A compact high gain dual-band antenna array for WLAN applications

Abstract

The continuously growing number of wireless devices and the demand for wireless local area network (WLAN) coverage received a lot of research and design attention during the past decade. The WLAN application is a popular dual-band IEEE standard, which operates in two distinct bands with a large centre frequency ratio. This dissertation presents the design and performance of a compact, high gain, dual-band and directional antenna array meant to be used for such applications. The low band, as stated by the IEEE 802.11b standard, covers the frequency range of 2.400 GHz to 2.484 GHz, and the high band is defined by IEEE 802.11a and starts at 5.150 GHz and stops at 5.850 GHz. The frequency ratio between the centres of the two bands is 2.25:1 and is considered a large ratio. The antenna array design is based on an existing dual-band antenna configuration. A parametric study was conducted on the antenna configuration features to obtain a detailed understanding of the antenna performance changes in relation to the physical parameters. The original design was modified to obtain a new sub-array design which can be used in an array for higher gain performance. The sub-array antenna element consists of one capacitively loaded dipole for the lower 2.4 GHz band and four smaller rectangular dipoles for the high 5.5 GHz band. The low band dipole is fed with a microstrip line whereas the four high band dipoles are fed with a slot line. Four of these sub-array antenna elements are configured into an array for increased gain performance. The final gain of the antenna array was measured as 12 dBi at the 2.4 GHz band and 16 dBi at the 5.5 GHz band. The radiation patterns of both the low and high bands have side lobes 10 dB below the main lobe and front to back lobe ratios of at least 17 dB. The volume of the final antenna is 128 _ 128 _ 12 mm3 and is compact compared to other dual-band antenna arrays. The continuously growing number of wireless devices and the demand for wireless local area network (WLAN) coverage received a lot of research and design attention during the past decade. The WLAN application is a popular dual-band IEEE standard, which operates in two distinct bands with a large centre frequency ratio. This dissertation presents the design and performance of a compact, high gain, dual-band and directional antenna array meant to be used for such applications. The low band, as stated by the IEEE 802.11b standard, covers the frequency range of 2.400 GHz to 2.484 GHz, and the high band is defined by IEEE 802.11a and starts at 5.150 GHz and stops at 5.850 GHz. The frequency ratio between the centres of the two bands is 2.25:1 and is considered a large ratio. The antenna array design is based on an existing dual-band antenna configuration. A parametric study was conducted on the antenna configuration features to obtain a detailed understanding of the antenna performance changes in relation to the physical parameters. The original design was modified to obtain a new sub-array design which can be used in an array for higher gain performance. The sub-array antenna element consists of one capacitively loaded dipole for the lower 2.4 GHz band and four smaller rectangular dipoles for the high 5.5 GHz band. The low band dipole is fed with a microstrip line whereas the four high band dipoles are fed with a slot line. Four of these sub-array antenna elements are configured into an array for increased gain performance. The final gain of the antenna array was measured as 12 dBi at the 2.4 GHz band and 16 dBi at the 5.5 GHz band. The radiation patterns of both the low and high bands have side lobes 10 dB below the main lobe and front to back lobe ratios of at least 17 dB. The volume of the final antenna is 128 _ 128 _ 12 mm3 and is compact compared to other dual-band antenna arrays. The continuously growing number of wireless devices and the demand for wireless local area network (WLAN) coverage received a lot of research and design attention during the past decade. The WLAN application is a popular dual-band IEEE standard, which operates in two distinct bands with a large centre frequency ratio. This dissertation presents the design and performance of a compact, high gain, dual-band and directional antenna array meant to be used for such applications. The low band, as stated by the IEEE 802.11b standard, covers the frequency range of 2.400 GHz to 2.484 GHz, and the high band is defined by IEEE 802.11a and starts at 5.150 GHz and stops at 5.850 GHz. The frequency ratio between the centres of the two bands is 2.25:1 and is considered a large ratio. The antenna array design is based on an existing dual-band antenna configuration. A parametric study was conducted on the antenna configuration features to obtain a detailed understanding of the antenna performance changes in relation to the physical parameters. The original design was modified to obtain a new sub-array design which can be used in an array for higher gain performance. The sub-array antenna element consists of one capacitively loaded dipole for the lower 2.4 GHz band and four smaller rectangular dipoles for the high 5.5 GHz band. The low band dipole is fed with a microstrip line whereas the four high band dipoles are fed with a slot line. Four of these sub-array antenna elements are configured into an array for increased gain performance. The final gain of the antenna array was measured as 12 dBi at the 2.4 GHz band and 16 dBi at the 5.5 GHz band. The radiation patterns of both the low and high bands have side lobes 10 dB below the main lobe and front to back lobe ratios of at least 17 dB. The volume of the final antenna is 128 _ 128 _ 12 mm3 and is compact compared to other dual-band antenna arrays.