Dariusz Wójcik

Evaluation of near field of the GSM base station antennas in urban environment

A simple and efficient method for evaluation of the near field of GSM base station antennas in an urban environment is presented in this paper. The method is based on the replacement of the panel antenna with a discrete linear array. Moreover, the geometrical optics approach is used to consider the influence of the environment. The approximate results are found to be in excellent agreement with the results obtained by using the method of moments (MoM). The presented method can be successfully used for fast evaluation of exposure to electromagnetic fields emitted by the GSM base station antennas in urban environments.

Absorption of EM energy by human body in the vicinity of the GSM base station antenna

A hybrid method is proposed for specific absorption rate analysis in a human body in the near field of typical GSM base-station panel antenna. The method combines the FDTD technique with an analytical description of the near field of the isolated antenna. The approximate results are found to be in excellent agreement with the results obtained by using the traditional FDTD method. The most important advantage of the proposed approach is minimization of computer memory requirements and computation time.

Immunity of medical electrical equipment to radiated RF disturbances

Immunity of medical equipment to radiated radio frequency (RF) electromagnetic (EM) fields is a priority issue owing to the functions that the equipment is intended to perform. This is reflected in increasingly stringent normative requirements that medical electrical equipment has to conform to. A new version of the standard concerning electromagnetic compatibility of medical electrical equipment IEC 60601-1-2:2014 has recently been published. The paper discusses major changes introduced in this edition of the standard. The changes comprise more rigorous immunity requirements for medical equipment as regards radiated RF EM fields and a new requirement for testing the immunity of medical electrical equipment to disturbances coming from digital radio communication systems. Further on, the paper presents two typical designs of the input block: involving a multi-level filtering and amplification circuit and including a solution which integrates an input amplifier and an analog-to-digital converter in one circuit. Regardless of the applied solution, presence of electromagnetic disturbances in the input block leads to demodulation of the disturbance signal envelope. The article elaborates on mechanisms of amplitude detection occurring in such cases. Electromagnetic interferences penetration from the amplifier’s input to the output is also described in the paper. If the aforementioned phenomena are taken into account, engineers will be able to develop a more conscious approach towards the issue of immunity to RF EM fields in the process of designing input circuits in medical electrical equipment.

Design of dual-polarized MIMO linear antenna arrays with increased port-to-port isolation

In the paper selected issues of feeding networks for dual-polarized linear antenna arrays designed for 2×2 MIMO applications are described. The influence of topology of corporate feeding network on achieved port-to-port isolation is shown as the result of computer simulations. As an example, four element linear arrays of two-layer electromagnetically coupled microstrip antennas designed for U-NII 5.15-5.85 GHz frequency band are examined in CST Microwave Studio.

Hybrid FDFD-MoM method for analysis of dielectric-covered thin-wire antennas

In this paper a hybrid technique combining finite-difference frequency-domain technique with method of moments is presented. The technique is designed for efficient analysis of arbitrary curved thin-wire antennas radiating in vicinity of dielectric scatterers. FDFD-MoM technique is successively employed for numerical analysis of dipole and helical antennas in dielectric cover.

SPICE-equivalent model for predicting effects of electromagnetic field coupling to transmission lines

The paper briefly describes a full-wave frequency-domain (FD) approach aimed at developing a SPICE-equivalent circuit model for predicting the effects of coupling of external electromagnetic fields to transmission lines (TLs). The approach employs the method of moments combined with rational approximation of the desired observable, and vector fitting technique. A Norton equivalent circuit representing the TL structure at the selected port is derived from the results of FD numerical simulation. Numerical example demonstrates the usefulness and efficiency of the approach.