C. Benjangkaprasert

Rectangular patch antenna with inset feed and modified ground-plane for wideband antenna

This paper presents the technique for increasing bandwidth of rectangular patch antenna from 0.88 GHz (7.76 - 8.64 GHz) to 6.75 GHz (3.49 - 10.24 GHz). This technique use inset feed patch antenna with modified ground plane for achieved widest bandwidth. We will propose three types of rectangular patch antenna: the simple rectangular patch fed by microstrip line, inset feed rectangular patch and inset feed rectangular patch with modifies ground plane. The final simulation result show that the lower edge of frequency is moved down from 7.76 GHz to 3.49 GHz and the higher edge of frequency is shifted up from 8.64 GHz to 10.24 GHz, which is the one selection for increasing bandwidth of rectangular patch antenna for wideband. Details of the increasing bandwidth of microstrip patch antenna are described, and simulation results for obtained wideband performance are presented by using IE3D Zeland software.

Adaptive equalization for DS-CDMA multi-user communication system based on adaptive Laguerre lattice filter

This paper deals with an adaptive equalizer based on Laguerre lattice filter and the recursive least square (RLS) adaptive algorithm for direct sequence-code division multiple access (DS-CDMA) communication system. Intersymbol interference (ISI) arises due to multipath propagation, which destroys the code orthogonality, gives rise to multiple access interference(MAI). Therefore, the objective of this paper is to minimize the effect of ISI with a long impulse response environment based on the proposed receiver. Because of the stability of Laguerre structure is sharing the characteristic of finite impulse response (FIR) filter and infinite impulse response (IIR) filter and the low sensitively of lattice filter is an attractive characteristic. Therefore, we propose the adaptive equalization based on adaptive Laguerre lattice filter for improve the bit error rate (BER) performance of the receiver. Our simulation results show that the performance of the proposed receiver in terms of BER and the stability are better than the conventional Laguerre filter and FIR filter receivers.

Adaptive equalization for DS-CDMA multi-user communication system using Laguerre filters

In this paper proposes an adaptive equalizer using Laguerre transversal filter and a RLS algorithm for adaptation in DS-CDMA mobile communication systems. The Laguerre structure is compromise between the FIR and IIR structures, since the Laguerre structure is always stable. We also analyze the Bit Error Rate (BER) performance of the proposed equalizer and the conventional equalizer. The simulation results show that the performances of the proposed equalizer are better than the conventional equalizer, such as fast convergence and lower BER than the conventional adaptive equalizer for every Eb / N0 value.

A robust variable step-size LMS-like algorithm for a second-order adaptive IIR notch filter for frequency detection

The best adaptive algorithm requires fast convergence speed, low variance, unbias and low steady-state mean square error (MSE) in both low and high signal-to-noise ratio (SNR) situations. We have proposed a robust variable step-size LMS-like algorithm (VS-LMS-L) for a second-order adaptive IIR notch filter for frequency detection in radar, sonar and communication systems. This algorithm is compared with the conventional LMS-like algorithm called the plain gradient algorithm (PG). The time-varying step-size /spl mu/(n) is adjusted by using the square of the time-averaged estimate of autocorrelation of the present output signal y(n) and the past one y(n-1). This technique can reject the effect of the uncorrelated noise sequence on the step-size update, resulting in a small MSE due to the small final /spl mu/(n). Moreover, this algorithm can also improve the convergence speed by comparison with the PG at the same MSE value.

Variable Step-Size Algorithm for Lattice Form Structure Adaptive IIR Notch Filter

In this paper, a new class of a variable step-size algorithm for a second-order lattice form structure adaptive IIR notch filter for detection of sinusoids in noise environments is presented. The proposed algorithm is adjusting two variable coefficients of the adaptive IIR notch filter: one is variable notch frequency and the other is variable notch bandwidth. By the proposed method, the optimization of the coefficients of the filter is obtained. The computer simulation results are shown that the proposed algorithm provides fast convergence speed, low mean square error, low variance of filter coefficients and high impulsive noise robustness. Moreover, to verify the new adaptive algorithm by application to reducing 50-Hz interference in ECG signal. As results, it is evident that the new algorithm gives a good performance

The reduction of gradient noise in gradient-based algorithm by using variable step-size technique

This paper proposes a different approach to control step-size adaptation. The objective is to ensure large step-size when the algorithm is far from the optimum with step-size decreasing as we approach the optimum. The proposed algorithm achieves this objective by employing the output signal energy to control step-size update. In the early stage of adaptation the estimate of the output signal energy is large, resulting in a large step-size. As we approach the optimal, the output signal energy approaches zero, resulting in a small step-size. This provides the fast convergence due to large initial step-size while ensuring low gradient noise due to the small final step-size, resulting in low variance of the filter coefficient.

Microstrip-fed slot antenna with rectangular-shaped tuning stub for WLAN application

This paper presents microstrip-fed slot antenna with rectangular-shaped tuning stub for WLAN application. The characteristics of antenna are proposed and analyzed for instance return loss, bandwidth, and far field radiation patterns. The measured results of the impedance matching for the proposed antenna show the impedance bandwidth, determined by -10 dB return loss, larger than 104% (2.0-6.35 GHz) of the center band, radiation pattern is bi-directional and average gain is 4 dBi.

On Design of Video Equalizer for Distorted Chrominance based on the Bernstein Polynomials

In this paper, we propose a design of video equalizer for compensating the amplitude of chrominance signal based on the Bernstein Polynomials. The use of Bernstein Polynomials in analog filter obtain the advantages are linear phase filter, several parameters that control the amount of phase and magnitude, and flexible for variable of phase. In addition, experimental results are carried out by using the modulated 20T sine squared signal. It is shown that the proposed video equalizer can be enhanced or compressed the amplitude chrominance distortion in color television transmission

Simplify adaptive IIR notch filter based on least mean p-power error criterion

In this paper, a simplify second order IIR adaptive notch (ANF) algorithm based on least mean p-power (LMP) error criterion is presented. The quantizing gradient technique is used to detect high convergence speed and high impulsive noise robustness. This algorithm reduces an amount of multiplication computational equal to the length of input data. It is proved here that the convergence speed, variance, bias and noise robustness do not depend on p values. For practical application with most desirable purposes, the value of p=1 is chosen, the results of computer simulation and application on TMS320C50 digital signal processing starter kit are given to demonstrate the convergence speed and noise robustness performance.

Performance comparison of adaptive algorithms for multiple echo cancellation in telephone network

In this paper presents the comparison of the performance of the variable step-size LMS adaptive algorithm and the fixed step-size LMS adaptive algorithm for cancels multiple echoes signal in telephone networks. The core of this paper is a multiple delay estimator, which estimates and distributes delays to each individual fixed length short echo canceller. It is shown that the variable step-size LMS adaptive algorithm yields the performances over the fixed step-size LMS algorithm. Computer simulation results are provided to confirm the performances of the variable step-size LMS algorithm.