I want to plot admittance vs. frequency for SAW device, so i iadd Study 2 (frequency domain). As we know, the two typical acoustic wave modules in COMSOL are "saw gas sensor" and "thin film baw resonator". In "thin film baw resonatore" module, some steps of plotting admittance vs. frequency are discribed. The most important step is the expression "abs(es. Y11)" used for plotting admittance vs. frequency. (see https://cn.comsol.com/model/download/397261/models.mems.thin_film_baw_resonator.pdf), therefore, i followed theses steps in the simulation of SAW device, but an error "undefined variable es. Y11" occured. So i want to know how to solve this problem, why here es. Y11 is undefined?

Can anyone help me with this, thank you very much! if you have solutions, you can revise the module "saw gas sensor" provided by COMSOL.