Super-Regenerative Oscillator Frequency Tuning for Drift Control
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Solution Overview
Problem
Super regenerative receivers face challenges in maintaining frequency stability due to periodic quenching, leading to frequency drift and degradation in bit error rate (BER) performance, as existing phase locked loop (PLL) schemes fail to continuously control the oscillator frequency effectively.
Innovation Solution
A frequency tuning apparatus that includes a frequency tuner and a compensator, using mapping and offset tables to align the oscillation frequency of a super regenerative oscillator with the target frequency, compensating for capacitance and controlling the oscillator's capacitor to minimize frequency errors and drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phase locked loop (PLL) scheme is used to control oscillator frequency, then frequency control capability is improved, but frequency drift occurs due to leakage current at charge pump node during SRR operation
Solution Approach 1:
The patent extracts the frequency control function from the continuous PLL operation and implements it only during calibration mode. The PLL is turned off during actual SRR data reception, eliminating the source of leakage current while preserving frequency control capability when needed.
Solution Approach 2:
The patent performs frequency calibration and adjustment in advance during a calibration mode before actual data reception. The oscillator frequency is tuned and stored in a lookup table during calibration, so no continuous control is needed during operation, preventing frequency drift.
2Reliability
If PLL is turned off during SRR operation to avoid leakage current, then frequency stability is improved, but frequency drift occurs because PLL cannot continuously control oscillator frequency
Solution Approach 1:
Frequency calibration is performed in advance during calibration mode, and the calibrated values are stored in a lookup table. During actual operation, the pre-calibrated settings are used, eliminating the need for continuous PLL control while maintaining frequency accuracy.
Solution Approach 2:
The system uses itself to calibrate its own frequency characteristics during initialization. The oscillator is calibrated against known reference frequencies, and the calibration data is stored for self-correction during operation, eliminating the need for external continuous control.
3Measurement precision
If frequency calibration is performed before data reception, then initial frequency alignment is improved, but frequency offset occurs between calibration mode oscillation frequency and average resonant frequency during actual data reception
Solution Approach 1:
The patent measures the actual resonant frequency during calibration by detecting the oscillator's response at different frequencies. This feedback information is used to adjust the calibration settings and compensate for the difference between calibration mode and operational mode frequencies.
Solution Approach 2:
The patent adjusts calibration parameters based on the detected frequency offset. By measuring the actual resonant frequency during calibration and comparing it with the target frequency, the system modifies calibration values to account for mode-dependent frequency shifts.
4Measurement precision
If continuous frequency control is implemented during SRR operation, then frequency accuracy is improved, but power consumption increases and complexity increases
Solution Approach 1:
Instead of continuous frequency control, the patent implements periodic calibration only during initialization or when frequency changes are detected. The oscillator operates in quenching mode during data reception without continuous control, significantly reducing power consumption while maintaining adequate frequency accuracy.
Solution Approach 2:
The continuous frequency control function is extracted from the operational mode and confined to calibration mode only. This eliminates unnecessary power consumption during data reception while preserving frequency control capability when actually needed.
5Ease of operation
If existing PLL scheme is used with periodic quenching, then SRR operation is maintained, but frequency control becomes ineffective due to periodic variation of bias current
Solution Approach 1:
The patent separates frequency control operations from continuous SRR quenching operations. Frequency calibration is extracted and performed during dedicated calibration intervals when the oscillator is not in quenching mode, avoiding interference from periodic bias current variations.
Solution Approach 2:
Frequency calibration is performed in advance before SRR operation begins. The oscillator is tuned to the correct frequency while not undergoing periodic quenching, and this pre-established frequency setting is maintained during operation without requiring continuous adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively stabilizes the oscillation frequency, reducing frequency drift and improving the bit error rate (BER) performance by actively tuning and compensating for errors, ensuring accurate frequency alignment and reduced power consumption.
Implementation Method 1
The frequency tuner may include: a first tuning controller configured to coarsely tune the oscillation frequency of the oscillator based on a result of comparing the target information to the oscillation information; and a second tuning controller configured to finely tune the oscillation frequency of the oscillator
Implementation Method 2
The frequency compensator may be further configured to compensate for a capacitance of the oscillator based on a compensation signal extracted from the offset table in correspondence to the target frequency
Implementation Method 3
a super regenerative oscillator configured to oscillate in response to a received external signal
Data Source
AI summary
A frequency tuning apparatus includes: a frequency tuner configured to tune an oscillation frequency of an oscillator based on target information extracted from a mapping table in correspondence to a target frequency, and oscillation information collected from the oscillator; and a frequency compensator configured to compensate for a compensation error between the tuned oscillation frequency and the target frequency based on an offset table.