The use of coplanar waveguide (CPW)-fed ultra-wideband antennas in applications of multi-system integration has been demonstrated in this paper. Spiral slot antennas and feeding structures were fabricated on the same plane of the substrate so that the circuit process and the position alignment could be simplified. A CPW-fed spiral slot antenna possessing the ultra-wideband characteristic is also suitable for integration with a monolithic microwave integrated circuit (MMIC) module. Variations of the measured initial resonant frequency due to substrate thickness, number of turns and slot width are discussed in this paper. In addition, two topologies of the CPW-fed spiral slot antenna were devised and measured to demonstrate the capability of lowering the initial resonant frequency by adding a circularly microstrip stub at the end of the feedline and placing a short pin to terminate the spiral slot and feedline. According to the measured results, the CPW-fed spiral slot antenna covered most of the commercial wireless communication and satellite communication systems in radio frequency (RF), microwave and millimeter-wave applications.

Active frequency-tuning beam-scanning leaky-mode antenna arrays have been demonstrated in this paper. These antennas integrated one or several microstrip leaky-wave antenna elements with a single varactor-tuned HEMT VCO as an active source. Noted that the measured scan angles of the 11 and 14 antennas were approximately 24 and the scanning range of the 12 antenna was 20. Furthermore, reflected wave due to the open end of each leaky-wave antenna element has been suppressed by the symmetric configuration of this antenna array and the antenna efficiency increases. When comparing with the measured radiation pattern of the single element antenna, we found that the 12 and 14 antenna arrays can effectively suppress the reflected power by more than 5.5 dB and 10.5 dB, respectively, at 10.2 GHz. The power gain are more than 2 dB and 3.16 dB higher than the single element antenna with a measured EIRP of 18.67 dBm.