Shinobu Ishigami

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.

Estimation of E-field distribution in a loaded GTEM cell

The E-fields in a loaded GTEM (gigahertz transverse electromagnetic) cell and an anechoic chamber with an equipment under test (EUT) were calculated by using the FDTD (finite-difference time-domain) method at frequencies of up to 1 GHz when the EUT was modeled by a conductive cube. A coefficient is proposed that is intended to evaluate the difference between an average of the E-fields on the six surfaces of the EUT in a case where the EUT is loaded and unloaded. As a result, the maximum deviation from the coefficient in the anechoic chamber for that in the GTEM cell became larger as the EUT size was increased, and the deviation was less then 5.0 dB when the ratio of an EUT size to a distance between the septum (inner conductor of a GTEM cell) and the floor conductor was below 0.4.

Complex antenna factor of a V-dipole antenna with two coaxial feeders for field measurements

In transient field measurements, an antenna with wide band performance both in amplitude and in phase is desired. The complex antenna factor (CAF) is an appropriate characteristic of such an antenna. It is convenient that the CAP of the wide-band antenna is able to be calculated easily. For this purpose, a V-dipole antenna with a balun consisting of two coaxial feeders is investigated. The calculated complex antenna factors are compared with the measured values. The results show that the V dipole has the wide-band performance and the CAF is calculable.

Development and Evaluation of a Prototype Multichannel APD Measuring Receiver

Development of a multichannel APD measuring receiver is necessary to enable evaluation of the impact of wideband disturbance emissions on digital wireless communication services which use multicarrier transmission systems. We describe technical details of the worlds first multichannel APD measuring receiver which we have developed using a general-purpose ADC-FPGA board. Our measurements of the basic performance of this receiver show that the receiver is suitable for practical use. We also used the developed receiver to measure the APDs of disturbance emitted from a microwave oven at five frequency points (1 MHz apart). These results indicate the significance of the multichannel APD measuring receiver.

Transfer impedance of new-type calibration target and reconstruction of injected currents for air discharges from electrostatic discharge generators

We measured in the frequency range from 300kHz to 6GHz of the transfer impedance of a commercially available calibration target newly developed for immunity testing against electrostatic discharges (ESDs) being prescribed by the International Electrotechnical Commission. The result showed that the transfer impedance has an almost flat frequency response up to 6GHz, while resonance phenomena were still observed at frequencies around 2.5 and 5GHz. With this result, the waveforms of injected currents onto the target were reconstructed from the observed output voltages for air discharges of an ESD generator with a charge voltage of 2kV.

Reconstruction of discharge currents injected on calibration target from electrostatic discharge generators

In the present study, measurements were made in the frequency range from 300kHz to 6GHz of the transfer impedance of a commercially available calibration target used for the immunity testing against electrostatic discharges (ESDs) that the International Electrotechnical Commission (IEC) prescribes, and thereby the waveforms of discharge currents injected onto the target were reconstructed from their observed output voltages for contact and air discharges of an ESD generator with a charge voltage of 2kV. As a result, it was confirmed that the transfer impedance has an absolute value of almost 1 Ω at frequencies up to 6 GHz, while resonance phenomena were observed at frequencies around 2 and 5 GHz. This result has demonstrated that the reconstructed discharge current waveforms agree well with those of the observed voltages for the contact discharge and air discharge with slow approach, producing the current with a rise time of almost 1 ns, while the reconstructed current has a slightly small peak and gentle rising part in comparison with those of the observed voltage for the air discharge with fast approach, which gives the current within a rapid rise time of a hundred pico-seconds.

Evaluation of interference between MB-OFDM UWB and wireless LAN systems using a GTEM cell

In this study, the electromagnetic interference of an MB-OFDM UWB system with an IEEE802.11a wireless LAN was evaluated using a GTEM cell. Band #3 (out-of-band radiation for 11a) in the band plan of the MB-OFDM UWB system and Band #4 (in-band radiation for 11a) were assumed to be two different types of interference. As a result, when the frequencies of the MB-OFDM UWB corresponded to Band #3, the MB-OFDM UWB system may not interfere with the wireless LAN. In the other band, although the interference power of the MB-OFDM UWB was less than the receiver noise of the wireless LAN, the MB-OFDM UWB system interfered with the wireless LAN. In addition, the separation distance was evaluated from the power inputted to the GTEM cell. As a result, for the vicinity of the minimum receiver sensitivity of the wireless LAN, the separation distance was about 3 m. Finally, the amplitude probability distribution (APD) of the MB-OFDM UWB system that was the interference source was evaluated. As a result, the APD characteristics of MB-OFDM UWB were slightly different from those of additive white Gaussian noise (AWGN).

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.