|標題:||單埠及多埠隙孔耦合微帶天線 : 設計與應用|
Slot-Coupled Microstrip Antennas with Single or Multiple Ports : Designs and Applications
Dr. Shyh-Jong Chung
|關鍵字:||隙孔耦合微帶天線;回授天線振盪器;廣角回波天線陣列;雙圓極化天線;動差法;積分方程法;雙埠天線;偏移饋入之隙孔天線;slot-coupled microstrip antenna;feedback antenna oscillator;retrodirective antenna array;dual circularly polarized antenna;method of moments;mixed-potential integral equation;two-port antenna;offset-fed slot antenna|
In this thesis, we propose and analyze several slot-coupled microstrip antennas with single or multiple ports for applications in active integrated antennas, remote identification, and communications. These antenna structures consist of (a) adding a second port to the traditional slot-coupled microstrip antenna to obtain a brand-new two-port antenna, (b) arranging several slot-coupled microstrip antennas to achieve a planar retrodirective antenna array, and (c) using two slot antennas constructed with the Wilkinson power divider configuration to form a novel dual circularly polarized antenna. To analyze these antenna structures of slot coupling feed, Galerkin's method of moments together with a mixed-potential integral equation (MPIE) was used. Also, the microstrip feed line was modeled as a waveguide for simplifying the problems. The two-port slot-coupled microstrip antenna contains a feeding port and a coupling port. Most of the incident power coming from the feeding port is radiated by the microstrip patch, and part of the power enters to the coupling port. A feedback antenna oscillator was designed by applying the present structure where it served as a feedback resonator and a radiator at the same time. The oscillation was stable and with a clean spectrum at the frequency of 9.79 GHz which was only 0.2% different from the design one. An effective isotropic radiated power (EIRP) of 39 mW was achieved. The measured cross-polarized fields were at least 15 dB lower than the co-polarized ones. Next, a planar antenna array reflector with retrodirectivity in both the E-plane and the H-plane is analyzed and demonstrated at X-band. The reflector consists of six pairs of symmetrically located slot-coupled patch antennas paired by microstrip lines. The total reflected field from the reflector is separated into three primary components, that is, the reradiation field from the patch antennas (RFPA), the scattering field from the patch antennas (SFPA), and the scattering field from the ground plane (SFGP). The first two components are calculated by using the method of moments and the last one is by the physical optics (PO) method combined with the method of equivalent currents (MEC). By tuning the microstrip-line lengths, the total reflected field contributed by the three components is designed to possess a broad-beamed pattern in both the E-plane and the H-plane. The measured reflected-field patterns of the fabricated reflector show good agreement with the designed ones. Finally, an offset-fed slot antenna was used to replace the lumped resistor in the equal-split Wilkinson power divider, and a dual CP slot antenna operating at S-band was designed and fabricated experimentally. The antenna possessed a return loss bandwidth of 39.3%, an isolation bandwidth of 10.3% for VSWR < 2, and a 3-dB axial ratio bandwidth of 28%.
|Appears in Collections:||Thesis|