Phase-Coherent NCO Circuit for Dynamic Frequency Switching

Solution Overview

Problem

Current digital local oscillator (LO) implementations in wireless transceivers face challenges in maintaining phase coherency when switching between frequencies, leading to increased circuit area and power consumption, as well as the inability to change frequencies dynamically while operating.

Innovation Solution

A phase coherent numerically controlled oscillator (NCO) circuit that includes a base frequency NCO, a phase seeding circuit, and a scaled frequency NCO, which generates phase values by computing a seed phase value based on the base phase and a scale factor, allowing for efficient switching between frequencies while minimizing power consumption and circuit area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional digital LO implementations are used to switch between frequencies, then frequency switching capability is achieved, but phase coherency is lost and circuit area increases

Engineering Contradiction:

Improvefrequency switching capabilityVSAvoidcircuit area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The NCO circuit is segmented into a base frequency NCO and a scaled frequency NCO, where the base frequency NCO generates a base phase sequence and the scaled frequency NCO generates the actual oscillator phase sequence by scaling the base phase. This segmentation allows frequency switching through parameter changes rather than physical circuit reconfiguration, reducing circuit area while maintaining phase coherency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The base frequency NCO serves multiple functions: it generates the base phase sequence that is used for both direct output and as input to the scaled frequency NCO. This multi-functionality eliminates the need for separate oscillators for different frequencies, reducing overall circuit area while maintaining the ability to switch frequencies with phase coherency.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If traditional digital LO implementations are used to switch between frequencies, then frequency switching capability is achieved, but power consumption increases

Engineering Contradiction:

Improvefrequency switching capabilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by stationary object

Solution Approach 1:

The NCO circuit is segmented into a base frequency NCO and a scaled frequency NCO, where the base frequency NCO generates a base phase sequence and the scaled frequency NCO generates the actual oscillator phase sequence by scaling the base phase. This segmentation allows frequency switching through parameter changes rather than physical circuit reconfiguration, reducing circuit area while maintaining phase coherency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The base frequency NCO serves multiple functions: it generates the base phase sequence that is used for both direct output and as input to the scaled frequency NCO. This multi-functionality eliminates the need for separate oscillators for different frequencies, reducing overall circuit area while maintaining the ability to switch frequencies with phase coherency.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If frequencies are changed dynamically during operation, then adaptability is improved, but phase coherency cannot be maintained

Engineering Contradiction:

Improvedynamic frequency changing capabilityVSAvoidphase coherency

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The base phase sequence acts as an intermediary between the base frequency NCO and the scaled frequency NCO. When switching frequencies dynamically, the scaled frequency NCO continues to derive its phase from the base phase sequence through scaling, ensuring that phase coherency is maintained even as the output frequency changes. This intermediary relationship allows seamless frequency transitions without phase discontinuities.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11418148B2Phase coherent numerically controlled oscillator

Publication Date: 2022.08.16 TEXAS INSTRUMENTS INC

AI summary

A phase coherent NCO circuit includes a base frequency NCO, a phase seeding circuit, a scaled frequency NCO, a sine/cosine generator. The base frequency NCO is configured to generate base phase values based on a base frequency control word. The phase seeding circuit is coupled to the base frequency NCO. The phase seeding circuit is configured to generate a seed phase value based on the base phase values and a scale factor value. The scaled frequency NCO is coupled to the phase seeding circuit. The scaled frequency NCO is configured to generate oscillator phase values based on the phase seed value and an oscillator frequency control word. The sine/cosine generator is coupled to the scaled frequency NCO. The sine/cosine generator is configured to generate oscillator output samples based on the oscillator phase values.