A new sensor based on substrate integrated waveguide (SIW) technology is proposed as an option for liquids electrical characterization. The sensor employs a rectangular waveguide resonant cavity filled with air, with two opposite side walls implemented by closely spaced metallic vias. The resulting structure is a hybrid SIW resonant cavity. The two noncontinuous walls of the hybrid SIW cavity allow the liquid insertion, filling its entire internal volume. The resonance frequency of the hybrid SIW cavity is used to determine the dielectric constant of the liquid to be characterized. A sensor using a hybrid SIW cavity operating in TE101 mode was designed to resonate at 5.9 GHz when filled with air. The sensor was employed to measure the dielectric constant of binary mixtures of distilled water and ethanol. Dielectric constants ranging from 21 to 79 were obtained, corresponding to measured resonance frequencies from 1,247 to 647 MHz, respectively. Good agreement was observed between computational electromagnetic simulation and experimental results. The dependence of the volumetric fraction of ethanol in the binary mixture on the sensor resonance frequency was expressed using a third‐order polynomial approximation.

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This article presents a novel tunable bandpass filter designed in substrate integrated waveguide (SIW) technology to operate at 3.5 GHz, a frequency widely used in 5G and WiMAX systems. The bandpass filter uses shunt‐inductive discontinuities provided by a novel offset post arrangement that resulted in a compact filter. The filter bandwidth is tunable through PIN diode switches connected to the metal posts, allowing three different operation states. The novel tunable filter was fabricated and demonstrated bandwidths of 6.23% and 0.714% centered at 3.5 GHz, with low insertion losses. The measured results are in good agreement with full‐wave simulation results.

This research work presents a detailed study about substrate integrated waveguide (SIW) operating in microwave frequencies based on rectangular waveguides (RWG) theory. The study about SIW associates equations presented at the literature and uses electromagnetic simulations to develop a well-defined design procedure. Is considered the integration between substrate integrated waveguides and microstrip line, designing transitions between these two structures with the aim to provide impedance matching and make possible the characterization in microwave . Is shown a sensibility analysis of the waveguides and filters performance in SIW technology to evaluate the layout differences caused by manufacturing process.With the experimental results and simulation results was possible validate the design procedures and the manufacturing process of the SIW circuits operating in microwave frequencies.