I-Young Tarn

Design of a Planar Ultrawideband Antenna With a New Band-Notch Structure

A novel planar ultrawideband (UWB) antenna with band-notched function. The antenna consists of a radiation patch that has an arc-shaped edge and a partially modified ground plane. The antenna that makes it different from the traditional monopole antenna is the modification in the shape of ground plane, including two bevel slots on the upper edge and two semicircle slots on the bottom edge of the ground plane. These slots improve the input impedance bandwidth and the high frequency radiation performance. With this design, the return loss is lower than 10 dB in 3.1-10.6 GHz frequency range and the radiation pattern is highly similar to the monopole antenna. By embedding a pair of T-shaped stubs inside an elliptical slot cut in the radiation patch, a notch around 5.5 GHz WLAN band is obtained. The average gain is lower than -18 dBi in the stopband, while the patterns and the gains at frequencies other than in the stopband are similar to that of the antenna without the band-notched function.

A Novel Pattern Diversity Reflector Antenna Using Reconfigurable Frequency Selective Reflectors

A radiation pattern diversity reflector antenna is investigated. Novel switchable frequency selective reflectors are designed and developed to construct a square corner reflector antenna. By controlling a switching device on the frequency selective reflector, one can make it opaque or transparent to a vertically polarized incident wave. This antenna is fed by a monopole. By configuring the switch states of the frequency selective reflectors, various beam shapes can be formed and steered. Measured results of the antenna show good agreement with the calculated ones.

A Compact Dual-Band Pattern Diversity Antenna by Dual-Band Reconfigurable Frequency-Selective Reflectors With a Minimum Number of Switches

A novel compact dual-band pattern diversity antenna is proposed. Dual-band reconfigurable frequency-selective reflectors are designed and applied to form a right-angle corner reflector antenna with reconfigurable patterns. With only one switch, the reconfigurable frequency-selective reflector can be controlled to be transmissive or reflective to vertically polarized waves at 2.45 and 5.25 GHz. By changing the combinations of the switch states, multiple patterns can be obtained. A dual-band feeding antenna designed via using the coupling effects is made to achieve well-matching conditions in all circumstances corresponding to various switch states at both frequencies. The measured results show good agreement with the calculated ones and demonstrate good pattern diversity virtues.

A Dual-Mode Millimeter-Wave Folded Microstrip Reflectarray Antenna

A dual-mode folded microstrip reflectarray antenna was developed and demonstrated in this paper. The proposed folded reflectarray antenna contains three parts: a planar main reflector, a planar subreflector, and printed feed antennas. The main reflector is used to produce twisted reradiated fields and to provide phase compensation for focusing. The subreflector parallel with the main reflector is made of a substrate printed with high-density metal grid lines, which is transparent to perpendicularly polarized fields, but would reflect the parallel ones. Three fixed-position patch antennas with polarization parallel to the grid lines are created for the radar mode, so that the radiation beam is switchable. Another patch with perpendicular polarization is designed for communication. A simple approach was proposed for simulating and designing the folded reflectarray. Measured results show good agreement with the calculated ones.

An X-band SAR satellite payload design with low cost approach for disasters management

Taiwan Island was created by tectonic plate collision where the continent building is still active with numerous earthquake activities. Taiwan is also in one of the most prevalent monsoon and typhoon areas of the world. Monsoons and typhoons bring along heavy precipitation that produce significant threat of mud slide and land slide in the mountains. SAR satellite missions, with their advantages of all-weather capability, repeat pass, high spatial resolution and sufficient swath, can provide not only in-time coverage at disaster locations, but also environment monitoring, disasters assessment and resource survey. The images product will serve the needs of Taiwan government agencies first not only before and after the crises but also during the crises. However, the disasters management community users have been in shortage of timely low cost imaging data ever since the disasters management operations became effective. Thus, a low cost SAR satellite payload design effort has been initiated in NSPO (National Space Organization) with the satellites and key SAR technologies in Taiwan.