Enhanced waveguide bandpass filters using S‐shaped resonators

This article presents a new solution for stopband performance improvement of rectangular waveguide bandpass filters using S‐shaped resonator loaded waveguide configurations at microwave and millimeter‐wave frequencies. The proposed filter structure is compact in size when comparing with the standard E‐plane counterpart. Compactness is achieved by taking advantage of the properties of slow wave effect in half wavelength resonators. Periodicity is readily imposed upon cascading the S‐shaped resonators within the rectangular waveguide. The structure is simple and compatible with E‐plane technology. This type of bandpass filters can be easily realized with a single metallo‐dielectric insert within a standard rectangular waveguide. Simulation and experimental results are presented to validate the argument along with some design guidelines. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2009.     

Miniaturized rectangular waveguide filters

Two types of miniaturized rectangular waveguide filters are presented. Miniaturization is achieved using the slow‐wave effect of electromagnetic bandgap (EBG) surfaces and the left‐handed properties of split ring resonators (SRRs). The proposed EBG waveguide bandpass filter performs passband in the frequency range, which corresponds to the waveguide with the lower recommended operating band consequently enabling significant miniaturization of the structure. The SRR‐loaded bandstop filter makes use of the effect imposed by left‐handed medium (LHM), which is created by a combination of SRRs and wireline on the dielectric slab. Both filters are designed, simulated, and tested. Experimental results of the SRR‐loaded bandstop filter are presented to demonstrate feasibility of the proposed structures. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Dual‐band ridge waveguide filters for high‐selectivity wireless base station applications

Dual‐band filters simplify the system architecture considerably by replacing doubly multiplexed filters. This is especially important in base stations for wireless communications, where high‐selective filtering functions are required, with very stringent requirements in size and insertion losses. For this goal, compact dual‐band filters realized in air‐filled metallic ridge waveguides are proposed. The dual‐band approach shown in this article allows fulfilling the stringent insertion loss specifications of very selective filtering functions. The ridge waveguide resonators are placed in a canonical folded top‐bottom structure layout. Coupling sections that provide cross‐couplings are realized by irises opened in the intermediate wall. Given the high‐order of the dual‐band filter required for actual wireless applications, an efficient modeling by the mode‐matching method is used. A complete challenging filter prototype with 16 poles and 10 transmission zeros with specifications of typical wireless transceivers is built and tested for verification. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:703–712, 2016.     

CAD of evanescent‐mode bandpass filters based on the short ridged waveguide sections

The paper presents the internal details of a developed full‐wave algorithm for the computer‐aided design of evanescent‐mode bandpass filters formed by single‐ or double‐short ridged waveguide sections. New filter configurations with an enlarged cross section of filter housing and nonconventional notch‐strip‐notch elements providing improved stopband performance are given special considerations. Additional input–output transformers built on rectangular waveguide sections are used in designing broadband filters. Characteristics of one of the designed filters are verified by measured data. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 354–365, 2001     

Modeling of cavity-backed coaxial line to rectangular waveguide junction

A coaxial line to a rectangular waveguide junction, backed by an iris-coupled cavity, is analyzed using a new approach based on the five-cavity moment method. The scattering matrix of the junction is obtained by combining the mode-matching method and an interpolation technique. The computed results are checked for orthogonality and unitary conditions, and are verified against experimental results. The proposed structure and the analysis method will be useful in the design of extracted pole filters, diplexers, and multiplexers. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 20–26, 1998.     

Direct‐coupled waveguide filters for the lower gigahertz frequency range

An analysis method based on the coupled‐integral‐equations technique (CIET) and the mode‐matching technique (MMT) is presented for the design of a variety of direct‐coupled waveguide filters suitable for applications in the lower gigahertz frequency range. The method is verified by comparison with data obtained through other numerical techniques and measurements. With reference to standard waveguide filters, the issues of filter miniaturization and stopband extension toward higher frequency bands are investigated. For given frequency specifications in the 2‐GHz frequency range, examples of rectangular coaxial waveguide filters, ridge waveguide filters, ridge waveguide filters including coupling irises and T‐septum waveguide filters are presented. It is demonstrated that the rectangular/square coaxial waveguide filter achieves the highest degree of miniaturization, but that ridge and, especially, T‐septum waveguide filter technology is advantageous with respect to stopband performance toward higher frequencies. In particular, a T‐septum filter centered at 2.155 GHz is shown to block the entire frequency range up to 7.5 GHz. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 217–225, 2002.     

A compact feed horn with wide‐distributed operating bands of Ku/Ka/W

This paper presents a design of a compact tri‐band feed horn for reflector, which has sufficient wide‐distributed operating bands at 14.5, 35, and 94 GHz. A single cavity is used to downsize and simplify the whole structure, replacing multiple transition sections, or dielectric rods. To maintain a good isolation, two 3‐order low‐pass filters are applied in the waveguide ports of Ku/Ka‐band respectively, meanwhile retaining a good coupling and minimal destruction on transmission modes. The prototype of the proposed tri‐band feed horn is fabricated and measured, showing an adoptable candidate for multiband reflector antennas.     

Three‐dimensional split‐step‐fourier and finite difference time domain‐based rectangular waveguide filter simulators: Validation,verification, and calibration

The split‐step‐Fourier‐based three‐dimensional wave propagation prediction and finite‐difference time‐domain‐based simulators are developed to show network scattering parameters of rectangular waveguide filters with horizontal and/or vertical windows as capacitive and/or inductive irises, respectively. The three‐dimensional‐split‐step parabolic equation simulator is applied to rectangular waveguide filters, and the results are compared with finite‐difference time‐domain model through tests inside a rectangular waveguide. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:660–667, 2016.     

Mode‐matching analysis of H‐plane ferrite‐loaded rectangular waveguide discontinuities

The full set of eigenmodes existing in a ferrite‐slab‐loaded rectangular waveguide is first obtained and then used to compute the scattering matrix of a junction between an air‐filled rectangular waveguide and an H‐plane ferrite‐slab‐loaded rectangular waveguide by using the mode‐matching method. Numerical results for the scattering parameters of the H‐plane waveguide discontinuity are compared to experimental data and those obtained by Ansoft's HFSS. Good agreement is observed. To demonstrate the usefulness of this structure, a computer‐optimized 90° nonreciprocal phase shifter is designed using an H‐plane ferrite‐slab‐loaded waveguide. With only one‐step impedance matching sections at both ends of the ferrite slab, a compact design is achieved to have 2° phase error and less than ?30 dB return loss over about 5% bandwidth. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 259–268, 2003.     

Micromachined plastic W-band bandpass filters

Results are presented for micromachined plastic waveguide bandpass iris filters for W-band applications using a cost-effective polymer micro hot embossing process in conjunction with metallic electroplating and sealing techniques. The prototype filter has an 8-μm thick electroplated gold layer on a polymeric WR-10 waveguide with a 5-cavity Chebyschev-type design. Measurement results show center frequency of 96.77 GHz with a bandwidth of 3.15%, a loaded quality factor 31.73 and an unloaded quality factor for a single cavity resonator is 1210.6, respectively. A minimum insertion loss of −1.22 dB and return loss of better than −9.3 dB have been measured over the entire passband.     

Use of 3D field simulators in the synthesis of waveguide capacitive iris coupled lowpass filters

This paper presents the generalized lowpass filter design method of Levy based on three‐dimensional electromagnetic analysis and discontinuity modeling using commercially available full‐wave electromagnetic simulators. It shows how to use Levy's method for very accurate theoretical design of a waveguide capacitive iris lowpass filter, using modern 3D EM field‐solvers based on the finite element method (FEM), the mode matching method (MM), and the transmission line matrix (TLM) analysis method. This is the first time that design curves and equations, based on full electromagnetic modeling, have been presented for constant thickness capacitive iris filters. We will demonstrate our approach by designing a number of waveguide capacitive iris filters. This paper also demonstrates the generality of the method. This method can be applied to many other types of waveguide lowpass and bandpass filters. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 190–198, 2000.     

Electromagnetic design of folded‐waveguide resonator filter with single finite‐frequency transmission zero

This article presents electromagnetic (EM) design of a new folded‐waveguide resonator filter that uses an advanced coupling scheme to achieve the desired asymmetric frequency response with an attenuation pole of finite frequency on the high side of the passband. A filter of this type with a fraction bandwidth about 5% at a center frequency of 4.45 GHz has been successfully designed using a commercially available electromagnetic simulator. The designed filter has been fabricated and tested. Simulations and experimental results are presented to validate the design and to show the advantages of this type of filter. This filter also provides a compact size compared with conventional cavity resonator filters. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Computer‐aided design of 3D microwave filter using quasi‐planar high Qu dielectric resonator

A dielectric resonator filter is proposed for high‐speed data communication systems and for multilayer filter applications. The structure is composed of a partially metallized dielectric plate enclosed in a parallelepipedic cavity. This topology allows high integration in a planar‐type environment. The proper excitation is ensured by coplanar lines directly integrated on the dielectric resonator. This structure, easily manufactured, is suitable for high frequency‐filtering and power applications. In order to realize two‐ and four‐pole filters without tuning, some new coupling and frequency compensation techniques are presented. To compensate for a parasitic effect, a direct optimization method is combined applying a global electromagnetic (EM) analysis to describe the four‐pole filter. Some experiments are performed to verify the theoretical design. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 333–341, 2000.     

Computer aided design of H‐plane tapered corrugated waveguide bandpass filters

This paper presents the complete computed aided design approach for the design of H‐plane iris‐coupled bandpass filters with improved stopband performance. Iris‐coupled bandpass filters with mixed (increased and decreased) adjacent resonator widths are proposed for the first time for improvement in the stopband performance. The simulated filter performance shows improved stopband performance and reduced filter dimensions compared with conventional H‐plane uniform corrugated waveguide bandpass filters. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 14–21, 1999.     

Design of coplanar waveguide elliptic low pass filters

This article proposes three design topologies of coplanar waveguide elliptic low pass filters. The design procedure is simple and explained in detail for the first topology. Numerical results are provided using the commercially available simulation softwares IE3D and HFSS to show the validity of the design with very good agreement. The proposed filters yield less than 0.1 dB attenuation in the passband (0–2 GHz), with a controllable slope of the transition between passband and stopband. The width of the rejection band is increased by simple filter cascading resulting in a passband to stopband ratio of up to 1:6. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

A prototype for predistorted high-pass filters

This paper presents a new technique for predistorting high-pass prototype filter networks to compensate for the dissipative losses in reactive elements. The method is based upon circuit transformations of a conventional predistorted low-pass prototype network. The resultant networks require additional resistors in addition to the lossy resonators. A design example of a fourth degree Chebyshev bandstop filter is presented. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 156–160, 1998.     

Spurious‐response suppression of substrate integrated waveguide filters using multishape resonators and slotted plane structures

This article introduces effective techniques to improve the stopband frequency response of substrate integrated waveguide filters. First, a filter is constructed by using different cavity resonators which resonate at the same fundamental mode but at different high‐order modes. A cascade connection of circular and rectangular cavities is used to separate high‐order modes, because the second resonant mode of the circular cavities is more than rectangular ones. Second, inserting transverse radiating slots at the proper positions of cavities, their second longitudinal resonant modes are shifted down and effectively rejected. Third, four cells of slotted plane structure (SPS) are adopted to the top plane of the both input and output feed lines of the filter to reject the undesired passbands or improve steepness of the filter. Also, a combination of the radiation slots with SPS is used to reject the spurious responses accompanied by sharp steepness of the filter. Comparing between the measurement values and simulation results verifies the effectiveness of the proposed configurations and the hybrid technique. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

积分清零与积分梳状滤波器在抽取滤波中的应用研究

抽取滤波器的设计是全数字软件接收机中的关键技术,选择合适的抽取滤波器可以使得效率和资源达到最佳的平衡.积分清零和积分梳状滤波器是两种实现简单、滤波性能较好的数字抽取滤波器.这两种滤波器在中频数字接收机中都有重要的应用.从原理上分析和研究了这两种滤波器频域响应,总结了积分梳状滤波器的设计方法.提出了两种滤波器结合应用的方法,并建立模型验证在性能方面的提高.在实际应用中,说明了两者在本质上相同但在结构上的差异,因此在应用中加以区分.通过两种滤波器在相干解调电路和同步电路中的仿真,进一步说明两种滤波器的设计和实现准则.     

Application of polynomial design of multiplexers to the implementation of a manifold microstrip triplexer

This article presents a microstrip implementation of a manifold multiplexer. The design procedure is based on evaluation, through an efficient synthesis algorithm recently proposed, of the characteristic polynomials of the triplexer, including the channel filters. Both the manifold and channel filters parameters are also available at the end of the synthesis. This approach, based on polynomial modeling of the triplexer, has been experimentally validated for the first time through a practical implementation in planar technology. The fabricated prototype consists of three channel filters of third order centered at 1.84, 1.95, and 2.14 GHz, with bandwidth of 75, 60, and 60 MHz respectively. This work illustrates in detail the design and implementation of the practical triplexer, starting from the initial specifications and obtaining the final physical dimensions of the structure. Following the technique here shown, each filter is synthesized taking into account for the loading effects of the whole manifold; the filters dimensioning can be carried out with the filters separated from the multiplexer. In this way the optimization tasks are greatly simplified as compared with previous techniques for multiplexer design. The measured results of a manufactured prototype show return losses under 17 dB and minimum isolation between channels equal to 25 dB. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23:690–698, 2013.