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Abstract

Monitoring of permanent stations that make up the reference frame is an integral part of the geodesists work. Selection of reference stations is based on analysis of parameters characterizing them (hardware, coordinates’ stability, mounting, location). In this paper, we took into account phase residual as an indicator of unmodelled signal. Phase residuals were computed based on ASG-EUPOS and EPN observation processing. The results show the connection between the method of mounting the antenna and the residuals. We have reviewed multipath effect at ASG-EUPOS stations, and chosen those which are characterized by the highest value of phase residual. The results show that LC phase residual is a good factor to characterize site’s solutions’ reliability. For majority of sites RMS values were less than 10 mm. Modulations associated with multipath effect were observed for few ASG-EUPOS sites only. Phase residuals are distributed specifically for sites, which antennas are mounted on pillars (more common for EPN sites). For majority of analysed sites phase residual distribution was similar for different days and did not depend directly on atmosphere condition.
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Authors and Affiliations

Andrzej Araszkiewicz
Karolina Szafranek
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Abstract

This paper focuses on the radio direction finding (DF) in multipath environments. Based on the measurement results presented in the open literature, the authors analyse the influence of environment transmission properties on the spread of the signal reception angle. Parameters that define these properties are rms delay and angle spreads. For these parameters, the mutual relationship is determined. This relationship is the basis for assessment of the required number of bearings that minimize the influence of the environment on the accuracy of DF procedure. In the presented analysis, the statistical properties of the signal reception angle are approximated by the normal distribution. The number of bearings versus the rms delay spread is presented as the main objective of this paper. In addition, a methodology of the bearings’ spatial averaging that provides better estimation of the reception angle is shown.
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Authors and Affiliations

Cezary Ziółkowski
Jan Marcin Kelner
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Abstract

This article provides a thorough description of a range of non-standard application cases in which EMC laboratories can be used other than those traditionally associated with this kind of facilities. The areas covered here include investigations of: wireless and radio systems (such as IoT and broadband radio systems) also that require ultra-high operational dynamic range, emulation of interference-free and/or heavilymultipath propagation environment, shielding effectiveness of cabinets and materials (i.e. thin, light and flexible as textiles as well as heavy and thick such as building construction elements).

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Authors and Affiliations

Kamil Staniec
Zbigniew Jóskiewicz
Jarosław Janukiewicz
Tadeusz Więckowski
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Abstract

The underwater acoustic communication (UAC) operating in very shallow-water should ensure reliable transmission in conditions of strong multipath propagation, significantly disturbing the received signal. One of the techniques to achieve this goal is the direct sequence spread spectrum (DSSS) technique, which consists in binary phase shift keying (BPSK) according to a pseudo-random spreading sequence.
This paper describes the DSSS data transmission tests in the simulation and experimental environment, using different types of pseudo-noise sequences: m-sequences and Kasami codes of the order 6 and 8. The transmitted signals are of different bandwidth and the detection at the receiver side was performed using two detection methods: non-differential and differential.
The performed experiments allowed to draw important conclusions for the designing of a physical layer of the shallow-water UAC system. Both, m-sequences and Kasami codes allow to achieve a similar bit error rate, which at best was less than 10 −3. At the same time, the 6th order sequences are not long enough to achieve an acceptable BER under strong multipath conditions. In the case of transmission of wideband signals the differential detection algorithm allows to achieve a significantly better BER (less than 10 −2) than nondifferential one (BER not less than 10 −1). In the case of narrowband signals the simulation tests have shown that the non-differential algorithm gives a better BER, but experimental tests under conditions of strong multipath propagation did not confirm it. The differential algorithm allowed to achieve a BER less than 10 −2 in experimental tests, while the second algorithm allowed to obtain, at best, a BER less than 10 −1. In addition, two indicators have been proposed for a rough assessment which of the detection algorithms under current propagation conditions in the channel will allow to obtain a better BER.
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Authors and Affiliations

Jan H. Schmidt
1
Iwona Kochańska
1
Aleksander M. Schmidt
1

  1. Faculty of Electronics, Telecommunication and Informatics, Department of Signals and Systems Gdansk University of Technology Gdansk, Poland

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