OFDM Baseband Receiver Equalizer Using Conjugate Multiplication
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Solution Overview
Problem
Existing OFDM baseband receivers face signal distortion due to the imprecision of channel state information inversion in equalization, which requires significant memory and hardware resources to improve accuracy, and this imprecision leads to errors in the output signal.
Innovation Solution
The OFDM baseband receiver eliminates the need for a reciprocal circuit by multiplying the input signal with the conjugate of the channel impulse response and directly outputting the product signal without dividing by the channel state information, thereby avoiding the errors induced by inaccurate inversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a reciprocal circuit with a table storing multiple exponents and mantissas is used to implement division for signal processing, then the equalization function is achieved, but the manufacturing precision of the inverse value approximation deteriorates due to limited table values
Solution Approach 1:
The patent extracts and eliminates the reciprocal circuit from the OFDM baseband receiver architecture. By removing the division operation entirely and using only multiplication with channel impulse response conjugates, the system avoids the precision limitations inherent in table-based approximation methods while maintaining equalization functionality
Solution Approach 2:
Instead of computing the inverse of channel state information (1/CSI) through division operations, the patent inverts the approach by directly multiplying the received signal with the conjugate of the channel impulse response. This eliminates the need for reciprocal calculation and its associated approximation errors
2Manufacturing precision
If the number of values stored in the table of the reciprocal circuit is increased to improve the accuracy of 1/CSI, then the manufacturing precision of inverse value approximation is improved, but the device complexity increases due to greater memory capacity requirements
Solution Approach 1:
The patent removes the reciprocal circuit and its associated lookup table from the system architecture. By eliminating the division operation and replacing it with direct multiplication, the system achieves accurate equalization without requiring additional memory resources for storing approximation tables
Solution Approach 2:
The patent replaces the expensive and complex reciprocal circuit with a simpler multiplication operation that requires no additional memory storage. This substitution uses computationally efficient operations that consume fewer hardware resources while achieving the same equalization goal
3Ease of manufacture
If a reciprocal circuit is used to generate approximation of inverse of channel state information, then the equalization function is implemented, but the reliability of output signal deteriorates due to approximation errors inducing signal distortion
Solution Approach 1:
The patent extracts and eliminates the source of approximation errors by removing the reciprocal circuit. By using direct multiplication with channel impulse response conjugates instead of table-based division approximation, the system achieves reliable signal equalization without introducing artificial distortion
Solution Approach 2:
The patent employs maximum ratio combining (MRC) equalization which inherently provides optimal signal-to-noise ratio performance. This approach uses feedback from channel estimation to directly compute the equalized signal, eliminating the need for separate reciprocal calculation and reducing error propagation
Data Source
AI summary
A method for implementing an equalizer of an orthogonal frequency division multiplexing (OFDM) baseband receiver is provided. The OFDM baseband receiver includes a channel estimation and tracking module for estimating a channel impulse response of an input signal of the equalizer. A conjugate of the channel impulse response is first calculated. The input signal and the conjugate of the channel impulse response are then multiplied to generate a product signal. The product signal is then taken as the output signal of the equalizer without dividing the product signal by a channel state information, wherein the channel state information represents a square of an absolute value of the channel impulse response.