本論文利用AT41486雙極接面型電晶體(Bipolar Junction Transistor, BJT)實作一可產生混沌訊號的考畢子(Colpitts)
振盪器，其有效頻寬可達微波頻段(microwave region)，空間解析度(range resolution)可達約 5cm，並可產生豐富的非線性動態，但其訊號相關性(correlation)卻有很多sidelobe，這將使得雷達偵測容易出錯，此是由於混沌訊號的頻譜不夠平坦及平滑所造成，因此在本論文中也嘗試模擬兩種方式，看是否能得到更好的混沌訊號相關性(correlation)。
一是藉由傳統濾波器的方式，模擬混沌訊號經柴比雪夫(Chebyshev)低通濾波器的結果，觀察其頻譜以及相關性曲線(correlation curve)。由於柴比雪夫(Chebyshev)濾波器在導通頻帶(pass band)
有等效漣波(equal ripple)存在，因此仍無法完全消除相關性曲線
的sidelobe。
另一種方式則是模擬光電回授複合系統(optoelectronic feedback hybrid system)。半導體雷射輸出的光訊號經由光偵測器接收並轉換成電流訊號，經適當的放大及衰減，將電訊號回授並驅動半導體雷射，藉由調整操作參數，系統可以操作在不同的狀態區，例如規則脈衝區(Regular Pulsing, RP)及混沌脈衝區(Chaotic Pulsing, CP)，在此同時我們將考畢子(Colpitts)振盪器產生的調變訊號注入光電回授系統，將造成半導體雷射載子濃度(carrier density)的改變，進而產生新的混沌訊號，有四個調變組合方式可產生混沌訊號:
(1)週期一(Period-1, P1)振盪訊號直接調變雷射規則脈衝區
(Regular Pulsing, RP)、(2)混沌振盪(Chaotic Oscillation, CO)訊號直接調變雷射規則脈衝區(Regular Pulsing, RP)
、(3)週期一(Period-1, P1)振盪訊號直接調變雷射混沌脈衝區(Chaotic Pulsing, CP)、(4)混沌振盪(Chaotic Oscillation, CO)訊號直接調變雷射混沌脈衝區(Chaotic Pulsing, CP)，經由模擬結果可得知混沌振盪訊號直接調變混沌脈衝區可產生相關性較好的訊號，雖然同樣無法完全消除相關性曲線的sidelobes，但相較於傳統濾波器方式，其具有較低的相關性，因此可增加雷達容許雜訊的空間，降低偵測錯誤的機率。

%半導體雷射可直接電流調變的特性，將電路產生訊號驅動雷射後經由光偵測器接收後回授，藉此使得半導體雷射載子密度
%(carrier density)產生變化，分別分析在四種調變方式下的訊號變化:(1)P1(period-1)振盪訊號直接%調變RP(Regular Pulsing)狀態區(2)P1(period-1)振盪訊號直接調變CP(Chaotic Pulsing)狀態區
%(3)混沌(Chaotic)振盪訊號直接調變RP(Regular Pulsing)狀態區(4)混沌振盪(Chaotic Oscillation;CO)訊號直接調變CP(Chaotic Pulsing)狀態區，經由模擬結果可得知第四種調變方式可產生較好correlation特性的訊號，雖然同樣無法完全消除相關性曲線的sidelobe，但相較於傳統濾波器方式，其Peak Sidelobe Level更低，因此可增加雷達容許雜訊的空間，降低偵測錯誤的機率。

We implemented a chaotic Colpitts oscillator with an AT41486 bipolar junction transistor. Experimental results indicate that, chaotic signals can be obtained with wide bandwidths in the microwave band. A range resolution of about 5 cm is obtained for potential application. The microwave Colpitts oscillator exhibits rich nonlinear dynamical behaviours. But the correlation curve of the chaotic signal show many sidelobes which makes the unambiguous detection difficult. This is because the spectrum of the chaotic signal is not very flat and smooth. Therefore we try to get better characteristics of the chaotic signal through simulating two schemes.
The first scheme uses a filter as the tranditional way. By simulating the filtered results of chaotic signal through the Chebyshev low pass filter, we find that the sidelobes of the correlation curve are not substantially lowered.
The second scheme uses an optoelectronic feedback hybrid system. The optical output from a semiconductor laser is fed back to itself optoelectronically with a fixed DC bias current. By tuning the operating parameters, this system can be operated in different instable regions. For instances, regular pulsing (RP) region and chaotic pulsing (CP) region. Simultaneously, the modulation signal from Colpitts oscillator into optoelectronic feedback system, which will alter the carrier density of the semiconductor laser. There are four schemes used to generate the modified chaotic signals: (1) period-1 oscillation (P1) signal direct current modulating on regular pulsing region (RP) of the laser, (2) chaotic oscillation (CO) signal direct current modulating regular pulsing region (RP) of the laser, (3) period-1 oscillation (P1) signal direct current modulating on chaotic pulsing region (CP) of the laser, and (4) chaotic oscillation (CO) signal direct current modulating chaotic pulsing region (CP) of the laser. We find that the fourth scheme has the best correlation characteristic among them. Although the sidelobes of the correlation curve can not be eliminated completely, the second scheme has better correlation characteristic than the first. Therefore, it can increases noise tolerance of a radar system and reduces probability of making a detection mistake.

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