Beamspace Volterra Filtering for Phased Array Intermodulation Suppression
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Solution Overview
Problem
Current signal processing systems, particularly in radar and communication systems, face challenges in mitigating odd-order intermodulation distortion, which limits the ability to detect weak signals and is exacerbated by non-linearities in components like ADCs, leading to reduced dynamic range and performance.
Innovation Solution
The implementation of nonlinear digital Volterra-based filters to cancel odd-order intermodulation distortion, with the residue being decorrelated across channels, improving performance by using a single non-linear equalization coefficient set generated in beamspace and applied across all elements in the array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-linear components like ADCs are used in signal processing systems, then system functionality and signal processing capability are improved, but odd-order intermodulation distortion is generated which limits dynamic range and detection capability
Solution Approach 1:
The patent applies Volterra filters to model and invert the non-linear distortion characteristics of ADCs. By characterizing the intermodulation distortion through Volterra series expansion and then applying inverse filters, the harmful distortion products are converted into beneficial cancellation effects, allowing the system to achieve high dynamic range performance while using practical non-linear components.
Solution Approach 2:
The patent changes the operating parameters of the signal processing system by applying non-linear equalization filters that dynamically adjust the signal characteristics. The Volterra filters modify the amplitude and phase parameters of the received signals to compensate for non-linear distortion, effectively transforming the system's parameter space to achieve linear operation despite using non-linear components.
2Device complexity
If traditional linear equalization is used, then simple signal processing is achieved, but odd-order intermodulation distortion cannot be canceled
Solution Approach 1:
The patent transitions from static linear equalization to dynamic non-linear equalization using Volterra filters. The filters incorporate memory effects and non-linear operations that adapt to the signal characteristics, enabling the system to dynamically cancel intermodulation distortion products that vary with input signal amplitude and frequency content.
Solution Approach 2:
The Volterra filters serve as intermediary processing elements between the non-linear ADC and the signal detection system. These filters act as a mediator that transforms the distorted signal into a form where intermodulation products are separated and can be selectively canceled, bridging the gap between non-linear component operation and linear signal processing requirements.
3Object-generated harmful factors
If individual NLEQ filters are applied to each channel, then channel-specific distortion is canceled, but device complexity and computational load increase significantly
Solution Approach 1:
The patent merges the NLEQ filter implementations by applying a single set of Volterra filter coefficients across all channels simultaneously. This unified approach combines the distortion cancellation function across multiple channels, reducing the overall number of filters required while maintaining effective intermodulation cancellation through the array processing gain.
Solution Approach 2:
The Volterra filter coefficients derived for one channel are made universal and applied to all channels in the array. This multi-functional approach allows the same filter implementation to serve multiple channels, reducing computational complexity and hardware requirements while the array processing itself provides additional distortion cancellation through coherent integration.
Data Source
AI summary
A method of beamforming is provided. A single non-linear equalization (NLEQ) coefficient set is generated in beamspace, the single NLEQ coefficient set configured to characterize non-linear behavior of a system having an array of N elements. M parallel digital signals are received, for transmission by N channels, respectively, the N channels corresponding to the N elements. Each of the M respective parallel digital signals are equalized, using an NLEQ filter based on the single NLEQ coefficient set, wherein the single NLEQ coefficient set is used for each of the N elements and wherein the equalizing is configured to generate a set of M linearized parallel digital signals. Using a single summer, the M linearized parallel digital signals are summed, to produce one or more beamspace channelized output signals.