GENERATOR FOR STANDARD TV SIGNALS

Transcription

1 GENERATOR FOR STANDARD TV SIGNALS Jivko Kostadinov Georgiev, Simeon Nikolov Hristov, Petia Sabeva Stoinova, Nadejda Vasileva Spasova, Technical University- United Technical College Botevgrad, Bulgarie, Keywords: generator, modulator, frequency, converter, microcontroller, encoder The paper describes the results obtained by the development of a generator for standard TV signals intended for measurement and adjustment several television systems. The generator comprises following main blocks: PIC microcontroller, AUDIO generator, RGB encoder, TV modulator, RF converter and amplifiers for the different frequencies. The PIC microcontroller is intended for controlling of the all general functions of the generator and besides for producing the necessary signals that are passed to the inputs of the RGB encoder. The output RF signal is produced directly by a TV modulator in the frequency range 40 00MHz and after conversion by RF converter in the range 30 00MHz.. INTRODUCTION Many different fields of the television technique demand to be used standard test signals, for example, for the measurement and adjustment of cable television networks, repairing of television receivers and for education processes. For these purposes, from the authors is designed a generator, that by utilization of up-to-date integrated circuits and an appropriate software are satisfied all technical requirements at lower production cost. 2. GENERAL BLOCK DIAGRAM In Figure is shown the general block diagram of the designed generator and in Figure 2 are represented the main frequencies of the different blocks. G Hz R AUDIO AMPLIFIER AUDIO out F G MH PIC MICRO- CONTROLLER SYN R G B RGB ENCODER CXA4P/M R2 TV MODULATOR TDA00XS Rfout=40-00MH VIDEO out VIDEO AMPLIFIER SW SW2 F3 RF CONVERTER TUA0XS F2=30 400MHz Corrector STEP Attenua tor LP Filter RF Ampli fier RF out ~220 POWER SUPLAY +33V +V + V LCD INDICATOR Fig.. Block diagram of the TV generator DIGITAL POTENTIOMETER MCP4 SCK SI

2 (a) RFout F, MHz (b) F3 F F F, MHz Fig.2. Output frequency of the TV modulator (a) and frequencies of the RF converter (b). The generator G generates an AUDIO signal with frequency Hz.This signal is regulated and amplified by the potentiometer R and AUDIO AMPLIFIER, respectively and then it is passed to AUDIO out. The unregulated AUDIO signal is fed to the AUDIO input of the TV MODULATOR. The PIC MICROCONTROLLER is used to control the main blocks by an interface I2C and generating the input signals of the RGB ENCODER. The RGB ENCODER receives the signals from the PIC MICROCONTROLLER and the signal 4.433MHz from the generator G2. These signals are converted by the RGB ENCODER in a standard PAL VIDEO signal that is regulated and amplified by the potentiometer R2 and VIDEO AMPLIFIER. From the output VIDEO out this signal can be used as a test signal for many measurements. For a purpose to get RF signals are used the TV MODULATOR and the RF CONVERTER. The TV MODULATOR converts the AUDIO and VIDEO signals which are fed to their inputs to RF signal in the frequency range RFout=40 00MHz. For frequency range F3=30 40MHz is used RF CONVERTER (where F3= F2 F=(30 400)-00 MHz). The converted signal is filtered by a low pass filter connected to the output of the RF CONVERTER. This signal flows via the PIN switches SW and SW2 that are controlled by PIC MICROCONTROLLER. After the switches, the RF signal is passed to the CORRECTOR formed as a PIN attenuator. The program controlled voltage from the DIGITAL POTENTIOMETER corrects the RF signal to a constant level for all frequencies. The corrected RF signal is attenuated by the manually switched STEP ATTENUATOR and amplified from the RF AMPLIFIER to output - RF out. The LCD INDICATOR connected to the PIC MICROCONTROLLER shows the frequency of the output RF signal and the difference between the video and audio carrier frequencies of.mhz or. MHz. 3. MAIN BLOCKS OF THE GENERATOR In the following presentation are described schematic diagrams of the main blocks of the generator. 3.. Generating of the main signals.

3 Figure 3 shows schematic diagram of the RGB ENCODER realized with the integrated circuit CXA 4P/M. The PIC MICROCONTROLLER generates RGB and SYNCHRO signals which are fed to the inputs of the RGB ENCODER. The RGB signals is formed in different combinations consecutive selected by the button B connected to pin 3. +V C VT BFS20 R3 k C2 XT MHz C3 C 22uF 4 R 30 4 U3 VDD OSC OSC2 MCLR VSS PICF84 I/P RB RB RB RB4 RB3 RB2 RB RB0 RA4 RA3 RA2 RA RA B R2,k R3,k R4,k 3xN448 VD VD2 R R k k C R 0p U4 NC NC SCIN NPIN VD3 SYNCIN R NC 8 BFOUT k C 2 RIN C 3 GIN C 4 BIN R X/Y CXA4P/M R0UT G0UT B0UT YCLPC CVOUT YTRAP COUT Vref YOUT FO Iref GND GND2 VCC VCC2 C 330p C3 330p C2 R4 NC R20 4uF/V XT2 4,433 C4 30p C22 R R C2 220,0 C23 220uF/V C24 220,0 YOUT R2 k/% VIDEO out COUT R8 R R C28 4uF/V C2 4uF/V C2 4n C30 R22 4k C3 uf/v Fig. 3. Schematic diagram of the RGB encoder. From these signals and with the signal F=4.433MHz of the Clappe generator realized by the transistor VT, is get a color VIDEO signal at pin 20 of the RGB ENCODER Modulation and converting In Figure 4 is shown the schematic diagram of a modulator realized with the integrated circuit TDA00XS and few external components. The AUDIO and VIDEO signals are fed to the pin 2 and 24, respectively. The generated frequency in a range 40 00MHz and the all parameters of the modulation are determined from PIC MICROCONTROLLER by I2C interface.

4 C0 C +V* 28 VVCCA AudGnd R C38 4,/V C 2 2 T2 AudinFM VIDEO in C3 2 3 R 2,k TFLF AudinAM C3 4n R 2 4 SLF SC2in C3 40n R8 24 Videoin CAS C2 R 23 GNDA R4 R0 C3,2p R 0-B2 R C3 R 20 4k C3 L Nav(D/d=2/0,3) C34,2p 0-C VD2 BB0 C33,2p 0-C2 C32,2p U2-TDA00XS 22 Modout 2 ModGnd 4Nav RF out 8 20 Modout2 TR GNDD 0-B R C30 p R 220 R4 T C2 n R 220 VTUNE C2 AUDIO in VVCCD C28 22n +V* CHGPMP C24 3 p Q R R3 C23 C22 +V* 4 Qx P2 R XT 4MHz +33V C2 C2 Fref=FQ/4 C2 Fig. 4. Modulator. Figure shows the schematic diagram of a converter realized with the integrated circuit TUA0XS converting the signal RFin = F = 00MHz to the signal RFout = 30 00MHz. The concrete frequency of the RFout=F3 is determined by I2C also. VD L BB833 2Nav-2/0,3mm C R4 0 VD BB833 L3 2Nav-2/0,3mm R40 R3 C2 2,2n R38 C4 +33V R42 C8 p C0,8p C p R43 C3 22n 28 2 OA-B2 OA-E2 MIXA MIXAx C 2,2p C C 2Nav MIXB OA-E OA-B OB-B2 OB-E2 OB-E OB-B MIXBx Vvcca CAS IFout IFoutx L4 220nH C8 U-TUA0XS R BAL GNDd GNDa C8 TUNE CHGPMP P0/I0 Vvccd C80 C 0p 0p R4 R C8 3 Q P/I XT3 4,0MHz 4 Qx P2/ADC C p TR3 2Nav C0 C8* C82 C4 RF in =00MHz C84 RF out= mhz Fig.. RF converter. +V

5 3.3. Filtering of the converted signals. In this converter are used frequencies in a outside region of the range MHz and for this reason after its output can be used a very simple low pass filter. Figure shows the schematic diagram of the low pass filter with cut-off frequency Fs = 00MHz and its the transfer (S2) and reflection (S) scattering parameters. PORT P= Z= Ohm IND ID= L L= 2. nh IND ID= L2 L= 2.4 nh IND ID= L3 L= 3.4 nh ID= C2 C= pf ID= C4 C=. pf PORT P= 2 Z= Ohm ID= C C= 4. pf ID= C3 C=.8 pf ID= C C=. pf Fig. (a). Low pass filter. 0 Graph 00 MHz -0.2 ] b [d S b ] MHz MHz -2. S 2[d Frequency Fig. (b). Low pass filter the transfer S2 and reflection S functions.

6 4. CONCLUSION. The described design allows the producing of a universal test generator for an application in many different television fields. By utilization of up- to- date integrated circuits, appropriate schematic resolutions and the software design, are reached very good technical performances at acceptable prices.. ACKNOWLEDGMENT The authors wish to thank H.Hristov and Z.Nentchev, design engineers from TECOM-3 Botevgrad, for their thoughtful suggestions, critiques, assistance and cooperation extended during the design and development of the described generator.. REFERENCES.Georgiev J.K., S.N.Hristov and P.S. Stoinova, TV modulator for cable stations, Electronics 2002,Sozopol 2.Georgiev J.K., S.N.Hristov and P.S. Stoinova, Programmable TV modulator for cable stations, Electronics 2003,Sozopol 3.Georgiev J.K., S.N.Hristov and P.S. Stoinova, Generator for TV test signal, Smolian, Dobrev M.D. and L.T. Jordanova, Receiving of a radio and TV programs by stations and a cable, Electroninvest, S.,.Konov K. and D.Makedonski, Up to date TV receivers, Dios, S..Mishev D., D.Makedonski and J.Jordanova, Satellite and Cable television, Color,Varna,.William O.Grant, Cable television,exton, PA,4 8.Marcelo F. Maggi Video pattern generator, mmaggi@hotmail.com, April, 8.Saal Rudolf, Handbuch zum filterenwurf, AEG-Telefunken,.GV-8, Instruction manual, TV generator PROMAX, Barcelona, 3