8 Ways ADS 2016 Overcomes Signal and Power Integrity Challenges

Keysight Technologies

10 Ways ADS Overcomes Signal and Power Integrity Challenges

Technical Overview

1. ADS provides speed and accuracy for your SI EM characterization

Electromagnetic (EM) technologies are typically used to accurately characterize loss and coupling of high speed channels. As data rates increase, a major dilemma is the choice of which EM technology to use. Full-wave general purpose EM simulation tools offer the desired accuracy at high-frequencies. The limiting factor of 3D-EM technology for SI analysis is simply the scale and complexity of PCB designs. Densely-routed boards require hours of engineering time to manually simplify a layout, cookie-cut the signal nets, and optimize the meshing to achieve accurate results in a practical time (many hours of simulation). Designers can only verify small sections of the board at one time.

Hybrid simulators are much faster by comparison, and can be used for greater coverage of the nets on the boards; however, there is always the question of whether or not the simulation correlates well with measurement. Moreover, what EM effects were missed by using the simplified techniques?

ADS introduces two EM analysis solutions—SIPro and PIPro—that are specifically designed to overcome these challenges. SIPro focuses on enabling SI EM analysis of high-speed links on large, complex high-speed PCBs, while PIPro is used for PI EM analysis of power distribution networks (PDNs), including DC IR drop analysis, AC PDN impedance analysis and power plane resonance analysis.

In particular, SIPro utilizes a composite EM technology to deliver pure-EM analysis with higher capacity than general purpose EM solutions. It captures all relevant EM effects, such as via-via coupling, via to microstrip transitions, and signal to ground/power plane coupling. From the net-driven user interface—a feature common to both the SIPro and PIPro suite of EM simulators—designers can quickly select only those nets they want to simulate, together with the power and ground planes and components, and with no time or engineering effort required to manually edit or manipulate layout objects before simulation. Ports can also be automatically setup. With this workflow, designers can go from layout to results in less than 20 clicks.

When the EM simulation is finished, designers can quickly plot the S-parameters (Single-Ended and Mixed-Mode), TDR/TDT and crosstalk. Doing so enables them to quickly assess whether or not the EM model is sufficiently characterized and if the channel performs as expected. With a single-click, automatic schematic generation back-annotates the EM model to an ADS schematic, making it ready for use in transient and channel simulations, in one easy flow. With such capabilities, SIPro delivers both the speed and accuracy today’s designers need, enabling a more productive workflow.

2. ADS simplifies the use of S-parameter files for your parts

Imagine you’ve just downloaded an S-parameter file for a part you are considering; in this case, a high-speed connector for a backplane. It has a large number of ports, so you want to first inspect the quality of the data and then use it in your simulation. How do you wire it up in the schematic? Which ports are paired?

Traditionally, the answer might be to open up the data in a text editor. However, with ADS’s S-Parameter Checker, designers can now easily view the contents of any S-parameter file without having to setup an S-parameter test bench simulation. This allows them to directly plot the individual relations they wish to see, and shows them the port names against each pin. It also tells designers if the file is passive or reciprocal, as well as the number of data points in the file and the frequency range it covers. Designers can even use S-Parameter Checker to rename, re-order and reduce the number of ports, which enables them to save a new, more usable S-parameter file.

In addition to the S-Parameter Checker, using S-parameter files in ADS simulations is now even easier with recent updates. The new SnP component reads port names from the file directly onto the symbol. Designers are free to choose the orientation of pins so that all inputs are on one side and all outputs are on the other. As a result, there is no more crossing of wires. After this, all that’s left for the designer to do is View, Edit, Place, Sim, Plot, and Done.

3. ADS provides access to industry-leading channel simulator technology

New disruptive technologies spring forth from tough technical challenges. That’s certainly the case for ADS’s Channel Simulation. This technology first became prevalent when transient simulation (SPICE) couldn’t address the measurement of margin-to-mask for really low bit-error-rates (BER), as demanded by high-speed link designs.

Before Channel Simulation, transient simulation was the predominant approach used to simulate a high-speed link design. However, designers were struggling with a tough technical challenge: What margin do I have at a BER of 1e-9, 1e-12, or 1e-16? These questions are outside the capability of transient simulation alone, because the sheer number of time steps required is beyond practical means. Computing BER contours with Channel Simulation arose as a way to answer this challenge.

The underpinnings of ADS’ technical leadership in Channel Simulation began with Dr. Fangyi Rao’s 2006 patent to correct for passivity, while ensuring causality, in bandlimited frequency-domain models. Dr. Rao work ensured ADS was regarded as the most accurate solution for handling cascades of S-parameter models combined with circuit models in one schematic. Following the patent’s issuance, further innovation into Channel Simulation continued at a swift pace:

• In 2009, Bit-by-Bit Channel Simulation was released.
• In 2010, Statistical Channel Simulation was released.
• In 2011, IBIS-AMI support for Channel Simulation was introduced.
• In 2012, an IEEE paper was published on the rigorous handling of Tx Jitter mechanisms (e.g., jitter amplification caused by lossy channels), with Dr. Rao as the author.