對於身為司法警察的執法人員，於偵查犯罪行為時，為達成蒐集犯罪證據之任務，均會靈活運用通訊器材以達成任務工作，在行動蒐證過程中，會利用偵防車輛對犯罪嫌疑人進行跟監，以有效掌控犯罪嫌疑人之行蹤，完成犯罪蒐證之任務。當執法人員進行跟監時，為避免被跟監對象察覺而暴露身分，有必要將偵防車輛之汽車無線電傳收機(Mobile Radio Transceiver)天線加以偽裝及多元化，以順利達成工作任務。 為達成研製發展偵防車輛之汽車無線電傳收機天線偽裝及多元化之目標，個人覺得目前市面上有大部分之自用小客車安裝數位電視天線，未來應會更加普遍及全面性，已是趨勢所在，此一購想燃起個人之研究動機，本論文之主題就是利用低成本之數位電視天線，設計成汽車無線電傳收機傳輸之天線，其研究目的在於改變傳統無線電傳收機所普遍使用之鞭形天線(whip antenna)，達成汽車無線電傳收機傳輸天線偽裝及多元化之設計目標。汽車無線電傳收機所使用之傳輸天線，除了要達成偽裝及多元化之目標外，傳輸天線之小型化亦是本論文所考量之設計方向，在論文中所提及之微帶天線便能達到天線小型化的目標。本篇論文中所設計之兩款天線，均依上列所提之目標為設計之準則，個人利用低成本數位電視天線及自行模擬之微帶天線，輔以網路分析儀作為天線之量測器材，經過多次不斷測試與實驗，將天線修正及改製成汽車無線電傳收機所能使用之傳輸天線，其中一款型式為螺旋天線(helical antenna)，另一款為微帶天線(patch antenna)，所研究模擬天線之規格界定如下：1、兼具發射與接收功能2、頻率範圍為171MHz－173MHz3、天線駐波比(SWR)<1.5，以上兩款模擬設計之天線經網路分析儀量測後，均能符合原先所要規劃設計之天線規格，其中所設計利用低成本數位電視天線作成之螺旋天線，模擬初步之雛型後，實際安裝於汽車無線電傳收機上，充當傳輸之天線使用，試用情形良好，並已成功量產且實際運用於行動蒐證工作，執行成效卓著。 As a member of the laws enforcement personnel, one needs to progressively and actively exploit communication apparatus to collect evidence to accomplish his mission during his investigation of criminal activities. In the process of evidence searching and collecting it sometimes needs to use surveillance vehicle to track and monitor the suspect so as to effectively track the suspect’s activity to accomplish his task. In order to hide and not to expose the laws enforcement personnel’s identity when he is in the pursuing and monitoring the suspect, he needs to camouflage and diversify the antennas of the Mobile Radio Transceiver equipped in his surveillance vehicle to vigorously accomplish his task.
In the course of developing and designing a diversified antenna of the Mobile Radio Transceiver the author realizes that it becomes popular and having as a trend that people starts installing digital television antenna in his vehicle so that he can enjoy the entertainments when he is traveling. The thought comes to author’s mind of installing antennas, alike the digital television antenna, for Mobile Radio Transceiver in the surveillance vehicle so that it will be easily hide and falsify the identity of the surveillance vehicle. The main task of this thesis is to design and develop transmission antennas for the Mobile Radio Transceiver by utilizing the available low cost digital television antenna. And furthermore it is the main purpose of this thesis to modify the whip antenna that is used in the conventional Mobile Radio Transceiver to accomplish the design task of camouflaging and diversifying the transmission antennas of the Mobile Radio Transceiver. In addition to camouflage and diversify the transmission antennas, how to miniaturize the antennas is also the design’s goal considered. We accomplish this miniaturization task by using patch antenna in our design. We design and demonstrate two kinds of antennas, helical and patch, in the thesis and we adopt all the tasks mentioned in the above as our design criterion. We fabricate the transmission antennas of the Mobile Radio Transceiver by modifying and retuning the low cost digital television antenna and by associating it with our developed patch antenna. We use network analyzer to measure and experiment the performance of the designed antenna during the design evolution. The considered main specifications for the transmission antennas are summarized as in the following, 1. It possesses both the transmitting and receiving capabilities. 2. It operates in the frequency range of 171 – 173 MHz. 3. The voltage standing wave ratio is limited to 1.5 Through various measurements by utilizing network analyzer the performances of both designed antennas all meet the specified specifications. Furthermore by installing the helical antennas on the surveillance vehicles they all show satisfactory performance in the field tests. It has been mass produced and installed in the surveillance vehicles to actually perform the task of investigating and collecting evidence information they all achieve outstanding performances.