5GSPS Handheld Isolation Channel Scopemeter Hardware Design

Hand-held scopemeter is widely recognized by users for its portability and low consumption.at present,the bandwidth of domestic mainstream scopemeter product is within 200 MHz,the maximum sampling rate is 2.5GSPS,and there is less isolation design,it is difficult to meet the growing demand for measurement.therefore it is necessary to research and develop a type of scopemeter of high bandwidth,high sampling rate and high isolation.This paper firstly analyzes the overall architecture of the hand-held scopemeter.then the realization method of the isolation channel in the scopemeter is given in detail.the detailed implementation scheme of the 5GSPS sampling rate is discussd,finally,the power consumption analysis and low power design are carried out,it is discussed mainly from the following three aspects.1、Analog channel isolation.firstly there is the introduction of the specific implementation scheme of analog channel,then is the detailed elaboration of isolation design including power isolation,control signal isolation and external interface isolation,the channel isolation have been improved.the open circuit noise of the scopemeter is tested,by means of circuit optimization,shielding and absorbing wave,the open circuit noise of the scopemeter is reduced.2、5GSPS sampling rate digital acquisition system.in this design,the 5GSPS sampling rate is realized by piecing the two dual-core ADC together.The impact of the parallel sampling error on ADC’s Effective Number Of Bits is elaborated,and the gain and offset of ADC are corrected,then the amplitude frequency characteristics of sampling waveform is analyzed,also the Signal Noise Ratio of digital acquisition system is improved,finally many function module such as high speed data receiving and caching,peak detection,hardware sampling is finished in FPGA.3、Low power design.combined with the characteristics of the scopemeter,low power optimization scheme is presented: to adjust the sampling rate of ADC according to the time base dynamically,to realize the automatic adjustment of screen brightness through detection of ambient light,and to perform key detection by interrupt mode.The scopemeter researched by this paper is of 500-MHz bandwidth,5GSPSsampling rate and 60 dB channel isolation.