Digital-to-Time Converter Dithering for Spur Reduction
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Solution Overview
Problem
Digital-to-time converter (DTC) circuits in communication systems face issues with temporal periodicity, leading to spectral spurs that can impact standard compliance and performance, as existing noise shaping methods are not robust or predictable enough to effectively eliminate these spurs.
Innovation Solution
The introduction of dither signals with non-constant instantaneous frequency, such as sinusoidal or pseudo-random modulation, is added to the DTC processing path to break up periodicity, with the dither information being canceled at subsequent stages to disrupt and prevent the formation of spectral spurs, allowing for robust and predictable reduction or elimination of spurs in the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If noise shaping is used to dissipate spur energy, then spectral spurs are reduced, but the added noise violates amplitude limits and the solution is not robust or predictable
Solution Approach 1:
A dither signal is introduced as an intermediary element in the DTC processing path. This dither signal breaks the temporal periodicity that causes spurs without adding significant noise to the output, providing a robust and predictable solution for spur reduction
Solution Approach 2:
The dither signal modifies the instantaneous frequency parameter of the local oscillator signal in a controlled manner. By changing the frequency parameter dynamically according to a dither sequence, the periodicity causing spurs is broken while maintaining signal integrity
2Object-generated harmful factors
If dither signal is added to break periodicity, then spectral spurs are eliminated, but device complexity increases
Solution Approach 1:
The dither signal is extracted from the main signal path after serving its purpose of breaking periodicity. The dither is added at one point in the processing chain and removed at another, minimizing its impact on overall system complexity while maintaining its spur-reduction effectiveness
Data Source
AI summary
Apparatus and methods for disrupting or preventing periodicity in DTC circuits are provided. In an example, a communication circuit can include a digital-to-time converter (DTC) and a processing path coupled to the DTC. The DTC can be configured to receive reference information, modulation information and first dither information, and to provide a modulated signal using the reference information, the modulation information and the first dither information. The processing path can be configured to receive second dither information and to cancel the first dither information using the second dither information, wherein the DTC is configured to disrupt processing periodicity of the communication circuit using the first dither information.