CAJ | 학술논문

VLBI数据采集终端是VLBI台站的重要设备,近年来随着数字硬件设备例如ADC、DSP、FPGA的快速发展,数字基带转化器代替模拟基带转换器成为现实.现有采用多相滤波器实现DBBC的方法不可避免存在盲区,且频率、带宽均不可调.提出一种通用的基于多相结构的宽带数字下变频方法,将多速率信号处理和并行处理方法应用在其中,成功实现了VLBI多个通道的单边带数字基带转换,且能实现中频中心频率可调、带宽可选.硬件测试结果表明VLBI数字基带转换器频率设置正确,带宽选择正确,且数字基带转换器带通特性好于模拟基带转换器.
VLBI수거채집종단시VLBI태참적중요설비,근년래수착수자경건설비례여ADC、DSP、FPGA적쾌속발전,수자기대전화기대체모의기대전환기성위현실.현유채용다상려파기실현DBBC적방법불가피면존재맹구,차빈솔、대관균불가조.제출일충통용적기우다상결구적관대수자하변빈방법,장다속솔신호처리화병행처리방법응용재기중,성공실현료VLBI다개통도적단변대수자기대전환,차능실현중빈중심빈솔가조、대관가선.경건측시결과표명VLBI수자기대전환기빈솔설치정학,대관선택정학,차수자기대전환기대통특성호우모의기대전환기.
The VLBI (Very Long Baseline Interferometry) data acquisition backend plays an important role in the VLBI station. Recently, based on advances in digital hardware like ADC(Analog-to-Digital Conversion), DSP (Digital Signal Processing), FPGA (Field Programmable Gate Arrays) and so on,it has become practical to sample and digitally process the intermediate frequency signal directly.DBBC(Digital Base-Band Converters) will replace ABBC(Analog Base Band Converters) in the VLBI data acquisi-tion backend.A VLBI digital backend using poly phase filter banks exits blind frequency zone inevitably.Moreover,the frequency and the band width are not adjustable in this method.This paper analyzes this limitation and presents a sequence of simple mod-ifications to sampled data structures based on the analog prototype system to obtain the poly-phase structure in the VLBI data acquisition backend which can eliminate the blind frequency zone.The theoretical principles of digital SSB(Single Side Band) con-verters are discussed in detail.The approach adopts multi-rate signal processing for the designed filters in a digital SSBconverter which is carried out by virtex-4 FPGA chips.The result of hardware VLBI experiments indicate that it can receive random IF band-pass in and bandwidth can be selected.Meanwhile.a conclusion is reached from the experiment that the VLBI DBBC has a better band pass performance than the ABBC.