Dual-Mode Dielectric Waveguide Monoblock Filter Design

This study presents a novel dual-ridged dual-mode dielectric waveguide resonator (DWR) for dual-band bandpass filter (BPF) designs. It employs the fundamental mode quasi-TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> and the second resonant mode quasi-TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">120</sub>. Two parallel ridges are placed on the top and bottom surfaces of the DWR at the maximum electric-field areas of the quasi-TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">120</sub> mode to control and reduce its resonant frequency. A metallized nonthrough hole at the DWR’s center controls and decreases the quasi-TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> mode’s resonant frequency. Therefore, a very compact volume is achieved for the dual-mode DWR. For verification, a fourth-order dual-band BPF is designed, fabricated, and measured by using the proposed resonator. The measured results highlight its key benefits: miniaturized volume, lightweight, low insertion loss, and flexible control over the center frequencies and bandwidths of both passbands.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This letter presents a novel compact lowpass filter with two transmission zeros. By tap-connecting the stepped-impedance hairpin unit, two transmission zeros can be generated when an interdigital structure is introduced between the two low-impedance sections. Further, the two transmission zeros can be adjusted easily to obtain a larger zero separation without the need to change the stepped-impedance unit. Therefore, a sharp transition, an expanded stopband, a low insertion loss, and a compact size can be obtained simultaneously. Two filters with single and two asymmetric units are designed, fabricated, and tested. The measured results demonstrate good performance: compact size, low passband insertion loss, broad stopband, and sharp skirt characteristic. </para>

Novel configurations for dual-mode dielectric resonators operating in the HEH/sub 11/ mode or the HEE/sub 11/ mode are presented. The use of the proposed configurations in the design of dual-mode dielectric resonator filters leads to a design with a remarkably improved spurious performance. Techniques to control the frequency separation between the resonance frequencies of the two dual-modes HEH/sub 11/ and HEE/sub 11/ are discussed. Experimental results are presented to verify the validity of the proposed configurations. The proposed configurations promise to be useful in the design of dual-mode dielectric resonator filters for satellite multiplexers having stringent rejection requirements. >

In this article, a dual-mode dielectric waveguide resonator (DWR) is proposed. A dual-band bandpass filter (BPF) is fabricated using this DWR. The two passbands are constructed by a pair of higher-order modes. These higher-order modes are the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{TM}_{210}$</tex> mode and the TM120 mode, which are all from the rectangular dielectric waveguide resonator. Therefore, by changing the width of the resonator cw and the length of the resonator cl, the resonant frequencies of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{TM}_{210}$</tex> mode and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{TM}_{120}$</tex> mode are able to be changed independently. The center frequencies of the filter can be adjusted freely. To excite and extract the modes, metallized blind holes can be set where their electric-fields are the strongest. In this way, the two modes do not affect each other. The coupling structures for different modes are realized by connecting corresponding metallized blind holes. By changing the depth of metallized blind holes at different positions on the resonator, therefore, the coupling coefficients of the two passbands are able to be under control freely so as to adjust the bandwidths of the two passbands independently. At last, the designed BPF's frequencies and bandwidths are able to be controlled freely.

In this paper, a novel design of an E-plane waveguide filter, called electromagnetically induced transparency (EMIT) filter, is proposed. This EMIT filter is implemented by a rectangular ring (RR) on one side of the substrate and two strip lines resonators (SLRs) on the opposite side, which brings in electrically induced transparency and magnetically induced transparency by the electrical and magnetic couplings between the RR and SLRs, respectively. An equivalent circuit is developed further. Properties of high selectivity, low insertion loss, flat group delay, and small size of only about 0.2λg are realized by this design method. A sample has been fabricated and tested. The measured central frequency is 33.77 GHz with 3-dB fractional bandwidth of 9.4% and the minimum insertion loss in the passband is 0.5 dB. Using the proposed miniature EMIT filter, a diplexer is further designed with compact sizes and low insertion losses. The measured minimum insertion losses are 0.9 and 0.5 dB in the lower and upper passbands centered at 31.79 and 34.74 GHz with 3-dB relative bandwidths of 7.2% and 8.6%, respectively. Good agreements between the simulated and measured results are obtained both in the EMIT filter and the EMIT diplexer.

A six-cavity dielectric waveguide filter (DWF) with flat group delay characteristics in the passband is designed in this paper. Control of the coupling slot distance is achieved by opening a single-sided magnetic coupling slot. The effect of the transmission zero position on the group delay is discussed. Complex transmission zeros are introduced in the CQ structure to equalize the group delay in operation band. By analyzing the effect of the spacing of the coupling slots in the CQ on the group delay responses, the appropriate coupling coefficient is achieved. Through simulation and physical testing, a filter that meets the design specifications is obtained.

In this work, we propose novel schemes to design on-chip ultra-compact optical directional couplers (DC) and broadband polarization beam splitters (PBS) based on off-centered and asymmetric dielectric slot waveguides, respectively. Slot dimensions and positions are optimized to achieve maximum coupling coefficients between two symmetric and non-symmetric slotted Si wire waveguides through overlap integral method. We observe >88% of enhancement in the coupling coefficients when the size-optimized slots are placed in optimal positions, with respect to the same waveguides with no slot. When the waveguides are parallel, in that case, a coupling length as short as 1.73 μm is accomplished for TM mode with the off-centered and optimized slots. This scheme enables us to design optical DC with very small footprint, Lc ∼ 0.9 μm in the presence of S-bends. We also report a compact (Lc ∼ 1.1 μm) on-chip broadband PBS with hybrid slots. Extinction ratios of 13 dB and 22.3 dB are realized with very low insertion loss (0.055 dB and 0.008 dB) for TM and TE modes at 1.55 μm, respectively. The designed PBS exhibits a bandwidth of 78 nm for the TM mode (C-and partial L-bands) and >100 nm for the TE mode (S + C + L wavelength bands). Such on-chip devices can be used to design compact photonic interconnects and quantum information processing units efficiently. We have also investigated the fabrication tolerances of the proposed devices and described the fabrication steps to realize such hybrid devices. Our results are in good agreement with 3D FDTD simulations.

This paper presents the realization of a tunable bandpass filter with high selectivity and low insertion loss using one tunable composite right/left-handed (CRLH) cell. The tunable CRLH cell is proposed with varactor diodes loaded both on series and shut circuits. Two shut circuits are designed to form the needed paralleled CR and LL, by which two transmission zeros beside the passband are obtained at the same time. Each varactor diode is shunted by a lumped capacitor for lower insertion loss. The filter is tuned by only one DC bias, which results in easily control and compact size. The measured results agree well with the simulated results, and a tunable range of the center frequency from 1.75 to 2.25 GHz is achieved in measurement with the insertion loss less than 2.5 dB.

In this paper, the realization of Y-shaped dielectric dual-mode resonator filters is discussed. All resonators are composed by uniform cylindrical rods which can be soldered on different metallic cores. This enables different resonator geometries to be realized easily. The dual-mode resonators are designed to operate in the TM mode. A second order Y-shaped dual-mode filter with one real frequency axis transmission zero (TZ) as well as two different fourth order filters are designed, manufactured and measured within this paper. Depending on the geometry, the fourth order filters either reveal a complex TZ pair or even a pair of real frequency axis TZs.

Planar microwave bandpass filters (BPFs) are an essential component in many communication systems. Traditional BPF design focuses on the application of frequency-invariant K-/J-inverters inserted between the two resonant modes or served as the external coupling to feed the resonators. This design method is most suitable for narrow bandwidth BPFs, but for wideband cases it is difficult for a direct application. To solve this problem, a synthesis method based on a modified general Chebyshev function and the Richard’s transformation has been proposed to characterize the frequency response over the whole frequency range for the wideband BPF designs. As for the corresponding circuit structure, short-circuited stepped-impedance multi-mode resonators (MMRs) serve as the foundation to the designs in this dissertation. By parallel-connecting or folding the MMRs, a class of dual-wideband BPFs has been developed. Based on the above discussion, this dissertation presents the wideband BPF designs in two aspects, the proposed filter synthesis procedure and a new class of circuit structures to realize the target filtering responses. As the foundation of this research work, short-circuited MMRs have been researched in the first place for a single-wideband BPF design. n sections of cascaded commensurate lines are used to group the resonances, and short-ended stubs are shunt on its two sides to inductively feed the MMR. For the filter design, a Chebyshev filtering function is used to characterize the frequency response of the circuit. By equating the filtering function to the transfer function of the circuit, the design parameters are obtained. The first set of dual-wideband BPFs is formed by parallel-connecting two dissimilar single-wideband BPFs, both formed by stepped-impedance MMRs. The two transmitting paths of 180o phase difference are used to generate up to two pairs of transmission zeroes (TZs) with symmetry to the dual-wide passbands. By appropriately choosing the characteristic impedances of the two paralleled MMRs, one pair of TZs is located in real frequencies contributing to the attenuation between the two passbands, whereas the second pair of TZs is located in imaginary frequencies adjusting the group delay within the passbands. The short-circuited stubs, in shunt connection on the two sides of the MMR, act as the inductive loading element to feed the MMR and to flatten the passband. In the meanwhile, they introduce TZs at multiple of π to suppress the DC-component. Following a similar design principle, the second set of dual-wideband BPF has been proposed as an improved design in terms of realizing a more compact size, the greater flexibility in terms of reflection zeros in the passband and an extra degree of freedom in choosing characteristic impedances. The generic structure of the proposed filters is formed by folding a MMR along its symmetrical plane and by coupling a pair of short-circuited stubs on the two ends of the MMR. Thus, two signal transmitting paths, one from the folded MMR and another from the loaded stubs, are used to generate additional TZs between the two passbands. By increasing sections of the loaded MMR, the reflection zeros in the passband is enlarged. Under fully-coupled structure, the merit of compact size and extra design freedom is obtained. For these two sets of dual-wideband BPFs mentioned above, the even-/odd-mode analysis method has been used to derive the transfer function to characterize their frequency responses. Given the properties of the proposed filters, the commonly used generalized Chebyshev filtering function as well as its transferred dual-band function is not appropriately used herein. Instead, a generalized Chebyshev filtering function, originally developed for a single-wideband BPF design, is readily applied. By directly formulating a filtering function with mirror to the origin, it has dual passbands respectively located at positive and negative frequency ranges. To accurately account for the wideband response, a TZ is assigned at the origin. Next, the Richard’s transformation is applied to transfer the normalized frequency response to its dual-band counterpart. With this proposed synthesis procedure, the targeted filtering function is characterized by a ratio of two polynomials. By equating these two aforementioned functions, which are the ideal filtering function from the specifications and the transfer function from the circuits, all the circuit design parameters are obtained. Finally, the proposed single-/dual-wideband bandpass filters have been synthesized and designed for practical implementation. The experimental results of the fabricated filter circuits have strongly verified these new filter structures and their corresponding synthesis method proposed.

This paper shows that it is feasible to realize a quadruple-mode dielectric resonator. A half-cut of this resonator is then shown to support two modes. A new type of dual-mode dielectric resonator filters is introduced, using a cylindrical resonator cut in half along its axis. Center frequency control, intra/inter/input-coupling mechanisms, tuning, and spurious improvement methods are discussed, showing versatility of the proposed structure. Practical filter measurement results are presented which verify the proposed concept. The filter provides improvements in terms of size and mass reduction, in comparison with existing dual-mode dielectric resonator filters, while maintaining better spurious performance, with a small degradation in quality factor. It is a low-cost compact solution, suitable for both wireless and satellite applications.

In this paper, a compact 1.71-2.69GHz diplexer is designed and fabricated for mobile phone terminals based on high-resistivity silicon (HRS) integrated passive device (IPD) technology. Low insertion loss and compact size can be achieved by utilizing new LC resonances to provide transmission zeros. The chip size of the diplexer is 1.525mm×0.95mm×0.1mm. Test results show that the operating center frequencies of the low and high frequency bands of the diplexer are 1.94 GHz and 2.595 GHz, respectively. The low band maximum insertion loss is 1.3dB in 1.71GHz ~ 2.17GHz. The high band maximum insertion loss is 0.7dB in 2.5GHz ~ 2.69GHz. The isolation between two bands is better than 11.2dB in 1.71GHz ~ 2.69GHz.

A dielectric-loaded cavity filter working in the Ku-band with wide bandwidth and high selectivity is presented. The structure is composed of rectangular waveguide cavities loaded with 3-D-printed dielectric resonators. An example of a 4-pole filter is shown in this paper. The filter has three rectangular cavities loaded with three dielectric resonators made of alumina. The dielectrics have a hexagonal shape and have been designed as a single piece. They operate with the dielectric mode TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01δ</inf> and the cavity mode TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</inf> . More specifically, the mode TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01δ</inf> was exploited for cavities 1 and 3, whereas modes TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01δ</inf> and TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</inf> were exploited for the middle cavity. These combinations of modes were used in order to obtain transmission zeros (TZs) in the upper and lower stopband of the filter, and obtain as a result, a high-selective filtering response. For validation purposes, a 4-pole filter working in the Ku-band at 14.125 GHz, with 5.3% fractional bandwidth was fabricated and measured.

This paper introduces for the first time a quad-mode dielectric resonator filter, using a simple cylinder resonator. A four-pole single cavity filter is designed, simulated, and fabricated based on this quadruple mode resonator. Additionally, a new type of dual-mode dielectric resonator filters is introduced, using the same cylindrical resonator cut in half along its axis. Center frequency control, intra/inter/input-coupling mechanisms, tuning, and spurious improvement methods are discussed, showing versatility of the proposed structures to realize different filtering functions and specifications. Measured results are presented for practical filters, employing the proposed quad-mode and dual-mode resonators. The dielectric resonator filters presented in this paper offer a significant size and mass reduction in comparison with conventional dielectric resonator filters. They promise to be useful for both wireless and satellite applications.

A novel dual-mode (DM) dielectric waveguide (DW) filter with controllable transmission zeros (TZs) is presented. The DM filter is based on a cascaded implementation, utilizing individual DM DW cavities. The filter is practically realized by embedding three circular blind holes at different positions in the surface of a dielectric silver-coated square cavity. By changing the relative position of the blind holes or rotating the direction of the proposed DW cavity, the filter's TZs' frequency locations can be flexibly adjusted. The zero points can be set in frequency at the low end of the passband, at the high end of the passband, or they can be generated at both the low and high ends of the passband in order to improve the selectivity of the filter. In this study, the two-cavity fourth-order filter is taken as an example, and the experimental results validate the feasibility of the presented theoretical design.