Inductor-Less LO Buffer With Replica Bias for Low-Power Mixers

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Solution Overview

Problem

Personal Handy-Phone System (PHS) cellphone receivers face challenges with high power consumption in mixers and significant space requirements due to the use of inductors and coupling capacitors in local oscillator (LO) buffers.

Innovation Solution

An N-stage inductor-less local oscillator buffer is developed, comprising N−1 non-final stages and a final stage with a gain circuit, common-mode feedback circuit, and replica bias circuit, which reduces power consumption and minimizes footprint by eliminating inductors and coupling capacitors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If inductors and coupling capacitors are used in LO buffers, then signal buffering performance is improved, but die area is significantly increased

Engineering Contradiction:

Improvesignal buffering performanceVSAvoiddie area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent extracts and removes the inductor and coupling capacitor components from the LO buffer circuit, replacing them with an inductor-less topology that uses only resistors and transistors, thereby eliminating the primary sources of large die area consumption while maintaining signal buffering functionality

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent substitutes the traditional passive inductor-based buffering mechanism with an active transistor-based circuit implementation, replacing physical electromagnetic components with semiconductor device equivalents that achieve the same signal conditioning function with minimal area

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If inductors and coupling capacitors are used in LO buffers, then signal buffering performance is improved, but power consumption is increased

Engineering Contradiction:

Improvesignal buffering performanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent extracts and removes the power-hungry inductor and coupling capacitor components from the LO buffer circuit, replacing them with an inductor-less topology that uses only resistors and transistors, thereby eliminating the primary sources of large die area consumption while maintaining signal buffering functionality

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If mixer power budget is increased, then receiver performance is improved, but overall power consumption is increased

Engineering Contradiction:

Improvereceiver performanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements a common-mode feedback circuit that monitors and regulates the output signals, ensuring optimal mixer performance through feedback control while maintaining power efficiency by preventing excessive power dissipation in the mixer stage

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7482852B1Inductor-less local oscillator buffer

Publication Date: 2009.01.27 QUALCOMM INC

AI summary

An N-stage inductor-less local oscillator (LO) buffer can include N−1 non-final stages and a final stage. The final stage can includes a gain circuit, a common-mode feedback circuit connected to the gain circuit, and a replica bias circuit that provides a predetermined voltage to the common-mode feedback circuit. The inductor-less LO buffer can advantageously reduce a power budget for its downstream mixer as well as provide a compact footprint.