DDS（直接數字頻率合成）技術是一門在頻率合成領域的新興技術，具有響應時間短，
精度高等優點。而PLL（Phase Locked Loop）鎖相環技術雖然工作速度慢，但穩定可靠。VXI 總線具有靈活、體積小、可移植好等特點，VXI 總線測試平臺是21 世紀公認的儀器總線系統和自動測試系統的優秀平臺。VXI 總線模塊儀器的優點是宜于集成為不同用途的自動測試系統，具有優良的交互操作性，數據傳輸速率高，可靠性高，易維修，體積小，重量輕，功耗低，可移動性好，價格與傳統的自動測試系統相比具有巨大的競爭潛力。
關鍵詞：VXI 總線；DDS；PLL；精密時鐘

Abstract： DDS is a new technique in the field of frequency synthesis. It owns the merits of
shorter response time, high accuracy, and so on. Though the converting speed of PLL is low, it works very stable. VXI bus owns the merits of smaller dimension, better transplanting ability, and so on. It is excellent instrument platform in 21st century, it has shown huge power of market competition with the merits of lower consumption, very good instinct of movable and its price compared with traditional instruments.
Keywords：VXI bus；DDS；PLL；PRECISE CLOCK