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

More documents

Recommendations

Info

SFN (Single Frequency Network) RECEPTION EXAMPLE BETWEEN TWO TX SITES 300µS 250µS 200µS 150µS 100µS 42 Along the lines signals are received from two TX sites with the same delay 50µS
As an example, we have superimposed a network of curves, with a constant level, onto a geographical map of the Padana Valley in North-West Italy. Here there is an SFN network, designed and built by the Italian broadcasting company Rai Way, which implements a few sites with high power transmitters that cover a very wide area. You can see that the distance between the TX sites of Mount Penice and Mount Eremo is so far that the delay exceeds the guard interval. To the east of Mount Penice there is Mount <strong>Ve</strong>nda, another high power TX site, and this is also in SFN with TX sites covering the regions of Friuli and Emilia <strong>Ro</strong>magna, North East of Italy. In cases like these it is very difficult to make the delays fall within the guard interval by inserting artificial delays at the various sites, because what you gain in one direction, you lose in the other. However natural obstacles can help to prevent propagation beyond a certain distance (see the hills to the east of Turin) as well as the careful design of antenna diagrams and the calibration of power in transmission. The directivity of the receiving antennas is of fundamental importance. International planning bodies, who dictate broadcasting regulations, have established that a basic antenna should have an attenuation of 10 dB for signals from an angle exceeding 25 degrees and about 15 dB for cross-polarization. 43
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 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: This picture shows an example of an
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

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

Create successful ePaper yourself

Delete template?

Save as template?