Intermodulation distortion in YBCO at the intrinsic limit: Implications for filters

Recently, evidence has been presented by this group that the measured intermodulation distortion (IMD) in YBa2Cu3O7-x (YBCO) films of high quality is consistent with the intrinsic limit, given by the d-wave order parameter. This intrinsic nonlinearity is also known as the nonlinear Meissner effect. The measurements and theory of the IMD agree in magnitude, temperature dependence, and power dependence. We present our latest results of IMD measurements that strongly support the agreement with the d-wave theory. Thus, a detailed understanding of the nonlinearity in YBCO is emerging from the measurements and calculations. We present results of modeling the IMD in YBCO resonators with very good agreement with measurement. We also present simulations of the IMD in multipole filters assuming intrinsic nonlinearity. While the IMD results depend on geometry and filter design parameters, our simulation results can be used to draw some conclusions regarding IMD in filters and the effect on the dynamic ranges of systems with YBCO filters at the front end