Vishal Technical Monitor

BARC Extends Online Application Date for 105 JRF Vacancies, Stipend Rs 31,000 BARC has extended the last date for online applications for 105 Junior Research Fellow vacancies available at the organisations. All the selected candidates will also register for a PhD at the Homi Bhabha National Institute (HBNI). which is deemed to be University of Department of Atomic Energy. Bhabha Atomic Research Centre (BARC) is offering JRF in the fields of physical, chemical and biological sciences, and selected candidates will receive a monthly stipend of Rs 31,000 to begin with, which will go up to Rs 35,000 per month in the third year. Who can Apply for the 105 JRF Vacancies at BARC? The official notification issued on the BARC website says that candidates who have secured consistently good academic record and have attained a minimum of 60% aggregate in BSc and 55% aggregate in MSc from a recognized university, along with a valid score in national level entrance examinations like GATE, NET, JEST an

Alternate Mark Inversion (AMI) Extra information for course - not included in assessment. AMI (Alternate Mark Inversion) is a  synchronous  clock encoding technique that uses bipolar pulses to represent logical 1. The next logic 1 is represented by a pulse of the opposite polarity. Hence a sequence of logical 1s are represented by a sequence of pulses of alternating polarity. The alternating coding prevents the build-up of a d.c. voltage level down the cable. Example of AMI coding of NRZ data and the corresponding clock signal AMI (Alternate Mark Inversion) encoding was used extensively in first generation pulse code modulation networks, but suffers the drawback that a long run of 0's produces no transitions in the data stream (and therefore does not contain sufficient transitions to guarantee lock of a  DPLL ). Successful clock recovery therefore relies on the user not wishing to send long runs of 0's and this type of encoding is not therefore transparent to the sequence of bi

High Density Bipolar Order 3 Encoding (HDB3) Extra information for course - not included in assessment. The HDB3 code is a bipolar signaling technique (i.e. relies on the transmission of both positive and negative pulses). It is based on  Alternate Mark Inversion (AMI) , but extends this by inserting violation codes whenever there is a run of 4 or more 0's. This and similar (more complex) codes have replaced AMI in modern distribution networks. HDB3 Encoding Rules The encoding rules follow those for AMI, except that a sequence of four consecutive 0's are encoding using a special "violation" bit. This bit has the same polarity as the last 1-bit which was sent using the AMI encoding rule. The purpose of this is to prevent long runs of 0's in the data stream which may otherwise prevent a DPLL from tracking the centre of each bit. Such a code is sometimes called a "run length limited" code, since it limits the runs of 0's which would otherwise be produce

Satellite frequency bands APPLICATIONS Satellite frequency bands Satellite technology is developing fast, and the applications for satellite technology are increasing all the time. Not only can satellites be used for radio communications, but they are also used for astronomy, weather forecasting, broadcasting, mapping and many more applications.  With the variety of satellite frequency bands that can be used, designations have been developed so that they can be referred to easily.  The higher frequency bands typically give access to wider bandwidths, but are also more susceptible to signal degradation due to ‘rain fade’ (the absorption of radio signals by atmospheric rain, snow or ice). Because of satellites’ increased use, number and size, congestion has become a serious issue in the lower frequency bands. New technologies are being investigated so that higher bands can be used.  L-band (1–2 GHz) Global Positioning System (GPS) carriers and also satellite mobile phones, such as Iridiu

T1/E1 Basic Bit Error Rate Test Overview The Bit Error Rate Test (BERT) application generates/detects unframed, framed, and fractional data that are defined in Pseudo Random Bit Sequence (PRBS). In addition to these, drop and insert capability is provided. A variety of standard data patterns are available for test purposes including static and user selected patterns. To open BER application, navigate to T1/E1 Analyzer > Intrusive Test > Bit Error Rate Test. Select the card on which BER test has to be performed. The screenshot given above displays the BER test application running on Card1: The functionality of the PRBS data stream is illustrated in the figure below: Framing Patterns selection for T1/E1 The framing patterns available in BER test are Unframed, Full-Framed, Fractional without Drop and Insert (D&I) and Fractional with Drop and Insert modes. These can be selected from the drop-down menu in the "Full-Fractional-Unframe" section. Unframed T1/E1:  Entire T1/

Parameters ASK FSK PSK Variable characteristics Amplitude Frequency Phase Bandwidth Is proportional to signal rate (B =(1+d)S),d is due to modulation & filtering ,lies between 0 & 1. B=(1+d)×S+2Δf B=(1+d)×S Noise immunity low High High Complexity Simple Moderately complex Very complex Error probability High Low Low Performance in presence of noise Poor Better than ASK Better than FSK Bit rate