Browsing by Author "Kormilainen, Riku"

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Decoupling and matching network for a MIMO handset antenna
(2018-08-20) Kormilainen, Riku
Sähkötekniikan korkeakoulu | Master's thesis
This thesis studies existing methods to derive decoupling and matching lumped element networks for antenna arrays. Based on the results, one method is used to design a decoupling and matching network for a 4x4 MIMO handset antenna. The complete antenna together with realistic lumped elements is simulated and, for the first time, realized in practice in a mobile phone antenna decoupling more than two antennas. The selected design for the decoupling and matching network is merely a starting point for the work. The network is reduced in order to manufacture it on a single layer PCB. Furthermore, several optimization steps are taken to derive the final values of the network elements. The MIMO array is designed at 2.6 GHz-2.7 GHz band and the measured total efficiencies vary between 32.6% and 62.5%. However, the efficiencies could potentially be 49.9%-62.7% according to the simulations. The difference is most likely due to excessive amount of solder for joining the components and other manufacturing defects. In simulations, decoupling and matching networks operate significantly better than conventional input matching networks. The difference varies from 5.7 percentage points to 16.5 points. These results demonstrate, that decoupling and matching networks are a potential choice, when strong mutual coupling is present in an antenna array. Furthermore, these networks provide an alternative approach to the issue of coupling.
Design and Optimization Methods for Multiport Antennas
(2022) Kormilainen, Riku
School of Electrical Engineering | Doctoral dissertation (article-based)
Modern wireless communications has evolved greatly within the past 30 years, and antennas are a significant part of the today's society. Almost everyone has a smartphone equipped with multiple antennas, and antennas are found in many everyday household objects and devices such as washing machines, coffee makers, and robotic vacuum cleaners. Furthermore, wearable antennas (such as those in medical devices, clothes, and watches) are becoming increasingly popular. In summary, antennas are placed in unconventional locations demanding new antenna design methods. Multiport antennas may provide benefits as compared to traditional single-port antennas. Therefore, this thesis discusses novel design methods for multiport antennas which requires new design methods. This thesis is divided into three part The first part studies using practical decoupling and matching networks (DMNs) in multiple-input-multiple-output (MIMO) antennas and antenna arrays. A DMN for a four-port MIMO antenna is realized with sufficient bandwidth, and a method is presented for optimizing a DMN of an antenna array with a commercial circuit synthesis tool by applying a unit cell model. The second part of the thesis discusses a method to optimize the radiation efficiency of a multiport antenna. The method provides an ultimate efficiency limit for a given multiport antenna in terms of its port characteristics. The developed method can be viewed as a design tool of sorts, and its practicality is demonstrated by designing a mobile MIMO antenna based on the results obtained with this method. The third part of the thesis focuses on extending the multiport antenna method discussed in the second part. The method is extended to optimize the partial radiation efficiency of multiport antennas and the realized gain of an antenna array comprising multiport elements. Although these methods are based on theoretical formulation, they enable a systematic way to realize practical multi-port antennas. The methods developed within this thesis provide a basis for developing multiport antennas. This hopefully advances the use of multiport antennas and enables the design of better and more complex antennas for future needs.
Discretized Antenna Concept
(2020-08-04) Viikari, Ville; Hannula, Jari-Matti; Kormilainen, Riku; Kutinlahti, Veli-Pekka; Lehtovuori, Anu; Luomaniemi, Rasmus; Saarinen, Tapio
A4 Artikkeli konferenssijulkaisussa
All electrical properties of an antenna are determined by its current distribution. It is possible to numerically solve a current distribution producing optimal performance in some sense. However, this ideal current distribution is nearly impossible to realize in practice. We propose the discretized antenna concept, which makes it possible to realize nearly optimal current distributions in practice. The method does not necessitate manual error and trial type iteration and it can be solved with many design goals. In this paper, we describe the design steps.
A Dual-Polarized Wideband Planar Multiport Mobile Antenna
(2022) Kormilainen, Riku; Luomaniemi, Rasmus; Lehtovuori, Anu; Khripkov, Alexander; Ilvonen, Janne; Viikari, Ville
A4 Artikkeli konferenssijulkaisussa
Additional antennas are needed in smart phones to support 5G bands. The metal rim, which is the most attractive position for antennas, is already fully occupied by antennas supporting legacy bands. Therefore, there is a growing interest in new, more challenging antenna locations, such as the back cover of the phone. In this paper, we introduce a dual-polarized frequency reconfigurable wideband planar multiport antenna to the back cover of a mobile phone. The antenna has a height of only 0.5 mm. The simulations show that the introduced antenna achieves better than-5.8 dB efficiency from 3.3 GHz to 4.2 GHz.
FF-signal-paneelin tutkiminen
(2021-05-12) Takkunen, Atte
Sähkötekniikan korkeakoulu | Bachelor's thesis
A Lumped-Element Decoupling and Matching Network for a Four-Element Mobile Handset MIMO Antenna
(2019-01-01) Kormilainen, Riku; Luomaniemi, Rasmus; Lehtovuori, Anu; Viikari, Ville
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This paper presents the first realization of a lumped-element decoupling and matching network (DMN) for more than two-element mobile MIMO arrays. The realization of the DMN is based on an existing method, which is improved in terms of bandwidth and the number of network elements. The array is designed to operate in the 2.6-2.7 GHz LTE band. The DMN is applied to a four-element MIMO antenna array located on one side of the mobile phone chassis. The array initially has a strong coupling of -3 dB, which is improved to -7 dB with the DMN. In other words, this denotes a reduction of 30 percentage points in coupled power. The DMN also improves the total efficiency by 21 percentage points at best.
A Method to Co-Design Antenna Element and Array Patterns
(2022) Kormilainen, Riku; Lehtovuori, Anu; Liesio, Juuso; Viikari, Ville
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this paper, we develop a novel method to design the elements of an antenna array and their feed weights simultaneously. The method is based on formulating the design problem as a non-linear multi-objective optimization model that estimates the realized gain at certain angles as a function of the element-level port signals and impedances, and the array-level weights for the elements. This enables utilization of genetic algorithms to find optimal signals, impedances, and weights for given steering range requirements. As an example, an array consisting of multi-port antenna elements is simulated and modeled with its impedance and radiation matrices. These matrices are used in the calculation of realized gain with the model. The model is then applied as part of the method to find as wide scanning range for the array as possible. The antenna elements are designed such that the multi-port system can be reduced to a single feed with physically realizable matching components and a matching network. The array designed with the proposed method is also compared to a reference antenna array of the same size. Both the simulations and measurements verify that the method can provide substantial improvements in the scanning range as compared to the reference.
Monisyöttöisen antennin optimointimenetelmän soveltaminen mikroliuskaantennin suunnittelussa
(2021-12-14) Helin, Anton
Sähkötekniikan korkeakoulu | Bachelor's thesis
Realizing Optimal Current Distributions for Radiation Efficiency in Practical Antennas
(2020-05) Kormilainen, Riku; Hannula, Jari Matti; Saarinen, Tapio O.; Lehtovuori, Anu; Viikari, Ville
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Modern antenna design is facing increasing issues with the radiation efficiency, since the space available for antennas is scarce and antennas are fitted into lossy environments. This letter presents a multiport antenna design method with a computationally efficient way to realize the port currents providing the highest radiation efficiency. In this method, an antenna is described with multiple excitation ports in electromagnetic simulations. The measurement results of an example design demonstrate the achieved benefit compared to traditional antenna design.
Robust On-Body Antenna Based on Discretized Planar Surfaces
(2023) Kormilainen, Riku; Langi, Konsta; Lehtovuori, Anu; Viikari, Ville
A4 Artikkeli konferenssijulkaisussa
This paper presents a novel on-body antenna consisting of discretized metallic patch elements connected with lumped components. The antenna is designed to on-body application, and it could be placed, e.g., to the sling of the backpack. Since most of the human body is composed of water, it has a significant effect on antenna performance. The main effects include detuning of the antenna and a deteriorating radiation efficiency. The proposed antenna inherently resists the detuning effects as compared to a conventional antenna. Therefore, the antenna provides a robust operation in various user scenarios. The details of the structure and element values are optimized with a readily available method that enables the optimization of lumped components to improve the total efficiency. The results show that a 400 MHz bandwidth can be achieved with reasonable efficiency.
Signaalin eheys digitaalielektroniikassa
(2015-12-20) Kormilainen, Riku
Sähkötekniikan korkeakoulu | Bachelor's thesis
Unbroken Metal Rim MIMO Antenna Utilizing Antenna Clusters
(2019-06-01) Luomaniemi, Rasmus; Hannula, Jari Matti; Kormilainen, Riku; Lehtovuori, Anu; Viikari, Ville
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This letter presents an antenna system for mobile devices with an unbroken metal rim. By utilizing the characteristic mode analysis for the unbroken metal rim, efficient multiple-input-multiple-output operation can be achieved. The design is based on an antenna cluster technique that uses several coupled elements that are used to efficiently excite the modes of the rim. Nonresonant antenna elements and matching networks are used to couple to the metal rim. The design has small ground clearance of 5 mm and height of only 4 mm, and can operate in wide bandwidths both in 700-960 MHz low band and 1.56-4 GHz high band. Measurement results confirm that competent performance is achieved.
User effect on antenna cluster based MIMO antenna
(2019-01-01) Luomaniemi, Rasmus; Hannula, Jari Matti; Kormilainen, Riku; Lehtovuori, Anu; Viikari, Ville
A4 Artikkeli konferenssijulkaisussa
This paper studies the benefits of the antenna cluster technique in exciting the orthogonal modes of a metal rim for MIMO operation in the low-band frequencies. The user effect with antenna clusters is studied with measurements of antenna prototype held by a hand phantom. On average, better than 20% total efficiency is achieved over the low-band frequencies and almost 30% average efficiency over the higher frequencies which suggests that the antenna cluster technique can be used to design user effective mobile device antennas.