An Angular-Displacement Microwave Sensor Using an Unequal-Length-Bi-Path Transversal Filtering Section

Directional‐coupler‐basedmicrowave sensors for differentialangular‐displacementmeasurement

“…The comparison in Table I with previous related angular-displacement microwave-sensing devices available in the technical literature shows that the proposed sensor can provide comparable performance metrics compared to the state-of-the-art. However, note that the current angular-displacement microwave sensors are based on the TFS principle and exploit three TZs for sensing, This has the advantage of being able to use three metrics for the angle of rotation at the same time (with different sensitivities and in distinct frequency regions), while most of the existing works only use one metric (either variation in frequency location or modification of signal attenuation level), with the except of the author's previous work 23 which exhibits two metrics.…”

“…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.…”

“…Some example of this type, 21,22 includes the microstrip-coupled modified CSRR sensor with its ability to detect the direction of rotation by taking advantage of the asymmetric reflection and transmission phase behavior, 21 and the sensing method of using planar dual circular-polarized antenna pair to detect the phase change that is proportional to the relative roll angle between the two antennas. 22 Recently, a bi-path signal-interference transversal filtering section (TFS) based on two in-parallel transmission lines 23,24 is used as the stator, to which an open-ended rotational stub is attached as the rotor to alter the locations of the transmission zeros (TZs) of its transfer function. Since these TZs are created through the destructive interference of the two signal components inside the TFS whose characteristics are modified with the rotation of the stub, angular-displacement sensing capabilities are gained.…”

“…Specifically, the variation of the inter-TZ spacing as the measurable to attain high dynamic range and quasi-linear region, along with reasonably-high sensitivity. 23 The use of inter-TZ spacing allows a more robust measurement by mitigating the potential error due to the frequency shifting of the microwave source. The work shows the possibility of using the planar microwave circuitry, such as a filter for displacement sensing applications.…”

“…Moreover, additional measurables may be used for sensing if needed, such as the center frequency of lower close-to-f Z1 narrow passband, as can be observed in Figure 2C. Compared to its bi-path precursor, 23 the proposed sensor can provide extended angular-displacement microwave-sensing properties, such as dual-band sensing and three outputs, because of the positions of the out-of-band power transmission zeros can be easily controlled through the design parameters of the coupler-based transversal section.…”