An alternative method for the measurement of the microwave temperature coefficient of resonant frequency (τ_f)

摘要

In this paper an alternative method for the measurement of the temperature coefficient of resonant frequency (τ_f), is presented. The traditional method (based on the Courtney method) present some limitations of measuring the values of τ_f, for samples with high dielectric loss due to their inability to observe clearly the TE_(011) mode. The alternative experimental setup, to measure the τ_f value, is based on the variation of the temperature of the dominant mode of a dielectric resonator antenna. The method is quite compatible with the measurement of τ_f, based on the Courtney method. It presents the advantage that it is less sensitive to the sample loss. In the studied samples, with loss higher than 10~(-2), the τ_f were obtained. Samples of known τ_f were measured in both methods, using the configuration proposed by Courtney and the present study. The alumina (A1_2O_3) and calcium titanate (CaTiO_3) were selected because they have well known values of τ_f and have low dielectric losses, the bismuth niobate and titanium (Bi_3NbTiO_9) was chosen because it is not possible to measure its τ_f by the traditional method due to its high dielectric loss. The obtained results, by measuring, the τ_f value of CaTiO_3 and Al_2O_3, in this proposed method, present excellent agreement when compared to the traditional Courtney, transmission method. It was also very efficient for measurements of the τ_f value, of high dielectric loss materials (>10~(-2)), as for the bismuth and titanium niobate (Bi_3NbTiO_9). The analysis of the temperature coefficient of resonant frequency (τ_f) in dielectric resonators is an important property for the development of electronic devices. This is because the τ_f is a fundamental parameter, for the production of new components like filters, oscillators and antennas, with high thermal stability.