High-Frequency Circuit Duplexer Harmonic Interference

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Solution Overview

Problem

In high-frequency circuits using carrier aggregation technology, the distorted signal of a lower frequency band can become stronger than the receive signal of a higher frequency band due to harmonic interference, causing signal burial and reduced isolation between antenna terminals.

Innovation Solution

Incorporating a low-pass filter (LPF) or band-pass filter (BPF) between the antenna and the switch in the high-frequency circuit to block harmonics of the transmit signal, ensuring that the electrical power of the transmit signal is attenuated to a level below the receive signal power, thereby preventing interference with the higher frequency band signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If carrier aggregation technology is used to simultaneously transmit and receive signals using different frequency bands, then communication capacity is improved, but harmonic interference from lower frequency bands can overpower higher frequency band receive signals

Engineering Contradiction:

Improvecommunication capacityVSAvoidharmonic interference

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

A filter is introduced as an intermediary component between the antenna and the receiver to block harmonic frequencies from lower bands while allowing higher frequency band signals to pass through, thus preventing harmonic interference without affecting the carrier aggregation functionality

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful harmonic components are extracted and removed from the signal path using a filter that specifically targets and blocks these frequencies, separating the useful higher frequency band signals from the harmful lower frequency band harmonics

Inventive Principle:

Principle #2Taking out (Extraction)

2Productivity

If multiple frequency bands are aggregated for simultaneous transmission and reception, then signal throughput is improved, but isolation between antenna terminals deteriorates

Engineering Contradiction:

Improvesignal throughputVSAvoidisolation between antenna terminals

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A filter is placed in the signal path as an intermediary to selectively block harmonic frequencies, thereby maintaining signal isolation between different frequency bands while preserving the ability to simultaneously transmit and receive on multiple bands

Inventive Principle:

Principle #24Intermediary (Mediator)

3Length of moving object

If the transmit signal power is increased to improve transmission distance, then coverage is improved, but the distorted transmit signal becomes stronger and interferes with receive signals

Engineering Contradiction:

Improvecoverage distanceVSAvoiddistorted transmit signal

Core Design Contradiction:

Length of moving objectVSObject-generated harmful factors

Solution Approach 1:

The filter converts the harmful effect of high-power transmit signals by blocking their harmonic distortions, allowing the system to operate at higher transmit powers for extended coverage while the harmonics are converted from harmful interference into blocked frequencies that do not affect receive signals

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

The solution effectively reduces the power of the third-order or second-order harmonics of the transmit signal, preventing them from overpowering the receive signal, thus maintaining clear reception in higher frequency bands and enhancing signal isolation between antenna terminals.

Implementation Method 1

an LPF or BPF that is connected between the first antenna and the first switch, and passes a signal in the first transmit band and the first receive band

Methodology Applied

Scientific EffectFilter (electronic): Filter (electronic)

Data Source

PatentUS9252832B2High-frequency circuit and communication device

Publication Date: 2016.02.02 TAIYO YUDEN KK

AI summary

A high-frequency circuit includes: first duplexers, each including a first transmit filter having a first transmit band, a first receive filter having a first receive band, and a first common terminal to which first ends of the first transmit filter and the first receive filter are commonly connected; a first switch that selects and connects one of the first common terminals to a first antenna; an LPF or BPF that is connected between the first antenna and the first switch, and passes a signal in the first transmit band and the first receive band; and a second duplexer including: a second transmit filter having a second transmit band, a second receive filter having a second receive band, and a second common terminal that is connected to a second antenna and to which first ends of the second transmit filter and the second receive filter are commonly connected.