本論文為設計應用於2.4 GHz諧波倍頻偵測獵能標籤，著眼開發一個可應用於獵能及被感測定位的新型標籤架構。此標籤不同於以往獵能器在敘述反射諧波時皆視之為可獵獲能量的損失，配合具有物件位置識別（方向偵測）之功率發射器共同組成一射頻獵能系統時，可藉由獵能器反射之倍頻諧波強度大小提供位置(定位偵測)或距離資訊（距離偵測）。利用在獵能電路中接上開關可控式諧波反射源，即可達到當功率發射器發射一訊號時，標籤可由雙頻天線接收基頻訊號和傳送倍頻訊號。倘若射頻電子標籤能量尚未獵取完成(未完成充電)時，則傳送倍頻諧波訊號至發射端，使功率發射器之天線陣列透過波束成型（Beamforming）技術搜尋並明確定位該標籤，為其快速充電。並於標籤充電過程中，逐漸降低倍頻諧波反射功率大小，增加獵能電路整流器的功率轉換效率。
本論文將提供雙頻天線、倍頻諧波增強耦合器之設計和分離式元件組裝於FR4電路板上驗證。當電路板中輸入功率+5 dBm時，開關切換前後所偵測的諧波得以有4.3 dB的差異，並在開關切換前後效率由27 %變至42 %，大幅提高15 %的轉換效率。此外本論文還利用晶片電路設計驗證相同概念，以期進一步改善因分離式電路板之體積與重量限制可裝載的接收器種類和分離式開關需額外偏壓控制開關切換的問題。晶片採用TSMC 90 nm製程進行製作。積體化除了改善體積大小需求與無須提供額外偏壓給予開關外，還大幅增加轉換效率(Power conversion efficiency, PCE)、可進行效率轉換之輸入功率範圍(Range of input power)與增強倍頻諧波偵測效果。獵能晶片在量測輸入功率為-7.2 dBm時功率轉換效能最高可達72%，且在輸入功率+5 dBm時，開關切換前後得以有近40 dB的差異，且可接收輸入功率範圍為14 dB。由於獵能整流電路主要是將天線接收後訊號由交流(AC)轉換為直流(DC)供應後端電路，整流電路的好壞可由整流電路的靈敏度與功率轉換效率判斷。但整流器的電路普遍為配合前端天線接收頻率與後端電路所需的供應電壓進行設計，因此以往的研究發表中鮮少針對獵能整流電路提出評比指標(Figure of merit, FOM)。為了對整流電路設計的優劣有較為具體的比較，最後於本論文將提出兩種FOM作為獵能整流電路的評比指標以供參考。

In this thesis, we propose a novel energy harvesting tag that can be applied to the radio frequency (RF) energy harvester with a second-harmonic identification capability. For the traditional RF energy harvester, the reflected harmonic wave is often regarded as a loss part of available energy. Different from the traditional ones, we proposed a tag with a stronger reflected harmonic in location detection mode and a better power conversion efficiency in energy hunting mode. By adding a switch-controllable harmonic reflection source in the harvester circuit, when the dedicated RF power emitter transmits a 2.4 GHz signal, the tag receives the signal by a dual-band antenna and reflects the related second-harmonic wave back to the power emitter, simultaneously. If the tag is not fully charged, according to the second-harmonic signal provided by the tag, the power emitter can identify the location of the tag and enhance the transmission of beamforming power, so that the tag can be charged quickly. As long as the tag is charged up gradually, the reflected second-harmonic signal strength will also be decreased gradually. The power conversion efficiency (PCE) can be optimized automatically.
This thesis presents the design of a dual-band antenna, a second-harmonic-enhanced coupler, and an energy harvester on the FR4 circuit board with discrete components. When the input power is +10 dBm, the harvester tag can provide a 4.4-dB difference of second-harmonic signal strength for location use. In energy hunting mode, the power conversion efficiency is increased from 27% to 45%, and the power conversion efficiency is greatly improved by 18%.
In order to prevent the tag from being out of the requirement of small volume and light weight, we implement a harvester IC chip by TSMC’s 90 nm process. In addition, we can use the rectifier output voltage to reduce the magnitude of the second-harmonic wave by using a PMOS switch. From the experimental results, we can get an enhanced difference of second-harmonic power in location detection mode, and a better power conversion efficiency and a wider input power range in energy hunting mode. The energy harvester IC chip has the maximum power conversion efficiency up to 72% when the input power is -7.2 dBm. When the input power is +5 dBm, the harvester can provide a 40 dB difference of second-harmonic signal strength between the previously mentioned different modes. The input power range, which is defined by the boundaries of power conversion efficiency greater than 10% and input power smaller than -10 dBm, is 14 dB. Finally, we proposed two FOM expression as the evaluation indexes of the energy harvesting circuit performances which have not been mentioned yet in previous research papers for a fair comparison.

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