Considerations for measurement setup for second-order nonlinearity in radio-frequency bulk acoustic wave duplexers

This paper discusses the influence of the setup on the measurement reliability and reproducibility for the second-order inter-modulation distortion (IMD2) generated in RF BAW duplexers. Our measurement results show that the IMD2 level can be reliably and reproducibly measured when the port terminations are properly applied. For example, a filter and a relatively large (>20 dB) attenuator are necessary between an oscillator and the antenna port of the duplexer to suppress the nonlinear mixing and the impedance mismatching. If the order of these two devices were reversed, the IMD2 level would change significantly. Although an isolator is commonly used to stabilize the power amplifier output, our research results show that not using an ISO produced more accurate results.