Multiport Antenna Research Articles

Effects of coupling and overspeeding on performance of predictor antenna systems in wireless moving relays

Using predictor antenna systems for modern wireless moving relays and base stations on top of vehicles such as buses, trains etc. proves to be a reliable approach for collecting channel state information to such fast moving nodes. Recently, it has been shown that coupling between different ports of a multiport antenna system used as a part of a predictor system can reduce the prediction performance. In this study, by integrating position and velocity vectors in the channel covariance matrix as seen at the antenna ports in a rich multipath environment, the authors quantify the impact of antenna coupling on prediction performance. Moreover, practically these predictor systems are designed for a certain target velocity. They further quantify the adverse effect of velocities, different from the target velocity, on prediction performance. In case open-circuit decoupling is necessary, the sensitivity of the predictor antenna system performance with respect to the accuracy of the input network parameters is disclosed.

Energy-Based Representation of Multiport Circuits and Antennas Suitable for Near- and Far-Field Syntheses

An energy-based representation suitable for the electromagnetic characterization of linear multiport circuits and antenna systems, as well as for the optimization of antenna beamforming and near-field radio frequency-focusing performances, is presented. Radiation, ohmic, dielectric power loss, and reactive power storage are described in the concise matrix form, yielding respective eigenmodes and eigenfields that rigorously account for all energetic processes. Noteworthy eigenfields orthogonality properties are illustrated and employed to maximize (minimize) active power flow through, or to synthesize fields on, arbitrary surfaces. Applications of the proposed formulation include multiport antennas, microwave-sensing devices, microwave hyperthermia applicators, through-the-wall imaging, and wireless power transfer systems. The numerical results illustrate features and performance advantages of the proposed formulation as applied to multiport antennas and lead to define some basic design guidelines.

Near Field Synthesis Based on Multi-Port Antenna Radiation Matrix Eigenfields

The attainable performances of a general formulation employing radiation matrix eigenfields of multi-port antennas to synthesize near-field distributions are investigated. Field synthesis performed on open or closed surfaces, proximate to or enclosing an antenna array, either based on both electric and magnetic target field distributions or just the former, are presented to illustrate the key features of the synthesis technique and its sensitivity with respect to realistic random magnitude and phase variations of the array excitation profiles. Guidelines to perform synthesis and the steering of the complex near-field distributions are then suggested. The propagation characteristics of diffraction-resistant Bessel, OAM Bessel, and Airy beams in their actual finite-energy implementation, when they are excited by finite-size antenna arrays are finally investigated.

Grid-Array Rectenna With Wide Angle Coverage for Effectively Harvesting RF Energy of Low Power Density

It is difficult to effectively rectify or convert low power in the circuit stage of harvesters. The high-gain antenna can offer a higher level of power and is beneficial to RF power harvesting in a low power density environment. To extend the narrow beam of the conventional high-gain rectenna, the multiport and multibeam antenna is promising. To pursue a simple configuration and avoid extra beamforming networks, a traveling-wave grid-array antenna (GAA) with two isolated ports and two symmetrically tilted beams is proposed. A prototype is designed and fabricated after a detailed analysis of the GAA with tilted beams and the coplanar stripline-based rectifier. The measured results show that the proposed rectenna is sensitive and effective in a wide-angle range. The harvesting angle range is extended by combining two tilted beams and can be greater than 70°, where the level of dc power exceeds $100~\mu \text{W}$ when the power density is as low as $1~\mu \text{W}$ /cm2. A maximum dc output of 3.6– $203.8~\mu \text{W}$ and a maximum RF-to-dc conversion efficiency of 16.3%–45.3% are available at 2.45 GHz, under the condition that the power density ranges from 0.052 to $1~\mu \text{W}$ /cm2.

On a silver platter

on a silver platter

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 CPW-fed UWB MIMO antenna with integrated GSM band and dual band notches

This article presents a coplanar waveguide fed global system for mobile communications band integrated ultra wide band (UWB) multiple input multiple output (MIMO) antenna with single and dual notch band characteristics. The novelty of the antenna lies in its design as all the unit cells of the proposed UWB MIMO antenna structure are orthogonal to each other therefore the additional isolation elements responsible for achieving high isolation are not required consequently making proposed antenna design simple and easy to fabricate. In this context, 2 MIMO systems have been designed. The first MIMO system is consisting of a dual port antenna whereas the second MIMO system is a printed quad port antenna; further single and dual notch band are achieved in the proposed multi-port MIMO antenna. The antenna shows pattern diversity throughout the impedance bandwidth range. The gain of the antenna varies from 4 to 8.48 dBi. The 2 band notches are achieved at 4.8 and 7.7 GHz in the UWB range. The proposed antenna is fabricated and it is found measured results are in good agreement with simulated results.

Packaging and Integration Strategy for mm-Wave Products

Abstract This paper is a follow on to the paper presented at the IMAPS 14th International Conference DEVICE PACKAGING and will provide more comprehensive case studies of few different system integration strategies for high frequency packaging. The packaging options vary widely based on the end market requirements, from performance, thermal, types and numbers of antenna arrays as well as the RF transceiver ICs. Tied closely to these performance related requirements is competing trade-offs of reliability, form factor and cost. We present assessment of packaging structures for (a) high performance mm-Wave network product and (b) consumer/mobile product and (c) automotive radar product. The former (a) is generally not challenged by form factor and can be enhanced by the addition of more antenna arrays and RFICs. However, care has to be taken to address the thermal solutions for effective heat dissipation as well as manufacturability issues as the package size may target ~400mm2 for Gen 1 and double or triple the area for subsequent generations. For (b), the primary drivers are cost and form factor. To manage antenna propagation and losses in a constrained form factor, mobile products generally require antenna in package (AiP) integration. The integration of the antenna within the same package as the RF IC greatly reduces the difficulty at the system level. This approach coupled to aggressive miniaturization of the antenna itself, using the same substrate technologies as the SiP leads to a new class of sub-systems termed Antenna in Package (AiP). This is extremely challenging from design, manufacturability and test perspectives. For example, Fan out wafer level packaging, such as eWLB packaging provides extremely smooth copper surfaces with tight etch tolerance compared to standard laminate based packaging. However, having multiport antenna structures fabricated in fan out technology with inductance matching and efficient ground ports, continue to be problematic. Hence adoption of 3D structures, in conjunction with SIP integration (with inductors and IPDs) can potentially provide relief. Inductors can also be built into the eWLB structure using the RDL as well as in the laminate packages using substrate embedded thin film cores.

Mutual Coupling Reduction of Rotationally Symmetric Multiport Antennas

A systematic method for reducing the mutual coupling of a rotationally symmetric multiport antenna system is proposed. A compact design example for a four-port antenna with low mutual coupling across two frequency bands centered around 2.4 and 5.8 GHz is provided. The entire size of the proposed four-port antenna is $0.28\lambda _{o}\times 0.28\lambda _{o}\times 0.04\lambda _{o}$ , where $\lambda _{o}$ is the wavelength in free space, and it is compact enough for the use in smartwatch applications for example. The defected ground structure and slot-lines used in the design are also modeled with an equivalent circuit to explain the achieved high port isolation. A prototype is fabricated and tested to confirm the results of the electromagnetic simulation. Furthermore, the proposed design method can be applied to five-port and three-port antenna systems in rotationally symmetric geometries for suppressing mutual coupling between ports.

Design and Optimization of Multiport Pixel Antennas

We describe a method for the design and optimization of multiport pixel antennas for application in multiple-input multiple-output (MIMO) communication systems. A rectangular grid of pixels with connections between them is used as a design surface for multiport antenna design. Genetic algorithm optimization is used to find the optimal configuration of connections between pixels and multiple input port locations under the constraints of high isolation between all ports and good impedance matching for all ports over the desired frequency band and/or beam direction. The method utilizes a scalar single-objective function that takes account of return loss, isolation between ports, and antenna gain, and makes use of the internal multiport method. Examples of MIMO antenna optimization for a 2-port MIMO dual-band antenna operating at 2.4 and 5 GHz without pattern optimization and an example for a 2-port MIMO single-band antenna operating at 5 GHz with pattern optimization (forming orthogonal endfire main beams) are provided.

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.

A Beamforming Approach for Multiport Antennas [Antenna Applications Corner

This article presents an approach for the systematic construction of a unitary multibeam transformation for a general multiport antenna. The resulting beamforming transformation produces up to N beams for an antenna with N terminal pairs. The beams are formed sequentially, each with maximum realized gain for the available degrees of freedom (DFs). The construction may be used for sidelobe control by sequentially placing nulls in the pattern, with each null requiring minimal additional incident power. The procedure provides insight into the effects of null placement on array efficiency and gain pattern. The average element pattern is invariant to unitary transformations of the incident waves, and this fact is used to derive a closed-form expression for the multiple signal classification (MUSIC) function PMU(Ω) for the case of two closely separated emitters symmetrically located about the broadside direction of an array of N ideal noninteracting elements with half-wavelength spacing.

Systematic Design of a Multiport MIMO Antenna With Bilateral Symmetry Based on Characteristic Mode Analysis

There are various bilaterally symmetric structures in the world. Characteristic mode analysis (CMA) enables to use a conductor with the symmetric structure itself as an antenna. Based on CMA, it is possible to implement a multiport MIMO antenna on the conductor using a mode-decoupling network (MDN). As the number of antennas increases, however, the complexity of the MDN becomes large, making design difficult. In this paper, we propose a simpler systematic design method for a multiport MIMO antenna on an electrically small and bilaterally symmetric conductor. More specifically, the implementation of the MDN depends on the design of the coupling elements that excite characteristic modes, so a design method for its position and shape is proposed. Owing to the well-designed coupling elements, a simple systematic design of the multiport MIMO antenna is suggested. The proposed design method is verified by simulation and measurement of a bug-like 3-port MIMO antenna operating in the 2.4 GHz ISM band, applicable to biomimetic drones. The antenna is realized using an FR-4 substrate with dimensions of 50 mm $\times \,\, 61.5$ mm $\times \,\, 10$ mm ( $0.4\lambda _{0} \times 0.49\lambda _{0} \times 0.08\lambda _{0} $ at 2.4 GHz). The measurements demonstrate that these antennas have a low mutual coupling (<−20 dB) and a low envelope correlation coefficient (<0.04).

Multi-port Pattern diversity antenna for K and Ka-band application

A compact coplanar waveguide (CPW) fed reconfigurable antenna with pattern diversity using multi-port excitation is designed. The basic antenna consists of a circular patch of radius 2.5mm which is fed by four ports independently. By exciting the patch with each individual port, the direction of the radiation pattern changes by 900. With the use of CPW feed technique, a very wide impedance bandwidth of around 12GHz (21.65 – 33.87 GHz) covering the K-band and Ka-band is achieved. The proposed antenna can be used for different satellite communication applications like earth exploration, radio navigation and location, mobile satellite communications which comes under K-band and Ka-band. The measured return loss and pattern characteristic results are in good agreement with simulated ones.

Multi-Port Patch Antennas for Flexible Power Combining and Feeding Choice

Patch antennas with multiple feeds are proposed in this paper. The antennas consist of a traditional square patch and feeding probes that are set in a line orthogonal to the polarization direction. In addition to radiating EM energy just like the conventional antennas, the proposed multi-port antennas can also realize on-antenna power combining without power combiner. Thanks to this, high-line losses and large system size caused by extra power combiner can be avoided. Moreover, since the location and the number of ports have a limited effect on the antenna performances, flexible feeding strategies can be chosen in different applications. For demonstration, four patch antennas with a different number of ports (one port, two ports, three ports, and four ports) are designed at the center frequency of 1.5 GHz. Compared with the traditional one-port patch antenna, the proposed three multi-port patch antennas can achieve nearly the same antenna performance, including bandwidth, polarization, efficiency, and radiation pattern. Besides, one-port antenna and two-port antenna integrated with a two-way power amplifier are designed and measured, respectively. Then, they are compared to further prove the proposed power combining method in multi-port antennas.

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.

Optimized Manipulation of the Network Characteristic Modes for Wideband Small Antenna Matching

Multiport antenna systems can be regarded as $N$ -port networks, which can be analyzed using the theory of network characteristic modes (NCMs). Due to the profound physical insights provided by an NCM, a desired antenna performance can be achieved by properly manipulating the modes through reactive loading at specified ports. This paper presents a new matching technique for an $N$ -port internally loaded small antenna. By combining the NCM with the differential evolution algorithm, optimal reactive load values can be calculated. These loads can manipulate the NCMs to match the antenna in a desired bandwidth. Unlike other matching techniques based on the NCM, the desired bandwidth is achieved through internal reactive loading without the need for an input matching network. Two examples of electrically small monopole antennas are studies. In both examples, we study the possibility to match the antennas in the GSM 900 band, and we further investigate the possibility to achieve wider bandwidths by varying the number of ports and the loading topologies based on the interpretation of the characteristic modes. The loaded antennas are wideband with a relatively stable radiation pattern and an efficiency higher than 90%. To confirm the theoretical results, a prototype is fabricated and measured.

Multiport MIMO antennas with mutual coupling reduction techniques for modern wireless transreceive operations: A review

The present technology fulfills the requirement of high data rate and high channel capacity using multiple input multiple output (MIMO) technology. The MIMO capacity of the system is increased linearly but due to the multiple antennas placed near to each other, problem of mutual coupling exists, which degrades the maximum achievable performance of the system. The problems of multipath propagation can be solved using MIMO system. The isolation improvement methods decrease the mutual coupling among antenna elements, and improve the gain and efficiency of the system. In this paper, decoupling network isolation approach, parasitic element approach, defected ground structure, Neutralization line, isolation improvement based on metamaterials, isolation improvement using PIN diode, varactor diode, and feeding structure have been incorporated, and their merits and demerits have been discussed. The effect of different permittivity material on antenna parameters has also included.

Ultrawideband In-Ground Multiport Antenna for Small Cell Applications

In this paper, a four-port ultrawideband antenna design is proposed. The antenna is suitable for installation in pavements. The main application of this antenna is in the reuse of the existing manholes for radio equipment and antenna installation. Equally important is its application in dense network deployment as a result of its capability to alleviate intercell interference. The antenna can support up to $4\times 4$ multiple-input and multiple-output (MIMO) systems. The isolation between different ports exceed 28 dB over the commercial long term evolution bands 3 and 7. The multiport matching bandwidth of the antenna (>-0.3 dB) extends over 1700–3000 MHz range. The antenna is mechanically robust and can withstand a weight of 40 ton. MIMO performance of this antenna is verified by virtue of field measurements. A comparative study between the proposed antenna and a classic half-wavelength dipole antenna is presented highlighting the advantages of the proposed antenna. Finally, its compliance with the exposure limits for nonionizing radiation is also demonstrated.

Planar Triorthogonal Diversity Slot Antenna

This communication proposes an easily manufacturable multifunction multiport planar slot antenna with triorthogonal pattern diversity. Distinct radiation patterns are emitted via a common square radiative slot by exploiting three orthogonal modes. These slot modes consist of a magnetic current loop mode with an omnidirectional linearly polarized (OLP) radiation pattern, and two degenerated linear slot modes radiating broadside with orthogonal linear polarizations (LPs). The triorthogonal patterns are obtained in an overlapping frequency band, and the mutual coupling between the ports is minimized through a differential feeding arrangement. This new concept of multiport diversity slot antenna is validated experimentally at a frequency of 5.9 GHz, successfully demonstrating the operation modalities of OLP and LP radiation patterns. A minimum triorthogonal overlapping impedance bandwidth of 2.3% is measured with interport coupling below −35 dB. The proposed antenna could be used as a pattern and polarization diversity antenna, where additionally, a linear combination of the primary triorthogonal patterns can be exploited to further enhance flexibility in pattern generation.