Papers by Per-Simon Kildal
2009 International Conference on Electromagnetics in Advanced Applications, 2009
The Eleven feed is a log-periodic array of parallel dipoles in Eleven (II) configuration. It exhi... more The Eleven feed is a log-periodic array of parallel dipoles in Eleven (II) configuration. It exhibits constant beam width and phase center position over a decade bandwidth, and finds therefore application as a wideband feed for reflector antennas. The present paper gives a summary of the present performance of a 2-14 GHz Eleven feed that is under development for use as a feed for VLBI 2010 radio telescopes for geodesy. Previous reported Eleven feeds did not reach that high in frequency. The intention is also to develop a feed that can be integrated with a low noise amplifier inside a cryostat at temperature of 14 K, and receive the waves focused by the primary reflector through an RF window in the cryostatic cavity. Thereby the lowest system noise temperature is ensured. The present model has successfully survived cooling to 14 K.
IEEE Transactions on Components, Packaging, and Manufacturing Technology
After the use of the bed of nails for removing cavity modes in microstrip circuit packages, we pr... more After the use of the bed of nails for removing cavity modes in microstrip circuit packages, we propose herein a new version of this periodic structure, based on helices (springs) instead of nails. This new structure, named bed of springs, is much more compact, and this allows its use at low frequencies where the bed of nails is not suitable as it is too bulky due to the required height of the nails (pins). The bandwidth of the proposed structure turns out to be similar to the case of bed of nails. Parametric studies are presented as a design tool and a demonstrator is manufactured and measured.
2006 First European Conference on Antennas and Propagation, 2006
The Eleven antenna is a novel dual polarized ultra wide band (UWB) feed with a decade bandwidth f... more The Eleven antenna is a novel dual polarized ultra wide band (UWB) feed with a decade bandwidth for use in both single and dual reflector antennas. The special name is associated with its basic 11 iquest configuration of two parallel dipoles with 0.5 wavelengths spacing, and because it can be used over more than a decade bandwidth (and 11 >
Proceedings of IEEE Antennas and Propagation Society International Symposium, 1993
ABSTRACT A technique to reduce scattering from gaps between reflecting panels by using the concep... more ABSTRACT A technique to reduce scattering from gaps between reflecting panels by using the concept of soft surfaces is described, as well as a computer program to analyze it. The computer program has been developed for the analysis of a two-dimensional gap in an infinitely large and perfectly conducting ground plane. The edges of the ground plane can be provided with an arbitrary number of corrugations inside the gap, with arbitrary rectangular shapes. This computer code is used to analyze different geometries in order to look for increased bandwidth. The program has been used to construct corrugations of different depth that reduce the transmission through a gap over a bandwidth of 4:1
Microwave and Optical Technology Letters
A simple method for computing the crosstalk between parallel conductors on printed circuit boards... more A simple method for computing the crosstalk between parallel conductors on printed circuit boards is presented. The crosstalk is computed by using a lumped-circuit element model for the conductors, where the per unit-length parameters are computed by a finite-difference scheme. The method is applied to analyse several examples showing how crosstalk on circuit boards can be reduced. The results are verified by comparison with previously published results and measurements
In an isotropic rich scattering environment, the shape of the patterns of the elements has long b... more In an isotropic rich scattering environment, the shape of the patterns of the elements has long been considered as irrelevant to their Multiple-Input and Multiple-Output (MIMO) performances. In the current communication it is cleared that the directivities of the embedded elements, which are immediate outcomes of their patterns, contribute to the diversity gains as well as capacity of the system. Indeed, the number of scatterers plays a significant role in this respect. It is demonstrated that unless the number of scatterers is high enough, the diversity gain and capacity do not reach their final limits, even though the spatial correlation and radiation efficiencies reside on their ideally best levels. A brief study of the matter is presented in this paper and the simulation results are verified by measurements in reverberation chamber.
Applied Computational Electromagnetics Society Journal
A user-friendly computer code, PCB-MoM, that is intended to be used in EMC applications for predi... more A user-friendly computer code, PCB-MoM, that is intended to be used in EMC applications for predicting radiated emission and susceptibility of printed circuit boards (PCB) is presented. The formulation is based on an electric field integral equation (EFIE) expressed in the frequency domain. The EFIE is solved by the method of moments using two-dimensional pulse basis functions and one-dimensional pulse test functions. In order to incorporate dielectric material in the substrate a spectral domain formulation is used. The code has been validated by comparison with previously published results and results obtained by other methods and codes
An independent implementation of a part of the Winner II channel models is compared with the isot... more An independent implementation of a part of the Winner II channel models is compared with the isotropic propagation environment. Convergence of diversity gain and capacity to their ergodic values is presented for a terminal with two antennas using embedded element far-field functions. I. INTRODUCTION Mobile terminals communicate wirelessly with a base station over a propagation channel. Through the channel there is usually not only a line-of-sight (LOS) component, but several scattered waves which vary stochastically with time. This gives rise to fading which may result in dropped connections or low throughput for the user. Techniques such as diversity and multiple-input multiple-output (MIMO) may be used to mitigate fading and increase throughput. In order to study these techniques and to be able to evaluate terminals under representative channel conditions, it is important to have an understanding of the fading channel.
Spatial correlations of incremental electric and magnetic currents, and Huygen's sources with... more Spatial correlations of incremental electric and magnetic currents, and Huygen's sources with different arrangements (parallel and collinear) are studied in this paper; showing computed results as well as some analytical closed-form expression. It is found that the correlation depends both on the isolated far field function and the arrangements, and of course the spacing. These correlations are compared with that of two imaginary isotropic source with the same spacing. It is found that two Huygen's sources for certain arrangements have a spatial correlation that is almost the same as that of two isotropic sources. Spatial correlation of an electrically small monopole is also measured in a reverberation chamber to verify some results.
The main concern of the current communication is to elicit the influences of beam-forming upon di... more The main concern of the current communication is to elicit the influences of beam-forming upon different multiple-input multiple-output (MIMO) parameters in a rich scattering environment. A detailed study of desired parameters is presented with particular stress on total radiation efficiencies observed on element ports and beam ports. Measurements are performed in a reverberation chamber (RC). The results illustrate that performance as viewed through element and beam ports are, in general, equal. Hence, they confirm that in a rich and isotropic scattering environment, beam-forming technique does not prove beneficial. They also demonstrate that as long as received radiation power is preserved, the shapes of the elements' patterns are irrelevant.
The paper studies the over-the-air (OTA) performance of a mobile terminal. A practical two-port m... more The paper studies the over-the-air (OTA) performance of a mobile terminal. A practical two-port mobile terminal model on the left side and the right side of the head for both standard cheek position and standard tilt position is used to study the diversity gains. The diversity gain has been determined by measurements in a reverberation chamber as well as by simulations using the far field patterns from CST Microwave Studio, and then exposing these patterns to rich isotropic multipath (RIMP) environment in a ray-based simulation tool.
Statistical uncertainties involved in the evaluation of ergodic MIMO capacity and diversity gain ... more Statistical uncertainties involved in the evaluation of ergodic MIMO capacity and diversity gain in a fading environment is investigated. The study is based on results from a numerical simulation tool called “Rayleigh-Lab.” This tool can be used for accuracy investigation of MIMO capacity and diversity gain, and to determine the number of independent samples needed to estimate them with a reasonable level of confidence. The MIMO capacity is evaluated using Shannon's channel capacity formula. Two different methods of evaluating diversity gains are compared: based on CDF curves, and based on estimating correlation and radiation efficiency and then using them in a newly available compact formula for calculating the diversity gain. Rayleigh-Lab emulates Rayleigh channels by generating sequences of random complex numbers and it provides a convenient graphical user-interface for a pedagogical study of average power level (proportional to antenna efficiency), correlation, diversity gai...
We propose that the rich isotropic multipath environment should be a reference environment for OT... more We propose that the rich isotropic multipath environment should be a reference environment for OTA (over-the-air) characterization of wireless stations for use in multipath, in the same way as the anechoic environment is a reference environment for antennas mounted on masts and rooftops. The rich isotropic multipath environment is emulated by a well designed reverberation chamber, but also by a spherical array of probes in an anechoic chamber. The present paper describes a ray-based simulation tool, ViRM-Lab, which enables users to study the performance of arbitrary user-defined multiport antenna located in user-specified multipath environment. The antennas are defined by their far-field functions of the embedded element (with the other ports matched-load terminated). The environment can be determined by its Angle-of-Arrival (AoA) distribution, richness, and polarization balance. The code is made in such a way that the convergence of the cumulative distribution function (CDF) receiv...
Doppler spread has been observed in reverberation chambers (RC) with moving mode-stirrers. In thi... more Doppler spread has been observed in reverberation chambers (RC) with moving mode-stirrers. In this paper, we propose a simple method to determine the maximum Doppler frequency shift in the RC by using level crossing rate (LCR). The Doppler spread bandwidth is twice of the maximum Doppler frequency. RC loading effect on Doppler spread is also studied in this paper. Using the method, it is found that maximum Doppler spread bandwidth tends to reduce when lossy objects are located into the RC, and the larger reduction the more larger lossy objects.
The performance of multiport antenna systems located in multipath environment is characterized by... more The performance of multiport antenna systems located in multipath environment is characterized by their ergodic capacity and diversity gain. The impact on convergence and statistical uncertainties involved in the estimation and evaluation of these performance metrics is studied for different port weights (i.e. different embedded element efficiencies) and correlations. The study is performed by using an upgraded version of the multipath simulation tool Rayleigh Lab which emphasizes the presentation of the statistical characteristics on the ports rather than the electromagnetic modelling. Therefore, the Rayleigh fading channels are generated in a very simple way by using arrays of randomly distributed complex numbers, and the user can input efficiencies and correlations rather than farfield functions and mutual couplings.
In this paper, we compare different methods to determine correlation. First, we did analytical st... more In this paper, we compare different methods to determine correlation. First, we did analytical study on correlation of two parallel dipoles. We present two methods for analytical correlation calculation. In addition, the effect of source impedances is also studied. It is found that these two analytical methods result in the same correlation, and that source impedance matched to embedded element impedance gives the smallest correlation. Then, we compared different methods of determining correlations of multi-port antennas from measurements. Wideband eleven antenna was used for measurements. It is shown that correlation can be determined correctly either using embedded radiation far field functions based on anechoic chamber (AC) measurement (i.e., embedded far field method), or using cross-correlation definition based on reverberation chamber (RC) measurement (i.e., RC method). Scattering parameters (S-parameter) can only be used to determine correlation of lossless multi-port antenna...
The paper discusses the need for a reference environment for the characterization of small antenn... more The paper discusses the need for a reference environment for the characterization of small antennas intended to be used in multipath. The conclusion is that a good choice is the rich isotropic multipath environment as emulated by a well designed reverberation chamber, or possibly by a spherical array of antennas in an anechoic chamber. This is the only environment that enables a unique, objective and repeatable antenna characterization. This cannot be achieved in other environments. A few examples are given showing that the performances of different incremental antennas are very different and depend strongly on their orientations when they are located in a 2D horizontal multipath environment, with incident waves only in the horizontal plane, whereas their performances are equal and invariant to orientation when they are located in the rich isotropic multipath environment.
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Papers by Per-Simon Kildal