Showing papers in "Iete Journal of Research in 1982"
14 citations
TL;DR: In this paper, the authors review methods and applications of two-dimensional analysis approach applicable to transmission structures, circuits, resonators and antennae with one of the dimensions much smaller than the one of this paper.
Abstract: This article reviews methods and applications of two-dimensional analysis approach applicable to transmission structures, circuits, resonators and antennae with one of the dimensions much smaller t...
7 citations
TL;DR: The possibilities of Legendre Polynomial transform for data compression are explored and a computationally fast algorithm for obtaining Legendre transforms of sequences is presented.
Abstract: The television pictures can be approximated by polynomials, so an orthogonal transform having polynomials as the basis vectors can be used for best representation of such images. The possibilities of Legendre Polynomial transform for data compression are explored in the present paper. This paper also presents a computationally fast algorithm for obtaining Legendre transforms of sequences.
7 citations
TL;DR: In this paper, a tutorial-cum-review of the properties of cepstral transformation is presented, and some auxiliary techniques which restore the violated but useful assumptions are discussed.
Abstract: This is a tutorial-cum-review paper. The properties of cepstral transformation are discussed. Cepstra of some sample functions are evaluated. In terms of the properties of cepstral transformation, the hope that it could be used to separate convolved signals is analysed. Some auxiliary techniques which restore the violated but useful assumptions are discussed. It is argued that the claims made on behalf of the deconvolution by cepstral transformation are generally exaggerated and if the technique is to contest its competitors successfully, much yet remains to be done. It may be advisable to use cepstral transformation in conjunction with other techniques for deconvolution.
4 citations
TL;DR: In this article, an auto-track system employing the step-track technique has been developed for tracking geo-synchronous satellites, where induction motors have been used for the antenna drive.
Abstract: An auto-track system employing the step-track technique has been developed for tracking geo-synchronous satellites. Continuous tracking employing this technique gives rise to an amplitude modulation (a.m.) in the transmitted and the received carriers due to a continuous movement of the antenna around the beam maximum. In order to avoid this a.m. and also to avoid an undue strain on the drive system, a provision has been made to switch off the system after the received signal has been maximized. Induction motors have been used for the antenna drive. The system switches on automatically after a specified interval to update the antenna pointing thereby maintaining a carrier-to-noise within 0.5 dB of the maximum throughout. The prototype of the system was used to track the Symphonie satellite during STEP‡
4 citations
TL;DR: In this article, a composite unit device, comprising a J-FET, a bipolar transistor and three passive resistors, is proposed, which offers a linear transfer characteristic over a wide range of input voltage along with high input resistance.
Abstract: A new composite unit device, comprising a J-FET, a bipolar transistor and three passive resistors, is proposed. The new unit offers a linear transfer characteristic over a wide range of input voltage alongwith high input resistance. The proposed circuit is fully compatible with silicon integrated circuit (IC) technology and may thus be fabricated as a three-terminal single unit device.
4 citations
TL;DR: An experiment, to study the improvements in accuracy and precision in broadcasting standard time ATA format via satellite over ATA high frequency broadcast, is described.
Abstract: An experiment, to study the improvements in accuracy and precision in broadcasting standard time ATA format via satellite over ATA high frequency broadcast, is described. The ATA format was transmitted in both, the routine code with ticks and tones and with BCD code carrying information about time and date i.e. Year, Month, Day, Hour, Minute, Second and DUT1 correction. The signals were transmitted from Delhi Earth Station and measurements were made at Delhi Earth Station (DES), Ahmedabad Earth Station (AES), Madras Earth Station (MES) and Transportable Remote Area Communication Terminal (TRACT) stationed at Calcutta: thus covering a large cross-section of India.
3 citations
TL;DR: The problems involved in Speech Transmission in packets are addressed, and a few specific cases of Packet Voice Transmission are examined, where silence periods are eliminated.
Abstract: The growth of computer networks has led to the development of the Packet Switching and Packet Broadcast Techniques. Especially useful for bursty traffic, they are of use for speech which is inherently so, with about 50% of the time occupied by silence periods. In Packet Transmission of speech, we digitize the speech and transmit packets of fixed or variable size and reassemble the bits at the destination.Unlike transmission of data, where the bit error rate is most important, in speech the prime consideration is delay. Depending upon the digitizing method, we have different error tolerance limits.In this paper, we first address the problems involved in Speech Transmission in packets, and then examine a few specific cases of Packet Voice Transmission. The concepts of TASI are also inherent in Packet Voice Transmission, where silence periods are eliminated. This involves the use of efficient speech activity detectors. Since there is a certain amount of error tolerance present in digitized speech (albeit in ...
3 citations
TL;DR: The present state-of-the-art of inverter circuits for UPS applications is reviewed in this article, where the importance of magnetic coupling in UPS inverter systems is emphasized.
Abstract: The present state-of-art of inverter circuits for UPS applications is reviewed in this paper. Circuit configurations, their advantages and disadvantages are discussed. The importance of magnetic coupling in UPS inverter systems is emphasized. A large number of references have been quoted to facilitate the reader to refer for actual details of control schemes, output voltage harmonic components and design details.
3 citations
TL;DR: It has been shown here how the microprocessors can be interfaced to the coded signal from an external encoder and decode the data even in the presence of errors, and the flowchart and the memory organization in the microprocessor have been discussed in this paper.
Abstract: For a short constraint length nonsystematic rate-half convolutional code with a Hamming distance of 5, a Viterbi decoding algorithm using Synertek—6502 microprocessor system has been developed. It has been shown here how the microprocessors can be interfaced to the coded signal from an external encoder and decode the data even in the presence of errors. The flowchart and the memory organization in the microprocessor have been discussed in this paper. Care has to be taken so that the calculated parameters, like the likelihood function does not exceed the word-length of the micro-processor. A throughput data rate of 2400 bps has been achieved with the system. This enables reliable transmission of 1200 bps data after encoding by rate-half error correction code to result in 2400 bps line rate, over telephone channels.It is important to consider the problems of requiring different computation time for different iterations in the decoding and establishing a reference time in the microprocessor to start iteratio...
2 citations
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TL;DR: The National Phyical Laboratory (NPL), in collaboration with Overseas Communications Service (OCS), has been giving HF time broadcast tinder the call sign ATA since 1959 and the present set-up in details is described.
Abstract: The National Phyical Laboratory (NPL), in collaboration with Overseas Communications Service (OCS), has been giving HF time broadcast tinder the call sign ATA since 1959. These signals are being used by a large number of scientific users in India and the neighbouring countries as a reliable source of standard time. Since its inception, the transmitting system of ATA has undergone various stages of development leading to its present state. This paper reviews these stages of development and describes the present set-up in details. The individual responsibilities of NPL and OCS for ATA broadcast are explained. Some future plans for development have also been discussed.Recently, a questionnaire on the usage of ATA was circulated in India. The varied response of the users to this have also been described.
TL;DR: A passive technique, where a line-10 of the odd field of TV format was identified and using as the transfer pulse or time marker between participating stations, was used, and the limitations and future prospects of this technique are discussed.
Abstract: Precise time transfers were made and the two atomic caesium clocks at Delhi Earth Station (DES) and Ahmedabad Earth Station (AES) were synchronized to submicrosecond precision, using direct television broadcast of Delhi Doordarshan from DES to AES by the satellite symphonie. A passive technique, where a line-10 of the odd field of TV format was identified and using as the transfer pulse or time marker between participating stations, was used. The limitations and future prospects of this technique, in view of Indian Space Programme, are discussed.
TL;DR: Using the technique of time expansion at the transmitter, it is possible to send a higher quality picture at a lower bit rate and suitable interpolation at the receiver improves the quality of the picture.
Abstract: The paper describes a scheme for producing and digitizing a low-resolution (256 × 256 pels) achromatic picture signals. Using the technique of time expansion at the transmitter, it is possible to send a higher quality picture at a lower bit rate. A DM-encoded picture at 8 MHz is transmitted at 4 Mb/s in the channel achieving a band compression by four. Suitable interpolation at the receiver improves the quality of the picture.
TL;DR: In this paper, an interesting design criterion for minimization of interfering noise voltage in the output of the said pre-amplifier circuit has been derived, and the advantage of the present method of eliminating the interfering voltages in the recorded (ECG) bio-signal as compared to the usual frequency do...
Abstract: The impedance matrix of the n-channel FET as an active network device as well as the general matrix equation of performance of an FET cascode (ECG) bio-instrumentation pre-amplifier have been obtained. Further, an interesting design criterion for minimization of interfering noise voltage in the output of the said pre-amplifier circuit has been derived in the text. According to this criterion, the bias point of the pre-amplifier circuit is uniquely related to the active device parameters of a matched pair of FETs. The input to the said pre-amplifier may contain bio-signal source voltage along with the electrode artifacts and electrostatic and electromagnetic interfering voltages from the neighbouring electrical power networks. If the design criterion is fulfilled, there is automatic suppression of the said interfering voltages in the output of the pre-amplifier. The advantage of the present method of eliminating the interfering voltages in the recorded (ECG) bio-signal as compared to the usual frequency do...
TL;DR: In this paper, the derivative term in a proportional integral derivative (PID) controller is replaced by a suitable time delay, the noise contamination in the output is smoothed out while the other good effects of PID action are preserved.
Abstract: If the derivative term in a proportional-integral-derivative (PID) controller is replaced by a suitable time delay, the noise contamination in the output is smoothed out while the other good effects of PID action are preserved. Sufficient conditions for the choice of time delay are established. Optimization of such a system with a prescribed degree of stability is worked out and compared with the response of a system with PID controller. The output is substantially noise free.
TL;DR: In this article, a theoretical method for computing the characteristic impedance of the inverted microstrip and suspended microstrip lines, for Microwave integrated circuit application, at frequencies above X-band, is reported.
Abstract: A brief outline of the theoretical method for computing the characteristic impedance of the inverted microstrip and suspended microstrip lines, for Microwave integrated Circuit application, at frequencies above X-band, is reported in this paper. Design data on the impedance characteristics of single and coupled lines for both these configurations are presented.
TL;DR: A procedure for the design of optimal feedback controls for linear time-invariant systems relative to time-weighted quadratic performance criteria is presented and an example is given to demonstrate the control over transient behaviour given by the design based on time- Weighted performance criteria.
Abstract: A procedure for the design of optimal feedback controls for linear time-invariant systems relative to time-weighted quadratic performance criteria is presented. An example is given to demonstrate the control over transient behaviour given by the design based on time-weighted performance criteria.
TL;DR: The study shows that the incorporation of a high capacity satellite channel increases the network throughout and reduces the average packet delay at minimum cost and thereby improves the performance of the network.
Abstract: The Packet-Switched Computer Communication Networks have now been well-established regarding their use for data communication, computer-hardware and software resource sharing, database access facility, interactive computing and many other uses. Recently, the study of cost-effective structure of computer networks is in great progress. The success has been very well achieved in the design of terrestrial networks in which a data or message can be transmitted with minimum possible delay. In this paper, authors survey some of the network design algorithms and procedures. Flow Deviation and Cut-Saturation algorithms have been extended for the design of a mixed-media network which contains both the terrestrial and satellite links. The study shows that the incorporation of a high capacity satellite channel increases the network throughout and reduces the average packet delay at minimum cost and thereby improves the performance of the network.
TL;DR: In this article, the optimal α-β-γ filter with an imperfect predictor was shown to be equivalent to the Kalman filter when the prediction uncertainties and the measurement statistics are white Gaussian.
Abstract: Recursive relationships are developed for an optimal α—β—γ filter having an imperfect predictor. The statistics of the measurement and prediction errors are incorporated in the determination of oprimalα, β and γ and parameters. When the prediction uncertainties and the measurement statistics are white Gaussian, the optimal α—β—γ filter is shown to be equivalent to the Kalman filter.
TL;DR: In this article, cross-correlation between barometric pressure and critical frequency for E region for Ahmedabad, Colaba, Kodaikanal and auto correlation of critical frequency and virtual height is studied.
Abstract: Cross-correlation between barometric pressure and critical frequency for E region for Ahmedabad, Colaba, Kodaikanal and auto-correlation of critical frequency and virtual height for E region for Ahmedabad, Haringhata are studied for several months in 1963 and 1968. Sustained correlation in the annual or biannual periodicities of the meteorological parameters and the ionospheric parameters is ascertained. Superposed latitude and solar heat effects on this correlation have been detected.
TL;DR: In this article, two SC integrator configurations using single unity gain amplifier are described, one is compatible with the bilinear Z-transform and the other with the single-input single-output (SISO) transceiver.
Abstract: Two new active switched capacitor (SC) integrator configurations using single unity-gain amplifier are described. The second circuit is compatible with the bilinear Z-transform.
TL;DR: A scheme for active compensation of Deboo's integrator is proposed and is shown to have better Q and superior response to those reported in the past.
Abstract: A scheme for active compensation of Deboo's integrator is proposed. It is shown to have better Q and superior response to those reported in the past. The Q-factor is evaluated in terms of a mismatc...
TL;DR: In this article, the authors present a method for comparing costs for a telecommunications plant between subscriber premises and the first code of a multichannel, multiservice telematics network.
Abstract: Since 1975, and in co-operation with the French Telecommunications Authority, we have been conducting field trials and feasibility studies, to determine the capability of existing copper loop plant to support telematics services.This paper presents some of the economic information that has come out of our program. The economic analysis proceeds from a study of the technical options most likely to prove cost-effective in the foreseeable future.We present a method for comparing costs for telecommunications plant between subscriber premises and the first code of a multichannel, multiservice telematics network. The application of our method, to the possible technical solutions in any given case, leads to a series of conclusions which could be valid for the coming stages of telematics networks development.
TL;DR: The second Indian satellite for earth observations, BHASKARA-II, was launched into a near-earth orbit on 20 November 1981 as discussed by the authors, and the satellite microwave radiometer (SAMIR) was one of the two primary payloads onboard the spin-stabilized satellite which is functionally similar to its predecessor, launched on 7 June 1979.
Abstract: The second Indian satellite for earth observations, BHASKARA-II, was launched into a near-earth orbit on 20 November 1981. The Satellite Microwave Radiometer (SAMIR) is one of the two primary payloads onboard the spin-stabilized satellite which is functionally similar to its predecessor, BHASKARA-I, launched on 7 June 1979. The SAMIR payload on-board BHASKARA-I was a two-frequency, three-channel system (two in the 19-GHz band and one in the 22-GHz band) while that presently on-board BHASKARA-II is a three-frequency radiometer operating at 19.35, 22.235 and 31.4 GHz frequencies.A temperature sensitivity of better than 1° K has been achieved in all the three radiometers and the radiometric antennas have coincident footprints of 125 km each.The main objectives of the radiometers are to investigate the sea state, liquid water and water vapour contents over the oceans adjoining the Indian subcontinent and also for synoptic studies related to soil moisture, snow cover and biomass on the Indian land.The initial ...
TL;DR: A circuit, basically, using three operational amplifiers and a resistor is given for the simulation of ideal grounded capacitor and its application in realizing an active-R band-pass biter is experimentally demonstrated.
Abstract: A circuit, basically, using three operational amplifiers and a resistor is given for the simulation of ideal grounded capacitor. Its application in realizing an active-R band-pass biter is experimentally demonstrated.
TL;DR: This paper describes a general-purpose interface for PERTEC digital tape recorder that generates computer compatible tape and has been built and successfully used for many scientific experiments.
Abstract: With availability of computer system at most of the scientific research centres, it has become almost obligatory on the part of the scientists to acquire data directly on digital magnetic tapes. This helps in analysing the data quite accurately, rapidly and more imaginatively than in the past when data was entered into the computer through cards/ punched paper tapes after tiresome hand scaling. Although the digital magnetic tape units are not manufactured in India-they can be imported. Almost all the tape units need customer interfaces to be developed by the user according to the data formats suitable to him. This paper describes a general-purpose interface for PERTEC digital tape recorder. With slight modification, it can be used for most of the tape recorders. The interface generates computer compatible tape. The interface has been built and successfully used for many scientific experiments.
TL;DR: In this paper, a microstripline Gunn Oscillator with a Barium Nonatitanate (Ba2 Ti9 O20) dielectric resonator has been designed and developed to realize a low-noise compact microwave source.
Abstract: A Microstripline Gunn Oscillator stabilized with a Barium Nonatitanate (Ba2 Ti9 O20) dielectric resonator has been designed and developed to realize a low-noise compact microwave source. The frequency stability of the oscillator is about 5 ppm/°C. It has been possible to get more than 30 mW stabilized output power with Gunn diode rated for 50 mW output power in conventional rectangular waveguide cavity configuration. The oscillator can be mechanical) tuned between 8.4 GHz and 8.6 GHz.
TL;DR: The global view point for all circuit generation of a non-oriented simple graph is considered to minimize the time bound.
Abstract: The global view point for all circuit generation of a non-oriented simple graph is considered to minimize the time bound. Individual circuit vectors are passed through a three-level sieve so that the time consuming connectivity testing for individual circuit vectors is, in general, avoided. Circuits are outputed, as and when, they pass through the sieve so that storage required is negligible.