Frequency Converter LO Phase Control for Harmonic Interference

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Solution Overview

Problem

Existing frequency converters and receivers face challenges in converting desired signals across a wide frequency range while effectively eliminating interference signals, particularly odd-order harmonics of the LO signal, while minimizing circuit area and power consumption.

Innovation Solution

A frequency converter with an LO signal generator capable of varying phase resolution and signal gain for each phase value, used in conjunction with a mixer to convert received signals, eliminates interference signals by optimizing FIR filter characteristics based on LO frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If SAW filters with wide pass bandwidth are used to reduce the number of band pass filters, then the pass bandwidth is improved, but interference signals with frequencies up to 10 times higher than the desired signal frequency are allowed to pass, requiring high linearity that increases power consumption

Engineering Contradiction:

Improvepass bandwidthVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The interference suppression function is segmented into multiple frequency domains by using multiple mixers with different LO frequencies. Each mixer handles a specific frequency range, allowing interference signals to be suppressed in a distributed manner rather than requiring a single high-linearity path

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the LO frequency parameter dynamically by selecting from multiple LO signals with different frequencies. This allows the mixer to adapt to different desired signal frequencies while maintaining the ability to suppress interference signals at various frequency offsets

Inventive Principle:

Principle #35Parameter changes

2Use of energy by stationary object

If a square wave LO signal is used to reduce circuit area and power consumption, then the circuit area and power consumption are reduced, but odd-order harmonics of the LO signal are generated, creating interference that cannot be eliminated by ordinary frequency converters

Engineering Contradiction:

Improvepower consumptionVSAvoidodd-order harmonics interference

Core Design Contradiction:

Use of energy by stationary objectVSObject-generated harmful factors

Solution Approach 1:

The system converts the harmful odd-order harmonics into useful frequency-selective mixing paths. By using multiple mixers with LO frequencies that are integer multiples of a base frequency, the harmonics that would normally be interference become the mixing signals for handling different frequency ranges

Inventive Principle:

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

Solution Approach 2:

Multiple mixers are configured to perform multiple functions: each mixer handles a specific frequency range and simultaneously suppresses interference signals at corresponding harmonic frequencies. The system achieves both frequency conversion and interference suppression in a unified multi-functional architecture

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Object-affected harmful factors

If RF tracking filters are used to eliminate interference signals, then interference suppression is improved, but the circuit area and power consumption increase

Engineering Contradiction:

Improveinterference signal suppressionVSAvoidcircuit area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

The system replaces the mechanical/filter-based interference suppression approach with a signal-processing-based approach using multiple mixers. Instead of using physical filters to block interference frequencies, the system uses frequency conversion and selective mixing to suppress interference in the digital/baseband domain

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach allows for precise suppression of interference signals without the need for power-hungry RF tracking filters, reducing circuit area and power consumption, and maintaining efficient frequency conversion across varying LO frequencies.

Implementation Method 1

a mixer that multiplies a received signal that has been band-limited in a usable bandwidth of said receiver by the LO signal so as to convert the frequency of the received signal

Methodology Applied

Scientific EffectFrequency conversion through mixing: Heterodyne

Data Source

PatentUS8818317B2Frequency converter and receiver that uses the frequency converter

Publication Date: 2014.08.26 NEC CORP

AI summary

The present invention is applied to a frequency converter used for a receiver. The frequency converter according to the present invention includes an LO signal generator (11) that generates an LO signal and outputs the LO signal; and a mixer (10) that multiplies a received signal that has been band-limited in a usable bandwidth of said receiver by the LO signal so as to convert the frequency of the received signal and outputs the resultant signal, wherein said LO signal generator is capable of varying a phase resolution, and said frequency converter is capable of varying a signal gain for each phase value of the LO signal.