lecture6

lecture6 - EEE455/591 EEE455/591 Fre ncy and...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
EEE455/591 Frequency and Phase Modulation FM and PM Reading: Textbook Sections 3.3, skip 3.3.2 Topics: 1. 1. What is FM and PM? Why? What Applications? 2. 2. Mathematical Description of PM and FM 3. 3. Spectrum Usage of FM and PM 4. 4. Practical Implementations of FM
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1. FM and PM: What and Why? Angle Modulation: Transmit the message in: - the frequency f c of the carrier (FM), or - the phase θ c of the carrier (PM) - but not the A c amplitude of the carrier (AM)! Use extensively in: - FM radio (e.g. KNIX 102.5MHz) - Audio part of TV broadcasting - First generation analog cellular phones (Narrowband FM) Result: Constant envelope modulated signal: ) 2 cos( ) ( c c c t f A t u θ π + =
Background image of page 2
1. FM and PM: Why? Advantages: Improved noise immunity Power efficient when amplifiers operates in saturation Immune to distortion in amplitude. Disadvantages: Takes more bandwidth than AM More complex transceivers. Frequency Modulation: The message modulates the frequency of the carrier: Phase Modulation: The message modulates the phase of the carrier. ) 2 cos( ) ( c c c t f A t u θ π + =
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2. Representation of PM and FM in Time Phase Modulation (PM) Frequency Modulation (FM) )) ( 2 cos( ) ( t m k t f A t u p c c + = π ) ) ( 2 cos( ) ( τ d m k t f A t u t f c c - + =
Background image of page 4
2. “Instantaneous” Frequency of PM and FM Definition of instantaneous frequency: PM: Maximum phase deviation FM: Maximum frequency deviation Modulation Index PM: FM: For message bandwidth W )) ( 2 cos( )) ( cos( ) ( t t f A t A t u c c c φ π θ + = = ) ( ' 2 1 ) ( 2 1 ) ( t f dt t d t f c i + = = | ) ( | max max t m k p = ∆φ | ) ( | max max t m k f f = max | ) ( | max β = = t m k p p W f W t m k f f max | ) ( | max = =
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2. Relationship Between AM and FM FM: PM: )) ( 2 cos( ) ( t m k t f A t u p c c + = π ) ) ( 2 cos( ) ( τ d m k t f A t u t f c c - + =
Background image of page 6
2. Equivalence of PM and FM
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/01/2009 for the course EEE 455 taught by Professor Hui during the Spring '09 term at ASU.

Page1 / 19

lecture6 - EEE455/591 EEE455/591 Fre ncy and...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online