PathWave Electro-Thermal (ETH) Simulation Suite

Introduction

The Keysight W3050E, W3051E and W3059E is a suite of electro-thermal (ETH) simulation tools that integrates with the transient and steady-state circuit simulators in ADS to deliver the highest accuracy in circuit simulation.

It accounts for layout-dependent localized steady-state and time-varying electro-thermal heating of circuit components that alters device characteristics, degrades RF/Microwave circuit performance, and reduces reliability. It replaces guesswork assumption of fixed ambient temperature settings for circuit simulation.

Based on the industry proven Keysight Heatwave simulation technology, the ADS ETH simulation suite enables accurate design of amplifiers and densely integrated RF modules that must handle not just steady state but also transient pulsed and modulated RF signals.

Transient ETH heating causes active impedance mismatch, Adjacent Channel Power Ratio (ACPR) and Error Vector Magnitude (EVM) degradation of digitally modulated RF signals. These critical ETH effects are not captured by traditional circuit simulations.

Applications of ADS electro-thermal (ETH) simulation for RF/Microwave circuit design

• Today’s RF/Microwave circuits often operate with not just steady state but pulsed and digitally modulated signals in densely integrated RF modules.

• The guesswork assumption of constant ambient temperature in regular circuit simulation does not account for the localized ETH temperatures of circuit components.

• Transient and time-varying ETH heating of the circuit components also causes transient variation in active device characteristics that must be considered during design to prevent costly failures after hardware deployment.

The following are examples of RF circuit and module applications optimized to meet performance and reliability specs under transient electro-thermal heating.

Power amplifiers under pulsed and modulated signals

• Power amplifiers operating under pulsed and modulated signals undergoes ETH time-varying changes in characteristics.

• Dynamic ETH heating degrades EVM and ACPR performance on digitally modulated signals

• Critical localized steady state or time varying ETH heating effects are not captured by regular circuit simulation, leading to costly hardware failure after field deployment.

RF module packaging ETH coupling

• Dense packaging in RF modules causes electro-thermal heating of neighboring devices are not analyzed in regular circuit simulations, resulting in off-target performance prediction.

• Localized steady state and time-varying electro-thermal heating causes active impedance shifts in devices and degradation of modulated signal specs such as EVM and ACLR.

• Dynamic ETH model generation and reuse result in 10x to 100x speedup of electro-thermal circuit simulation to enable thorough design exploration of layout-dependent transient ETH effects before making tedious layout changes.

Active impedance match at peak transient temperature for reliability

• Amplifier dissipated power depends on selected load termination, but localized layout-dependent electro-thermal heating alters device active impedance. Junction temperature is device-layout dependent and therefore ETH load pull is needed to obtain accurate load termination to match to.

• In mission critical commercial, industrial, military and space applications where component failure cannot be tolerated, optimal load is not for maximum output power, but for reliable junction temperature to ensure long Mean Time To Failure (MTTF).

• Power gain, efficiency, impedance match must be accurately optimized for performance and thermal reliability using a closed loop electro-thermal and nonlinear circuit simulation.

• For pulsed and modulated signal operation, dynamic ETH model generation and reuse speeds up ETH circuit simulation by 10x to 100x for thorough design exploration of ETH design options before tedious layout design changes.