Local Oscillator Frequency Calibration for Crystal-Less Wireless Chips
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless system chips require an off-chip crystal oscillator, increasing BOM cost and PCB area, and face challenges in achieving accurate frequency calibration to comply with ETSI and FCC spectrum emission regulations due to the instability of reference clocks generated from on-chip active oscillators.
Innovation Solution
A crystal-less wireless system design that uses an active oscillator to generate a local oscillator signal, integrated with a calibration circuit to detect a calibration tone within the receiver bandwidth and adjust the LO frequency, thereby implementing a low-cost frequency calibration scheme to ensure compliance with regulatory standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an off-chip crystal oscillator is used to generate the reference clock, then the frequency accuracy and stability are improved, but the BOM cost and PCB area increase
Solution Approach 1:
The patent extracts the oscillator function from an external off-chip component and integrates it into an on-chip active oscillator. This eliminates the need for external crystal oscillators, reducing PCB area and BOM cost while maintaining frequency accuracy through integrated calibration mechanisms.
Solution Approach 2:
The patent combines the reference clock generation and frequency calibration functions into a single integrated on-chip active oscillator. This merging of functions eliminates the need for separate external components while achieving both area reduction and frequency accuracy through unified design.
2Area of stationary object
If an on-chip active oscillator is used to generate the reference clock, then the BOM cost and PCB area are reduced, but the frequency accuracy and stability deteriorate
Solution Approach 1:
The patent implements a feedback-based frequency calibration mechanism where the receiver detects calibration tones and generates control signals to adjust the active oscillator frequency. This closed-loop feedback system compensates for the inherent frequency inaccuracies of on-chip oscillators, achieving regulatory compliance without external components.
Solution Approach 2:
The patent dynamically adjusts the operating parameters of the active oscillator through frequency calibration. By changing the oscillator frequency based on detected calibration tones and control signals, the system achieves accurate frequency alignment despite the initial limitations of on-chip oscillation.
3Measurement precision
If frequency calibration is implemented to comply with ETSI and FCC regulations, then the spectral emission accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent implements a self-calibrating frequency control mechanism where the receiver uses its own calibration tone detection capability to generate frequency correction signals. This self-service approach eliminates the need for external calibration equipment or complex external frequency control circuits, achieving regulatory compliance through integrated self-calibration.
Data Source
AI summary
A system includes a local oscillator (LO) signal generation circuit, a receiver (RX) circuit, and a calibration circuit. The LO signal generation circuit generates an LO signal according to a reference clock, and includes an active oscillator that generates the reference clock. The active oscillator includes at least one active component. The RX circuit generates a processed RX signal by processing an RX input signal according to the LO signal. The calibration circuit checks a signal characteristic of the processed RX signal by detecting if a calibration tone exists within a receiver bandwidth, set a frequency calibration control output in response to the calibration tone being not found in the receiver bandwidth, and output the frequency calibration control output to the LO signal generation circuit. The LO signal generation circuit adjusts an LO frequency of the LO signal in response to the frequency calibration control output.