Coupled-Line RF Phase Shifter for Stable Return Loss and Group Delay

Solution Overview

Problem

Current RF phase shifters face challenges in providing high-frequency performance, maintaining constant return loss across phase settings, and minimizing group delay variation with frequency, which affects their ability to handle wideband signals effectively in advanced cellular technologies like 5G NR.

Innovation Solution

The design incorporates a phase shifter with a first and second controllable reflective load, each featuring a switched transmission line loaded with shunt switches, and a pair of coupled lines that are electromagnetically coupled, allowing for adjustable even mode impedance, odd mode impedance, and length to achieve desired performance characteristics, including high-frequency operation and minimal group delay variation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional phase shifters are used, then basic phase shifting function is provided, but high-frequency performance is not achieved and group delay variation with frequency is significant

Engineering Contradiction:

Improvehigh-frequency performanceVSAvoidgroup delay variation

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The phase shifter is divided into multiple independently controllable sections, each with its own reflective load and shunt switches. This segmentation allows each section to be optimized for high-frequency operation while collectively providing the full phase shifting range, thereby improving high-frequency performance while maintaining stable group delay characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The phase shifter employs dynamically switchable reflective loads with shunt switches that can be selectively activated based on the desired phase shift amount. This dynamic configuration allows the impedance and electrical length to be adjusted in real-time, optimizing performance across different operating conditions and frequencies, thus reducing group delay variation.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If phase shifting is implemented using conventional methods, then phase control is achieved, but return loss varies across different phase settings

Engineering Contradiction:

Improvephase controlVSAvoidreturn loss consistency

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The invention changes the impedance parameters of the reflective loads by selectively activating different combinations of shunt switches. This allows the reflection coefficient magnitude to be maintained at approximately -10 dB across all phase settings by adjusting the effective electrical length and impedance of each section, thereby achieving consistent return loss while maintaining full phase control capability.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If simple transmission line phase shifters are used, then device complexity is low, but performance in wideband signals is poor due to group delay variation

Engineering Contradiction:

Improvestructure simplicityVSAvoidwideband signal handling

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The phase shifter is divided into multiple independently controllable sections, each with its own reflective load and shunt switches. This segmentation allows each section to be optimized for high-frequency operation while collectively providing the full phase shifting range, thereby improving high-frequency performance while maintaining stable group delay characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The phase shifter employs dynamically switchable reflective loads with shunt switches that can be selectively activated based on the desired phase shift amount. This dynamic configuration allows the impedance and electrical length to be adjusted in real-time, optimizing performance across different operating conditions and frequencies, thus reducing group delay variation.

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration enables high-frequency performance, consistent return loss across phase settings, and minimal distortion of wideband signals, making it suitable for applications in 5G NR and other advanced cellular technologies.

Implementation Method 1

a pair of coupled lines that are electromagnetically coupled to one another

Methodology Applied

Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Data Source

PatentUS11791800B2Apparatus and methods for phase shifting

Publication Date: 2023.10.17 SKYWORKS SOLUTIONS INC

AI summary

Apparatus and methods for phase shifting are provided herein. In certain embodiments, a phase shifter includes a first port, a first controllable reflective load, a second port, a second controllable reflective load, and a pair of coupled lines that are electromagnetically coupled to one another. The pair of coupled lines includes a first conductive line between the first port and the first controllable reflective load and a second conductive line between the second controllable reflective load and the second port. At least one of the first controllable reflective load or the second controllable reflective load includes a switched transmission line load.