An ultra-wideband dual circularly polarized slot antenna with high isolation

An ultra-wideband dual circularly polarized (CP) slot antenna with high isolation is presented. Two L-shaped probes are on the upper layer, both a ladder strip outside and a bent strip in the center on the bottom layer. The L-shaped probes and the ladder strip result in four impedance resonance modes, and the bent strip moderates real and imaginary impedances to achieve an ultrawide impedance bandwidth. Furthermore, two L-shaped strips on the ladder strip make two linear polarized Modes 1 and 2 into two CP modes at the low- and mid-frequency bands. Meanwhile, the bent strip combined with the L-shaped probes creates the third CP resonance mode at the high-frequency band. The cutting corner and bent slots on the ladder strip change the amplitude and the phase of the electric fields Ex and Ey to realize ultra-wideband CP radiation. In addition, the port-port isolation is enhanced because the currents are concentrated on the bent strip, and the coupling current path is cut off with the bent slot. The fabricated antenna achieves a -10-dB impedance bandwidth of 111% (1.7-5.94 GHz), a 3-dB axial ratio bandwidth of 101% (1.7-5.2 GHz), and a port-port isolation of better than 20 dB. Besides, our antenna obtains a high peak gain of 8.1 dBi and a lower profile of 0.004 & lambda;L, where & lambda;L is the lowest frequency wavelength of the operating bands in vacuum. These performances make the proposed design competitive for wireless communications. An ultra-wideband dual circularly polarized slot antenna with high isolation of better than 20 dB is presented. The L-shaped probes and the ladder strip result in four impedance resonance modes, and the bent strip moderates impedances to achieve an ultrawide impedance bandwidth. Two L-shaped strips on the ladder strip make two circularly polarized modes at the low- and mid-frequency bands, and the bent strip combined with the L-shaped probes creates the third CP resonance mode at the high-frequency band.image