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DC Estimation and Tracking for M-DPSK Channels

IP.com Disclosure Number: IPCOM000008087D
Original Publication Date: 2002-May-16
Included in the Prior Art Database: 2002-May-16
Document File: 4 page(s) / 96K

Publishing Venue

Motorola

Related People

Weizhong Chen: INVENTOR

Abstract

While direct conversion receivers or 0-IF receivers offer a low power/cost advantage to portable wireless devices, they incur a unique problem: a DC component in the received I&Q baseband signal. This DC component increases the dynamic range of the received signal, thus increasing the power consumption of the receiver. The conventional solution to the DC problem is to use a highpass analog filter to attenuate the DC in order to reduce the received signal dynamic rage. However, this highpass filter has a long acquisition time or a long response time. For burst communication, the received baseband signal thus has residual DC. This residual DC component in baseband also reduces the performance for message recovery. In addition, the highpass filter also causes a false attenuation problem since the highpass filter also attenuates the desired signal DC component. To solve the false attenuation problem, most communication systems are designed to allow data scrambling on retransmission. However, this retransmission coupled with data scrambling reduces the system throughput. Thus there is a need to estimate and compensate for the residual DC in the received baseband signal.

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DC Estimation and Tracking for M-DPSK Channels

 Weizhong Chen

The Problem

While direct conversion receivers or 0-IF receivers offer a low power/cost advantage to portable wireless devices, they incur a unique problem: a DC component in the received I&Q baseband signal. This DC component increases the dynamic range of the received signal, thus increasing the power consumption of the receiver. The conventional solution to the DC problem is to use a highpass analog filter to attenuate the DC in order to reduce the received signal dynamic rage. However, this highpass filter has a long acquisition time or a long response time. For burst communication, the received baseband signal thus has residual DC. This residual DC component in baseband also reduces the performance for message recovery. In addition, the highpass filter also causes a false attenuation problem since the highpass filter also attenuates the desired signal DC component. To solve the false attenuation problem, most communication systems are designed to allow data scrambling on retransmission. However, this retransmission coupled with data scrambling reduces the system throughput. Thus there is a need to estimate and compensate for the residual DC in the received baseband signal.

In addition, co-channel and adjacent channel interference can also cause DC error, which is time varying. Thus there is also a need for DC error tracking and compensation for the time varying DC error.

The Solution

For M-DPSK channel, the received baseband signal can be represented as

where x(k) is the signal value at the symbol center of kth symbol, A is an unknown complex amplitude, dc is the complex DC error to be estimated, and n(k) is the Additive White Gaussia...