水下一發一收換能器系統之匹配研究

水下一發一收系統係以發射與接收換能器組成，主要流程為發射換能器發射能量，此能量在水中因為距離以及懸浮微粒產生衰減後，由接收換能器接收，再透過壓電效應轉換成電訊號輸出，可運用在泥沙濃度、水下無線充電、魚群探測等用途上，然而不同的發射器與接收器在等效電路參數變化之下，會讓最佳發射頻率與最佳接收頻率改變而造成理想驅動頻率飄移，若換能器在非理想狀態下運作，除了短期會造成系統損失效率以及換能器發熱之外，長期下來可能會造成換能器損壞，另一方面來說，水下環境會因為四季變化、天氣影響而產生溫度、壓力、水流等變動，這些變動都有可能會干擾能量傳輸，為了改善上述缺點，本文針對一發一收機制，發展了一套掃頻系統，以直接數字合成(DDS)作為掃頻訊號核心，以AD8310作為接收電路核心，透過ARM控制器操作整體系統運作，本研究之動態追蹤法能根據換能器不同配置下，動態設定最適合該配置的驅動頻率，此外也能偵測理想驅動頻率建立回朔數據，提供對於環境是否有在變動的判別依據。在一發一收應用中，泥沙濃度原理為發射訊號穿透待測液後，該訊號與待測液中的粒子碰撞而受到幾何、介質、散射衰減，此衰減關係與待測液體濃度成正向關係，藉此能推算出濃度，而為了使系統有更廣的頻寬以因應不同場合的應用，本文使用電感匹配使整體頻率響應拓寬，再利用拓寬後的頻段內選擇三個相同接收強度、不同頻率點量測濃度，最後探討了使用不同頻率量測濃度的結果。

關鍵字

換能器；電感匹配； DDS ；泥沙濃度；超音波

並列摘要

Transceiver system has many applications such as Sediment Concentration System, Wireless Charging System and Fish Detecting System. However, the environment variation under these usages include temperature and pressure which would remodel equivalent circuit and drift the ideal driving frequency. This drawback not only causes efficiency loss in short term, but also highly possible damages the transducer in long term. Therefore, this research creates a sweep circuit system to adjust driving frequency at ideal point under unstable environment. The core of the system is using DDS as transmitting circuit and use ARM as microcontroller. The experiment shows the system can track ideal driving frequency under temperature, pressure variation, and the efficiency can increase 6%~25% after tracking. The principal of Sediment Concentration System depends on the attenuation of receiving power which is proportional to concentration. Based on the frequency power law, different frequency will affect the degree of attenuation. In transceiver system, the frequency response is located near the mid-band frequency which can only be driven at specific region. In order to improve the frequency response, this research use inductance matching to expand the bandwidth, and then measure the concentration via different frequency.

並列關鍵字

Resonant Tracking System ； DDS ； Sediment Concentration System

參考文獻

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[9] 張宥駿, “超音波都卜勒流速量測系統硬體與泥沙濃度量測系統,” 臺灣大學工程科學及海洋工程學研究所學位論文, pp. 1-117, 2014.

[13] 連振傑, “具頻率校正功能之超音波換能器驅動電路設計,” 臺灣大學電子工程學研究所學位論文, pp. 1-67, 2012.

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[1] R. Urick, “The absorption of sound in suspensions of irregular particles,” The Journal of the acoustical society of America, vol. 20, no. 3, pp. 283-289, 1948.

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水下一發一收換能器系統之匹配研究

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