Frequency-Shifting Circuit for Idle Downlink Interference

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Solution Overview

Problem

Existing communication systems face interference issues due to idle downlink signal paths generating noise that affects uplink signal reception, and achieving sufficient electrical isolation is costly and difficult.

Innovation Solution

Implementing a frequency-shifting circuit to shift interference signals out of the uplink signal path's frequency band during idle periods and using directional antennas to isolate downlink and uplink paths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If electrical isolation between downlink and uplink signal paths is implemented, then interference from idle downlink path is reduced, but device complexity and cost increase

Engineering Contradiction:

Improveinterference from idle downlink pathVSAvoidisolation circuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent extracts the interference signal from the idle downlink signal path and processes it separately through a dedicated interference cancellation path. This involves coupling the idle downlink path to an interference cancellation path that includes its own mixer, local oscillator, and filter, allowing the interference to be processed and cancelled without affecting the main uplink signal path, thus reducing interference while minimizing complexity in the primary signal paths

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary interference cancellation path that acts as a mediator between the idle downlink signal path and the uplink signal path. This intermediate path processes the interference signal through mixing and filtering operations, and the processed interference is then subtracted from the uplink signal, providing isolation without requiring direct electrical isolation between the downlink and uplink paths

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If downlink signal path components remain active during idle periods, then transition time and voltage fluctuations are reduced, but interference signal generation increases

Engineering Contradiction:

Improvesignal path stabilityVSAvoidinterference signal from idle downlink path

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful interference signal generated by active components in the idle downlink path into a useful cancellation signal. By processing the idle downlink path through a mixer and local oscillator to generate an interference model, and then subtracting this model from the uplink signal, the previously harmful interference is transformed into a benefit that improves uplink reception quality

Inventive Principle:

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

Solution Approach 2:

The patent implements a feedback mechanism where the idle downlink signal path is continuously monitored and processed through the interference cancellation path. The processed interference signal is fed back and subtracted from the uplink signal in real-time, creating a closed-loop system that actively compensates for interference generated by active components during idle periods

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If frequency-shifting circuit is implemented, then interference signals are shifted out of uplink band, but device complexity increases

Engineering Contradiction:

Improveinterference in uplink frequency bandVSAvoidfrequency-shifting circuit complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent segments the signal processing into distinct functional paths: the main uplink signal path, the idle downlink signal path, and the interference cancellation path. Each path has dedicated components (mixers, local oscillators, filters) that process specific signals independently. This segmentation allows frequency shifting and interference cancellation to be implemented in a modular fashion, reducing overall system complexity while effectively removing interference from the uplink band

Inventive Principle:

Principle #1Segmentation

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

Effectively reduces interference by shifting interference signals away from the uplink band, improving signal quality and reducing oscillations in the closed loop formed by downlink and uplink paths.

Implementation Method 1

a frequency-shifting circuit to shift interference signals out of the uplink signal path's frequency band

Methodology Applied

Scientific EffectFrequency mixing: Heterodyne

Data Source

PatentUS12445164B2Shifting a frequency band of an interference signal out of a pass band of a signal path

Publication Date: 2025.10.14 ANDREW WIRELESS SYSTEMS GMBH(DE)

AI summary

In an embodiment, a communication circuit includes a frequency-shifting circuit coupled to a signal path, which is configured to carry, during a first period, an information signal having a first frequency. The frequency-shifting circuit is configured to receive a control signal, to shift the first frequency of the information signal by a second frequency in response to the control signal having a first control value, and to shift a third frequency of an interference signal on the signal path during a second period by a fourth frequency in response to the control signal having a second control value. For example, such a communication signal can be configured to shift the frequencies of an interference signal generated by the signal path out of the passband of an adjacent signal path to reduce the interference superimposed on a signal carried by the adjacent signal path.