Premysl Hudec

UHF RF Identification of People in Indoor and Open Areas

The performance of an ultra-high-frequency RF identification (ID) system operating at 869 MHz, intended for the ID of persons in both indoor and open areas, has been validated using the propagation models, as well as the series of practical measurements. A two-ray propagation model and the 3-D ray-tracing model were used for calculations of all important system parameters in open and indoor areas, respectively. For the application mentioned above, a novel (electrically small and, at the same time, low-profile) wearable TAG antenna was designed. It was used in order to carry out the necessary tests as well. The antenna in question is based on an artificial-like surface. The latter provides an important screening effect and avoids detuning. Another virtue of the surface used is represented by the fact that it ensures the minimum loss of the antenna efficiency (resulting from the presence of a nearby human body). The simulations and measurements show that the optimized system can guarantee a reliable ID at distances up to 9 m in open areas and up to 16 m in corridors.

Microwave system for the detection and localization of mobile phones in large buildings

A novel monitoring system for the detection and localization of mobile (cellular) phones in large buildings based on a matrix of microwave sensors has been designed and practically employed. The system enables detection of all active mobile services and ensures very high immunity against all other radio signals. The designed antennas, system structure, and signal processing provide high probability of correct localization of the transmitting mobile phone. Thus far, microwave detection systems with several thousands of sensors have been installed and successfully operated in several prisons in the Czech Republic. The system has been found to be an efficient tool for improving security in highly guarded areas.

Hidden problems in precise calibration on microstrip

A study of calibration problems on microstrip with respect to interaction of electromagnetic fields around SMA to microstrip launcher and microstrip short was carried out in frequency band up to 26 GHz. Omni Spectra SMA to microstrip launcher, 50 Omega microstrip line on Arlon CuClad 223 0.508 mm thick substrate and microstrip shorts with reflective wall above the upper side of substrate as a calibration elements were used for simulations in CST Microwave Studio. Strong influence of dimensions of shorts and distance between the shorts and the launcher on simulated calibration data was observed. Reasonable dimensions of the short and the distance between the short and the launcher making possible correct precise calibration were determined.

Generalized Approach for Phase Interferometric Measurements of Electromagnetic Field

A new generalized approach for microwave phase interferometric measurement of electromagnetic fleld using an antenna matrix (AM) was developed. The approach allows correction of most signiflcant measurement errors caused by mutual couplings of closely spaced antenna elements. It is based on vector measurements of the AM designed for the frequency 2.60GHz and Matlab simulations.

Efficiency Treatment of Composite Right/Left-Handed TL Zeroth-Order Resonator Antenna

Antenna efficiency of zeroth-order resonator (ZOR) antenna implemented in composite right/left-handed transmission line (CRLH TL) microstrip structure is treated by method of moment simulator IE3D. Radiation is investigated from individual portions of the antenna structure according to calculated amplitude of surface current density. Dominantly radiating regions are identified, geometrically emphasized, and efficiency improved version of CRLH ZOR antenna is designed, realized, measured and compared with initial design. Improvement of simulation antenna efficiency from 10 to 75% and 4x increased measured gain at design ZOR frequency has been found.

Analysis and Measurement of the RFID System Adapted for Identification of Moving Objects

A system study of ability of using a commercially available 869 MHz RFID system for identification of moving objects has been performed. The study has been focused on a power budget of received signal levels and on identification of main signal fadings and their quantification. Two types of TAG antennas have been used. Comparisons of their radiation properties when operated in the close vicinity of the human body (or a simple phantom of a human body) have been performed. Suitability of their use is discussed. Results of this study provide deeper insight in the given problem and information in which way the system should be improved in order to comply with the intended purposes

The optimization of the RFID system for the identification of sportsmen in mass races

The optimization of a standard UHF RFID system for identification of sportsmen in mass races was proposed, realized and verified. The work was based on a system study that identified the main reasons of system failures. The proposed and realized improvements were focused on a development of more efficient and directive antennas for both the reader and the transponder and on an optimization of their location and orientation. The used propagation model turned out to be able to describe the existing fading phenomena and to predict the received signal levels anywhere in a 5 m wide finishing corridor. The optimized RFID system was tested in a standard outdoor operation, the results showed 100% identification reliability.

A Novel Vector Microwave Phase Interferometer

The paper describes a concept of a novel vector microwave phase interferometer based on a vector network analyzer system. The instrument is designed for fast vector measurements of a space distribution of an interference electromagnetic field using a matrix of antennas. It is supposed to be used in non-contact deformation and non-homogeneity measurements in civil engineering and other areas. Results of first measurements performed in the 2.45 GHz frequency band are presented

General Method for Characterization of Power-Line EMI/RFI Filters Based on S-Parameter Evaluation

This paper deals with a general working approach for determining the lowest possible insertion loss of power-line interference filters in their stop bands at high megahertz or gigahertz frequencies. It is shown that at these frequencies, the measurement methods recommended for testing of interference filters in available standards for frequencies up to 1 GHz fail in determining their lowest possible insertion loss. This problem is solved by the newly developed method which also enables the characterization of concerned filters in a completely impedance unknown environment. It is based on two-port vector network analyzer measurement and postmeasurement data processing applying an impedance matching technique. Experimental verification of the new method using two Maury Microwave automated tuners and a cascade of low-pass coaxial filters was performed in the frequency band from 6 to 12 GHz. The results show that measurement-evaluation procedures performed according to the newly developed method provide more reliable and precise results when compared to measurement procedures corresponding to methods described in common standards. The new method was also applied to the characterization of a professional EMI/RFI filter from 1 to 10 GHz.

An Experimental Study of the Lowest Troposphere Layers at 10 GHz - First Results

In this paper an extensive innovative experiment for combined, both local and remote sensing of the troposphere is introduced. The experiment is based on a unique set of mutually linked, time-space dependent, synchronized radio-electrical and radio-meteorological measurements. The first results for first two months of operation are presented and discussed as well.