Design of an omnidirectional transmit/receive antenna pair using mushroom‐like electromagnetic band‐gap structure

Abstract

This paper presents a transmit-receive (T/R) antenna pair with omnidirectional and broadband radiation performance. The proposed antenna combines a patch with mushroom-like electromagnetic band-gap (EBG) structures. The mushroom structures are utilized to enhance the radiation characteristics such as impedance bandwidth, directivity, and gain. Two T/R antennas with 3 Â 3 and 5 Â 5 arrays working in K-band are designed and fabricated, the transmit (TX) and receive (RX) antennas are printed on a single-layer grounded dielectric substrate. Both the TX and RX antennas consist of an array of mushroom-like EBG structures around the monopole microstrip antenna, which is loaded with four stubs and fed by a 50 Ω coaxial probe. The dimensions of the fabricated prototype 3 Â 3 array antenna are 3:58λ 0 Â 1:61λ 0 (λ 0 -the wavelength in free space at 24 GHz). The TX/RX measured impedance bandwidth (j S 11 j < À10 dB) are 9.58% (23.6 ~25.9 GHz), 12.08% (22.8 ~25.7 GHz), respectively. The measured peak gain is 3.45 dBi at 24.8 GHz. For the 5 Â 5 array antenna, the aperture size is 5:58λ 0 Â 2:61λ 0 . The measured impedance bandwidth (j S 11 j < À10 dB) is 9.17% (23.65 ~25.85 GHz) and 12.71% (22.65 ~25.7 GHz) for the TX and RX, respectively. The measured peak gain increases by nearly 2 dB. Measurement results show that both antennas have a TX/RX isolation level better than 20 dB and achieve monopole-like omnidirectional patterns over its operating frequency band.