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This letter explores geometrical optics-based raytracing in combination with modal analysis to realize an open cavity structure as an advanced variant of the resonant cavity antenna (RCA). Additional ray confinement has been ensured by determining accurate phase-locking conditions as demonstrated for the first time. Its combination with the analysis of the cavity mode has also been introduced to determine the optimum design parameters, achieving improved radiation properties. With respect to a reference RCA reported earlier, the proposed approach exhibits a remarkable improvement in gain by 4–9 dB, resulting in about 17 dBi peak value consistently over the full 18% matching bandwidth. This is resultant from an increase in aperture efficiency, typically from 27% to 74%. This is achieved without any compromise with the cross-polarization property. The sidelobe level improves over the band except in higher frequency in H-plane. The proposed concept is commercially viable, showing significantly advantageous features.

A novel multihorn antenna using the substrate integrated waveguide (SIW) technology is discussed in this communication. Conventional SIW-inspired horns, being the extensions of planar H-plane horn antennas, portray a fan-shaped beam, with a narrow H-plane and a wide E-plane radiation characteristics. The present design employs this feature to produce a crossed horn, in which both E- and H-plane radiations can be realized by individually exciting the two sectoral horns, while terminating the other port to a matched load. When both the ports are excited, a spot beam is realized, representing a pattern similar to that of a pyramidal horn. Such an antenna should find its potential applications in systems requiring radiation switchability/pattern diversity from a single embodiment.

An innovative measurement methodology is developed and successfully implemented for a spot beam antenna and payload characterization of high-throughput satellites (HTSs) in a compact antenna test facility (CATF). With the developed measurement methodology, total measurement time and measurement setup duration are reduced by more than 70% with respect to conventional measurement techniques. The proposed methodology is successfully implemented in multiple spacecraft (SC) of the Indian Space Research Organisation (ISRO).

Face recognition has a large extent of applications from individual recognizable proof and reconnaissance to electronics showcasing and publicizing for chosen clients. There are various advances in facial recognition, for example, pre-processing, feature extraction, and grouping, where feature extraction and grouping are utilized to acquire the greatest precision. In this paper, diverse feature extraction methods, for example, A.A.M, A.S.M, template-based, Gabor-features, and a few are basically surveyed. Aside from these, the various kinds of neural classification systems, for example, backpropagation, convolutional, radial-basis-function, and so on in the space of face recognition, are investigated. The method and calculations created in the present writing are examined, and it is uncovered that every system is one of a kind and has ideal execution. This assessment further makes a relative examination of these frameworks reliant on their focal points and imperatives.

Design and Implementation of gesture based human computer interface using microcontroller, image processing and standers computer system is presented. The purpose of design system is to solve real time problem of any disable persons using hand movement and performs basic task by recognition of static and dynamic gesture of hand. The propose system work with the classification of hand gesture with many sensors mounted at wearable gloves. The practical implementation is in the form of glove equipped with Accelerometer sensors for sensing hand movement and transmitter receiver module that assists the disable persons to communicate with world in natural way where user can transmit and receive the original data without need any other mode of communication. The main purpose of this paper is interaction of human with computer interface (HCI) that connects man and machine. The combined static and dynamic human gesture can be recognized with set of rules and regulation based on permutation and computation for an input signal of microcontrollers. All this instruction will be encrypted by the help of Advance Microcontroller. Basically this hand gesture recognition is based on three main phases-detection, tracking and recognition. This paper provides existing interaction related to gesture recognition system for human computer interaction and try to implement it in prototype.

A low-power VLSI design technique is currently needed for a digital circuit with optimization of a trade-off between power dissipation and delay parameters of circuits. This paper explores a low-power VLSI design methodology, gated leakage transistor (GALEOR) and increases a resistive trail between power supply node and ground node with reducing the leakage current flowing through the circuit. In GALEOR leakage power technique, two gated leakage transistors are inserted in convention CMOS circuit with MOSFET mechanism that utilizes diode by shorting gate terminal with drain terminal. We show the comparative analysis between GALEOR technique and conventional CMOS technique that we perform on basic digital gate circuit with SPICE programming by HSPICE EDA tool.

A quasi-optical design approach has been proposed to realize a resonant cavity antenna (RCA) for significant improvements in the gain characteristics. The ray-tracing technique of geometrical optics has been successfully used. About 17 dBi boresight gain has been achieved over the 18% impedance bandwidth of the antenna as evident from the experimental data. This approach should find several applications and may be useful to explore other variants of RCA configurations.

Compact antenna test ranges are used for fast and accurate measurement of satellite antennas and payloads. The measured performance of compact range feed dictates the quality of Quiet zone at CATF. A Dual Linear Q/V-Band feed compliant to standard compact range feed specifications was designed. The designed feed will be used for RF characterization of advance communication payload. In this paper, design aspects and simulated results of proposed feed are discussed.

An innovative test methodology is proposed and implemented successfully for characterization of advanced high capacity multi-beam satellite's payloads at Compact Antenna Test Facility (CATF). Payload characterization in CATF is a mandatory test as it provides end-to-end performance of payload in radiated mode, simulating on-orbit conditions. Usually quantitative measurement of each payload parameter for each transponder is performed at the location, where In-orbit-test (IOT) is planned. To achieve this satellite is moved using CATF DUT Positioner such that geographical IOT location is aligned to Nominal Plane wave Axis of CATF. This method is commonly used for antennas having single coverage area/footprint. In case of multiple beam spacecrafts, characterization of all beams may not be possible at a single location due to sharp roll-off of the beams (away from location). Hence, characterization is required to be carried out at each beams peak location. The proposed method is validated by means of measurement example and implemented successfully for characterization of multi-beam spacecrafts.

A new design of Fabry-Perot cavity antenna (FPCA) has been presented with a unique as well as the most desirable feature of very high-gain maintained over its wide matching bandwidth. About 15.5 dBi average broadside-gain has been achieved over the 19% matching bandwidth. A flat-gain characteristic has been attained using a specially designed conical sidewall. In addition to that, the sidewall will play an important role in reducing the mutual coupling arises due to nearby RF elements. About −16 dB and −19 dB side lobe levels have been obtained satisfactorily in two principle-plane patterns (E- and H-plane) respectively. The cross-polarization purity of the antenna is maintained reasonably below −25 dB over the frequency band.

Compact antenna test ranges are used for fast, precise and real time measurement of antenna and payload parameters. ISRO has established a Compact range at Bangalore and has a rich experience of characterizing more than 33 satellites and 200 subsystem level antennas over wide frequency range from 1–40 GHz. The standard set of compact range feeds comprises 7 dual linear polarized and 2 single linear polarized feeds in the range of 1–40 GHz. In case of satellites with payloads in lower C, Nor C and Upper ext. C-band, 3 compact range feeds should be used for performing payload characterization which consumes considerable test set up time. In this view, an ultra-wide C-band (65% Bandwidth) is designed covering the above mentioned frequency bands. In this paper, design methodology and simulation results of the proposed feed are presented.

Compact Antenna Test Facility (CATF) facility is extensively used for evaluating the antenna pattern and payload performance for all communication satellites in the integrated condition. Operating frequency range of the CATF is from 1-40 GHz. Standard feeds are available in CATF, which will cater testing in the frequency range from 1–40 GHz. Facility can also be used as standard far-field range (By-passing the reflectors and in direct Line Of Sight: LOS) for limited characterization of antennas in the frequency range less than 1GHz. With an increase in the application of UHF frequency usage in the spacecraft sphere, it is required to extend feed capability in the lower operating frequency range of facility. In view of this, it was proposed to design and develop an UWB antenna operating in the frequency band from 200 MHz - 1 GHz so that facility measurement capabilities can be extended. In this paper, design aspects of antenna, feeding network, fabrication, pattern and gain measurement procedure are discussed. Comparison of simulated & measured pattern and gain values shows good match between them.

An innovative design of Ultra Wide-band (over 55% fractional bandwidth) and Low X-pol (Axial Ratio (AR) ≤1dB) helical antenna is presented in this paper. Presented design is generic in nature and can be implemented in any frequency band. We have demonstrated the same in S-band (2.1-3.7 GHz) to meet our internal application. The effect of spacing between turns, number of turns and pitch angle of helical conductor over axial ratio is investigated and presented here. Peripheral feeding technique is used in the design and the off-axis AR within ±100 from the bore sight is ≤ 1 dB over the band. An ultra wide band impedance match between helical conductor and 50 ohm coaxial feed line is achieved by introducing a matching section in between. The matching section presented here is novel, since it is an integral part of the helical conductor section and thus made out of same conductor wire. A minimum of −10dB input reflection coefficient (S11) over the desired band 2.1 GHz to 3.7 GHz is achieved. Further, near band center (2.9 GHz) demonstrated S11 is better than -30 dB using this method. Details of design, modeling in CST (Computer Simulation Technique), and fabrication of the antenna along with the comparison of simulated and measured parameters are presented. An excellent match is observed between simulated and measured results.

In this research work, an attempt has been made to investigate the gas tungsten arc welded Monel 400 plates using ENiCu-7 for its mechanical and corrosion properties. Microstructure examination reveals the coarse grain formation of Ni-Cu phase in the heat affected zone (HAZ) and well defined dendrites are observed in the weld region. Tensile tests showed that fracture occurred at the weld interface and the ultimate tensile strength of the Monel weldment is found to be 515 MPa. Furthermore hot corrosion studies were performed on the different zones (Weld, HAZ and Base metal) of Monel 400 exposed to the thin film of molten salt environment of Na2SO4 - 60% V2O5 at 600°C. It was found that corrosion was extremely severe on the fusion zone after exposed to 50 cycles. The corrosion products were characterized using the combined techniques of optical microscopy, XRD, SEM/EDX analysis

Nonwovens have the most complex morphologies in textile materials and they are often being compressed in a range of applications. The morphology of a typical nonwoven is defined in terms of fiber orientation, fiber volume fraction, number of fiber-to-fiber contacts, distance between the contacts, porosity, and pore size distribution. In this study, an attempt has been made to predict the morphological characteristics of nonwoven materials under the state of compression. A concept of compression ratio has been introduced in predicting the fiber volume fraction at a defined level of compression strain that has significantly influenced the other morphological characteristics of nonwoven materials. A mechanistic model of pore size distribution of nonwoven has been proposed by updating the structural and morphological parameters under predefined compressive stresses. A comparison has been made between theoretical and experimental pore size distributions of compressed nonwoven fibrous materials. In addition, the out-of-plane fiber orientation distribution was experimentally obtained by analyzing the two-dimensional (2D) cross-sections of fibers in the thickness direction.

It is very essential to perform Passive Inter Modulation (PIM) measurement in multi-band communication satellites to avoid unwanted interference. Since source of PIM product can be any metallic or ferromagnetic objects, etc. it is very important to precisely identify the source of PEVI i.e from external environment or satellite transponder chain. For this reason, before conducting any PEVI measurement at satellite level in any anechoic chamber it is usual practice to measure the inherent PIM level of the chamber at measured frequencies. In this paper, procedure for PEVI characterization at satellite level is discussed. Also, one case study is discussed when, PIM product was observed in one satellite, the sequence of operations that were carried out to precisely identify the source of PEVI and corrective action that was taken to suppress them.

In a spacecraft, the Electro Explosive Devices (EED) are used for the appendages deployment activities like Antennas Deployment, Solar arrays deployment etc. EED electronics package provides the required excitation to fire the SQUIB. During the launch phase, the spacecraft experiences a high level of Electromagnetic (EM) radiation. The EEDs should not get enabled due to the EM radiation. EMC analysis was carried out on EED package to assess the safety margin for the squibs, when it is subjected to the radiated E-fields and conducted noise. Micro-cap and CST cable studio software's are used to simulate conducted susceptibility and radiated susceptibility EMC margins respectively.

This paper describes the various challenges experienced and their resolving techniques during RF characterization of multi beam onboard Tracking Antenna in Compact Antenna Test Facility (CATF) of ISRO Satellite centre (ISAC), Bangalore. ISAC-CATF has rich experience of successfully testing 12 spacecrafts covering wide frequency range from L-band to Ka-band with Linear and circular polarization having single and multiple beams. Challenges experienced in RF characterization of onboard Ka-band Tracking antenna and special requirement of zero-g are also discussed. ISRO’s experience in transponder characterization of multiple spot beam antenna is shared. Keyword-Compact range, Payload antenna, radiation pattern, Spot beam antenna , Multi-beam antenna, Tracking Reciever

This paper will describe the various challenges experienced and their resolving techniques during RF characterization of spacecraft onboard antennas in Compact Antenna Test Facility (CATF) of ISRO Satellite centre (ISAC), Bangalore. ISAC-CATF has rich experience of successfully testing 8 spacecrafts covering wide frequency range from L-band to Ka-band with Linear and circular polarization. Effect of spacecraft body and its mounting location on low-gain, wide beam Telemetry and Telecommond Antenna and criticality in measuring cross-pol component of payload antenna is discussed. Challenges experienced in RF characterization of onboard Ka-band Tracking antenna and special requirement of zero-g are also discussed. ISRO's experience in transponder characterization of multiple spot beam antenna is shared and spacecraft level PIM measurement in presence of metallic range reflectors is presented.

Magnetic field dependence of transport critical current density (J c) of a polycrystalline YBCO superconductor in field cooled and zero field cooled cases have been studied experimentally. The measured J c value when the sample was cooled in a field (FC) was always larger than that measured for a zero field cooled (ZFC) case in the same magnetic field. We also observe (i) a peak in the field dependence of the ratio of J c in FC case to that of ZFC case and (ii) an anomalous rise in J c in ZFC case with increasing field. These observations are explained as a signature of two types of regions (intergrain and intragrain) in sintered specimens.