aj ka viva

7/31/2019 aj ka viva

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Methodology : Since the using ACD based on GPS is costly, our aimto reduce the system implementation cost by using microwave link. Inthis system the signal post which shows green or red signal , is beingconverted using modulation in the range of 2-3GHz and beingtransmitted every time .there is separate frequency for the UPLINK &DOWNLINK pathway .the receiver presents in the LOCO ACD willreceive the signal .This high frequency received signal isdownconverted to baseband frequency. Baseband frequency signal isthen passed through ADC unit &signal is converted in binary signalwhich is passed to the microntroller PIC16F72 that uses the DM&PM617 Intel chipset through which it control visual display displayinggreen or red. It also after 3-4 sec. sound unit which is a buzzer getactivated and driver get alarm of presence of another train in the sametrack. If driver does not respond within 3-4sec. the AUTOMATICBRAKE UNIT is get activated and avoid the risk of collision.

At receiver the recived signal is passed through ADC andthen to microcontroller to make decision of colour i.e RED, GREEN,YELLOW of separate received frequency and a part of this signalidentified by microcontroller is also sent to alarm to generate sound of distinguished tone.If the driver in case of danger does not respondwithin 5 sec , then AUTOMATIC BRAKING UNIT get activated &stop the train automatically .


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Microwave Link Structure . The basic components required foroperating a radio link are the transmitter, towers, antennas, andreceiver. Transmitter functions typically include multiplexing,

encoding, modulation, up-conversion from baseband or intermediatefrequency (IF) to radio frequency (RF), power amplification, andfiltering for spectrum control. Receiver functions include RFfiltering, down-conversion from RF to IF, amplification at IF,equalization, demodulation, decoding, and demultiplexing. Toachieve point-to-point radio links, antennas are placed on a tower orother tall structure at sufficient height to provide a direct,

unobstructed line-of-sight (LOS) path between the transmitter andreceiver sites.

Microwave System Design . The design of microwave radio systemsinvolves engineering of the path to evaluate the effects of propagation on performance, development of a frequency allocationplan, and proper selection of radio and link components. This designprocess must ensure that outage requirements are met on a per link and system basis. The frequency allocation plan is based on fourelements: the local frequency regulatory authority requirements,selected radio transmitter and receiver characteristics, antennacharacteristics, and potential intrasystem and intersystem RFinterference Bandpass filter: bandpass filter having appropriatepassband is designedFrequency UP and DOWN converters: Varactordiode or FET transistor is generally is used for frequencymultiplicatrion & demultiplication.

Small capacity systems generally employ the frequencies less than 3GHz while medium and large capacity systems utilize frequenciesranging from 3 to 15 GHz. Frequencies > 15 GHz are essentially usedfor short-haul transmission.


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MICROWAVE LINK DESIGNThe objective of this project is to successfully implement, test, andapply a working 10 GHz microwave communication link. Amicrowave link is a wireless communication system that sends andreceives information through the conversion of electrical signals topropagating electric fields. An electrical signal is set up by atransmitter and is coupled through a microwave network andpropagated into free space with the use of an antenna. The signal thentravels through space to a receiver. The receiver has an antenna thatwill pick up the transmitted electric field and convert it back to anelectric signal, which is then interpreted by the receivers associatedcircuitry to recover the original signal. Then, using a connectioncalled an Attachment Unit Interface (AUI), the signal is routed to aload device. The load device then uses the signal for whatever itsapplication may be. The project will be carried out in different stages,some of which have been completed to date.Unfortunately, as shall be explained, due to time constraints, We wereunable to complete all that we hoped to.

SYSTEM DESIGNThe overall microwave link will have two units: the low frequencytransmitter unit and the high frequency transmitter unit. The low and

high reflect the frequencies to which each unit is tuned. Thesefrequencies are 10.178 GHz for the low frequency unit for UPLINKand 10.323 GHz DOWNLINK for the high frequency unit. It mayseem peculiar to label such close frequencies as high and low, but forthe ease of explanation, this is how they are labeled. As can be seen,the difference between these two frequencies is 145 MHz. Thisfrequency, called the Intermediate Frequency (IF) is what enables the

link to operate.


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The Antenna

The system can operate using various antennas and decisions upon

choice will depend on application. The testing will initially be donewith a direct X-band waveguide connection as the transmission linebetween the transmitter and the receiver to verify the transceiver isfunctioning properly. X-band waveguides function for frequenciesbetween 8 and 12 GHz, so our 10 GHz application fits in the X-bandquite well .For this link height of transmitter and receiver isconsidered 0.5m.

The GunnplexerThe transmission and reception of signals will be dealt with using 10GHz Voltage controlled oscillator transceiver modules calledGunnplexers. Ultimately, any type of 10 GHz oscillator could havebeen chosen, but due to the fact that Gunnplexers are relativelycompact and are easily tuned to work with IF circuitry, they are agood choice to be used for


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The Intermediate Frequency (IF) StripAfter signal transmission, the IF strip plays an important role inreceiving the signal. The IF strip is a subsystem that filters

disturbances from Frequency Modulation (FM) transmissions. TheIF Strip uses a high filter and a low pass filter that ultimately form asort of band pass filter that has a good response between 82 and 210MHz. Following the IF Strip in the system is the Frequency-ShiftKeying (FSK) Demodulator .


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generate a 10 GHz carrier frequency, slightly tune the oscillator to adesired frequency and transmit that frequency out an X-bandwaveguide opening. When receiving, Gunnplexers can output aheterodyne signal. It is important to note that there are limitations onthe use of Gunnplexers as transceivers for systems. The system willoperate in half duplex due to limitations that shall be discussed lateron. The received signal from our Gunnplexer works in conjunctionwith an IF Strip to bring our operating frequency from a 10 GHz bandsignal down to a 145 MHz IF .


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The FSK DemodulatorThe FSK Demodulator is an important part of the overall system. Its

purpose is to recover the original signals waveform from the IF

signal. The original signal can be recovered from the IF signal byperforming wideband FM demodulation [1].

The Output BufferThe output buffer is a system component that level shifts, filters andamplifies the signal prior to routing the microprocessor. Thiscomponent has as a dual the FSK Modulator. That is to say, the task

the output buffer accomplishes is accomplished in the reversedirection by the FSK Modulator. Hence the Output buffer isconnected to the receiver side of the system and the FSK Modulator isconnected on the transmitter side of the system [1]. The FSKModulatorContrary to what one may believe, the FSK modulator does notperform the opposite task of the FSK demodulator. In fact, by itself,

the FSK modulator does not even perform any modulation. The FSKModulator is actually a system device that prepares the signal fortransmission and then sends it off to the Gunnplexer to be modulated.It DC shifts the zero baseline of the original signal to a desired valueand amplifies the signal to a desirable value .

FSK modulator, which sets up the signals to be modulated by the

Gunnplexer system at a carrier frequency in the 10 GHz band, isdesigned using a Mini-Circuits PLP-21.4 low-pass filter, and a Burr-Brown OPA603 non-inverting current feedback amplifier. A Mini-Circuits T2-1 balun transformer is also used to better match the outputof the low-pass filter to the AUI input.


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Gunnplexer AssemblyThe Gunnplexer assembly consists of a T4-1 Balun transformer,several resistors and capacitors chosen to meet the necessary

specifications, and the Gunnplexer itself. Though currently, noGunnplexer is connected to the circuitry, there are terminals on thecircuit board ready to connect to the three diodes of a Gunnplexer.The Gunn diode terminal is connected directly to a terminal for biasvoltage which is in parallel with a 4.7F Tant alum capacitor and a0.1F ceramic capacitor. The Mixer diode terminal is connected to aT4-1 balun, which, on the other side, is directly connected to the IF

strip input. The varactor diode terminal, as mentioned above connectsdirectly to output of the FSK modulator circuitry. .

IF StripThe IF strip, which as we know, connects to the mixer diode inputterminal after having been matched with a balun, works at anoperating frequency of 145 MHz. The IF segment of the system hastwo jobs: filtering and amplification. The IF strip is the thirdsubsystem that has been integrated into the design of Board 1 of thePCBs [2].The filters used are a PHP-100 High Pass Filter and a PHP-200 LowPass Filter and the amplifiers used are MMIC MAR-6. Two suchamplifiers are needed in the IF strip. All components in the IF stripwere used in compliance with the specification.FSK Demodulator

Once the received signal has passed through the IF strip, it can thenbe demodulated. The FSK demodulator is the subsystem thatperforms this task. The FSK demodulator was designed using a Mini-Circuits MAR-4 operational amplifier, a T4-1 balun and a MotorolaMC13155 microchip and is located on Board 2 of the PCBs [2].4.1.5 Output BufferThe output buffer is connected to the output ports of the FSKdemodulator on one end, and to the input of the AUI port on the other


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end. It is designed using four main components: two OPA603amplifiers, a PLP-21.4 low-pass filter, and a T1-1 balun transformer.The output buffer is located on Board 2 in conjunction with the FSK

demodulator .


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ABU: ACDs interface with Loco brake system Loco ACD InterfacesLoco ACD interfaces with various devices in the locomotive, which

arebriefly explained below:4.1. ABU: ACDs interface with Loco brake system Figure -

ABU is the Automatic Braking Unit which is connected to theexistingLocos Braking System. ABU applies either emergency or normal

(service)brakes to the train based on the commands send by the Loco ACDdepending on the situations perceived by it. ABU acts as an interface

between the Loco ACD and the Locos Braking System. ABU has provision to put it into auto mode or manual mode.

Significance of NB NOT OK IN ABU: This indication does not

necessarily indicate ACD / ABU defects. The indication may appear,if


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brake power of train is poor. The driver should take brake feel testwhenthis indication appears on ACDs Drivers Console.

Significance of Emergency Brake: If train speed is not gettingcontrolledthrough application of Normal Brakes, or the Normal Brake itself isineffective, ACD resorts to Emergency Brake application to regulatetrainspeed to desired limits.Based on their Construction, ABUs can be categorized into two types,namely the double handle ABUs & the single handle ABUs. SinglehandleABU is a modification of double handle ABU. Differences betweentwo

Whenever the Loco ACD fails (i.e., in the drivers console whenACD-MLED glows) ABU is required to be isolated using the isolatinglever(s).ACD - M indication may appear because of GPS failure, speedometer


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input problems, ICS failure etc. ABU needs to be isolated when ACDis in ACD-M mode & does not permit to move/work or when ABU isitself is not function properly.

Automatic Braking Unit Rotex Make(single handle)

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