A quarter-wave U-shaped patch antenna with two unequal arms for wideband and dual-frequency operation

Patch antennas are receiving increasing interest in various mobile communication systems since they can provide advantages over traditional whip and helix antennas in terms of high efficiency, low EM coupling to the human head and increased mechanical reliability (see Pattnail, S.S. et al., 1998). The main disadvantages are their narrow impedance bandwidth and large size for mobile applications. Several techniques have been proposed to overcome the size problem of conventional patch antennas. Many efforts have recently been taken to improve the bandwidth of the shorted patch antennas. For our previous design (see Guo, Y.X., et al., Electron. Lett., vol.35, no.24, p.2069-70, 1999), the substrate thickness must be within a range to obtain a wide impedance bandwidth. Broadband and dual-frequency shorted U-shaped patch antennas are presented. Different-length arms of the U-shaped patch are used to produce two staggered resonant modes. For a given substrate thickness, a wide impedance bandwidth can easily be obtained. The proposed antenna is simpler in structure than regular stacked patch antennas (see Zaid, L. et al., IEEE Trans., vol.AP-47, no.4, p.654-60, 1999), and has more freedom on the choice of bandwidth and size than our previous design.