Aperture coupled microstrip antenna with extremely low profile

An extremely low profile (0.022λ_c, λ_c is the wavelength of the central frequency) microstrip antenna with two H-shaped serial coupling slots for bandwidth enhancement is proposed in this paper. Compared with one coupling slot, a broader impedance bandwidth is available by employing two serial slots. Two coupling slots resonate at adjacent frequency that expands the antenna impedance bandwidth. The H-shaped slots, which shift the resonant frequency to the relatively lower band, can reduce the coupling slot length. Key parameters of coupling slots are investigated and discussed by resorting to simulation results. Measurements of the antenna prototype agree well with the simulation results which exhibit 6.63% impedance bandwidth (S11<;-10dB) from 1.415GHz to 1.512GHz. The prototype exhibits a peak gain of 5.79 dBi and the 3dB beam width of 56° and 112° in the E- and H-planes, respectively, besides the cross polarization level of -20dB down from the co-polarization.