Ifong Wu

Characteristics of Radiation Noise from an LED Lamp and Its Effect on the BER Performance of an OFDM System for DTTB

The characteristics of radiation noise from an LED lamp and its effect on the bit error rate (BER) performance of an orthogonal frequency-division multiplexing (OFDM) system for digital terrestrial television broadcasting (DTTB) are investigated. The waveform and frequency spectrum of radiation noise from an LED lamp are measured. A sequence of noise pulses is observed, caused by the switching circuit of the LED, and spread over the broadcast band of Japan. The relationship between the radiation noise from the LED lamp and its effect on the BER performance of the OFDM system using 64-quadrature amplitude modulation (64QAM) is evaluated using amplitude probability distribution (APD) measured with various resolution bandwidths. The behavior of the APD of the noise is similar to Gaussian noise when the resolution bandwidth becomes narrow. The BER performance of the OFDM system subjected to the noise of the LED lamp is estimated from the APD results, which agree well with measured results subjected to the LED noise. The characteristics of sequential LED noise are similar to the effect of Gaussian noise on the BER performance of the OFDM system for DTTB. Therefore, the APD measurement is a useful method to estimate the characteristics and effect of noise from an LED lamp on the OFDM system.

Relation between electromagnetic noise from LED light bulb and its impact on bit error rate performance of DTTB

A relation between electromagnetic noise from an LED light bulb and its impact on BER performance of the DTTB is estimated from the APD measurement. First, the APD of the noise is measured with various resolution bandwidths. The characteristic of the APD of the noise is similar to the Gaussian noise when the resolution bandwidth becomes narrow. Then, the BER performance of the DTTB subjected to the noise of the LED light bulb is estimated from the APD result with the resolution bandwidth that is nearly equal to the subcarrier band range of the DTTB. As a result, the BER of the estimated result agrees well with measured results which are subjected to the LED light bulb and the Gaussian noise. Therefore, the effect of the noise from the LED light bulb on the DTTB is similar to the effect of the Gaussian noise.

Evaluation of electromagnetic radiation from the DC side of a photovoltaic power generation system

The radiation mechanism from the DC side of a photovoltaic (PV) power generation system is investigated at frequencies between 150 kHz and 30 MHz. To determine the source of the outbreak of the common mode noise, the balancing of the PV measurement model, which is composed of a PV panel and a 2-m-long DC cable, is measured by the mixed-mode S-parameter method. Results showthatthe PV model has good balance. Then, a balanced PV simulation model is proposed. To express the common mode noise, the input signal is supplied to only one of the two wires of the PV simulation model. To confirm the validity of the PV simulation model, the current flowing in the DC cable and the magnetic field from the PV simulation model are compared with those of the PV measurement model. A good agreement between the measured and simulation results is obtained. The PV simulation model is valid for evaluating the radiation noise from the DC side of the PV power generation system. Moreover, the effect of the frame wire of the PV power generation system on the radiation noise is evaluated. The radiation noise from the PV power generation system will strengthen or weaken depending on the layout of the frame wire, especially at low frequency. The radiation noise from the PV power generation system with a plurality of PV panels is also investigated. The peak of the frequen cy spectrum of the radiation noise shifts to lowfrequency when the number of PV panels is increased.

Probe calibration by using a different type of probe as a reference in GTEM cell above 1GHz

Calibration of an electric field probe using a different type and size of probe as a reference is carried out in a GTEM cell from 1 to 6GHz. We compared our results with those of calibration in an anechoic chamber to determine the effectiveness of the calibration. The difference between the calibration factors of the GTEM cell and the anechoic chamber increases when the probe is calibrated in an area in which the electric field distribution is nonuniform. Therefore, it is important to place the probe in an area with good uniformity or maintain the uniformity of the electric field in the GTEM cell when calibrating electric field probes with different dimensions.

Effect on electric field of foam block in GTEM cell

The effect on the electric field of a foam block in a GTEM cell was numerically investigated using the finite integration (FI) method. In particular, we focused on the frequency range of 1–16 GHz, for which the effect has not yet been sufficiently analyzed. We only modeled the tip of the GTEM cell, to focus on the change in the electric field strength from the foam block and also to reduce the computational resources required. We showed that the foam block increases the electric field strength when it is placed at the tip of the GTEM cell. Even though the change in the electric permittivity was small, the effect on the electric field strength was great. We then compared the analysis results with measurement results and found that good agreement was obtained between the two. We also investigated the effect that the size of the foam block has on the electric field. The electric field strength was found to increase when the block size increased. We concluded that the foam block may affect the electric field and increases the electric field strength in a GTEM cell.

Calibration of electric field probes with three orthogonal elements by standard field method

Electric field probes with three orthogonal elements were calibrated from 1-6GHz by the standard field method in an anechoic chamber. A special jig was constructed for setting and calibrating a Δ-beam-type probe. Calibration factors of the probes were obtained for each element using this jig. To reflect the future revision of IEC 61000-4 series, uncertainty in the calibration factors was investigated to improve calibration quality and determine the factors affecting calibration. We found that fluctuation in the power transmitted from a high power amplifier and the imperfection of the anechoic chamber were the most important factors affecting uncertainty.

Calibration of electric field probes in GTEM cell using reference antenna method

Calibration of electric field probes in a GTEM cell is carried out using the reference antenna method. To determine the effectiveness of the calibration, we compared our results with those of calibration in an anechoic chamber from 1 to 6GHz. Each electric field probe had three elements, one of which was used to calibrate the other two. The calibration factors in the GTEM cell agree well with those in the anechoic chamber. Therefore, the GTEM cell is as effective as the anechoic chamber for calibrating electric field probes with the same type of probe and helps save more measurement time and effort.

A study of the surface current distribution on the microwave transmission line using Green's function

Abstract A method for estimating the currents on the microwave transmission line is proposed. In this method, the substrate is divided into a wire-grid model. Then the magnetic near field strength above the microwave transmission line is calculated and measured. Based on the magnetic near field strength, the magnetic field integral equation is established by applying the Green’s function and is used to estimate the currents flowing on the microwave transmission line. In this paper, the current distribution which is calculated by FDTD method with the interpolation (first order) and estimated current distribution by applying the Green’s function on the microstrip line and the coplanar line is evaluated by using the calculated magnetic field components. As a result, a good agreement between both results is observed and the validity of this method is confirmed. Furthermore, the validity of the current estimation by measuring the magnetic near fields is confirmed by comparing the current obtained from the measured magnetic fields and the calculated magnetic fields. Comparing between the measured and calculated results, a good agreement is observed between both results on the strip line area. However, differences are also observed on the dielectric substrate area.

A Study of Near Field Shielding Effect Measurement for Oval Human Phantom Model using the Conductive Material Shield

In this study, the near field human shield is investigated, which measured the shielding effect of the oval human phantom model, by locating the conductive material shield in front of the phantom model. Also the shielding effect is investigated with the FDTD (Finite Difference Time Domain) method, to confirm the validity of the measurement method. According to the results, it has been shown, that more than 30 dB of the shielding effect is observed for the small gap distances between the shield and phantom model, with the square shield length of 1.0 ¿. On the other hand, very little and also negative shielding effect observed for the square shield length of 0.25 ¿. Furthermore, due to the good agreement between the measured and calculated results, the validity of our measurement method is confirmed.

Evaluation of radiation mechanism of LED noise and its impact on communication quality of digital terrestrial television broadcasting

The radiation mechanism of electromagnetic noise from an LED lamp and its impact on communication quality of digital terrestrial television broadcasting (DTTB) are investigated. The impulses of the electromagnetic noise from the LED lamp are observed and synchronized to the light-dark changes in the light emission which is controlled by the switching regulator of the LED lamp. The switching regulator of the LED lamp is the source of the outbreak of the LED noise. Then, the distribution of current on the lighting duct rail is measured. The LED noise is flowing on the lighting duct rail. This noise is generated in the LED lamp and radiated to the free space through the lighting duct rail of the LED lighting system. Furthermore, the communication quality of DTTB subjected to the LED noise is evaluated by the amplitude probability distribution (APD). Measuring APD of the LED noise is a useful method to evaluate the characteristics of the LED noise. The tolerance level of the LED noise for the reception of the DTTB signal is estimated from the APD curve of the LED noise.