本論文設計出一支應用衛星定位系統(GPS)之天線。一般衛星訊號接是以圓極化的方式來接收避免多重路徑反射的干擾以及法拉地旋轉的效應，操作頻帶主要以能覆蓋於GPS 的L1 (1.575 GHz)頻段以及L3(1.381 GHz)的頻段為主。製作過程中主要會利用 HFSS 軟體來進行天線模擬與設計，並藉用網路分析儀測量實作天線的特性。 本天線設計於 FR-4 基板上，天線尺寸為 12.4×12.4×0.8 mm3，目標天線以 50 毆姆同軸電纜做為天線之饋入結構。藉由使用單極天線(Monopole)饋入外加一M形寄生原件使天線可以激發兩個正交模態，再利用接地面不等長的特性，使兩個正交模態產生 90 度的向位差，進而達成圓極化的效果。並且，在天線與接地面之間焊上一顆SMD0201型可變電容，利用改變偏壓可改變容值的特性，達成天現頻率可重置的目的。 天線頻寬以-6dB 以下反射損失的定義下達成在低頻帶可以涵蓋GPS L3 (1.381 GHz)頻段達到29 MHz的絕對頻寬，而高頻部分可以在GPS L1 (1.575 GHz)頻段擁有45 MHz的絕對頻寬，皆有達到GPS天線24 MHz絕對頻寬之要求。 天線在電磁波無反射室內量到的遠場響應中，L1與L3頻段皆是以右手圓極化輻射，並且增益皆大於 0 dBic。 ;The designs of antennas for global satellite positioning system (GPS) are presented in the thesis. Generally, the satellite signal is circularly polarized to avoid the interference of multiple path reflections and the Faraday rotation. The operating frequency is designed to cover the band of L1 (1.575 GHz) and L3 (1.381 GHz). In the designing process HFSS software for antenna simulation and design will be used, and the network analyzer will be applied for measuring the characteristics of the implementation of the antenna. The antenna is designed on the FR-4 substrate with the size of 12.4 × 12.4 × 0.8 mm3, and fed by a 50-Ω mini-cable. The monopole feed with an M-shaped parasitic element makes the antenna resonate with two orthogonal modes. With the 90 degrees phase difference set up by the characteristics of the unequal length of the ground plane, a circularly polarized radiation pattern is generated. A SMD0201 varactor is added to the antenna and the ground plane to change the operating frequency by changing the bias voltage on the M-shaped parasitic element. The antenna bandwidth based on the 6-dB reflection coefficient are 29 MHz in the GPS L3 (1.381 GHz) band, and 45 MHz in the GPS L1 (1.575 GHz) band, which meets the bandwidth requirements of 24 MHz in GPS applications. The far-field response of the antenna is measured in the antenna measurement chamber. Both of the L1 and L3 bands radiate a right-hand circularly polarized EM wave, and the gain are greater than 0 dBic.
