Compact dielectric resonator antenna for WLAN applications

A new dielectric resonator antenna (DRA) with reduced size for WLAN applications is presented. The proposed antenna consists of a rectangular dielectric resonator with partial vertical and horizontal metallisations which is coupled to a microstrip line through a rectangular aperture in the ground plane. A 9.6 reduction coefficient is obtained compared to the volume of an equivalent isolated DRA. An experimental 12% bandwidth is also achieved in spite of the compact size.     

Microstrip termination effects on dielectric resonator filters

The effect of microstrip termination on the noise figure and insertion loss performance of dielectric resonator filters has been investigated both theoretically and experimentally. Radiation loss from open- and short-circuited dielectric resonator coupling lines has been determined. It is shown that the use of short-circuited coupling lines results in significant improvements in the performance of the filter. The improvement increases as frequency increases.     

Precision measurement of coupling between microstrip and TE01 mode dielectric resonator

The coupling between a microstrip transmission line and a dielectric resonator with a relative dielectric constant of 80 has been measured as a function of the distance between the resonator and the microstrip. Precision measurement involves the TRL de-embedding procedure, and data fitting to a fractional linear transformation on a complex plane. A comparison is made of covered and uncovered resonators, demonstrating the influence of radiation     

Systematic evaluation and analysis for 60-GHz dielectric resonatorscoupled to a microstrip line on a GaAs substrate

This paper presents the first systematic evaluation and analysis of 60-GHz-band TE_01δ-mode cylindrical dielectric resonators coupled to a microstrip line on a GaAs substrate. The loss components of the unloaded Q are analyzed using simple numerical techniques. The distance between the resonator center and the microstrip line which gives the maximum coupling coefficient is found to be approximately 3/5 of the resonator radius, whose ratio is almost constant for all practical cases. The temperature characteristics are also demonstrated and the origins of temperature dependences of the unloaded Q and the coupling coefficient are discussed. An equivalent circuit model for the dielectric resonator coupled to the microstrip line is presented, whose element parameters can express the dependences of the resonant frequency, the unloaded Q, and the coupling coefficient on the structural parameters and the temperature     

新型X波段圆极化介质谐振器天线

提出了一种工作于X波段的新型圆极化矩形介质谐振器天线。该天线是一块矩形介质谐振器嵌入到介质基板中并通过U型微带线激励。天线的接地面采用缺陷地的结构,可以通过调节该缺陷地对角的大小来产生2个正交模式实现圆极化,有效解决了一些圆极化天线馈电网络复杂的缺点。所设计天线的阻抗带宽为8.88~10.22 GHz。天线的轴比带宽为9.56~9.92 GHz,可应用于卫星广播、航空无线电导航业务和无线电定位。     

Circular polarised cylindrical dielectric resonator antenna

A circular polarised cylindrical dielectric resonator antenna excited using a simple microstrip feed line is reported. The experimental results of the resonant frequency, radiation pattern, boresight axial ratio, gain, unloaded Q-factor, impedance bandwidth and radiation efficiency are presented     

Optimum dielectric overlay thickness for equal even- and odd-mode phase velocities in coupled microstrip circuits

An optimum dielectric overlay thickness was found for achieving the equal even- and odd-mode phase velocities in coupled microstrip lines. The theoretical results were calculated based on a variational method. Coupled linear resonator structures were used to measure both the even- and odd-mode effective dielectric constants and the results agree very well with the theory. A directional coupler, built with overlay, has greater than 60 dB isolation as compared with 20 dB isolation for an uncompensated coupler.<>     

A microstrip phase-trim device using a dielectric overlay

A design procedure is given for a microstrip phase-trim device using a dielectric overlay on a conventional microstrip line. The physical operation of the device is based on the change in the effective dielectric constant of the microstrip line caused by the presence of the dielectric layer on top of the microstrip line. The amount of phase trim produced by the device can be selected by the appropriate choice of dielectric constant, height, and length of the dielectric overlay. An approximate expression is given for the effective dielectric constant of the microstrip line as a function of the dielectric constant and height of the overlay. Measured results at 10 GHz are compared with predicted performance     

Stabilisation of a W-band microstrip oscillator by a dielectric resonator

The effect of temperature on the performance of a dielectric resonator compensated W-band impatt diode microstrip oscillator is shown to be quite small. The frequency change was about 2 MHz/°C as compared to the uncompensated oscillator's 10 MHz/°C. The design of the oscillator is presented and the resonator used was a cuboid of temperature compensated barium nonatitanate.     

Comparative study on the mutual coupling between different sized cylindrical dielectric resonators antennas and circular microstrip patch antennas

A systematic comparative study on the mutual coupling (S/sub 21/) between dielectric resonator antennas (DRAs) and microstrip patch antennas is presented. The mutual coupling between two cylindrical probe-fed DRAs is studied for different radius to height (a/L) ratios. It is found that the mutual coupling decreases with the radius to height ratio. Comparison between mutual coupling of probe-fed cylindrical DRAs and circular microstrip patch antennas with different dielectric substrates are also studied. The mutual coupling between DRAs is 2 dB stronger than between microstrip patch antennas when the patch is etched on a dielectric substrate of a dielectric constant close to the permittivity of the DRA. The mutual coupling of the circular patch antennas reduces with the dielectric constant of the substrate.     

A multicomposite, multilayered cylindrical dielectric resonator forapplication in MMIC's

A method, based on the mode matching technique, to study various resonant modes of a multicomposite, multilayered cylindrical dielectric resonator is presented. Dielectric sphere and cone resonators placed in practical environments are investigated. The calculated resonant frequencies show very good agreement compared with the numerical results of the finite difference method for the spherical resonator and with the measured values for the conical resonator, respectively. Experimental investigations show that the conical resonator can be coupled to a circular microstrip line, which has small size at high frequencies and may be integrated together with an oscillator     

Design and analysis of multisegment dielectric resonator antennas

The multisegment dielectric resonator antenna (SDRA) has previously been developed to significantly enhance the coupling to a microstrip line. The MSDRA greatly facilitates the integration with a printed feed distribution network for use in a large array environment. The thickness and permittivity of the dielectric insert of the MSDRA can be adjusted to match the element impedance to that of the feed line. A detailed study of the effects of varying the dielectric insert parameters was carried out and useful guidelines are presented for the design of MSDRAs     

Wideband dielectric resonator antenna excited by cavity-backed circular aperture with microstrip tuning fork

A wideband dielectric resonator antenna excited by a circular aperture is investigated experimentally. The aperture is coupled by a microstrip feedline with a microstrip fork-like tuning stub. A backing cavity is placed beneath the stub to block undesirable backside radiation. The return loss, field pattern, and antenna gain of the proposed configuration were measured, and the results are compared with those without the backing cavity.     

Lagrangian formulation of a linear microstrip resonator: theory andexperiment

A Lagrangian approach is used to formulate the electromagnetic scattering properties of a linear microstrip resonator. The resonator design includes a center microstrip separated from the source and output loads by dielectric gaps. The gaps of the resonator are represented by capacitively coupled π-networks whereas the Lagrangian is formulated in the discrete limit such that the equations of motion transform into two boundary conditions, relating the waves on the two sides of the gap in terms of two lumped capacitors. The effective capacitors expressed in the boundary conditions are actually the capacitances experienced by the even and odd excitation modes of the system, respectively. The calculations, therefore take into account the characteristic impedance, effective dielectric constant, conductivity of the metal strip and the ground plane, and dielectric loss tangent of the dielectric material. In addition, the two capacitor values representing the gaps are included in a consistent manner with the above parameters by the application of the Lagrangian formulation. Calculated and measured reflection coefficients of linear microstrip resonators are compared, and general agreement is found between theory and experiments     

Unloaded quality factor measurement for MIC dielectric resonator applications

The unloaded quality factor of a dielectric resonator, in the MIC environment, and magnetically coupled to a terminated microstrip line, is estimated by using a network analyser. It is sufficient to compute the relative bandwidth of the interception between the reflection coefficient locus and the R ? 1 = ±jX arcs.     

Efficient analysis of microstrip-coupled nonradiative dielectric(NRD) resonators for hybrid integrated circuits

Nonradiative dielectric (NRD) resonators have been recently known as excellent stabilizing components for the design of a new class of oscillators based on hybrid integration of planar circuits and NRD-guides. However, an accurate characterization of such a component is needed in order to develop efficient computer-aided-design programs. In this paper, a hybrid planar integrated circuit comprising an NRD resonator is accurately modeled and is coupled to input and output planar microstrip circuits by means of long slots located on the top ground plane of the NRD structure. A reciprocity approach is used to solve the coupling problem between the resonator and microstrip lines. A modal expansion of the field equations has been applied to the NRD resonator in obtaining its rigorous field expressions. Finally, a transmission-line analysis is proposed for the structure, and scattering parameters have been calculated for different slot positions. Results are discussed for various parametric effects on coupling and Q-factor characteristics     

Modified method for the analysis and design of microwave bandpass filters containing dielectric resonators

High-Q dielectric resonators having remarkable advantages such as compactness, light weight, temperature stability, and low cost have become very valuable elements for various microwave circuits. A modified Itoh and Rudokas model is proposed to analyse the field distribution and the coupling relations between dielectric resonators and microstrip lines based on the analysis results, a convenient procedure for designing microwave filters containing parallel coupled dielectric resonators is presented. Two experimental dielectric resonator filters are also fabricated to verify the calculation and the design procedure. The outcome demonstrates that the procedure provides good accuracy and saves design time.     

Spectral Domain Analysis of Elliptic Microstrip Disk Resonators

The elliptic microstrip disk resonator in an open microstrip configuration is analyzed using the spectral domain technique under quasi-static approximation. The normalized value of capacitance is presented as a function of the ratio of substrate thickness and semimajor axis of the elliptic disk resonator for different values of eccentricity. The fringing field effects associated with the structure are quantitatively assessed in terms of effective normalized semimajor axis. The resonator frequencies computed incorporating this effect are in good agreement with the experimental values reported in the literature. Results for various dielectric constants are also included.     

Broadband cylindrical dielectric resonator antenna excited by modified microstrip line

The impedance bandwidth of a high permittivity cylindrical dielectric resonator antenna excited by a microstrip line was significantly improved by modifying the feed geometry. The 10 dB return loss bandwidth is enhanced from 12 to 26% without much affecting the gain and other radiation properties of the antenna. Good agreement has been observed between the predicted and measured results.     

Novel temperature-stable ceramics for microwave dielectric resonators and microstrip substrates

Ceramics comprising homogeneous single-phase zirconate solid solutions of suitable composition have very low temperature coefficients of permittivity, low-frequency permittivities of 30?40 and low losses. Dielectric resonators give Q values up to 4000 and permittivities of 28?35 at 4?5 GHz. The effective permittivity measured on a microstrip ring resonator on a calcium-zirconate substrate shows the dispersion predicted theoretically; the effective permittivity increases from 17 to 23 over the frequency range 1?12 GHz and gives 28.1 as the calculated real value of the permittivity of the substrate. The measured Q value of 200 indicates negligible dielectric losses compared with the I2R losses.