Kristian Karlsson

Reverberation Chamber for Antenna Measurements: Modeling Using Method of Moments, Spectral Domain Techniques, and Asymptote Extraction

Large reverberation chambers (RCs) have proved to be useful for measuring the performance of small antennas and terminals for wireless communications, and it is therefore important to be able to model them numerically to control accuracy. This paper describes a method of moments approach for analyzing wire antennas and other metallic objects in a large RC. The RC is treated as a rectangular perfect electric conducting cavity, and the Greens function is constructed by using a spectrum of plane waves and imaging combined with periodic boundary conditions. The code has been validated by comparison with measurements and other computer codes

Doppler Spread in Reverberation Chamber Predicted From Measurements During Step-Wise Stationary Stirring

We propose a simple method to accurately predict Doppler spread in a reverberation chamber (RC) by using frequency domain S-parameters measured with a vector network analyzer (VNA) at many fixed stirrer positions (step-wise stationary mode). Thus, the measurements are done under repeatable stationary conditions, so no Doppler shift is present during the actual measurements. Still, this letter shows that the measured S-parameters in step-wise stationary mode can be used to determine Doppler spread appearing during continuous movement of the stirrers. This can be done by computation for any stirrer speed by assuming that the fixed stirrer position steps are the time steps of a continuous movement of the stirrers, and by adding a virtual stirrer speed between the positions corresponding to the desired continuous movement of the stirrers. The computed Doppler spreads are validated over a large frequency band by measuring the time-varying S-parameters for a given stirrer speed.

Field Measurements of IEEE 802.11p Communication in NLOS Environments for a Platooning Application

This paper presents results from field measurements on a vehicle-to-vehicle communication system based on IEEE 802.11p. During the measurements the vehicles were moving and there were also moving obstacles located between the transmitting and receiving nodes creating a Non-Line-of-Sight environment. Distance, speed and type of obstacles were varied during the measurements. Both a highway and suburban environment was tested. The tests were focused on packet error rate and consecutive packet loss. The results of the measurements are compared with the communication requirements of a vehicle platooning application which is a novel intelligent transport system application. It implies multiple vehicles tightly following each other in a row. Performance of the application degrades with consecutive packet loss. It is shown that the platooning application is not adequately supported in all measurement scenarios.

Designing reverberation chambers for measurements of small antennas and wireless terminals: Accuracy, frequency resolution, lowest frequency of operation, loading and shielding of chamber

The last five years the reverberation chamber has been developed to an accurate instrument for measuring the performance of small antennas and active mobile terminals in Rayleigh fading. The present paper gives an overview of the research done by the authors in relation to achieving an accuracy of 0.5 dB RMS or better, when measuring efficiency and radiated power. The accuracy has been verified by comparison with measurements in anechoic chambers, and between reverberation chambers of different size, and from participation in benchmarking of measurement ranges done within ACE (Antenna Center of Excellence, a European Network of Excellence). There have also been developed procedures for measuring quantities that are specific for the Rayleigh environment, such as diversity gain, MIMO capacity, and static as well as dynamic receiver sensitivity at certain data error rate (BER or FER). The paper will describe important topics related to the mode stirring and loading of the chamber, such as the accuracy, frequency resolution, average transfer function, and the system bandwidth when measuring active terminals. Numerical simulations play an important role in controlling the chamber performance.

On OTA Test in the Presence of Doppler Spreads in a Reverberation Chamber

In this letter, over-the-air (OTA) tests of the performance of the IEEE 802.11p radio system are performed in a reverberation chamber (RC) that is equipped with a fast rotating mode stirrer. By varying the speed of the mode stirrer, different levels of Doppler spreads are created, and the 802.11p radio system is tested accordingly. As expected, the Doppler spread affects the package error rate (PER) of the radio system adversely. In addition to measurements, a simple PER model is presented, which sheds some light into the OTA tests.

Analysis and optimization of MIMO capacity by using circuit simulation and embedded element patterns from full-wave simulation

A method for analyzing and optimizing multi-port antennas in MIMO systems is presented and exemplified. The method is based on work presented in [1]–[3] and uses data from full wave electromagnetic field (EM) solvers in combination with circuit simulations for efficient calculations of radiation properties of multi-port antennas. Here it is shown that the method can also be used for simulations of antennas in a MIMO system. The main advantage of the proposed method is that only a few full-wave simulations, which usually are time consuming, are needed when e.g. optimizing the matching circuits for a multi-port antenna. Since embedded element patterns are used, MIMO capacity (and of course all other relevant antenna parameters) can efficiently be computed for any matching network connected to the antenna ports and for different channel models, both statistical and deterministic.

Study of diversity gain obtained with two PIFA antennas on a small ground plane for a UMTS terminal

In this work, diversity performance of two PIFA antennas on a small ground plane is studied. In this case, when the second antenna is located on the left edge, better diversity gain can be obtained. Matching network can be used to reduce the correlation coefficient and consequently increase the diversity gain.

Analysis and optimization of multi-port antennas by using circuit simulation and embedded element patterns from full-wave simulation

A method for efficiently analyzing and optimizing multi-port antennas based on the use of a port response matrix and embedded element patterns has been presented. This has been implemented in software which uses data from commercial full-wave EM codes and communicates with a circuit simulator for fast evaluation of antenna parameters for arbitrary port loadings. The method is especially useful for optimization which was demonstrated by a simple example.

Curvature based antenna selection method evaluated using the data age metric and V2V measurements

In this paper, we compare a method for selecting transmission antenna based on road curvature to a method based on periodically alternating between left and right hand side transmission antennas. Both methods aim to improve the success rate for communication between participants in a platoon of vehicles. Moreover, we propose the data age metric for online use as input to the algorithm controlling the inter-vehicle distance in platooning, e.g. to decide appropriate gap between the vehicles depending on the V2V communication quality. The methods have been evaluated through V2V communication measurements performed using heavy duty vehicles on public highway. We show that, when using the curvature-based method, a 150 ms data age deadline is only missed approximately half as often compared to when periodically alternating between left and right hand side transmission antennas. The methods have also been compared for different antenna combinations.

Combination of Full Wave Simulations and Equivalent Circuit Models in Predicting Coupling between Antenna Element and Nearby Object in Mobile Phone

This paper presents a simple method for using data from full wave simulations in combination with lumped circuit models for calculating port responses for arbitrary loading and excitation conditions. Data from full wave simulations are used for constructing a matrix representation of port responses that is used in a circuit simulator code where arbitrary active and passive components can be added to the circuit. By this it is possible to evaluate different circuit configurations efficiently without the need of performing additional full wave simulations.