In this paper the novel method of "weighted OFDM" is addressed. Different types of weighting factors (including Rectangular, Bartlett, Gaussian, Raised cosine, Half-sin and Shanon) are considered. The impact of weighting of OFDM on the peak-to-average power ratio (PAPR) is investigated by means of simulation and is compared for the above mentioned weighting factors. Results show that by weighting of the OFDM signal the PAPR reduces. Bit error performance of weighted multicarrier transmission over a multipath channel is also investigated. Results indicate that there is a trade off between PAPR reduction and bit error performance degradation by weighting.

This paper proposes radio resource control scheme for ABR service that execute flow-control on the transmission rate and assignable bandwidth according to the congestion conditions in both wireless and wired networks. The proposed scheme is useful in improving frequency utilization and meeting the QoS requirements. There are two methods to realize the proposed scheme: explicit rate control (ERC) and binary control (BC). We estimate the performance of the proposed scheme by simulation in comparison with a scheme without flow control in a wireless network under the conditions of a finite buffer, wired network congestion, and RM-cell errors. Consequently, we confirm that the proposed scheme is more effective than the scheme without flow-control under all service conditions. In addition, we clarify that both ERC and BC are effective under the conditions of a finite buffer, wired network congestion, and RM-cell errors.

We examine the detection of coded hybrid direct-sequence frequency-hopped spread-spectrum signals in the presence of narrowband interference. Since blind interference suppression requires a reliable estimate of the data, while at the same time data decoding requires interference suppression, we advocate an iterative ("turbo") detection scheme whereby information is exchanged between the interference suppressor and the soft-input soft-output decoder. Several suppression schemes are examined and compared. Simulation results show that this new scheme is robust, i.e., exhibits good performance under a modicum of assumptions on the interference structure. Turbo codes and convolutional codes are compared, showing that the former perform better.

A simple but efficient method to improve readability of discrete pseudo time-frequency representations (TFRs) of nonstationary signals by the reassignment of the representations in discrete frequency dimension is presented. The method does not rely on the nonzero time derivative of the window function employed in the estimation of pseudo TFR. This property of the reassignment method is advantageous because the method can provide an improved readability in the situation when a known reassignment method is unefficient. The reassignment of the TFRs of corrupted signals is discussed. Numerical examples are included to illustrate the performance of the proposed method.

There are methods used to test the optical purity of enantiomers; however, most of the simple methods are not precise and more complicated methods are better. As a result, these methods cannot be widely used for industrial purposes. The aim of this research is to design a sensor which can discriminate D-amino acids from L-amino acids. The designed sensor has chiral membranes and uses the technique of impedance change of these chiral membranes to discriminate the amino acids. We used a noise-FFT (Fast Fourier Transform) technique to determine the membrane impedance. When an enantiomer membrane resides in a chiral environment, (E*), diastereomeric interactions (E*-D) and (E*-L) are created, which may differ sufficiently in the arrangement of molecules of the membranes so as to permit the discrimination of optical substances due to the change in membrane characteristics. With increasing concentrations of the amino acids, the membrane resistance changes depended on the optical activity of the amino acids. The results suggest that the impedance changes of the chiral membrane with diastereomeric reaction can be used for the high-performance chemical sensor to measure the optical purity of different substances.

The orbital portrait of quasi-periodic oscillation shows transition like change with the amplitude of external force in periodically forced van der Pol oscillator. This phenomenon originates from frequency pulling between self-sustained and periodic external oscillations induced by the frequency shift of former. We estimate this shift and succeed in deriving the transition points at which the portrait changes.

In this paper, we propose a combination system of point to multipoint (P-MP) time division multiple access (TDMA) broadband wireless access (BWA) system and indoor wireless local area network (WLAN). In order to realize a high speed wireless communication, a wide bandwidth is required for both access lines and local area networks. The proposed system shares the frequency between BWA and WLAN to achieve an efficient use of frequency resources. This is based on the idea that an uplink band of the P-MP TDMA BWA system will provide relatively small interference slots, which are not used by subscriber stations nearby. In other words, there are useful small interference slots for another system using same frequency according to its position. Then we use such small interference slots for WLAN. In addition, direct sequence code division multiple access (DS-CDMA) can suppress such TDMA interference by spreading it over wide bandwidth. Therefore in the proposed system, DS-CDMA is used for WLAN in the same band with the BWA uplink. We also discuss WLAN packet error rate reduction techniques for this system. To confirm the availability of the proposed system, we evaluate the system performance by numerical analysis and computer simulation.

In this paper, a new frequency transformation for complex analog filter design which is suitable for integration is discussed. Arbitrary specified passband and stopband edges are easily transformed into those of the normalized LPF by solving simultaneous equations with four unknowns. Different from previous methods, the proposed transformation provides better performance in active realization of complex filters.

This paper describes a CORDIC-based direct digital frequency synthesizer in comparison with a ROM-based architecture. To optimize the hardware design parameters, we perform numerical analysis of the quantization effects for ROM and CORDIC-based architectures. The hardware costs of them are estimated in FPGA, which shows that the CORDIC-based architecture becomes better than the ROM-based when the required accuracy is 9 bits or more.

We propose a novel adaptive multiple-symbol differential detection (MSDD) scheme that has excellent performance over frequency selective fading (FSF) channels. The adaptive MSDD scheme consists of an adaptive noncoherent least mean square channel estimator that can accomplish channel estimation without any decision delay and the MSDD. The M-algorithm is introduced into this detection scheme to reduce the complication of computation due to increasing observed sequence length in the MSDD. Because of the application of the adaptive channel estimator and the M-algorithm, this adaptive MSDD make it possible that channel estimation is accomplished for every symbol along M surviving paths without any decision delay. And the SER performance of this adaptive MSDD is not affected by phase fluctuation introduced by a channel because the MSDD and the noncoherent channel estimator are applied. The adaptive MSDD scheme is applied to typical constellation of 16APSK, the (4,12) QAM and the star QAM. The excellent tracking performance of this adaptive MSDD scheme over FSF channels is confirmed by computer simulations.

In this letter, we propose an approximate calculation formula for the resonant frequency of a microstrip antenna with meshed ground plane, which is derived by perturbational technique and is expressed by a simple closed form. The calculated results are in good agreement with FDTD-calculated and measured ones. Therefore, it is confirmed that the proposed formula is valid for approximate evaluation of the resonant frequency of microstrip antenna with meshed ground plane.

A novel K-band MMIC frequency doubler has been developed using resistive series feedback circuit. The doubler exhibits much better D/U ratio, smaller output power variation against ambient temperature and lower power consumption than those of the conventional single-ended doubler. This paper presents the simulation results on the effect of the resistive series feedback by harmonic balance methods. To obtain practical and accurate simulation results, newly developed gate charge model for Cgs and Cgd is introduced. The fabricated result of the proposed MMIC is also demonstrated.

A 20 GHz-band GaAs MMIC receiver module has been developed using 0.15 µm HEMT technology process. It incorporates two front end low noise amplifiers, a double balanced diode mixer, and filters. The RF input frequency ranges 20.1 to 21 GHz and the IF output 1.1 to 2 GHz. Test results show an overall conversion gain of more than 27 dB, and less than a 2.2 dB noise figure. The image-rejection ratio greater than 21 dB has been obtained. The isolation between RF and IF ports is better than 27 dB, and between LO and IF is more than 50 dB.

The present paper modifies the algorithm to estimate harmful event frequencies and examines the definition of modes of operation in IEC 61508. As far as the continuous mode concerns, the calculated results coincide with those obtained based on the standard. However, for the intermediate region of medium demand frequencies and/or medium demand durations, the standard gives much higher harmful event frequencies than the real values. In order to avoid this difficulty, a new definition of modes of operation and a shortcut method for allocation of SILs are presented.

In modems for burst transmission of digital data, rapid carrier and clock synchronization are essential. Typically, frequency correction occurs prior to phase recovery since estimators are sensitive to frequency offsets. In this paper, we derive the bit error rate (BER) performance of a M-ary phase shift keying (MPSK) receiver in a closed form when there is no frequency offset estimator. Then we derive a relationship of the required burst length for certain BER with frequency offset estimator. To obtain the BER=10-4, approximately we need the burst length of 101 at Eb/N0=10 dB and 69 at Eb/N0=15 dB.

In a phase-locked-loop (PLL) frequency synthesizer with binary phase comparison, jitter is hard to suppress. In this paper, we propose a PLL frequency synthesizer with an improved binary phase comparison which can solve the above problem. The effectiveness of the proposed method is confirmed by PSpice simulation results.

In the phase locked loop (PLL) frequency synthesizer which is used in a higher frequency region, the prescaler method is employed in order to increase the operating frequency of the programmable divider. However, since the fixed divider whose division ratio is same as the prescaler is installed at the following stage of the reference divider, the reference frequency is decreased and the performance of the PLL frequency synthesizer is degraded. The prescaler PLL frequency synthesizer using multi-programmable divider is one of the counter measures answering the request. In this paper we propose the reduction of the number of programmable dividers by using the (N+1/2) programmable divider. The effectiveness of the proposed method is confirmed by experimental results.

A nonlinear multiple complex sinusoidal estimator (NMSE) is proposed, as an extended and improved version with system noise of the single sinusoidal estimator previously presented by the author, for extracting multiple complex sinusoids in white noise. This estimator is derived by applying an extended complex Kalman filter (ECKF) to a noisy multiple complex sinusoidal model with state-representation, where the model becomes a nonlinear stochastic system. Proof of the stability is given by using a structure of the state-space signal model and Lyapunov techniques. Also, computer simulations demonstrate the effectiveness of the NMSE from various points of view.

It is not rare case that a floated metal plate exists nearby high speed circuit traces. Heatsink placed on a IC chip nearby circuit traces, metal enclosure or circuit traces in a compact designed product may be a good example. It may be also seen such structure for a shield box and circuit traces confined. It is generally known that such metal plate as placing nearby circuit trace may change circuit trace parameters and then resonance frequency associated with the circuit trace. In this study, we clarified resonance frequency variation with comprehensive observation of input impedance of microstrip line that is an essential model of circuit traces on a printed circuit board. Since such structure is created in various cases in product designs, we believe that the results shown in this study may be useful for EMC design as well as signal integrity. For computation, method of moment was used.

Closed-loop power control providing maximum capacity of the multicarrier channel with frequency selective Nakagami fading is investigated. Use of the famous Gallager channel capacity (water-filling) theorem with the assumption of limited transmitter power and independent fading in partial channels leads to the algorithm for their optimal power loading. Analytical expressions for the capacity of the multicarrier channel as a function of the number of its subchannels and the fading parameters are derived for the cases of Optimal Power Distribution (OPD) and Equal Power Distribution (EPD). The dependence of the capacity gain on the OPD system order, the fading depth and the average SNR due the optimal power control is obtained. Comparison of the power efficiencies of the systems with OPD and EPD is presented.