Crystal-Less Reference Clock Circuit for Wireless LO Generation

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Solution Overview

Problem

Wireless system chips rely on off-chip crystal oscillators for local oscillator signals, increasing BOM costs and PCB area, as they require an external electromechanical resonator for reference clock generation.

Innovation Solution

Integration of an active oscillator without an electromechanical resonator on the chip, generating a reference clock used for local oscillator signals in both transmit and receive processes, eliminating the need for an off-chip oscillator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an off-chip crystal oscillator is used to generate the reference clock, then the stability and accuracy of the local oscillator signal is improved, but the BOM cost and PCB area increase

Engineering Contradiction:

Improvestability and accuracy of local oscillator signalVSAvoidPCB area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent integrates the reference clock generation function directly into the wireless system chip by incorporating an active oscillator circuit on-chip. This merging of the off-chip crystal oscillator functionality with the chip reduces PCB area by eliminating the external component while maintaining the necessary signal generation capability through on-chip active components and routing.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If an off-chip crystal oscillator is used to generate the reference clock, then the stability and accuracy of the local oscillator signal is improved, but the BOM cost increases

Engineering Contradiction:

Improvestability and accuracy of local oscillator signalVSAvoidBOM cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent merges the reference clock generation function into the wireless system chip by implementing an on-chip active oscillator. This integration eliminates the need for a separate off-chip crystal oscillator component, thereby reducing the bill of materials cost while providing the necessary reference clock signal for local oscillator generation.

Inventive Principle:

Principle #5Merging (Combining)

3Area of stationary object

If an active oscillator without electromechanical resonator is used on-chip, then the BOM cost and PCB area are reduced, but the stability and accuracy of the reference clock may be compromised

Engineering Contradiction:

ImprovePCB areaVSAvoidstability and accuracy of reference clock

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The patent replaces the electromechanical resonator (crystal) with an active oscillator circuit implemented using electronic components on-chip. This substitution eliminates the need for mechanical resonance elements while generating the reference clock signal through electronic oscillation mechanisms, thereby reducing PCB area and BOM cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs parameter changes by adjusting the operating conditions and design parameters of the on-chip active oscillator to optimize its performance. By carefully selecting and tuning parameters such as transistor dimensions, bias currents, and feedback network values, the system achieves acceptable stability and accuracy without requiring an electromechanical resonator.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11677433B2Wireless system having local oscillator signal derived from reference clock output of active oscillator that has no electromechanical resonator

Publication Date: 2023.06.13 MEDIATEK INC

AI summary

A wireless system includes an active oscillator and a front-end circuit. The active oscillator is used to generate and output a reference clock. The active oscillator includes at least one active component, and does not include an electromechanical resonator. The front-end circuit is used to process a transmit (TX) signal or a receive (RX) signal according to a local oscillator (LO) signal. The LO signal is derived from the reference clock.