Detailed error analysis and automation of the RA Resonator technique for measurement of uniaxial anisotropic permittivity

Dual-Band Uniaxial Dielectric Anisotropy Sensor Using Coupled-Line Resonators

“…Step 3 Next, the fabricated sensor loaded with planar samples is tested. It is worth mentioning that the surface roughness and the air gap between the SUT and sensors are the two main challenges in measuring solids with planar structures [11], [12], [13], [14], [15]. The air gap between the SUT and sensors is removed in the experiments by using Styrofoam which is pressed over the sample and the pressure is increased until there is no change in the measured singleended S-parameter, as was proposed in [12].…”

“…Resonant methods for anisotropy characterization, which are the focus of this paper, have been implemented with different technologies that fall into waveguide [7], [8], [9], [10] or planar circuit [11], [12], [13], [14]. In [8], a dielectric cavity resonator enclosing an anisotropic sample under test (SUT) inside is used.…”

“…On the other hand, in [11], [13], and [15], a dual-mode strip line resonator is used for anisotropy characterization at multiple frequencies. For this, each mode of the resonator has a different distribution of horizontal and vertical directed fields.…”

“…Using an electromagnetic analysis of the dual-mode resonator, the resonant frequencies of the modes are space mapped to the horizontal and vertical dielectric constants through an iterative process. The sensor in [11], [13], and [15] is a long resonator that has characterized an FR4 sample in seven frequencies, corresponding to the first to seventh-order resonance of the resonator. That sensor uses a destructive characterization method, since it is necessary to implement the sensor on each sample which is going to be characterized.…”

“…It is important to mention that the methods proposed in [8], [11], [13], and [15] were successfully tested for multiple frequencies, however, they are not flexible in the sense that they could characterize anisotropic samples at multiple frequencies but only one frequency could be established in the design of the sensor and the other frequencies are the multiple order harmonics. Additionally, the method proposed in [9] and [10] can also characterize anisotropic samples at multiple frequencies; they use different resonance modes of a cavity, so there is no freedom in choosing the second or third frequencies in these methods as well.…”