Integrated Microwave Sensor and Antenna Sensor Based on Dual T-Shaped Resonator Structures for Contact and Noncontact Characterization of Solid Material

This article proposes the integration of microwave sensors (MSs) and antenna sensors (ASs) for contact and noncontact characterization of solid materials. Integration between MS and AS was determined based on the reflection coefficient (
${S}_{{11}}$
), where
${S}_{{11}}$
of
${\ge }-10$
dB was proposed as MS and
${S}_{{11}}$
of
${\le }-10$
dB was proposed as AS. The proposed sensor consists of a dual T-shaped resonator with single port operating at a resonant frequency of
${f}_{r{1}}= {1.81}$
GHz for MS and
${f}_{r{2}}= {2.34}$
GHz for AS using FR-4 substrate with
$\varepsilon _{r}$
of 4.3, tan
$\delta $
of 0.0265, and thickness of 1.6 mm. Furthermore, the two resonant frequencies had independent characteristics with different sensing hot spots. MS is proposed for permittivity detection of the material under test (MUT) for contact detection while non-contact detection is proposed by utilizing AS. The procedure for contact detection was carried out by placing the MUT on the surface of the sensor, while noncontact detection was carried out by placing the MUT with an air gap between the MUT (
$d$
) and the AS was 0.5–1.5 mm. The measurement results showed that the average accuracy was 99.30% and 99.31% for the MS and AS for the permittivity range of 1–6.15, while the normalized sensitivities (NSs) of the proposed sensors were 1.15% and 0.16%, respectively. The results of this research are novel and can be recommended for several purposes related to biomedical and pharmaceutical industries requiring contact and noncontact detection of material characterization.