High-power broadband-loaded monopole antenna with sleeve ground plane for portable applications

Abstract

This paper presents a novel design (loaded antenna with sleeve as a ground plane) for broadband-loaded monopole antenna. Monopole antenna is usually known for its narrow bandwidth characteristics. To achieve broad impedance bandwidth, the narrow bandwidth characteristics of wire monopole antenna is overcome by proper capacitive or inductive loading. The high capacitive behavior of antennas at low frequencies is controlled using RF transformer in conjunction with proper matching network. The proposed antenna is capable of handling high power up to 100 Watts CW. The bandwidth characteristics of the proposed antenna are investigated through optimization routine namely Genetic Algorithm in CST Microwave Studio. A bandwidth of 10:1 within the frequency range of 84–890 MHz is achieved with antenna length of 1.9 m. By switching the antenna to different configurations with length of 1.4 m, bandwidth of 750 MHz (from 250 MHz to 1 GHz) is also achieved. The antenna radiation pattern is measured using anechoic test chamber. The antenna measured and simulated results are in good agreement.

Keywords:

• Genetic Algorithm
• RF transformer
• capacitive loading
• impedance bandwidth