http://iet.metastore.ingenta.com
1887

Demodulation

Demodulation

For access to this article, please select a purchase option:

Buy chapter PDF
£10.00
(plus tax if applicable)
Buy Knowledge Pack
10 chapters for £75.00
(plus taxes if applicable)

IET members benefit from discounts to all IET publications and free access to E&T Magazine. If you are an IET member, log in to your account and the discounts will automatically be applied.

Learn more about IET membership 

Recommend Title Publication to library

You must fill out fields marked with: *

Librarian details
Name:*
Email:*
Your details
Name:*
Email:*
Department:*
Why are you recommending this title?
Select reason:
 
 
 
 
 
Transceiver and System Design for Digital Communications — Recommend this title to your library

Thank you

Your recommendation has been sent to your librarian.

The demodulation process is an important aspect in the design of the transceiver. Proper design of the demodulation section can enhance the sensitivity and performance of data detection. Two types of demodulation can be used to despread and recover the data. The matched filter approach simply delays and correlates each delay segment of the signal to produce the demodulated output. This process includes the use of PPM to encode and decode the actual data. Another demodulation process uses a coherent sliding correlator to despread the data. This process requires alignment of the codes in the receiver, which is generally accomplished by a short acquisition code. Tracking loops, such as the early/late gate, align the code for the dispreading process. Carrier recovery loops, such as the squaring loop, Costas loop, and modified Costas loop, provide a means for the demodulator to strip off the carrier. A symbol synchronizer is required to sample the data at the proper time in the eye pattern in order to minimize the effects of ISI. Finally, receivers designed for intercepting transmissions of other transmitters use various means of detection depending on the type of phase modulation utilized.

Chapter Contents:

  • 5.1 Types of Demodulation
  • 5.2 Pulsed Matched Filter
  • 5.3 Digital Matched Filter Correlator
  • 5.4 Pulse Position Modulation
  • 5.5 Code Division Encoding and Decoding
  • 5.6 Coherent versus Differential Digital Modulation and Demodulation
  • 5.6.1 Coherent Demodulation
  • 5.7 Carrier Recovery
  • 5.7.1 Squaring Loop
  • 5.7.2 Costas Loop
  • 5.7.3 Modified Costas Loop and AFC Addition
  • 5.8 Despreading Correlator
  • 5.9 Symbol Synchronizer
  • 5.10 The Eye Pattern
  • 5.11 Digital Processor
  • 5.12 Intersymbol Interference
  • 5.13 Scrambler/Descrambler
  • 5.14 Phase-Shift Detection
  • 5.15 Shannon's Limit
  • 5.16 Summary

Inspec keywords: decoding; correlation methods; demodulation; phase modulation; matched filters; encoding; transceivers

Other keywords: ISI; delay segment correlation; carrier recovery loop; signal; code alignment; transceiver design; sliding correlator; symbol synchronizer; demodulation process; data decode; Costas loop; data detection; data recover; data encode; matched filter; acquisition code; phase modulation; receiver; squaring loop; data despread; PPM; tracking loop; dispreading process

Subjects: Filtering methods in signal processing; Modulation and coding methods

Preview this chapter:
Zoom in
Zoomout

Demodulation, Page 1 of 2

| /docserver/preview/fulltext/books/te/sbte008e/SBTE008E_ch5-1.gif /docserver/preview/fulltext/books/te/sbte008e/SBTE008E_ch5-2.gif

Related content

content/books/10.1049/sbte008e_ch5
pub_keyword,iet_inspecKeyword,pub_concept
6
6
Loading
This is a required field
Please enter a valid email address