Digital Predistortion Transmitter Split Paths for Reduced Receive-Band Noise

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Solution Overview

Problem

Traditional radio transmitters with digital predistortion face challenges in reducing noise within the synthesis bandwidth, leading to undesired interference and high costs due to the complexity and expense of cavity duplexers.

Innovation Solution

A radio transmitter system incorporating a high output power narrowband upconverter and a low output power wideband upconverter, where digital predistortion is applied by separating the predistortion signal into narrowband and wideband components, and upconverting them using digital-to-analog converters and modulators, with a summation block to combine the signals and correct for phase and amplitude differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If traditional digital predistortion is applied with wideband transmit signal, then power and efficiency are increased, but noise falls into receive band causing interference and sensitivity loss

Engineering Contradiction:

Improvetransmitter output powerVSAvoidnoise interference in receive band

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent segments the predistortion signal processing into separate narrowband and wideband paths. The narrowband path handles the transmit signal while the wideband path handles the predistortion correction products, allowing independent optimization of each path's bandwidth and filtering characteristics to prevent noise overlap with receive band

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent separates signal processing in the frequency domain by creating distinct narrowband and wideband transmission paths. This dimensional separation allows the system to maintain high power output while controlling noise distribution across different frequency bands, preventing receive band contamination

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Object-affected harmful factors

If cavity duplexers are used to reject receive band noise, then noise rejection is achieved, but system cost and complexity increase significantly

Engineering Contradiction:

Improvereceive band noiseVSAvoidcomplexity of cavity duplexer system

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent extracts the noise rejection function from the traditional cavity duplexer architecture and implements it through digital signal processing in the predistortion paths. By taking out the heavy hardware filtering requirement and replacing it with digital filtering in the narrowband/wideband separation, the system achieves noise rejection without the complexity and cost of cavity duplexers

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical/cavity-based filtering system with digital signal processing. The narrowband and wideband digital paths with their respective filters substitute for the physical cavity duplexer, achieving the same noise rejection function through electronic/digital means rather than mechanical resonance structures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If wideband predistortion signal is transmitted, then amplifier linearization is achieved, but bandwidth requirements increase and filtering becomes more difficult

Engineering Contradiction:

Improveamplifier linearityVSAvoidsynthesis bandwidth

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent segments the predistortion signal into narrowband transmit signal and wideband correction products, allowing the system to maintain amplifier linearization through predistortion while reducing the overall synthesis bandwidth by separating the signal components into distinct frequency ranges with appropriate filtering

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8824980B2System and method to implement a radio transmitter with digital predistortion having reduced noise

Publication Date: 2014.09.02 ANALOG DEVICES INC

AI summary

A system and method provide for a radio transmitter with digital predistortion. The radio transmitter includes a high output power narrowband upconverter and a low output power wideband upconverter. In a stage of the radio transmitter, digital predistortion is applied to transmit data by setting digital coefficients by a digital predistortion algorithm, resulting in a predistortion signal. A predistortion signal is separated into a narrowband component and a wideband component, where the narrowband component corresponds to a desired traffic signal and the wideband component corresponds to a digital predistortion signal reflecting separated digital predistortion correction products. The narrowband upconverter provides a transmission path for a desired traffic signal or transmit data (the narrowband component of the digital predistortion signal), while the wideband upconverter provides a transmission path for the wideband component representing digital predistortion correction products.