RF system simulation technology has come a long way since the use of spreadsheets. Improvements in accuracy and diagnostic capabilities are significant. An example of these improvements includes identifying the component origin and frequency equation of nonlinear intermods; and which system blocks and their specs in the system lineup are contributing to performance degradation such as Error Vector Magnitude (EVM), BER, and ACPR under digital modulated RF stimulus.
Figure 2 shows the budget analysis of EVM error versus system component line up, which instantly identifies the major contributors of EVM degradation as LO phase noise and linearity of mixer and amplifiers. Clicking on the culprit components enables their offending specs to be adjusted in order to improve the system performance. This enables proper selection of system component lineup without over or under spec’ing them, to achieve the best performance with minimum cost.
Specifying the behavioral specs during design and then trying to find real components that have such specs during realization is a common but inefficient approach, which inevitably results in multiple iterations. Sys-parameters representing simulatable datasheets of real off-the-shelf components or X-parameters of measured nonlinear components can be used directly in RF system simulation, so that when the design is complete, parts have also been already specified and verified to work in the system chain. The system is now ready for hardware implementation.