Waveform Synthesizer Jitter Insertion for Baud Rate Test Signals
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Solution Overview
Problem
Conventional test and measurement instruments lack the necessary baud rate range and flexible impairment generation capabilities to effectively simulate jitter and other timing-related impairments as required by various communication standards, limiting their ability to accurately test devices under test (DUT) for performance margins.
Innovation Solution
The implementation of a waveform synthesizer that uses digital signal processing (DSP) or analog means to add impairments like jitter and spread spectrum clocking to the desired data waveform, utilizing a field programmable gate array (FPGA) or Application Specific Integrated Circuits (ASICs) to modulate the signal source DAC sample clock in real-time, allowing for flexible impairment generation and simulation of various impairment types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional test and measurement instruments are used, then device simplicity is maintained, but the baud rate range and impairment generation capabilities are insufficient
Solution Approach 1:
The waveform synthesizer is designed to generate multiple types of impairments (jitter, spread spectrum clocking, and other timing-related impairments) through a single integrated system. The impairment generator can produce various impairment types by modifying the DAC sample clock, eliminating the need for multiple separate instruments and enhancing adaptability across different communication standards.
Solution Approach 2:
The system employs dynamic clock modulation where the DAC sample clock is adjusted in real-time to introduce timing impairments. The symbol transition edges are advanced or delayed dynamically based on the desired impairment type, allowing flexible simulation of different jitter conditions without requiring fixed, dedicated hardware for each impairment type.
2Measurement precision
If the DAC sample clock is modulated in real-time to add impairments, then impairment simulation accuracy is improved, but the system complexity increases
Solution Approach 1:
The impairment generator acts as an intermediary component that sits between the waveform synthesizer and the DAC. It processes the desired data waveform and introduces timing impairments by modulating the DAC sample clock before the signal reaches the DAC. This intermediary approach allows precise impairment injection without requiring complex modifications to the core DAC or waveform synthesizer architecture.
Solution Approach 2:
The system replaces traditional mechanical or hardware-based impairment injection methods with digital signal processing. By using DSP techniques to modulate the DAC sample clock and advance or delay symbol transition edges, the system achieves precise impairment simulation through software-controlled timing adjustments rather than physical hardware modifications.
3Adaptability or versatility
If multiple communication standards are supported, then versatility is improved, but the baud rate range requirements increase
Solution Approach 1:
The waveform synthesizer enables baud rate and impairment parameter changes through software configuration. By dynamically adjusting the DAC sample clock frequency and the timing offsets introduced by the impairment generator, the system can adapt to different communication standards and their specific baud rate requirements without requiring multiple fixed-frequency oscillators or hardware configurations.
Data Source
AI summary
A test and measurement device having a signal source, including an impairment generator configured to output an impairment and a waveform synthesizer. The waveform synthesizer receives an input digital signal to be synthesized, receives the impairment, and synthesizes a synthesized digital signal based on the input digital signal and the impairment. The test and measurement instrument also includes a fixed sample rate digital-to-analog converter configured to receive a clock signal and the synthesized digital signal and output an analog signal.