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

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RADIOFREQUENCY MEASUREMENTS RF POWER MEASUREMENT The mains RF Power/Level units: RF <strong>DIGITAL</strong> POWER RF ANALOG LEVEL 1mW = 0 dBm 1µV = 0 dBµV 0dBm = 108,7 dBµV 1mV = 60 dBµV –58,7 dBm = 50 dBµV 1mV = 0dBmV (USA) AVERAGE POWER IN DVB-T • It is like powering an electric heater with many small power linesDVB-T: • Each line provides part of the energy • The total heat is the total amount of all lines contributions 8
The power of the digital signal is always measured in dBµV, but is different from analog: ANALOG: Is the true voltage measured only for the peak of the video carrier and a certain amount is required (about 1 millivolt, equal to 60 dBµV) to obtain a quality image, practically low level = low quality, high level = high quality pictures. <strong>DIGITAL</strong>: This is a measurement derived from the average power, obviously it is not possible to measure 8000 signal carriers individually. The result is however expressed in dBµV, a well known, familiar unit. PLEASE NOTE: The power of the received field is not so important in DVB-T, it only needs to have a required minimum level that is about 40 dBµV (better 50 dBµV), after which it has no influence on the quality. In fact, it is better to avoid levels that are too high and that could saturate and degrade the set-top box and the quality of the signal received. With numbers, as shown above, you can move very quickly from dBµV to dBm and vice versa: just add, or remove the number 108.7, which is valid for 75 ohm systems. In the case of 50 ohms, the number is 107. In all the meters you can select the unit of measurement you prefer: dBm or dBµV, or dVmV for USA. 9
Page 1 and 2: UNDERSTANDING DIGITAL TV • Radio
Page 3 and 4: SUMMARY 6 Radio frequency spectrum
Page 5 and 6: The difference between the two sign
Page 7: The function that allows you to fin
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
Page 59 and 60:
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
Page 67 and 68:
Using this case study you can see h
Page 69 and 70:
Directive 2004/108/EC requires that
Page 71 and 72:
The diagram shows the real case of
Page 73 and 74:
MPEG4 REAL TIME SPECTRUM 6-HOUR BA
Page 75 and 76:
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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