# Multiport Single Element Mimo Antenna Systems: A Review
## 5 Summary  
In this paper, a concise review on different multiport single antenna element systems has been presented. Comparison has been done based on antenna size, substrate, number of ports, ECC, antenna gain, and radiation efficiency, and summarized in Tables 2 and 3 for the compared MIMO antenna designs. Designing a compact common radiator MIMO antenna system with strong isolation between antenna ports is important for future wireless communication. Several isolation techniques considered for MIMO antenna design are discussed in this review paper. By implementing DGS and CSRR technique, the MIMO antenna provides wide band with lower ECC values. The simple structure with a significantly improved isolation is achieved through a neutralization line technique and parasitic elements provide size reduction with improved efficiency. Similarly, other mutual coupling reduction techniques discussed in the literature offer better isolation, but maintaining improvement in efficiency and size reduction could be a challenge for shared radiator MIMO antenna design. The implementation of a slot on a common radiating patch is another technique for obtaining effective isolation between antenna ports but the antenna performance is affected. Similarly, CPW-fed structure provides easy integration but increase in space between the antenna elements leads to less suitability for portable devices. Compared to this CPW-fed structure, ACS structure provides good performance in decreasing the overall size, due to its half-ground identity of antennas. Additionally, the ACS-fed structure provides better performance with additional features such as single lateral ground-plane, wide bandwidth, and easy to integrate with portable devices. Figure 18: (**a**) Common radiator with square ring ground [82], (**b**) Quad-port MIMO antenna [83]. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**References** & **Frequency** & **Size/Material** & **Isolation** & **Isolation** & **Isolation** & **CC** & **Gain** & **No. of Ports/Application** \\  & **(GHz)** & **(mm\({}^{2}\))** & **Technique** & **(dB)** & **ECC** & **(dBi)** & **No. of Ports/Application** \\ \hline
[60] & 2.3-2.6 & 48 \(\times\) 33.8/FR4 & Slots/Ground slot & \(-16\) & 0.1 & 1.2 & 2/WLAN (2.4 GHz) \\ \hline
[61] & 2.3-2.9 & \(105\times 125/\)FR4 & CSFE rings & \(-15\) & 0.15 & 5 & 2/Wifi (2.4 GHz) and LTE (2.5 GHz) \\ \hline
[62] & 1.2-1.55 & \(110\times 130/\)FR4 & CSFE rings & \(-15\) & 0.15 & 3.3-5.6 & 2/Wifi (2.4 GHz), WMAX (2.3 and 2.5 GHz), and LTE (1.5, 2.6 GHz) \\  & 2.3-2.7 & \(110\times 130/\)FR4 & CSFE rings & \(-15\) & 0.15 & 3.3-5.6 & 2/Wifi (2.4 GHz), WMAX (2.3 and 2.5 GHz), and LTE (1.5, 2.6 GHz) \\ \hline
[63] & 2–6 & \(64\times 64\) mm/RT Duroid 5880 & Ground plane circular slot & \(-15\) & 0.02 & 3.2-6.1 & 2/MIMO applications \\ \hline
[66] & 31–10.6 & \(26\times 26\)/FR4 & 1 and U-shaped stub & \(-15\) & 0.02 & 2.2, 3.5, 2 & 2/Ultra-Wide Band \\ \hline
[65] & 2.6-11 & \(28.5\times 285/\)FR4 & Rectangular stub & \(-15\) & 0.01 & 1.5-3.7 & 2/Ultra-Wide Band \\ \hline
[67] & 3–11 & \(27\times 27\)/Regers TMM4 & Slot & \(-15\) & 0.01 & 3 & 2/Ultra-Wide Band \\ \hline
[68] & 3.1–10.6 & \(22\times 24.3\)/Regers TMM4 & Slots, open shut stub & \(-15\) & 0.02 & 2-5.5 & 2/Ultra-Wide Band \\ \hline
[70] & 2.4-12.75 & \(39\times 39\)/FR4 & Sub, meandered line & \(-15\) & 0.02 & 4.92 & 2/Ultra-Wide Band \\ \hline
[71] & 3.35-3.65 & \(90\times 50\)/FR4 & Positioning shorting strips & \(-20\) & 0.1 & 3.5 & 2/MIMO applications \\ \hline
[72] & 3.4-3.7 & \(130\times 50\)/FR4 & 3 shorting strips & \(-25\) & 0.017 & 4 & 2/MIMO applications \\ \hline
[73] & 2.1–2.9 & \(45\times 100\)/FR4 & Slot at ground plane & \(-14\) & 0.005 & 6.4 & 2/2.45 GHz WLAN band \\  & & & & & & and WMAX band (2.5-2.7 GHz) \\ \hline
[74] & 3-12 & \(45\times 45\) & Slot & \(-17\) & 0.01 & \(-4\) to 2 & 2/Ultra-Wide Band \\ \hline
[75] & 3-12 & \(41\times 41\) & Slot & \(-14\) & 0.01 & 2 & 2/Ultra-Wide Band \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Shared radiator antenna with two ports.