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【正文】 圖 7 線極化的輻射圖 4 結束語 本文中，我們提出了一種設計同時擁有圓極化和線極化特性的雙頻貼片天線的方法。 圖 4 軸比的頻率特性 與圖 3 相比，圖 5 顯示了 測量到的天線阻抗特性。 第五步 設置天線的攝動單元和饋點來獲得在低諧振頻率下的圓極化。2 ( ) ( / , )L rrcf W W W L t??? ? ? ? ? （ 2） 其中 c 為自由空間的光速， r? 為有效的介電常數，通常 121 1 1 0( , ) 122r yyxy x???? ??? ? ????? （ 3） 39。 1 傳統雙頻微帶貼片天線的結構 圖 1 顯示了傳統線極化雙頻天線的結構。因為平面天線在低成本、重量輕和穩定性方面的優點，已經被廣泛研究并較好的應用于多頻帶系統中。2 ( ) ( / , )L rrcf W W W L t??? ? ? ? ? (2) where c is the velocity of light in free space， r? is the effective permittivity given by 121 1 1 0( , ) 122r yyxy x? ??? ??? ? ????? (3) And 39。A Novel Method for Designing DualFrequency Slot Patch Antennas with Two Polarizations WU Di1, OH ISH I BA SH I H idekazu2, SEO Kazuyuk i2, I NA GA K IN aok i3 (1. Department of Communication Engineering , Shang hai University , Shang hai 202172, China。 1 . 5 0 . 4wlWWWL??? ? ????? (4) ,rLW g tt ????? ???? (5) Here ? ? ? ?1 0 . 3 3 6 1, 0 . 2 8 0 . 2 7 4 l n ( 2 . 5 1 8 )0 . 5 5 6xyg x y x? ????? ? ? ? ???? ?? (6) and the upper frequency is determined by 2 ( 2 ) ( / , )H rrcf L l d w t??? ?? (7) In above expression, the parameters of W, L, t, w, d, l are referred to Fig 2, and the r? is the dielectric constant of the substrate. However, in this study, in order to obtain a circular polarization at the lower resonant frequency, the aspect ratio of the outline size of the patch will be changed so that the mentioned formulas above will not be pletely satisfied. Fig 2 Configuration of dualfrequency We present a design method for dualfrequency slot patch antenna with two polarization as follows. Step 1 Design a square patch antenna with the desirable lower frequency f10 by using a conventional method. Step 2 Etch two slots close and parallel to the radiating to behave the dualfrequencies operation by using Eq (7). However the lower resonant frequency f10 will change, since the slots modify the current distribution of the TM10. Step 3 Adjust the size of the antenna element to obtain the desired lower resonant frequency. Step 4 Adjust the length and the width of the slots to obtain the upper resonant frequency f30. Step 5 Set perturbation segment and place the feed point on the diagonal axis of the antenna to obtain the circular polarization at the lower resonant frequency f10. 3 Experimental results and discussion We experimentally designed a dualfrequency patch antenna with two polarizations. Figure 2 shows the configuration of the antenna, and the specifications are listed in Table 1. In this configuration of the antenna, we extended the L edge of the patch antenna to set the perturbation segment, and placed the feed point on the diagonal axis to achieve the circular polarization. Table 1 Specifications of a dualfrequency patch antenna with two polarization GPS VICS Frequency/GHz Polarization