Digital PWM Signal Generation for Low-Aliasing RF Output
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Solution Overview
Problem
The generation of high dynamic range pulse-width modulated signals is challenging due to jitter and inaccuracies in edge transitions, leading to increased noise and decreased dynamic range, especially when upconverted to RF frequencies, causing aliasing and adjacent band interference.
Innovation Solution
A method of generating pulse-width modulated signals by calculating a finite number of basis functions, such as Fourier harmonics, to create a band-limited signal that prevents aliasing and reduces out-of-band noise, implemented in a digital domain using a digital pulse-width modulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional PWM generation methods are used, then the system achieves high efficiency through switching operation, but jitter and inaccuracies in edge transitions lead to increased noise and decreased dynamic range
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing pulse width values in a lookup table before they are needed for PWM generation. The duty cycle values are computed in advance based on the input signal characteristics, and these pre-computed values are then used during the switching operation. This eliminates the need for real-time edge transition calculations, thereby reducing jitter and improving dynamic range while maintaining the efficiency benefits of switching operation.
2Speed
If the PWM signal is upconverted to RF frequency, then the system achieves wider bandwidth application, but aliasing and adjacent band interference increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing pulse width values in a lookup table before they are needed for PWM generation. The duty cycle values are computed in advance based on the input signal characteristics, and these pre-computed values are then used during the switching operation. This eliminates the need for real-time edge transition calculations, thereby reducing jitter and improving dynamic range while maintaining the efficiency benefits of switching operation.
Solution Approach 2:
The patent uses a lookup table that stores pre-computed duty cycle values, essentially creating a copy of the required PWM parameters in advance. This lookup table serves as a reference that can be quickly accessed during signal generation, avoiding the need for complex real-time calculations and reducing the generation of spurious signals and interference.
3Object-generated harmful factors
If high order filtering is used to attenuate aliasing and out of band noise, then adjacent band interference is reduced, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing pulse width values in a lookup table before they are needed for PWM generation. The duty cycle values are computed in advance based on the input signal characteristics, and these pre-computed values are then used during the switching operation. This eliminates the need for real-time edge transition calculations, thereby reducing jitter and improving dynamic range while maintaining the efficiency benefits of switching operation.
Solution Approach 2:
The patent uses a lookup table that stores pre-computed duty cycle values, essentially creating a copy of the required PWM parameters in advance. This lookup table serves as a reference that can be quickly accessed during signal generation, avoiding the need for complex real-time calculations and reducing the generation of spurious signals and interference.
Data Source
AI summary
In an embodiment, a method of generating a pulse-width modulated signal from an input signal includes calculating a finite number of basis functions of a first pulse-width modulated signal based on the input signal, and forming an electronic output based on the calculated finite number of basis functions.