Satellite Interference Cancellation via Power Series Expansion

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Solution Overview

Problem

Existing digital data modulation systems in satellite communication face challenges in canceling nonlinear-distorted interference, particularly due to dispersive nonlinear channels caused by power amplifiers, which limits frequency reuse and requires techniques that can handle such distortions effectively.

Innovation Solution

A receiving apparatus and method that utilizes a series expansion of nonlinearity to estimate and cancel distorted interference, incorporating a receiver filter/sampler, synchronizer/sampler, vector power series generator, source multiplier, interference filter, weight generator, and combiner to produce a residual-interference signal for demodulation, enabling efficient initialization and adaptation to changing conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional Volterra series expansion techniques are used for interference cancellation, then the system can handle nonlinear distortions, but the convergence is slow and adaptation to changing conditions is inefficient

Engineering Contradiction:

Improveconvergence speedVSAvoidinitialization and adaptation time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent transforms the conventional Volterra series expansion parameters into a new parameterization based on signal power levels. By expressing the nonlinear distortion as a function of power ratios rather than traditional Volterra kernels, the system achieves faster convergence and more efficient adaptation to changing signal conditions without requiring extensive re-initialization

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamic adaptation of the interference cancellation parameters based on real-time signal conditions. The system continuously updates the power series expansion coefficients according to changing signal power levels and interference characteristics, enabling rapid adaptation to varying communication conditions without full re-initialization

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If the local terminal uses a larger diameter antenna with higher gain, then the received signal strength increases, but the relayed interference problem becomes more difficult to cancel

Engineering Contradiction:

Improvereceived signal energyVSAvoidrelayed interference level

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent replaces traditional mechanical/physical approaches to interference cancellation (such as simple filtering or linear cancellation) with a nonlinear power series expansion method. This mathematical transformation allows the system to effectively cancel interference that has been distorted by nonlinear power amplifiers, achieving cancellation performance that was previously unattainable with conventional linear techniques

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs feedback mechanisms where the estimated distorted interference is continuously refined based on the residual error after cancellation. The system uses the difference between the actual received signal and the cancelled signal to update and improve the interference estimation, achieving better cancellation performance iteratively

Inventive Principle:

Principle #23Feedback

3Productivity

If frequency reuse is implemented in satellite communication links, then bandwidth efficiency increases, but nonlinear-distorted interference from power amplifiers limits the achievable cancellation performance

Engineering Contradiction:

Improvebandwidth utilizationVSAvoidcancellation performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent fundamentally changes the parameter representation of nonlinear distortion from traditional Volterra kernels to power series expansion coefficients based on signal power ratios. This parameter transformation enables effective modeling and cancellation of nonlinear distortions in frequency-reuse scenarios, achieving reliability levels that support practical frequency reuse implementation

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9608718B2Method and apparatus for demodulation of a desired signal by constellation-independent cancellation of nonlinear-distorted interference

Publication Date: 2017.03.28 PM ASSOC

AI summary

A method and apparatus are provided for demodulating a received signal containing modulated desired-signal digital data and relayed-interference that results from a nonlinear-distorted interference signal. Estimation of the nonlinear-distorted interference from a pre-distortion interference signal and subsequent cancellation within the received signal of the distorted interference produces a residual-interference signal that is subsequently demodulated to produce estimates of the desired-signal data. The estimation is adapted for changing nonlinear distortion effects.