Satellite Pre-equalizer for Asymmetric Group Delay Compensation

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Solution Overview

Problem

Modern communication satellite designs face challenges in increasing throughput while adhering to strict weight and power constraints, as solid-state components used to enhance performance can cause forward-link distortions, limiting symbol rate and throughput.

Innovation Solution

Implementing a pre-equalizer in the demodulator of satellite receiver terminals with dynamically updated filter coefficients to compensate for channel filter distortions, ensuring reliable decoding and increased symbol rate across the entire channel bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of stationary object

If solid-state components are used in satellite filters to reduce weight and size, then weight and payload constraints are improved, but forward-link distortions and asymmetric group delay responses are introduced that limit symbol rate and throughput

Engineering Contradiction:

Improvesatellite payload weightVSAvoidsymbol rate

Core Design Contradiction:

Weight of stationary objectVSProductivity

Solution Approach 1:

The patent converts the harmful asymmetric group delay distortion introduced by solid-state filters into a benefit by computing pre-equalizer filter coefficients that are specifically designed to compensate for this distortion. The system measures or characterizes the asymmetric group delay response of the solid-state filters and uses this information to create compensation filters that restore symmetric group delay response, thereby enabling higher symbol rates while maintaining the weight advantages of solid-state components

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies pre-equalization filtering to the transmitted signal before it passes through the asymmetric solid-state filters. By computing and applying pre-equalizer filter coefficients in advance (prior to transmission through the distorted channel), the system pre-compensates for the anticipated asymmetric group delay distortion, ensuring that the overall system response remains symmetric and supports higher symbol rates

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the number of beams is increased to support more terminals, then throughput is improved, but the number of components and system complexity increase

Engineering Contradiction:

ImprovethroughputVSAvoidnumber of components

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent changes the parameter of filter response symmetry by applying pre-equalizer filter coefficients that transform the asymmetric group delay response of solid-state filters into a symmetric response. This parameter change enables the system to operate at higher symbol rates across all beams without requiring additional hardware components, thereby increasing throughput while maintaining the same component count

Inventive Principle:

Principle #35Parameter changes

3Reliability

If power to beams is increased to improve signal-to-noise ratio, then throughput is improved, but power consumption and heat generation increase

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidbeam power

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent replaces the mechanical/power-based approach of increasing beam power to improve SNR with a signal processing approach. By applying pre-equalizer filter coefficients that compensate for asymmetric group delay distortion, the system enables more efficient signal transmission that maintains or improves SNR without requiring additional power, thereby reducing heat generation and power consumption while maintaining reliable communication

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11916704B2Pre-equalizer at the terminal to compensate for forward link distortions

Publication Date: 2024.02.27 HUGHES NETWORK SYST

AI summary

Techniques are described for pre-equalization at the demodulator of a satellite receiver terminal to compensate for forward link distortions. Some satellite channel filters can manifest distortions, such as asymmetric group delay response. Such distortions can conventionally force restriction of symbol rate only to the portion of the channel bandwidth having a symmetric filter response. Embodiments include a pre-equalizer in the demodulation path that filters received downlink communications based on a set of pre-equalizer filter coefficients computed to at least partially compensate for the channel filter distortions. Some embodiments support updating the filter coefficients based on channel reassignments, and/or dynamically updating the filter coefficients based on detecting and exploiting pre-equalization frames. The pre-equalized sample stream can facilitate reliable decoding by the demodulator with an appreciably increased symbol rate and correspondingly increased forward link capacity.