Isolating and Characterizing Critical Traces Using EM Analysis
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Figure 9 illustrates the simulation results for the VCO. The curves illustrate the oscillation frequency in GHz (vertical axis)
versus voltage (horizontal axis). The red curve shows the case where only models in the Spectre circuit simulator are used.
The blue curve shows the results when parasitics are added for the nets using a parasitic extractor. The green curve shows
the AWR AXIEM EM simulation results used for the spiral inductor instead of a model, demonstrating that the more accurate
EM representation of the spiral's performance is required, as opposed to using the built-in model.
Figure 10: Simulation results for VCO
Conclusion
As frequencies of operation push upward, EM simulators are becoming more and more critical for RFIC designers. Distributed
effects, such as inductors, become important, as do frequency-dependent effects such as resistance. Grounding issues
become critical and must be accounted for in simulations. Structures such as meshed ground planes and rings need to be EM
simulated to ensure they are modeled correctly. Coupling effects between various components, which are not included in
models, become an issue and must be EM simulated.
The AWR AXIEM EM solver/Virtuoso RF Solution design flow seamlessly integrates the process of accounting for EM effects
within a circuit design project by enabling a single environment for simulation, LVS, and EM analysis and verification, without
the need for unique schematics for EM and LVS. This flow reduces the chance of error and cuts down on design time and
verification cycles.
