Tuning Screws Research Articles

Design of manifold-coupled multiplexers

Following a brief review of different types of multiplexer configurations, a systematic design approach has been outlined for the design of manifold-coupled multiplexers. The piecewise approach, optimizing parts of the multiplexer separately in repeated cycles while converging upon an optimal solution, has proved to be very effective for most practical applications. The technique is readily applicable to manifold multiplexers incorporating an arbitrary number of channels, regardless of their bandwidths and channel separations. There are no restrictions on the design and implementation of channel filters onto the manifold; they may be asymmetric, and may incorporate transmission zeros, group delay equalization zeros, or both. The manifold itself is a transmission line, be it a coaxial line or a rectangular waveguide or some other low-loss structure. The costly EM simulation is used economically on manifold junctions and channel filters through the use of space-mapping optimization techniques, where EM-based simulators are used to fine-model each multiplexer channel and coupling matrix representation is used to coarse-model the performance. Fine details such as tuning screws may be included in the design process. This design procedure takes into account the effects of dispersion and spurious modes and, as a result, the overall design and final tuning time can be significantly reduced.

Passive microwave filter tuning using bond wires

A practical method is proposed to tune microwave planar filters. When the circuit is fabricated, a number of additional capacitive patches and inductive lines are patterned close to the filter. These patches and lines can be connected to the filter by bond wires to tune the filter response. By replacing the traditionally used tuning screws with these bond wires, the package for a microwave filter can be much more compact, and the mechanical reliability of the tuned filters can be improved. To demonstrate the method, a three-pole microstrip filter is fabricated on a Duroid substrate. The additional capacitive patches and inductive lines are also patterned on the same substrate close to the filter. By connecting the patches and the lines to the filter with bond wires, the centre frequency of the three-pole filter is easily tuned by −7% and+7%, respectively, and can be tuned to an arbitrary value in a wider range. The return loss of the filter is tuned from 15 dB to better than 20 dB in the passband at the same time. It is also found that the bond wire has introduced negligible additional loss.

A dual-mode waveguide pseudo-elliptic filter with zero-shifting properties

This paper describes the design and realization of dual-mode waveguide filters with zero-shifting properties. The transmission zero can be shifted from one side of the passband to the other by simply changing the resonant frequencies of the resonators. Without changing the physical dimensions of the resonators and coupling irises, transmission zeros can be shifted by adjusting the tuning and coupling screws. The filters are realized and the measured results show good agreement with the simulated ones. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 357–359, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21169

The Electric-Field Integral-Equation Method for the Analysis and Design of a Class of Rectangular Cavity Filters Loaded by Dielectric and Metallic Cylindrical Pucks

Rectangular cavity filters loaded by metallic and dielectric cylindrical pucks represent a wide class of structures used for the realization of compact microwave filters for space and terrestrial communications. The electric-field integral-equation method has been applied here to develop a software tool for the design of such a class of filters. Resonators simultaneously containing a number of dielectric and metallic cylindrical pucks can be analyzed using the method presented here. Dielectric loaded rectangular waveguide filters and comb-line filters are two typical examples where this approach can be applied. The input and inter-cavity couplings realized by slots have been modeled using the proposed integral-equation method. The full-wave analysis and optimization of an entire filter can be performed using the software presented here. Dielectric and metallic losses have been taken into account and the tuning screws have been also included into the analysis. The prototype of a single resonator and complete passband dielectric loaded rectangular waveguide filter have been realized and measured to test the software, and a commercial software has also been used to validate the code. A number of examples are presented here. A very short computation time of the order of 1-s/frequency point for the analysis of an entire filter has been obtained, making the full-wave optimization of an entire filter an affordable task.

A Shorted Waveguide-Stub Coupling Mechanism for Narrow-Band Multimode Coupled Resonator Filters

A shorted waveguide-stub coupling mechanism is presented for implementing narrow-band multimode coupled cavity filters without coupling screws. The coupling element is a shorted rectangular waveguide stub placed in the end walls of cylindrical filter cavities, using perturbation of the magnetic fields to obtain coupling between degenerate modes. This structure is well suited to analysis and design with the efficient and accurate mode-matching method. Coupling coefficients and resonator frequencies can be controlled by varying cavity dimensions and the length, width, and depth of the rectangular coupling element. The accuracy with which the coupling can be realized and the elimination of coupling screws reduce the amount of tuning substantially. A third-order Chebyshev filter, realized in a triple-mode cavity with no coupling screws and only two tuning screws, is presented to verify the use of the coupling structure.

EM-Based Design of Large-Scale Dielectric-Resonator Filters and Multiplexers by Space Mapping

A novel design methodology for filter and multiplexer design is presented. For the first time, finite-element electromagnetic (EM)-based simulators and space-mapping optimization are combined to produce an accurate design for manifold-coupled output multiplexers with dielectric resonator (DR) loaded raters. Finite-element EM-based simulators are used as a fine model of each multiplexer channel, and a coupling matrix representation is used as a coarse model. Fine details such as tuning screws are included in the fine model. The DR filter and multiplexer design parameters are kept bounded during optimization. The sparsity of the mapping between the design parameters and the coupling elements has been exploited. Our approach has been used to design large-scale output multiplexers and it has significantly reduced the overall tuning time compared to traditional techniques. The technique is illustrated through design of a five-pole DR filter and a ten-channel output multiplexer.

Two-zero four-pole building block for microwave waveguide filters using all-resonant modes at their cutoff frequency

This article describes a basic building block for microwave waveguide filters. It uses a new coupling scheme where all resonant modes are used at their cutoff frequency. It is composed of a cascade of basic nonloaded rectangular cavities where the modes are alternately single mode and dual mode. These cavities are coupled directly, without any iris. Neither coupling nor tuning screws are needed. The analysis of the discontinuities is performed by the method of moments (MoM). The synthesis makes use of an optimization method based on the genetic algorithm. Prototypes have been realized and measurements are shown to confirm the analysis results. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 429–437, 2003.

A 9 pole bandpass filter at 2.7 GHz with Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-δ/ coplanar wave guides on a sapphire substrate

A bandpass filter for a 0.6 dB relative bandwidth of 4.5% at 2.67 GHz is implemented with nine end coupled resonators of meander lines with air bridges for ground connections on a 1.7/spl times/3.7 cm/sup 2/ substrate. A single side thermally co-evaporated Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film with a CeO/sub 2/ buffer layer on a sapphire substrate is patterned with an Ar ion beam. Within a bandwidth of 112 MHz at 2.67 GHz the measured insertion loss is smaller than 0.1 dB at 15 K. Filters for a two channel receiver with almost identical transfer functions have been achieved without manual tuning screws. Their characteristics should not be affected by mechanical vibrations on a cold finger.

Coplanar microwave filters with YBa 2Cu 3O 7− δ thin films on sapphire substrates

A bandpass filter for a 1 dB relative bandwidth of 2.5% at 1.417 GHz is implemented with five end coupled resonators of meander coplanar lines with air bridges for ground connections on a 4.0×2.6 cm 2 substrate. A single sided sputtered YBa 2Cu 3O 7− δ film with a CeO 2 buffer layer on a sapphire substrate is patterned with an Ar ion beam. The wanted bandwidth of 35 MHz near 1.4 GHz is measured with a minimum insertion loss smaller than 0.1 dB at 15 K. Filters for a two channel receiver with almost identical characteristics have been fabricated without manual tuning screws. In the passband an insertion loss difference of less than 0.2 dB has been achieved. Their characteristics are not affected by mechanical vibrations on a cold finger. To attenuate higher order pass bands the design of a superconducting low pass filter is discussed.

Effects of walls on coupling between coupled combline resonators

The effects of the open-side end-wall and ground walls (planes) on the coupling between two identical combline resonators coupled through slots are analysed. It is shown that the electric coupling, which is necessary to realise filters with transmission zeros, can be achieved only when the ground planes are sufficiently close to the resonator post while the open-side end-wall is sufficiently far from it. A criterion for choosing the wall distances from the post is presented. Also, it is shown that the tuning screw (which is mounted on the end-wall) significantly reduces the electric coupling only when it is very close to the post.

Improvements of an inverted trapezoidal pulse antenna

Summary form only given, as follows. A simple tuning screw can improve the wideband impedance matching of an S/C-band trapezoidal impulse antenna-operating over a 4 GHz frequency range-by lowering the SWR level below 1.5, which is 50% better than competitive designs. Thus, operation at high output power levels, typical in radar applications, becomes feasible. Besides this, it is possible to reduce the weight of the construction to 60% of the original, without affecting the input impedance, by using a hatch-like material for the radiating element and the reflector. Finally, we show that a conventional swept-frequency analysis may have fewer uncertainties for pulse-antenna measurements. An example of a practical conversion from the frequency domain to the pulse response is demonstrated.

Automated computer-controlled tuning of waveguide filters using adaptive network models

This paper describes a method for computer-controlled tuning of waveguide filters. The tuning algorithm is based on approximate filter network models, which take into account the effects of input/output coupling. Based on measurements of an initial filter design, the approximate network model is then corrected by optimizing the element values such that they minimize the mean square error between the measured and simulated response. The sensitivities of the tuning screws are determined directly from the sensitivities of the element values. Filter tuning is accomplished by gradient optimization of the corrected computer model rather than its physical realization. Only as a final step are the tuning screws of the physical model turned to the position determined by the optimization process.

Superconducting filter for IMT-2000 band

In this paper, a new design of microstrip-line superconducting filters for IMT-2000 band application is presented. The design features high selectivity by means of creating transmission zeros and using many resonators. As a demonstration, 16- and 32-pole filters were fabricated using YBCO films on a half-area and on the full area of 3-in-diameter MgO wafers, respectively. Excellent attenuation of more than 30 dB, 420 kHz from the lower band edge, and 400 kHz from the upper band edge for the 32-pole filter was achieved. The filters were tuned not with mechanical tuning screws, but with a dielectric film. The tuning was carried out based on a novel method of measurement. These techniques are also described.

Computer‐aided design of inductively coupled rectangular waveguide filters including tuning elements

In this paper we first describe a CAD tool for rectangular waveguide filters with tuning elements based on a multimode network representation. The equivalence between tuning elements of circular and square cross section is then investigated. Next we discuss the CAD of a tunable filter to be used over a given frequency range. Finally, measured performances are presented for two types of implementation. The first is a filter structure in which the required frequency of operation is easily changed by replacing its top cover, without affecting the filter bandwidth. The second is a traditional implementation using manually adjusted tuning screws. Measured and simulated results are shown to be in good agreement, thereby fully confirming the validity of the CAD tool described. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 226–235, 1998.

Computer-aided design of inductively coupled rectangular waveguide filters including tuning elements

In this paper we first describe a CAD tool for rectangular waveguide filters with tuning elements based on a multimode network representation. The equivalence between tuning elements of circular and square cross section is then investigated. Next we discuss the CAD of a tunable filter to be used over a given frequency range. Finally, measured performances are presented for two types of implementation. The first is a filter structure in which the required frequency of operation is easily changed by replacing its top cover, without affecting the filter bandwidth. The second is a traditional implementation using manually adjusted tuning screws. Measured and simulated results are shown to be in good agreement, thereby fully confirming the validity of the CAD tool described. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 226–235, 1998.

CAD applying the finite-element method for dielectric-resonator filters

The progress of numerical techniques now permit us to analyze rigorously complex devices such as dual-mode cavity multipole filters or planar passive elements for coplanar monolithic microwave integrated circuits (MMICs). In this paper, we describe a rigorous design of dielectric resonator (DR) filters applying the finite-element method (FEM). We first present a dual mode coupling technique which replaces classical DRs, coupling, and tuning screws, which are commonly used in dual-mode filters, by slotted DRs. Next, a new theoretical analysis based on the contribution to the dual-mode filter response of the first DR hybrid mode and of higher order modes is described. This analysis can be applied to any type of microwave dual-mode filter. It allows us to define a procedure which explains the presence and controls the position of the two transmission zeros in the filter responses. In this paper, this procedure has been applied to improve filtering performances of a dual-mode DR filter. Finally, a synthesis method is developed to rigorously design for the first time, a four- and an eight-pole slotted DR elliptic filters. The experimental results were obtained with no tuning and the theoretical ones show good agreement.

Automated design of waveguide components using hybrid mode-matching/numerical EM building-blocks in optimization-oriented CAD frameworks-state of the art and recent advances

Fast hybrid mode-matching/boundary-contour (MM/BC) and mode-matching/finite-element (MM/FE) waveguide building blocks are described for the optimization-oriented use in powerful circuit computer-aided design (CAD) tools and the automated design of waveguide components. The efficient electromagnetic (EM) CAD technique allows the accurate design of a comprehensive class of rectangular and circular waveguide components including realistic structures of higher complexity. The efficiency and flexibility of the hybrid CAD method is demonstrated at advanced EM design examples, such as broad-band circular-to-rectangular waveguide transitions including octagonal cross sections, waveguide resonator filters with rounded corners, optimum-shaped bends, dual-mode filters with coupling sections without tuning screws, ridged waveguide filters with rounded corners, and multiplexers. The designed components are directly amenable to cost-efficient fabrication techniques like computer-controlled milling methods. The theory is verified by available measurements.

Precise computations of resonant frequencies and quality factors for dielectric resonators in MICs with tuning elements

In this paper, the highly accurate results of resonant frequencies, field distributions, and quality factors of the TE/sub 01/spl delta// mode for the cylindrical shielded dielectric resonator (DR) in microwave integrated circuits (MIC's) with a practical tuning element, such as the metallic tuning screw and the dielectric tuning device, are presented. By using the newly developed FD-SIC method, numerical results can be calculated accurately and efficiently. The DR structures with tuning elements can be more easily modeled by the present approach than the other methods using approximate solutions or the mode-matching (MM) methods. Numerical results in the literature are compared to the present FD-SIC results for the DR without tuning elements and detailed discussions on these results are given. In addition, design curves are also presented for the DR with the metallic tuning screw and with the dielectric tuning device. These design curves are helpful for designing DR systems with tuning elements in MIC applications.

Full-wave design and realization of multicoupled dual-mode circular waveguide filters

A new full-wave method for the design and realization of dual-mode circular waveguide filters is presented. The rigorous CAD is a combination of the mode-matching and the finite-element techniques, which permits obtaining the Generalized Scattering Matrix for all the blocks that compose the structure (rectangular slots, cross-irises, and screws). The finite thickness of the irises, the higher order mode interaction, as well as the coupling and tuning screws are rigorously taken into account. A systematic design process for the different elements is described. A full prediction of resonant out-of-band spurious modes is accomplished prior to the filter construction. Special attention is devoted to the circuital model in order to save a great deal of computational effort in the final adjustment. A four-pole elliptic circular waveguide cavity filter has been designed and constructed. The experimental filter results show excellent agreement with theory. >

Full-wave design of spurious free DR TE mode band pass filters

Analytic full-wave analysis and design of direct-coupled dielectric loaded bandpass filters in rectangular waveguide configuration using the TE/sub 10/ mode with a spurious-free response up to twice the operating frequency is described. The filter has no tuning screws and is small in size. Theoretical design of the filter is supported by the experimental results. Superiority of the filter over the inductive window-coupled filter is presented. Practical issues faced while building the filter are discussed. An alternative folded configuration of the filter that allows the implementation of both the canonical elliptic function as well as the Chebychev response is also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>