Microstrip sensor and methodology for the determination of complex anisotropic permittivity using perturbation techniques

Abstract

In this work, a sensor in microstrip technology and a methodology for measuring the real part and the imaginary part of the complex uniaxial permittivity of solid anisotropic samples are presented. The sensor is based on a pair of parallel lines coupled resonators and a cleft arranged in the coupling region which allows to hold the samples under test (SUTs). The proposed methodology relates the change in the even/odd resonance frequency with the real part of the permittivity in the vertical/horizontal direction, and the change in the Q factor of the even/odd mode with the imaginary part of the permittivity in the vertical/horizontal direction. The methodology was successfully verified with the characterization, at 2.43 GHz of anisotropic samples of printed PLA, Diclad 880, and RO4350B using the knowns materials: RT5870, PTFE and RO4003.

The Automatic Design of Multimode Resonator Topology with Evolutionary Algorithms

“…One of the most important problems with optimizing the microstrip resonator topology is the computational complexity of the fitness function: modeling the AFC of the resonator in a specified frequency range may take from 5 to 60 s. Resonators used as sensors may have very simply [15,16,45,46,79] or rather sophisticated topology [17,18,80]. For more complex topology, the modelling can take more time.…”

“…At the same time, the scope of microstrip resonators is not limited to frequency-selective designs. Microwave sensors designed on their basis are of high interest [14][15][16]. The concept of microwave sensors based on microstrip resonators is based on changes in their frequency response depending on the dielectric permittivity of the samples under test which are considered as an additional dielectric layer [14,[17][18][19][20][21] or are introduced in the cleft of the proposed sensor [16,22].…”

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.…”

“…The sensor is designed on an isotropic substrate and is composed of two pairs of coupled resonators. We have used the resonators described in [11], [12], and [14] because they are straight lines, symmetrical to have even and odd modes, easy to manufacture and simple when performing the electromagnetic simulation. The two pairs of resonators share an input port through a T-shaped structure to separate the two frequency bands with high isolation.…”