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Carrier offset estimator

a carrier offset and estimator technology, applied in the field of digital communication systems using quadrature modulation techniques, can solve problems such as the quality of downstream signal processing

Inactive Publication Date: 2007-11-22
INTERDIGITAL TECH CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This approach allows for precise estimation and correction of carrier frequency offsets, enhancing signal quality by addressing frequency alignment issues before data processing, thereby improving communication system performance.

Problems solved by technology

However, signal perturbations occurring during transmission as well as frequency alignment errors between the local oscillators of the transmitter and receiver manifest a difference between the carrier and local oscillator frequencies which is known as carrier offset.
Without correcting offset first, the quality of downstream signal processing suffers.

Method used

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Examples

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Embodiment Construction

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[0030] When referred to hereafter, the terminology “wireless transmit / receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment.

[0031] The embodiments will be described with reference to the drawing figures where like numerals represent like elements throughout.

[0032] Shown in FIG. 4 is an analog or digital blind carrier detector 33 of the present invention. A quadrature modulated signal r(t) is received from a communication channel (not shown) and is input 19 to a receiver 17. One skilled in this art recognizes that additional co...

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Abstract

A system for estimating carrier offset includes includes a transmitter configured to transmit a quadrature modulated signal, and a receiver. The receiver includes an input configured to receive the quadrature modulated signal, a local oscillator configured to generate cosine and sine waves at a carrier frequency of the quadrature modulated signal, at least one cosine mixer configured to generate a carrier frequency demodulated output, at least one sine mixer configured to generate a carrier frequency demodulated output, a plurality of lowpass filters configured to filter the demodulated output of the cosine and sine mixers to produce filtered cosine and sine signal components, and a carrier offset detection processor to estimate a carrier offset between the carrier frequency and a local oscillator frequency based on the filtered output of the lowpass filters.

Description

CROSS REFERENCE TO RELATED APPLICATION(S) [0001] This application is a continuation of application Ser. No. 10 / 258,626, filed on Mar. 25, 2003; which claims priority from PCT Application No. PCT / US00 / 11125, filed on Apr. 25, 2000, all of which are incorporated herein by reference.BACKGROUND [0002] 1. Field of Invention [0003] The present invention relates generally to digital communication systems using quadrature modulation techniques. More specifically, the invention relates to a system and method for blind detection of carrier frequency offsets in such systems. [0004] 2. Description of the Prior Art [0005] A digital communication system typically transmits information or data using a continuous frequency carrier with modulation techniques that vary its amplitude, frequency or phase. After modulation, the signal is transmitted over a communication medium. The communication media may be guided or unguided, comprising copper, optical fiber or air and is commonly referred to as the c...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H04L5/12H04L27/227H04L27/233H04L27/38
CPCH04L27/2332H04L27/3836H04L2027/0085H04L2027/0065H04L27/3854
Inventor KAZAKEVICH, LEONIDOZLUTURK, FATIHREZNIK, ALEXANDER
Owner INTERDIGITAL TECH CORP