Slide Series 2

1

Συστήµατα Κινητών ΕπικοινωνιώνΕργαστήριο Κινητών Ραδιοεπικοινωνιών, ΣΗΜΜΥ ΕΜΠ

Χρήση των dBs & Nepers στιςΤηλεπικοινωνίες

ITU-R V.574-4 USE OF THE DECIBEL AND THE NEPER IN TELECOMMUNICATIONS

Αθ. ∆. Παναγόπουλος, Λέκτορας ΕΜΠ

Χρήση των dBs & Nepers στιςΤηλεπικοινωνίες

ITU-R V.574-4 USE OF THE DECIBEL AND THE NEPER IN TELECOMMUNICATIONS

Αθ. ∆. Παναγόπουλος, Λέκτορας ΕΜΠ

2


210

1

210

1

10log

20log

PdB

P

VdB

V

=

=

Ορισµοί dBΟρισµοί dB

10

010

10log

( )10 log

( )

t

r

a

PL

P

P reference antennaG

P given antenna

=

=

Απώλεια Μετάδοσης

Κέρδος ΚεραίαςΤάσεις

Ισχύεις

3


10

10

10log1

10log1

dBW

dBm

PdBW P

W

PdBm P

mW

= =

= =

Ορισµοί dBW, dBmΟρισµοί dBW, dBm

1010log 1000 30dBm dBW dBWP P P= + = +

4


( )

( )

10

10

10

( )10 log

1

10log

10log

dBmV

Hz dBHz

K dBK

V mVdBmV V

mV

dBHz f f

dBK T T

= =

= =

= =

Ορισµοί dBmV, dBHz, dBKΟρισµοί dBmV, dBHz, dBK

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( ) ( )2 210

2 2

2 2

10log

1 0.10 / 10 /

S dBW m S W m

W mWdBW m dBmW cm

m cm

=

= = = −

Ορισµοί dBW/m2, dBV/mΟρισµοί dBW/m2, dBV/m

Μονάδα µέτρησης της πυκνότητας ισχύος :

Μονάδα µέτρησης ηλεκτρικού πεδίου :

( ) ( )1020log

0 120 120

E dBV m E V m

dBV m dB V m dBuµ

=

= =

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Χαρακτηριστικές ΤιµέςΧαρακτηριστικές Τιµές

Απώλειες Ισχύος

-1dB 0.8

-2dB 0.63

-3dB 0.5

-4dB 0.4

-5dB 0.32

-6dB 0.25

-7dB 0.2

-8dB 0.16

-9dB 0.125

-10dB 0.1

Κέρδος Ισχύος

1dB 1.25

2dB 1.6

3dB 2

4dB 2.5

5dB 3.2

6dB 4

7dB 5

8dB 6.3

9dB 8

10dB 10

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dBW: absolute power level with respect to 1 Watt, expressed in decibels;

1W=0dBW=30dBm

dBm: absolute power level with respect to 1 milli Watt, expressed in decibels;

1mW=0dBm=-30dBW

dBm0: absolute power level with respect to 1 milli Watt, expressed in decibels,

referred to a point of zero relative level;

dBm0p: absolute psophometric power level (weighted for telephony) with respect

to 1 milli Watt, expressed in decibels, referred to a point of zero relative level;

dBm0s: absolute power level with respect to 1 milli Watt, expressed in decibels,

referred to a point of zero relative level in sound programme transmission;

dBm0ps: absolute psophometric power level (weighted for sound-programme

transmission) with respect to 1 milli Watt, expressed in decibels, referred

to a point of zero relative level in sound programme transmission.

Απόλυτα Επίπεδα ΙσχύοςΑπόλυτα Επίπεδα Ισχύος

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dBµ or dBu: absolute level of the electromagnetic field with respect to 1 mV/m,

expressed in decibels

Απόλυτα Επίπεδα Η/Μ πεδίωνΑπόλυτα Επίπεδα Η/Μ πεδίων

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dBu: absolute voltage level with respect to 0.775 V;

dBu0: absolute voltage level with respect to 0.775 V, referred to a point

of zero relative level;

dBu0s: absolute voltage level with respect to 0.775 V, referred to a point

of zero relative level in sound-programme transmission;

dBq: absolute noise voltage level with respect to 0.775 V;

dBqps: absolute weighted voltage level in sound-programme

transmission;

dBq0ps: absolute weighted voltage level with respect to 0.775 V referred

to a point of zero relative level in sound-programme transmission;

dBq0s: absolute unweighted voltage level in sound-programme

transmission with respect to 0.775 V referred to a point of zero

relative level.

Απόλυτα επίπεδα τάσης για audio σήµαταΑπόλυτα επίπεδα τάσης για audio σήµατα

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dBi: in relation to an isotropic antenna;

dBd: in relation to a half-wave λ/2 dipole.

dBd = dBi - 2.15

dBi = dBd + 2.15

Κέρδη κεραιώνΚέρδη κεραιών

Slide Series 2

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Transcript of Slide Series 2