This paper presents the shadowing analysis of a body area network (BAN) diversity antenna based on the statistical measurements of the human walking motion. First, the dynamic characteristics of the arm-swing motion were measured using human subjects, and a statistical analysis was then carried out using the measured data to extract useful information for the analysis of a BAN diversity antenna. Second, the analytical results of the shadowing effects of the BAN antenna were shown based on the statistical data of the swing motion. The difference between the typical and the realistic arm-swinging models significantly affected the bit error rate (BER) characteristic of the BAN antenna. To eliminate the shadowing caused by the movement of the arms, a BAN diversity antenna was used. Particular emphasis was placed on the evaluation of the spatial separation of the diversity antennas to attain reduction of the signal-to-noise ratio (SNR) required to achieve a specific BER performance, considering the combined outcome of shadowing and multipath fading unique to BAN antenna systems. We determined that an antenna angle separation of greater than 80° is required to reduce the shadowing effects when the diversity antenna is mounted at the left waist in a symmetrical configuration. Further, an antenna angle separation of 120° is required when the diversity antenna is mounted in an asymmetric configuration.

This paper presents a basic investigation of the power imbalance problem with regard to maximum ratio combining (MRC) array antennas for digital TV broadcast reception. First, the relationship between the decrease in the diversity gain and reduction in the received power was investigated using two-element and four-element dipole array antennas by means of a Monte Carlo simulation. The relationship between the decrease in the diversity gain and the number of branches imposed to reduce the received power was also investigated. Then, a simple method of predicting the reduction in the diversity gain under imbalanced power conditions is given using the simulation results. The objective is to determine a criterion associated with the gain reduction that allows us to achieve the required system performance. Finally, the proposed method is confirmed by analysis using a model representing a typical portable digital broadcasting TV set held with both hands that simulates the power imbalance condition.

An RF adaptive array antenna (RF-AAA) configured with variable capacitors is proposed. This antenna system can control the power combining ratio and phase value of received signals. In this paper, we focus on the diversity effects of RF-AAA. First, we show the design methodology of the combiner circuit to realize the effective combining. Second, the perturbation method and the steepest gradient method are compared for the optimization algorithms to provide fast convergence and suboptimum solutions among the variable circuit constants. Finally, in simulation, we show the RF-AAA can achieve diversity antenna gains of 7.7 dB, 10.9 dB and 12.6 dB for 2-branch, 3-branch and 4-branch configuration, respectively, which have higher performance than the selection combining.

This paper reviews the antenna system for Japanese celullar systems and PHS (Personal Handphone System). The unique features of the Japanese cellualr system are multi-band operation, compact diversity antennas, electronic beam tilting, and indoor booster systems. The original antennas for the above purpose will be described. The PHS is also a unique mobile communication system in Japan, and is mainly used for high speed, low cost data transmission. Its original antennas are also presented in this paper.

A polarization diversity planar inverted-F antenna (PIFA) on portable telephone in the practical use near the operator's body is investigated at 1,800 MHz under multipath urban environment. The antenna structure comprises a center-fed square patch with one permanent short-pin and two RF-switches on three corners. The RF-switches perform as the polarization branch switches for dominantly vertical polarization (VP) or dominantly horizontal polarization (HP) modes. The radiation efficiency of the polarization diversity PIFA is 58% and 53% for VP and HP modes, respectively, which is higher than the 52% efficiency of the reference λ/4 monopole antenna under the same condition. The mean effective gain (MEG) of VP and HP modes decrease with respect to the increasing cross-polarization power ratio (XPR). The correlation coefficient of two diversity branches is between 0.66 through all the possible XPR ranging from -10 dB to +10 dB. The diversity gain is computed from the MEG and correlation coefficient to determine the diversity antenna gain (DAG). The diversity gain, based on 10-3 BER for selective combining, is 7.5 dB over non-diversity reception. The DAG is -1.2+2.8 dBi which is approximately 4 dB lower than the case without human body. In other words, the presence of the human body degrades the communication performance by a half.