Radio Transmitter Distortion Mitigation via Null-Space Shaping

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Solution Overview

Problem

Large antenna array systems face a trade-off between cost and performance due to excessive transmit signal distortion, limiting their spatial duplexing ability and increasing production costs.

Innovation Solution

A transmitter system that adds shaping components based on the null-space of the channel matrix H to the transmit signal components, optimizing the signal for the specific properties of the transmit unit and reducing distortion without increasing overall cost, using a pre-coder connected to an antenna array with M antenna elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If dedicated transmit circuitry (DAC and PA) is provided for each antenna element, then transmitter performance in terms of distortion is improved, but power consumption and production cost increase

Engineering Contradiction:

Improvetransmitter performanceVSAvoidpower consumption

Core Design Contradiction:

Manufacturing precisionVSUse of energy by stationary object

Solution Approach 1:

The patent combines multiple transmit signal components into fewer transmit units, where a single DAC and PA serve multiple antenna elements. This merging of circuitry reduces the total number of components required, thereby lowering power consumption and production cost while maintaining transmitter performance through coordinated signal processing.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent makes transmit units serve multiple functions by having a single DAC and PA configuration handle multiple antenna elements. The pre-coder processes signals to enable these shared transmit units to support multiple spatial streams, making the transmit circuitry universal rather than dedicated to single elements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If dedicated transmit circuitry is provided for each antenna element, then transmitter performance is improved, but production cost increases

Engineering Contradiction:

Improvetransmitter performanceVSAvoidproduction cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent merges the functionality of multiple dedicated transmit circuits into shared transmit units. By combining DACs and PAs to serve multiple antenna elements, the system reduces the total component count, which directly lowers production costs while maintaining the required transmitter performance through multi-user MIMO processing.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses signal processing techniques to create virtual copies of transmit signals through the pre-coder, allowing shared hardware to generate multiple spatially distinct beams. This enables the system to achieve performance equivalent to dedicated circuits without duplicating the expensive hardware components.

Inventive Principle:

Principle #26Copying

3Ease of manufacture

If low-cost antenna arrangements are used, then production cost is reduced, but spatial duplexing ability is limited due to excessive transmit signal distortion

Engineering Contradiction:

Improveproduction costVSAvoidspatial duplexing ability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent changes the signal parameters through pre-coding to compensate for the limitations of low-cost transmit units. By transforming the transmit signal components and utilizing null-space properties, the system maintains spatial duplexing capability despite using cost-reduced hardware configurations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The pre-coder acts as an intermediary that processes signals before they reach the shared transmit units. This intermediate processing stage compensates for the hardware limitations, enabling spatial duplexing functionality that would otherwise be lost in low-cost configurations.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Use of energy by stationary object

If shared transmit units are used for multiple antenna elements, then power consumption and cost are reduced, but transmit signal distortion increases

Engineering Contradiction:

Improvepower consumptionVSAvoidtransmitter performance

Core Design Contradiction:

Use of energy by stationary objectVSManufacturing precision

Solution Approach 1:

The patent applies parameter transformations through the pre-coder to optimize signals for shared transmit units. By adjusting signal parameters and utilizing channel null-space properties, the system maintains transmitter performance despite the non-ideal characteristics of shared, lower-cost hardware.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10218421B2Radio transmitter for distortion mitigation

Publication Date: 2019.02.26 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A transmitter for radio transmission to one or more receivers over a channel described at least in part by a channel matrix H, the transmitter comprising a pre-coder connected to an antenna array via a transmit unit, the antenna array comprising a number M of antenna elements am, m=1, 2, . . . , M, each antenna element am being configured to receive a respective transmit signal component xm from the pre-coder via the transmit unit, the pre-coder being configured to receive a number K<M of data streams sk, k=1, 2, . . . , K, and to generate the M transmit signal components, wherein the generating comprises adding M shaping components em, m=1, 2, . . . , M, to respective transmit signal components xm, the shaping components em being generated based on a null-space of the channel matrix H and on one or more properties of the transmit unit.