Applied Mechanics and Materials Vols. 427-429

Abstract: Amplify-and-forward (AF) orthogonal frequency division multiplexing (OFDM) relay systems without diversity are studied, with emphasizing on the subcarrier pairing at the relay node. Using the subcarrier pairing based on the signal-to-noise power ratios (SNRs) of subcarriers, it is proven that the ordered subcarrier pairing (OSP), according to normalized channel gains of the subcarriers of OFDM at two hops, is optimal in terms of system capacity, without any assumption for SNRs of subcarriers and types of power constraints. The proof about the optimality of OSP shows that in this kind of relay systems, the subcarrier pairing and power allocation are completely decoupled.

Abstract: Nonuniformity of Infrared Focal Plane Array (IRFPA) has greatly limited the quality of infrared imaging system, so nonuniformity must be corrected before using IRFPA. In order to reduce nonuniformity correction calculating amount and improve real-time nonuniformity correction speed, a new compressing correction method of utilizing hardware memory is presented. In this paper, memory compressing correction principle and implementing process are expounded in detail, and the hardware circuit diagram is given out. The experimental results prove that the method has simple circuit and excellent image quality and it easily realizes real-time nonuniformity correction.

Abstract: Filters between voltage source converter and the batteries in power system can be categorized into constant voltage source excited filters. The paper discusses the importance of the matched structure and parameters for power filters. The relation between matched structure and filters output characteristic is demonstrated and the design principle is introduced. The work above proved that even if the filters are designed for the same transfer function, so long as filters load resistance is different, their designed parameters are also different. Traditional power system filter seldom consider its both ends load matching characteristic. When the difference between filter's load characteristic and practical system equivalent impedance are large, the actual filtering effect becomes worse, current loss arises and even there may be the possibility of resonance. As the lack of energy resource and energy crisis is gradually becoming a serious problem, energy conservation is important. Constant voltage source excited circuit configuration model is established through the simulation and test. The results show the validity and feasibility of the method that filter should be designed the according to its load characteristic in practical application.

Abstract: Modern radar systems should transmit different waveforms according to different environment. Waveform design is an important problem in radar system design. In this paper, we compare two waveform design methods based on MI and SINR with the signal model of a Gaussian target ensemble in ground clutter. The simulation results show that for the different tasks of radar, the energy allocation modes are different. Finally, the whole paper is summarized.

Abstract: A 4-stage travelling wave amplifier with 10dB ± 1.2 dB gain and 12 GHz bandwidth is presented in the paper. The parameters of the small signal equivalent model about the GaAs PHEMT are extracted to evaluate the characterization of the device, which is also used to design the amplifier. The amplifier has a minimum noise figure lower than 4.8 dB in the frequency range, and the S₁₁ and S₂₂ are below-10 dB and-7 dB, which demonstrate a good performance. The P_1dB and IIP3 are 7.3 dBm and 24 dBm, respectively, and the saturation output power is above 20 dBm at 13 GHz.

Abstract: In this paper, global adaptive output feedback tracking problem is considered for a class of multivariable nonlinear systems with unknown parameters and nonlinear terms linear in unmeasured states. Based on a modified high-gain observer and Hurwitz assumption of high frequency gain matrix, an adaptive backstepping design is proposed, which is able to guarantee global stability of the closed-loop system and circumvent the over-parameterization problem raised by using conventional back stepping method.

Abstract: In this paper, Legendre orthogonal functions neural network is used to achieve the control of nonlinear systems. The adaptive controller is constructed by using Legendre orthogonal functions neural network. The adaptive learning law of orthogonal neural network is derived to guarantee that the adaptive weight errors and tracking errors are bound by using Lyapunov stability theory. Simulation results are given for a two-link robot, and the control scheme is validated.

Abstract: Based on the bloom filter and QR decomposition, a detection scheme against node replication attack in wireless sensor network was proposed. The scheme used the bloom filter to generate the geographic fingerprints of the nodes. According to the principle that the same ID cannot have two different geographical locations, when the receiver found the conflicting fingerprint, the node replication attack was detected. Matrix QR decomposition can guarantee the network security and provide verification of the link

Abstract: In this paper, a low temperature coefficient bandgap voltage (BGR) is designed for A/D converter by adopting piecewise-linear compensation technique. The designed BGR is analyzed and simulated in SMIC 0.18μm CMOS process. Simulation results show that the PSRR of the designed BGR achieves-72.51dB, -72.49dB, and-70.58dB at 10Hz, 100Hz and 1kHz respectively. The designed BGR achieve the temperature coefficient of 1.57 ppm/°C when temperature is in the range from-35°C to 125°C. When power supply voltage V_DD changes from 1V to 7V, the deviation of the designed BGR output voltage V_REF is only 4.465μV.

Abstract: In this paper, a sliding mode control (SMC) with a cooperative weights neural network (CWNN) is proposed to realize the synchronization of two chaotic Gyro systems with nonlinear uncertainties and external disturbances. By the Lyapunov stability method, the overall closed-loop system is shown to be stable and chaos synchronizationis obtained. The simulation results demonstrate the effectiveness of the proposed control method.