PLL Transmitter Calibration for Multi-Band Frequency Accuracy
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Solution Overview
Problem
The loop bandwidth of phase-locked loop circuits is sensitive to their transfer function, making it challenging to generate different frequency bands effectively in multi-band systems, as conventional techniques have limitations in calibrating compensation filters according to the output frequency of controllable oscillators.
Innovation Solution
A phase-locked loop based transmitter with an open loop modulation compensation scheme that calibrates a compensation filter according to the output frequency of a controllable oscillator, utilizing a phase/frequency detector, control signal generator, voltage controlled oscillator, divider, control unit, detecting device, filtering device, and modulating device to adjust and calibrate the synthesized signal and filtering process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional phase-locked loop circuits are used to generate different frequency bands, then the basic frequency synthesis function is achieved, but the loop bandwidth becomes sensitive to transfer function variations making it difficult to accurately generate different frequency bands
Solution Approach 1:
The patent applies preliminary action by calibrating the compensation filter before normal operation. A calibration mode is implemented where the phase-locked loop device determines calibration data based on its actual transfer function response, stores this calibration data, and then uses it during normal operation to compensate for transfer function variations. This preliminary calibration action resolves the contradiction by pre-adjusting the system to account for frequency band-specific characteristics.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the compensation filter parameters based on the determined frequency band and stored calibration data. When a frequency band changes, the system retrieves corresponding calibration data and modifies the compensation filter's transfer function parameters to match the optimal settings for that specific frequency band, thereby maintaining loop bandwidth accuracy across different operating conditions.
2Adaptability or versatility
If the phase-locked loop circuit is designed with fixed compensation filter parameters, then the circuit structure remains simple, but it cannot adapt to different frequency bands with varying transfer function characteristics
Solution Approach 1:
The patent applies dynamics by transforming the static compensation filter into a dynamic, adaptive component. The system includes a calibration mode that determines actual transfer function characteristics, stores calibration data for different frequency bands, and dynamically adjusts compensation filter parameters based on the currently active frequency band. This dynamic adaptation enables the fixed physical structure to achieve variable performance characteristics across different operating conditions.
Solution Approach 2:
The patent uses preliminary action by pre-calibrating the compensation filter for each frequency band during a calibration phase. The calibration data, which represents optimal compensation parameters for each frequency band, is stored in advance and then retrieved during normal operation. This preliminary calibration action eliminates the need for complex real-time adjustments while maintaining adaptability across frequency bands.
3Measurement precision
If calibration is performed for each frequency band, then accurate loop bandwidth control is achieved, but the calibration process time increases
Solution Approach 1:
The patent resolves this contradiction by performing calibration in advance during a dedicated calibration mode before normal operation begins. The system determines calibration data for all frequency bands in advance, stores this calibration data in memory, and then quickly retrieves the appropriate calibration data when switching frequency bands during normal operation. This preliminary calibration action eliminates repeated calibration time while maintaining accuracy.
Solution Approach 2:
The patent applies copying by creating and storing calibration data copies for different frequency bands during calibration mode. Instead of performing time-consuming calibration measurements each time a frequency band changes, the system creates calibration data representations during an initial calibration phase and stores these copies for rapid retrieval during normal operation, significantly reducing calibration time while maintaining measurement precision.
Data Source
AI summary
A signal generating apparatus is disclosed for generating a synthesized signal according to an input signal, the signal generating apparatus includes a phase-locked loop device for generating the synthesized signal; a control unit for controlling the control signal generator to adjust the control signal in a calibration mode to thereby adjust a frequency of the synthesized signal, wherein the phase/frequency detector does not output the detected signal to the control signal generator in the calibration mode; a detecting device for detecting the synthesized signal to generate a calibrating signal in the calibration mode; a filtering device for filtering the input signal and calibrating the input signal according to the calibrating signal to generate a filtered signal; and a modulating device for modulating the filtered signal to generate the dividing factor.