In the estimation of SAR (specific absorption rate) for a human phantom model, we proposed a method for using a double-loop probe to correct for the effects of the magnetic field reflected off the surface of the phantom. By comparing our experimental results with those obtained using an electric-field prove method, we were able to confim the accuracy of corrections made for the effects of a reflected magnetic field.

A low loss magnetic plate positioned near an antenna is proposed to increase radiation efficiency of cellular phones. This magnetic plate is used to control the nearby magnetic field around the cellular phone's antenna, and this field controlling is shown to be effective for the improvement of radiation efficiency and far-field pattern. As for the material design of the plate, a magnetic plate having high µr and low µr" (complex relative permeability: µr = µr - j µr") is found to be effective for achieving high performance. In our sample fabrication, a low loss magnetic sample with µr = 5.7 - j 0.7 at 900 MHz is realized. It is demonstrated that this low loss sample contributes to increased efficiency and improved far-field characteristics.

This paper describes an estimation method for an antenna current distribution including the interaction between a cellular telephone antenna and a human body. In our experiments, current distributions on a half wavelength dipole antenna at 900 MHz are evaluated by measuring the magnetic field near the antenna, when a human head-sized phantom model is located near the dipole antenna. From the experiments, the antenna current around a feed point is confirmed to increase by 30% due to the interaction effect. This result shows that antennas of portable phones should be designed by considering the effect of a human presence for the development of the higher performance antenna, and our estimation method will contribute to optimizing the design of such antennas.

A novel compact multi-input multi-output (MIMO) antenna system with split-ring resonator (SRR), a popular metamaterial structure, is presented. The MIMO antenna system consists of SRRs as radiator elements arranged close to each other on a printed circuit board. We evaluate the antenna characteristics with a single and two SRR elements arranged within various sizes of area. We also analyze MIMO channel capacities of SRR elements by using radiation patterns. The obtained results confirm that the proposed MIMO antenna system can achieve the same channel capacity as a conventional MIMO antenna system but with a 30% smaller footprint area and is very suitable for compact wireless equipment in next-generation wireless systems.

Substrate noise coupling in RF receiver front-end circuitry for LTE wireless communication was examined by full-chip level simulation and on-chip measurements, with a demonstrator built in a 65nm CMOS technology. A CMOS digital noise emulator injects high-order harmonic noises in a silicon substrate and induces in-band spurious tones in an RF receiver on the same chip through substrate noise interference. A complete simulation flow of full-chip level substrate noise coupling uses a decoupled modeling approach, where substrate noise waveforms drawn with a unified package-chip model of noise source circuits are given to mixed-level simulation of RF chains as noise sensitive circuits. The distribution of substrate noise in a chip and the attenuation with distance are simulated and compared with the measurements. The interference of substrate noise at the 17th harmonics of 124.8MHz — the operating frequency of the CMOS noise emulator creates spurious tones in the communication bandwidth at 2.1GHz.

In this paper the amplitude probability distribution (APD) measurement method is applied to evaluate noise coupling to an antenna on an evaluation board that uses mixed RF and digital signals of an IC. We analytically investigate noise coupling path to the antenna where the correlation coefficient matches the APD curve of the evaluation board. Moreover, in order to verify the analysis results, the noise coupling path in the board is evaluated by measurements involving In-phase/Quadrature (I/Q) signals as well as electromagnetic simulations. As a result, we demonstrate that APD method is effective in evaluating a degree of noise coupling from an IC to multiple antennas on the board, and confirm that the intensity of noise coupling to each antenna is affected greatly by the board layout patterns.