "dead time" is researched, and a method to test and measure the oscilloscope's waveform capture rate with the external characteristic is discussed.Through this method,user or the third party can test any oscilloscope and obtain the actual waveform capture rate accurately.Meanwhile,the method, as well as the calculating formula of waveform capture rate mentioned above in 1),is used to test and measure digital 3D oscilloscope designed and implemented in 1),validating the mapping model and the calculating formula of the mapping efficiency.3. Method to calibrate the amplitude error of the parallel acquisition system.The reason of the channel mismatch error in parallel time-interleaved acquisition system is discussed, and from the perspective of the acquisition model, a method,which can estimate and calibrate the amplitude mismatch error synthetically,and solve the problem of offset and gain errors simultaneously through a calibration, is researched.4. Nonuniform signal reconstruction.The nonuniform problem of the signal brought about by timing mismatch error in the parallel time-interleaved acquisition system is analyzed,and the viable scheme of adaptive reconstruction under the condition of nonuniformity is introduced,which can avoid the bandwidth loss result from the former waveform reconstruction means;the spectrum continuation is reduced by using window function;the resource consumption and efficiency of the waveform reconstruction technology with nonuniformity and the waveform reconstruction arithmetic after the nonuniform calibration is analyzed, and the integration signal reconstruction method of nonuniform system is exposed to optimize the arithmetic efficiency.5. Compensation for channel frequency response.The bandwidth characteristic of DSO is analyzed and researched.The method to test the actual channel frequency response of the system is present, which establishes a base of the design of filter compensating for channel frequency respone from the perspective of digital signal processing, meanwhile,the best degree of the signal recovery can be obtained by using the Bassel amplitude-frequency response and linear phase to do furture optimization and restriction.