| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 102 === In this discourse, three compact and broadband microwave components are developed, which include the microstrip-fed antenna using two unsymmetrical monopoles and L-shaped ground, microstrip line-to-rectangular waveguide transition using semi-circle and ground resonators, and rectangular waveguide-to-circular waveguide transition using semi-circle and ground resonators.
First of all, a compact (25×15×0.8 mm3) and UWB (3.1 to 10.6 GHz) microstrip-fed antenna using two unsymmetrical monopoles and L-shaped ground is proposed. By properly selecting the resonance lengths of three monopoles, an ultra wide band performance can be achieved. The frequency range for which the reflection coefficient is less than -10 dB covers from 3.2 GHz to 10.6 GHz (105.7%), covering the whole UWB. Also, the antenna maintains an omni-directional radiation pattern for both the E-plane and H-plane. Furthermore, the antenna provides averagely more than 80% efficiency and its gain varies from 1.3 dBi to 3.27 dBi.
Secondly, a compact and broadband microstrip line-to-rectangular waveguide transition using the semi-circle and ground resonators is proposed. The bandwidth for which the reflection coefficient is smaller than -15 dB covers the frequency range from 8.2 GHz to 12.6 GHz, which is estimated to be 42.7 %. The corresponding transmission coefficient in this frequency range is larger than -0.18 dB. As compared with the microstrip line-to-rectangular waveguide transition using the antisymmetric tapered probe [23], the circuit size is greatly reduced from 400 to 250 mil while the broadband response is maintained.
Thirdly, a compact and broadband rectangular waveguide-to-circular waveguide transition using the semi-circle and ground resonators is proposed. The bandwidth for which the reflection coefficient is smaller than -15 dB covers from 9.3 GHz to 11.75 GHz, estimating to be 23.8%, while the corresponding transmission coefficient in this frequency range is larger than -0.05 dB. As compared with the rectangular waveguide-to-circular waveguide transition using various techniques [29]-[32], the mechanical complexity is reduced while the compact size and the broadband response are maintained.
In order to verify our design, a microstrip-fed antenna, one back-to-back MSL-to-RWG circuit, and one back-to-back RWG-to-CWG circuit are fabricated and measured where the measurement results are in good agreement with the simulation results.
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