Blocker Cancellation Circuit for Wideband LNA Sensitivity

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Solution Overview

Problem

Portable wireless devices face desensitization of low noise amplifiers due to powerful blocker signals, which affect their ability to receive and process signals effectively in wide band receiving applications.

Innovation Solution

A system comprising a main amplifier, auxiliary amplifiers, and a combiner with a load that adjusts phase and filters to cancel blocker components, ensuring equal amplitude and 180-degree phase difference between signal and blocker components, thereby reducing blocker interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the receiver processes wide band signals, then the receiving capability is improved, but the low noise amplifiers become desensitized due to powerful blocker signals

Engineering Contradiction:

Improvereceiving capabilityVSAvoidamplifier sensitivity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The signal processing is divided into multiple stages: a first LNA processes wideband signals initially, then a filter separates blocker frequencies, and a second LNA processes the filtered signal. This segmentation allows each amplifier to operate optimally without desensitization from blockers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A filter is introduced as an intermediary component between the first LNA and the second LNA. This filter mediates the signal path by removing blocker frequency components before they reach the second LNA, preventing desensitization while maintaining wideband receiving capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If the amplifier amplifies all received signals, then the signal strength is improved, but the blocker components interfere with target signal processing

Engineering Contradiction:

Improvesignal strengthVSAvoidblocker interference

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The filter extracts and removes blocker frequency components from the amplified signal. By taking out the harmful blocker components after amplification, the system maintains strong signal strength while eliminating interference with target signal processing.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system uses the blocker signals themselves to generate cancellation signals. The blocker components are amplified and processed to create phase-inverted versions that cancel the original blockers, converting the harmful interference into a beneficial cancellation mechanism.

Inventive Principle:

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

3Measurement precision

If the receiver uses low noise amplifiers for wide band receiving, then the signal reception is improved, but the amplifiers become desensitized by blocker signals

Engineering Contradiction:

Improvesignal reception qualityVSAvoidblocker desensitization

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The first LNA performs preliminary amplification of the wideband signal before filtering. This preliminary action ensures that both target and blocker signals are amplified early, allowing the subsequent filter to remove blockers while preserving the amplified target signal for further processing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback mechanisms where the output signal is processed to generate cancellation signals that are fed back to cancel blocker components. This feedback loop continuously reduces blocker interference, maintaining amplifier sensitivity and signal reception quality.

Inventive Principle:

Principle #23Feedback

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 solution enhances the sensitivity of amplification systems by effectively canceling blocker components, improving the device's ability to amplify target signals while reducing interference, thus enhancing the overall performance in wide band receiving applications.

Implementation Method 1

a second signal path coupled to receive the input signal and adjust a phase of the input signal to generate a cancellation signal

Methodology Applied

Scientific EffectPhase shift:

Implementation Method 2

The combiner is coupled to combine the first output signal with the cancellation signal to reduce the blocker components

Methodology Applied

Scientific EffectSignal cancellation: Interference

Data Source

PatentUS9225369B2Filtering blocker components of a signal

Publication Date: 2015.12.29 QUALCOMM INC

AI summary

An apparatus includes a main amplifier configured to receive an input signal. The main amplifier is also configured to generate an output signal. The apparatus also includes an auxiliary path configured to phase-shift the input signal to generate a cancellation signal to reduce or cancel a blocker component of the output signal.