1. 
 Helander, Jakob, et al.
(författare)

Performance Analysis of MillimeterWave Phased Array Antennas in Cellular Handsets
 2016

Ingår i: IEEE Antennas and Wireless Propagation Letters.  15361225. ; 15, s. 504507

Tidskriftsartikel (refereegranskat)abstract
 This letter discusses the usage of highgain steerable antenna arrays operating at millimeterwave (mmWave) frequencies for future cellular networks (5G). Based on the probable outline of the 5G networks, a method for characterizing phased array antennas in cellular handsets has been introduced. For analyzing the performance, the total scan pattern of the array configuration together with its respective coverage efficiency are essential to consider in order to compare different antenna designs and topology approaches with each other. Two design approaches and subarray schemes of these have been considered in order to illustrate the relevance of such a characterization method. The results show the importance of evaluating potential array antennas in such manners. The method can be applied to much more complex system models, where polarization diversity, hand and body effect, and statistical modeling of the channel may be included.


2. 
 Ramprecht, Jörgen, et al.
(författare)

Biased magnetic materials in RAM applications
 2007

Ingår i: Progress in Electromagnetics Research.  15598985. ; 75, s. 85117

Tidskriftsartikel (refereegranskat)abstract
 The magnetization of a ferro or ferrimagnetic material has been modeled with the LandauLifshitzGilbert (LLG) equation. In this model demagnetization effects are included. By applying a linearized small signal model of the LLG equation, it was found that the material can be described by an effective permeability and with the aid of a static external biasing field, the material can be switched between a Lorentzlike material and a material that exhibits a magnetic conductivity. Furthermore, the reflection coefficient for normally impinging waves on a PEC covered with a ferro/ferrimagnetic material, biased in the normal direction, is calculated. When the material is switched into the resonance mode, two distinct resonance frequencies in the reflection coefficient were found, one associated with the precession frequency of the magnetization and the other associated with the thickness of the layer. The former of these resonance frequencies can be controlled by the bias field and for a bias field strength close to the saturation magnetization, where the material starts to exhibit a magnetic conductivity, low reflection ( around  20 dB) for a quite large bandwidth ( more than two decades) can be achieved.


3. 
 Ramprecht, Jörgen, et al.
(författare)

Magnetic Losses in Composite Materials
 2008

Ingår i: Journal of Physics D : Applied Physics.  00223727. ; 41:13, s. 135005

Tidskriftsartikel (refereegranskat)abstract
 We discuss some of the problems involved in homogenization of a composite material built from ferromagnetic inclusions in a nonmagnetic background material. The small signal permeability for a ferromagnetic spherical particle is combined with a homogenization formula to give an effective permeability for the composite material. The composite material inherits the gyrotropic structure and resonant behaviour of the single particle. The resonance frequency of the composite material is found to be independent of the volume fraction, unlike dielectric composite materials. The magnetic losses are described by a magnetic conductivity which can be made independent of frequency and proportional to the volume fraction by choosing a certain bias. Finally, some concerns regarding particles of small size, i.e. nanoparticles, are treated and the possibility of exciting exchange modes are discussed. These exchange modes may be an interesting way to increase losses in composite materials.


4. 
 Ramprecht, Jörgen, et al.
(författare)

Scattering from a thin magnetic layer with a periodic lateral magnetization application to electromagnetic absorbers
 2008

Ingår i: Progress in Electromagnetics Research.  15598985. ; 83, s. 199224

Tidskriftsartikel (refereegranskat)abstract
 A magnetized thin layer mounted on a PEC surface is considered as an alternative for an absorbing layer. The magnetic material is modeled with the LandauLifshitzGilbert equation, with a lateral static magnetization having a periodic variation along one lateral direction. The scattering problem is solved by means of an expansion into Floquetmodes, a propagator formalism and wavesplitting. Numerical results are presented, and for parameter values close to the typical values for ferro or ferrimagnetic media, reflection coefficients below 20 dB can be achieved for the fundamental mode over the frequency range 14 GHz, for both polarizations. It is found that the periodicity of the medium makes the reflection properties for the fundamental mode almost independent of the azimuthal direction of incidence, for both normally and obliquely incident waves.


5. 
 Xu, Bo, et al.
(författare)

Investigation of planar nearfield measurement of millimeterwave antenna for 5G application
 2017

Ingår i: ISAP 2016  International Symposium on Antennas and Propagation.  Institute of Electrical and Electronics Engineers Inc.. ; s. 600601

Konferensbidrag (refereegranskat)abstract
 The requirement of higher data rates and the emergence of new wireless device demands in future 5G communication put millimeterwave frequencies in focus. To investigate electromagneticfiled exposure at such frequencies for 5G cellular phone application, a planar nearfield antenna measurement system is established. A tapered openended rectangular waveguide was used as the probe antenna, and a patch array antenna operating at 28 GHz was used as antenna under test. The distribution of power density above the antenna surface was calculated based on the measured data and the plane wave expansion method.


6. 
 Zhao, Kun, et al.
(författare)

User Body Effect on Phased Array in User Equipment for the 5G mmWave Communication System
 2017

Ingår i: IEEE Antennas and Wireless Propagation Letters.  IEEEInstitute of Electrical and Electronics Engineers Inc..  15361225. ; 16, s. 864867

Tidskriftsartikel (refereegranskat)abstract
 The millimeterwave phased array in the user equipment (UE) for 5G communication is studied in this letter. In particular, the body effect on the phased array in the UE at 15 GHz is investigated with the 3D measurement data, and its impact on some key parameters for phased array in the UE, such as the total scan pattern, the coverage efficiency, and the probability of detection, are analyzed.

