PROPERTIES OF FERROELECTRIC MATERIALS UNDER HIGH MICROWAVE POWER. NONLINEARITY. POWER HANDLING CAPABILITY
As a rule the investigation of ferroelectric thin films are devoted to small signal properties of these materials. The information about the behavior of the films under elevated microwave power is practically absent. This is a significant omission because the nonlinear response of ferroelectric elements to a microwave signal is undesirable in passive tunable devices and should be minimized to reduce nonlinear distortion of the operating microwave signal. On the other hand, microwave nonlinearity is promising for the development of nonlinear active devices. Besides, the ferroelectric thin film heating due to the microwave energy dissipation leads to variations in nonlinear properties of the films and, consequently, in the performance of microwave devices incorporating these films. These are the reasons why the microwave nonlinearity of tunable devices based on thin ferroelectric films continues to be an area of extensive study.
The pulse measurements
Two main mechanisms define the upper level of the operating microwave power:
- nonlinear electric field effect (fast process)
- overheating effect (slow process)
To separate fast E-field and slow thermal responses to microwave power the pulse measurements have been developed.
The effect of elevated microwave power on resonance curve of resonator with nonlinear element
IMD measurements of ferroelectric circuit
One-tone and IMD measurements allow to define the parameters of microwave nonlinearity of ferroelectric elements in terms of nonlinear capacitance and nonlinear conductance and to estimate the overheating of the ferroelectric elements due to microwave energy dissipation.
Power handling capability of ferroelectric devices
Influence of high microwave power on the device parameters
Estimation of phc for ferroelectric devices
Power handling capability of 5-cascade 2.4 ghz ferroelectric phase shifter