多頻段可重置性天線設計;Multi-band Antenna Design Using Reconfigurable Techniques

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题名:	多頻段可重置性天線設計;Multi-band Antenna Design Using Reconfigurable Techniques
作者:	洪啟彰,;Hung,Chichang
贡献者:	電機工程學系
关键词:	可重置性天線;槽孔天線;背腔式天線;變容器;reconfigurable antenna;slot antenna;cavity-backed antenna;varactor
日期:	2016-05-11
上传时间:	2016-06-04 12:55:00 (UTC+8)
出版者:	國立中央大學
摘要:	本博士論文主要針對在天線設計中應用可重置性(reconfigurable)技術的研究與討論。首先，提出一個雙頻可重置性槽孔天線設計，此天線結構為基於彎折之槽孔天線並且於天線分支中加入電路元件作為附載。在設計初期，將天線結構分解為數個區塊分析，獲得相對應之等效電路。藉由設定的中心頻率以及導入共振條件，可獲得等效電路的元件值。接著將被動元件置換成變容器(varactor)之後，天線之中心頻率便具有可重置的特性。在此設計中，可重置性天線其操作頻率分別為；2.4 GHz之S雷達波段以及1.227/1.381/1.575 GHz全球定位系統(GPS)。提出天線模組化設計方式建構出多頻段天線。首先基於一組串聯電容電感的共振電路，作為天線原型模組。在此原型模組中加入變容器，則可以設計出頻率可重置性天線模組。在圓形模組上，透過電容性耦合的饋入方式引入額外的共振模態，則可以得到寬頻天線模組。而設計出的這些模組具有不同的頻率範圍，並且可以利用組合的方式將以上設計之模組組合成多頻段天線，可應用於各種功能需求。在此章節中，透過建構4G-LTE天線來驗證天線模組組合。在可重置性模組中，其中心頻率設計在LTE700 (698-787 MHz)與GSM850 (824-960 MHz)的頻段之間切換，此模組僅需要20×20mm2。另一方面，在寬頻模組中，其中心頻率設計應用於GSM1800/ GSM1900/ UMTS/ LTE2300/ LTE2500 (1.71-2.59 GHz)，所需的頻寬為49.3%，此模組僅需10×10mm2。提出應用於GPS與S雷達波段之雙頻圓極化槽孔天線設計。在此設計中，使用非常薄之背腔(0.017 λ0操作在1.575 GHz)用來達到單方向輻射的特性。天線之雙頻操作分別是1. 利用共振模態產生1.575 GHz；2. 利用波導效果(waveguide transition)產生2.4 GHz。即使使用厚度非常小的背腔，在1.575 GHz仍可以獲得足夠的1.6 %(26 MHz)頻寬與在2.4 GHz 8.4% (203 MHz)的頻寬。接著，組合兩個雙頻背腔天線，並且使用PIN二極體作為相位調整機制的開關，可形成操作於1.575 GHz與2.4 GHz的雙頻右圓極化天線。其中，軸比分別為1.5 % (24 MHz)於1.575 GHz以及4.5 % (110 MHz)。提出使用共振電路元件之頻率可重置性天線。在此設計中，利用電容電感元件設計一個中心頻率為2.4 GHz之帶拒濾波器。由於帶拒濾波器的頻率選擇特性，可將天線的組態分為一個2.4 GHz的單極天線，3.3-3.7與5.15-5.85 GHz的四分之一波長槽孔天線。操作於2.4 GHz時，此單極天線為主要的輻射元件，而四分之一波長槽孔則會視為皆地面。此外，在3.3與5.5 GHz時，單極天線則是四分之一波長槽孔的接地面。因此，天線之間的相互耦合效果則不需關注。所設計的雙頻與三頻段天線的尺寸分別為8.5×10mm2與14.5×10mm2。最後，概括本論文所提出之研究成果，以及未來可研究內容於第六章。 ;In this dissertation, several multi-band antenna with reconfigurable techniques are presented. The first part of the dissertation focuses on using varactors in the antenna to achieve active reconfigurable operation. In Chapter II, a novel design of dual-band reconfigurable slot antenna is proposed. The configuration of the proposed antenna is based on a folded slot with a branch edge formed by multiple strips loaded with circuit components. In the design, the antenna is decomposed into networks, and the corresponding equivalent circuits are deduced. By applying resonant condition on the equivalent circuit at the desired center frequencies, the circuit components can be determined. The proposed design is later transformed into a reconfigurable antenna by using varactors. The antenna configuration is also modified for applying biasing voltages to varactors. Dual-band reconfigurable operation of antenna is studied and demonstrated for S-band applications at 2.45 GHz and GPS at 1.227/1.381/1.575 GHz. The design approach is described in details. Also, antenna measurements are conducted for design validation. In Chapter III, novel resonant modules for constructing multi-band mobile antennas are proposed. The basic configuration of the module, named as the prototype module, is designed based on a series LC resonant circuit. By adding a varactor to the module, it can be transformed into a reconfigurable module. By introducing an extra resonant mode with capacitive coupling to enhance the bandwidth, a wide-band module can be obtained. These modules have different frequency ranges, and can be combined into multi-band antennas for various applications. The proposed modules are demonstrated by constructing a 4G-LTE antenna. The reconfigurable module, which is of 20×20 mm2, is designed to switch between LTE700 (698-787 MHz) and GSM850 (824-960 MHz) bands. The wide-band module, which is of 10×10 mm2 and 49.3% bandwidth, is designed for GSM1800/ GSM1900/ UMTS/ LTE2300/ LTE2500 (1.71-2.59 GHz) applications. All designs have been realized and measured for validation. The proposed antenna modules, which are simple and convenient to use, can provide flexibility, especially in antenna deployment, in multi-band mobile antenna designs. The second part of the dissertation focuses on switchable polarization. In Chapter IV, a design of dual-band cavity-backed slot antenna loaded with a spurline is presented for GPS and S-band radar applications. In the design, a very thin cavity (0.017λ0 in thickness at 1.575 GHz) is used to achieve unidirectional radiation. The dual-band responses of the antenna are excited by the slot resonance at 1.575 GHz and waveguide transition effect at 2.4 GHz. Even with very small cavity thickness, reasonable impedance bandwidths are obtained as 1.6% (26 MHz) at 1.575 GHz and 8.4% (203 MHz) at 2.4 GHz. The proposed slot can also be loaded with a spurline to adjust the antenna center frequency and the phase of the radiated field. A switch using a PIN diode is deployed with the spurline. Since the spurline is in serial connection with the slot, the spurline and the corresponding bias circuit for the PIN diode have little effect on the antenna radiation. Two proposed slots are combined to form an antenna which is right-hand circularly-polarized at both 1.575 and 2.4 GHz. A phase delaying system consisting of delay line and the spurline is designed to achieve 90° phase difference at both frequencies. The axial-ratio bandwidths are obtained as 1.5% (24 MHz) at 1.575 GHz and 4.5% (110 MHz) at 2.4 GHz. Compared to the traditional designs in which the cavity thickness is often more then 0.25 , the proposed design with thin cavity is more suitable to be deployed on the vehicle surface. The last part of the dissertation focuses on the reconfigurable antenna with passive components. In Chapter V, a frequency reconfigurable tri-band antenna using resonant circuit is proposed. In the design, the resonant frequency of the LC parallel resonator is designed at 2.4 GHz, which formed a band-stop filter. With the frequency selective property of the band-stop filter, the configuration of the proposed antenna is transformed into a monopole at 2.4 GHz, and quarter-wave slots at 3.3-3.7, and 5.15-5.85 GHz, respectively. At 2.4 GHz, the monopole is the main radiator, the quarter-wave slots are performed as ground plane. Besides, at 3.3 and 5.5 GHz, the monopole is the ground plane of the quarter-wave slots. Thus, the mutual coupling effect of the antennas are not of concern. The fabricated dual-band and tri-band antenna have compact dimensions of 8.5×10 mm2 and 14.5×10 mm2, respectively. Both the dual-band and tri-band antennas are tested experimentally. Measured and simulated return loss and radiation patterns are in good agreement.
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