Quadrature Coupler Duplexer with 180-Degree Phase Shift for High Isolation

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Solution Overview

Problem

Traditional RF duplexers provide insufficient isolation between transmit and receive paths when TX and RX carrier signals are closely spaced in frequency, failing to meet system requirements.

Innovation Solution

A high isolation duplexer/quasi circulator design utilizing two quadrature couplers, where one TX-RX signal path is shifted at or near 180 degrees from the other, coupled with a phase shift circuit to combine signals in phase at the antenna port, enhancing isolation between the TX and RX ports.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional duplexer is used to provide isolation between TX and RX ports, then signal transmission and reception are enabled over a single antenna, but the isolation between TX and RX paths is insufficient when TX and RX carrier signals are closely spaced in frequency

Engineering Contradiction:

Improveisolation between TX and RX portsVSAvoidsignal transmission and reception capability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The invention divides the single duplexer path into two separate signal paths by introducing a second quadrature coupler. Each path contains a duplexer, and the two paths are combined at the antenna port with a 180-degree phase shift between them. This segmentation allows independent optimization of each path's isolation characteristics while maintaining overall system functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies preliminary anti-action by introducing a 180-degree phase shift between the two signal paths before they combine at the antenna port. This phase shift causes the TX leakage signals from the two paths to cancel each other out through destructive interference, thereby preemptively eliminating the isolation problem before it affects the RX signal quality.

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If magnetic circulator is used to route signals between TX port, antenna port, and RX port, then signal directionality is achieved, but the device becomes excessively large

Engineering Contradiction:

Improvesignal directionalityVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The invention replaces the magnetic circulator's mechanical/magnetic field-based signal routing with an electrical/phased-array approach. Instead of using a permanent magnet to physically direct signals, the invention uses two quadrature couplers with controlled phase shifts to achieve the same signal directionality and isolation through electromagnetic phase manipulation, resulting in a more compact device.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If two quadrature couplers are used to create two TX-RX signal paths with 180 degree phase shift, then isolation between TX and RX ports is improved to greater than 80 dB, but device complexity increases

Engineering Contradiction:

Improveisolation between TX and RX portsVSAvoidnumber of signal paths and phase shift circuits

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The two quadrature couplers serve multiple functions simultaneously: they split the TX signal into two paths, combine the RX signals from two duplexers, and provide the necessary 180-degree phase shift for isolation. This multi-functionality reduces the need for additional dedicated components, thereby managing device complexity while achieving superior isolation performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Achieves greater than 80 dB of isolation between the TX and RX ports, significantly improving upon traditional duplexer designs by 15 to 25 dB across relevant frequencies, preventing signal interference and damage to sensitive components.

Implementation Method 1

a first TX-RX signal path (from the TX port to the RX port) is shifted at or near 180 degrees from a second TX-RX signal path

Methodology Applied

Scientific EffectPhase shift:

Implementation Method 2

A phase shift circuit is coupled to the ANT port of one or both duplexers such that the signals passing through the quadrature couplers to the ANT port are combined substantially in phase

Methodology Applied

Scientific EffectPhase shifting:

Implementation Method 3

These paths cancel each other to provide a high level of isolation between the TX port and the RX port

Methodology Applied

Scientific EffectSignal cancellation: Interference

Data Source

PatentUS10686485B1High isolation duplexer/quasi circulator with two quadrature couplers

Publication Date: 2020.06.16 QORVO US INC

AI summary

A high isolation duplexer/quasi circulator with two quadrature couplers is disclosed. Isolation between a transmit (TX) port and receive (RX) port of the quasi circulator is improved through use of two quadrature couplers. The quadrature couplers are coupled such that a first TX-RX signal path (from the TX port to the RX port) is shifted at or near 180 degrees from a second TX-RX signal path. These paths cancel each other to provide a high level of isolation between the TX port and the RX port. There are two signal paths between an antenna (ANT) port and the quadrature couplers for both TX signals and RX signals. A phase shift circuit is coupled to the ANT port of one or both duplexers such that the signals passing through the quadrature couplers to the ANT port are combined substantially in phase.