A simple, tunable, and highly sensitive radio-frequency sensor

Abstract

We report a radio frequency (RF) sensor that exploits tunable attenuators and phase shifters to achieve high-sensitivity and broad band frequency tunability. Three frequency bands are combined to enable sensor operations from ∼20 MHz to ∼38 GHz. The effective quality factor ( ) of the sensor is as high as ∼3.8 × 10 with 200 l of water samples. We also demonstrate the measurement of 2-proponal-water-solution permittivity at 0.01 mole concentration level from ∼1 GHz to ∼10 GHz. Methanol-water solution and de-ionized water are used to calibrate the RF sensor for the quantitative measurements.

Resonator- and Filter-Induced Slow Waves for High-Sensitivity RF Interferometer Operations

“…To achieve high sensitivity and obtain rich information about material-under-test (MUT) have been the main challenges in these efforts, which often depend on measuring MUT dielectric properties. The newly developed tunable interferometers [11], [12] aimed at solving these problems. An effective quality factor of 3.8 × 10 6 and a frequency tuning range from ∼20 MHz to 38 GHz have been reported [11].…”

“…The newly developed tunable interferometers [11], [12] aimed at solving these problems. An effective quality factor of 3.8 × 10 6 and a frequency tuning range from ∼20 MHz to 38 GHz have been reported [11]. Approximately 50 DNA molecules in ∼1 nL water have been measured with such interferometers.…”

Two-stage radio-frequency interferometer sensors

“…Nevertheless, for high sensitivity measurements, the required system dynamic range is exceptionally large, e.g., $120 dB for an effective quality factor of $3 Â 10 6 . 7 As a result, such systems are difficult to use in rugged environments. To help address this problem, different filters and resonators [8][9][10] are proposed and demonstrated to improve sensitivity for a given dynamic range.…”

“…Sensitivity improvements are also observed at PGD and SP frequency regions. [5][6][7] in solution. Their design flexibility, tunable sensitivity, and frequency coverage are attractive properties for various sensing applications.…”

“…Radio-frequency (RF) interferometers have been demonstrated for high sensitivity detection and analysis of single cells, 1,2 particles, 3 DNAs, 4 glucose, methanol, and 2-propanel [5][6][7] in solution. Their design flexibility, tunable sensitivity, and frequency coverage are attractive properties for various sensing applications.…”