【摘要】：射頻識(shí)別RFID)技術(shù)是物聯(lián)網(wǎng)中非常重要的一部分。應(yīng)用于RFID系統(tǒng)讀寫(xiě)器的天線是其最重要的設(shè)備之一,目前已經(jīng)成為了研究熱點(diǎn)。一方面,遠(yuǎn)場(chǎng)應(yīng)用的RFID天線通常采用高增益的圓極化天線或天線陣列,以增加其讀取距離。近場(chǎng)的RFID讀寫(xiě)器天線則需要強(qiáng)磁場(chǎng),寬頻帶和低增益的特性,同時(shí)產(chǎn)生的磁場(chǎng)應(yīng)該均勻分布以避免產(chǎn)生漏讀現(xiàn)象。另一方面,RFID系統(tǒng)中的讀寫(xiě)器輸入輸出信號(hào)需要有較好的收發(fā)隔離,該隔離度成為影響系統(tǒng)靈敏度的重要因素之一。為了使得系統(tǒng)獲得更好的讀取標(biāo)簽信號(hào)能力,需要盡可能降低接收機(jī)中發(fā)射機(jī)信號(hào)的功率。 本文的研究工作是在射頻識(shí)別系統(tǒng)的理論研究和實(shí)踐設(shè)計(jì)領(lǐng)域中進(jìn)行的,根據(jù)RFID的實(shí)際應(yīng)用要求,主要對(duì)RFID系統(tǒng)中的讀寫(xiě)器天線、圓極化天線陣列、圓極化天線罩、近場(chǎng)天線、讀寫(xiě)器收發(fā)隔離技術(shù)等方面進(jìn)行了研究。所獲得的研究結(jié)論或成果對(duì)于推動(dòng)射頻識(shí)別技術(shù)的發(fā)展和應(yīng)用具有一定的應(yīng)用價(jià)值。本文的創(chuàng)新點(diǎn)如下 1針對(duì)系統(tǒng)對(duì)高增益圓極化輻射器的要求,本文重點(diǎn)研究了圓極化天線陣特性,理論分析了多種天線陣類型的耦合效應(yīng)并提出了一種具有引向器功能的圓極化天線罩。對(duì)偶極子、矩形貼片天線、圓形貼片天線三種圓極化天線陣列中各天線單元軸比的耦合效應(yīng)做了理論推導(dǎo),得到了任意天線陣元受耦合影響后軸比變化的表達(dá)式。對(duì)矩形微帶天線陣列駐波,軸比,方向圖做了詳細(xì)的仿真分析,結(jié)論是最佳軸向軸比的頻點(diǎn)會(huì)因?yàn)轳詈细淖?|S11|對(duì)耦合效應(yīng)較為敏感,方向圖則相對(duì)比較穩(wěn)定。提出的天線罩具有圓極化器和引向器的功能,可以使得線極化天線及天線陣獲得圓極化并提高增益,等效天線陣的部分功能。該天線罩使得線極化微帶單天線的增益提高達(dá)3dB以上 2基于磁場(chǎng)耦合原理的RFID讀寫(xiě)器近場(chǎng)天線近些年來(lái)發(fā)展很快。本文提出了雙S形導(dǎo)線環(huán)天線與雙層終端開(kāi)路天線,這兩種RFID近場(chǎng)天線同時(shí)具有寬頻帶和強(qiáng)磁場(chǎng)的特性,并且結(jié)構(gòu)緊湊,加工簡(jiǎn)單。兩種天線均由兩根導(dǎo)線組成,導(dǎo)線均使用彎折的方法,保證了天線上各處電流方向一致。雙S形天線通過(guò)彎折使得外環(huán)上的電流方向一致且強(qiáng)而內(nèi)部的導(dǎo)線上電流較弱,最大限度的利用了天線產(chǎn)生的磁場(chǎng)能量,并在饋電端使用巴倫將不平衡電流轉(zhuǎn)為平衡電流。雙層終端開(kāi)路天線的饋電位于下層,上層是輻射環(huán)。天線環(huán)終端有一段導(dǎo)線折向環(huán)內(nèi)部,可以保證外環(huán)遠(yuǎn)離波節(jié)點(diǎn),環(huán)上電流更強(qiáng)。相比于雙S形天線,該天線尺寸更小,并且饋電部分和輻射部分相隔離,很好的避免了相互之間的干擾,也不用采用巴倫等器件,降低了加工成本。 3針對(duì)近場(chǎng)天線本身對(duì)磁場(chǎng)的負(fù)面影響,本文研究了金屬對(duì)磁場(chǎng)的影響并提出改進(jìn)方案,對(duì)近場(chǎng)天線進(jìn)行了環(huán)境實(shí)驗(yàn),并提出了一種新型的天線結(jié)構(gòu)以降低天線本身對(duì)近區(qū)磁場(chǎng)的負(fù)面影響。通過(guò)詳細(xì)的金屬、液體環(huán)境實(shí)驗(yàn)和三種RFID系統(tǒng)應(yīng)用實(shí)驗(yàn),發(fā)現(xiàn)天線受到金屬、液體影響較大,其他介質(zhì)也會(huì)影響天線的磁場(chǎng)分布,但比金屬,液體影響小很多。針對(duì)天線結(jié)構(gòu)特點(diǎn)和近場(chǎng)天線導(dǎo)線對(duì)磁場(chǎng)分布的負(fù)面影響,提出一種改進(jìn)型的終端結(jié)構(gòu)并將其應(yīng)用在雙層終端開(kāi)路天線上。用一種電感結(jié)構(gòu)代替普通的直導(dǎo)線,這種新結(jié)構(gòu)有較長(zhǎng)的電長(zhǎng)度和對(duì)磁場(chǎng)影響較小的優(yōu)點(diǎn)。從仿真和實(shí)驗(yàn)的結(jié)果可以看出,該結(jié)構(gòu)可以很大程度的減小天線上金屬導(dǎo)線對(duì)磁場(chǎng)的影響,非常適合開(kāi)路結(jié)構(gòu)的近場(chǎng)天線。 4RFID系統(tǒng)的讀取性能除了和天線有關(guān),還和信號(hào)通道中輸入輸出信號(hào)的隔離性能有關(guān),隔離度直接影響了系統(tǒng)對(duì)標(biāo)簽信號(hào)的讀取能力。為了提高收發(fā)信號(hào)隔離度,除了使得天線自身反射降低以外,本文提出了新型的載波相消技術(shù)和提高耦合器隔離度的方法。用一種RFID輸入輸出信號(hào)檢測(cè)設(shè)備監(jiān)控RFID系統(tǒng)的讀寫(xiě)器信號(hào)和標(biāo)簽信號(hào),并用定向耦合器分離輸入輸出信號(hào)。在定向耦合器的耦合端增加一段高阻抗線來(lái)產(chǎn)生不匹配,使其產(chǎn)生的反射信號(hào)與耦合器隔離端的泄露信號(hào)等幅反向,提高了耦合器的定向性,使得定向性可以達(dá)到30dB以上。載波相消技術(shù)則利用對(duì)數(shù)檢測(cè)器,單片機(jī),矢量放大器,功分器,定向耦合器等,通過(guò)自適應(yīng)方法產(chǎn)生抵消信號(hào)。該抵消信號(hào)與接收的標(biāo)簽信號(hào)合路,使得標(biāo)簽信號(hào)通路中的讀寫(xiě)器信號(hào)功率水平大大降低。利用載波相消技術(shù)處理以后標(biāo)簽信號(hào)通路中的讀寫(xiě)器信號(hào)電壓僅為處理前的1/12。該技術(shù)對(duì)天線本身反射的信號(hào)也同樣有作用,彌補(bǔ)了耦合器的不足。
[Abstract]:radio frequency identification (rfid) technology is a very important part of the internet of things. The antenna applied to the RFID system reader-writer is one of its most important equipment, and has become a hot topic at present. on the one hand, an rfid antenna for a remote field application typically employs a high gain, circularly polarized antenna or antenna array to increase its read distance. The near-field RFID reader-writer antenna requires a strong magnetic field, a wide band and a low gain characteristic, and the generated magnetic field should be uniformly distributed to avoid the phenomenon of leakage. On the other hand, the reader/ writer input/ output signal in the RFID system needs to be well received and received, and the isolation becomes one of the important factors that affect the sensitivity of the system. in order for the system to obtain a better signal capability to read the tag, it is necessary to reduce the power of the transmitter signal in the receiver as much as possible. The research work in this paper is carried out in the field of the theoretical research and practice design of the radio frequency identification system. According to the actual application requirements of the RFID, the reader/ writer antenna, the circular polarized antenna array, the circular polarization antenna cover and the near field in the RFID system are mainly applied to the RFID system. the antenna, the reader/ writer transmitting and receiving isolation technology and the like are carried out, The results or results of the research have a certain application to the development and application of the radio frequency identification technology. Value. The innovation of this paper In order to meet the requirement of the system to the high gain circular polarization radiator, the characteristics of the circular polarization antenna array are studied in this paper. The coupling effect of multiple antenna array types is analyzed theoretically, and a circle with the director function is proposed. The coupling effect of the axial ratio of the antenna elements in the three circularly polarized antenna arrays of the dipole, the rectangular patch antenna and the circular patch antenna is theoretically derived, and the coupling effect of the arbitrary antenna array elements on the rear axle ratio is obtained. In this paper, a detailed simulation and analysis of the standing wave, the axial ratio and the direction diagram of the rectangular microstrip antenna array are carried out. The conclusion is that the frequency point of the optimal axial-axis ratio can be changed because of the coupling change. | S11 | The coupling effect is more sensitive, and the direction map is the same. The proposed radome has the functions of a circular polarizer and a director, so that the linear polarized antenna and the antenna array can be circularly polarized and the gain and the equivalent antenna array can be improved. and the antenna cover is used for improving the gain of the linearly polarized microstrip single antenna, Near-field antenna of RFID reader-writer based on magnetic field coupling principle of over 3dB In recent years, the development of double S-shaped conductor loop antenna and double-layer terminal open-circuit antenna is proposed in this paper. The two antennas are made up of two wires, the wires are all bent, and the antenna is ensured the two-S-shaped antenna is bent so that the current direction on the outer ring is consistent and strong, the current on the inner conductor is weak, the magnetic field energy generated by the antenna is used to the maximum extent, and the balun will not be balanced at the feeding end The current is converted to a balanced current. The feed of the open-circuit antenna of the double-layer terminal is at the bottom The upper layer is a radiation ring. The antenna loop terminal has a length of wire folded into the ring, which can ensure that the outer ring is far away from the node Compared with the double S-shaped antenna, the size of the antenna is smaller, the feeding part and the radiating part are separated, the interference between the feeding part and the radiating part is well avoided, In this paper, the influence of metal on the magnetic field is studied and the improvement scheme is put forward, and a new type of antenna structure is proposed to reduce the cost of the antenna. The negative effect of the body on the magnetic field in the near zone is carried out. Through the detailed metal, liquid environment experiment and the application of the three kinds of RFID system, it is found that the antenna is affected by the metal and the liquid, and the other medium can also influence the magnetic field distribution of the antenna, but Based on the characteristics of the antenna and the negative effect of the near-field antenna lead on the distribution of the magnetic field, an improved terminal structure is proposed and it should be in that open-circuit antenna of a double-layer terminal, an inductance structure is used instead of a common straight conductor, and the novel structure has a long electrical length and the structure can greatly reduce the influence of the metal lead on the magnetic field on the antenna, the read performance of the 4RFID system is related to the isolation performance of the input and output signals in the signal channel, In order to improve the isolation of the transmitting and receiving signals, a new carrier cancellation is proposed in this paper, in addition to the reduction of the reflection of the antenna itself. The invention relates to a method for measuring the isolation of a coupler, which comprises the following steps of: detecting a reader-writer signal and a label signal of an RFID system by using an RFID input and output signal detection device, A high-impedance line is added to the coupling end of the directional coupler to generate a mismatch, so that the reflected signal generated by the directional coupler is inverted with the amplitude of a leakage signal, such as a leakage signal at the isolation end of the coupler, so that the orientation of the coupler is improved, The directional property can reach above 30dB. The carrier cancellation technique uses a log detector, a single chip computer, a vector amplifier, a power divider, a directional coupler, and the like. and generating a cancellation signal by an adaptive method, wherein the cancellation signal and the received tag signal are in the same way, so that the label signal path the signal power level of the reader/ writer is greatly reduced, and the reader-writer in the label signal path after processing by using the carrier destructive technique The signal voltage is only 1/ 12 before processing. The signal is also the same as the signal reflected by the antenna itself
【學(xué)位授予單位】：西北工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TP391.44;TN820

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本文編號(hào)：2358836