Showing papers on "Dielectric resonator antenna published in 1994"
TL;DR: In this paper, a comprehensive review of the modes and the radiation characteristics of open dielectric resonators (DRs) of different shapes, such as cylindrical, spherical, and rectangular, is presented.
Abstract: Open dielectric resonators (DRs) offer attractive features as antenna elements. These include their small size, mechanical simplicity, high radiation efficiency due to no inherent conductor loss, relatively large bandwidth, simple coupling schemes to nearly all commonly used transmission lines, and the advantage of obtaining different radiation characteristics using different modes of the resonator. In this article, we give a comprehensive review of the modes and the radiation characteristics of DRs of different shapes, such as cylindrical, cylindrical ring, spherical, and rectangular. Further, accurate closed form expressions are derived for the resonant frequencies, radiation Q-factors, and the inside fields of a cylindrical DR. These design expressions are valid over a wide range of DR parameters. Finally, the techniques used to feed DR antennas are discussed. © 1994 John Wiley & Sons, Inc.
861 citations
TL;DR: A tuned transmission line resonator developed in theory and in practical design for the clinical NMR volume coil application at 4.1 tesla has been demonstrated to be a function of the electromagnetic properties of the load itself and uncompromised high field advantages of signal‐to‐noise and spatial resolution.
Abstract: A tuned transmission line resonator has been developed in theory and in practical design for the clinical NMR volume coil application at 4.1 tesla. The distributed circuit transmission line resonator was designed for high frequency, large conductive volume applications where conventional lumped element coil designs perform less efficiently. The resonator design has made use of a resonant coaxial cavity, which could be variably tuned to the Larmor frequency of interest by tunable transmission line elements. Large head- and body-sized volumes, high efficiencies, and broad tuning ranges have been shown to be characteristic of the transmission line resonator to frequencies of 500 MHz. The B1 homogeneity of the resonator has been demonstrated to be a function of the electromagnetic properties of the load itself. By numerically solving Maxwell's equations for the fully time-dependent B1 field, coil homogeneity was predicted with finite-element models of anatomic structure, and inhomogeneities corrected for. A how-to exposition of coil design and construction has been included. Simple methods of quadrature driving and double tuning the transmission line resonator have also been presented. Human head images obtained with a tuned transmission line resonator at 175 MHz have clearly demonstrated uncompromised high field advantages of signal-to-noise and spatial resolution.
402 citations
TL;DR: In this paper, a formulation based upon the method of moments (MoM) is presented for the computation of input impedance of dielectric resonator antennas, which consists of axially symmetric D resonators fed by thin wire elements.
Abstract: A formulation based upon the method of moments (MoM) is presented for the computation of input impedance of dielectric resonator antennas. The class of antennas modeled by this method consists of axially symmetric dielectric resonators fed by thin wire elements. The formulation is general in that the feed structure may be interior or exterior to the dielectric resonator. To demonstrate the utility of this technique, parametric studies are performed on a cylindrical dielectric resonator antenna (CDRA) operating at frequencies that excite the important HEM/sub 11/ resonator antenna mode. The integrity of this technique is established both experimentally and numerically. >
175 citations
TL;DR: Low profile rectangular dielectric resonator antennas, fabricated out of a very high permittivity material ( epsilon /sub r/=100), were reported in this paper. But their performance was limited to 3% bandwidth.
Abstract: Low profile rectangular dielectric resonator antennas, fabricated out of a very high permittivity material ( epsilon /sub r/=100) are reported. An antenna having a height of approximately 0.026 lambda /sub 0/ and a bandwidth of 3% is demonstrated.<
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160 citations
TL;DR: In this paper, the effect of an air gap on the input impedance and resonance frequency of a cylindrical dielectric resonator (CDR) antenna operating in the TM01 mode as a function of the DIC constant was studied.
Abstract: The results of a numerical study pertaining to the effect of an air gap on the input impedance and resonance frequency of a cylindrical dielectric resonator (CDR) antenna operating in the TM01 mode as a function of dielectric constant are presented. The CDR resides on a conducting ground plane and is excited by a coaxial probe through the bottom of the ground plane. Some of the numerical results are validated experimentally.
127 citations
TL;DR: In this article, the authors measured the radiation efficiency of dielectric resonator antennas in the dominant hybrid (HE/sub 11/spl delta) mode and showed that the conduction losses are quite small.
Abstract: Radiation efficiency (due to conduction and dielectric losses) of dielectric resonator antennas has been measured. Results show that for dielectric resonators placed directly on a metallic plane, the conduction losses are quite small. A radiation efficiency of >98% has been measured for dielectric resonator antennas operated in the dominant hybrid (HE/sub 11/spl delta//) mode. Theoretical considerations show scope of further improvement in the radiation efficiency by choosing optimum resonator parameters. >
127 citations
TL;DR: In this paper, a circularly polarised dielectric resonator antenna is reported, which is obtained by exciting the two orthogonal HE/sub 11 delta / modes of a cylindrical ring dielectrics resonator in phase-quadrature.
Abstract: A circularly polarised dielectric resonator antenna is reported. The circular polarisation is obtained by exciting the two orthogonal HE/sub 11 delta / modes of a cylindrical ring dielectric resonator in phase-quadrature. Measured results show that the antenna has an axial ratio of less than 3 dB over a beam width of 100 degrees with a minimum value of approximately 0.5 dB in this range. >
86 citations
TL;DR: In this paper, the effect of an air gap surrounding the feed probe of a cylindrical dielectric resonator (CDR) antenna on its input impedance and resonance frequency was investigated.
Abstract: Results of an experimental study pertaining to the effect of an air gap surrounding the feed probe of a cylindrical dielectric resonator (CDR) antenna on its input impedance and resonance frequency are presented. The antennas under consideration consist of a CDR positioned on a conducting ground plane and fed by a coaxial probe to excite either the TM/sub 01/ or HEM/sub 11/ antenna modes.
85 citations
TL;DR: The collapse of a continuum of transverse modes in a self-imaging ring resonator that is photorefractively pumped is demonstrated and the resulting localized mode has an arbitrary transverse location.
Abstract: We demonstrate the collapse of a continuum of transverse modes in a self-imaging ring resonator that is photorefractively pumped. The resulting localized mode has an arbitrary transverse location. The mode collapse results from placing saturable photorefractive gain and loss media in spatially conjugate resonator planes. The transverse position of the localized mode is unstable under small cavity misalignments, and it drifts across the transverse aperture while retaining its spatial form.
78 citations
Patent•
01 Jul 1994
TL;DR: In this article, a cylindrical cavity consisting of a dielectric resonator (DR) connected to a metal tuning screw is described, where the tuning screw penetrates into a hole made in axial direction in the upper wall of the cavity.
Abstract: Tunable resonator consisting of a cylindrical cavity containing a cylindrical dielectric resonator (DR) connected to a metal tuning screw by means of a cylindrical dielectric spacer placed between the screw and the DR and connected rigidly to the latter. The tuning screw penetrates into a hole made in axial direction in the upper wall of the cavity. Said wall exhibits on the edge of the hole a toroidal extension toward the interior of the cavity. As concerns tuning, starting from a condition in which resonance frequency fr of the resonator is minimal, i.e. when the DR is at the centre of the cavity, a rotation of the metal tuning screw which results in approach of the DR to the toroidal extension produces a significant increase in fr. There are also described microwave filters comprising multiple resonators which are the object of the present invention coupled together by means of irises.
61 citations
TL;DR: In this paper, the characteristics of center probe-fed cylindrical dielectric ring resonator antennas with an air gap were studied both theoretically and experimentally, and the return loss of the TM01δ mode was evaluated by using the finite-difference time-domain (FDTD) method and the result agrees well with the measured data.
Abstract: The characteristics of centre probe-fed cylindrical dielectric ring resonator antennas with an air gap are studied both theoretically and experimentally. The return loss of the TM01δ mode is evaluated by using the finite-difference time-domain (FDTD) method and the result agrees well with the measured data. It is demonstrated that the impedance bandwidth can be improved by adjusting the air-gap spacing.
Patent•
30 Jun 1994TL;DR: A plane antenna suitable for space applications in particular comprises a passive resonator coupled to a feedline by a looped slot as discussed by the authors, where the resonator is coupled to the feed line by a linear loop.
Abstract: A plane antenna suitable for space applications in particular comprises a passive resonator coupled to a feedline by a looped slot.
TL;DR: In this article, an experimental investigation of a novel ferrite resonator antenna has been carried out, where the ferrite antenna was subjected to a static magnetic bias field, applied in directions parallel and perpendicular to the antenna length.
Abstract: An experimental investigation of a novel ferrite resonator antenna has been carried out. The ferrite antenna was subjected to a static magnetic bias field, applied in directions parallel and perpendicular to the antenna length. The effects on the resonance frequency of the antenna when subjected to this bias were investigated. A maximum frequency shift of 8% above (parallel bias) or 8% below (perpendicular bias) the unbiased resonance frequency was achieved. >
TL;DR: In this article, the authors proposed an all-fiber compound ring resonator with two rings: a primary one that serves as a resonator and a secondary one serving as a filter, which increases the free spectral range by choosing the fiber lengths in the compound ring cavity.
Abstract: The new all-fiber compound ring resonator has two rings: a primary one that serves as a resonator, and a secondary one that serves as a filter. The main contribution of this resonator is to increase the free spectral range by choosing the fiber lengths in the compound ring cavity. This resonator with a large free spectral range can be readily used as a doped fiber laser. The optimum resonant conditions of the resonator are discussed by using an equivalent model and by the transfer matrix method. The frequency responses of the output and of the circulating intensities are given. Mode suppression by the vernier effect is demonstrated. Comparison with a fiber Fox-Smith resonator is also presented. >
TL;DR: In this paper, a capacitively loaded microstrip loop resonator has been developed, which has not only a smaller size but also a higher Q factor as compared with the conventional half-wavelength resonator.
Abstract: A novel capacitively loaded microstrip loop resonator has been developed It has been shown theoretically and experimentally that the novel resonator has not only a smaller size, but also a higher Q factor as compared with the conventional half-wavelength resonator
TL;DR: In this article, several resonator miniaturization techniques, including multimode reuse of space, the use of supplementary energy resonators (so called active resonator) with a enhanced apparent Q value, the low-stored energy filter technique using transversal filters, and the reduced size resonators using mirror image technique, are described.
Abstract: The unloaded Q of a fixed frequency cavity resonator which is filled with low-loss dielectric material is proportional to the cubic root of its volume due to the intensified current loss in the cavity wall. Utilization of such materials to reduce resonator size must be evaluated by taking this volume dependency into account. This paper describes several resonator miniaturization techniques, including the multimode reuse of space, the use of supplementary energy resonators (so called active resonator) with a enhanced apparent Q value, the low-stored-energy filter technique using transversal filters, and the reduced size resonators using mirror image technique. >
Patent•
24 Mar 1994TL;DR: In this paper, a laminated dielectric resonator is used to reduce the length of the strip line of the resonator and reduce the resonant frequency, which leads to further reduction of the length.
Abstract: In a laminated dielectric resonator, twomo strip line is formed and resonant frequency is lowered. Accordingly, the length of the resonator is reduced, and the length of the strip line becomes shorter than one fourth of the wavelength with the lowered resonant frequency, which leads to further reduction of the length of the resonator. By lowering the resonant frequency, dielectric material with less relative permittivity can be used, with a result of resonator with high unloaded Q and excellent temperature characteristic. Further, at least one coupling electrode is formed as external or internal electrode to compose a capacitor together with a second strip line, and a laminated dielectric resonator is connected to an external circuit via the coupling electrode. A dielectric filter such as band pass filter, band elimination filter is so composed that the dielectric resonators are cascade-connected to one another. In the thus constructed dielectric filter, external coupling capacitors are unnecessary, reducing the number of parts and facilitating the manufacturing process. Thus, a small-sized, low-cost dielectric filter is attained.
Patent•
09 Sep 1994
TL;DR: In this paper, a transmission line resonator is disclosed which has a resonance frequency that is electrically controllable by control voltage, and a reactive circuit is coupled in parallel between two coupling points on the transmission line resonance.
Abstract: A transmission line resonator is disclosed which has a resonance frequency that is electrically controllable by control voltage. A reactive circuit is coupled in parallel between two coupling points on the transmission line resonator. The reactive value of the reactive circuit is changed by the control voltage. The reactive circuit can be inductive or capacitive. The control voltage can switch the reactive circuit in parallel with a part of the transmission line resonator between the coupling points, or can control the capacitance value of a capacitance diode disposed in parallel with a part of the transmission line resonator between the coupling points.
Patent•
27 Jan 1994TL;DR: In this article, a cylindrical dielectric resonator (40) is supported by a spacer (58) above a ground plane (14) and dielectrical substrate (12), and a first microstrip transmission line includes a strip conductor (22) coupled at one end to the coupled 0° port, and extending parallel to a tangent to the edge of the resonator at a central plane (44), terminating in an open-circuit (226).
Abstract: A notch filter includes a directional coupler (16) with an input port (17a), coupled output port (17b), coupled 0° (17d) and direct 90° (17c) ports. A cylindrical dielectric resonator (40) is supported by a spacer (58) above a ground plane (14) and dielectric substrate (12). A first microstrip transmission line includes a strip conductor (22) coupled at one end to the coupled 0° port, and extending parallel to a tangent to the edge of the resonator at a central plane (44), terminating in an open-circuit (226). A second transmission line includes a strip conductor (24) coupled to the direct 90° port (17c) and extending parallel to the first transmission line, on the other side of the resonator. The first and second transmission lines each have an electrical length λ/4 between the central plane (44) and their open-circuit terminations, to reflect a high current to the plane. The high current represents maximum transmission line current, for maximizing coupling to the resonator. An offset metal plunger generates a higher-order mode, which is combined with the fundamental to improve rejection at the notch.
TL;DR: In this article, a rectangular dielectric resonator antenna fed by a microstrip line through an aperture on the ground plane is analyzed using the finite-difference time-domain (FDTD) method.
Abstract: A rectangular dielectric resonator (DR) antenna fed by a microstrip line through an aperture on the ground plane is analysed using the finite-difference time-domain (FDTD) method. The calculated return losses were compared with experiment and reasonable agreement was obtained. The effects of the slot width on the return loss are also studied.
Patent•
10 Oct 1994TL;DR: The dielectric notch filter as mentioned in this paper is a high-frequency filter that includes an impedance matching element connected to the ground conductor and the transmission line in parallel with the resonator.
Abstract: The dielectric notch filter of the invention includes: a transmission line for transmitting a high-frequency signal; input and output terminals provided at both ends of the transmission line; a ground conductor for supplying a ground potential; and a dielectric resonator connected to the ground conductor and the transmission line. The dielectric notch filter further includes an impedance matching element connected to the ground conductor and the transmission line in parallel with the dielectric resonator. The dielectric resonator includes: a cavity connected to the ground conductor; a dielectric block provided in the cavity; a coupling device coupled with an electromagnetic field produced in the cavity; and a coupling adjusting line for connecting the coupling device to the transmission line and for adjusting the degree of electromagnetic coupling.
Patent•
11 May 1994
TL;DR: In this article, a plurality of dual mode, dielectric resonator loaded cavity filters are coupled to a radiator of an array antenna, such as a phased array antenna by a thin annular, electrically conductive ring disposed on a resonator surface facing the corresponding radiator of the antenna.
Abstract: A plurality of dual mode, dielectric resonator loaded cavity filters may be coupled to respective ones of a plurality of radiators of an array antenna, such as a phased array antenna. Each of the filters is provided with a thin annular, electrically conductive ring disposed on a resonator surface facing the corresponding radiator of the antenna. The ring greatly increases the coupling of electromagnetic power for circularly and linearly polarized waves between the filter and the radiator for radiation of the power from the radiator into space, as well as during reception of radiation from outer space. The filter is operative also, if desired, to provide such coupling of electromagnetic power to a waveguide, as well as directly into the external environment. The ring may be located at the opening of the cavity through which the power is coupled between the filter and the radiator or the waveguide or the empty space.
Patent•
19 Jul 1994
TL;DR: In this article, a reentrant dielectric ceramic resonator and filters incorporating a plurality thereof are suitable for use in mobile and portable radio transmitting and receiving devices, where the resonator is constructed by a cylindrical hole extending partially from the top surface toward the bottom surface.
Abstract: A re-entrant dielectric ceramic resonator and filters incorporating a plurality thereof are suitable for use in mobile and portable radio transmitting and receiving devices. The inventive re-entrant dielectric ceramic resonator comprises a dielectric means comprised of a dielectric ceramic material having a top surface, a bottom surface and outer side surfaces, the top and bottom surfaces being flat and parallel to each other, the dielectric means further having a cylindrical hole extending partially from the top surface toward the bottom surface thereby forming an inner side surface and an inner bottom surface, the inner bottom surface being flat and parallel to the bottom surface. Furthermore, the top and outer side surfaces of the dielectric means and the inner side and inner bottom surfaces of the cylindrical hole are covered completely with a first conductive material, and the bottom surface of the dielectric means is partially covered with a second conductive material, to thereby form a coupling/tuning capacitor between the first conductive material covering the inner bottom surface and the second conductive material partially covering the bottom surface, whereby the re-entrant dielectric ceramic resonator is constructed.
TL;DR: In this article, a ring resonator topology was developed which exhibits mode suppression characteristics by incorporation of a stepped impedance lowpass filter directly into the ring resonators, which increases the rejection bandwidth of the ring resonance.
Abstract: A novel ring resonator topology was developed which exhibits mode suppression characteristics. The resonator achieves the mode suppression by incorporation of a stepped impedance lowpass filter directly into the ring resonator. Experimental results show that complete suppression of a ring resonator's second mode can be achieved with no increase in circuit size. The topology effectively increases the rejection bandwidth of the ring resonator.
12 Aug 1994
TL;DR: A Gaussian-beam antenna invention comprises a transmitting circuit or a receiving circuit, a resonator consisting of a pair of reflecting mirrors, which consist of a spherical mirror and a planar mirror or two spherical mirrors, and a transmission line which transmits a high-frequency signal between the transmitting circuit and the resonator, one reflecting mirror having an electromagnetic wave coupling region constituted as a circular partially transparent mirror surface region having its center on the optical axis.
Abstract: A Gaussian-beam antenna invention comprises a transmitting circuit or a receiving circuit, a resonator consisting of a pair of reflecting mirrors, which consist of a spherical mirror and a planar mirror or two spherical mirrors, and a transmission line which transmits a high-frequency signal between the aforesaid transmitting circuit or receiving circuit and the resonator, one reflecting mirror of the resonator having an electromagnetic wave coupling region constituted as a circular partially transparent mirror surface region having its center on the optical axis.
TL;DR: In this paper, the broadside fundamental mode of a spherical cap dielectric resonator antenna using aperture coupling was investigated, which offers a wider bandwidth than the previous configuration which used a hemispherical DR antenna.
Abstract: The broadside fundamental mode of a spherical cap dielectric resonator antenna using aperture coupling is investigated. The new configuration offers a wider bandwidth than the previous configuration which used a hemispherical DR antenna. The return loss, radiation characteristics and antenna gain of the new configuration are studied.
20 Jun 1994
TL;DR: In this article, a closed form expression for the radiation Q-factor of a rectangular dielectric resonator (DR) antenna was derived based on replacing the DR by a polarization electric current source.
Abstract: A closed form expression is derived for the radiation Q-factor of a rectangular dielectric resonator (DR) antenna. The method used for determining the Q-factor is based on replacing the DR by a polarization electric current source. Experiments were conducted on dielectric resonators having a value of /spl epsi//sub r//spl ap/38 to verify the accuracy of the expression. The measured results are found to be in fairly good agreement with theory. >
TL;DR: A planar subarray composed of rectangular dielectric resonators fed by a microstrip-line / aperture combination has been devised and investigated in this paper, achieving a 10-dB impedance bandwidth and excellent radiation patterns.
Abstract: A new type of planar subarray composed of rectangular dielectric resonators fed by a microstrip-line / aperture combination has been devised and investigated Good performance has been achieved, including a 10-dB impedance bandwidth of 18% and excellent radiation patterns Results for impedance bandwidth, radiation patterns, and mutual coupling effects are presented © 1994 John Wiley & Sons, Inc
TL;DR: In this article, a probe-fed hemispherical dielectric resonator antenna with a polysilicon-coating was investigated rigorously by using a Green's function formulation.
Abstract: A probe-fed hemispherical dielectric resonator antenna with a dielectric coating is investigated rigorously by using a Green's function formulation. Numerical results for the input impedance at TE111 mode are calculated. It is found that, by coating the dielectric resonator antenna with a dielectric material having a relative permittivity about half that of the dielectric resonator antenna, the impedance bandwidth of the antenna can be significantly improved. This dielectric coating here serves as a transition region between the wave inside the dielectric resonator antenna and the free-space wave, and thus can increase the impedance bandwidth of the antenna. A broadband dielectric resonator antenna can thus be obtained. © 1994 John Wiley & Sons, Inc.
Patent•
08 Mar 1994TL;DR: An antenna of small size is provided in this paper, which is suitable for use with a portable receiver and which does not require provision of a separate matching circuit for the matching circuit.
Abstract: An antenna of small size is provided which can be mass-produced, which is suitable for use with a portable receiver and which does not require provision of a separate matching circuit The antenna includes a plurality of meander antennas printed on at least one dielectric film and satisfying respectively different resonance conditions in a frequency band used by the receiver, at least one dielectric solid cylinder for winding the dielectric film therearound, and a dielectric hollow cylinder for covering the dielectric film wound around the dielectric solid cylinder The individual meander antennas printed on the dielectric film do not make direct electrical contact with each other, and one of the meander antennas connected to a feeder or a helical antenna surrounding the dielectric solid cylinder acts to produce multiple resonance by means of electromagnetic coupling with the other meander antennas, thereby widening the frequency band The dielectric solid cylinder around which the dielectric film is wound or to which the dielectric film is bonded may be replaced by a dielectric polygonal prism such as a dielectric square prism In the antenna, impedance matching with the radio frequency part of the receiver can be satisfactorily achieved, so that an antenna of low cost suitable for portable receivers can be offered