Understanding Timing Analysis in High-Speed Signal Integrity

Timing analysis in the context of channel simulation using the ADS (Advanced Design System) tool focuses on analyzing the signal integrity (SI) and ensuring proper timing for data transmission. Here’s a step-by-step guide to performing timing analysis in ADS channel simulations:

1. Setup the Channel Simulation

• Define the Channel: Include the transmission line models, connectors, vias, and other passive components representing the channel.
• Driver and Receiver Models: Use IBIS models for drivers and receivers. Include a proper termination scheme as per the design.
• Simulation Mode: Choose either Time Domain Simulation or Statistical Simulation based on your requirements.

2. Configure the Simulation

• Open the Channel Simulator in ADS.
• Set up the following key parameters: Bit Rate: Specify the data rate for the channel. Encoding Scheme: Set the coding method if applicable (e.g., NRZ, PAM4). Stimulus: Configure pseudo-random bit sequences (PRBS) or specific test patterns. Number of Bits: Define the length of the simulation.
• Select the appropriate analysis: Time Domain Eye Diagram Analysis BER (Bit Error Rate) Analysis Impulse/Step Response Analysis

3. Perform Timing Measurements

Timing analysis involves the extraction of metrics such as eye diagram parameters, jitter, and skew.

• Eye Diagram Analysis: Plot the eye diagram to visualize timing margins and voltage levels. Key measurements: Eye Height: Determines vertical signal integrity. Eye Width: Measures the available timing margin. Jitter: Analyze total jitter (TJ), random jitter (RJ), and deterministic jitter (DJ).
• BER Contours: Evaluate the BER contours to ensure compliance with system specifications.
• Timing Margin: Check the available timing margin against the setup and hold requirements of the receiver.

4. Analyze Crosstalk and Skew

• Crosstalk (both NEXT and FEXT) can degrade timing margins.
• Measure skew between differential pairs to ensure synchronization.

5. Channel Compliance Analysis

• Compare simulation results with industry standards (e.g., PCIe, USB, Ethernet).
• Validate whether the timing and SI metrics meet the required specifications.

6. Post-Simulation Reporting

• Export the results to generate a comprehensive report, including: Timing metrics Eye diagram plots BER analysis data
• Use ADS's built-in tools for generating compliance summaries.

7. Optimization

• Based on the results: Optimize equalization (Tx and Rx equalizers such as FFE, DFE). Adjust termination schemes. Tune channel components to improve timing margins.

By following these steps, you can perform effective timing analysis for channel simulation in ADS, ensuring reliable high-speed digital communication.