Tasuku Morooka

Efficiency improvement of wireless power transfer via magnetic resonance using transmission coil array

The transfer efficiency between a transmission coil and a reception coil for wireless power transfer via magnetic resonance is a function of the orientation between the coils. When two coils share a single axis, the transfer efficiency is maximal, but otherwise the efficiency becomes lower. In this paper, a wireless power transfer system via magnetic resonance using a transmission coil array is proposed to improve the transfer efficiency. The transmission coils of the array are excited with appropriate phase weights by transmission circuit, according to the orientation among the transmission coils and the receiving coil. The effect of the proposed system is confirmed by simulation by a method of moment and measurement using a vector network analyzer.

A triangular loop antenna mounted adjacent to a lossy Si substrate for millimeter-wave wireless PAN

Millimeter-wave wireless communication is expected to be used for wireless personal area network (WPAN) for which a bit rate of 1Gbps or more is needed. Our goal is the development of an antenna suited to a WPAN terminal. Since a small, low-cost antenna with high radiation efficiency and a high gain in a wide- angle range is required for WPAN, the beam scan becomes unnecessary. In this paper, we propose a novel triangular loop antenna with a simple structure which has a feed point on to a semiconductor substrate.

Radiation efficiency measurement method for electrically small antennas using radio wave scatterers

The radiation frequency of a small built-in antenna in portable radio equipment could not be measured accurately because of the nearby electric parts and the human body. A description is given of a measurement method taking account of these influences. The authors devise a modified version of the random field measurement (RFM), which is based on the assumption that the cumulative probability of reception should be the same for both the unknown and the reference antennas. This method has an advantage of being able to measure the radiation efficiency including the effects of the human body. Experimental results using the indoor RFM are presented and some inherent problems with this measurement scheme are discussed. An alternate method of using radio wave scatterers surrounding the transmitting antenna is proposed to improve the accuracy of the measurement.<<ETX>>

Bonding wire loop antenna built into standard BGA package for 60 GHz short-range wireless communication

The unlicensed 60 GHz frequency band is suitable for high-speed wireless systems with transmission rates of 1 Gbps or more. In this paper, we propose a bonding wire antenna built into a BGA package for 60 GHz short-range wireless communication. This antenna utilizes two bonding wires and a metal plate on an interposer in a BGA package and has a loop shape. The proposed antenna is built into a standard BGA package without special modification, so that it can be fabricated at low cost by conventional BGA package fabrication process. The first and unique evaluation of the antenna fully sealed by encapsulation resin was done by measurement. We describe the operation mechanism of the proposed antenna, the design procedure and the measurement results.

Low profile double resonance frequency tunable antenna using RF MEMS variable capacitor for digital terrestrial broadcasting reception

It is difficult to realize the built-in antenna for wideband systems, because a frequency bandwidth of the low profile antenna is narrow. A frequency tunable antenna is a technique for wideband characteristics. In this paper a low profile double resonance frequency tunable antenna using MEMS variable capacitors is presented. It has high efficiency over a wide frequency band. Through both resonant portions from 465 to 665 MHz, the efficiency of more than −4 dB and the VSWR of less than 3 are observed in the measurement using the variable capacitor of 0.4–0.9 pF.

Scanning limitation in adaptive superresolution array

A fundamental limitation in an adaptive superresolution array, due to reciprocity between the angular resolution capability and the measurement time required, is discussed. For this purpose, a new concept for the measurement time, a scanning time concept, is introduced by considering a superresolution array consisting of an Applebaum-Howells adaptive processor with steering signal changing periodically with time. The measurement time is defined as the amount of time taken to perform one observation over the range of desired angle. Superresolution array output is defined according to the adapted angular response formulation. It is shown that the relationship between the resolution capability and the scanning time is reciprocal, i.e., the increased angular resolution is obtained at the expense of the scanning time. The relationship is discussed quantitatively for a narrow-band signal model.

Novel small structure for low profile antenna by analogy with EBG structure

By using the image theorem, the relation between the reflection phase of an infinite plane and the input impedance of the dipole antenna just above the plane has been discussed. It has been confirmed that the dipole antenna matches with 50 Omega when the reflection phase is around pi/2, and it is similar to the dipole antenna above an EBG structure. We have proposed the novel small structure which enables the dipole antenna to lay in low profile to the ground plane. The proposed structure rotates the reflection phase through a frequency band and the dipole antenna just above the structure matches with 50 Omega when the reflection phase is around pi/2. It is concluded that the periodicity of an EBG structure is NOT indispensable to realize a low profile antenna.

A study on loop antenna with uniform current distribution

A new antenna concept is proposed to improve and stabilize performance at the talk position of cellular telephones. Constant vertical average gain which is independent of its tilting angle and suppressed radiation toward an operator side can be realized by loop type antennas with uniform current distribution. The proposed square antenna of 0.54 /spl lambda/ circumference length with distributed capacitances is measured. Predictable results are obtained.

Two methods for estimating the diversity characteristics of built-in antennas for mobile communication equipment

In mobile communications, the diversity technique plays a very important role in improving the quality of digital transmissions, and the fading simulator is widely employed to achieve a quasi-fading environment. However, the fading simulator cannot be used to evaluate the effects of the antenna radiation patterns on the diversity characteristics. It is very difficult to predict analytically the radiation characteristics of built-in antennas in portable radio equipment, because they are affected by nearby electrical devices. Therefore, an experimental investigation is important. We proposed two measurement systems for evaluating the radiation characteristics of built-in antennas for hand-held radio equipment. Two methods for estimating the diversity characteristics of mobile communication equipment using these two measurement systems are presented.

A systolic array architecture for the Applebaum-Howells array

A systolic array architecture for the Applebaum-Howells array is derived. The problem to be solved is the elimination of the global signal feedback loop in the conventional Applebaum-Howells array processor. The procedure involved in deriving the architecture consists of two steps: orthogonalization of the input element signals and elimination of the feedback loop. In the first step, the input element signals are orthogonalized with regard to each other by using the Gram-Schmidt processor, placed ahead of the Applebaum-Howells processor. It is shown in the second step that the orthogonality in the Gram-Schmidt processor output signals can remove the global signal feedback loop and that the Applebaum-Howells array can be implemented effectively by using a systolic array with regular structure and local communication. Simulation results also show that the proposed processor features desirable characteristics for the radiation pattern with low sidelobe level common to the Applebaum-Howells array. >