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What is x = I + jQ

Started by Unknown March 10, 2005
This is regarding the DSP math/equations in general.  What is "x = I +
jQ"?  I know that j = 0 + 1i and i = sqrt(-1) and i^2 = -1.  But what
is x = I + jQ, where x represents a form of the input data signal.

I need this info to calc the atan(Q/I) for frequency demodulation
purposes.  Any help is appreciated.

george_barr@yahoo.com schrieb:
> This is regarding the DSP math/equations in general. What is "x = I + > jQ"? I know that j = 0 + 1i and i = sqrt(-1) and i^2 = -1. But what > is x = I + jQ, where x represents a form of the input data signal. > > I need this info to calc the atan(Q/I) for frequency demodulation > purposes. Any help is appreciated. >
x is just a complex number. Since I and Q are real, you should have no problems calculating your formula. Thomas
"Dr. Thomas Radtke" <thradtke@freenet.de> wrote in message 
news:422FFB0A.90508@freenet.de...
> george_barr@yahoo.com schrieb: >> This is regarding the DSP math/equations in general. What is "x = I + >> jQ"? I know that j = 0 + 1i and i = sqrt(-1) and i^2 = -1. But what >> is x = I + jQ, where x represents a form of the input data signal. >> >> I need this info to calc the atan(Q/I) for frequency demodulation >> purposes. Any help is appreciated. >> > > x is just a complex number. Since I and Q are real, you should have no > problems calculating your formula. > > Thomas >
What Thomas said. I is used for the In-phase component and Q for Quadrature component. People seem to use phase = atan2(imaginary part , real part) as a convention , if this is what you are using then phase can be interpreted as a clockwise rotation (looking into the paper) with respect to the In-phase direction, when you draw your Q axis at 90 degrees clockwise to the I. Best of Luck - Mike
"Dr. Thomas Radtke" <thradtke@freenet.de> writes:

> george_barr@yahoo.com schrieb: >> This is regarding the DSP math/equations in general. What is "x = I + >> jQ"? I know that j = 0 + 1i and i = sqrt(-1) and i^2 = -1. But what >> is x = I + jQ, where x represents a form of the input data signal. >> I need this info to calc the atan(Q/I) for frequency demodulation >> purposes. Any help is appreciated. >> > > x is just a complex number. Since I and Q are real, you should have no > problems calculating your formula.
Also note that a complex number can be expressed in rectangular form, z = x + i*y or polar form z = r*e^{j*theta}, where r = |z| = sqrt(x^2 + y^2} theta = angle(z) = arctan(y/x), the usual rectangular-to-polar conversion. -- % Randy Yates % "And all that I can do %% Fuquay-Varina, NC % is say I'm sorry, %%% 919-577-9882 % that's the way it goes..." %%%% <yates@ieee.org> % Getting To The Point', *Balance of Power*, ELO http://home.earthlink.net/~yatescr
I guess the missing part is that the math peoples i (imaginary element) 
is called j in electrical engineering to avoid mixup with the current i.


Randy Yates wrote:

> "Dr. Thomas Radtke" <thradtke@freenet.de> writes: > > >>george_barr@yahoo.com schrieb: >> >>>This is regarding the DSP math/equations in general. What is "x = I + >>>jQ"? I know that j = 0 + 1i and i = sqrt(-1) and i^2 = -1. But what >>>is x = I + jQ, where x represents a form of the input data signal. >>>I need this info to calc the atan(Q/I) for frequency demodulation >>>purposes. Any help is appreciated. >>> >> >>x is just a complex number. Since I and Q are real, you should have no >>problems calculating your formula. > > > Also note that a complex number can be expressed in rectangular form, > > z = x + i*y > > or polar form > > z = r*e^{j*theta}, > > where > > r = |z| = sqrt(x^2 + y^2} > theta = angle(z) = arctan(y/x), > > the usual rectangular-to-polar conversion.
-- Please change no_spam to a.lodwig when replying via email!
I is the inphase component and J is the quadratrature component.

I is the inphase component and J is the quadratrature phase component.

Andre wrote:
> I guess the missing part is that the math peoples i (imaginary element) > is called j in electrical engineering to avoid mixup with the current i.
Mix-ups are so very easy! If I didn't know better, I could assume that "current i" above refers to i as it is now, as opposed to what it might become. (Anyone still confused should read "the current i" as "the symbol 'i' that is used to represent electrical current.") Oh my! Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Neo wrote:
> I is the inphase component and J is the quadratrature component.
Ignore that nonsense. (What is K?) Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Neo wrote:
> I is the inphase component and J is the quadratrature phase component.
It doesn't matter that he repeated it. Ignore it anyway. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;