slide1
Download
Skip this Video
Download Presentation
Phase/Frequency Modulators

Loading in 2 Seconds...

play fullscreen
1 / 6

Phase/Frequency Modulators - PowerPoint PPT Presentation


  • 53 Views
  • Uploaded on

Phase/Frequency Modulators. Frequency Modulation using a Voltage Controlled Oscillator (VCO). v o (t) = V c cos{2 p [f c +k 0 v m (t)]t} k 0 v m (t) = D f(t). f out. f c , k o (Hz/v) VCO. v m (t). “Modulation Sensitivity”.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Phase/Frequency Modulators' - lionel-madden


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Phase/Frequency Modulators

Frequency Modulation using a Voltage Controlled Oscillator (VCO)

vo(t) = Vccos{2p[fc +k0vm(t)]t}

k0vm(t) = Df(t)

fout

fc ,

ko(Hz/v)

VCO

vm(t)

“Modulation Sensitivity”

This is the only parameter we are interested in! Not the frequency, not the voltage, but the Frequency Deviation. This is the parameter that represents the source information signal; and this is what we recover during demodulation.

fout

fc

ko

“Free Running Frequency” frequency of operation when input voltage is zero.

Df(t)

fout(t)

vm(t)

k0

vm

+

fc

slide2

Phase/Frequency Modulators

Reference Phase

Phase Modulation using a Voltage Controlled Phase Shift

fc

vo(t) = Vccos{2pfct+kpvm(t)}

kpvm(t) = F(t)

vm(t)

kp(rad/v)

“Modulation Sensitivity”

Phase Deviation

F

This is the only parameter we are interested in! Not the frequency, not the voltage, but the Phase Deviation. This is the parameter that represents the source information signal; and this is what we recover during demodulation.

vm

determining modulation sensitivity for a phase modulator
Determining Modulation Sensitivity for a Phase Modulator

Reference Phase

V(t)=I0ZT(t)) = V ejq(t) = V ej(wt+F(t))

i(t)=I0cos(wct)

Phase Deviation

chain rule
Chain Rule

v0 is the DC bias level which gives zero phase shift.

When v0 is applied to the diode:

C(v0) = C0(1+2v0)-1/2 = Cc

w(v0)= wc

S(v0) = 0

slide6

Limit of Linearity: How good is good enough?

DF

s

se

Phase Error

DFe

se

s

For a maximum fractional error (distortion) of e, the maximum normalized frequency displacement is:

1

If e < 0.05, DFMAX < 0.39R

ad