Direct RF Sampling for MIMO DPD Calibration Without Downconversion

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current digital pre-distortion calibration technologies for MIMO transceivers require large circuit footprints and increased costs due to the inclusion of components like mixers, subtractors, and filters for downconverting signals, which also introduce insertion loss.

Innovation Solution

Implementing direct sampling for digital pre-distortion calibration by using a data converter to sample signals at a baseband frequency, eliminating the need for downconverting components and reducing the circuit footprint, while calibrating pre-distortion parameters to compensate for non-linearity in power amplifier amplification.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If downconverting components (mixers, subtractors, filters) are included for signal downconversion, then signal frequency conversion is achieved, but circuit footprint increases and production costs increase

Engineering Contradiction:

Improvesignal frequency conversionVSAvoidcircuit footprint

Core Design Contradiction:

SpeedVSArea of stationary object

Solution Approach 1:

The patent extracts and eliminates the downconverting components (mixers, subtractors, filters) from the calibration signal path. By using direct sampling, the calibration signal is sampled directly at the RF frequency without being downconverted to baseband, removing the need for these components and reducing circuit footprint while maintaining frequency conversion capability through digital signal processing

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the analog downconversion mechanism (mixers and filters) with a digital sampling approach. The data converter directly samples the RF calibration signal and generates digital samples that are then processed digitally to achieve the equivalent of downconversion, substituting mechanical/analog components with digital processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If downconverting components (mixers, subtractors, filters) are included for signal downconversion, then signal frequency conversion is achieved, but production costs increase

Engineering Contradiction:

Improvesignal frequency conversionVSAvoidproduction costs

Core Design Contradiction:

SpeedVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces expensive analog downconversion components with a data converter and digital processing elements that are more cost-effective. The direct sampling approach uses standard data converters and digital signal processing algorithms that reduce bill of materials costs and simplify manufacturing

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Speed

If downconverting components are included for signal downconversion, then signal frequency conversion is achieved, but insertion loss is introduced

Engineering Contradiction:

Improvesignal frequency conversionVSAvoidinsertion loss

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates a digital copy of the RF calibration signal through direct sampling. The data converter captures the RF signal directly and creates digital representations that can be processed without physical downconversion, preserving signal energy and avoiding insertion loss associated with analog components

Inventive Principle:

Principle #26Copying

4Manufacturing precision

If pre-distortion parameters are calibrated to compensate for PA non-linearity, then signal distortion is reduced, but calibration complexity increases

Engineering Contradiction:

Improvesignal distortion compensationVSAvoidcalibration complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements a calibration process where the transmitted calibration signal is sampled and the received signal characteristics are fed back to adjust pre-distortion parameters. The DPD circuit uses the sampled calibration signal to determine optimal pre-distortion settings that compensate for power amplifier non-linearity, creating a closed-loop feedback system for automatic calibration

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11165517B2Direct sampling for digital pre-distortion calibration

Publication Date: 2021.11.02 MAXLINEAR INC

AI summary

A MIMO transceiver may include a communication chain configured to generate a signal at a first frequency and that includes a pre-distorter configured to accept pre-distortion parameters to pre-distort signals and a PA to amplify the signals. The MIMO transceiver may include a DPD chain configured to receive the signal at the first frequency and that includes a data converter to sample the signal using a sampling rate based on a baseband frequency and to generate a sample signal based on the sampling of the signal. The MIMO transceiver may include a buffer configured to buffer the sample signal. The MIMO transceiver may include a DPD circuit configured to calibrate the pre-distortion parameters based on the buffered sample signal. The MIMO transceiver may include a CTS circuit to transmit a CTS-to-Self signal within an operational environment to reserve a duration of time for the MIMO transceiver to perform DPD calibration.