Correlation of maximum temperature increase and peak SAR in the human head due to handset antennas

This paper attempts to correlate the maximum temperature increase in the head and brain with the peak specific absorption rate (SAR) value due to handset antennas. The rationale for this study is that physiological effects and damage to humans through electromagnetic-wave exposure are induced by temperature increases, while the safety standards are regulated in terms of the local peak SAR. For investigating these correlations thoroughly, the total of 660 situations is considered. The numerical results are analyzed on the basis of statistics. We find that the maximum temperature increases in the head and brain can be estimated in terms of peak SARs averaged over 1 and 10 g of tissue in these regions. These correlations are less affected by the positions, polarizations, and frequencies of a dipole antenna. Also, they are reasonably valid for different antennas and head models. Further, we discuss possible maximum temperature increases in the head and brain for the SAR values prescribed in the safety standards. They are found to be 0.31/spl deg/C and 0.13/spl deg/C for the Federal Communications Commission Standard (1.6 W/kg for 1 g of tissue), while 0.60/spl deg/C and 0.25/spl deg/C for the International Commission on Non-Ionizing Radiation Protection Standard (2.0 W/kg for 10 g of tissue).     

Correlation between peak spatial-average SAR and temperature increase due to antennas attached to human trunk

This paper discusses the correlation between peak spatial-average specific absorption rate (SAR) and maximum temperature increase for antennas attached to the human trunk. Frequency bands considered are 150, 400, and 900 MHz, which are assigned for occupational communications. This problem is throughly investigated with the aid of Green's function. In particular, the effect of variation of thermal constants on the temperature increase is revealed by using one-dimensional model. Computational results suggests that one of the most dominant factors which affect the correlation between peak SAR and maximum temperature increase is blood flow in tissues. This is confirmed by considering a three-dimensional realistic human body model. Uncertainties caused by the calculation of peak SAR and the difference in the body model shape are also quantified.     

FDTD-derived correlation of maximum temperature increase and peak SAR in child and adult head models due to dipole antenna

This paper investigates the correlation between the peak specific absorption rate (SAR) and the maximum temperature increase in head models of adults and children due to a dipole antenna. Much attention is paid to the effect of variation of electrical and thermal constants on the correlation for the child models, since these constants of child tissues are different from those of adult tissues. For investigating these correlations thoroughly, a total of 1400 situations are considered for the following six models: 3-year-old child, 7-year-old child, and adult models developed at the Nagoya Institute of Technology and the Osaka the University. The numerical results are analyzed on the basis of statistics. We find that the maximum temperature increases in the head can be estimated linearly in terms of peak SAR averaged over 1- or 10-g of tissue. In particular, no clear difference is observed between the adult and child models in terms of the slopes correlating the maximum temperature increase with the peak SAR. Also, the effect of electrical and thermal constants of tissue on these correlation is found to be marginal. Further, we discuss possible maximum temperature increases in the head and brain for SAR limits prescribed in safety guidelines. For the adult model developed at the Osaka Univ., these are found to be 0.26/spl deg/C and 0.10/spl deg/C at the SAR value of 1.6 W/kg for 1-g cubic tissue and 0.59/spl deg/C and 0.21/spl deg/C at the SAR value of 2.0 W/kg for 10-g cubic tissue. Similarly, for the 3-year-old child model at Osaka Univ., these are 0.23/spl deg/C and 0.11/spl deg/C for the value of 1-g SAR and 0.53/spl deg/C and 0.20/spl deg/C for the value of 10-g SAR.     

A comparison between different polarimetric measurement schemes

The usefulness of polarization information in remote sensing applications has been clearly demonstrated in the last two decades. Land covers and meteorological targets are complex and their backscatter returns are time varying. Their polarimetric characteristics should be determined in terms of second order statistics of scattering matrix elements. These are contained. in the polarimetric covariance matrix. Estimation of polarimetric covariance matrix elements has been addressed by different authors based on different scattering matrix measurement methods. The most widely used and implemented method consists in the alternate transmission of two orthogonal polarizations while. receiving with both. Recently, a method that considers simultaneous transmission of two orthogonal polarizations, which are phase coded with orthogonal signals, has been proposed. Another method, specifically developed to obtain the polarimetric covariance matrix, is based on transmitting three different polarizations and receiving their corresponding co-polar and cross-polar counterparts. Different data sets result from each measurement technique and different estimators of polarimetric covariance matrix elements have been developed for the different data sets available. These various methods are investigated in here. Based on simulated data the performance of the different estimators under different working conditions are analyzed. Effects on the estimators of operation frequency, pulse repetition frequency (PRF) and temporal properties of targets are discussed     

High average and high peak brightness slab laser

A high average and high peak brightness Nd:YAG MOPA laser system composed of a laser-diode-pumped Nd:YAG master oscillator, flash-lamp-pumped slab power amplifiers and a phase conjugated mirror was developed. The system demonstrates an average output power of 235 W at a repetition rate of 320 Hz and a peak power of 30 MW at a pulse duration of 24 ns with M²=1.5. Both an average brightness of 7×10⁹ W/cm²·sr and a peak brightness of 1×10¹⁵ W/cm2·sr are achieved simultaneously. The system design rules that we confirmed suggest that by replacing lamp pumping in the amplifier with laser-diode pumping, an average output power of ~1 kW can be obtained at ~1 kHz with a higher average brightness of ~3×10¹⁰ W/cm²·sr and a higher peak brightness of ~3×10¹⁵ W/cm²·sr     

FEM modeling of SAR distribution and temperature increase in human brain from RF exposure

The assessment of radiofrequency exposure level and the exposure setup are critical, because if the exposure levels (related to frequency, power, position, and other variables) are not known, the biological results are not meaningful. In this regard, this study aims to design, implement, and analyze numerical setups for the simulations of radiofrequency exposure related specific absorption rate and temperature increase in the human brain and head. For this purpose, specific models for human head and telephone antenna are chosen, and the FEM is selected for solving PDEs related to electromagnetic wave equations and bioheat equation. After the verification of the methodology chosen by achieving comparable results with the literature, the scope of the study is then turned to the effects of different parameters on the exposure levels. In the end, comprehensive information can be obtained from the simulation results so that risk management policies for electromagnetic radiation can be reevaluated to minimize the possible health hazards. Copyright © 2012 John Wiley & Sons, Ltd.     

SAR and temperature increase in the human eye induced by obliquely incident plane waves

Specific absorption rates (SARs) and temperature increases in the human eye are calculated for exposure to obliquely incident plane waves in the frequency range of 600 MHz and 6.0 GHz. The average SARs and the temperature increases in the lens are found to take maximum values only in the hot-spot frequency range for oblique incidence (30/spl deg/-50/spl deg/).     

慢符号速率低峰均比调制与信噪比关系的仿真研究

根据无线收发信机的工作原理,设计了慢符号速率调制信号经过各种环境的无线传输后误码率和信噪比变化的仿真原理结构,并应用理论公式和实际例子分析差分算法最适合慢符号速率低阶调制信号的解调.在时域同步和不同步的两种情况下,分别针对慢符号速率信号用GMSK和OQPSK低峰均比调制后经过4种不同的无线通信环境的仿真,详细分析了解调后信号误比特率和信噪比的关系,最后总结并比较了GMSK和OQPSK调制对信噪比的要求和对放大器工作效率的不同.     

Simultaneous peak and average power minimization during datapath scheduling

In low-power design for deep submicrometer and nanometer regimes, peak power, power fluctuation, average power, and total energy are equally important design constraints. In this paper, we propose datapath scheduling algorithms for simultaneous minimization of peak and average power. The minimization schemes based on integer linear programming are developed for the design of datapaths that can function in three modes of operation: 1) single supply voltage and single frequency; 2) multiple supply voltages and dynamic frequency clocking (MVDFC); and 3) multiple supply voltages and multicycling. The techniques are evaluated by estimating the peak power consumption, the average power consumption and the power delay product of selected high level synthesis benchmark circuits for different resource constraints. Experimental results indicate that combining multiple voltages and dynamic frequency clocking as in the MVDFC scheme, yields significant reductions in the peak power, the average power, and the power delay product.     

Correlation between hot-carrier-induced interface states and GIDLcurrent increase in n-MOSFET's

Correlation between created interface states and GIDL current increase in n-MOSFET's during hot-carrier stress is quantitatively discussed. A trap-assisted two-step tunneling model is used to relate the increased interface-state density (ΔD_it) with the shift in GIDL current (ΔI_d). Results show that under appropriate drain-gate biases, the two-step tunneling is so dominant that ΔI_d is insensitive to temperatures up to about 50°C. With the help of 2-D device simulation, the locations of the drain region with significant two-step tunneling and the energy levels of the traps involved can be found, with both depending on the drain voltage. From these insights on ΔD_it, ΔI_d and their relation, ΔD_it near the midgap can be estimated, with an error less than 10% as compared to the results of charge-pumping measurement on the same transistors. Devices with nitrided gate oxide, different gate-oxide thicknesses and different channel dimensions are also tested to verify the above correlation     

Measuring peak and average power of digitally modulated advancedtelevision systems

The author reviews why it is that the peak power of the NTSC visual signal is measured, noting that its average power varies inversely with scene brightness. The average power of a digital TV signal is independent of scene content, motion, and other variables and is, therefore, the parameter to be measured and used to compute interference, coverage, and the utility cost to provide that coverage. Transient peak power varies with the data stream, and for this reason it is a statistical quantity. A method to determine the transient peak power is described. Thermocouple power sensors and the limitations of square law power sensors are also discussed     

A novel trellis-shaping design with both peak and average power reduction for OFDM systems

A new trellis shaping design is proposed for reducing the peak-to-average power ratio of the bandlimited orthogonal frequency-division multiplexing (OFDM) signals. The approach is based on recursive minimization of the autocorrelation sidelobes of an OFDM data sequence. A novel metric in conjunction with the Viterbi algorithm is devised. The performance of the trellis shaping depends on signal mapping strategy, and the two types of mapping, referred to as Type-I and Type-II, are proposed. The Type-I mapping has no capability of reducing the average power, but it can achieve a significant reduction of the peak-to-average power ratio. On the other hand, the Type-II mapping is designed to achieve both peak and average power reduction. The bit error probability of the system over an AWGN channel is evaluated based on the simulations, which confirms the effectiveness of the proposed scheme.     

Radar signal design subject to simultaneous peak and average power constraints

Optimal amplitude modulations for a radar signal are derived and then used to calculate the efficiencies of various sub-optimal modulations. The choice of modulation is constrained by the total energy transmitted and the peak power (amplitude) of the transmitted signal. The peak power constraint is handled by the use of Pontryagin's Maximum Principle, an extension of the calculus of variations recently developed in the U.S.S.R. that is enjoying wide application in optimal control theory. The criterion of optimality is based on the error variances of estimates of the range motion parameters of a reflecting body, where the errors are caused by additive, white, zero mean, Gaussian noise. Explicit results are provided for bodies with constant velocity and bodies with constant acceleration. The analysis covers: 1) incoherent processing of a sequence of many range measurements; 2) coherent processing assuming the RF phase is known, 3) certain aspects of coherent processing assuming the RF phase is unknown. The optimal modulations turn out to be of the "on-off" type, requiring either no transmission or transmission at the maximum allowable power level.     

Power adaptation for BPSK signaling with average and peak power constraints in Rayleigh fading channels

We consider power adaptation strategies for binary phase-shift keying signals in Rayleigh fading channels under the assumption that channel state information is provided at both the transmitter and the receiver. We first derive a closed-form expression for the optimal power adaptation that minimizes average bit-error rate (BER) subject to average and peak transmission power constraints. Then, we analyze the average BER for channel inversion power adaptation with the same constraints. Our results show that the performance difference between the optimal power adaptation and the channel inversion becomes negligibly small as available average transmission power increases and/or peak-to-average power ratio decreases. We also find that an optimal peak-to-average power ratio exists that minimizes the average BER in the channel inversion scheme.     

Influence of high-level synthesis on average and peak temperatures of CMOS circuits

The aim of this paper is introducing a new modified high-level synthesis (HLS) technique resulting in reduction of the power dissipation in CMOS circuits leading to lowering the peak and the average temperature of the designed chip. The presented approach enables us designing contemporary electronic systems with reduction of the peak and average power consumption, so the reliability of the system can be improved. In the present method, the initial HLS is performed by the ASAP algorithm [The Synthesis Approach to Digital System Design, 1992]. In the next stage, acceptable increase of the toggling time of chosen functional units (without exceeding the system throughput — the latency is constant) leads to the possibility of decreasing their supply voltages. These chosen functional units are determined by the inserting idle operations with interchanging (IIOI) algorithm. This approach leads to decreasing the power dissipated in the chosen functional units and finally their peak and average temperature is lowered.     

Digital Laguerre filter design with maximum passband-to-stopband energy ratio subject to peak and Group delay constraints

In this paper, we formulate a general design of transversal filter structures with maximum relative passband-to-stopband energy ratio subject to complex frequency response constraints in the passband and the stopband as well as additional constraints such as constraints. These constraints are important for applications where the suppression of noise at certain frequencies are important. Additional constraints are introduced allowing approximately linear phase and constant group delay in the passband. For a given set of basis functions, the design problem can be formulated as a semi-infinite quadratic optimization problem in the filter coefficients, which are the decision variables to be optimized. In this paper, we focus on the design of digital Laguerre filter and digital finite impulse response (FIR) filter structures. A modified bridging algorithm is developed for searching for the optimum pole of the Laguerre filters. Design examples are given to demonstrate the effectiveness of the proposed algorithm.     

不同调制方式下高斯信道容量的计算

计算不同调制方式下的信道容量对实际通信系统的信道编译码设计具有重要的理论意义。首先从Shannon信息论出发,介绍了平稳无记忆连续信道与加性白高斯噪声信道容量的定义。接着利用互信息与微分熵的相互关系,推导了几种常用的不同调制方式下高斯信道的容量,并给出了相应的信道容量闭合计算表达式。通过将电力卫星通信信道模拟为高斯信道,对采用无速率信道编码联合不同调制方式的卫星通信进行了数值仿真。仿真结果显示,通过推导得到的闭合表达式计算信道容量,能对实际卫星通信的编码速率、译码启动条件的确定起到很好的理论指导作用。     

Correlation between reliability and oxidation temperature for ultra-dry ultrathin silicon oxide films

The correlation between time-dependent dielectric breakdown lifetime and oxidation temperature of 800–950°C for 3.5 and 5.0 nm thick silicon oxide films as gate insulators was investigated. To obtain ideal gate oxide films with few hydrogen-related defects and precise thickness distribution that extremely influence the lifetime, metal-oxide semiconductor diodes with the films used in the evaluation were produced by our continuous ultra-dry process. The films oxidized at 850°C showed the largest lifetimes irrespective of thickness. The enhancement, however, was confirmed only in the diodes selecting the oxidesilicon substrate interfaces as the anode-side, where the lifetime is mainly dominated. Interestingly, a similar relationship was observed in their density characteristics. This suggests that the condition near the oxide-silicon substrate interfaces is probably improved by the 850°C oxidation due to microscopic structural changes.     

基于条带式SAR与聚束式SAR内在联系的SAR成像研究

针对条带式合成孔径雷达（stripmap sar）与聚束式合成孔径雷达（spotlight sar）的方位向频谱结构,讨论了两种模式SAR之间的区别与联系,利用两者之间的内在联系,提出斜视条件下将条带式SAR数据分块,进行聚束式处理的方法,并对聚束式成像区域大小参数的选择进行了分析.对于相同尺寸的成像区域,对条带式SAR进行聚束式处理可以减小运算量.采用空间频率插值成像算法实现了条带式SAR与聚束式SAR成像算法上的统一,最后应用外场实测数据完成成像,成像结果证实了理论分析的正确性.     

Capacity of multiuser diversity systems with adaptive transmission and different MIMO schemes

In this paper, we present a comprehensive capacity analysis of the downlink of multiuser diversity (MD) systems with adaptive transmission over Rayleigh fading channels. First, the exact capacity of the single‐input single‐output (SISO) systems with MD and adaptive transmission technique is derived. The optimal power allocation scheme for such a system is shown to be a water‐filling algorithm. Next, we derive the exact closed‐form capacity expressions for different multiple‐input multiple‐output (MIMO) schemes, including the selective combining (SC), maximum ratio combining (MRC) and space‐time block codes (STBC). In order to avoid the cumbersome numerical root finding techniques in solving the optimal cutoff SNR level below which the channel is not used, we also provide the approximate expressions for the cutoff level. For the MD MIMO systems, it is observed that the optimal power allocation strategy is to focus transmit power on a single transmit antenna (e.g. Tx‐MRC/Rx‐MRC scheme) or selecting the best transmit antennas (e.g. Tx‐SC/Rx‐MRC scheme). Copyright © 2007 John Wiley & Sons, Ltd.