Dual band low-profile switched beam Square Loop Antenna with capacitively coupled feeds

Abstract

A low profile dual-band switched beam Square Loop Antenna (SLA) with capacitively coupled feeds is presented. Two co-centered square loops are capacitively coupled to the four vertical feeding probes by four rectangular feeding patches. The capacitively coupled feeding mechanism introduces capacitance into the antenna input impedance and cancels the high inductance due to the feeding probe and the close proximity of the ground plane. This feeding technique allows the antenna to be matched to a 50 ohm feed line and helps in the realization of a low profile SLA. The antenna has a height of 6 mm and it is developed for operating in 3.1 GHz and 3.8 GHz frequency bands. In both frequency bands when any of the four ports is excited, keeping other ports open circuited, the antenna generates a radiation beam tilted by 31 degrees from the broadside and directed away from the excited port, having a maximum directivity of 9.1 dBi. Thus by exciting one port at a time, the antenna can steer its tilted beam in four different quadrants to scan the entire space in front of antenna.Index Terms-low profile antenna, square loop antenna, capacitively coupled feed, beam steering, dual band antenna.

A Dual-Band Single-Feed Switched Beam Antenna for WLAN

“…The beam pattern can switch in two directions by changing the position of the feeding point, likewise in the work of [3], in which the antenna operated at 2.4 GHz and 5.2 GHz. Also the works presented in [4][5][6] have proposed a dual band, low-profile, switched beam square loop antenna with capacitively coupled feeds, a dual-band lowprofile capacitively coupled beam-steerable square-loop antenna and a low-profile switched-beam dual-band capacitively coupled square loop antenna. The antennas were developed to operate at 3.1 GHz and 3.8 GHz frequency bands for the work of [4] 3.8 GHz and 4.7 GHz frequency bands for the work of [5] and 4.1 GHz and 5.2 GHz frequency bands for the work of [6].…”

Software Controlled Beam Steerable Antenna

“…Later work on the pattern reconfigurable SLA has involved the design of a dual band capacitively coupled SLA (DBCCSLA) by Pal et al (2014aPal et al ( ,b, 2013b. This design, which is shown in Fig.…”

“…The low impedance bandwidth problem in the DBCCSLA has been overcome in later reported work by Pal et al (2014b) and Pal et al (2014a). This has been achieved by creating a gap at the center of each radiating arm of the SLA, which is fed via capacitively coupled feeding.…”

“…This has been achieved by creating a gap at the center of each radiating arm of the SLA, which is fed via capacitively coupled feeding. The air gap created in the centre of the SLA's arm gives rise to an additional 'loaded resonance' along with an 'unloaded resonance' whose frequencies are close to each other (Pal et al, 2014a). This creates an overlapping frequency band at the resonances that helps to create a wider impedance bandwidth.…”