Low-Profile Tripolarization Patch Antenna Using Hybrid Substrate

A new method of realizing pattern diversity patch antenna with three polarization directions is presented. By concentrically placing a thin cylindrical dielectric with high permittivity underneath a metal circular ring patch, we can lower resonant frequency of the monopolar TM₀₂ mode significantly, whereas resonant frequency of the broadside mode, i.e., two degenerate orthogonal TM₁₁ modes, basically remains unchanged. Thus the antenna is able to provide a vertical polarization with an omnidirectional radiation pattern and two orthogonal horizontal polarizations with unidirectional radiation patterns at the same frequency. Besides, the antenna height is as low as 0.038λ₀ (λ₀ is the free-space wavelength of the center frequency) that can be attributed to the careful arrangement of the hybrid substrate. Simulated results show that high isolation level better than 30dB is obtained between the ports.