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An 88‐year‐old Japanese woman underwent DDD pacemaker (MicroPort KORA 250 DR, V lead: VEGA R52) implantation for complete atrioventricular block. A 12‐lead electrocardiogram for a routine examination showed atrial pacing within the intrinsic P wave, followed by inhibition of ventricular pacing. Pacemaker interrogation revealed no abnormalities in the basic parameters; however, ventricular pacing was...
To determine E-field at a tip of probe for evaluating SAR (specific absorption rate) values of DUTs in saline solution, use of near-field transmit antenna factor (NF-TAF) of small dipole antenna is proposed. NF-TAF can be expressed in closed form by assuming hyperbolic sinusoidal current distribution. Also, it can be evaluated by measuring S parameters between two identical dipole antennas and dielectric...
To design antennas for underwater communication systems using LF band, the transmission factor of dipole antennas with the sheath immersed in seawater are investigated by numerical study. Comparison of antenna characteristics between dipole antennas with different sheath structure is presented.
In 1998, JAMSTEC started the development project of the first prototype of a long-range cruising AUV (LCAUV) to evaluate fundamental technologies needed to travel through under the ice covered area of the Arctic. In 2005, The LCAUV, Urashima, achieved 317 km continuous cruising powered by a deep sea fuel cell developed in JAMSTEC [1]. We then moved to next stage and have conducted to design the second...
To evaluate specific absorption rate (SAR) of radio devices operated in MHz band, a small loop antenna can be used to calibrate a probe for estimating field intensity in the tissue-equivalent liquid. In our proposed method, field intensity radiated by a small loop antenna can be expressed in terms of its antenna factor in transmitting mode. In this paper, distance property of the antenna factor is...
To estimate SAR (specific absorption rate) of the wireless devices operated in HF band, the behavior of the near-field gain in the near-field region of the reference antennas operated in the tissue-equivalent liquid is required. Some asymptotic expansions of the near-field gain of the reference antennas are derived by using an integral form of the transmission coefficient between the antennas and...
It is required that specific absorption rate of mobile devices operated in HF band should be evaluated by using a calibrated probe. In this paper, we propose an extension of reference antenna method, which is one of methods for calibrating the probe. As a reference antenna, we examine a circular folded loop antenna immersed in normal saline solution. If its perimeter is well selected, constant near-field...
To calibrate an electric field prove for evaluating specific absorption rate (SAR) of wireless devices operated in the MHz band, we have proposed the use of circular loop antenna immersed in tissue-equivalent liquid. In our proposed method, near-field gain of the loop antenna should be evaluated to estimate the fields radiated by the loop antenna. However, there is a serious problem that its size...
To evaluate specific absorption rate (SAR) in HF band using reference antenna method, dielectric-coated and shielded loop antenna operated in the liquid can be used. It is found that the electric and magnetic field intensity in the near-field region of the reference antenna behave like corresponding far-field if the near-field gain have a plateau as a function of the distance from the antenna. To...
An insulated circular loop antenna (ICLA) immersed in tissue-equivalent liquid is one of candidates for reference antenna to calibrate probes which are used to evaluate SAR (specific absorption rate) for mobile communication devices operated in the MHz band. To clarify operation principle of ICLA immersed in the liquid, ICLA fed at a point along the loop is analyzed by the method of moments with characteristic...
Modal analysis on dipole antenna using method of moments and characteristic modes is used to evaluate the amount of the excitation for balanced and unbalanced modes. To separate the current on the antenna into the balanced and unbalanced modes, the current distribution is decomposed into even- and odd-symmetrical distribution with respect to reference plane. As a result, the power ratio of the unbalanced...
This paper presents measurement techniques to reduce sampling points in Total Radiated Power (TRP) measurement by spherical scanned probes. For the sampling point reduction, this paper presents modified equi-angle to eliminate the effect of metric coefficient and generalized spiral scanning to pick up measured data uniformly. Data reduction rate is discussed by the measurement results. In addition,...
A new technique for estimating far-field gain as well as phase center of antennas operated in liquid is numerically demonstrated. It is easily derived that the distance characteristic of near-field gain for antennas operated in the liquid is the same as that in free space. Moreover, another expression for the nearfield gain for antennas operated in the liquid that the authors have proposed is proven...
A method to evaluate reflection coefficients accurately by using a hybrid coupler and a sliding short is modified to save measurement time. For modified method, a digital phase shifter is used to vary the phase of reference standard. Radiation efficiency based on Wheeler method for a monopole antenna is evaluated by the modified method to confirm the effectiveness of using the digital phase shifter...
For calibrating electric-field probe to evaluate the value of SAR (specific absorption rate) for devices at a frequency of 30 MHz, a shielded loop antenna is used as a reference antenna. To facilitate curve fitting for the calibration, near-field gain should be constant near the loop. In this paper, it is shown that the circumference of the loop can be selected as the near-field gain becomes approximately-constant...
It is known that coupling between balanced and unbalanced modes on AUT (antenna under test), is calculated by using mixed-mode S parameters. In this paper, it is shown that the coupling can approximately be evaluated by proposed one-port measurement with a quadrature hybrid as well as two-port measurement for equivalent network of AUT.
As a reference antenna operated in the tissue-equivalent liquid at 30 MHz, where the wireless communication devices are used in Japan, an insulated circular loop antenna is useful for calibrating the electric field probe for evaluating the SAR (Specific Absorption Rate) of the devices. Its near-field gain and electric field intensity are numerically simulated by the mothods of moment so that the probe...
Wheeler cap method is known as a simple method for measuring the radiation efficiency of small antennas [1]. In this method, the radiation efficiency can be evaluated by using reflection coefficients when the antenna under test is located in free space and is covered with the shield. Also, it is known that the uncertainty of the measurement for the reflection coefficient using the vector network analyzer...
Recently, it has been expected that the wireless energy transmission system which uses the phenomenon of magnetic-field resonance will be launched and the methodology of estimating SAR (Specific Absorption Rate) for this system can be required. In this system, the distance that the energy can transfer between the transmitted and received equipments will be tens of centimeters. To estimate SAR for...
Improved Wheeler method is known as one of the simplest methods of measuring the radiation efficiency of the small antennas [1]. In this method, the reflection coefficients are required when the antenna under test (AUT) is located in free space and waveguide with both movable ends shorten, and the reflection coefficients in the waveguide with the shorts draw a circle on the reflection coefficient...
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