Four-Port Dual-Frequency Dual-Polarized Antenna With Reduced Size and Improved Isolation

In this paper, a four-port dual-frequency dual-polarized antenna with reduced size and improved isolation is proposed. Initially, the proposed antenna achieves dual-frequency and dual-polarized performance on a symmetrical patch by exciting four ports in the appropriate positions. Then, the four short-circuited T-shape metal baffles are placed symmetrically to improve the isolation among these four ports. Simultaneously, the isolation of the low-frequency band can be further improved by symmetrically loading two sets of short-circuited strip branches. In addition, a notch is introduced by loading a pair of annular branches at the bottom of the substrate to decrease the mutual interference between high and low frequency working bands. In the end, the antenna that was suggested has been tested through simulation and proven to be effective. According to the results, the proposed antenna operates in the frequency bands of 3.46-4.24 GHz (20.2%) and 4.42-5 GHz (12.3%). And the isolation among the four ports is greater than 14.9 dB. Meanwhile, it maintains a compact size of 0.424λ
0
× 0.379λ
0
× 0.148λ
0
(λ
0
is the free-space wavelength at the center frequency of the lower-band).