Signal distortion in helicopters antenna system

Effect of Phase-Encoding Reduction on Geometric Distortion and BOLD Signal Changes in fMRI

Introduction Echo-planar imaging (EPI) is a group of fast data acquisition methods commonly used in fMRI studies. It acquires multiple image lines in k-space after a single excitation, which leads to a very short scan time. A well-known problem with EPI is that it is more sensitive to distortions due to the used encoding scheme. Source of distortion is inhomogeneity in the static B0 field that ...

Multiple - Antenna Signal

Reduction of Nonlinear Distortion in Multi-Antenna WiMAX Systems

Multiple-input multiple-output (MIMO) techniques in combination with orthogonal frequency-division multiplexing (OFDM) have already found its deployment in several standards for the broadband communications including WiMAX or 3GPP proposal termed as Long Term Evolution (LTE). The MIMO-OFDM allows to substantially increase the spectral efficiency, link reliability and coverage of the signal tran...

Studies on Microwave Antennas: Passive Intermodulation Distortion in Antenna Structures and Design of Microstrip Antenna Elements

Passive intermodulation (PIM) measurements of antennas and the design of dual-polarised microstrip antenna elements are investigated in this thesis. The emphasis is on the development of a passive intermodulation source localisation method and on the studies of the PIM source behaviour under various impedance loading conditions. Passive intermodulation distortion can be harmful in wireless comm...

Estimation of Signal Correlation in Antenna Arrays

The correlation between signals received with different antenna elements is an important parameter in an adaptive array. In this paper it is shown that when the signal DOA distribution is uniform the signal correlation can be calculated using measured S-parameters of the antenna input ports. When the spread of the angle of arrival is known, the scattering parameters allow also to estimate the c...