Jyoti Saxena

Microstrip Filter Designing by SRR Metamaterial

In this paper planar and compact band stop filter using split ring resonator (SRR) metamaterial is proposed. Band stop type attenuation is presented from L-to X-band. Low insertion loss in the pass band and high attenuation in the stop band can be considered as the advantage of this filter. Filter characteristics of SRR is presented using microstrip line. Here SRR is introduced in the substrate layer of microstrip line. It has been observed that the rejection level of the filter in stop band goes on increasing as we increase the number of SRR in the structure. Size of SRR is much less than the operating wavelength thereby several SRR can be introduced in substrate layer to provide a compact structure with high rejection level in the stop band. The frequency of filtering depends on the dimensions of SRR. The effect of varying the dimensions of SRR on the filtering frequency is also presented in this paper. It has also been observed by Nicolson-Ross-Weir approach that at the filtering frequency, value of relative permeability as well as relative permittivity for this structure is negative. This confirms that this structure behaves as a Left Handed medium.

Near---Far Resistant ICA based Detector for DS-CDMA Systems in the Downlink

The performance of a conventional single user DS-CDMA receiver is severely limited by multiple access interference (MAI) and near–far effects. This severity has motivated research into adaptive filtering, near–far resistant detectors and power control strategies for DS-CDMA systems. In this paper, we propose a near–far resistant detector based on independent component analysis (ICA) of the received signal. Since ICA is a blind technique, the proposed ICA based detector has the potential to combat the near–far problem. The ICA is a higher order statistical technique based on the assumption of independence of source signals. The assumptions in ICA algorithm are the realistic conditions in a DS-CDMA system and therefore ICA algorithm can be applied successfully to detect the signal of the desired user. The focus of this paper is to illustrate the near–far resistance capability of the ICA based detector. Simulation studies performed on the proposed detector show that it is resistant to the near-far problem and has low bit error rate.

Modified Optimum Beamforming for Smart Antenna in WCDMA Network

Third-Generation based Wide Band Code Division Multiple Access (W-CDMA) networks have been characterized for high data rate services accessible to a large number of users. But multipath and co-channel interference puts a limit on system capacity, throughput and new multimedia information services like wireless internet or video streaming. Smart antenna technique that includes Direction of Arrival (DOA) approach and Adaptive Beam forming algorithm is a promising means to improve the over-all system capacity and to overcome limited spectrum problem by effectively reducing the multipath and co-channel interference. In this paper, DOA estimation is done by Multiple Signal Classification (MUSIC) algorithm and Minimum Variance Distortion less Response (MVDR) algorithm is used for adaptive beam forming that continuously adjusts the weight of antenna arrays for creating a beam to track the desired user automatically, and to place null towards the interference user. Here, we improve on the MVDR method in order to assign the weightings. Instead of using a single linear equality constraint, a variable constraint has been used to obtain the optimum weights that decrease the gain in the undesired direction and desired direction comes out with more gain and without distortion. Obtained results are analyzed for the conventional method and the proposed method by observing beam forming spectrum by first varying number of antenna elements and then by varying the spacing between elements. For both the cases, the performance is better for the proposed method in terms of lower noise floor, more relative power and sharper peaks in the desired user direction than conventional method.

Design optimization of CPW-fed microstrip patch antenna using constrained ABFO algorithm

This paper explores the potential of bio-inspired soft computational technique known as adaptive bacterial foraging optimization (ABFO) for the joint optimization of geometrical parameters of compact coplanar waveguide (CPW)-fed microstrip patch antenna with defected ground structure. The presented research work is divided into three phases. In the initial phase, the intended antenna is designed and analyzed using finite element-based electromagnetic simulator Ansoft HFSS 15.0. In the subsequent phase, the analytical equations of various design parameters are modeled using curve fitting technique in MATLAB and root mean square error-based fitness functions are derived for individual design parameters. Then, a joint cost function is formulated from individual fitness functions for evaluation in optimization algorithm. Adaptive BFO is an improvement in classical BFO algorithm that dynamically adjusts the run-length unit parameter to maintain the balance between exploration–exploitation trade-off. In the final phase, a variation in the adaptive BFO algorithm termed as ‘constrained ABFO’ is projected and designed to suit the bounded constraints imposed by anticipated antenna structure. The modified algorithm is efficaciously used for joint optimization of specific design parameters to transform ‘dual-band performance’ into ‘broadband performance’ for high-speed point-to-point wireless services. The performance of design optimization using constrained ABFO is compared with the original BFO, particle swarm optimization (PSO), hybrid bacterial foraging–particle swarm optimization (BF-PSO), invasive weed optimization (IWO) and artificial bee colony (ABC) techniques to scrutinize its adequacy.

Performance Evaluation of OWC Using Different Modulation Techniques

Abstract In this paper, performance of an optical wireless communication (OWC) channel has been investigated using different modulation techniques such as phase shift keying (PSK), differential PSK (DPSK) and optical quadrature PSK (OQPSK). This investigation has been compared at a bit rate of 20 Gbps. The results are evaluated in terms of quality (Q) factor and bit error rate (BER) using different modulation techniques. It is observed that by using PSK modulation technique, the signal can travel up to 70 km transmission distance with acceptable BER of 3.48×10−12 and Q factor of 6.93. It is also observed that by using DPSK and OQPSK, system covers transmission distance of 80 and 90 km with acceptable values of Q factor of 6.59, 6.02 and BER of 2.34×10−11, 1.46×10–10, respectively.

Comparative investigations of DWDM transmission system with PMD for different orthogonally modulated signals at 80Gb/s

Polarization mode dispersion PMD has become one of the major limiting factors for high-bit-rate optical transmission systems. This paper evaluates the performance of dense wavelength division multiplexed DWDM system with PMD at 80Gb/s in the presence of Kerr-nonlinear effects. Orthogonally modulated signals have been investigated and compared for tolerance against PMD in a DWDM transmission system with direct detection receivers. The optimized combinations of orthogonal polarization OP with carrier-suppressed return-to-zero CSRZ and CSRZ differential-phase-shift-keying signals are shown to improve PMD tolerance over high bit rates and long transmission lengths. Improved performance greater than 4dB is observed for CSRZ modulated signal with OP because of less channel cross talk and reduced power transfer between adjacent bits over different PMD values. The numerical results demonstrate that our proposed orthogonally modulated signals perform better with lesser complex direct detection receivers. Copyright

Power control analysis of Gaussian approximated WCDMA system under Rayleigh fading channel

Wideband Code Division Multiple Access (WCDMA) is an air interface standard specially designed for third generation (3G) mobile networks to provide low data rate voice services to high data rate multimedia services. But different types of multipath fading, multi-access and co-channel interferences put a limit on overall system performance. The mechanism of power control provides a best alternative to enhance the system performance. In this paper, the behavior of WCDMA system is analyzed by using Gaussian Approximation (GA) technique in which interference and channel noise in the system are generated by the approximations of mean and variance of interferer power. The various power control scenarios have been used to analyze the performance of Gaussian approximated WCDMA system. System performance with the severer effect of Rayleigh fading has also been analyzed for perfect power control based conventional and rake receivers. Simulation results are obtained for Signal to Interference Noise ratio (SIR) verses number of users and Bit Error Rate (BER) verses number of users at different power control scenarios with different system processing gain and different number of interfering cells. Results show that WCDMA system performance improves with perfect power control mechanism, at high processing gain with less number of interfering cells. It is also shown that rake receiver has much better performance than conventional receiver at different processing gain, different number of interfering cells.

Superdirective patch antenna array using metamaterial

A new method to improve the directive gain of patch antenna array for ISM band of 2.4 G Hz with metamaterial is presented. This method is based on suppressing the electromagnetic interference between the elements of antenna array. The electromagnetic interference between elements of antenna array is reduced by using Split Ring resonator metamaterial. Here Split ring resonator metamaterial acts as a notch filter between the arrays elements thereby reducing the mutual coupling between the array elements. Suppressing of mutual coupling between the array elements allows for denser packing and enhanced directivity of antenna array. The electromagnetic characteristics of SRR metamaterial and patch antenna array with and without SRR mtamaterial are studied. Simulation results show that by introduction of SRR metamaterial into patch antenna array there is improvement of directive gain of patch antenna array thereby approaching a superdirective patch antenna array.

Effect of optimized alternate polarization on performance of N X 60-gb/s WDM transmission system

In this paper, simulation of 60-Gb/s alternate polarization of adjacent bits in a Wavelength Division Multiplexed (WDM) transmission link has been carried out for Return to Zero and differential phase shift keying modulation formats. Alternate Polarization Return to Zero (al-PRZ) system for 8, 16 and 32 channels has been analysed. The effect of variation of input power is observed in terms of Q value. It is found that Alternate Polarization Return to Zero (al-PRZ) suppresses the nonlinear effects at higher power levels of 22 dBm per channel and also improves the transmission length to 640km for a N X 60-Gb/s WDM system.

MAI Mitigation in MC-CDMA Systems Using Social Impact Based Wireless Communication Algorithm

In this paper a novel optimization technique i.e. Social Impact based Wireless Communication Algorithm (SIWCA) has been applied on multi-carrier code division multiple access (MC-CDMA) communication systems to mitigate multiple access interference (MAI). MC-CDMA is being researched as an alternate technology for fourth generation (4G) as well as fifth generation (5G) mobile systems. MAI has been a major concern for the CDMA based systems. MAI increases the bit error rate in a MC-CDMA system, which in turn degrades the system performance. The SIWCA is based on the social impact theory of human behavior in the society. The proposed approach combines the social sciences with the communication technology. The simulation results show that SIWCA based MC-CDMA detector is capable of significantly reducing the MAI and gives a near-optimum performance. Further SIWCA is compared with popular optimization techniques like genetic algorithm (GA) and binary particle swarm optimization (PSO) for different parameters. Simulation results show that SIWCA converges fast and works with lesser number of control parameters as compared to GA and PSO.