Proper Power Level Research Articles

Outage Analysis of Alamouti-NOMA Scheme for Hybrid Satellite–Terrestrial Relay Networks

In this article, we investigate the performance of hybrid satellite–terrestrial relay networks with multiuser downlink nonorthogonal multiple access. The satellite applies Alamouti space–time block coding, and users exploit a receive antenna selection technique. Communication between the satellite and users is assumed to be established with the aid of a half-duplex terrestrial relay equipped with multiple receive antennas and operating in amplify-and-forward mode, because of the heavy masking effects attributed to environmental obstacles. Subsequently, the satellite–relay link is exposed to shadowed-Rician fading, whereas the relay–users links undergo Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> fading, which is a generic statistical channel model for nonterrestrial networks. To be more practical, we consider imperfect successive interference cancellation. The exact outage probability of each user and the corresponding asymptotic expression at the high signal-to-noise ratio are derived to demonstrate the system performance. The analysis indicates that the shadowing conditions do not affect the array gain when the diversity order is dominated by the multiantenna configuration of the second hop. The theoretical derivations are validated by using Monte Carlo simulations. The numerical results indicate that the proposed scheme significantly improves the performance of each user under various shadowing conditions. It also outperforms orthogonal multiple access when proper power levels are allocated to users.

A Soft-Switching Single-Stage Converter With High Efficiency for a 3.3-kW On-Board Charger

This paper presents a highly efficient 3.3-kW single-stage on-board charger (OBC). The proposed OBC consists of two interleaved cells sharing a full-bridge diode rectifier. Each cell is composed of an active clamp circuit and a series resonant circuit. The proposed OBC provides zero-voltage switching of all switches and reduces the reverse-recovery problem by zero-current switching of the output diodes. The interleaved technique maintains the proper power level with high efficiency. The proposed control algorithm enables power factor correction by the OBC without any auxiliary circuit and balances the input current between the two cells. In addition, the proposed converter requires no electrolytic dc-link capacitor, ensuring compact size and a long lifetime. Owing to these features, the proposed OBC efficiently outputs a high power factor over a wide power range and achieves reliability with a simply structured, single-power processing step. Therefore, the proposed OBC is potentially feasible for automotive applications. Finally, the theoretical analysis is confirmed in a 3.3-kW prototype and validated in experimental results.

Phase-Preserving Amplitude Noise Compression of 40 Gb/s DPSK Signals in a Single SOA

Wavelength-preserving and wavelength-converting amplitude regeneration of 40 Gb/s DPSK data in a saturated semiconductor optical amplifier (SOA) with limited excess phase noise feature is reported and investigated. By injecting simultaneously in the amplifier the noisy data and a CW beam with proper power levels, both the pass-through (PT) signal and the wavelength-converted data by four-wave-mixing (FWM) can be regenerated. The strongest regenerative effect is observed for the converted FWM data. The effect of input power variations on the regenerative performance of the device is thoroughly investigated in terms of Bit-Error Rate (BER) versus threshold margin improvement. We observe that regenerative behavior is attained for different levels of the data and CW power levels at SOA input. Experimental investigation of small-signal amplitude and phase SOA response reveals indeed the role of data/CW power balance for reducing the impact of excess phase noise from the amplifier. The analysis also confirms the stronger regenerative capability of the FWM process due to the strong amplitude-limiting SOA response at lower input data power in respect to the PT signal. The scheme offers the advantages of simplicity, compactness, and low operating power levels, making it a practical candidate for all-optical regeneration of high-speed DPSK signals.

Switching of ultrashort pulses in nonlinear high-birefringence two-core optical fibers

We analyze the switching characteristics of ultrashort pulses in a nonlinear high-birefringence two-core optical fiber by solving a set of four generalized coupled nonlinear Schrödinger equations. In such a fiber, the critical power required for activating switching changes significantly with the polarization angle of the input pulse and, as a result, a pulse at a proper power level can be switched between the two cores of the fiber by changing the input polarization angle. This provides a simple mechanism of achieving optical switching with the fiber. We also study the effects of the group-delay difference (GDD) between the two polarization components and the coupling-coefficient dispersion (CCD) in the fiber on the switching characteristics. The GDD tends to break up the two polarization components in the input pulse and thus leads to an increase in the switching power. A larger GDD, however, can give a sharper switching contrast when the input polarization angle is varied. The CCD tends to break up the input pulse and cause pulse distortion, regardless of the polarization, so it also leads to an increase in the switching power. Unlike the GDD, a large CCD always reduces the switching contrast. To achieve high-quality switching, the fiber should have a small CCD.

ZF-THP를 이용한 다중 안테나 다중 사용자 시스템에서 전송률 합 최적화를 위한 전력 할당 알고리즘

이 논문에서 우리는 Tomlinson-Harashima precoding (THP)를 이용한 다중 입력 단일 출력 다중 사용자 하향링크 시스템을 위한 전력할당 기법에 대해 알아본다. Zero-forcing THP 시스템의 sum rate를 최대화하기 위해 우리는 이전 방법과는 달리 mutual information 방법을 적용하였다. 나아가서, 모듈로 오퍼레이션을 사용하는 유저에 적절한 전력 레벨을 할당하기 위해 간단한 전력 할당 알고리즘을 제안한다. 실험 결과는 제안된 기법이 기존의 water-filling 기법보다 성능이 우수하고, 시스템의 최적의 성능을 내는 기법과 성능은 유사하면서 보다 작은 복잡도로 이루는 것을 보여준다. In this paper, we study a power allocation technique for Tomlinson-Harashima precoding (THP) in multi-user multiple input single output (MISO) downlink systems. In contrast to previous approaches, a mutual information based method is exploited for maximizing the sum rate of zero-forcing THP systems. Then, we propose a simple power allocation algorithm which assigns proper power level for modulo operated users. Simulation results show that the proposed scheme outperforms a conventional water-filling method, and it provides similar performance with near optimal method with much reduced complexity.

A Microwave Oven with Variable Continuous Power and a Feedback Temperature Controller

AbstractThe power supply circuit of a domestic microwave oven was modified so that the field intensity in the cavity could be changed continuously. The oven was further fitted with a feedback temperature controller for controlling product temperatures during microwave heating by cycling the magnetron on and off. The temperature controller consists of a fiber optic temperature sensing system, a computer, an optocoupler, and a mechanical relay. White bread, moist sponges, and a 5‐mL water load were used to test the performance of the oven. The temperature control capability was greatly influenced by the field intensity of the cavity and less influenced by the data acquisition rate. Experimental data indicated that it was possible to maintain the sample temperature within ±0.3°C at 60°C and within ±0.6 °C at 80°C when a proper power level was used.

The rapid synthesis of organic compounds in microwave ovens

This work demonstrates that organic compounds can be synthesized up to 1240 times faster in sealed Teflon vessels in a microwave oven than by conventional (reflux) techniques. It is shown that all polar molecules absorb microwave energy rapidly and that the rate of energy absorption varies with the dielectric constant. The rates of reaction of polar molecules in nonpolar solvents are not increased appreciably by the microwave method. Also, the homogeneity of the reaction does not affect the rate enhancement. The rate enhancement arises predominantly because the oven superheats the solvent rapidly. Finally, pressure (temperature) measurements have shown that the maximum rate enhancement is achieved when the proper power level and volume of solvent are used. It appears that rate enhancements of approximately 200 are possible for many reactions if the reaction conditions are optimized.