| Summary: | 博士 === 國立臺北科技大學 === 電腦與通訊研究所 === 102 === In this dissertation, in order to sufficiently utilizing the UHF band for both mobile, digital broadcasting, and space communications scenarios, we proposed not only the design of miniaturized antennas and 1×4 switched-beam smart circuit for usage of consumer devices, but also the RF module of hybrid rocket.
Firstly, a novel multimode miniaturized antenna is proposed for operation in the digital television (DTV) reception band (470-862 MHz) throughout the world. To achieve broadband characteristics, the proposed spiral antenna is constructed using seven resonance paths in the ground plane. The impedance matching and bandwidth of the spiral antenna are significantly affected by the sheet metal on the signal line. The antenna is able to realize an omnidirectional radiation pattern for the entire frequency band.
Regarding the need of multi-band for mobile communications, the second study applied printed inverted-F monopole antenna to design the 7-frequency band to cover from GSM-850 (824-894 MHz), GSM-900 (880-960 MHz), DCS-1800 (1710-1880 MHz), PCS-1900 (1850-1990 MHz), UMTS (1920-2170 MHz), GPS (1575.42±5 MHz), to IEEE 802.11 (2400-2484 MHz). With printed inverted-F monopole antenna, a gap between the fed and the ground path was added and the ground path was extended to excite the low-frequency resonant frequencies as well as combine with multi-path resonant frequencies to achieve multi-frequency resonances.
Next, the 1×4 switched-beam smart circuit is presented, which is composed by a miniaturized branch-line coupler and a miniaturized 45° phase shifters based on the newly proposed π-equivalent microstrip lines. The miniaturized 1×4 switched-beam smart circuit can create four phase modes ±45° and ±135° for the circuit path through a microcontroller. Four generated beams can reduce the interference from other directions to enhance indoor LTE communication.
The final topic aims to implement the telematics between hybrid rockets and the ground receiving station. In order to largely reduce the rocket weight, Fiber-Reinforced Plastic (FRP) is utilized for the hybrid rocket casing, on which coplanar wraparound antennas with the operation frequency 433 MHz are designed. The antenna structure contains three coplanar printed patches, in which the middle printed patch is the primary radiator and the resonant length appears half-wavelength. The RF module with high receiver sensitivity and high-power power amplifier are included to enhance the communication coverage of hybrid rockets and the ground receiving station so that the ground receiving station could effectively tracking the hybrid rocket.
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