Design of Microwave-Based Angular Displacement Sensor

Microfluidic reflective-mode differential sensor based on open split ring resonators (OSRRs)

“…Frequency variation is the most common sensing mechanism in resonant sensors [9][10][11][12][13][14][15][16][17][18]. The output variable in such sensors is the resonance frequency (and eventually the peak, or notch, magnitude), determined by the properties of the surrounding medium.…”

“…The output variable in such sensors is the resonance frequency (and eventually the peak, or notch, magnitude), determined by the properties of the surrounding medium. Frequency variation sensors have been applied to the measurement of displacements and velocities [9,18], but this type of sensors is of special interest for the dielectric characterization of solids and liquids [10][11][12][13][14][15][16][17]. Typically, these sensors require calibration and are subjected to cross sensitivities, caused, e.g., by changing environmental factors, such as temperature or humidity.…”

Directional‐coupler‐basedmicrowave sensors for differentialangular‐displacementmeasurement

“…Considerable attention is thus being dedicated to the engineering of angular-displacement sensors due to their potential interest in control systems, such as in the reaction wheels of space vehicles for altitude control and torque measurement, as well as in other relevant applications as seismic scenarios since they are sensitive to structure or ground rotations. [12][13][14][15][16][17][18][19][20][21][22][23] Whereas some realizations of this type of sensors operating at the lowfrequency region have been devised, 12 most of them exploit microwave-measurement techniques based on resonating circuits in their angular-displacement detection mechanism. Attending to the specific measurable that is considered for the sensing process, these microwave-resonator-based angular-displacement sensors can be classified into three different families.…”

“…14,15 The second category of microwave-resonator-based angular-displacement sensors, which are mostly based on metamaterial-inspired resonators, operate in basis to the variation of a notch frequency or TZ in their transmission response as a function of the angular-displacement to be measured. Some exponents to be highlighted, [16][17][18] which exploit different solutions as follows: (a) the overlapping area of U-shaped resonators for the stator and the rotor depending on the rotational angle, (b) microstrip-coupled complementary SRRs (CSRRs), and even (c) comb-like or nested SRR pairs that are interrogated by a single-slot microstrip antenna to obtain sub-milliradian resolution along with high sensitivity. However, they exhibit some limitations, such as a dynamic range that cannot exceed 90 17 and good linearity only for a very-reduced 5 angularvariation interval.…”

“…Some exponents to be highlighted, [16][17][18] which exploit different solutions as follows: (a) the overlapping area of U-shaped resonators for the stator and the rotor depending on the rotational angle, (b) microstrip-coupled complementary SRRs (CSRRs), and even (c) comb-like or nested SRR pairs that are interrogated by a single-slot microstrip antenna to obtain sub-milliradian resolution along with high sensitivity. However, they exhibit some limitations, such as a dynamic range that cannot exceed 90 17 and good linearity only for a very-reduced 5 angularvariation interval. 18 The dynamic range limitation of the SRR sensors can be addressed by using multiple resonators in a microwave rotatory encoder configuration to improve the sensing capability.…”