Dielectric materials, devices, and circuits

Dielectric materials are continuing to play a very important role in the microwave communication systems. These materials are key in realization of low-loss temperature-stable resonators and filters for satellite and broadcasting equipment, and in many other microwave devices. High dielectric-constant materials are critical to the miniaturization of wireless systems, both for the terminals and base-stations, as well as for handsets. In this paper, a sequential evolution of the dielectric materials applications in microwave devices will be reviewed. This includes dielectric waveguides, low-loss temperature-stable ceramic materials, dielectric resonators, and filters. The recent advances in the multilayer circuit modules, dielectric antennas, and ferroelectrics are also described     

Temperature-stable low-loss microwave filters using dielectric resonators

Recently developed high-permittivity low-loss temperature-stable dielectric materials have been used as resonators in microwave filters. The resulting low-loss filters possess extremely good temperature stability. Proper design and the use of metal-screw mode suppressors have eliminated the further problem in dielectric-resonator filters of spurious modes just above the passband.     

Application of Dielectric Resonators in Microwave Components

Dielectric resonators are being used in microwave filters and oscillators now that high-dielectric-constant, high-Q, temperature-stable ceramics have been developed. This paper reviews dielectric resonators with emphasis on applications, contains tutorial material, deseribes new 2-, 4-, and 6GHz bandpass filters, and presents several examples of oscillator applications. A complete blbliography to English language publications on dielectric resonators is included.     

Loop-Gap Resonator: A Lumped Mode Microwave Resonant Structure

Loop-gap resonators are newly developed microwave resonant structures with a field configuration that is intermediate between lumped and distributed. Typical characteristic dimensions are of the order of 1/10 of the resonant wavelength, and typical Q's are of the order of 1600-2000 in the frequency range of 1-4 GHz. Data are presented for Q's and frequencies for a series of resonators of various dimensions and compared with theory. Various coupling and frequency tuning techniques are discussed, and results of experiments are reported. Results of preliminary application of the stictire in microwave filters and oscillators are presented. Loop-gap resonators provide a useful design alternative, it is concluded, to dielectric and surface acoustic-wave resonators at low microwave frequencies.     

Direct coupling between two dielectric resonators

The letter deals with a new method of calculation of direct coupling between two dielectric resonators. This method could be used for the design of microwave integrated filters. Comparison between calculated and measured values of this coupling shows good agreement.     

Dual-mode filters with conductor-loaded dielectric resonators

In this paper, a new class of dual-mode microwave filters is presented. These devices use conductor-loaded dielectric resonators with unloaded Q-factors of 2000-8000 achievable in half the physical size of TEM filters and with good spurious performance. The basic properties of this resonator have been examined with the aid of a finite-element field-analysis package. Fundamental design rules for bandpass filters have been developed. A design example of a transmit filter for a ground-signal-metal cellular-radio base station is demonstrated     

Analysis and realization of L-band dielectric resonatormicrowave filters

High power L-band dielectric resonator microwave filters, used in satellite systems because of their good temperature and vibration characteristics, low weight, and size, are discussed. The electromagnetic and electrical parameters of different microwave dielectric resonator structures are computed by means of the two-dimensional and three-dimensional finite element method, which are applied both for free and forced oscillation systems. The design and response evaluation of an elliptic filter using rectangular dielectric resonators excited in their TM₁₁₀ mode are presented     

Microwave Bandpass Filters Containing High-Q Dielectric Resonators

This paper is concerned with dielectric disks used as resonators in microwave bandpass filters. For many years it has been known that modes of resonance occur in isolated dielectric bodies having air boundaries, and that very compact high-Q resonators can be achieved when /spl epsiv/ /sub r/, is high and tan /spl delta/ is low. High-purity TiO/sub 2/ ceramic material, for example, has an /spl epsiv/ /sub r/ about 100, tan /spl delta/ about 0.0001, and Q/sub u/ about 10 000. Practical applications of dielectric resonators have previously been limited by insufficient design information. Formulas are derived for the coupling coefficient between adjacent dielectric-disk resonators within a metal waveguide below cutoff. This metal enclosure is necessary for shielding and to prevent radiation loss. Comparisons between theoretical and experimental coupling coefficient values show very good agreement in each of the three bandpass configurations treated in this paper. Techniques of loop and probe coupling to the end resonators of a multiresonator bandpass filter are discussed and methods of supporting the resonators are suggested. The conclusion is made that microwave dielectric resonators offer important size reductions compared to conventional resonators of similar high Q, but that the center-frequency change of the dielectric resonators as a function of temperature is excessive for many applications. Temperature stabilization is one solution, but preferably a material should be developed having electrical characteristics similar to TiO/sub 2/ ceramic, but with at least an order of magnitude improvement in temperature sensitivity.     

Direct-coupled microwave filters with single and dual stopbands

This paper presents new ideas for the design and implementation of microwave filters with single and dual stopbands. They can be realized with waveguide, coaxial, dielectric resonators, or in a planar technology. The new methods represent an advance over present methods in that the resonators are direct coupled, thus avoiding the need for transmission line phase lengths between resonator stubs that tend to degrade performance due to their dispersion and are difficult to adjust during tuning. Three bandstop (BS) configurations are presented. The first will accommodate even or odd characteristics and also asymmetric responses, although some negative or diagonal cross-couplings will be needed. The second resembles the cul-de-sac configuration for bandpass filters and needs no diagonal or negative couplings even for asymmetric characteristics. The third is an application of the cul-de-sac synthesis technique to dual-band bandstop (DBBS) filters. All these BS designs are very similar to regular bandpass filters in their design and realization. The design of a DBBS filter is presented and compared with an equivalent bandpass filter to demonstrate its advantages. Finally, the simulated and measured results of a fourth-degree BS filter design in the novel cul-de-sac configuration are presented.     

A Frequency-Stabilized Microwave Band-Rejection Filter Using High Dielectric Constant Resonators

The high permittivity dielectric resonator is a low loss microwave filter element whose size is substantiality less than metal waveguide cavities. Temperature stabilizing their resonant frequency increases the applicability of such elements. A temperature compensated 3-section band-rejection filter using dielectric resonators has been fabricated and tested. The measured electrical performance was comparable to metal waveguide filters and the frequency stability for temperature variations was comparable to brass waveguide cavity filters which are not temperature compensated.     

Dielectric Resonator Filters for Application in Microwave Integrated Circuits

Design of bandpass filters for microwave integrated circuits (MICS) utilizing dielectric resonators is discussed. Synthesis methods for both Tschebycheff and Butterworth responses are derived. Experimental results with S- and X-band filters are presented, and the agreement between theory and experiments is shown to be fairly good. Limitations on this technique due to poor temperature stability are also discussed.     

Analysis and Composition of a New Microwave Filter Configuration with Inhomogeneous Dielectric Medium

A theoretical study has been undertaken to solve inter-resonator coupling problems, and to design a new structure of microwave bandpass filter. This filter is composed of quarter-wavelength resonators arranged in a housing with the same ends short-circuited. This arrangement of resonators has never been utilized to compose bandpass filters because of the small inter-resonator coupling. The coupling coefficient of TEM resonant lines has been derived theoretically and expressed with capacitive parameters of the coupled lines. The accurate values of capacitances of the lines were obtained by the numerical analysis of the TEM field. By a simple method to make the medium inhomogeneous through removing the dielectric partially, a simplified structure of filter has first been realized based on the theory. Through numerical analysis by the finite difference method, this structure is also shown to have higher unloaded Q of resonator than conventional dielectric-filled coaxial filters to minimize the volume of filters.     

Temperature compensated,high permittivity dielectric resonators for millimeter wave systems

The properties of selected low loss, temperature compensated high permittivity microwave and millimetre wave dielectrics are summarised and experimental convenience suggests that planar hybrid microstrip is the preferred circuit technology for the initial studies of dielectric resonators at the millimetre wavelengths. Data are presented for temperature stabilised oscillators and some simple band pass filters are discussed.     

源与负载感性交叉耦合的小型介质滤波器

为了提高滤波器的阻带衰减,研究了源与负载感性交叉耦合的小型介质滤波器。首次提出一种新概念：将源和负载看作准谐振器。以贴片电感作为源与负载之间、源与第二个谐振器之间的交叉耦合元件,两个准谐振器和两个介质谐振器可构成级联四节(CQ),一个准谐振器和两个介质谐振器可构成级联三节(CT)。分析了传输零点的位置,详细讨论了这种滤波器结构的设计方法。采用介电常数为80的介质陶瓷组装了3个两级介质滤波器,并进行测试,结果表明传输零点的个数和位置与仿真设计相符合。滤波器的体积小,均为14 mm×6.5 mm×10 mm。     

低温共烧微波介质陶瓷材料研究进展

在介绍低温共烧陶瓷(LTCC)技术的基础上,阐述了LTCC微波介质陶瓷材料的特点及应用背景。综述了BaTi4O9、Ca[(Li1/3Nb2/3)1-xTix]O3-δ、ZnNb2O6、ZnTiO3及Li2O-Nb2O5-TiO2等常用的LTCC微波介质陶瓷材料体系。指出了目前研究中存在的问题,指出新体系的开发是今后的主要研究方向。新体系可以采用多相复合,也可以由几种低熔点氧化物化合而产生。     

Circular TE/sub 011/Mode, Trapped-Mode Band-Pass Filters

Band-pass filters are described which utilize a novel type of resonator which has been named a "'trapped-mode resonator." This type of resonator uses a structure which is open on its sides so that energy in all but a single desired mode tends to radiate out to energy-absorbing material. However, energy in the desired resonator mode is trapped within the structure and a high-Q resonance occurs, such as is typical of conventional microwave cavity resonators. The use of resonators of this type makes possible the design of band-pass microwave filters which have a pass band similar to that of other multiresonator microwave filters, but without the many unwanted pass bands which are typical of microwave filters. The particular type of filter discussed utilizes the circular TE/sub 011/ mode. Several experimental filter structures of this type were constructed, and the results of laboratory tests are described.     

微带型回音壁模介质谐振器带阻方向滤波器

本文报道了使用新型平面回音壁模介质谐振器的微带型毫米波带阻、方向滤波器。全文用行波环谐振器的方法进行分析,并给出了Ka波段带阻、方向滤波器的实验研究,其结果表明,该谐振器特别适用于毫米波微带集成电路。     

Bandstop Filter in Nonradiative Dielectric Waveguide Using Rectangular Resonators

A bandstop filter realized by means of rectangular resonators coupled to the center dielectric strip of a nonradiative dielectric (NRD) waveguide is described.This filter has the advantage that it is simple to manufacture, making use of a center dielectric of standard cross section. The design procedure is similar to the conventional strip line design procedure, with the stubs replaced by "stubs" of dielectric, or resonators. The design equations for the stub coupling are derived the properties of the stubs are obtained through measurement.     

Duplexer designed on the basis of microstrip filters using high dielectric constant substrates

A microstrip duplexer for a modification of a PCS communication system operating at frequencies of 1.84?C1.87 and 1.75?C1.78 GHz is described. The duplexer containing microstrip bandpass filters on high dielectric constant substrates (? _r = 92) are compared with duplexers manufactured on microwave ceramic materials with high values of ? _r . The microstrip bandpass filters use stepped-impedance resonators placed one near another with a gap of 0.1?C0.2 mm. It is shown that the microstrip duplexer has slightly lower insertion loss and occupies smaller volume than a duplexer using coaxial dielectric resonators having a rectangular cross section of 3 × 3 mm and ? _r = 92.     

Coplanar quarter-wavelength quasi-elliptic filters without bond-wire bridges

This paper presents the design and experimental results of two coplanar quarter-wavelength microwave filters operating at a frequency of approximately 3 GHz. Coplanar designs are of particular interest because they are less sensitive to the thickness of the dielectric substrate than other transmission-line types such as a microstrip. One of the designs has a quasi-elliptic frequency response. In addition, the design also eliminates problems with unbalancing of the ground planes normally present in coplanar structures. Bond wires between the ground planes are not required. This paper describes in detail the structure of the resonators and how they are coupled together to form a filter.