Signal-integrity (SI) issues were once a concern of digital circuit designers rather than RF/microwave engineers. But the divide between the two groups has narrowed to a relatively thin line in recent years, prompting software developers to address device and circuit models within an environment suited for SI analysis. One of these developers, Applied Wave Research (El Segundo, CA), now offers a solution

for engineers faced with SI issues: the company's AWR SI 2005 design suite is a cross-domain SI solution developed for designing and analyzing high-speed, high-frequency circuits. The suite of software tools allows engineers to analyze and modify SI problems early in the design cycle to speed time to market.

As analog and digital integrated circuits (ICs) grow in complexity and total number of gates, the potential for signal-routing problems increases almost exponentially. Second-order physical causes can lead to signal problems in analog, mixed-signal, or digital ICs, which can be described as SI problems or design integrity problems. The SI problems are usually manifested as timing problems, while design integrity issues involve device reliability, such as proper grounding paths, thermal dissipation, etc.

The AWR SI 2005 design suite combines the AWR Design Environment and unified data models with an SI analysis environment to create a unified, easy-to-use platform (see figure). The design suite supports multiple process technologies, and allows SI analysis of complex interconnections within and between chips, between chips and packages, between modules, and on printed-circuit boards (PCBs). SI analysis allows checking for crosstalk between circuit traces, intersymbol interference (ISI) in digital and mixed-signal circuits, and the effects of data-dependent jitter on timing in high-speed circuits.

The SI analysis capability can be applied to a host of design and simulation scenarios, including the study of coupled lines, evaluation of electromagnetic (EM) fields radiating into free space, analysis of dielectric losses, three-dimensional modeling of plated through holes in ICs, and investigation of the effects of losses due to metal skin effects. Most metal skin-effect models assume that the metal has infinite thickness with losses that are constant with frequency. An accurate SI analysis tool such as the AWR SI 2005 Design Suite can model device metal layers with finite thickness, calculating metal resistance as a function of frequency. The AWR SI 2005 Design Suite can also accurately model dielectric losses. Conventional tools assume constant relative permittivity for a dielectric loss model, with constant loss tangent. The AWR SI 2005 Design Suite features dielectric models with loss tangent and permittivity that vary as functions of frequency.

The AWR SI 2005 tools provide comprehensive SI analysis capabilities on top of the company's Analog Office Intelligent Net™ (iNet) technology. The iNet technology, which is based on accurate interconnection and RF/microwave modeling methodologies in order to speed and simplify the design process, supports model extraction on complex cross-domain interconnections. The AWR SI 2005 suite also includes support for multiple EM simulation and analysis tools (through its AWR EM Socket™ open interface), as well as a wide variety of modeling formats such as SPICE netlist, IBIS models, and S-parameter blocks. The company's harmonic balance simulator is integrated with HSPICE from Synopsys to provide fast, high-capacity simulations from a single, physically accurate schematic framework, with modeling capability to 20 GHz and beyond.

At a time when more device and module solutions include mixed-signal formats, tools such as the AWR SI 2005 design suite become essential for accurately modeling the second-order effects of layouts, interconnections, and packages on ultimate performance. In contrast to separate design and analysis solutions, the AWR SI 2005 brings all design domains into a single platform, allowing easy movement and design/analysis flow between ICs, modules, packages, and PCBs. It allows designers to examine such disparate technologies as GaAs and silicon ICs, multilayer PCBs, and low-temperature-cofired-ceramic (LTCC) modules within a common environment. The software can generate a wide range of result formats, including S-parameter data, bit-error-rate (BER) plots, eye diagrams, error-vector-magnitude (EVM) plots, adjacent-channel-power-ratio (ACPR) plots, and in-phase/quadrature (I/Q) scatter plots.

The AWR SI 2005 design suite is available as a stand-alone product for new users or as an upgrade to existing Analog Office™ and Microwave Office®‚ design users. It is available for Linux and Windows XP operating systems on the personal computer. P&A: $15,750 and up; stock. Applied Wave Research, Inc., 1960 East Grand Ave., Suite 430, El Segundo, CA 90245; (310) 726-3000, FAX: (310) 726-3005, e-mail: info@mwoffice.com, Internet: www.mwoffice.com.