chap4_lec3 - Eeng 360 1 Chapter 4 Bandpass Circuits...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon

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

View Full DocumentRight Arrow Icon

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

View Full DocumentRight Arrow Icon

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

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

Unformatted text preview: Eeng 360 1 Chapter 4 Bandpass Circuits Limiters Mixers, Upconverters and Downconverters Detectors, Envelope Detector, Product Detector Phase Locked Loops (PLL) Huseyin Bilgekul Eeng360 Communication Systems I Department of Electrical and Electronic Engineering Eastern Mediterranean University Eeng 360 2 Limiters Limiter is a nonlinear circuit with an output saturation characteristic. It rejects envelope variations but preserves the phase variations. ( ) ( )cos( ( )) ( ) cos( ( )) in c out L c v t R t t t v t KV t t = + = + Ideal limiter characteristic with illustrative input and unfiltered output waveforms. Eeng 360 3 Mixers Ideal mixer is a mathematical multiplier of two input signals. One of the signals is sinusoidal generated by a local oscillator. Mixing results in frequency translation. SSB mixer ( 29 ( 29 { } Bandpass Input Signal Re c j t in in v t g t e = Eeng 360 4 Mixers ( 29 ( 29 { } ( 29 ( 29 { } ( 29 1 Bandpass Input Signal Mixer Output Re Re cos 4 c c c j t in in j t in j t in in v t g t e v t A g t e t A g t e g = = = + ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 {} {} {} ( 29 ( 29 ( 29 { } ( 29 ( 29 { } * * * 1 * 4 1 1 R 2 2 e 2 2 Re Re c c c c c c c c c j t j t j t j t j t j t j t in in in in j t j t i u n in c t e e e A g t e g t e g t e g t e A A v t g t e g t f f e -- +- +--- +- = + = + + + + + = = UPCONVERSION DOWNC BANDPASS FILTER BASEBAND O ONVER R BAN DPASS FILTE SI N R O d c f f f f + = - Eeng 360 5 Choosing LO Frequency of Mixers ( 29 ( 29 ( 29 { } ( 29 ( 29 { } t j in t j c c e t g A e t g t v Re 2 Re 2 2 -- = = ( 29 ( 29 ( 29 { } ( 29 ( 29 { } t j in t j in c c e t g A e t g A t v - + + = * 1 Re 2 Re 2 ( 29 ( 29 ( 29 ( 29 ( 29 * * * *- Upper & lower sidebands are exchanged * Phase spectrum is inverted j t j t in in in in F g t g t e dt g t e dt f f G ----- = = =- If ( f c- f ) = 0 Low Pass Filter gives baseband spectrum If ( f c- f )> 0 Bandpass filter Modulation is preserved Filter Output: If f c > f 0 modulation on the mixer input is preserved If f c < f needs to be positive Complex envelope is conjugated...
View Full Document

This note was uploaded on 05/24/2011 for the course EE 324 taught by Professor Emreaktaş during the Spring '11 term at Hacettepe Üniversitesi.

Page1 / 25

chap4_lec3 - Eeng 360 1 Chapter 4 Bandpass Circuits...

This preview shows document pages 1 - 6. Sign up to view the full document.

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