Broadband power-line communication using turbo codes and orthogonal frequency division multiplexing (OFDM) is considered in this paper. It is shown that the performance of conventional turbo coded OFDM systems degrades substantially due to the impulsive noise interference commonly encountered in power-lines. A robust turbo coded OFDM transceiver applying an iterative noise cancellation technique is proposed. Simulation results show that the proposed scheme is robust to impulsive noise while maintaining excellent performance in Gaussian noise.
A new fuzzy weighted average computation algorithm (NFWA) based on the α-cuts representation of fuzzy numbers is presented in this paper. For each α-cuts, the endpoints of the fuzzy weighted average (FWA) can be calculated from two particular switch points. In the proposed algorithm, these two switch points are computed with an opposite direction searching process, although recursive, which is remarkably efficient. The calculation complexity of the new algorithm is O(n). Experimental result demonstrates that compared with some commonly used FWA algorithms, the new algorithm approach requires the least CPU time, and then may be the fastest available FWA algorithm to date.
A group shuffled belief propagation (GSBP) decoding for punctured low-density parity-check (LDPC) codes is proposed in the paper. The proposed GSBP decoding schedules the updating order of each bit node according to its recovery order in the standard BP decoding. This enables the proposed decoding to recover all punctured nodes in the first iteration with the minimum required number of groups. Calculation of the number of effective updates, which indicates the number of nonzero check-to-bit messages, shows that the proposed decoding can achieve faster decoding convergence than the layered BP (LBP) decoding for rate-compatible punctured LDPC (RCP-LDPC) codes. In the simulation results, the maximum SNR gain of the proposed decoding over the LBP decoding is about 0.9dB at the FER of 10-4.
This paper proposes a bistatic High Frequency Surface Wave Radar (HFSWR) system for ocean current mapping. This system is composed of two remote sites. Both receive backscattered echoes as well as bistatic echoes transmitted by the other. An experiment was conducted on the coast of the North China Sea during January 2010, which proved effectiveness of the radar system.
The paper presents the waveform analysis and parameters design involved with range resolution, maximum detect range, transmit interval and receive interval, in phase-code interrupted continuous wave (PCICW) radars. More attention is paid to the effect of transmit/receive gating. Range blinds are avoided by ensuring the pulse travels to and from the maximum detect range before the next pulse is emitted. It is shown that certain complementary sets with column orthogonality are adequate for our applications. Although the echo is partially suppressed by the gate, the compressed output retains zero range sidelobe performance. Simulation demonstrates that P4 codes are insentivity to Doppler effect in PCICW radars so it can simplify the receiver complexity, and the experiment shows that the sidelobes level are -90dB compared to the mainlobe.
InAlAs/InGaAs/InP high electron mobility transistors have higher mobility comparing to structures without indium. But existence of indium causes smaller Eg and as a result smaller breakdown voltage. However, increasing percentage of indium results in higher mobility and as a result higher current and transconductance. Therefore decreasing percentage of indium causes higher breakdown voltage at the sometime lower transconductance. One of the most important parameters that limit maximum output power of transistor is breakdown voltage. In this paper, InAlAs/InGaAs/InP HEMTs with different structures are simulated and a structure with a good transconductance and breakdown voltage is introduced.
A new wideband Orthogonal Frequency Division Multiplexing (OFDM) receiver based on split spectrum processing (SSP) technique is presented. In this receiver, the spectrum of the input signal is first decomposed into a number of sub-bands, and then independently down-converted to baseband for filtering and demodulation. This technique, which is characterized by the number of sub-bands and their bandwidths, reduces the sampling rate of analog-to-digital converter (ADC) by the sub-band bandwidth compared to conventional OFDM system. Analysis and simulation of the phase noise show that the new receiver exhibits the same bit error rate (BER) performance as the conventional OFDM system. Also, the Chebyshev II filter gives rise to superior BER performance compared to Butterworth, Chebyshev I, Elliptic, and Bessel filters. Interestingly, the traditional time domain synchronization algorithms can be employed for the new SSP receiver with only minor modifications.
This paper proposes a shortened transmit technique using repetitive transmission in the frequency domain. For a single antenna OFDM system, a hybrid selection combining and maximum ratio receive combining technique was proposed for better performance, but it is effective only for high Eb/N0 region. This paper suggests a new method of removing zeros generated from repetitive transmission and of reconfiguring repetitive transmit time domain signals for maximum ratio receive combining at the receiver, by which we can obtain better performance comparing to SISO case at the expense of a few algebraic calculations and FFT/IFFT executions.
We propose a behavioral model of unipolar resistive RAMs (ReRAMs). The model integrates three behavioral characteristics of unipolar ReRAMs; i.e., i) ON/OFF resistive switching characteristics for transient voltage pulses, ii) I-V characteristics exhibiting ON/OFF resistive switching with current compliance, and iii) current-compliance dependence of both ON resistance and OFF threshold currents. The model is described by three nonlinear differential equations with several static functions, which enables us to employ the model in any numerical or circuit simulator. As an example, we integrate the model on HSPICE, and show the simulated results using experimental parameters extracted from fabricated ReRAMs of TiO2 thin films.
We investigated the properties of pulse propagation on nonlinear traveling-wave field effect transistors (TWFET) in order to develop a method for generating short electrical pulses. We considered the case where a decreasing voltage pulse is applied to the gate line and an increasing one is simultaneously applied to the drain line. By properly designing the top and bottom levels of the applied pulses, every FET simulates an electronic switch (the switch is open for voltages greater than some fixed threshold, and closed otherwise). On a line with such switches, a pulse experiences great shortening by the development of steep exponential wave; therefore, a TWFET operates as a short pulse generator.
In this paper a novel current conveyor with high functionality is proposed. The current conveyor utilizes a four quadrant current multiplier which can be used as a programmable gain amplifier in addition to current multiplication, which enables the device to function in both linear and non-linear regions. The correlation of the ports was optimized so that all of them would perform as input and output ports that are suitable for programmable applications. The current conveyor was implemented in 0.18µm CMOS process with a ±0.9v voltage supply. The results were obtained by Hspice and with a high detailed transistor library.
This paper presents the Q factor for use in Adler's formula to estimate locking range of oscillators. We extend it to arbitrary circuit topology, and take into account not only resonator but the entire network. The results show that, even for the same topology, Q differs if we change the port of injection or the active device's property. Since the theory is described in linear Z(ω) matrix domain, it gives oscillator designers a clear vista on their practical circuits.
Various handheld devices, in the first place mobile phones, have strong needs regarding 2D vector & bitmap graphics capabilities, including high performance and quality requirements. OpenVG is one of widely used low-level 2D vector graphics API's. Currently, fully dedicated OpenVG semiconductor chips are relatively expensive and require high power consumption. In contrast, full software implementations show lower performance even with almost 100% of CPU usage, which would disrupt other concurrent applications. In this paper, we present a new cost-effective way of accelerating OpenVG, based on wide-spread and inexpensive multimedia-processing hardwares, presently on the mobile phones. Through an extensive use of these multimedia processors, we successfully accelerated our AlexVG, an OpenVG software-based implementation, especially on its fundamental OpenVG features: bit-block transfer, masking, scissoring, color conversion, image transformation, etc. This accelerated implementation comes with a lower power consumption. It exhibits appropriate performance, reaching more than 20 frames per second, even for complicated graphical user experiences. Its CPU utilization ranges from 20% to 30%, while the remaining CPU power remains available for other real-time tasks and user applications. This implementation is now commercially available and used in several mid-tier mobile phones.
We investigated the source-to-drain capacitance (Csd) due to DIBL effect of silicon nanowire (SNW) MOSFETs. Short-channel SNW devices operating at high drain voltages have the positive value of Csd by DIBL effect. On the other hand, junctionless SNW MOSFETs without source/drain (S/D) PN junctions have negative or zero values by small DIBL effect. By considering the additional source-to-drain capacitance component, the accuracy of a small-signal model was significantly improved on the imaginary part of Y22-parameter.
A 1.0µm-band supercontinuum (SC) with a flat spectral bandwidth of 6.0nm is generated using a seed pulse source consisting of a CW light source, a phase modulator and a dispersion medium. And we use a photonic crystal fiber (PCF) as the nonlinear medium. PCF can be designed to realize high nonlinearity and low dispersion in the 1.0µm band. Moreover, we showed that we could fine-tune the optical spectrum of the SC by changing the modulation index Δθ of the phase modulator in the seed pulse source. We also describe the application of the supercontinuum as a multi-wavelength pulse source in the 1.0µm band.