T.S. Kamal

Design of Yagi-Uda Antenna Using Biogeography Based Optimization

Biogeography based optimization (BBO) is a new inclusive vigor based on the science of biogeography. Biogeography is the schoolwork of geographical allotment of biological organisms. BBO employs migration operator to share information between the problem solutions. The problem solutions are identified as habitat and sharing of features is called migration. In this communication, BBO algorithm is matured to optimize the element length and spacing for Yagi-Uda antenna. The gain of Yagi-Uda is a multimodal function and is hard to optimize because of its reliance on changes in lengths and spacings. To confirm the capabilities of BBO, Yagi-Uda antenna is optimized for three different design objectives which include gain, input impedance and side lobe level (SLL). During optimization, NEC2-a method of moments code evaluates the performance of each design generated by BBO algorithm. The results obtained by BBO are compared with the genetic algorithm (GA), evolutionary programming (EP), comprehensive learning particle swarm optimization (CLPSO), simulated annealing (SA) and computational intelligence (CI).

Linear Array Synthesis Using Biogeography Based Optimization

This paper presents a novel optimization technique biogeography based optimization (BBO) for antenna array synthesis. BBO is a relatively new evolutionary global optimization technique based on the science of biogeography. It is capable of solving linear and non-linear problems. In this paper, BBO algorithm is used to determine an optimum set of amplitudes of antenna elements that provide a radiation pattern with maximum side lobe level reduction and/or null placement in the specifled directions. The results obtained show the efiectiveness of the BBO algorithm, and they are better than previous published results.

Approximate and Exact Small Signal Analysis for Single-Mode Fiber Near Zero Dispersion Wavelength with Higher Order Dispersion

This article presents the comparison of approximate and exact small-signal theories for analyzing the influence of the higher-order dispersion terms on dispersive optical communication systems operating near zero dispersion wavelength for linear single-mode fiber. For the approximate theory, the generalized conversion matrix has been reported and gives the transfer function of intensity and phase from the fiber input to fiber output for a laser source including the influence of any higher-order dispersion term. In addition, expressions for the small-signal frequency response and the relative intensity noise (RIN) response of an ultrafast laser diode including noises are derived. However, it is observed that the approximation assumed for the second-order dispersion term for the approximate analysis is not valid. From the approximate theory, the exact generalized conversion matrix and exact expressions for small-signal frequency response and relative intensity noise (RIN) are obtained. We show that for the exact theory, the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances contrary to the approximate theory as reported by other authors. But we show that third-order dispersion term certainly has some minute impact on the frequency and RIN response for long distance links at high modulating frequencies.

Simulation Results for DWDM Systems with Ultra-High Capacity

We present stimulation results for DWDM systems with an ultra-high capacity up to 1.28 Tbit/s and spectral efficiency approaching 0.4 bit/s/Hz. The impact of signal-to-noise ratio (SNR) on parameters such as channel spacing, length of fiber, dispersion, and number of channels has been investigated and the results obtained have been explained on the basis of fiber nonlinear effects. It has been shown that with an increase in channel spacing, the SNR increases to the maximum optimum value and then decreases to a steady value. With an increase in number of channels, the SNR decreases for small wavelength spacing. For large wavelength spacing, it becomes independent of the number of channels. Keeping channel spacing constant, the SNR decreases with an increase in the length of the fiber. The SNR also improves with a small increase in dispersion of the fiber. Further, it is observed that, with increase in length over dispersion-shifted fiber, the received power decreases and the bit error rate increases.

Large signal analysis of FM-AM conversion in dispersive optical fibers for PCM systems including second order dispersion

By using large signal analysis for dispersive optical fiber, the FM-AM conversion with respect to binary intensity modulated PCM systems including second order dispersion term is discussed. The modified expression for power penalty has been derived and its impact on laser linewidth and bit rate has been investigated. For power penalty less than 0.5 dB, the plots between bit rate and transmission distance are plotted. It is seen that the transmission distance increases with decrease in linewidth over significant bit rates. The transmission distance with first order dispersion term for 300 MHz linewidth is approximately 800km. With proper first order dispersion compensation, i.e., with second order dispersion only, the transmission distance can be enhanced to 10 8 km for this linewidth. The linewidth requirements for systems with different bit rates and transmission distances are also calculated and discussed. Further, it is seen that by including the second-order dispersion term, the bit rate and transmission distance decreases. For higher linewidths, this decrease in bit rate and transmission distance is very less and vice versa. For 300 MHz linewidth, the decrease in transmission distance is just 30 km, and for 30 MHz linewidth, the decrease is approximately 600 km over significant bit rates.

Optimal Synthesis of Thinned Arrays Using Biogeography Based Optimization

Thinning of large arrays in order to produce low side lobes is a di-cult task. Conventional gradient methods often stuck in local minima and hence are not capable of obtaining optimum solutions. As a result, global optimization methods are required to thin large antenna arrays. In this paper, a global evolutionary method, Biogeography Based Optimization (BBO) is introduced as a new tool for thinning large linear and planar antenna arrays of uniformly excited isotropic antennas. The aim is to synthesize linear arrays so as to yield the maximum relative sidelobe level equal to or below a desired level while also keeping the percentage of thinning equal to or above the desired level. The results obtained by BBO are compared with the previous published results of Genetic Algorithm (GA), Ant Colony Optimization (ACO), Immunity Genetic Algorithm (IGA) and Binary Particle Swarm Optimization (BPSO).

Synthesis of thinned planar circular array antennas using biogeography based optimization

This paper presents a novel optimization algorithm biogeography based optimization (BBO) for thinning large multiple concentric circular ring arrays. The objective is to achieve an array of uniformly excited isotropic antennas that will generate a narrow beamwidth and minimum relative side lobe level (SLL). BBO is a new comprehensive force based on the science of biogeography. Biogeography is the schoolwork of geographical allotment of biological organisms. BBO utilizes migration operator to share information between the problem solutions. The problem solutions are known as islands and sharing of features is called migration. In this paper, the authors propose pattern synthesis method to reduce the SLL with narrow first null beamwidth (FNBW) by making the ring array thinned using the BBO algorithm. In this paper a nine ringed concentric circular antenna array with central element feeding is considered. The computational results show that the number of antenna array elements can be brought down from 279 to 131 with simultaneous reduction in SLL of more than 21 dB with a fixed FNBW.

The effect of phase matching factor on four wave mixing in optical communication systems: fuzzy and analytical analysis

In this paper, a modified analysis of Four Wave Mixing (FWM) by incorporating the third-order dispersion parameters is reported. With the help of a modified formula for FWM crosstalk, the effect of second- and third-order dispersion parameters at different input channel powers has been analysed. Under the combined effect of second- and third-order dispersion parameters, the crosstalk introduced by FWM is reduced. Further, we propose a fuzzy-based approach using Adaptive-Network-Based Fuzzy Inference System (ANFIS) to calculate FWM power by varying input channel powers at different intensity-dependent phase-matching factors, and observed that the results are very similar to analytical results.

Validity of third-order dispersion term for single-mode fiber near zero dispersion wavelength

The paper presents the validity of third order dispersion term for dispersive optical communication systems operating near zero dispersion wavelength for single-mode fiber. We show that the second-order dispersion term has no effect on intensity and frequency response even at large modulating frequencies and large propagation distances as reported by other authors but on carrying the analysis further we show that the third-order dispersion term certainly has some minute impact on the frequency response and significant impact on the relative intensity noise (RIN) response for long distance links at high-modulating frequencies.

Performance Analysis of Four Wave Mixing Using Volterra Series Method with Higher-Order Dispersiion Effects

In this paper, the intensity fluctuations due to FWM in the presence of higher-order dispersion effects using Volterra Series Transfer Function method have been investigated. The impact of FWM on the Channel Spacing. Transmission Distance and Frequency has been studied in the presense of higher-order dispersion terms. It has been found that at frequency 50 THz with first-order dispersion compensation, the intensity fluctuation have been reduced to 0.009 mW from 0.155 mW and this can be further improved with first- and second-order dispersion compensation together to .00002 mW. ALso it have been found for intensity fluctuations 0.25 mW, the transmission distance can be enhanced from 120 Km to 620 Km with first-order dispersion compensation and this can be further enhanced to 810 Km with first- and second-order dispersion compensation together. It has also been observed that the second- and third-order dispersion effects are very small, when the first-order dispersion is present.