Substrate Integrated Waveguide Sensor Research Articles

A dual-mode microwave sensor for retrieving permittivity of materials based on multiple complementary rectangular ring resonators

A dual-mode microwave sensor based on multiple complementary rectangular ring resonators (CRRRs) are proposed to characterize the permittivity of material under test (MUT) in this manuscript. The designed microwave sensor is based on substrate integrated waveguide (SIW) with multiple CRRRs etched on the top plane. With comparison to traditional microstrip line excited sensors, the proposed SIW sensor has a higher quality factor. The SIW structure has the feature of bandpass filter, and the geometrical parameters of SIW are optimized to achieve an ultra-wideband with the cavity resonant modes of TE101, TE102, TE103, and TE104. The four cavity resonant modes (TE101, TE102, TE103, and TE104) substitute the pass-band, and by utilizing the characteristic of quasi bandpass filtering of SIW, four pairs of identical CRRRs can produce two resonant modes in the passband, named by mode1 and mode2. The electrical field distribution of mode1 is mainly confined at two intermediate resonators, and mode2 has an intensive electrical field at resonators on both sides. As the resonant frequencies are altered with the variations of permittivity of MUTs, thus the mathematical expressions can be obtained. By using the mathematical expressions, the permittivity of MUTs can be predicted. Moreover, the error model is used to decline the error of measurement. The equivalent circuit model is established to illustrate the operating principle of the sensor. A good agreement between circuit model and simulation is acquired. In the measurement, the average sensitivities of proposed microwave sensor are about 6.33% and 6.17% for mode 1 and mode 2, respectively. Besides, the errors of retrieving permittivity are about 0.5% and 0.9% for mode 1 and mode 2, respectively.

Flexible SIW humidity sensors based on nanodiamond sensing films

AbstractIn this paper, flexible substrate integrated waveguide (SIW) resonators have been designed and fabricated on polyimide substrates for humidity sensing applications. The proposed SIW resonant cavity allows the resonator to obtain the maximum humidity sensitivity and meet the demand for flexible microwave sensing detection. Meanwhile, the humidity response performance can be further significantly enhanced by introducing nanodiamond (ND) sensing material. Three prototypes of ND-coated SIW sensors with different bending radii are measured to analyze their humidity sensing performance. The experimental results demonstrate that the proposed ND-coated SIW sensor with the minimum bending radius can achieve a maximum humidity sensitivity of 1.09 MHz/% relative humidity (RH) in the high RH region (>75.3% RH) and a low humidity hysteresis of 1.8% in the range of 11.3–97.3% RH. This study provides a promising candidate to realize flexible microwave sensors with excellent sensing performance.

A Substrate Integrated Waveguide Resonator Sensor for Dual-Band Complex Permittivity Measurement

This paper presents a novel dual-band substrate integrated waveguide (SIW) sensor that is designed to measure the complex permittivities of liquids or solid powders at two industrial, scientific, and medical (ISM) frequencies simultaneously. Resonant frequencies and quality factors are obtained from S-parameter measurements with the proposed SIW sensor, and applied to reconstructing the permittivities of materials under test through an artificial neural network. The water–ethanol mixed liquids were measured with the proposed sensor. The maximum deviations of the measured permittivities at 2.45 and 5.8 GHz are within 3% of literature results. The measurement by the proposed SIW sensor with artificial neural network reconstruction is accurate and efficient.

Permittivity Estimation of Dielectric Substrate Materials via Enhanced SIW Sensor

An enhanced substrate integrated waveguide (SIW) cavity sensor is proposed and designed in this work operating under sub -6 GHz 5G band suitable for the accurate permittivity estimation of low-loss dielectric materials. The proposed SIW sensor is designed for the fundamental TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>101</b></sub> mode at the resonance frequency of 3 GHz. The designed sensor is excited by employing a newly optimized external coupling topology incorporating a transition offset, contrary to the conventional microstrip feed. Due to which, a fully planar SIW sensor is developed for the first time without incorporating any active component, exhibiting a substantially high unloaded quality factor of nearly 515 basically required for the accurate testing of low loss tangents. Besides, the designed sensor is yielding a high sensitivity of 20 MHz (equivalent to 0.67% in terms of normalized sensitivity) desirable for segregating nearly resembling dielectric constants. Several standard dielectric samples are tested for the performance validation revealing that the proposed sensor is efficiently differentiating between Plexiglass ( ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.6) and PVC ( ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.65). Simultaneously, the sensor is accurately determining even the low loss tangent of Teflon (tan δ = 3.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> ). The measurement results are in close agreement with the references available in the literature. A thorough comparison with the state of the art literature corroborates the advantages offered by the proposed sensor and hence, its usability. Apart from characterizing the commercial grade dielectrics, this resonator is also potentially appropriate for designing high performance RF filters, oscillators and other devices.

A microwave SIW sensor loaded with CSRR for wireless pressure detection in high-temperature environments

In this study, a microwave substrate integrated waveguide (SIW) sensor loaded with complementary split ring resonator (CSRR) for wireless pressure detection in high-temperature environments was presented. The CSRR structure is placed directly above a substrate with an embedded sealed cavity, which is sensitive to pressure. The resonant frequency of sensor is in response to pressure because the strongest electromagnetic field is mainly concentrated on the CSRR. The working principle of the pressure sensor is elaborated via circuit analysis and simulation optimization of high frequency structure simulator (HFSS). The designed sensor worked at about 2.4 GHz to avoid use of expensive measurement equipment. The sensor was customized, and fabricated on the high temperature co-fired ceramics (HTCC) using the three-dimensional co-firing and screen printing technology. The as-prepared sensor can stably work at the ambient environment of 25 °C–800 °C, and 10–300 kPa with a highest pressure sensitivity of 206.89 kHz kPa−1 at 800 °C. The sensor described in this study has the advantages of simple structure, higher quality and sensitivity, and lower environmental interference and has the potential for utilization in multi-site pressure testing or multi-parameter testing (temperature, pressure, gas) in high-temperature environments.

Highly Sensitive Air-Filled Substrate Integrated Waveguide Resonator Integrated Wireless Passive Slot-Antenna for Confined Environmental Detection

In this paper, highly sensitive air-filled substrate integrated waveguide (SIW) resonators integrated wireless passive slot-antenna are designed and fabricated for confined environmental detection. The models of SIW sensors were established by using the software of HFSS to optimize the performance of the sensor for the 802.11 WLAN application. Due to the symmetry and the ideal-wall characteristic of the SIW, the SIW sensor can be designed into a half-mode substrate integrated waveguide (HMSIW) to reduce the size of the sensor. The SIW and HMSIW sensor were fabricated and measured experimentally. The sensitivities of HMSIW sensor for humidity detection without humidity sensitivity materials using the dielectric perturbation method were 187.67 kHz/%RH and 0.233 dB/%RH and 211.5 kHz/%RH and 0.33 dB/%RH for SIW sensor. Meanwhile, the SIW sensor can also realize the detection of ammonia filled with polyaniline material into the air-filled hole array of sensor. The slot-antenna integrated wireless passive air-filled SIW resonators with the low-cost advantage provide a new method for the detection of confined environments.

Reconfigurable microwave SIW sensor based on PBG structure for high accuracy permittivity characterization of industrial liquids

In this paper, we present a novel tunable microwave sensor for permittivity determination of industrial liquids. The proposed sensor is cavity based which is developed on a Substrate Integrated Waveguide (SIW). To enhance the characterization accuracy, the reconfigurable sensor is equipped with a Photonic Band Gap method and variable capacitors. Moreover, we employ the cavity perturbation technique in order to calculate the permittivity. In the characterization process, we obtain the permittivity of an unknown material by considering a resonant frequency shift. In fact, a capacitance is the main parameter for controlling the sensor resonance. We herein change this capacitance via reconfigurable SIW cavity and applying different materials. The proposed tunable architecture lets us study the material characteristic in the wider frequency range. The structure is designed in 5–6 GHz in order to determine the electromagnetic behavior of a brand new and used transformer oil samples. The results present a highly accurate permittivity of these oil samples. Hence, the proposed method and setup is not only suitable for oil ageing programs, but also applicable for other industrial liquid applications.

Compact substrate integrated waveguide sensor for liquids permittivity measurement

A compact substrate integrated waveguide (SIW) liquids permittivity sensor structure that utilizes half-mode (HM) and slow-wave (SW) techniques for the miniaturization of SIW sensor is presented in this paper. First, HM miniaturization technique is applied to SIW resonator cavity. Sensor width is reduced by 50% in comparison to the conventional resonator. Due to the complexity of the relationship between the complex permittivity of the substrate and liquids under test, artificial neural network tool is used as a simple and fast method to determine liquids’ complex permittivity through the measured resonant frequency and unloaded quality factor. The sensor is fabricated, and good agreement with simulations is observed according to the obtained experimental results. In the second step, SW and HM techniques are applied to the SIW sensor. The application of the HM and SW techniques indicate that an increase in sensor miniaturization while obtaining a better quality factor could be achieved. Furthermore, HM-SW-SIW is not fabricated, and we are satisfied with simulation results since we have fabricated other components. Moreover, good correspondence between the measurement and simulation results is obtained. Finally, a comparison between the structures presented in this paper and those published previously is made, demonstrating that a minimum of 25% miniaturization is achieved while maintaining acceptable characteristics.

SIW resonator humidity sensor based on layered black phosphorus

A passive microwave substrate-integrated waveguide (SIW) resonator humidity sensor using black phosphorus (BP) as sensitive layers has been presented. The proposed structure consists of an SIW cavity resonator operating at S-band and a folded sensing slot opened on the top plane. The humidity sensing performances of the proposed sensor were tested in the relative humidity range of 11–97%. Compared with an SIW resonator without BP sensitive layers, the sensitivity of the proposed SIW sensor with BP nanosheets significantly increased about 40 times.

Microwave Chemical Sensor Using Substrate-Integrated-Waveguide Cavity [corrected

This research proposes a substrate-integrated waveguide (SIW) cavity sensor to detect several chemicals using the millimeter-wave frequency range. The frequency response of the presented SIW sensor is switched by filling a very small quantity of chemical inside of the fluidic channel, which also causes a difference in the effective permittivity. The fluidic channel on this structure is either empty or filled with a chemical; when it is empty the structure resonates at 17.08 GHz. There is always a different resonant frequency when any chemical is injected into the fluidic channel. The maximum amount of chemical after injection is held in the center of the SIW structure, which has the maximum magnitude of the electric field distribution. Thus, the objective of sensing chemicals in this research is achieved by perturbing the electric fields of the SIW structure.