The microwave waveguide and resonator methods are compared as applied to the experimental determination of the dielectric properties of high loss liquids. A differential microwave waveguide cavity for measuring high loss liquids complex permittivity in a small volume has been designed and studied. This cavity consists of two circular waveguide cells with central rods made of quartz and surrounded by high loss liquid tested. The cells have different lengths to eliminate complex propagation coefficient measurement errors due to the diffraction effect on the ends of the layered waveguide cells. We have measured the wave amplitude and phase coefficients for the waveguide cavity to estimate physical properties of a high loss liquid under test. The resonant frequencies and the Q-factor of a semi-disk dielectric resonator with high loss liquid filling a capillary have been measured. We have selected water-ethanol solutions as a high loss liquid under test for both techniques. We have determined the measurement sensitivity for these two techniques. The measuring results are discussed. Both the waveguide and resonator methods provide comparable sensitivity and can be successfully used for the complex permittivity characterization of high loss liquids in small volumes.

In this paper, a microstrip diplexer composed of two similar resonators is designed. The proposed resonator is consisting of four microstrip cells, which are connected to a coupled lines structure. In order to select a suitable geometric structure, first, all cells are assumed as undefined structures where there is a lack of basic information about their geometry and dimensions. Then, an equivalent LC circuit of the coupled lines is introduced and analyzed to estimate the general structure of the resonator respect to a requested resonance frequency. The proposed diplexer is designed to operate at 2.36 and 4 GHz for wireless applications. The insertion losses (S21 and S31) are decreased significantly at the resonance frequencies, so that they are 0.2 and 0.4 dB at 2.36 and 4 GHz, respectively. The designed diplexer is fabricated and measured and the measurement results are in a good agreement with the simulations.

In this paper, a resonator is modeled as a microbeam under the effect of thermoelastic damping and actuated electrically. Two models, small and large deformation models, are represented by considering linear and nonlinear Euler-Bernoulli beam theory. These models are compared against voltage, and the difference between these models is shown and discussed. In the large deformation model, the microbeam deflected due to applied DC voltage, and vibration of microbeam occurs around this static deflection. The vibration equation is linearized around static deflection and by applying harmonic vibration, equation for mode shape and frequency is obtained. The complex frequency is calculated by numerical method and then used for obtaining the Q-factor of thermoelastic damping. The stretching effect and thermoelastic damping is validated with the literature. The result shows that for the high values of voltage, the large deformation model is more accurate. The behavior of thermoelastic damping is also investigated against the geometrical and material properties.

In this paper, for the first time, we present a novel Pi-shaped structure using resonators for multiband applications. The multiband Pi-shaped structure with LC resonators is analyzed. In order to demonstrate the proposed multiband Pi-shaped structure, one tri-band Wilkinson power divider and one tri-band rat-race coupler are designed, fabricated, and tested. The compactness of the two demonstrated components is well kept by putting all stubs with resonators inside the components themselves. Measured results are in good agreement with the simulated results.

In this paper, a new way of obtaining a band rejection in a ultra wideband (UWB) filter using a uniplanar Electromagnetic bandgap (EBG) structure is reported. The EBG structure has a bandgap centered at 6.69 GHz which is almost 38% lower compared with the conventional uniplanar EBG of same dimensions. A one-dimensional EBG structure coupled with a microstrip line provides a narrow bandgap, which is used in obtaining a notch in the UWB filter. Single notch UWB filters with variations in the placement of EBG are fabricated producing a notch centered at 5.19 GHz (wireless local area network (WLAN)). A dual notch (5.16 and 8.24 GHz (satellite communication)) UWB filter is also fabricated with two different unit cell EBGs'. Switchable and tunable notch band UWB filters are proposed.