PATTERN GENERATOR

Experimental Purposes

1 Getting to know the basic Pattern in the pattern generator.

2 Measuring standard composite video and Voltage on each Pattern.

3 Measuring the modulated wave on the video modulator.

4 Measuring IF video.

Circuit diagram

Tools and materials in used

A Pattern Generator signal TV, LODESTAR CPG-136 74

An Oscilloscope 40 MHz

A Passive Probe

A Power Supply

A BNC to BNC 75Ω cable

A BNC to RCA 75Ω

A T connector

Experimental Procedure

1. Set-up equipment look like in the circuit diagram
2. Connect the Pattern Generator with power source 8, 5 V, and then push ON the instrument.
3. Pattern generator output switches on and observe put on VIDEO waveforms for each pattern.
4. Observe and picture synchronizing signal and horizontal blanking, vertical blanking, front and rear porch, and image information of each pattern
5. Images and specify voltage waveforms.
6. Pattern generator output switches on and observe put in the IF waveform for each pattern and frequency measurement.
7. Image of the wave form and specify voltage.
8. Image signal for one frame (still image) in composite video, determine the level and period.

Basic Theory

CPG1367A is designed for repairing and adjusting any defect on TV set in PAL system. The RF rang is covering from VHF CH3‐CH4 and including color pattern, white raster and for basic patterns. The unit is used of IC circuit, air variable capacitor inner tuner and crystal controlled progressive scanning circuit. Such design for of cute and portable type is really an efficient instrument for TV set servicing industry.
Features of CPG1367A:
-The employment of IC achieves high stability and accuracy.
- Color pattern for testing PAL system TV color circuit.
- Four basic pattern as dots, square‐crosshatch, vertical lines and horizontal lines for testing and adjusting most of TV circuits.
- White resters pattern is used for testing purity and white balance.
- Battery or AC adapter operation.
Specificationsof CPG1367A:

A Pattern Generator or Generator Digital Pattern is an electronic testing equipment or software used to generate the stimulation of a digital electronics. Digital electronic stimulation of certain types of electrical wave form varies between two voltages that match the conventional two-logic ('logic low' and 'logic high' or '0 'and the '1'). The main purpose of the digital pattern generator is to stimulate the input of digital electronic devices. A digital pattern generator is a synchronous digital stimulus sources, a pulse generator has the objective to generate electrical pulses of various shapes, they are mostly used for testing in the field of electric or analog.

Various kinds of image patterns in the Pattern Generator are as follows:

a. Dot

To check and adjust the static convergence in the middle of the screen with a low brightness. This should be done according to the television manufacturer's instructions.

b. Crosshatch

Plaid pattern with horizontal lines and vertical lines with the background color of black and white color line.

1) To check and adjust the horizontal and vertical dynamic convergence and the convergence angle.

2) By linearity of deflection the correct horizontal and vertical, horizontal white lines should be a rectangular equilateral.

If this line is not sharp and visible lower intensity than the horizontal line, the amplitude response is possible recipients will not be enough.

c. White

This pattern contains a signal 100% white (without color information) with alternating burst.

1. Images for constant brightness on the entire screen

2. Color picture tube for setting a good white

3. Limitation of fire flow on the color picture tube.

4. For the video recorder is ideal pattern for the current settings. It can also to set the FM demodulator (setting white level).

d. Color

Color beam consists of 8 vertical color bar standard and a reference beam horizontally. Beams 8 colors are arranged in order of depreciation luminance. From left to right beams D color is white, yellow, cyan, green, magenta, red, blue, and black. This pattern is used to set the operational control of the receiver at the correct position. Horizontal beam (white level) on the bottom of this pattern is used as a standard when set the amplitude of color differences in correlation with luminance signal in the picture tube. Signals can be used for resetting the signal amplitude of the demodulator circuit and the matrix, as the output can be compared with the reference beam. In addition to the above purposes, this pattern can be used to check the overall color appearance. So can also be used checks and settings on the receiver or VCR:

1. Lock Inspection burst.

2. AGC examination of color and which create the color.

3. Examination series reactance of the subcarrier regenerator.

4. Examination of the regenerator subcarrier synchronization.

5. Checking circuit identifier (identification) PAL.

Signal Synchronization

Synchronization signal is a signal that is always given periodically and remains, serves to drive a raster scanning path in every television set so that the formation of the video signal into an image and the exact arrangement will remain the same as the original position in the field of raste camera (picture production), therefore the synchronization signal is always supplied along with the video signal sent anywhere. For the formation of this raster scanning system will require two kinds of synchronization are:

- Namely the horizontal synchronization signal to the horizontal scanning provided at each horizontal retrace.

- Vertical sync signal is for vertical scanning provided on each vertical retrace.

Video signal which is equipped with synchronization signals called the complete video signal (Composite Video signal / CVSl), while for color video signal is called Color Composite Video Signal (CCVS). Because the video signal has been added color information signals, i.e. signals and signal Burst Color Sub Carrier.




Result

PATTERN	VIDEO		IF
	Vpp	Period	Vpp
Dot	0.29 Vpp	6.2µs	0.12Vpp
Cross Hatch	0.3 Vpp	6.2 µs	0.12 Vpp
Vertical Lines	0.28 Vpp	6.2 µs	0.12 Vpp
Horizontal Lines	0.29 Vpp	3.1 µs	0.12 Vpp
Raster	1.2 Vpp	1.7 µs	0.05 Vpp
Color	2.2 Vpp	1.8 µs	0.1 Vpp

CONCLUSION

1. Voltage at all about the same video system.
2. At the time of the IF mode is turned down because the amplitude of the voltage will also be down
3. IF output frequency is also almost the same because there is no significant difference in amplitude.
4. Tension on the composite video is lower than the voltage on any other video system

VIDEO MODULATOR

Objectives:

1.Measuring the frequency spectrum of video transmission.

2.Determine the image carrier frequency range and sound carrier frequency.

3.Specifies the bandwidth on video transmission.

4.Specify the type of modulation on the picture and sound

Equipment Used:

1 Video modulator (VCD / VTR / video sender).

1 Spectrum Analyzer.

1 cable connector RCA- BNC.

Circuit diagram:

Introduction:

How to transmit image signal which the amplitude is modulated similar to a radio broadcasting system that has been known.
In both cases, the amplitude of a carrier wave radio frequency (RF) is made varies with the modulating voltage. The modulation is a signal of fundamental frequency (baseband).
On television, this baseband signal is a composite video signal. Television broadcast is similar to a radio system, but includes pictures and sound.
Sound signal emitted by joining it in frequency modulation (FM) on a separate carrier wave transmitter in the same channel as the image signal.

This image signal means a modulated carrier wave.
The video signal is a signal for a picture tube. Video signal for the television audio is correspond to the sound system signal. Details for the AM image signal (amplitude modulation picture) and an FM voice signal.

Figure 2.a shows the frequency spectrum of video transmission that produces an image signal comprising AM picture carrier frequency (center frequency) and sound carrier frequencies (frequency side of the upper and lower side frequencies) - without VSB, while Figure 2b shows the frequency spectrum in transmission generate video image signals of AM frequencies only have the upper side only (with VSB).

A variation of DSB is used for broadcast TV. Under the FCC requirements, the standard video signal occupies a bandwidth of 4.5 MHz. The sound signal is separate and is transmitted at the upper edge of this signal. When carrier is shifted to bandpass, this one sided bandwidth becomes 9 MHz. This is nearly ten times as large as the total bandwidth occupied by all the channels of the AM radio. Use of SSB modulation would cut this in half but SSB is not used for video signals because of the complexity of the SSB receivers. TV manufacturers particularly American companies were instrumental in setting these standards like to keep the cost of the TV’s as low as possible so SSB receivers are not used.

This filter takes in a small part of the upper edge of the lower sideband, starting from -1.25 MHz. The signal is attenuated in this range from -1.25 MHz to -.75 MHz. From here on to 4 MHz, the signal is transmitted full strength. At 4 MHz it is once again attenuated down to 4.5 MHz so as not to interfere with the sound carrier which is demodulated separately. The shaded portion is what is transmitted.

The term vestigial is used since a tiny trace part of the lower sideband is also included in the transmission. The net result is that instead of transmitting a 9 MHz signal, we transmit only 6 MHz, the standard video signal today.

Unlike voice signals which have no components near the zero frequency, Video signals are very sensitive to their low frequency content. Distortion in these components degrades the picture. So extra care has to be taken to make sure that all the low frequency components (which are located in the center) are transmitted without distortion. VSB modulation transmits these low frequencies at the twice level. The motivation for filtering the signal in this way also comes from the desire to use a diode demodulator which requires an explicit carrier. But to recover the carrier we need to go a little to the other side of the carrier frequency and take in an attenuated part of the signal because of the limitations of practical filters. The development of this filter was a function of a compromise between bandwidth and the TV receiver complexity.

The new HDTV standard is also based on VSB.

Lecture Video for Amplitude Modulation:

Experimental Procedure:

1.Calibrate the Spectrum Analyzer by determine the reference spectrum.

2.Set-up instruments just like in the picture above.

3.Turn ON the instrument.

4.Measure the video modulator output (RF) using the Spectrum Analyzer and observe the frequency spectrum.

5.Draw the frequency spectrum.

6.Determine how much is the images carrier frequency, voice carrier frequency, and the difference between.

7.Observe the spectrum, determine the type of modulation used in transmission by changing the SPAN FREQ (reduce the scale).

8. Draw the multiples frequency spectrum from it's frequency base.

Question:

1.What system is used in the video modulator?

2.From step 6, how do we know what types of modulation?

Experimental results:

Image of Frequency Spectrum	Information
	Ref = 102dBμ BW = 100 KHz CF = 5 MHz CP1ΔF + 4.32 MHz 2 MHz / DIV ΔV + 18.8 dB Image Carrier Frequency: LSB = 5 MHz - 4.32 MHz USB = 5 MHz + 4.32 MHz Voice carrier frequency: can not be detected by the frequency spectrum analyzer because it's frequency very small
	Ref = 102dBμ BW = 100 KHz CF = 214 MHz CP1ΔF + 4.32 MHz 2 MHz / DIV ΔV + 18.8 dB Image Carrier Frequency LSB = 214 MHz - 4.32 MHz USB = 214 MHz + 4.32 MHz Voice carrier frequency: can not be seen by the spectrum analyzer because it's frequency very small
	Ref = 102dBμ BW = 100 KHz CF = 421 MHz CP1ΔF + 4.32 MHz 2 MHz / DIV ΔV + 18.8 dB Image carrier frequency: LSB = 421 MHz - 4.32 MHz USB = 421 MHz + 4.32 MHz Voice carrier frequency: can not be seen by the spectrum analyzer because it's frequency very small
	Ref = 102dBμ BW = 100 KHz CF = 624 MHz CP1ΔF + 4.32 MHz 2 MHz / DIV ΔV + 18.8 dB Image Carrier Frequency: LSB = 624 MHz - 4,32 MHz USB= 624 MHz + 4,32 MHz Voice carrier frequency: can not be seen by the spectrum analyzer because it's frequency very small
	Ref = 102dBμ BW = 100 KHz CF = 831 MHz CP1ΔF + 4.32 MHz 2 MHz / DIV ΔV + 18.8 dB Image Carrier Frequency: LSB = 831 MHz - 4.32 MHz USB = 831 MHz + 4.32 MHz Voice carrier frequency: can not be seen by the spectrum analyzer because it's frequency very small
	Ref = 102dBμ BW = 100 KHz CF = 1055 MHz CP1ΔF + 4.32 MHz 2 MHz / DIV ΔV + 18.8 dB Image Carrier Frequency: LSB = 1055 MHz - 4.32 MHz USB = 1055 MHz + 4.32 MHz Voice carrier frequency: can not be seen by the spectrum analyzer because it's frequency very small

DATA ANALYSIS:

From the spectrum image that we get, we can know that the value of:

Carrier frequency: 421 MHz

CP1ΔF + 4.32 MHz

Then:

USB = 421 MHz + 4.32 MHz = 425.32 MHz

LSB = 421 MHz - 4.32 MHz = 416.68 MHz

Voice carrier frequency: can not be seen by the spectrum analyzer because it's frequency very smaller than the frequency carrier.

For the multiples frequencies:

• 1^st multiple : 5 MHz
  
• 2^nd multiple : 214 MHz
  
• 3^rd multiples : 624 MHz
  
• 4^th multiples : 813 MHz
  
• 5^th multiples : 1055 MHz

The sound signal is separate and is transmitted at the upper edge of this signal but in this experiment it cannot be seen clearly. Carrier is shifted to bandpass and increase the one side bandwidth.

Unlike voice signals which have no components near the zero frequency, Video signals are very sensitive to their low frequency content. Distortion in these components degrades the picture. So extra care has to be taken to make sure that all the low frequency components (which are located in the center) are transmitted without distortion.

QUESTION'S ANSWER:

1. Modulation system that being use in the video are AMPLITUDE MODULATION, because the signal amplitude information affect the amplitude of the carrier signal, the signal information into the cover of the carrier signal.
   

Image Modulated Signal

A common use of signal Am is: AM radio broadcasting is widely used for broadcast AM radio wave signal, the TV image (Video), Radio communication: aircraft, amateur radio (SSB), CB radio (Citizens Band Radio). Digital data transmission: Modems Computers (combined with QAM modulation)

1. This type of modulation is amplitude modulation and it can be seen from the changes in amplitude and has a spectrum of AM.
   

Based on the equation of the spectrum signal AM modulated, AM will have 3 (three frequencies):

• fc: carrier frequency signal
  
• LSB: Lower Side Band frequency (LSB), namely the difference between frequency carrier signal and the signal information.
  
• USB: Upper Side Band frequency (USB) is the addition of carrier signal frequency and signal information.
  

CONCLUSION

1. Video modulator is using amplitude modulation (AM)
   
2. AM modulation that shown on a spectrum analyzer displays are three frequencies namely
   

• Carrier frequency (fc)
  
• Lower Side Band Frequency (LSB)
  
• Upper Side Band Frequency (USB)
  

1. The difference between USB and LSB frequencies are = 4.32 MHz
   
2. Using 100 KHz bandwidth
   

Reference

http://en.wikipedia.org/wiki/Amplitude_modulation

http://elkakom.telkompoltek.net/

http://vodpod.com/watch/1793578-lecture-8-amplitude-modulation

http://www.complextoreal.com/base.htm