The Method of DC Elimination in Digital Baseband Receiver of OFDM System

Abstract

The invention relates to a method of an OFDM system digital base-band receiver for carrying out direct-current elimination. The method comprises the steps that: signals received by the OFDM system digital base-band receiver are divided into two parallel paths, filtering is carried out through two high-pass IIR filters with different transition bandwidths, for one path, filtering is carried out on short training sequences, and for the other path, filtering is carried out on long training sequences, SIG fields and data fields, so that signal fields whose direct-current components are eliminated are respectively obtained for different receiving processing. The method adopts the idea that OFDM fields with different effective frequency points around a zero frequency are filtered by the high-pass filters with different transition bandwidths, two parallel paths of high-pass filter structures are designed for respectively carrying out direct-current elimination on the received signals, so that the different transition band requirements of the filters are met, and the time delay requirement is also met; in addition, the method can be applied to the design of a 802.11n system digital base-band and can also used for other similar OFDM systems with different training sequences, so that the application range is wide.

Description

technical field [0001] The invention relates to a method for eliminating direct current by a digital baseband receiver of an OFDM system, and is especially suitable for a method for eliminating direct current at a receiving end of a digital baseband of an OFDM system with a frame structure similar to 802.11n. Background technique [0002] The DC offset usually comes from the self-mixing and nonlinear characteristics in the analog front-end. When the DC offset is large, the DC offset will cause all subsequent circuits to saturate. Usually, the DC component is eliminated in the analog front-end, but the residual DC component still interferes a lot with the baseband signal after passing through the subsequent amplification module, resulting in a decrease in receiver performance. In the 802.11n OFDM system, although zero frequency is not an effective signal frequency point, the DC component has no direct impact on signal demodulation, but the DC component will affect signal dete...

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Problems solved by technology

[0002] The DC offset usually comes from the self-mixing and nonlinear characteristics in the analog front-end. When the DC offset is large, the DC offset will cause all subsequent circuits to saturate

Usually, the DC component is eliminated in the analog front end, but the residual DC component still interferes a lot with the baseband signal after passing through the subsequent amplification module, resulting in a decrease in receiver performance

In the 802.11n OFDM system, although zero frequency is not an effective signal frequency point, the DC component has no direct impact on signal demodulation, but the DC component will affect signal detection, AGC adjustment, frequency offset estimation, symbol synchronization and channel estimation, etc. The accuracy of the module indirectly affects the receiver demodulation sensitivity

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