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This paper presents a multiple-input, multiple-output (MIMO) antenna system with the ability to perform full-azimuth beam steering, and with the aim of realizing greater than 20 Gbps vehicular communications. The MIMO antenna described in this paper comprises 64 elements arranged in a daisy chain array structure, where 32 subarrays are formed by pa...
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In this paper, two kinds of design methods of combining the multidimensional (MD) orthogonal frequency division multiplexing (OFDM) with coded direct index modulation (CDIM) system and multiple‐input multiple‐output (MIMO) technology are proposed to increase the spectrum efficiency more. These systems can be called as dimension‐dependent system and...
Citations
... A fluidically loaded dielectric lens has been deployed for singleelement beam-steering in a modified antipodal Vivaldi antenna element (Zhao et al. 2017). Beam steering in both azimuth and elevation planes have been facilitated by rotating two all metal transmit-array lenses placed above the antenna (Honda et al. 2020). Azimuthal beam-steering can be obtained by arranging the antenna elements of MIMO in a daisychain structure (Liu et al. 2013). ...
In this work, beam-steering in THz MIMO antennas has been demonstrated using two different types of graphene-based intelligent reflective surface. Equivalent circuit models of intelligent reflective surface unit cells have been proposed for demonstrating their reflection characteristics. Two types of microstrip patch-based THz MIMO in side-by-side configuration and orthogonal configuration have been designed to exhibit S11 lower than − 15 dB and radiation efficiency greater than 95%. Band-stop FSS has been employed to reduce the mutual coupling of MIMO antennas which are arranged in side-by-side configuration. The MIMO antennas have been integrated with graphene-based intelligent reflective surface for simultaneous steering of four beams radiated by the antenna elements. The reflectivity of the intelligent reflective surface relies on the conductivity of graphene which can be modified by changing its bias voltage. A digital 1-bit coded metasurface has been designed using graphene-based intelligent reflective surface. By varying the bias voltage on the graphene-based unit cells, the pattern of the digital code is modified on the intelligent reflective surface, which causes beam-steering of MIMO antennas placed above it. Gain improvement of 4 dB takes place when the intelligent reflective surface behaves as an AMC for the MIMO in linear configuration. Maximum gain improvement of 10 dB is obtained for the intelligent reflective surface integrated MIMO in orthogonal configuration with radiation efficiency greater than 90%. Numerical simulations using finite integration technique have been performed for illustrating the rotation of beam in MIMO antennas.
... A fluidically loaded dielectric lens has been deployed for single-element beam-steering in a modified antipodal Vivaldi antenna element [15]. Beam steering in both azimuth and elevation planes have been facilitated by rotating two all metal transmit-array lenses placed above the antenna [16]. Azimuthal beam-steering can be obtained by arranging the antenna elements of MIMO in a daisy-chain structure [17]. ...
In this work, beam-steering in THz MIMO antennas has been demonstrated using two different types of graphene-based intelligent reflective surface (IRS). Equivalent circuit models of IRS unit cells have been proposed for demonstrating their reflection characteristics. Two types of microstrip patch-based THz MIMO in side-by-side configuration and orthogonal configuration have been designed. Band-stop FSS has been employed to reduce the mutual coupling of MIMO antennas which are arranged in side-by-side configuration. The MIMO antennas have been integrated with graphene-based IRS for simultaneous steering of four beams radiated by the antenna elements. The reflectivity of the IRS relies on the conductivity of graphene which can be modified by changing its bias voltage. A digital 1-bit coded metasurface has been designed using graphene-based intelligent reflective surface (IRS). By varying the bias voltage on the graphene-based unit cells, the pattern of the digital code is modified on the IRS, which causes beam-steering of MIMO antennas placed above it. Gain improvement of 4 dB takes place when the IRS behaves as an AMC for the MIMO in linear configuration. Maximum gain improvement of 9 dB is obtained for the IRS integrated MIMO in orthogonal configuration. Numerical simulations using finite integration technique have been performed for illustrating the rotation of beam in MIMO antennas.
... Figure 9a shows the Rice channel model, whereas Figure 9b is the vector diagram of signals in the complex plane. A Monte Carlo simulation was conducted using this model [31]. Hereafter, we consider the proposed antenna to be located at the center of the circle where the scatterer is placed, as depicted by the broken line in Figure 9a. Figure 10a shows the results of the estimation of the AOA based on the cooperative operation of the MIQ method with the K-factor as a parameter, whereas Figure 10b is the estimation error of that method. ...
... The weight functions are determined in such a way that the gain in the communication direction of the combined radiation pattern yields a maximum value [31]. All elements are phase-shifted by τ i to be in the in-phase state at the angle of the incoming wave in consideration of the electromagnetic mutual coupling. ...
... A spatial fading emulator is implemented using the Monte Carlo simulation [31]. In the fading emulator, the radio waves radiated from the scatterers, which are the controlled amplitude and phases of the signal used to emulate a Rayleigh fading channel, are summed around the evaluating antennas, and the desired radio environment is then generated [37,38]. ...
To ensure high-reliability communication in healthcare networks, this paper presents a smart gateway system that includes an angle-of-arrival (AOA) estimation and a beam steering function for a small circular antenna array. To form a beam toward healthcare sensors, the proposed antenna estimates the direction of the sensors utilizing the radio-frequency-based interferometric monopulse technique. The fabricated antenna was assessed based on the measurements of complex directivity and the over-the-air (OTA) testing in Rice propagation environments using a two-dimensional fading emulator. The measurement results reveal that the accuracy of the AOA estimation agrees well with that of the analytical data obtained through the Monte Carlo simulation. This antenna is embedded with a beam steering function employing phased array technology, which can form a beam spaced at 45° intervals. The ability of full-azimuth beam steering with regard to the proposed antenna was evaluated by beam propagation experiments using a human phantom in an indoor environment. The received signal of the proposed antenna with beam steering increases more than that of a conventional dipole antenna, confirming that the developed antenna has great potential of achieving high-reliability communication in a healthcare network.
... The m-MIMO array antenna (160x4) elements are arranged in a rhombic pattern to achieve better coverage in all directions, which is desired for the base station application [9]. The distance between each array element from its center is 20cm. ...
... Most of the activity so far undertaken in developing massive MIMO systems has been directed toward providing large-scale MIMO antennas at the BS, with antennas comprising more than 100 antenna elements [4,5], and there are few reports of doing something similar at the MS [6]. The author is currently developing a method to achieve a large-scale MIMO antenna system that maintains an invariable channel capacity over the full-azimuth at the MS, such as, for example, a connected ground-based or flying car [7]. ...
... To analyze the capability of the developed antenna [7], the author proposed a Monte Carlo simulation with randomly arranged scatterers [10]. A small number of differently positioned scatterers were set for each BS antenna using random numbers, confirming that the channel matrix created can achieve full-rank status similar to conventional Monte Carlo simulation. ...
... As shown in Figure 8, the average channel capacity increases with increasing Δφ. These results can be understood from Figure 7b, because the channel capacity is calculated using the eigenvalues of the channel matrix [7]. Moreover, the channel capacity measured at Δφ = 5.1° achieves 97% of the analytical outcome; indicating that the observed result corresponds to the simulation value. ...
This paper presents an over-the-air testing method in which a full-rank channel matrix is created for a massive multiple-input multiple-output (MIMO) antenna system utilizing a fading emulator with a small number of scatterers. In the proposed method, in order to mimic a fading emulator with a large number of scatterers, the scatterers are virtually positioned by rotating the massive MIMO antenna. The performance of a 64-element quasi-half-wavelength dipole circular array antenna was evaluated using a two-dimensional fading emulator. The experimental results reveal that a large number of available eigenvalues are obtained from the channel response matrix, confirming that the proposed method, which utilizes a full-rank channel matrix, can be used to assess a massive MIMO antenna system.
... The disadvantage of this method is that it requires many instruments, such as a probe antenna, a power divider, and a phase shifter. However, a fading emulator is capable of emulating realistic and accurate multipath environments [20][21][22][23][24]. ...
... One of the most common approaches to analyze a MIMO antenna system is to use Monte Carlo simulation, where many scatterers are arranged on a circle, known as Clarke's model [28], to simulate a multipath fading channel in a mobile propagation environment; this results in the evaluation of the MIMO terminal performance [24]. A multipath propagation environment is simulated by the amplitude and phase of each wave radiated from the scatterers, which is an aggregation of all the information in the radio waves emitted by the BS antennas. ...
... The MIMO terminal is located at the center of the emulator. This fading emulator functions as an operating algorithm based on the same formulation described in [24]. The instruments, such as the network analyzer (Keysight, HP8753E), power combiner/divider (mini circuit, ZAPD-2-S+ and ZB8PD-252-S+), and phase shifter (mini circuit, JSPHS-23+), have bidirectional characteristics at the measurement frequency. ...
This paper presents a method of implementing a 4 × 4 correlation matrix for evaluating the uplink channel properties of multiple-input multiple-output (MIMO) antennas using an over-the-air measurement system. First, the implementation model used to determine the correlation coefficients between the signals received at the base station (BS) antennas via the uplink channel is described. Then, a methodology is introduced to achieve a 4 × 4 correlation matrix for a BS MIMO antenna based on Jakes’ model by setting the initial phases of the secondary wave sources in the two-dimensional channel model. The performance of the uplink channel for a four-element MIMO terminal array antenna is evaluated using a two-dimensional bidirectional fading emulator. The results show that the measured correlation coefficients between the signals received via the uplink channel at the BS antennas using the proposed method are in good agreement with the BS correlation characteristics calculated using Monte Carlo simulation and the theoretical formula, thereby confirming the effectiveness of the proposed method.
This paper presents a method to eliminate the phase difference ambiguity in angle of arrival (AOA) estimation using the radio-frequency-based interferometric monopulse technique. In order to uniquely determine the AOA, we utilize four directivities which are formed by using selected elements with the same weight function as the AOA estimation. We investigate the AOA estimation accuracy for the direction of the incoming wave from a high elevation angle and in multi-path propagation environments using a three-dimensional fading emulator. The results show that the proposed method is valid for complex propagation environments.
