Your SlideShare is downloading. ×
Tele3113 wk6wed
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×

Introducing the official SlideShare app

Stunning, full-screen experience for iPhone and Android

Text the download link to your phone

Standard text messaging rates apply

Tele3113 wk6wed

173
views

Published on

Published in: Education

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
173
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
8
Comments
0
Likes
0
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. TELE3113 Analogue and Digital Communications Phase-Locked Loop Wei Zhang w.zhang@unsw.edu.auSchool of Electrical Engineering and Telecommunications The University of New South Wales
  • 2. Phase-Locked Loop (1)Block diagram. (Demodulation of FM Signals.) × FM wave s(t) e(t) Loop v(t) filter r(t) Voltage controlled oscillatorVoltage controlled oscillator (VCO) performs FM as r(t) = Av cos[2πfc t + φ2 (t)],where Av is the amplitude and the angle t φ2 (t) = 2πkv v(τ )dτ. 0 TELE3113 - Phase-Locked Loop. August 26, 2009. – p.1/
  • 3. Phase-Locked Loop (2)Suppose the incoming FM wave is s(t) = Ac sin[2πfc t + φ1 (t)]and the angle t φ1 (t) = 2πkf m(τ )dτ. (1) 0After the multiplication of s(t) by r(t), the low-frequencycomponent is e(t) = km Ac Av sin[φe (t)],where km is the multiplier gain and φe (t) = φ1 (t) − φ2 (t). TELE3113 - Phase-Locked Loop. August 26, 2009. – p.2/
  • 4. Phase-Locked Loop (3) When the phase error φe (t) = 0, the PLL is in phase-lock. When the phase error is small compared to 1, sin[φe (t)] ≈ φe (t), the PLL is near-phase-lock.Therefore, if φe is small compared to one, K0 e(t) = km Ac Av φe (t) = φe (t), kvwhere K0 = km kv Ac Av is called the loop-gain parameter of thePLL. TELE3113 - Phase-Locked Loop. August 26, 2009. – p.3/
  • 5. Phase-Locked Loop (4)Linearized model of the PLL. K 0 / kv φ1 (t ) φe (t ) × e(t) v(t) ∑ + h(t) __ φ2 (t ) × ∫0 t dτ 2πkv TELE3113 - Phase-Locked Loop. August 26, 2009. – p.4/
  • 6. Closed-loop GainConsider a negative feedback amplifier, as follows. µ × I(t) O(t) ∑ + __ Network gain βThe closed-loop gain of the amplifier is O(t) µ G = . I(t) 1 + µβ 1If µβ is large compared to one, G ≈ β . TELE3113 - Phase-Locked Loop. August 26, 2009. – p.5/
  • 7. Phase-Locked Loop (5)If K0 is large compared to 1, then the closed-loop gain of thePLL is v(t) 1 ≈ , φ1 (t) βwhere β denotes the gain of the network generating FM waves.Therefore, 1 dφ1 (t) v(t) ≈ . 2πkv dtUsing (1), we continue to obtain kf v(t) ≈ m(t). kvNow the message signal m(t)is recovered from s(t). TELE3113 - Phase-Locked Loop. August 26, 2009. – p.6/