Bandwidth Enhancement of Microstrip Comb-Line Antenna Fed from Both Ends

Millimeter-wave antennas have been developed for various applications such as broadband high-speed wireless communication systems and automotive radar systems. Microstrip antennas are more advantageous than other millimeter-wave antennas at the viewpoints of low profile and low cost [1]. On the other hand, transmission loss of microstrip line is significant problem in array feeding. So, microstrip array antennas are suitable for relatively low-gain applications such as a subarray of digital beam forming (DBF) systems. A comb-line feeding system is effective at the point of relatively low loss compared with other microstrip patch array antennas fed by parallel or ordinary series-feeding [2]. However, travelling-wave array antenna has a significant problem that gain is degraded by beam shift due to frequency changes when the array antenna is fed from one edge of the feeding line. This paper proposes the way to reduce the gain degradation due to frequency change by feeding from both ends of the microstrip comb-line antenna (MSCLA). Simulated performance of the designed antenna is reported in this paper.