UNDERSTANDING DIGITAL TV - Ro.Ve.R. Laboratories S.p.A.

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RADIO FREQUENCY MEASUREMENTS RADIO FREQUENCY SPECTRUM Analog, 1 program for each channel You can see video, croma and audio Digital, many programs for each channel You cannot see the single contributions 4
The difference between the two signals is evident in that the digital signal is composed of thousands of carriers, which give the impression of a continuous spectrum. Each of these carriers is modulated in amplitude and phase separately and independently from the others and brings with it a part of the total content of information. The user’s decoder must then interpret and reassemble all the information, translating it into video signals and selecting the program required by the user. The difference that interests an installer is to measure the received “field”, it is a good idea to see if there is a difference between an analog and digital situation to see how things are: ANALOG - You measure the voltage of a single video carrier and express it in units. The most suitable unit, used by almost everyone, is dBµV, ideal value: 60 dBµV level. <strong>DIGITAL</strong> - This measures the power of the complete channel (Average Channel Power), calculating the total power of each carrier (power, not voltage). The unit should be, logically, the milliWatt, or rather dBm (0 dBm = 1 milliwatt), but if you still use dBµV for convenience, ideal value 50 dBµV. 5
Page 1 and 2: UNDERSTANDING DIGITAL TV • Radio
Page 3: SUMMARY 6 Radio frequency spectrum
Page 7 and 8: The function that allows you to fin
Page 9 and 10: The power of the digital signal is
Page 11 and 12: The modulation is the same type for
Page 13 and 14: We know that signals can be “poll
Page 15 and 16: The DVB-T signal has this behavious
Page 17 and 18: Here you can see a schematic block
Page 19 and 20: When it is said that a DVB-T system
Page 21 and 22: Let us assume that the electromagne
Page 23 and 24: We will illustrate a laborious, but
Page 25 and 26: This chart is useful, even if it do
Page 27 and 28: Another situation where the antenna
Page 29 and 30: The back to front antenna ratio is
Page 31 and 32: The reflections caused by a mismatc
Page 33 and 34: Since the system is immune to refle
Page 35 and 36: Operation is based on being able to
Page 37 and 38: Nearly every instrument has an SFN
Page 39 and 40: Here are a number of rules to impro
Page 41 and 42: This picture shows an example of an
Page 43 and 44: As an example, we have superimposed
Page 45 and 46: The diagram clearly shows the trans
Page 47 and 48: To obtain minimum reception stabili
Page 49 and 50: These predictions are verified when
Page 51 and 52: The electromagnetic field is measur
Page 53 and 54: Even if the MER is a good indicator
Page 55 and 56:
The diagram shows once again the th
Page 57 and 58:
This table is calculated for system
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Micro-interruptions are not always
Page 61 and 62:
So ripple (waves) in the spectrum p
Page 63 and 64:
In Figure 3 and 4 you can see the s
Page 65 and 66:
Figure 5 shows DVB-T signal ch.8 th
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Using this case study you can see h
Page 69 and 70:
Directive 2004/108/EC requires that
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The diagram shows the real case of
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MPEG4 REAL TIME SPECTRUM 6-HOUR BA
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mod. HD COMPACT STC THE MOST ADVANC
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UNDERSTANDING DIGITAL TV - Ro.Ve.R. Laboratories S.p.A.

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