Search

In this paper, a microwave sensor with a meandered microstrip structure is introduced to measure the permittivity of the various liquids. The performance of the sensor is based on the change of operating resonance frequency during the absence and presence of materials in the sensing area. In this study, liquids including ethanol, methanol, aqueous glucose solution, and deionized water have been selected as samples under test. The proposed sensor has been implemented on RO4003 substrate with dimensions of 35 × 20 × 0.508 mm3 and operating frequency of 6.21 GHz in a free load state with a Q-factor of 506. When the samples are present in the sensing area, the frequency of the sensor shifts from 5.42 to 3.27 GHz. The sensitivity of 0.64% is obtained for the presented sensor. Compact size, linearity of changes, and low cost are the most important advantages of the sensor. The introduced sensor can be used in various fields of industrial, medical, and diagnostic due to its performance. [ABSTRACT FROM AUTHOR]

This article shows the design of two different low phase noise (LPN) planar X-band frequency oscillators using two various microstrip filters (MFs). These two MFs act as a frequency stabilization part in the loop of the microwave oscillator. The first one, the modified Jerusalem MF (MJ-MF), is based on the Jerusalem scheme. The second one, the complementary modified Jerusalem MF (CMJ-MF), is complementary of the MJ-MF. Finally, by employing the branchline coupler, the LPN MF oscillator is achieved. The MJ-MF (narrowband filter) LPN X-band oscillator operates at 8.17 GHz and denotes a phase noise (PN) of −161 dBc/Hz at 1-MHz frequency offset. The CMJ-MF (wideband filter) LPN X-band oscillator operates at 8.14 GHz and mentions a PN of −157 dBc/Hz at 1-MHz frequency offset. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a microwave sensor is designed and built to measure the permittivity of aqueous solutions. The samples used in this experiment are different purities of ethanol mixed with water. Ethanol solution with different purities is a widely used material in industry. Structures of meander, ladder, and T‐structure were used to design the sensor. Then the designed sensor is simulated in CST software in range of relative dielectric from 10 to 80. After obtaining the desired answer in the simulation, the proposed sensor is built on the Rogers 4003 substrate, the built‐in sensor measured ethanol solution with a purity of 5% to 35% (equivalent to permittivity of 76 to 58), and is showed a sensitivity of 4% and a Q‐factor of 3500. The results of simulation and measurement are consistent with each other, and they indicated that the proposed sensor beyond the fluids can be supported and determine their relative dielectrics. [ABSTRACT FROM AUTHOR]

This study denotes a procedure of a small phase noise (SPN) oscillator employing three different substrate integrated waveguide (SIW) resonators as a frequency stabilization‐component. The SIW resonator as modifying phase noise (PN) is investigated and branchline coupler in the feedback loop is presented. The design technique to attain SPN usage for optimized efficiency is proposed. Then, three different X‐band SIW oscillators using a packaged GaAs FET transistor are planned. Due to the PN and compacting, the miniaturized conventional SIW (MCSIW) oscillator is selected. This MCSIW oscillator operates at 8.15 GHz, mentions a PN of −169 dBc/Hz at 1‐MHz frequency‐offset. [ABSTRACT FROM AUTHOR]