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This manuscript deals with the implementation of adaptive neuro-fuzzy inference system (ANFIS) approach to automatic load frequency control (ALFC) of six unequal areas’ multi-generation hyb...

In this paper, artificial neural network (ANN) and fuzzy-based adaptive neuro-fuzzy inference system (ANFIS) approach to automatic generation control of three unequal area hydro-thermal power systems has been introduced. The proposed ANFIS controller combines the advantages of fuzzy controller as well as quick response and adaptability nature of ANN. Area 1 and area 2 consist of thermal reheat power plant whereas area 3 consists of hydro power plant with electric governor. Performance evaluation is carried out by using ANN, fuzzy, and ANFIS control approaches. To enhance the performance of intelligent controller, sliding surface is included. The performances of the controllers are simulated using MATLAB/SIMULINK software. A comparison of ANFIS, ANN, fuzzy-based approaches shows the superiority of proposed ANFIS over ANN, fuzzy for change in frequency and tie-line power deviation in three area interconnected power system.

To characterise the helical slow-wave structure (SWS), two conventional analytical techniques are used: the field analytical approach and equivalent circuit analytical approach. However, these two approaches give same analytical results after a lengthy algebraic manipulation, moreover, the complexity of the analysis enhances as one goes for more and more practical situations. In this paper, a numerical approach has been presented to predict the structure characteristics, namely, the dispersion characteristics and the interaction impedance of an inhomogeneously loaded helical SWS based on field expressions and boundary conditions. Here, using field expressions and boundary conditions at different structure regions, a complex determinant has been formed by the co-efficients of unknown field constants as done in conventional method. To obtain the dispersion characteristics of the structure the complex determinant is solved numerically. To evaluate the Interaction Impedance of the structure, the integrals involved with the expression of power are also solved numerically. The results obtained from this present approach fully agree with those obtained from conventional method for typical practical structures developed here. Moreover, this present numerical approach reduces the complexity of the algebraic manipulation of the conventional method.

An expression for interaction impedance of a practical helix slow-wave structure used in a high power, broad-band Travelling Wave Tube, based on tape helix model is derived. The method is validated by comparing the theoretical values of axial propagation constant and the interaction impedance with the experimental data for typical structures.

The paper presents evaluation of electromagnetic field distribution and wave impedance variation of electromagnetic field between two antennas excited from coherent sources, taking space attenuation, impedance mismatch and multiple reflections between two sources into account. The variations of electric and magnetic field distribution and wave impedance as a function of position between two antennas are evaluated. The region between the two antennas, which is most suitable for EMI measurements under high electric and low magnetic fields or low electric and high magnetic fields is found. Numerical results are presented.

A 30W (peak) S-band helix travelling wave tube (TWT) has been designed and developed. Specialised techniques for the fabrication of gridded gun, rf attenuators and stainless steel to alumina sealing were developed. A number of tubes were successfully fabricated, processed and tested to check the reproducibility of rf output characteristics. The hot test results were found comparable with the predicted results. Computer aided design packages were used to validate the design of the vital components and predict the performance of the TWT.

In this paper, a detailed design procedure for designing a thin disc pill-box type microwave window, operating in narrow frequency range at S-band and at a power level of 5 MW, has been given. The design criteria and a generalised design flow chart have been presented and discussed in detail. A method has been suggested for quicker experimental optimisation of the length of the circular waveguide section, which results in substantial saving of time and material. This design methodology can easily be adopted for designing practical pill-box type high power microwave windows.

This paper presents an extensive study of the advanced signal processing techniques for the classification of different Power Quality (PQ) disturbances. A detailed study of application of the signal processing techniques like Wavelet Transform (WT) and Wavelet Packet Transform (WPT) is carried out for the said purpose. These techniques are used to extract useful information from the raw signal in different frequency bands and give the time–frequency information. Hence, the statistical features are derived from this information and are used for the classification purpose. The features extracted are given to the Neural Network (NN) for training and subsequently it is tested for an effective classification. Three types of NN classifiers, namely, Multi Layer Feed Forward (MLFF), Probabilistic Neural Network (PNN) and Radial Basis Function (RBF) NN are analyzed for effective classification of PQ disturbances. For real-time implementation, one has to see the structural complexity of NN along with its ca...

This paper discusses the necessity of carrying out qualification, screening and failure analysis of electronic components for space application. The result of failure analysis carried out in Quality Assurance Division of Vikram Sarabhai Space Centre is also discussed. In connection with failure analysis, illustrations are given with photographs taken with Scanning Electron Microscope (SEM) for some failure mechanism observed in the transistor and the integrated circuits.

Different types of X-band Gunn diode oscillator cavities and Impatt diode oscillator cavities, developed at SPL, Delhi, have been discussed. These cavities can be tuned mechanically. One of these cavities has a provision for dielectric tuning. The characteristics of some of these solid state oscillators are shown and attempt has been made to explain their performance.

A modification is made to the method of measuring dielectric constants developed by Sinha and Brown. The mismatch occurring between the empty and the partially filled portions of the cavity is removed by putting a quarter-wavelength matching section at the end of the rod specimen. This considerably simplifies the system which becomes much easier to handle theoretically. Also, the computational labour in the evaluation of loss tangent is considerably reduced. The main advantage, however, of this modified method is the ability to measure the dielectric constants of samples having lengths less than half a wavelength, a facility not available with the original method.

A technique for measuring high values of ‘Q’ of microwave cavities is described. The problem of measuring very narrow bandwidths, say of the order of 0·5 mc/s. or less centred at a microwave frequency, is considerably simplified by obtaining the same response curve centred at an I.F. frequency, as the effective Q then is very considerably reduced. Consistent and reliable results have been obtained on the measurements of Q of the order of 20,000 of a cavity resonant in the ‘X’ band.

This paper describes an algebraic process of finding all the irredundant covers of a switching function. Here the cover terms are identified with column matrices and a formulation of this matrix multiplication avoiding redundancies is presented by two theorems. A systematic process of search by which residual redundancies can be detected and avoided is also explained. An worked out example and proofs of theorems are included

The electrical properties of the solid solutions of PbZrO3 and CaZrO3 have been investigated over a wide temperature intervals. The maximum molecular percentage of the second component has been taken to be 10 per cent. An attempt has been made to explain the various phase transitions encountered in the temperature range of investigations—room temperature to about 350°C.

The development of high resistivity microwave ferrites having the general composition Ni1-xCuxFe1·9Mn0·02O4 has been described. Three different compositions corresponding to x = 0, 0·2 and 0·4 have been attempted. The reasons for selecting these particular compositions in the light of their microwave properties have been discussed. Most of their relevant parameters, e.g. the d.c. resistivity, curie temperature, bulk density, saturation magnetization, max. permeability, microwave permittivity and permeability have been determined with a good accuracy. The samples obtained from the compositions corresponding to x = 0·2 and x = 0·4 have been tried in isolator structures and have shown satisfactory characteristics. In addition, as the values of curie temperature measured for these compositions turn out to be very high, these materials offer a good potentiality for the development of high power ferrite devices.

Conventional axial mode helix requires a broad band impedance transformer for feeding it from a 50 ohms coaxial line. Generally, these transformers take the form of a section of coaxial line of varying characteristic impedance. Separate impedance transformer increases the sine of the antenna transformer combination which is undesirable for many applications. The present paper describes an axial mode helical antenna in which the impedance transformer has been built into the helical winding.

The electrical properties of BaTiO3 doped with Sb have been studied. The nature of variation of ∈ and tan δ with temperature in this material shows that, under the doped conditions, the mechanism of polarization changes from spontaneous to that of relaxation after curie temperature. This supposition is also verified from the study of variation of permittivity with different levels of applied r.f. power at temperatures higher than that of curie. Further, the dielectric hysteresis loops of this material corresponding to various applied voltages were also studied both at a temperature below curie and a temperature above curie. The loops corresponding to the temperature below that of curie showed saturation while those corresponding to the temperature above curie did not show saturation, thus giving another proof of this supposed existence of relaxation polarization in this doped material at that temperature.

Filters with equi-ripple transmission characteristics in the pass-band as well as the stop-band have, for a long time, been considered as optimum with regard to performance and economy of elements. These were first synthesized by Darlington by the use of Jacobian elliptic functions. This method necessitates the use of double-entry tables, but with the tables commonly available, the values are not sufficiently accurate, especially if the number of poles is greater than four. Other methods based on potential analogy, and using electrolytic tanks, are equally cumbersome.In this paper, a method using rational functions has been discussed, and an example of design has been given. This method has the advantage that it does not require the use of tables, and calculations can be carried out to the desired degree of accuracy. It can also be extended to give design tables for normalized low-pass filters, from which the circuit elements of any type of filter can be obtained, using impedance and frequency tra...

(1964). Some Design Aspects of Ferrite Isolators. IETE Journal of Research: Vol. 10, No. 9, pp. 444-458.

A very commonly-used slow-wave structure for high-power, large bandwidth TWT's that consists of a helix supported by means of wedge- shaped dielectric bars in a metal shell has been studied for interaction impedance. The results show the effects of varying various helix and support parameters on the interaction impedance and the gain-frequency response.

A field analysis has been developed to derive an expression for an important design parameter, viz., the dielectric loading factor of a dielectric wedge-supported helix, enclosed in a glass envelope which is very commonly used in medium-power, broad-band TWT's. The result is compared with a corresponding metal envelope situation.

A simple, straightforward equivalent circuit analysis for a helix supported by dielectric wedge bars in a finned metal shell, a slow-wave structure that is used in high power, broad-band TWT's, shows that there exists an optimum value of the radial fin dimension corresponding to a fairly dispersion-free phase velocity versus frequency response of the structure.

Two major material interaction problems in the semiconductor devices and integrated circuits ‘purple plague’ and ‘electromigration’ have been discussed in this paper. Illustrations are given with scanning electron micrographs.

A ferrite-loaded helical line with an inner coaxial conductor has been analysed by working out only 2×2 determinant. The equivalent circuit analysis has also been developed for the structure.