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.     

E and H‐plane wide‐band ridge waveguide couplers

A systematic synthesis procedure for ridge waveguide branch line couplers in both E‐plane and H‐plane configurations is presented. Ridge waveguides are chosen to benefit from their wide mono‐mode band and compact size compared to rectangular waveguides. Equivalent circuit parameters are used to synthesize the coupler sections. Rigorous mode matching method is used for full‐wave analysis and optimization of the couplers. Ridge couplers both in empty waveguide and Low Temperature Co‐fired Ceramic “LTCC” technology are designed using the proposed method and the design is verified with another numerical method. A prototype is built and its response is measured to verify the approach. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Design of dual‐mode dual‐band rectangular waveguide filtering antenna

A dual‐mode dual‐band rectangular waveguide filtering antenna with fourth‐order Chebyshev response is presented. First, design equations and processes of filtering networks are presented. Then, filtering antenna is constructed through cross‐shaped slot for radiation instead of the output port of filtering networks. A pair of degenerated modes are exploited in waveguide resonator design to miniaturize the whole size and form two passbands. In addition, the bandwidth can be adjusted flexibly in proper range. A prototype at C‐band is fabricated and measured, showing two operation channels of 5 to 5.05 GHz and 5.1 to 5.15 GHz with high rejection between two bands. Good agreement is achieved between the simulations and measurements, showing excellent performance in terms of filtering, out‐of‐band rejection, and gain in bands.     

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.     

A folded dual‐mode bandpass filter with circular waveguide

In this article, a folded circular waveguide dual‐mode filter without tuning screws is designed for the fifth‐generation (5G) mobile communication system. The folded filter is composed of two stacked circular cavities operated at 3.5 GHz. Each cavity has two resonant modes, which can generate and control two transmission zeroes at specific frequencies. Through a coupling iris, the two single‐cavity filters are connected together, and can control four poles, which helps to expand the 3dB fractional bandwidth to 11.4%. The measured insertion losses are around 0.5 dB in the passband (from 3.4–3.6 GHz). The experiment results show an excellent agreement with the simulation results. Such folded filters have the advantages of very low insertion loss, compact size, high frequency selectivity, and low cost.     

Full‐wave modeling and optimization of Bøifot junction ortho‐mode transducers

The full‐wave design of broadband ortho‐mode transducers based on the Bøifot junction has two main aspects: an efficient analysis method and a design process divided into tasks with relatively low computational effort. In the analysis part, a rigorous mode‐matching technique has been developed to obtain the generalized admittance matrix of the Bøifot junction. The other elements of the device are also analyzed by mode‐matching. With respect to the design, the proposed procedure starts with the optimization of the individual building blocks of the device. Their interaction is also taken into account in a systematic process. The analysis and design methods have been validated with other numerical methods and an experimental prototype. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

A compact substrate integrated waveguide H‐plane horn antenna with dielectric arc lens

An H‐plane horn antenna constructed into SIW (substrate integrated waveguide) is proposed. It has a dielectric arc lens for better directivity and a simple microstrip transition as feed. The horn, the lens and the transition share the same substrate. The resulting formula from optical principles shows that the suitable dielectric lens can improve the directivity of the antenna significantly. A prototype was fabricated; the antenna size is 39.175 × 14 × 2 mm³. The frequency band is from 25.5 to 28.5 GHz. The measured gain of this antenna is about 9 dB; the bandwidth, at 10 dB return loss, is over 12%. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Study of the design of waveguide filters with improved suppression of modal interference through the cross‐shaped slot

In this article, a new method is suggested to improve the frequency responses of dual‐mode waveguide filters employing cross‐shaped slots. According to this method, regarding one cross‐shaped slot between two cavities, the horizontal (vertical) mode in one cavity influences the vertical (horizontal) mode in the other cavity to a much lesser extent. It enhances the overall performances. A 4^th‐order dual‐mode filter is used as an example and it validates the method. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 285–292, 2003.     

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.     

A systematic approach for computer aided design of waveguide E‐plane diplexers

This paper presents a systematic approach for computer aided design of waveguide E‐plane diplexers. The approach is based on the principle of equireflection three‐ports and using the common junction as the constituent elements of the K‐inverters of each channel filter. The method divides an E‐plane diplexer in a number of key essential building blocks and adopts the best method for the analysis and synthesis of each key block. This has led to a very accurate and efficient design procedure with minimum computation effort. The advantage of the proposed design procedure has been demonstrated by the implementation of several E‐plane bifurcated and T‐junction millimeter‐wave diplexers. The design algorithms presented in this work can be implemented on a low end Pentium machine. An exact design of a diplexer requires no more than 10 min. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 104–116, 1999     

Design of a compact dual‐band folded‐waveguide bandpass filter using multilayer waveguide resonators

A novel compact dual‐band bandpass filter based on multilayer folded‐waveguide (FWG) structure is presented in this article.In this design, slots are used to realize direct coupling between adjacent resonators and apertures are adopted to implement cross coupling between non‐adjacent resonators.A new technique of external quality factor of FWG resonator and coupling coefficients between different resonators are studied using full‐wave simulator. In order to demonstrate the proposed technique, a four‐pole dual‐band bandpass filter is designed, fabricated and measured using vector network analyzer. Measurement results which are well agreed with simulation results are presented. Moreover, four‐pole substrate integrated folded waveguide SIFW dual‐band bandpass filter, using two layers of slotted folded waveguide resonators, is demonstrated. The proposed filter has a compact size and it is excellent candidate for the application of wireless communication systems. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:780–788, 2015.     

A covering Ka‐band two‐way switch filter module using a three‐line and an E‐plane waveguide band‐pass filters

A millimeter‐wave ultrawideband two‐way switch filter module is presented in this article. The switch filter module covers whole Ka‐band (26–40 GHz), and is composed of two wideband band‐pass filters and two monolithic microwave integrated circuit (MMIC) single pole two throw (SP2T) switches. One filter is realized using E‐plane iris waveguide band‐pass filter, and another is realized by a novel 11‐pole three‐line microstrip structure band‐pass filter. Compared with the traditional three‐line filter, the proposed three‐line filter not only retains virtues of the traditional three‐line filter, but also resolves drawbacks of it, which include discontinuities between adjacent sections, many parameters of design, and no effective matching circuits at input/output ports. The developed switch filter module is fabricated using hybrid integrated technology, which has a size of 51 × 26 × 9.8 mm³, and interconnections between MMICs and microstrip are established by bond wires. The fabricated switch filter module exhibits excellent performances: for two different states, the measured insertion loss and return loss are all better than 7 and 10 dB in each pass‐band, respectively. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:305–310, 2015.     

Compact Dual‐/Tri‐/Quad‐Band banpass filters using shorted stub loaded stepped‐impedance resonator

In this article, the shorted stub loaded stepped‐impedance resonator (SSLSIR) with the individually tunable first even resonant mode and first odd resonant mode is applied to design dual‐, tri‐, and quad‐band bandpass filters (BPFs). The SSLSIR dual‐band BPF with asymmetrical coupling is realized using the first even resonant modes and the first odd resonant modes of a set of SSLSIRs. Then, the high‐impedance feeding lines of SSLSIR dual‐band BPF is modified to produce a new passband, and thus a new tri‐band BPF is realized. The proposed quad‐band BPF consists of two sets of SSLSIRs with symmetrical coupling. Each of the designed circuits occupies a very compact size and has a good in‐band out‐of‐band performance. Good agreements are observed between the simulated and measured results. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:601–609, 2015.     

Substrate‐integrated waveguide band pass filters with frequency‐dependent coupling elements

An effective technique to improve the stop‐band frequency response of direct‐coupled resonators in substrate‐integrated waveguide (SIW) technology is introduced. Regular inductive‐iris filters in SIW technology are supplemented with H‐plane frequency‐dependent inverters which not only create transmission zeros but also serve as the proper impedance inverter. A synthesis technique is introduced to prescribe transmission zeros at finite frequencies on either side of the pass band, symmetrically or asymmetrically. Two different topologies of frequency‐dependent inverters for X‐band SIW band pass filters demonstrate that attenuation poles can be created on both side of the passband and significantly improve the filters' stop‐band performences. Measurements confirm the validity of the presented design approach. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:237–242, 2014.     

Independently controllable dual‐band microstrip bandpass filter using quadruple‐mode stub‐loaded resonator

In this article, a quadruple‐mode stub‐loaded resonator (QM‐SLR) is introduced and its four modes are excited using a simple approach, which can provide a dual‐band behavior. By changing the length of the loaded stubs, independently tunable transmission characteristics of the proposed quadruple‐mode stub‐loaded resonator were extensively described for filter design. Moreover, microwave varactors were adopted to represent the length variation of the loaded stubs for the dual‐band tunability. The equivalent circuit modeling of the open stub with microwave varactor was given and discussed. Then, adopting the compact quadruple‐mode stub‐loaded resonator with three varactors, an independently controllable dual‐band bandpass filter (BPF) was designed, analyzed, and fabricated. Its separated bandwidths and transmission zeros can be tuned independently by changing the applying voltage of the microwave varactors. A good agreement between simulated and measured results verified the design methodology. The proposed filter possesses compact size, simple structure, and excellent dual‐band performances. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:602–608, 2016.     

A novel super compact half‐mode substrate‐integrated waveguide filter using modified complementary split‐ring resonator

A novel super compact filter based on half‐mode substrate‐integrated waveguide (HMSIW) technology loaded by the modified complementary split‐ring resonator (MCSRR) is proposed. The working principle of the proposed filter is based on the evanescent‐mode propagation technique. According to this technique, by loading the complementary split‐ring resonator (CSRR) on the metal surface of the substrate‐integrated waveguide (SIW) structure, an additional passband below the SIW cutoff frequency can be obtained. In order to miniaturize the physical size of the conventional CSRR, a new method is introduced. In the proposed MCSRR unit‐cell, the meander slots are carved inside all of the interior space of the ring. Accordingly, the length of the slot is increased which leads to an increase in the inductor and capacitor of the proposed structure without occupying the extra space. Therefore, the electrical size of the proposed MCSRR unit‐cell is reduced. Consequently, the resonance frequency of the proposed MCSRR unit‐cell is decreased compared to the conventional CSRR with the same sizes. Namely, the lower resonance frequencies can be achieved by using this technique without increasing the size of the unit‐cell. In order to confirm the miniaturization technique, two HMSIW filters loaded by the proposed MCSRR unit‐cell are designed, fabricated, and experimental verifications are provided. The results show that a miniaturization about 67% is achieved.     

Independently controllable dual‐band filter using single quad‐mode silver‐loaded dielectric resonator

This article proposes a novel bandpass filter with two controllable passbands using a single quad‐mode silver‐loaded dielectric resonator (DR). The silver plane is inserted in the middle of the cubic DR and two degenerate pairs are used to build the two passbands. Because of the distinct E‐field distributions, the silver plane has significant effect on the degenerate pair (TE^x₁₁₂ and TE^y₁₁₂), whereas another one (TE^x₁₁₁ and TE^y₁₁₁) remains unchanged. With the aid of the silver plane, both center frequencies and bandwidths of the two bands can be controlled independently. To verify the proposed idea, a prototype dual‐band BPF is designed and fabricated. Good agreement between simulated and measured results can be observed.     

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 novel E‐plane substrate inserted bandpass filter with high selectivity and compact size

In this article, a novel E‐plane substrate inserted waveguide bandpass filter with high selectivity and compact size is proposed in Ka‐band. By integrating an extra resonator between two metal septa, the E‐plane waveguide filter is achieved with two transmission zeros at both sides of the passband which contribute to the high‐skirt selectivity. One sample is fabricated, whose total length is just 5 mm, namely, less than 0.5 and the minimum insertion loss is only about 0.3 dB. Good agreements between simulated and measured results are obtained. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:451–456, 2014.