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.     

COMPUTER-AIDED OPTIMIZATION DESIGN OF BANDPASS FILTER WITH DIELECTRIC RESONATORS

By way of employing a multimode method together with the multimode transmission matrixtechnique based on the theory of planar circuits, the paper presents computer-aided design and optimized de-sign of bandpass fllters with dielectric resonators, and their sample was tested. The experimental result ofthe sample shows a reasonable agreement with the designed one.     

Serially-connected series-stub resonators for narrowband coplanar-stripline bandpass filters

In this letter, a coplanar stripline (CPS) series resonator composed of serially-connected series-stubs is proposed. This kind of resonator provides two transmission zeros close to the resonant frequency. With the proposed structure, the reactance slope parameters of the resonators are significantly increased and adjustable by changing the length ratio of the two series stubs. This is useful for designing narrowband filters which is difficult to realize with conventional series CPS resonators. The structures of the resonators are optimized for a lower radiation loss and used to design a narrowband Chebyshev bandpass filter. The simulation and experimental results show that the proposed filter provides multiple transmission zeros and high selectivity.     

A design method of optical bandpass filters

A design method of optical bandpass filters which are composed of several resonators consisting of dielectric layers is discussed. The relation between the loaded Q of a resonator and the thickness of each layer is calculated by treating equivalently each layer as a segment of transmission line and represented on a chart. It becomes possible to design an arbitrary value of loaded Q by using the chart. Thus, an optical bandpass filter of required bandwidth and rejection characteristic can be designed by finding out the optimum thickness of each layer of the resonator which is the component of the filter     

A novel coupled method for dual-mode dielectric resonators andwaveguide filters

A novel method for coupling dual-mode waveguide or dielectric resonator cavities is described and analyzed. The method has advantages of providing a practical, flexible, economic means of replacing irises, of offering easy tunability of the coupling over a wide range of coupling values, and of reducing the length of the coupling structure. Calculation of the resonator's coupling parameters using the mode-matching method yields accurate results and is verified by measurements. Experimental four-pole dual-mode elliptic function filters using the coupling method for empty cavities and dielectric-resonator-loaded cavities were constructed and tested. The test results showed excellent agreement with theoretical analysis     

Using the branch-line directional coupler in the design of microwave bandpass filters

This paper addresses the application of the branch-line directional coupler to the design of microwave bandpass filters. The basic idea consists of using the branch-line coupler as a transversal filtering section by loading the coupled ports of the coupler with suitable transmission-line segments ending in an open circuit and taking the isolated port as the output node. Thus, under the signal interference philosophy involved in classic transversal filter schemes, bandpass transfer functions with perceptible stopbands and sharp cutoff slopes are derived. Furthermore, the main characteristics of the synthesized filtering response, such as the bandwidth or the position of the out-of-band power transmission zeros, can be easily controlled by means of the design parameters of the transversal section. Hence, a large variety of bandpass filtering profiles different from those offered by classical filter schemes can be realized. Finally, the experimental usefulness of the transversal filtering section based on the branch-line coupler is proven with the design and construction in microstrip technology of two microwave bandpass filter prototypes at 5 GHz.     

High-Q microwave acoustic resonators and filters

The authors present recent experimental and modeling results for high-Q microwave acoustic resonators and filters for use in oscillators and other frequency control applications. Overmoded resonators have exhibited an FQ product greater than 1×10¹⁴ Hz (e.g., Q=68,000 at 1.6 GHz) with a strong inductive response suitable for one-port and two-port oscillator feedback circuits. Ladder filters fabricated with overmoded resonators have loaded Qs greater than 40,000 with 76-kHz bandwidth at 1.6 GHz. Aluminum nitride films were used for transduction on Z-cut sapphire and lithium niobate substrates     

Passive CCD resonators [for high Q bandpass filters]

The passive CCD resonator is a recursive CCD building block which is well suited for the realization of high Q bandpass filters. Its realization is compatible with the standard double-poly NMOS technology. Advantages of the new approach are an extremely low sensitivity of the center frequency which is determined by an external clock frequency, a relative bandwidth which does not depend on the center frequency but is controlled by a capacitance ratio, and signal frequencies at least up to some hundred kHz. The analysis, design considerations, and performance results are presented. A loaded Q factor of 30, a maximum stopband attenuation of 26 dB, and a negligible insertion loss in the passband are typical for a single CCD resonator. The maximum overall center frequency deviation /spl Delta/f/f due to fabrication tolerances is proportional to the transfer inefficiency of the CCD and has the value of about 2/spl times/10/SUP -4/.     

Tunable, temperature-compensated dielectric resonators and filters

A thermal and electromagnetic model of a tunable hybrid-mode dielectric double resonator is introduced and analyzed by the mode-matching technique. Results of the analysis show the temperature sensitivity of the structure as a function of the center frequency as well as the other resonator parameters. A simple optimization procedure which allows the design of the resonator to have both a wide tunability range and good thermal stability of the resonant frequency is described. A circuit model is presented for a tunable four-pole dual-mode filter. The model exhibits interesting dual passbands, separated by a very-high-attenuation stopband. Measured results obtained from an experimental four-pole dual-mode dielectric resonator filter designed using the tunable hybrid-mode resonators showed excellent tunability range (200 MHz at C-band) and good agreement with the circuit model     

Best approximation for design of natural resonance frequencies of microwave dielectric disc resonators

Une méthode nouvelle pour le calcul des fréquences de résonance des résonateurs diélectriques cylindriques est présentée. La condition de court-circuit magnétique imparfait appliquée successivement à toutes les parois augmente considérablement la précision. Les valeurs théoriques et expérimentales diffèrent au plus de 1%. We present a new method for efficient computation of the resonance frequencies of dielectric disc resonators. Successive applications of imperfect open-circuit boundary conditions to all walls greatly improve the accuracy for resonance frequencies. Theoretical values agree within 1% of experimental results.     

基于E型双模谐振器的源负载耦合带通滤波器设计

为实现滤波器的小型化和高性能,提出了两款中心加载的E型双模谐振器,并对其进行了奇偶模分析。在此基础上通过引入源负载耦合,采用ADS与HFSS软件进行了仿真与优化。开路支节加载与短路支节加载的E型双模谐振器分别比方环谐振器减少42.8%与52.6%。实测结果表明,设计的滤波器中心频率分别为4.22 GHz和3.75 GHz,相对带宽分别为33.6%和9.1%,带内插损分别为-0.9 dB和-1.9 dB,带外零点位置与计算仿真结果吻合良好。这两款滤波器不仅尺寸小、插损低,并且具有宽阻带、传输零点可调的优点,短路支节加载的双模滤波器在选择性与带外抑制方面性能更好,可以广泛应用于各种微波电路中。     

Low-pass and high-pass filters using coaxial-type dielectric resonators

This paper proposes new low-pass and high-pass filters using coaxial-type dielectric resonators. The low-pass filter has a LC-type circuit structure and is composed of three inductances and two resonance circuits. The resonance circuits are the open-ended coaxial-type dielectric resonators whose length is λg/4. The high-pass filter has a CL-type circuit structure. Two high-pass filters are described, one of them is composed of three capacitances andtwo resonance circuits, the other is composed of five capacitances and four resonance circuits. The operating frequency range of the low-pass filter is 0.13–0.9 GHz and the cutoffency is 900 MHz, and the insertion loss is 0.3 dB. The corresponding quantities of the high-pass filter are 0.9–2.5 GHz, 900 MHz, and 0.3 dB, respectively.     

Stub-tuned microstrip bandpass filters for millimeter-wave diplexer design

This letter presents a new design for microstrip bandpass filters and its application to a millimeter-wave diplexer. Basically, parallel-coupled microstrip lines are utilized for bandpass response and non-uniform open-circuited stubs are added to tune the bandwidth of the passband and improve out-of-band rejection. The designed filters are connected to make a diplexer, which can be used in a phased-array transceiver system operating in millimeter-wave range. The diplexer is designed to separate an input signal containing both 32GHz and 35GHz into two signals of 32GHz and 35GHz, respectively or to combine two signals at 32GHz and 35GHz into one signal.     

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.     

Exact design of switched-capacitor bandpass ladder filters

An exact design of switched-capacitor bandpass filters is presented. This new technique is based on the distributed circuit theory with a suitable bandpass transformation. The theoretical aspects of this method are given as well as the simulated results using a switched-capacitor circuit-analysis program.     

Graphical design of millimeter-wave finline bandpass filters

A very simple yet accurate design procedure for the finline bandpass filters at millimeter wavelengths is presented. The technique enables the geometry of finline bandpass filters to be obtained accurately from simple closed-form equations and curves. Using this graphical approach, various millimeter-wave finline bandpass filters have been designed. Results in V-band (50 to 75 GHz) and W-band (75 to 110 GHz) are presented and indicate a good agreement between the calculated and measured performances.     

High-performance microwave coplanar bandpass and bandstop filters on Si substrates

High-performance bandpass and bandstop microwave coplanar filters, which operate from 22 to 91 GHz, have been fabricated on Si substrates. This was achieved using an optimized proton implantation process that converts the standard low-resistivity (/spl sim/10 /spl Omega//spl middot/cm) Si to a semi-insulating state. The bandpass filters consist of coupled lines to form a series resonator, while the bandstop filter was designed in a double-folded short-end stub structure. For the bandpass filters at 40 and 91 GHz, low insertion loss was measured, close to electromagnetic simulation values. We also fabricated excellent bandstop filters with very low transmission loss of /spl sim/1 dB and deep band rejection at both 22 and 50 GHz. The good filter performance was confirmed by the higher substrate impedance to ground, which was extracted from the well-matched S-parameter equivalent-circuit data.     

Tentative approach to the design of waveguide-below-cutoff bandpass filters

This letter deals with a theoretical approach to the waveguide-below-cutoff bandpass filter. An equivalent circuit of the elementary section of the filter is used to derive the attenuation and bandpass properties. In order to explain some discrepancies between theoretical and experimental data, a more sophisticated circuit is introduced.     

级联MZI带通巴特沃斯微波光子滤波器的设计

随着对MPF(微波光子滤波器)的深入研究,设计的方法和滤波器性能都得到了很大改进,但是对于给定参数实现一些典型结构的MPF的报道却很少。在深入研究数字滤波器和MPF结构的基础上,采用数字滤波器的设计方法,给出了带通巴特沃斯MPF的详细设计过程。利用数字滤波器的设计方法得到了所需带通巴特沃斯MPF传递函数的零点和极点。采用光纤环辅助的MZI(马赫-曾德干涉仪)级联,实现滤波器的传递函数,根据传递函数的零点和极点计算确定了各级联MZI的结构参数:耦合系数、臂长差和环长,并对其进行了仿真验证,结果与带通巴特沃斯MPF设计要求基本一致,并进一步研究了不同结构参数对MPF的影响。     

宽阻带波导带通滤波器的精确设计

应用模式匹配法分析了矩形波导中双面阶梯的不连续性.在此基础上,设计和优化了一个C波段1/4波长传输线耦合谐振膜片型带通滤波器.与传统的直接耦合半波长谐振腔型带通滤波器相比,这种滤波器带外抑制度高,阻带宽,特别是其尺寸缩短了近40%.该滤波器的实测结果与数值计算结果吻合很好.