A wideband multiple-input-multiple-output (MIMO) antenna system with common elements suitable for WiFi/2.4 GHz and Long Term Evolution (LTE)/2.6 GHz wireless access point (WAP) applications is presented. The proposed MIMO antenna system consists of four wideband microstrip feedline printed monopole antennas with common radiating element and a ring-shaped ground plane. The radiator of the MIMO antenna system is designed as the shape of a modified rectangle with a four-stepped line at the corners to enhance the impedance bandwidth. According to the common elements structure of the MIMO antenna system, isolation between the antennas (ports) can be challenging. Therefore, the ground plane is modified by introducing four slots in each corner to reduce the mutual coupling. For an antenna efficiency of more than 60%, the measured impedance bandwidth for reflection coefficients below -10 dB was observed to be 1100 MHz from 1.8 to 2.9 GHz. Measured isolation is achieved greater than 15 dB by using a modified ground plane. Also, a low envelope correlation coefficient (ECC) less than 0.1 and polarization diversity gain of about 10 dB with the orthogonal mode of linear polarization and quasi-omnidirectional pattern during the analysis of radiation characteristic are achieved. Therefore, the proposed design is a good candidate for indoor WiFi and LTE WAP applications due to the obtained results

In this paper a wideband multi-input multi-output (MIMO) antenna system for WiFi-LTE wireless access point (WAP) application is proposed. The MIMO antenna system consists of two common element microstrip-fed monopole antennas with dual polarization. Physically closed integration of MIMO antenna elements requires a special technique to increase the isolation between the antennas. A novel structure of parasitic element is introduced to improve the isolation between the antennas. The proposed MIMO antenna system is simulated and optimized using CST Microwave Studio. The designed antenna system is fabricated and measured to verify the simulation results. Reflection coefficient of less than −10 dB and isolation more than 15 dB are achieved in the operating frequency range of 2.3–2.9 GHz which covers WiFi 2.4 GHz and LTE 2.6 GHz bands. The proposed system also provides dual polarization with 10 dB polarization diversity gain and envelope correlation coefficient less than 0.15. Each individual antenna has a gain of 5.1 dB and 68% efficiency.

Abstract-In this paper, a new method that called the "Stepped Cut at Four Corners" is introduced to design a multi-mode/broadband modified rectangular microstrip patch antennas (MRMPAs). In order to become acquainted with the new method, the design process of a monopole broadband MRMPA suitable for multifunctional wireless communication bands is explained. The methodology of the proposed broadband MRMPA design is presented in six stages. The first stage is designing a single-mode RMPA. Subsequently, by creating a step at the corners using the proposed method a dual-mode antenna is obtained at the second stage, while the triple-mode and multi-mode antennas are designed, at the third and fourth stages respectively. Two types of broadband antennas are obtained, the stepped line and straight line antennas. By increasing the number of steps, the antenna's operating bandwidth (BW), with return loss less than −10 dB, covers the frequency range from 900 MHz to 2.6 GHZ, which is suitable for GSM (900 MHz and 1.5 GHz), WiFi (2.4 GHz) and LTE (2.6 GHz) applications. In addition, the antenna prototype has been fabricated and measured in the all stages, in order to validate the simulation results, and there is a close agreement between the simulated and measured results.

In this paper, a dual-polarized multiple-input multiple-output (MIMO) antenna system suitable for indoor wireless access point is proposed. The presented MIMO antenna system consists of two coplanarwaveguide-fed monopole antennas with orthogonally polarized modes. According to the closely spaced structure of the MIMO antenna system, the mutual coupling between the ports is a big challenge. Therefore, a new structure of parasitic element is introduced in order to improve the mutual coupling between the ports. For the purpose of validating the simulated results, the antenna prototype has been fabricated and measured; the comparison of the results shows that there is an acceptable agreement between the measurement and simulation results. The proposed design covers the frequency bands of WiFi (2.4 GHz), Worldwide Interoperability for Microwave Access (2.3 and 2.5 GHz), and Long-Term Evolution (LTE; 1.5 and 2.6 GHz) applications with a reflection coefficient less than À10 dB and a mutual coupling coefficient better than À15 dB. The MIMO antenna system provides an envelope correlation coefficient less than 0.15, polarization diversity gain more than 9.985 dB, and quasi-omnidirectional pattern within the expected frequency band. In addition, LTE downlink throughput measurements show that the proposed antenna system delivers data rates close to the theoretical maximum for quadrature phase shift keying, 16 quadrature amplitude modulation (QAM), and 64-QAM modulations. coefficients (S 12 and S 21 ) without CSPE are above À9 dB, indicating low isolation between the ports. The coupling coefficients (S 12 and S 21 ) with CSPE are À17 dB, justifying that good isolation between ports has been achieved. S-parameter resultsIn order to validate the simulated results obtained from CST Microwave Studio, the prototype has been fabricated and measured. The performance of the fabricated antenna is tested using a vector network analyzer to determine the reflection coefficient, isolation, voltage standing wave ratio, and bandwidth of the proposed antennas as well their operating frequency. Figure 4. Parametric study on the gap between ring number 3 and stepped line.Figure 5. Simulated S-parameter of the proposed MIMO antenna (a) without CSPE and (b) with CSPE. 5 of 11 DUAL-POLARIZED MIMO ANTENNA SYSTEM

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Abstract-Interference and multipath is one of the current issues in a wireless communication system, with complicated scenarios of environment especially in urban areas with a high number of users. Introducing smart antenna systems at the base station can contribute to reducing interference and improve quality of service. This paper proposes and explores the application of artificial immune system and negative selection algorithm to the prototype of smart antenna, where the proposed smart antenna is a hexagonal structure with 6-elements of the antenna array and working in LTE band at 2.6 GHz. Initial testing was done to define the RSSI value by calculating the average of the signal then comparing RSSI value defined by implementing artificial immune algorithm. To proof and determine actual RSSI signal received, a test in an anechoic chamber is conducted as reference that assumes free interference and multipath then compared to both of results. X-Bee module was used for transmitter and receiver in system at 2.4 GHz band, and the proposed system prototype with hexagonal structure also used dual ARM microprocessor. Negative selection algorithm is applied in smart antenna programming to define actual values of receiving signal and angle of arrival. Every beam of the antenna was installed with an X-Bee module then connected to microprocessors, with an LED installed at each of the antenna as an indicator of beam switching or angle of arrival signal.

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