Abstract
A miniaturized dual-frequency dual-polarization microstrip patch antenna with high isolation between receiving and transmitting ports (operating at 2.1 GHz for receiving and at 2.5 GHz for transmitting) is presented in this paper. The proposed antenna consists of a modified rectangular radiating patch, two 50 Ω microstrip feed lines, and two EBG filters. Two coupling microstrip lines are employed to excite two orthogonal fundamental modes (TM10and TM01). The high isolation is achieved by embedding two novel EBG filters underneath two feed lines to reject the incoming signal from the opposite line. Multilayer configuration, miniaturized EBG filters, and modified rectangular radiation patch contribute to size reduction. The total size is 0.67λ × 0.67λ × 0.03λ , only quarter of the multilayer rectangular radiation patch antenna (1.33λ × 1.33λ × 0.03λ) using common EBG filters with the same performance. Measured results on the reflection coefficients, isolations, and gains for the two frequencies are provided, which agree well with the numerical simulations. Also, measured isolations and radiation patterns at both two resonant frequencies are compared with the antenna without filters. The results show that the proposed method improves isolation by more than 20 dB with little influence on the radiation patterns.
Highlights
Dual-frequency dual-polarization antennas are often required for frequency reuse to enhance communication system capacities
Dual-frequency dual-polarization can be realized by using a pair of feeds to, respectively, excite two orthogonal fundamental modes from a single radiating patch; this type of antenna has a poor isolation between two exciting ports
By placing defected ground structure (DGS) under the feed line, port isolation can be improved by 20 dB [2, 3], but DGS
Summary
Dual-frequency dual-polarization antennas are often required for frequency reuse to enhance communication system capacities. In [4], two filters based on electromagnetic bandgap structures (EBGs) have been investigated in order to increase the isolation Two filters based on spiral defected microstrip structures (DMS) are used to enhance the ports isolation [5]. Both DMS filters are compact near 0.1λ, two quarter-wave-length transformers are needed to match the antenna impedance. A novel EBG filter with a compact size of 0.18λ × 0.06λ is embedded underneath the feed line to enhance the isolation between receiving and transmitting ports. The total size of the DEP-EBG filter and the spaces between filter and patch is smaller than 0.2λ. The total size of the proposed antenna is 0.67λ × 0.67λ × 0.03λ, which is smaller than that of the antenna (1.33λ × 1.33λ × 0.03λ) in [4]
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