Compact Multiport Antenna Research Articles

Digital pattern synthesis with a compact MIMO antenna of half-wavelength diameter

The paper presents a compact multiport antenna, with beamforming capabilities and a realized gain of 4.31 dBi with the size of λ/2. The antenna allows digital beamforming with independent control over three parameters: main-beam direction, beamwidth, and null-depth. Those parameters can be dynamically adjusted within a continuous range, create multiple beams for different frequency channels, and simultaneously generate multiple digital patterns. Due to digital beamforming capabilities, the proposed antenna offers much greater flexibility over switch-based analogue beamforming of Electronically Steerable Parasitic Array Radiator (ESPAR) antennas. The reconfiguration properties are achieved by using superposition of three dipole-like radiation patterns, where each radiator generates different spherical mode, i.e. with different angular phase distribution in the horizontal plane. This allows beamsteering with compact size, while the use of different modes ensures low Envelope Correlation Coefficient (ECC) from 10−4 to 3.2 × 10−5 for the operating frequency of 2.4 GHz. The proposed technique allows for significantly greater pattern reconfiguration than any reconfigurable antenna or array of comparable size and is a perfect candidate for Software Defined Radios.

A compact four‐element multiple‐input‐multiple‐output antenna with enhanced gain and bandwidth

AbstractA compact four‐element wideband planar multiple‐input‐multiple‐output (MIMO) antenna is proposed. The radiating elements are half‐loop monopoles. In order to cover the 5.8 GHz WLAN band, an additional high‐frequency operation mode is excited by an inter‐connected coupling parasitic element, and the radiation gain attained is enhanced via the arrangement of elements. The proposed four‐element MIMO antenna operates in a wide frequency range of 4.58‐6.37 GHz (34.3%), which covers the 5.2/5.8 GHz WLAN band and 5.5 GHz WiMAX band. For each element, an average gain of greater than 3.18 dBi is achieved, and the envelope correlation coefficient (ECC) between elements is lower than 0.05. The overall size of the compact multiport antenna system is only 40 × 36 mm2 with minimum isolation of 19 dB between its elements and has no any complex decoupling structure. Since the antenna has a satisfactory MIMO performance and is easily integrated with a planar structure, it is an excellent candidate for the MIMO communications application.

Single-Carrier Spatial Modulation for the Internet of Things: Design and Performance Evaluation by Using Real Compact and Reconfigurable Antennas

In this paper, for the first time, we propose two new solutions to boost the data rate between small connected objects such as glasses and cams and the 5th generation (5G) mobile network, based on spatial modulation, single carrier waveform, compact reconfigurable antennas at the object side and massive multiple input multiple output (M-MIMO) at the network side. In the first new wireless communication system, a "transmitting object" uses transmit spatial modulation with a compact reconfigurable antenna and a constant envelop amplifier to transmit in high data rate with a low complexity and low power consumption. The space-time digital processing capability of the M-MIMO 5G base station is used to detect such signal. In the second new wireless communication system, a "receiving object" uses receive spatial modulation, a compact multiport antenna and a low complexity detection algorithm to receive in high data rate with a low complexity signal processing. The space-time beamforming capability of the M-MIMO 5G base stations is exploited to deliver a signal that is pre-equalized enough to be detected by the object. For the first time, we present experiments showing that M-MIMO allows for the re-introduction of single carrier modulation waveform. For the first time, we present performance results obtained with real existing compact antennas and compact reconfigurable antennas, showing that the two new communication systems outperform conventional modulation in terms of energy efficiency and complexity.

A Method of Suppressing Higher Order Modes for Improving Radiation Performance of Metasurface Multiport Antennas Using Characteristic Mode Analysis

A method is proposed to suppress the unwanted higher order modes (HOMs) of the metasurfaces in multiport antenna systems for improving the radiation performances using characteristic mode analysis (CMA). The proposed method is to control the modal currents under consideration by loading the unit cells of the metasurface with slots and vias. The positions of loads are determined with the aid of CMA of the metasurface. For proof of concept, the proposed technique is applied to a compact wideband four metasurface antenna (MA) systems operating at 5 GHz Wi-Fi bands. With the suppression of HOMs, the split and tilted radiation patterns of the MAs are significantly improved. The concept is experimentally validated for potential compact multiport antenna applications.

On the Covariance Matrix and Diversity Performance Evaluation of Compact Multiport Antenna Systems

In this communication, we present a new electromagnetic methodology that determines the covariance matrix of compact multiport antenna (MPA) systems at the early design stage. Further insight into this field is provided, as contrary to existing methodologies, it rigorously relies on the reciprocity principle of MPA systems. Thus, the impact of propagation environment, termination conditions, and MPA radiation characteristics as independent factors affecting performance is physically incorporated. Provided the availability of mathematical expressions for the cumulative distribution function and probability density function of received signal-to-noise ratio (SNR), performance can then be analytically studied via the diversity antenna gain (DAG) in terms of: 1) SNR enhancement at a specific outage probability (OP) level (that is DAG-OP) and 2) average SNR reduction for achieving a specific average bit error rate (BER) (that is DAG-BER). Illustrative examples with performance evaluation of compact MPA systems are presented. The adopted diversity technique is the transmit antenna selection/maximal ratio combining, which is analytically studied employing realistic MPA systems for the first time. Comparisons with existing published results further demonstrate the validity and usefulness of the proposed methodology.

A Compact Triband Quad-Element MIMO Antenna Using SRR Ring for High Isolation

A compact multiband four port diversity-based antenna with high isolation between elements is proposed for multiple-input-multiple-output applications. The antenna resonates at following three bands: 1.95-2.5 GHz (covering UMTS, LTE 2300, and 2.4-GHz ISM bands), 3.15-3.85 GHz (covering WiMAX band), and 4.95-6.6 GHz (covering 5.2/5.8-GHz ISM bands). The stub-loaded meander-line antenna is loaded with split-ring resonators arranged in the form of a ring to enhance isolation by 17 dB at 2.4 GHz. All four elements radiate with equal efficiency with measured peak gains of 2.5, 3.7, and 4.4 dBi, respectively, in three bands and have a very low envelope correlation coefficient between elements. The overall size of the compact multiport antenna system is 0.26λ × 0.26λ × 0.01λ with a minimum isolation of 22 dB between its elements. The antenna elements and the isolation enhancement structure are fully planar for an easier integration.

Compact Multiport Antenna With Radiator-Sharing Approach and Its Performance Evaluation of Time Reversal in an Intra-Car Environment

A compact multiport antenna with three ports sharing one radiator is presented. The radiator is composed of two Sierpinski fractal triangles. This antenna contains two main ports and one auxiliary port. The two main ports have the same operating frequency band of 1–4 GHz. The auxiliary port with a multiband at around 2.4, 3.4, and 5.2 GHz provides an additional WLAN/WiMAX port. Since all the three ports share one radiator, the dimension of this antenna is only about ${0}.{21\lambda } \ast {0}.{15\lambda } \ast {0}.{01\lambda }$ , where ${\lambda }$ is the wavelength at the lowest operation frequency. Simulation results of time reversal (TR) propagation in an intra-car environment show that all the ports of the antenna have excellent TR focusing characteristic in each operation frequency band and the enhancement of the ratio of receiving signal amplitude to transmitting signal amplitude has been obtained. The radiator-sharing approach can be used to miniaturize the multiport antenna in TR time-domain communication systems.

Compact multiport antenna with isolated ports

AbstractThe small element spacing of compact multiport arrays introduces strong mutual coupling between the antenna ports. Because of this coupling, the input impedance of the array changes when elements excitations are varied, and consequently, the array cannot be matched for an arbitrary excitation. Decoupling networks have in the past been used to provide an additional connection between antenna ports to cancel the coupling between elements. An alternative approach is to design the antenna so that each port does not excite a single element, but instead all elements simultaneously. The geometry of the antenna is optimized so that this direct excitation of elements counteracts the mutual coupling, thus, yielding decoupled ports. This article describes the design of such a four‐port antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 229–232, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23038

High-temperature superconductor antennas: Utilization of low rf losses and of nonlinear effects

The low radio frequency (r.f.) losses in epitaxial HTS thin films allow the realization of novel antenna structures which have to be excluded in conventional antenna techniques with normal conductors because of the highly reduced radiation efficiency. Thus, the design of miniaturized but nevertheless highly efficient antennas down to a lower limit determined by both the required order of radiation pattern and the frequency bandwidth becomes possible. For a bandwidth of more than about 1%, a considerable margin for a size reduction below the “critical size” is restricted to the case of electrically small antennas and of superdirective antennas with a relatively low order of the radiation pattern, e.g. antennas with a beam of less than 15 dB maximum gain. If the size approaches the lower limit, the antennas show a sharp bandpass frequency response. This is demonstrated by means of experimental results for a novel HTS meander antenna. These bandpass characteristics can be utilized in compact multiport antenna systems in order to decouple subantennas for adjacent frequency bands. Besides the low losses in HTS's, their nonlinear properties can be used in order to realize current-controlled HTS switches for antenna systems.