Borivoj Modlic

Measurement of electric field probe error for pulsed s

Electric field probe performance is measured inside a calibration waveguide. The electric field probes based on diode detection are designed and calibrated for continuous signals. When measuring electric field strength of a pulsed waveform, performance degradation is expected. The degradation is measured in terms of measurement error. It is defined as electric field strength reading on the probe vs. actual electric field strength in the test volume of a calibration waveguide. Two such probes were measured. Test signals were pulsed (ASK) signals with fixed duty cycle of 1/10 and varying repetition frequency. The results show great differences among the two probes measured. One probe shows only slight degradation in terms of increased reading (positive measurement error) for high repetition frequencies. The second probe shows the same feature but of even greater extent, together with significant degradation for low repetition frequencies in terms of decreased reading (negative measurement error). The existence of such errors demands a great amount of caution during EMC measurements using diode-based electric field probes.

Absorber and resistor contribution in the GTEM-cell

The GTEM-cell is described. The influence of absorbers and resistors is shown. The SWR and return loss as well as time domain measurements were performed on the GTEM-cell as well as on GTEM-cell without resistors, absorbers, and with open and metal end. The obtained data was, compared and the conclusion drawn. The GTEM-cell was modeled with the FEM method as well.

Measurement validation of ship wiregrid models of different complexity

Shipboard HF electromagnetic field distribution is simulated using five wiregrid ship models of different complexity, with a shipboard HF communication transmitter as the source of radiation. The Numerical Electromagnetics Code (NEC 2) is used for computer simulation. Electric field is calculated and then measured in each point. The measurement results are compared with simulation results for each model. The comparison shows that the model of moderate complexity, which albeit includes the main objects in electromagnetic environment, shows the best results. More complex models give similar validation results, but are much more difficult to build and computer-time consuming.

Measurement of Electric Field Probe Response to Modulated Signals Using Waveguide Setup

Electric field probes based on diode-loaded short dipoles bear an inherent limitation of use concerning the signal waveform. When measuring signal waveforms other than sinusoidal, probes can show a considerable measurement error. Although this error has been recognized before, its importance is growing lately due to expansion of new modulation schemes. Therefore, a convenient measurement setup and procedure is needed to examine and measure such probe errors for various types of signals. An example of a waveguide-based measurement setup is presented in this letter. The advantage of the proposed setup is the ability to achieve high field strength in the test volume suitable for field probe testing, using small to moderate output power.

Measured distribution of electric field in GTEM-cell

The electric field inside the GTEM-cell was measured with the field probe. The variation of the electric field was within 3 dB. The measured results were compared with the numerical model performed with finite element method (FEM). There is a very good agreement between measured results and the computer model. Both results prove that almost 80% of the area below septum could be used for testing purposes.

Low-PAPR Spatial Modulation for SC-FDMA

Although spatial modulation (SM) presents an attractive multiple-input–multiple-output (MIMO) technique, it increases peak-to-average power ratio (PAPR) on all transmit antennas when applied directly to single-carrier frequency-division multiple access (SC-FDMA). Therefore, we propose an SM modification, which is called low-PAPR SM (LPSM), to preserve the low PAPR level of SC-FDMA and to achieve the benefits of SM. In addition, as the optimal maximum-likelihood detection (MLD) receiver has a very high computational complexity when applied to SC-FDMA system, we observed suboptimal receivers for SC-FDMA with LPSM. In addition to low-complexity linear receivers, we proposed and analyzed two receivers: near-MLD and improved minimum mean square error (iMMSE) receivers. The near-MLD receiver achieves performance very near to MLD with significantly lower complexity, whereas the iMMSE receiver presents a tradeoff between MLD and linear receivers in terms of performance and complexity.

High Speed Downlink Packet Access Principles

Data services are expected to have significant growth over the next few years and will likelly become the dominant source of 3G traffic. High speed downlink access (HSDPA) provides large enhancements over wideband code division multiple access (WCDMA) for the downlink. HSDPA was standardized as part of third generartion partnership project (3GPP) Relase 5 and Relase 6. The HSDPA peak date rate avaible in the terminals is initally 1.8 Mbps, and it is increasing to 3.6 and 7.2 Mbps with potentially beyond 10 Mbps. HSDPA has been designed to increase downlink packet data throughput by means of fast physical layer retransmission and transmission combining as well fast link adaptation controlled by the Node B -i.e. base transmission station (BTS). The paper covers HSDPA principles for WCDMA -the key new feature included in Relase 5 and enhanced further in Relase 6 specification.

Linear-nonlinear approach to the analytical solution of a diode-loaded short dipole for complex signals

A diode detector consisting of a zero-bias Schottky diode connected to an electrically short dipole is a configuration commonly encountered in electric field measurement applications, e.g. wideband electric field probes. This circuit is described analytically by nonlinear differential equations, due to a nonlinear diode resistance. This problem is solved here using a novel linear-nonlinear analytical approach. It is based on the idea of keeping only the necessary nonlinearity of the circuit, while conveniently linearizing some steps of the procedure. Combining linear and nonlinear steps, the transfer function of a diode-loaded electrically short dipole is solved by a completely analytical, fairly simple procedure. This approach is applied separately to small signals and large signals, and to sine input signal and a complex signal with an arbitrary waveform. The obtained solutions describe the behavior of the electric field probe in various working conditions

Analytical solution of a diode-loaded short dipole response to large and small signals based on linear-nonlinear approach

Using the linear-nonlinear approach, the diode-loaded electrically short dipole response to large and small signals can be calculated completely analytically. The solutions are easy to interpret and are practical for any further analysis. The agreement of results with the previous work that used much more complicated procedures shows that the method is correct. Usefulness of this approach can be applied to other configurations of diode detectors and other types of input signals.

Is There Hazardous Electromagnetic Radiation From Telecom Power Systems - Some Practical Experiences

The interaction of low-frequency electric and magnetic fields or of high-frequency electromagnetic fields with biological systems on whole organisms or on a cellular level requires a detailed experimental and theoretical analysis. In the present contribution attention was paid to the occupational environment in telecommunications and to the equipment leakage radiation characterization. Some scientific outputs of various exposure effects on humans is reviewed. The problems of actual exposure level assessment and the respective safety standards implementation for the health hazards estimation is discussed and suggestions are made therefor. The experimental data resulting from measurements in a telecom switching center are analyzed and used for final conclusions.