How to convert dB into Magnitude and Angle (2024)

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  • EDA Theory
  • Elementary Electronic Questions
  • Thread starternarayani
  • Start dateSep 20, 2015
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  • Sep 20, 2015
  • #1

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narayani

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Dear Sir,

I want to convert 18.65 dB into its Magnitude and Angle (Phase). Can you give formula to converting dB into its equivalent magnitude and angle (Phase).

  • Sep 20, 2015
  • #2

pancho_hideboo

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You can never get phase infomation from dB.
You can only get magnitude infomation.

Mag = 10^(dB/20)

  • Sep 20, 2015
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KlausST

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Hi,

dB is a value of ratio.

For values like voltage, current the above formula is correct.

For value like power "Mag = 10^(dB/10)" is correct.

Klaus

  • Sep 20, 2015
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then how to convert dB into Magnitude and phase. How to get phase values for dB.

  • Sep 20, 2015
  • #5

pancho_hideboo

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I have following definition in Verilog-A code.

`define db20_real(x) (pow(10, (x)/20))
`define db10_real(x) (pow(10, (x)/10))

narayani said:

then how to convert dB into Magnitude and phase. How to get phase values for dB.

Again, You can never get phase infomation from dB.

  • Sep 20, 2015
  • #6

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Do you read the replies? dBs are like percentages %, a ratio of two numbers. Nothing about phase angles at all!!
Frank

  • Sep 20, 2015
  • #7

pancho_hideboo

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The followings are MATLAB code for dbv()=db20() and dbp()=db10().

Code:

function y=dbv(x)% dbv(x) = 20*log10(abs(x)); the dB equivalent of the voltage xy = -Inf*ones(size(x));if isempty(x) returnendnonzero = x~=0;y(nonzero) = 20*log10(abs(x(nonzero)));

Code:

function y=dbp(x)% dbp(x) = 10*log10(x): the dB equivalent of the power xy = -Inf*ones(size(x));if isempty(x) returnendnonzero = x~=0;y(nonzero) = 10*log10(abs(x(nonzero)));

Again, You can never get phase infomation from dB value, even if you use MATLAB or ANY.

https://edadocs.software.keysight.com/display/ads2009/db()+Measurement
https://en.wikipedia.org/wiki/Decibel

Last edited:

  • Sep 21, 2015
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KlausST said:

Hi,
dB is a value of ratio.
For values like voltage, current the above formula is correct.
For value like power "Mag = 10^(dB/10)" is correct.

Not quite. The Bel is always a

power

ratio, by definition. A deciBel is 1/10 of a Bel, hence the "10" in the well-known formulae.

Since power is proportional to the square of the voltage, expressing voltage ratios in dB introduces an extra "2", hence the "20".

  • Sep 21, 2015
  • #9

KlausST

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Hi,


The Bel is always a power ratio, by definition. A deciBel is 1/10 of a Bel, hence the "10" in the well-known formulae.

Since power is proportional to the square of the voltage, expressing voltage ratios in dB introduces an extra "2", hence the "20".

Isn´t that what i wrote? At least i wanted to..

Klaus

  • Sep 21, 2015
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KlausST said:

Hi,

Isn´t that what i wrote? At least i wanted to..

Klaus

The end result is the same, but your explanation implied there was a difference for power and voltage, whereas there is no difference.

Sorry that it is so difficult to follow what we are discussing; by design this website strips out the context, hence the large amount of vertical whitespace between "Hi" and "Isn't".

  • Sep 21, 2015
  • #11

KlausST

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Hi,

The end result is the same, but your explanation implied there was a difference for power and voltage, whereas there is no difference.

Yes, there is a difference. And you explained it correctely already.

1) for voltage: dB(U) = 20 * log(U_out / U_in)

2) for power: dB(P) = 10 * log(P_out / P_in)

the mathematical calculation is like you explained:

Klaus

  • Sep 21, 2015
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pancho_hideboo

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Consider original point of this thread.

Decibel definition should be db20() not db10() for this thread point.

For example, consider S-parameter of Touchstone format
There are following three styles for complex value.
(1) dB/Angle
(2) Mag/Angle
(3) Real/Imag
Here Mag=10^(dB/20)

https://edadocs.software.keysight.com/display/ads2009/db()+Measurement
https://www.edaboard.com/threads/344348/

Last edited:

  • Sep 21, 2015
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KlausST

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Hi,

Consider original point of this thread.

Decibel definition should be db20() not db10() for this thread point.

I read the original post and can´t find this.

Is "magnitude" always considered to be voltage or current? Can´t it be power?

Klaus

  • Sep 21, 2015
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pancho_hideboo

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Last edited:

  • Sep 21, 2015
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KlausST

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Hi,

The OP says nothing about S parameters nor Agilent (Keysight) ADS.

Klaus

  • Sep 21, 2015
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pancho_hideboo

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KlausST said:

The OP says nothing about S parameters nor Agilent (Keysight) ADS.

Phase(Angle) is refered in this thread, so it is voltage not power.

Again, Decibel definition should be db20() not db10() for this thread point.

Last edited:

  • Sep 21, 2015
  • #17

KlausST

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Hi,

Yes, here it is. The OP knows how to hide informations...

Klaus

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How to convert dB into Magnitude and Angle (2024)

FAQs

How do you convert dB to magnitude? ›

Description. y = db2mag( ydb ) returns the magnitude measurements, y , that correspond to the decibel (dB) values specified in ydb . The relationship between magnitude and decibels is ydb = 20 log10( y ).

Know More ›
What is the formula for converting decibels? ›

The formula is dB = 10 × log(P1/P2). Also, since power is proportional to V^2, then dB = 20 ×log(V1/V2).

Explore More ›
How to convert dB into normal value? ›

How to Calculate Normal Value from dB?
  1. First, determine the dB value you want to convert.
  2. Next, determine the reference value (RV). ...
  3. Use the formula NV = RV * 10^(dB / 10) to calculate the normal value (NV).
  4. Finally, enter the dB value and the reference value into the calculator to get the normal value.
6 days ago

See More ›
How to convert a value in dB? ›

The dB is calculated via two different expressions XdB=10log10(XlinXref)orYdB=20log10(YlinYref). If you convert a quantity X that relates to power or energy, the factor is 10. If you convert a quantity Y that relates to amplitude, the factor is 20.

Read On ›
What is the magnitude unit of dB? ›

decibel (dB), unit for expressing the ratio between two physical quantities, usually amounts of acoustic or electric power, or for measuring the relative loudness of sounds. One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio.

Continue Reading ›
How to convert dB into intensity? ›

For every 10 dB increase in intensity level, the sound intensity will increase by a factor of 10. The intensity level is given by β = 10 log ⁡ ( I I 0 ) dB, where I 0 = 10 − 12 W / m 2 represents the threshold for human hearing and is the intensity of the sound in W / m 2 .

Discover More Details ›
How can I calculate dB? ›

dB = 10 log(0.1/1) = -10 dB. The term decibel does not in itself indicate power, but rather is a ratio or comparison between two power values. It is often desirable to express power levels in decibels by using a fixed power as a reference.

Read On ›
What is 1 dB equal to? ›

The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B).

See Details ›
What is an example of a dB calculation? ›

Finding dB Gain

Assume an input power of 1 milliwatt (0.001 watt) and an output power of 50 watts. Find the ratio: 50 ÷ 0.001 = 50,000. Then, take the log of 50,000 = 4.699. Finally, multiply by 10 = 46.99 dB power gain.

Learn More ›
What is 20 dB equal to? ›

Decibels Explained
Decibel LevelSource
10 dBNormal breathing
20 dBRustling leaves, mosquito
30 dBWhisper
40 dBStream, refrigerator humming
7 more rows

Show Me More ›

How to convert dB into linear scale? ›

  1. The usual formula for calculating linear-to-dB is: dB = 20log(V1/V2)
  2. dB is an expression of a ratio (V1/V2) and in the case of dBFS the ratio is with reference to a Full Scale = +/- 1. So V2 = 1. Which gives: dB = 20.log V. ...
  3. Calculating the other way: linear-value = antilog (db-value/20) V=10^(dB/20)
Feb 17, 2010

Read More ›
What is 10 dB equal to? ›

Decibels increase exponentially

For example, every increase of 10 dB on the decibel scale is equal to a 10-fold increase in sound pressure level (SPL). Near silence is expressed as 0 dB but a sound measured at 10 dB is actually 10 times louder. If a sound is 20 dB, that's 100 times louder than near silence.

Show Me More ›
How do you convert decibels to intensity? ›

For every 10 dB increase in intensity level, the sound intensity will increase by a factor of 10. The intensity level is given by β = 10 log ⁡ ( I I 0 ) dB, where I 0 = 10 − 12 W / m 2 represents the threshold for human hearing and is the intensity of the sound in W / m 2 .

Learn More Now ›
How many decibels is an order of magnitude? ›

Every 10 dB represents a change of one order of magnitude in intensity. 120 dB, 12 orders of magnitude higher than our reference level, has an intensity of 1 W/m2. Any more intense than this and sounds start getting uncomfortable.

Keep Reading ›
What is the magnitude of the decibel scale? ›

It is based on orders of magnitude, rather than a standard linear scale, so each mark on the decibel scale is the previous mark multiplied by a value. On the decibel scale, the quietest audible sound (perceived near total silence) is 0 dB. A sound 10 times more powerful is 10 dB.

Get More Info ›

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