Compact narrow slot antenna with stable radiation pattern and wide bandwidth

Abstract

One of the most crucial parameters for any antenna is bandwidth. Over the whole extended bandwidth, the antenna achieves a high gain of 5dBi and a steady bidirectional radiation pattern. A novel design concept for increasing bandwidth and maintaining a consistent radiation pattern has been proposed for the radiated fields of a slot antenna. First, the radiated fields of the standard slot antenna are examined theoretically using characteristic modes (CMs). Its three CMs vibrate at 2.45, 4.78, and 7.17 GHz, respectively, according to the results. CM1 and CM3 both continue to emit radiation in both directions, but CM2 generates a radiation null in the broadside direction. After that, the linear slot is appropriately folded to change CM2’s non-bidirectional pattern into a bidirectional one, allowing for the broad bandwidth use of the neighbouring CM1 and CM2. The narrow slot is then used to create the stepped scheme, which reallocates these dual modes in close proximity to one another. By using these designs, the antenna’s radiation pattern consistency and small size of 0.022λo can be preserved, but its impedance bandwidth can be significantly expanded. After that, the proposed antenna is constructed and assessed. Measurements show that the antenna has a broad bandwidth (|S11|<−10 dB) of around 35.14%, covering the frequency range of 3.3 to 4.6 GHz.