Reference Clock Noise Pedestal Generation for Signal Sources
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing signal sources struggle to generate tunable noise pedestals without consuming processing resources or requiring complex algorithms, and they fail to scale phase noise ideally, especially in direct digital synthesizer (DDS) and phase locked loop (PLL) synthesizer-based systems, which are crucial for compliance and performance testing.
Innovation Solution
A reference system with a noise pedestal generator is integrated into the reference clock of the signal generator, allowing for the direct formation of tunable noise pedestals in the clock signal, which is then reflected in the output, without consuming processing resources or using complex algorithms, and scales ideally with frequency adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If noise pedestal is generated using internal modulation capability of DDS signal source, then phase noise can be introduced, but computing and processing resources are consumed and external frequency modulation capabilities must be disabled
Solution Approach 1:
The noise pedestal generation function is extracted from the DDS signal source and implemented as a separate reference system with dedicated noise pedestal generator circuitry. This separation removes the burden of computing and processing resources from the main signal source while preserving external frequency modulation capabilities.
Solution Approach 2:
A reference system with a noise pedestal generator serves as an intermediary between the clock source and the DDS signal source. This intermediary adds the desired noise pedestal to the clock signal without requiring the DDS signal source to perform complex modulation operations.
2Reliability
If noise is added to the signal generation engine output, then phase noise can be generated, but the solution does not scale ideally with frequency and requires complex algorithms
Solution Approach 1:
The noise pedestal is generated in advance in the reference system before the signal reaches the DDS signal source. By pre-generating the noise pedestal at the reference clock level, the system avoids the need for complex real-time algorithms to scale noise with frequency changes.
Solution Approach 2:
The noise pedestal characteristics are copied from the reference clock signal to the final output signal through the frequency multiplication process. This natural copying mechanism ensures ideal scaling behavior without requiring additional complex algorithms.
3Reliability
If DDS signal source is used, then noise pedestal is absent which improves overall performance, but customers cannot obtain pedestals for testing and comparison purposes
Solution Approach 1:
The reference system dynamically adjusts the noise pedestal level through a variable gain amplifier controlled by a control signal. This allows the system to adapt between different noise pedestal levels (including zero) based on customer requirements, providing versatility while maintaining signal purity when needed.
Solution Approach 2:
The noise pedestal characteristics are controlled by changing parameters such as the gain of the variable gain amplifier and the attenuation level. This allows flexible adjustment of noise pedestal presence and magnitude to match different testing and comparison requirements.
Data Source
AI summary
A reference system is provided for generating a clock signal with a tunable noise pedestal for driving a signal generator. The reference system includes a reference source configured to generate a reference signal and a multiplier chain, including a noise pedestal generator. The noise pedestal generator includes a noise pedestal attenuator configured to attenuate the reference signal to degrade a noise floor of the reference signal, a VGA configured to adjust the attenuated reference signal to a desired signal level, a bandpass filter configured to filter out excess noise from the adjusted reference signal to form a noise pedestal, and a switch arrangement configured to selectively input the reference signal to a first path including the noise pedestal attenuator and the VGA, and a second path bypassing the noise pedestal attenuator and the VGA. The clock signal includes the noise pedestal when the first path is selected.