N-Path Filter Phase Driving for Wider Frequency Tuning

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Solution Overview

Problem

Existing N-path filters with base filters containing series arm elements with reactance components face limitations in frequency variable range due to unwanted response modes, making it difficult to achieve the desired frequency variable width.

Innovation Solution

The N-path filter design includes multiple signal paths with modulators and base filters, each containing a series arm element with a reactance component, where the modulators are driven by phase-completed signals across the paths, allowing for wide frequency variable width by reducing unwanted response modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If base filters with series arm elements containing reactance components are used in N-path filters, then the filter can be implemented with practical components, but unwanted response modes occur and the frequency variable range is limited

Engineering Contradiction:

Improveimplementability of filterVSAvoidfrequency variable range

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent converts the harmful unwanted response modes caused by reactance components into beneficial effects by using phase-completed drive signals. The opposite-phase driving of modulators causes unwanted modes to cancel each other out while preserving the desired filtering function, thus transforming a manufacturing advantage into a performance solution.

Inventive Principle:

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

Solution Approach 2:

The patent changes the phase parameter of the drive signals to resolve the contradiction. By setting drive signals with opposite phases for modulators in different signal paths, the system achieves both practical implementability with reactance components and extended frequency variable range through destructive interference of unwanted modes.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If base filters with series arm elements containing reactance components are used in N-path filters, then the filter structure is simplified, but time response shifts occur during switching and unwanted response modes are generated

Engineering Contradiction:

Improvefilter structure complexityVSAvoidsignal response accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent transforms the harmful time response shifts and unwanted modes into beneficial cancellation effects. By driving modulators with opposite-phase signals, the unwanted response modes generated by reactance components cancel each other, preserving signal accuracy while maintaining structural simplicity.

Inventive Principle:

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

Solution Approach 2:

The patent applies preliminary anti-action by pre-configuring drive signals with opposite phases before switching occurs. This anticipatory measure prevents unwanted response modes from affecting signal accuracy, as the phase-completed driving arrangement is established in advance to counteract the inherent reactance effects.

Inventive Principle:

Principle #9Preliminary anti-action

3Adaptability or versatility

If the frequency variable range is extended to accommodate unwanted response modes, then the main response mode frequency variable width is reduced, but if the range is limited to avoid unwanted modes, then the filter cannot achieve desired frequency variable width

Engineering Contradiction:

Improvefrequency variable widthVSAvoidresponse mode purity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent resolves this contradiction by converting unwanted response modes into beneficial cancellation effects through opposite-phase driving. This allows the frequency variable range to be extended without sacrificing response mode purity, as the harmful modes cancel each other rather than contaminating the passband.

Inventive Principle:

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

Solution Approach 2:

The patent changes the phase parameter of drive signals to simultaneously achieve extended frequency variable width and maintained response purity. By adjusting the phase relationship between modulators, the system expands the usable frequency range while keeping unwanted modes suppressed through phase-completed interference.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250070761A1N-path filter

Publication Date: 2025.02.27 MURATA MFG CO LTD

AI summary

An N-path filter includes first signal paths connected in parallel with each other between signal terminals and second signal paths. Each of the first signal paths includes first and second switches connected to the signal terminals, and a base filter connected between the first and second switches. Each of the second signal paths includes a third switch connected to a signal terminal. The base filter includes a series arm element including a reactance component. The first and second switches modulate an input signal with a phase that completes one cycle across the signal paths, and the third switch modulates the input signal with a phase that completes one cycle across the signal paths. A phase of a drive signal to drive the second switch is opposite to a phase of a drive signal to drive the third switch.