Fujio Amemiya

Development and analysis of electric field sensor using LiNbO/sub 3/ optical modulator

The sensitivity of an electromagnetic field sensor which uses a LiNbO/sub 3/ electrooptical crystal and an optical-fiber link is improved by using a Mach-Zehnder interferometer, whose half-wave voltage is about 4 V at 1.3- mu m wavelength, and a YAG laser pumped by a laser diode whose output power is 25 mW. The resulting frequency response is about flat from 100 Hz to 300 MHz, and the minimum detectable electric field strengths are 0.22 mV/m at 50 MHz and 0.079 mV/m at 750 MHz. The variation of the sensitivity with the frequency and element length are analyzed using the moment method, and the calculated results agree with the measured results. The measurement of the cross-polarization of the sensor indicates that this property is similar to that of a dipole antenna. The improved sensor can measure an electromagnetic impulse whose peak value is larger than 10 V/m and whose width is wider than 5 ns. >

Developing a common-mode choke coil with high-permeability core used high-speed telecommunications port for UTP cable

The choke coil used in a telecommunications port for unshielded twisted pair (UTP) cable needs a high common mode impedance across a wide range of frequencies because UTP cable has no grounding port. A high permeability ferrite core was used to get a high common-mode impedance across a wide range of frequencies and a low level of insertion loss at high frequencies. As a result, the frequency range is about four times better than that for a conventional core and an insertion loss for telecommunications signals is about half that for the choke coil used with 10Base-T Using the coke coil for a 100Base-T LAN port, the measured improvement in immunity indicates that a wire length of more than 0.5 m is desirable to give sufficient performance.

Investigation of interferences between wireless LAN signal and disturbances from spread spectrum clocking

The disturbance wave from a personal computer (PC) employing spread spectrum clocking was converted to the frequency range using a wireless LAN system. The wave was impressed on to the wireless LAN signal to investigate its influence on the radio telecommunication system using a broadband signal. The results indicate that the influence from a PC employing spread spectrum clocking was more serious than that from a PC not employing spread spectrum clocking. A frequency modulation signal and white noise were also impressed on to the wireless LAN signal. The result indicated that the frequency modulation signal, whose modulation frequency is from 1 kHz to 10 kHz and modulation frequency deviation is the same as that of the disturbances from a PC employing spread spectrum clocking, can be used as the artificial source to investigate the interference.

Measurement And Analysis Of Electromagnetic Pulses Caused By Electrostatic Dischrage

This paper describes experimental and analytical results of electromagnetic pulses caused by electrostatic discharge (ESD). Energy spectra of ESD pulses measured by plural antennas are analyzed for three frequency domains ( Analytical results show that ESD energy does not always increase in proportion to discharge voltages and that ESD pulses produced by low voltage ESD may cause strong electromagnetic interference. 1-30MHzI 30-200MH2, 200-750MHz ) .

A Design Method for the Asymmetric Artificial Network With an Asymmetrical Transformer

Conducted asymmetric disturbances are measured at telecommunication ports of equipment under test using an asymmetric artificial network (AAN). Therefore, theoretical investigations are carried out to characterize an AAN with a mode-impedance matrix, introducing the common-mode and differential-mode impedances. By referring to this matrix, a theoretical design method is developed for the AAN with an asymmetrical transformer to satisfy the requirements for the mode impedances and the longitudinal conversion loss. By using this design method, two different prototype AANs are assembled: one meets the CISPR 22 specifications, and the other is used in power line telecommunication modem tests. A detailed experimental examination of the assembled AANs validates the proposed theoretical design method.

Development of wide-band and highly sensitive electric field sensor using LiNbO/sub 3/ optical modulator

A Mach-Zehnder interferometer whose half-wave voltage is about 4 V and a YAG laser pumped by a laser diode whose output power is 25 mW are used to improve the sensitivity of a LiNbO/sub 3/ electromagnetic field sensor. The resulting frequency response is almost flat from 100 Hz to 300 MHz and the minimum detectable electric field strength is 1 mV/m at 50 MHz and 0.14 mV/m at 750 MHz. The frequency response of the sensor is analyzed using the moment method, and the calculated results agree with the measured results. The improved sensor can measure an electromagnetic impulse whose peak value is larger than 10 V/m and width is wider than 5 ns.<<ETX>>

Method of Measuring Voltage without Cable Correction by Loading Capacitance Changeable CVP

Capacitive voltage probe (CVP) can measure the common mode disturbance voltages without contact to cables. However, it is necessary to obtain the correction factor for each cable within correction. Although the measurement method using two CVPs has been developed to measure the voltage without the correction, it needs two CVPs and a signal generator. This paper proposes the measurement method without correction using the loading capacitance changeable CVP (LCC-CVP). To evaluate the performance, a cable was replaced with a copper rod, and the deviation from the actual common mode voltage was measured. The results indicated that the deviation was within 3dB from 0.15 MHz to 30 MHz, the measurement value slightly changes depend on the loading capacitance value, and the deviation increases when the frequency is greater than 10 MHz. The disturbances from telecommunications equipment were measured to confirm the validity of the LCC-CVP. The results indicated that the measurement results were almost the same as the results using impedance stabilization network (ISN) when the sufficient large capacitance was used as the loading capacitance.

Evaluation method of common-mode choke coil used for high speed telecommunications port

A method of measuring characteristics of the common-mode choke coil, which is used for a high-speed telecommunications system using UTP cable, is needed to evaluate the performance. We present a new method of measuring the S-parameters of the coil. The two-port F-matrix parameters of the balun were obtained from three-port S-parameters, and the S-parameters of the coil were measured at the unbalance port of the baluns, which was connected to both ends of the coil. The F-matrix parameters of the coil were obtained from the F-matrix parameters of the balun and the measured S-parameters. When two baluns were connected to each other at the balance ports, the S-parameters were measured find compared with the calculated value from the F-matrix parameters of the balun. The results indicated that the difference was within 0.1 dB from 30 MHz to 100 MHz, and within 1 dB from 100 MHz to 300 MHz. The differential mode insertion losses were also measured for five types of the coils. The results indicated that the proposed method obtained a realistic insertion loss value which was not less than 0 dB although the insertion loss measured by the usual method was not a realistic value because it was less than 0 dB up to 100 MHz.

Investigation of emission reduction effect from interface cables using amorphous magnetic-alloy film

This paper describes the effect of amorphous magnetic-alloy film in achieving emission reduction. This film is expected to replace ferrite because of a high permeability that exceeds Snoeks limit and a low required thickness. In the investigation, an amorphous magnetic-alloy film was wound around a cable. Then, the cables emission levels were measured in a semi-anechoic chamber at a distance of 3 m. We examined to what degree film length, film position, and film thickness have an effect on the emission reduction from cables protected with amorphous magnetic-alloy films. The experiment results indicated that a 1 m long region wound with the magnetic-alloy film was required in order to achieve identical emission reduction levels as those of typical ferrite cores. In addition, the results show that the reduction effect was enhanced when a ferrite core was used in combination with the film, and that there were few advantages in reducing emission when a metallic thin film was applied on one surface of the magnetic-alloy film.

Investigation of radiation source using disc-cone antenna with optical/electrical converter operating from 1 to 10 GHz

The recent progress of radio wave communication and high-speed electrical equipment has brought the need for radiation sources operating at more than 1 GHz to evaluate EMC test facilities and shielding characteristics. This paper proposes a radiation source using a disc-cone antenna with an O/E converter. A wire grid model construction based on a triangle was studied to maintain the wire density constantly, and a laser diode with an electroabsorption (EA) device was used as the E/O converter. The radiation source was constructed, and the characteristics were measured in an anechoic chamber from 0.3 to 10 GHz. The investigation indicated that the calculation accuracy was improved to employ the wire grid model based on a triangle, and the deviation between the calculated value and the measured value is within /spl plusmn/3 dB from 1 to 10 GHz. This also indicated that the deviation of the gain is within /spl plusmn/5 dB from 1 to 10 GHz and the maximum radiated field is more than 0.1 V/m at a distance of 1 m. Using the radiation source, the shielding effect of the PC case was investigated. The results indicated that the shielding effect decreased in proportion with the increase in frequency, and a careful design is important for maintaining the shielding effect in this frequency range.