Rx DC Component Estimation in Zero-IF Receivers
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Solution Overview
Problem
In wireless local area network (WLAN) systems, zero intermediate frequency receivers generate a receive end-direct current (Rx DC) component that interferes with signal performance, especially when frequency offsets are large, making it challenging to obtain an accurate estimated value of the Rx DC component for compensation.
Innovation Solution
A signal processing method that involves sampling a signal in two time periods to obtain first and second sampling points, and then calculating an estimated value of the Rx DC component based on these sampling points and a normalized frequency offset, allowing for compensation of the Rx DC component even in data frames with only one DC subcarrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DC subcarriers outside the bandwidth center are used to obtain the estimated value of the Rx DC component, then the estimation accuracy is improved for data frames with multiple DC subcarriers, but the method cannot be applied to data frames with only one DC subcarrier located at the bandwidth center
Solution Approach 1:
Instead of using DC subcarriers outside the bandwidth center to estimate the Rx DC component, the patent inverts the approach by using the single DC subcarrier at the bandwidth center itself for estimation. This is achieved by sampling the signal at specific time points and using the phase difference between these samples to calculate the frequency offset and subsequently estimate the Rx DC component on the DC subcarrier.
Solution Approach 2:
The patent changes the estimation parameters by utilizing time-domain sampling at specific points (e.g., first sampling point at time t1, second sampling point at time t2) rather than frequency-domain analysis of multiple subcarriers. By calculating the phase difference between these time samples and using the known frequency offset, the method adapts the estimation approach to work with a single DC subcarrier configuration.
2Device complexity
If zero intermediate frequency receiver is used to simplify receiver structure, then device complexity is reduced, but large frequency offset causes severe interference to the received signal
Solution Approach 1:
The patent applies preliminary action by estimating and compensating for the Rx DC component before it causes severe interference to the data transmission. The method calculates the frequency offset using training fields or preamble sequences, then uses this offset information to estimate and remove the Rx DC component from the received signal, preventing its harmful effects on subsequent data demodulation.
Solution Approach 2:
The patent implements feedback by using the estimated frequency offset to continuously adjust and compensate for the Rx DC component. The system measures the frequency offset, calculates the corresponding Rx DC component estimate, applies compensation, and can iteratively refine this process to maintain signal quality despite the simplified zero intermediate frequency receiver architecture.
Data Source
AI summary
Embodiments of this application disclose a signal processing method and a communication apparatus, to obtain an estimated value of a receive end-direct current (Rx DC) component based on a sampling point of a signal. In this application, for a specified data frame including one or more direct current (DC) subcarriers or a field in the data frame, the signal is sampled in a first time period to obtain at least one first sampling point, the signal is sampled in a second time period after the first time period to obtain at least one second sampling point corresponding to the at least one first sampling point, and then the estimated value of the Rx DC component is obtained based on the at least one first sampling point, the at least one second sampling point, and a normalized frequency offset.