A Dual-Band Integrated Network Analyzer for Water Solvent-Specific RF Biosensors

A solvent-specific novel integrated biosensing network analyzer (IBNA) for the detection of materials with varying dielectric constant (i.e., permittivity) is reported in this article. The proposed IBNA works on the concept that any change in permittivity of the material under test (MUT) results in a change in capacitance of the RF bioliquid cavity’s resonant frequency measured by the measurement unit. An interdigitated capacitor-based RF bioliquid cavity resonating at 2.3 GHz performs the sensing operation, while a dual-band six-port reflectometer (DBSPR) with an operating frequency of 1.1 and 2.3 GHz facilitates the measurement of the s-parameters and hence the extraction of permittivities. The DBSPR operating at 1.2 and 2.3 GHz required development of a dual-band coupler which exhibits
$|{S}_{{11}}|$
of −30 and −25 dB and a bandwidth of 573 and 644 MHz at the chosen design frequencies. It also required design of a dual-band power dividers which possess
$|{S}_{{11}}|$
of −21.5 and −34.5 dB with a bandwidth of 301 and 264 MHz at the design frequency. The eventual prototype of DBSPR achieves respective bandwidths of 254 and 215 MHz at 1.12 and 2.26 GHz. The resonant frequency of the designed sensing unit loaded with water is 2.483 GHz and this falls in the second band of the DBSPR. Finally, the detection of 1 M Glucose and Sucrose is performed in simulation and experiments and these yield excellent respective frequency shifts of 15 and 20 MHz at room temperature.