A Compact Printed Dual-Band (915MHz/2.4GHz) Folded Monopole Antenna

A compact printed dual-band folded monopole antenna has been proposed for the operation at 915MHz and 2.4GHz ISM bands. The dual resonance operation from a monopole antenna with a total length lesser than 0.2.915MHz including a finite ground plane occupying 1/6th of the total antenna space is the main feature of the proposed antenna. Furthermore, the easier integration of the proposed dual-band antenna on the printed circuit board without using its ground plane is another important characteristic. The desired dual resonances were obtained by implementing a folded conductor pattern for the antenna's main radiator along with two rectangular conductor stubs deployed at different positions along the main radiator on a 60 x 20 x 1mm(3) FR4 substrate. The 915MHz resonance was caused by the folded conductor pattern of the main radiator with a stub located at its end while a shorter conductor segment was defined on the main radiator by placing the second rectangular stub at about 0.25 lambda(2.4GHz) caused the other resonance at 2.4GHz. The design of the proposed dual-band antenna was simulated and analyzed in ANSYS HFSS. The simulated return loss of about -18dB at both frequencies along with a peak realized gain of 3.2dB and 2.3dB were obtained at 915MHz and 2.4GHz respectively.