ARYAN INSTITUTE OF ENGINEERING AND TECHNOLOGY PROJECT REPORT ON TELEVISION TRANSMITTER Guided By: Submitted by: Janmejaya Pradhan Janmitra Singh Reg : Branch:ECE

CONTENTS INTRODUCTION OF TV TRANSMITTER BLOCK DIAGRAM OF TV TRANSMITTER TV CAMERA SCANNING PROCESS TRANSMISSION PICTURE & SOUND SIGNAL

INTERODUCTION OF TELEVISION Tele means far vision means to see television means to see long distance object by a screen the other name is duradarshana there are two signal are transmitted in television communication system. One is picture signal other is sound signal similarly two type modulation are required one is amplitude modulation another is frequency modulation. Amplitude modulation is used for picture signal and frequency modulation is used for sound signal.

T HE PROCESS OF MODULATION IS SAME FOR BROADCASTING.A TRANSMITTER THERE IS SIGNAL ANTENNA IS USED FOR TRANSMITTING FOR BOTH SIGNAL BUT THE FREQUENCY OF TELEVISION BROADCASTING IN TERMS OF MHZ THERE ARE TWO SEPARATED CARRIER ARE USED FOR PICTURE AND SOUND MODULATION NATURALLY THE SOUND CARRIER FREQUENCY IS GREATER THAN PICTURE CARRIER FREQUENCY. B ECAUSE LOW SPEED THE PICTURE IS TRANSMITTED THE PHOTO OR OBJECT IS TWO NO OF LINE HORIZONTALLY AND VERTICALLY AND CONSTITUTE A VIDEO SIGNAL T V CAMERA CONVERT INTO ELECTRICAL SIGNAL IN T V BROADCASTING NORMALLY MORE THAN 40MHZ IS USED FOR TRANS MITTED SIGNAL INTO ELECTROMAGNETIC WAVE FROM THROUGH AIR AT HIGH SPEED.

PICTURE TRANSMISSION The picture information is optical in character and may be thought of as an assemblage of a large number of tiny areas representing picture details. These elementary areas into which picture details may be broken up are known as ‘picture elements’ or ‘pixels’, which when viewed together represent visual information of the scene. Thus, at any instant there are almost an infinite number of pieces of information that need to be picked up simultaneously for transmitting picture details. However,simultaneous pick-up is not practicable because it is not feasible to provide a separate signal path (channel) for the signal obtained from each picture element. In practice, this problem is solved by a method known as ‘scanning’ where conversion of optical information to electrical form is carried out

BLOCK DIAGRA OF TV TRANSMITTER

TV CAMERA

TELEVISION CAMERA SCANNING PROCESS T v camera performance dual functions finites it converting image of object in front of lance of lance into electrical picture elements. Second this image is done by scanning process by the help of electron beam to produced a electrical video signal the strength video signal is varying according to light intensity in picture eliminate in directly. T v camera convert from object into electrical video signal. The scanning process is breaking photo or frame off object into horizontally and vertically by the help of electronic beam.

SCANNING PROCESS Type of scanning process 1. Progressive scanning. 2.Interlaced scanning. Progressive scanning : Progressive scanning the electronic beam is stated top left hand edge of the picture and it move to the right hand edge the beam also slowly move down words Each frame is divide to 625 horizontal line. The beam scans horizontal trace period with picture elements. When electronic beam is return to left edge for scan for second line of period to horizontal retrace period. this period has electronic beam is of.

R ETRACE PATH IS VERY QUICK OR FASTER THAN TRACE PATH. T HE BEAM SLOWLY MOVE TO WARDS BUTTOM DURING SCANNING PERIOD. W HEN 625 LINE SCANNING COMPLETED THEN THE BEAM IS SUDDENLY MOVE TO THE TOP OF LEFT CORNER OFF ORIGINAL POSITION OF FRAME THE SECOND FRAME SCAN START. T HE SCAN SEQUENCE IS FIRST HORIZONTAL LINE THEN SECOND LINE THEN THIRD LINE THEN FORTH LINE. I N THIS WAY THE VERTICAL SCAN ONCE SO VERTICAL SCAN FREQUENCY IS 25 HZ.T HE PROGRESSIVE SCANNING VERTICAL BLANKING PERIOD IS VISIBLE ON THE SCREEN OUR EYES CAN DESTINY WITH DIFFERENCE BETWEEN ONE TO ANOTHER FRAME AND THIS TYPE NOISE IN PICTURE IS CALL FLICKER.

INTERLACED SCANNING I N I NDIAN BROADCASTING DONE BY INTERLACED SCANNING PROCESS. IN THIS SCANNING THE FRAME REPETATION RATE STANDARD 25/ SEC. E ACH FRAME IS DIVIDE I NTO 625 HORIZONTAL LINE. E ACH FRAME IS DIVIDED INTO TWO FIELD ODD & EVEN FIELD.T HE ELECTRON BEAM IS SCANNING TOP LEFT CORNER TOP WORDS RIGHT SIDE EDGE OF FRAME WITH SLOWLY MOVE DOWN WORDS. D URING HORIZONTAL TRACE THE BEAM IS ON AND DURING RETRACE PERIOD THE BEAM IS OFF. F AST SCANNING IS DONE BY ODD NO HORIZONTAL LINES RIGHT 1, 2, 3, 5….. ETC TO 312 LINES THE BEAM IS SUDDENLY MOVE TO WARDS AFTER COMPLETION OF 3121/2 LINES.T HE BEAM SCAN NO OF HORIZONTAL LINE LIKE 2,4,6,8… ETC IN THIS WAY THE ELECTRON BEAM TWICE OF VERTICAL FOR EACH HORIZONTAL SCANNING. H ENCE VERTICAL SCANNING FREQUENCY IS 50 HZ AND HORIZONTAL SCANNING FREQUENCY IS HZ. I N THIS SCANNING THERE IS NO FLICKER OR VERTICAL RETRACE LINE IS VISIABLE ON THE SCREEN.

COLOUR TRANSMITTER A COLOUR TV TRANSMITTER IS ESSENTIALLY THE SAME AS THE MONOCHROME TRANSMITTER EXCEPT FOR THE ADDITIONAL NEED THAT COLOUR ( CHROMA ) INFORMATION IS ALSO TO BE TRANSMITTED. A NY COLOUR SYSTEM IS MADE COMPATIBLE WITH THE CORRESPONDING MONOCHROME SYSTEM. C OMPATIBILITY MEANS THAT THE COLOUR TV SIGNAL MUST PRODUCE A NORMAL BLACK AND WHITE PICTURE ON A MONOCHROME RECEIVER AND A COLOUR RECEIVER MUST BE ABLE TO PRODUCE A NORMAL BLACK AND WHITE PICTURE FROM A MONOCHROME TV SIGNAL. F OR THIS, THE LUMINANCE ( BRIGHTNESS ) SIGNAL IS TRANSMITTED IN A COLOUR SYSTEM IN THE SAME WAY AS IN THE MONOCHROME SYSTEM AND WITH THE SAME BANDWIDTH.

H OWEVER, TO ENSURE COMPATIBILITY, THE COLOUR CAMERA OUTPUTS ARE MODIFIED TO OBTAIN (B-Y) AND (R-Y) SIGNALS. T HESE ARE MODULATED ON THE COLOUR SUB - CARRIER, THE VALUE OF WHICH IS SO CHOSEN THAT ON COMBINING WITH THE LUMINANCE SIGNAL, THE SIDEBANDS OF THE TWO DO NOT INTERFERE WITH EACH OTHER I. E., THE LUMINANCE AND COLOUR SIGNALS ARE CORRECTLY INTERLEAVED. A COLOUR SYNC SIGNAL CALLED ‘ COLOUR BURST ’ IS ALSO TRANSMITTED FOR CORRECT REPRODUCTION OF LOURS.

S OUND T RANSMISSION T HERE IS NO DIFFERENCE IN SOUND TRANSMISSION BETWEEN MONOCHROME AND COLOUR TV SYSTEMS. T HE MICROPHONE CONVERTS THE SOUND ASSOCIATED WITH THE PICTURE BEING TELEVISED INTO PROPORTIONATE ELECTRICAL SIGNAL, WHICH IS NORMALLY A VOLTAGE. T HIS ELECTRICAL OUTPUT, REGARDLESS OF THE COMPLEXITY OF ITS WAVEFORM, IS A SINGLE VALUED FUNCTION OF TIME AND SO NEEDS A SINGLE CHANNEL FOR ITS TRANSMISSION. T HE AUDIO SIGNALFROM THE MICROPHONE AFTER AMPLIFICATION IS FREQUENCY MODULATED, EMPLOYING THE ASSIGNED CARRIER FREQUENCY. I N FM, THE AMPLITUDE OF CARRIER SIGNAL IS HELD CONSTANT, WHEREAS ITS FREQUENCY IS VARIED IN ACCORDANCE WITH AMPLITUDE VARIATIONS OF THE MODULATING SIGNAL. A S SHOWN IN F IG. 1.4, OUTPUT OF THE SOUND FM TRANSMITTER IS FINALLY COMBINED WITH THE AM PICTURE TRANSMITTER OUTPUT, THROUGH A COMBINING NETWORK, AND FED TO A COMMON ANTENNA FOR RADIATION OF ENERGY IN THE FORM OF ELECTROMAGNETIC WAVES.