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| Impact Analysis of the Sub-channel Delay in Very Long Baseline Interferometry Digital Baseband Converter |
| Jiang Kun Wang Yuan-qin Ma Hong Jiao Yi-wen Lian Xin |
| Academy of Equipment, Beijing 101416, China |
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Abstract The effect of Digital BaseBand Converter (DBBC) sub-channel delay on bandwidth synthesis precision is analyzed under the condition of the consistent receiving system channel delay in order to improve the accuracy of bandwidth synthesis. Through a theoretical derivation, it is for the first time to discover that the sub-channel delay could induce “phase step” phenomenon among the different sub-channels in the group delay measurement of a single station. And in the delay difference measurement of different stations, the “phase step” phenomenon could occur when the frequency differences of different stations’ corresponding sub-channel Local Oscillator (LO) are different. The “phase step” could deteriorate the precision of bandwidth synthesis. The impact domain of the sub-channel delay is discussed for different DBBCs, suggesting that the “phase step” can be eliminated by a sub-channel delay compensation. The simulation results show that the sub-channel delay compensation can effectively remove the “phase step” and the precision of bandwidth synthesis can be improved by at least one order of magnitude or more.
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Received: 10 July 2013
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Corresponding Authors:
Jiang Kun
E-mail: jiangkunzzy@126.com
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2014, Vol. 36 
