The solid-state sintering route was employed for the production of (1-x)Bi2(Li0.5Ta1.5)O7-xTiO2 (x = 0, 0.02, 0.04, 0.06, 0.08) ceramics. The phase, microstructure and microwave dielectric properties ...of each ceramic composition were determined via X-ray diffraction, scanning electron microscopy and Haki Colmon resonator technique, respectively. The dielectric constant, tanδ and AC conductivity were also determined for the composition of x = 0.04. The TiO2 addition developed new phases of Bi3Ti4O12 and Bi3TaTiO9 for x = 0.04 along with Bi2(Li0.5Ta1.5)O7 phase which disappeared for x = 0.08. The τf of Bi2(Li0.5Ta1.5)O7 was tuned through zero by TiO2 addition and good microwave dielectric properties εr~67.2, Qufõ13,767 GHz and τf ~ −1.45 ppm/°C can be obtained for the composition of x = 0.04 sintered at 1050 °C for 2 h. This ceramic composition is a suitable candidate for 5G cellular base station resonator application.
Photoacoustic cell is an essential core component in a photoacoustic spectroscopy (PAS) gas sensing system, which is used to enhance and measure the absorption-induced acoustic signal. For certain ...applications, miniaturized photoacoustic cells with tiny inner volumes are preferred to reduce gas consumption. In this article, a photoacoustic cell with inner volume of only 0.5 mL is designed based on differential Helmholtz resonators (DHRs). After an initial simulation stage by the finite element analysis (FEA) based on COMSOL software, the photoacoustic cell is fabricated by 3-D printing. To facilitate laser power coupling, a micro fiber collimator is customized and integrated with photoacoustic cell to guide the laser beam. New concept of photoacoustic detector is proposed and integrated to a PAS system for trace acetylene detection. As a result, an excellent linearity of 0.99999 is achieved in the concentration range of 0-5000 ppm. A <inline-formula> <tex-math notation="LaTeX">1\sigma </tex-math></inline-formula> sensitivity of 0.13 ppm is measured within a response time of 10 s, the minimum detection limit (MDL) is evaluated to be 0.3 ppm. Allan deviation analysis indicate that the detection sensitivity can be improved to 16.6 ppb at an integration time of 910 s.
In this brief, compact multi-channel bandpass filters and diplexers are proposed based on dual-coaxial resonators. One coaxial resonator is embedded into the other to form a dual-mode resonator ...without increasing the size, where the resonant section of one resonator acts as the shielding cavity of the other one. In this way, the two modes of the dual-coaxial resonator are ideally isolated and can be controlled independently. By properly designing the feeding and coupling structures between resonators, the two modes in one dual-coaxial resonator can be excited and coupled to construct different filter channels without influencing each other. Accordingly, multi-channel filters are realized. For verification, a dual-channel and a triple-channel filters are presented. Moreover, the filter channels in a dual-channel filter can be applied to design the diplexer, resulting in a compact size. Experimental results are presented with good in-band responses and high isolation.
This paper is focused on the analysis of coplanar waveguides (CPWs) loaded with circularly shaped electric-LC (ELC) resonators, the latter consisting of two coplanar loops connected in parallel ...through a common gap. Specifically, the resonator axis is aligned with the CPW axis, and a dynamic loading with ELC rotation is considered. Since the ELC resonator is bisymmetric, i.e., it exhibits two orthogonal symmetry planes, the angular orientation range is limited to 90°. It is shown that the transmission and reflection coefficients of the structure depend on the angular orientation of the ELC. In particular, the loaded CPW behaves as a transmission line-type (i.e., all-pass) structure for a certain ELC orientation (0°) since the resonator is not excited. However, by rotating the ELC, magnetic coupling to the line arises, and a notch in the transmission coefficient (with orientation dependent depth and bandwidth) appears. This feature is exploited to implement angular displacement sensors by measuring the notch depth in the transmission coefficient. To gain more insight on sensor design, the lumped element equivalent-circuit model for ELC-loaded CPWs with arbitrary ELC orientation is proposed and validated. Based on this approach, a prototype displacement sensor is designed and characterized. It is shown that by introducing additional elements (a circulator and an envelope detector), novel and high precision angular velocity sensors can also be implemented. An angular velocity sensor is thus proposed, characterized, and satisfactorily validated. The proposed solution for angular sensing is robust against environmental variations since it is based on the geometrical alignment/misalignment between the symmetry planes of the coupled elements.
A differentially fed duplex filtering dielectric resonator antenna (DFDRA) is proposed. This DFDRA combines the functions of the duplexer, the filter and the antenna into one highly integrated ...multifunctional module. A dual-mode substrate integrated waveguide (SIW) cavity working as the common feeding structure operates at two orthogonal modes at the lower and higher channel and is differentially fed by two pairs of differential input ports. The DRA working as the common radiation element operates at two orthogonal modes at two channels respectively and is excited by two cross slots etched on the top of the SIW cavity. High-isolation between the two channels is realized due to the two pairs of orthogonal operating modes of the DRA and SIW cavity. Measured results show that the balanced DFDRA can operate with differential mode 10dB impedance bandwidth of 2.7% (5.07-5.21 GHz) and 2.6% (5.72-5.87 GHz), the peak realized gains of 4.6-4.9 dBi and 4.8-5.1 dBi for two channels respectively. The isolation between the lower and higher channels is greater than 75dB. Good common mode suppression is realized.
A novel stacked dielectric resonator antenna (DRA) using the higher-order TE(z)-mode cluster to realize bandwidth diversity is reported for the first time. A significant difference in the ...permittivity between the upside and downside content is the essential condition for higher-order TE(z) modes excitation and manipulation. The fundamental TE 111 (y) mode generated from the whole mass, as well as three higher-order TE 1α1 (y) (α=2,4,6) modes generated from the upside content, are excited simultaneously, resulting in a flexible bandwidth performance. The four modes are verified and analyzed through theoretical calculation. Further parametric study reveals their unique manipulation for giving a desired bandwidth. To demonstrate our proposal, one of the wideband prototypes is fabricated with the upside and downside materials chosen as water and K9 glass, respectively. The DRA is differential-fed by a pair of L-shaped strips. The measured results show that a broadside radiation pattern with a maximum gain of 8.82dBi can be achieved over a wide bandwidth of 65.4% from 1.75 GHz to 3.45 GHz.
In this communication, a compact three-port pattern- and polarization-diversity rectangular dielectric resonator antenna (DRA) is investigated. The antenna is designed based on three TE modes, TE x ...δ11 mode, asymmetric TE y 1δ1 mode, and the presented quasi-omnidirectional mode, symmetrical TE y 1δ1 mode. The radiation mechanism of the presented symmetrical TE y 1δ1 mode is revealed by the theory of array and the geometric theory of diffraction. The asymmetric and symmetrical TE y 1δ1 modes are supported by different boundary conditions. Based on the field-distribution difference between the two modes, artificial boundary made of metal strips is electroplated on a portion of the side of the DRA to excite the symmetric and asymmetric TE y 1δ1 modes simultaneously. For verification, a three-mode diversity DRA is designed at 5.8 GHz. The TE x δ11 , asymmetric, and symmetric TE y 1δ1 modes are excited by differential probes, slot in the center and slots at the periphery, respectively. The overlapping 10-dB bandwidth of the three ports covers from 5.7 to 5.9 GHz. The envelope correlation coefficients and mean effective gain ratios are lower than 0.13 and 1.5 dB, respectively.
A novel substrate integrated waveguide (SIW) cavity-backed self-triplexing slot antenna, consisting of a hybrid SIW cavity resonator is proposed for tri-frequency operation. The hybrid cavity ...resonator is an amalgamation of a half-mode circular and half-mode rectangular SIW cavity resonator. A radiating slot is etched on its top surface, which produces three distinct resonant frequencies (5.57, 7.17 and 7.65 GHz) when it is excited by three microstrip lines. The lower band around 5.57 GHz is achieved due to a half-mode circular cavity resonator, when the corresponding microstrip line is excited. On the other hand, remaining two bands around 7.17 and 7.65 GHz are achieved due to half-mode rectangular cavity resonator when excited by the corresponding microstrip lines. The experimental isolation level between any two feed lines is better than 20 dB, which helps to introduce the self-triplexing phenomenon. Moreover, the proposed design is realised on a single-layered copper-laminated dielectric substrate, maintaining planar configuration.
Here we demonstrate the direct optical modulation of RF radiation patterns in a high permittivity (ϵ ∼ 80) cylindrical dielectric resonator antenna (DRA) loaded with a silicon superstrate. A hybrid ...mode (HEM 11δ ) is excited via microstrip. The far-field radiation pattern is characterized with an angle-dependent RF radiation measurement setup, and the near-field is measured using an optically induced conductance technique. We show that when light is incident upon the superstrate, the optically generated electron-hole-pairs (EHPs) in the silicon superstrate modulate and inhibit the far-field RF radiation. We compare our experimental results with finite element method simulations and show excellent agreement. Finally, we perform a proof of principle experiment to mix optically modulated signals with the baseband RF far-field radiation, paving the pathway for future free space optical/RF hybrid communications setups and modulation schemes as well as phase circuitry-free RF beam shaping and steering.
A compact quasi-isotropic dielectric resonator (DR) antenna (DRA) with filtering response is first investigated in this communication. The cylindrical DRA is fed by a microstrip-coupled slot, ...exciting in its <inline-formula> <tex-math notation="LaTeX">{\text {HEM}}_{11 \delta } </tex-math></inline-formula> mode which radiates like a magnetic dipole. A small ground plane is used for this DRA and it radiates like an electric dipole. The combination of the two orthogonal dipoles leads to a quasi-isotropic radiation pattern, with gain deviation as low as 5.8 dB in the 360° full space. To integrate the filtering function, the microstrip feed-line and the ground plane are turned upside down, and further two stubs with different lengths are used together to excite the DR. Due to the different loading effects of the feeding stubs, two resonances of the DR <inline-formula> <tex-math notation="LaTeX">{\text {HEM}}_{11 \delta } </tex-math></inline-formula> mode are excited in the passband, effectively enhancing the bandwidth of DRA (<inline-formula> <tex-math notation="LaTeX">\varepsilon _{r} = 20 </tex-math></inline-formula>) to 7%. Furthermore, two controllable radiation nulls are generated by the DR loaded microstrip feed-line, bringing about high frequency selectivity at the edges of the passband and a quasi-elliptic bandpass response. For demonstration, a prototype operating at 2.4 GHz was fabricated and tested; reasonable agreement is obtained between the simulated and measured results.
