what is phase ,frequency spectrum ,gain ,unity gain?

[m_Hadad]

hi evreyone,
i'm a begginer in DSP and i'm trying to know some terminilogies related to this science.i'm reading a book called DSP for scintists and engineers.i have some background in electronics and i'm a programmer.so please bare with me.
what is phase ,frequency spectrum ,gain ,unity gain?
there is some phrases in this book that i couldn't understand like the following:
when random noise signals combine in an electronic circuit, the resultant noise
is equal to the combined power of the individual signals, not their combined
amplitude.
in chapter 2
i would be gratefull if someone could help me in learning dsp.
regards.

 

[zeeshanzia84]

PHASE: Time shift between two signals of same frequency for e.g.

sine and cosine have a phase difference of 90 degrees. i.e. if you advance the time scale by 90 degrees the sine wave becomes a cosine.

sin (90 + θ) = cos θ



FREQUENCY SPECTRUM : If you know about FOURIER TRANSFORM, you should know that all signals can be broken up into their constituent sinusoidal components. A graph that shows the amplitude of these frequency components is called Frequency Spectrum.


GAIN: The gain of an amplifier is the factor by which it multiplies the input signal and gives you an greater amplitude o/p signal.

Vout = G x Vin

UNIT GAIN: If G=1, it is called unit gain.

 

[m_Hadad]

thanks alot