In this paper, we propose a closely spaced two-port microstrip patch antenna system with significant isolation enhancement (> 90 dB), which can be deployed for MIMO as well as full-duplex transceiver systems. We deploy a resonant combination of rectangular defected ground structure (DGS) and a near-field decoupling structure (NFDS) in the vicinity of a closely spaced (inter-element spacing = 0.01λ 0 ) two-port microstrip patch antenna system at 5.85 GHz. This drastically reduces the port-to-port mutual coupling (< −90 dB), which can help in self-interference cancellation for full-duplex point of view without any additional circuitry, while still preserving desired impedance matching performance (< −15 dB). The broadside gain of individual antennas in the two port MIMO system is 7.11 dBi, with 97% efficiency and coto-cross-polar level < 25 dB. The proposed concept is validated by full-wave simulation in CST Microwave Studio, as well as experimental results on fabricated prototype. Moreover, MIMO performance metrics such as total active reflection coefficient (TARC), envelop correlation coefficient (ECC) and channel capacity loss (CCL) are analysed using simulation and measurement.
In this paper, we propose a compact four-port dual-band MIMO antenna with suppressed higher order modes (HOMs). First, complementary split ring resonator (CSRR) loading is used on a square microstrip antenna to achieve simultaneous miniaturization and dual-band response. Next, the HOMs in the proposed CSRR loaded MIMO configuration are analysed using equivalent circuit model as well as surface current distribution plots. By placing a single shorting post close to antenna center line, these HOMs of the four-port dual-band MIMO antenna are then suppressed, while maintaining satisfactory mutual coupling (< −11 dB) and impedance matching (< −15 dB) performance in the operating band. Furthermore, simulated and measured values of total active reflection coefficient (TARC), envelop correlation coefficient (ECC) and channel capacity loss (CCL) are within the desired levels of −10 dB, 0.5 and 0.5 bits/s/Hz respectively, signifying good diversity performance of the proposed MIMO antenna.
INDEX TERMSComplementary Split Ring Resonator (CSRR), Higher Order Modes (HOMs), Microstrip Antenna, Multiple Input Multiple Output (MIMO).
This paper presents, a mutual coupling reduction technique between a very closely spaced (1.8 mm) two-element microstrip based MIMO antennas using a modified inverted-fork shaped decoupling (m-IFSD) structure. The m-IFSD consists of an inverted fork and a cross shaped structure with a shorted via. The combined effect of inverted-fork and shorted cross shaped structure results in mutual coupling reduction below −35 dB between adjacent antenna elements. The decoupling technique is analyzed using an approximate transmission-line model and field distribution. Further, the two-element MIMO antenna design is extended to 8-element MIMO configuration to improve the MIMO diversity. To verify the proposed isolation technique a two-element MIMO antenna prototype is fabricated and measured. The proposed MIMO antenna exhibits a low mutual coupling (< −35 dB) with good impedance matching (< −10 dB) at 5.45 GHz. The MIMO antenna provided a total active reflection coefficient (TARC) less than −10 dB and envelop correlation coefficient (ECC) (for isotropic propagation scenario) less than 0.5. Finally, the ECC of the proposed MIMO antenna system is analyzed for a realistic Gaussian/Uniform propagation scenario for various incidence angles and angular spreads to better understand the effect of the mutual coupling reduction technique.
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