On-Chip Active Oscillator Reference Clock for Crystal-Free Wireless LO
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Solution Overview
Problem
Existing wireless systems rely on off-chip crystal oscillators, increasing BOM cost and PCB area, which can be reduced by using a local oscillator signal derived from an active oscillator without an electromechanical resonator.
Innovation Solution
Integrate an active oscillator without an electromechanical resonator into the wireless system chip, generating a reference clock for on-chip components, eliminating the need for off-chip oscillators and reducing BOM cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an off-chip crystal oscillator is used to generate the reference clock, then the wireless system achieves stable frequency reference, but the BOM cost and PCB area increase
Solution Approach 1:
The patent merges the oscillator function into the wireless system chip by integrating a phase-locked loop (PLL) circuit that generates the reference clock internally. This eliminates the need for a separate off-chip crystal oscillator, thereby reducing PCB area while maintaining frequency reference stability through the PLL's feedback control mechanism.
Solution Approach 2:
The integrated PLL circuit serves multiple functions: it generates the reference clock for frequency synthesis, provides timing signals for digital circuits, and enables frequency multiplication. This multi-functionality replaces the dedicated off-chip oscillator, reducing component count and PCB area while maintaining system reliability.
2Reliability
If an off-chip crystal oscillator is used to generate the reference clock, then the wireless system achieves stable frequency reference, but the BOM cost increases
Solution Approach 1:
The patent combines the oscillator functionality within the wireless system chip using an integrated PLL circuit. This eliminates the need to purchase and assemble a separate off-chip crystal oscillator, directly reducing BOM cost while maintaining frequency reference stability through the PLL's feedback control.
Solution Approach 2:
The wireless system chip becomes self-sufficient by generating its own reference clock through the integrated PLL circuit. This self-service capability eliminates dependence on external oscillators, reducing both BOM cost and assembly complexity while maintaining reliable frequency reference.
3Area of stationary object
If an active oscillator without electromechanical resonator is used, then the PCB area and BOM cost are reduced, but the frequency stability challenge arises
Solution Approach 1:
The patent employs a phase-locked loop (PLL) circuit with feedback control to generate the reference clock. The PLL continuously monitors and adjusts the output frequency based on feedback from a divider circuit, ensuring frequency stability without requiring an electromechanical resonator. This feedback mechanism compensates for frequency drift and maintains reliable operation.
Solution Approach 2:
The patent replaces the mechanical electromechanical resonator (crystal) with an electronic PLL-based frequency synthesis system. This substitution eliminates the need for physical resonators while achieving comparable or superior frequency stability through electronic feedback control, thereby reducing PCB area and BOM cost.
Data Source
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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.