Design of Wideband Circularly Polarized Antenna and Balun with Radar Application
| Autor: | Jen-Chun Yeh, 葉人郡 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 First, this paper presents a circularly polarized (CP) equiangular spiral antenna operated over a wide range of frequencies. Contrary to the conventional spiral antenna using the coaxial line or the vertically connected feeding structure, a tapered microstrip balun is fully integrated into one spiral arm of the proposed antenna and hence this construction can be realized completely planar. The measured results show that the return loss is better than 10 dB from 3.75 to 18.6 GHz, the axial ratio is below 3 dB from 3 to 14.5 GHz, and the radiation is bidirectional with opposite polarization and 3.5 to 7 dBic peak gain. The time-domain characteristic of the transmitting/receiving radar system using the proposed ultra-wideband (UWB) CP antennas is investigated by transient response. The pulse distortion is insignificant and is verified by the measured results of the high signal fidelity (0.89) and the low variation of antenna group delay (0.1ns). The time-frequency analysis of the measured pulses is also investigated for the relationship between time- and frequency-characteristics of spiral antenna. Finally, the transmitting/receiving antenna system using the proposed antennas is constructed to demonstrate the CP characterization and to detect the target position. The distance between antenna and the target can be obtained with high accuracy and high resolution by measuring a very short signal pulse. The circularly polarized radar with no polarization tracking requirement is demonstrated by measuring a metallic rod with different orientation angle. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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