Search Results (54)

This article investigates how to exploit the high-frequency mmWave for 5G-advanced and beyond, which requires new filters for the wide bandpass and its multi-sub-band. Based on the substrate-integrated waveguide (SIW), spoof surface plasmon polariton (SSPP), and metastructures, like complementary split-ring resonators (CSRRs), the development of a wide bandpass filter and a multi-sub-band filter is proposed, along with an experimental realization to verify the model. The upper and lower cutoff frequencies of the wide bandpass are controlled through an SIW-SSPP structure, whereas the corresponding wide bandpass and its multi-sub-band filters are designed through incorporating new metastructures. The frequency range of 24.25–29.5 GHz, which covers the n257, n258, and n261 bands for 5G applications, was selected for verification. The basic SIW-SSPP wide bandpass structure of 24.25–29.5 GHz was designed first. Then, by incorporating an Archimedean spiral configuration, the insertion loss within the passband was reduced from 1 dB to 0.5 dB, while the insertion loss in the high-frequency stopband was enhanced from 40 dB to 70 dB. Finally, CSRRs were integrated to effectively suppress undesired frequency components within the bandpass, thereby achieving multi-sub-band filters with low insertion losses with a triple-sub-band filter of 0.5 dB, 0.7 dB, and 0.8 dB in turn. The experimental results showed strong agreement with the design scheme, thereby confirming the rationality of the design. Full article

To obtain a flat top shaped passband in a conventional thin-film-based optical bandpass filter (OBF), it needs a large number of constitutional layers of thin films, which makes the film deposition systems more complicated and accumulates errors in film growth. A flat top and polarization-independent optical bandpass filter structure is proposed based on experimentally verified polarization independency in the form of a prism-pair coupled planar optical waveguide (POW). The POW is composed of two waveguide stacks, which consists of nine planar thin-film layers. Theoretical simulations show that the flat band top spans about 5 nm with transmittance over 97.8%. The passband is designed to be centered at 632.8 nm, the He-Ne laser wavelength, and the FWHM (full width at half maximum) bandwidth is about 35 nm. Within 0.5° tuning for the incident angle of the light, the passband could be shifted within 50 nm, while its transmittance fluctuates only less than 1% and the passband shape distorts only slightly. This type of OBF is potentially applicable in various fields of optical and laser spectroscopies. Full article

This paper presents our research on an E-band Radio Frequency (RF) front-end packaging structure based on back-to-back gap waveguide (GW). This design effectively mitigates the impact of air gaps on performance and offers the advantage of large assembly tolerances. Additionally, its back-to-back structure enables structural stacking, which can reduce the overall packaging size. In terms of functionality, the structure integrates hybrid couplers, bandpass filters, and amplifier packaging structures. Notably, the hybrid couplers provide high port isolation, facilitating a higher isolation duplex function by simply connecting high-order bandpass filters at the output ports without the need for additional optimization. Furthermore, these couplers also serve as power dividers/combiners. When combined with the H-plane amplifier packaging structures, the output power of the module is theoretically increased by 3 dB. Based on the measurements, the results indicate that this structure operates within the frequency ranges of 71–76 GHz and 81–86 GHz. The common port return loss is below 12 dB, while the in-band insertion loss is less than 2.26 dB and 2.42 dB, respectively. These findings demonstrate excellent electrical performance and suitability for E-band communication systems. Full article

This paper presents an E-band four-channel multiplexer based on a turnstile junction. The proposed multiplexer consists of a power distribution unit featuring a turnstile junction topology and four Chebyshev bandpass filters. Thanks to the implementation of a rotating gate connection structure as the distribution unit, the overall compactness was enhanced, and the complexity of optimization was significantly reduced. Furthermore, this configuration offers a well-organized spatial port distribution, facilitating scalability for additional channels. According to the frequency band planning and design requirements of the communication system, an E-band four-channel multiplexer was designed and manufactured using high-precision computer numerical control (CNC) milling technology, achieving an error margin of ±5 μm. The experimental results indicate that the passbands are 70.6–73.07 GHz, 73.7–76.07 GHz, 82.55–82.9 GHz, and 83.4–85.9 GHz. The in-band insertion loss of each channel is below 1.7 dB, while the return loss at the common port exceeds 12 dB. The measured results align closely with simulations, demonstrating promising potential for practical applications. Full article

This paper presents a waveguide bandpass filter that integrates bending and twisting functions, utilizing mixed TE₁₀₁ and TE₁₀₂ mode resonators. Benefiting from the mixed utilization of TE₁₀₁ and TE₁₀₂ resonators, the desired stopband suppression and low insertion loss are achieved. To verify the feasibility of this approach, a sixth-order Chebyshev bandpass filter centered at 20.4 GHz is designed, with a bandwidth of 1.6 GHz (FBW = 7.84%) and a return loss of more than 20 dB. The filter also achieves 120° bending in the propagation direction and 90° rotation in polarization. This prototype is fabricated following the stereolithography (SLA) process using photosensitive resin, followed by metallization through electroplating to achieve a lightweight design. The measurements exhibit great consistency with the simulations. Full article

Terahertz is one of the most promising technologies for high-speed communication and large-scale data transmission. As a classical optical component, ring resonators are extensively utilized in the design of band-pass and frequency-selective devices across various wavebands, owing to their unique characteristics, including optical comb generation, compactness, and low manufacturing cost. While substantial progress has been made in the study of ring resonators, their application in terahertz surface wave systems remains less than fully optimized. This paper presents several spoof surface plasmon polariton-based devices, which were realized using ring resonators at terahertz frequencies. The influence of both the radius of the ring resonator and the width of the waveguide coupling gap on the coupling coefficient are investigated. The band-stop filters based on the cascaded ring resonator exhibit a 0.005 THz broader frequency bandwidth compared to the single-ring resonator filter and achieve a minimum stopband attenuation of 28 dB. The add–drop multiplexers based on the asymmetric ring resonator enable selective surface wave outputs at different ports by rotating the ring resonator. The devices designed in this study offer valuable insights for the development of on-chip terahertz components. Full article

This work presents the design of a novel fully canonical triple-mode filter with source–load coupling for 5G applications, exploiting its very compact size for the FR1 band. The design is carried out using circular waveguide technology to attain power handling and low insertion losses. The fully canonical topology allows for increasing the selectivity of the filter since the number of finite transmission zeros is equal to the order of the filter. Given that this topology needs a source–load coupling level that is not possible to achieve with the classical iris ports, coaxial probes are used as input–output ports. A systematic procedure is developed to obtain the initial geometry before the full-wave optimization. The proof of concept is verified by a manufactured prototype at 3.7 GHz with 1.1% relative bandwidth for high coverage of 5G base stations. The results show an excellent agreement between the simulation and the measurement, validating the triple-mode filter and its underlying design process. Full article

In this paper, a compact capacitive-loaded quarter-mode substrate integrated waveguide (CL-QMSIW) resonator is proposed and analyzed. This resonator is created by loading a metal–insulator–metal (MIM) capacitor inside the QMSIW resonator. A miniaturized hybrid bandpass filter with deep stopband suppression is designed based on the CL-QMSIW resonator and the stripline resonator. The filter generates a transmission zero (TZ) that can be adjusted flexibly through cross-coupling in its lower stopband, which significantly enhances the filter’s selectivity. To verify the correctness of the proposed filter, a third-order filter was created and produced, utilizing the low-temperature co-fired ceramics (LTCC) technique. The measurement outcomes align with the results from the electromagnetic simulations. The filter is characterized by a center frequency of 7 GHz, while the core size is only $0.33{\lambda }_g\times 0.17{\lambda }_g$, and the lowest insertion loss (IL) within the band is 1.4 dB, achieving a TZ at 5.1 GHz. The proposed filter features a compact dimension, excellent selectivity, and low insertion loss. Full article

A substrate-integrated waveguide (SIW) bandpass filter (BPF) with extraordinary selectivity and an adequate upper stopband for C-band Satellite Communication (SATCOM) applications is proposed in this paper. The design comprises comb-shaped slots engraved on a half-mode SIW (HMSIW) that constitute a multimode resonator (MMR). Its performance is further ameliorated by applying the first and second iterations of the Minkowski fractal curve in the ground plane as a defected ground structure (DGS). The Minkowski fractal has advantages in terms of better bandwidth and miniaturization. The filter is first simulated using the commercial full-wave electromagnetic simulator HFSS v19 and then fabricated on a 0.062′′ (1.6 mm) FR4 with dielectric constant ε_r = 4.4. The measured results are comparable with the simulated ones and demonstrate that the BPF has a resonant frequency (f₀) of 4.75 GHz, a 3 dB bandwidth of 770 MHz (fractional bandwidth of 21.4%), an insertion loss of 1.05 dB, and an out-of-band rejection (in the stopband) of more than 28 dB up to 8 GHz, demonstrating a wide and deep stopband. Using the multimode resonator (MMR) technique, a wide bandwidth has been achieved, and by virtue of using half-mode SIW (HMSIW), the proposed BPF is compact in size. Also, the fractal DGS aids in better stopband performance. Full article

This paper presents a bandpass filter (BPF) exploiting hybrid shielded eighth-mode circular substrate-integrated waveguide (SD-EMCSIW) and complementary split ring resonator (CSRR) resonators. The proposed BPF leverages the SD-EMCSIW resonator with a 45-degree angle to create a second-order BPF with a mixed electromagnetic coupling scheme. Detailed analyses of the related electromagnetic characteristics and operating mechanisms have been performed. In order to further reduce the occupied area, the CSRR structures are embedded into the SD-EMCSIW resonators. Meanwhile, extra metallic via-holes are implemented to enhance the upper-stopband performance. A transmission zero (TZ) of the second-order BPF can be placed on either the left or right side of the passband and can be flexibly adjusted. To validate the design concept, a second-order hybrid SD-EMCSIW and CSRR BPF was designed, simulated, fabricated, and measured as a specific example. The prototype operates at a center frequency f₀ of 8.3 GHz with a 3 dB fractional bandwidth of 8.1%. Two transmission zeros are located near the right passband. The upper-stopband rejection reaches up to 15 dB at 2.85 times the center frequency f₀. Both the simulated and measured results show satisfactory agreement. Meanwhile, the overall size of the proposed hybrid SD-EMCSIW and CSRR BPF is 13.5 mm × 13.0 mm (0.37λ₀ × 0.36λ₀), featuring a compact physical dimension in the filter design. Full article

In this paper, the design of a dual-band filter based on the band gap waveguide (BGW) is presented. In the low-frequency band, the TE₂₀₁ mode rectangular waveguide cavity resonator was used to design the bandpass filter, which significantly reduces the impact of the high-frequency transmission line (TL). In the high-frequency band, a TE₁₀₁ mode cavity resonator based on the gap waveguide (GW) structure was used to design the high-frequency band filter. A lower insertion loss can be achieved with the use of all-metal structure. A dual-band filter prototype was fabricated to verify its performance. According to the measurement results, the insertion loss is less than 1.3 dB and the return loss is better than 14 dB in the frequency range of 5.92–6.06 GHz; and the insertion loss is less than 1.77 dB and the return loss is better than 15 dB in the frequency range of 80.6–86.2 GHz. The frequency ratio is as large as 13.9, and because the high-frequency band filter is embedded in the cavity resonator of the low-frequency band filter, it saves space to a certain extent and realizes the integrated design of the dual-band filter, which is of great significance for the improvement of the performance of the dual-band communication system in higher-frequency bands. Full article

This article presents a multiband bandpass filter structure with an in-line topology based on substrate-integrated waveguide (SIW) technology. A multi-layer configuration is employed to achieve circuit miniaturization. By constructing the coupling matrix, the coupling relationships among all resonators are quantitatively characterized, enabling the extraction of the theoretical frequency response and guiding circuit modeling and optimization. We designed and fabricated a third-order tri-band SIW filter and a third-order quad-band SIW filter, achieving a return loss of nearly 20 dB across all passbands. The close agreement between simulated and measured results validates the proposed design model. Additionally, the high in-band isolation of over 40 dB is demonstrated between all adjacent bands, highlighting the potential applicability of this technology in multiband scenarios. Full article

The proliferation of the Internet of Things (IoT) propels the continuous demand for compact, low-cost, and high-performance multiband filters. This paper introduces a novel low-profile dual-band bandpass filter (BPF) constructed with a back-to-back coupled pair of shielded folded quarter-mode substrate integrated waveguide (SF-QMSIW) multimode cavities. A hybrid structure is obtained by etching a coplanar waveguide (CPW) coupling line in the folded cavity’s septum layer. It serves multiple functions: generating an additional resonance, providing a separate coupling mechanism for the upper passband, and offering the flexibility to control the passbands’ center frequency ratio. Additionally, the unused second higher-order mode is suppressed by integrating embedded split-ring resonators (ESRRs) with an inter-digital capacitor (IDC) structure into the feed lines. A filter prototype has been fabricated and experimentally tested. The measurements confirmed reliable operation in two passbands having center frequencies 3.6 GHz and 5.8 GHz, and exhibiting 3 dB fractional bandwidths (FBWs) of 6.4% and 5.3%, respectively. Furthermore, the group delay variation within both passbands equals only 0.62 ns and 1.00 ns, respectively. Owing to the second higher-order mode suppression, the filter demonstrated an inter-band rejection exceeding 38 dB, within a compact footprint of 0.71${\lambda }_g^2$ (with ${\lambda }_g$ being the guided wavelength at the lower passband’s center frequency). Full article

In this paper, a W-band waveguide bandpass filter with a standard fourth-order Chebyshev response is proposed based on the computer numerical control (CNC)-milling technology. The harmonics-staggered technique and orthogonal coupling method are incorporated into this waveguide filter design without increasing the complexity of the filter structure in order to suppress the intrinsic spurious responses near the passband. Furthermore, the proposed filter design maintains a simple construction, which can be conveniently fabricated using CNC milling. The fabricated waveguide filter exhibits an average insertion loss of 0.9 dB and a return loss of above 20 dB in a 3 dB fractional bandwidth (FBW) of 5.5% centered at 85 GHz. The excellent spurious suppression property can reach better than −25 dB up to 165 GHz. The wide stopband performance of the proposed W-band filter is very competitive compared with the reported waveguide filters. Full article

In this paper, a novel broadband balanced-to-balanced (BTB) filtering power divider (FPD) utilizing the half-mode substrate-integrated waveguide and spoof surface plasmon polariton (HMSIW-SSPP) hybrid transmission line is introduced. Initially, a new HMSIW-SSPP unit cell is proposed, demonstrating a lower upper cut-off frequency compared to the classical HMSIW-SSPP unit cell. Building upon this unit cell, a bandpass BTB FPD is devised employing dual-layer stacked substrates, enabling independent control over the passband’s lower and upper cut-off frequencies through specific physical dimensions. Additionally, the incorporation of isolation resistors and defected ground structures in the BTB FPD enhances differential-mode isolation and common-mode (CM) suppression between output ports. A manufactured and tested BTB FPD prototype validates this design method, showcasing a broad fractional bandwidth of 52.31% (6.72–11.48 GHz), output port isolation surpassing 14.25 dB, and transmitted CM suppression exceeding 34.05 dB. Full article