A Miniaturized Broadband Multi-State Reflectometer Integrated on a Silicon MEMS Probe for Complex Permittivity Measurement of Biological Material

A fully integrated broadband multi-state reflectometer (MSR) covering both 2- and 16-GHz bands is developed using microelectromechanical systems and monolithic-microwave integrated-circuit technology for complex permittivity measurement of biological material. The MSR consists of a dual-band phase-locked loop, a power amplifier, a directional coupler, an impedance tuner, two RF power detectors, and a micromachined silicon planar probe with an open-ended coaxial aperture. All the active and passive circuit components have been integrated on the micromachined probe platform in a small form factor of 6.8 mm × 50 mm × 0.6 mm. To cover a broad bandwidth ranging from 2 to 16 GHz, the circuit components have been designed with multi-octave characteristics. The performance of the fabricated reflectometer has been verified by comparing the measured permittivities of 0.9% saline, pork muscle, and pork fat with the reference data. To the best of our knowledge, this is the first demonstration of a miniaturized active integrated broadband reflectometer for complex permittivity measurement of biological material.