BITS Faculty Publications
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Item Application of a Cylindrical Dielectric Resonator as an Angular Displacement Sensor(IEEE, 2020) Kumar, A. V. PraveenAuthors investigate the application of a cylindrical dielectric resonator (CDR) for detecting the angular displacement with the help of numerical simulations. The CDR is made bisymmetric by attaching a metal strip diametrically on its top-face to enable angular sensing in the range of 0 - 90°. The CDR is coupled to a single microstrip line for reflection mode measurement, while it is coupled to two microstrip lines for transmission mode measurement. Identically in both the configurations, the CDR resonates at the HEM 11δ mode frequency of ≈3.5 GHz, with the magnitude of the respective S-parameters varying with the strip angle. The CDR configurations provide nearly identical sensitivities and quasi-linear ranges of ≈0.26 dB/°, and 70° respectively for the reflection mode, while ≈0.3 dB/° and 60° respectively for the transmission mode operation.Item A Non-Invasive Feed Approach to Excite the Electric Monopole Mode of a Dielectric Resonator Antenna(IEEE, 2021-11) Kumar, A. V. PraveenA non-invasive feeding method to excite the electric monopole mode (TM 01δ mode) of a cylindrical dielectric resonator (DR) antenna or DRA is presented. The feed comprises a non-resonant circular metallic patch with four symmetric stubs, fed by a coaxial probe. The monopole mode of the DRA is excited by the patch rather than the probe, hence the need to drill an axial hole in the DR for conventional probe insertion (invasive feed) is avoided. Using ANSYS HFSS simulations, the viability of this new feed is demonstrated and results are compared with that of a probe-fed DRA exciting the same mode.Item Comparative Analysis of Dielectric Resonator based Linear Displacement Sensor with Various Microwave Feeding Techniques(IEEE, 2022) Kumar, A. V. PraveenThe authors presents the comparative analysis of a dielectric resonator (DR) based linear displacement sensor with various microwave feeding techniques. A cylindrical DR excited by common feeding techniques such as the coaxial probe feed, microstrip slot feed, microstrip line feed, and coplanar waveguide feeds is numerically investigated using ANSYS HFSS. Single-port or reflection mode sensor characteristics such as the frequency shift, displacement sensitivity, linearity, and dynamic range are found to be highly dependent on the feeding technique.Item Investigation on the aspect ratio of conducting superstrates in deciding its function as a gain enhancer/suppressor for wideband slot antenna(Springer, 2022-07) Kumar, A. V. PraveenThis paper presents an investigation on the effect of the aspect ratio (AR or width-to-length ratio) of a conducting sheet for radiation control i.e., gain enhancement or suppression, leading to useful applications for wireless communication. A wideband slot antenna working in 6–8.5 GHz band is adopted as the basic antenna. It is found that for the sheet AR < 1, the boresight (θ = 0°) gain in the entire band is enhanced, while for AR > 1, boresight gain suppression is achieved. For an optimum AR such that AR(enhancement) = 1/AR(suppression), the same sheet can serve the above dual purposes according to its azimuthal orientation with respect to the slot. For ϕ = 0° orientation with respect to the slot, the sheet acts as a gain enhancer, while for ϕ = 90° orientation, it suppresses the radiation, both in θ = 0°. Practically, the sheet orientation can be easily controlled manually. Antenna measurements demonstrate an impedance band of 6–8.66 GHz with bidirectional radiation pattern, and 1.11 dBi boresight gain at 7.25 GHz. A conducting sheet of size 1.45λ0 × 0.29λ0 where λ0 is the free-space wavelength at 7.25 GHz, is loaded above the slot which improves the boresight gain by 5.77 dB, and when rotated by ϕ = 90°, suppresses the gain by 8.78 dB, both relative to the original slot antenna.Item Sensitivity Comparison of Common Microwave Feeds to be Useful in Angular Displacement Sensors(IEEE, 2022) Kumar, A. V. PraveenIn this work, the authors analyze the performance of dielectric resonator (DR) based angular displacement sensor with different feeding methods. It is demonstrated that, sensor characteristics like resonant frequency, impedance matching, sensitivity, and dynamic range are highly dependent on the selected feeding technique. The common microwave feeds such as the coaxial probe, slot line, microstrip line, and conformal microstrip line are considered for reflection mode operation. Standard commercial EM simulation tool ANSYS HFSS is used for performing the simulations. Analysis of the simulation results lead to proposing the microstrip line feed for realizing fixed-frequency DR based angular sensor which is experimentally validated.Item Application of HEM11δ Mode in DR based Linear Displacement Sensor(IEEE, 2023) Kumar, A. V. PraveenPresented a numerical investigation on the application of HEM 11δ mode in a dielectric resonator (DR) sensor. A simple two-port network is implemented by placing two microstrip lines opposite to each other for full transmission. A dielectric resonator (DR) is placed between them to detect the coupling w.r.to its displacement. Proposed transmission mode operated DR excite HEM 11δ mode at~ 3.7 GHz. Here, the DR positional movement produces identical results in both directions (+dx/ -dx) due to the structural bisymmetry. This single frequency operated Transmission circuit provides 1.78 dB/mm sensitivity in the 0 - 9 mm range.Item A Microwave Resonator Realized Combined Displacement Sensor(IEEE, 2023) Kumar, A. V. PraveenIn this work, a microwave resonator realized combined displacement sensor is presented. To realize this, a metal-strip loaded DR is coupled to a pair of 50 ohm microstrip lines. The change in |S21| helps to find out the displacement. The proposed model excites both the strip mode and DR mode based on the alignment of movable resonator to fixed microstrip lines. To verify the HFSS response, the fabricated prototype is tested with VNA. The sensor features are compared with the existing combined displacement sensors.Item Two-Dimensional Wide Dynamic Range Displacement Sensor Using Dielectric Resonator Coupled Microwave Circuit(IEEE, 2023-11) Kumar, A. V. PraveenIn this article, the authors propose a two-dimensional (2-D), wide dynamic range, linear displacement sensor based on the microwave resonator principle. The sensor employs a cylindrical dielectric resonator (DR) proximity coupled to a pair of 50- Ω microstrip lines that are laid orthogonally over a microwave substrate. The DR is free to move on the substrate in the 2-D space between the microstrips so that the coupling strength of the excited DR mode varies with the DR’s proximity to the microstrips. This variation in coupling strength can be measured in terms of the two-port scattering (S) parameters of the circuit, from which the DR’s displacement can be estimated. The above circuit operates at a fixed frequency determined by the resonant frequency of the particular mode of the DR. Initially, one-dimensional (1-D) analysis using the |S21| sensitivity of the DR displacement reveals a dynamic range of more than 23 mm for the horizontal, vertical, and diagonal displacements. To enable full 2-D scanning by differentiating the horizontal and vertical displacements, the |S11| and |S22| parameters are also taken into account in addition to |S21| . Note that in all the above measurements, the sensor’s operating frequency remains constant at 3.67 GHz which is the resonant frequency of the DR. Such single-frequency sensors are highly robust to frequency offsets and are also cost-effective in practical realization compared with variable frequency sensors. This aspect as well as other performance parameters of the proposed sensor are compared with that of the existing 2-D sensors.Item Impact of the Design Parameters on the Microwave Displacement Sensor Performance(IEEE, 2023) Kumar, A. V. PraveenThe investigations have been conducted on the involved design parameters to analyze the behavior of the microwave displacement sensor output characteristics. To implement this, a dielectric resonator loaded to a reflection mode operated microstrip line circuit is proposed. For the proposed reflection mode sensor, the sensor features like resonant frequency, impedance matching position, sensitivity, and dynamic range are sensitive to the displacement of DR to microstrip line. The impact of the substrate shape and size, and resonators geometrical properties are numerically analyzed and experimentally validated by using VNA. The sensor analysis shows good matching between both HFSS simulations and VNA measurements.Item Multi Mode (Reflection and Transmission) Operated Dielectric Resonator based Displacement Sensor(IEEE, 2023) Kumar, A. V. PraveenA multi-mode operated microwave resonator based displacement sensor is presented. To enable this, a cylindrical dielectric resonator (DR) coupled microstrip line structure is established. The parameters like |S11| in reflection mode and |S21| in transmission mode are sensitive to DR displacements w.r.to transmission lines. The HFSS is carried out for numerical analysis and the fabricated sensor prototype is realized with VNA measurement. The sensor exhibits sensitivity of 6.2 dB/mm in the range of 0-4 mm in reflection mode and 1 dB/mm over 0-18 mm range in transmission mode. Both the HFSS and VNA responses are in good agreement with each other for this multi-mode operation. This reveals the selection of mode freedom to the choice of operation.