In this brief, a dual-mode dual-band filter based on half-mode substrate integrated waveguide (HMSIW) is presented. The proposed filter has the capability to tune the two pass-bands independently. The proposed filter consists of two HMSIW resonators coupled through a pair of ${E}$ -shaped coupling slots. Two resonating modes ( TE 101 and TE 102) are excited in each resonator. A varactor diode is used in the proposed filter for tuning purpose. The varactor diode is placed in the structure in such a way that both bands can be tuned independently. The lower passband can be tuned from 3.26 to 3.47 GHz with insertion loss of 0.2–2.9 dB. The higher passband can be tuned from 5.47 to 6.13 GHz with low insertion loss of 0.1–2.1 dB. The presented results show the flexibility of the filter to achieve desired responses and its suitability for integration with any tunable planar structure. A good agreement between the simulated and measured results is observed.

Dual-Band Half Mode Substrate Integrated Waveguide Filter With Independently Tunable Bands

This brief propose the design and measurement of tunable, highly selective and wide-stopband microwave filters using substrate integrated waveguide (SIW) technology. A two pole filter is designed using optimized cavity parameters. Two higher order (4-pole) filters are designed by connecting two cavities vertically and horizontally through coupling slots. In this way, four poles are achieved in two cavities, in which the proposed filter produces $2\times \text{N}$ poles in N cavities. A varactor diode is employed in both configurations to make the filters tunable. The proposed filters have wide upper stopband performance [20 dB up to $4.8f_{1}$ (Filter 1) and 20 dB up to $4.2f_{1}$ (Filter 2)], lower insertion losses [0.2-1.1 dB (Filter 1) and 0.2-1.5 dB (Filter 2)] and good tunability ranges [2.7–3.4 GHz (Filter 1) and 3.1–3.9 GHz (Filter 2)]. In order to validate the proposed design, a prototype is fabricated on RT/duroid 5870 substrate and measured. The simulated results accord closely with the measured results.

Tunable SIW Bandpass Filters With Improved Upper Stopband Performance

The progress of technology in consumer electronics demand an antenna having a compact size, high gain and bandwidth, and multiple antennas at transmitter and receiver to enhance the channel capacity. Over the last decade, numerous techniques are proposed to improve the performance of the antenna. One such technique is the use of metamaterials (MTMs) in antenna design. MTMs are artificial structures to provide unique electromagnetic properties that are not available in natural materials. The unique properties of these materials allow the design of high-performance antennas, filters, and microwave devices which cannot be obtained using traditional antennas. Loading antenna with the one, two, and three-dimensional MTM structures comprised of a periodic subwavelength unit cell exhibits RLC resonant structures and allows to manipulate electromagnetic waves in the antenna system. These structures offer low resonant frequency compared to the antenna resonant frequency resulting in antenna miniaturization and manipulation of electromagnetic waves helps in enhancing the gain and bandwidth, and achieving circular polarization (CP) of an antenna system. Also, metamaterial loading enhances isolation between the antenna elements in the multiple-input-multiple output (MIMO) system by suppressing the surface waves. In this paper, the electromagnetics of MTM with analytical expressions and its application in antenna design are discussed in detail. The MTM-based antennas are classified into MTM loading, MTM inspired antenna, metasurface loading, and composite right/left hand (CRLH) based antennas. The recent development in MTM inspired antenna and its application in antenna miniaturization, enhancing gain and bandwidth, achieving CP and mutual coupling suppression in MIMO antenna systems are discussed to make it useful for further research.

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Electromagnetic Metamaterials: A New Paradigm of Antenna Design

In this article, novel millimeter-wave (mmWave) filtennas (filtering antennas) are proposed to realize compact size and low insertion loss for 5G applications. It is achieved by employing eighth-mode substrate-integrated waveguide (EMSIW) cavities fully shielded by metallized vias and cover as resonators, which are named as fully shielded EMSIW (FSD-EMSIW) cavities. Interdigital coupling between cavities is introduced in order to obtain higher coupling strength for wideband operation. The proposed single-polarized antenna consists of a feeding stripline, two FSD-EMSIW cavities, and two stacked square patches, generating the four-order filtering antenna response. Furthermore, this design has been extended to realize a dual-polarized filtenna by employing double sets of feeding network. For demonstration, single-/dual-polarized filtenna prototypes were fabricated and measured, the measured results show that the 5G mmWave band (24.25–29.5 GHz) can be covered with average gains of 4.5 dBi. Good bandpass filtering response is also observed. Finally, to validate the proposed idea in array applications, a 16-element filtenna array is designed and measured with good performance.

SIW Cavity-Fed Filtennas for 5G Millimeter-Wave Applications

A class of tunable multi-band bandpass filters (BPFs) that is based on a quasi-bandpass topology is presented. Unlike other approaches, it features a quasi-elliptic-type filtering response with controllable passbands in terms of center frequency and bandwidth. Additional transmission zeros (TZs) are produced through cross couplings that are introduced between adjacent quasi-bandpass sections through their non-resonating nodes (NRNs). These TZs are synchronously tuned with passband reconfiguration. The lack of direct interaction among the resonating nodes of this multi-band BPF architecture results in a transfer function with high tuning robustness. Furthermore, when compared to prior-art coupled-resonator multi-band BPF designs, a reduced number of inverters are needed when synthesizing a large number of transmission bands. For the first time, the coupling-matrix formalism of the engineered multi-band BPF is expounded. In addition, a microstrip dual-band BPF prototype with mechanically-variable capacitors is manufactured and characterized for experimental demonstration purposes.

Quasi-Elliptic Multi-Band Filters With Center-Frequency and Bandwidth Tunability

This letter presents a half-mode substrate integrated cavity bandpass filter with both continuous center frequency and 3 dB bandwidth tuning capabilities. The filter adopts a superposed two layers PCB with lumped varactors loading the central resonator to tune the center frequency. The first-invented semicircular metal sheet on the center rod not only reduces the filter size given a certain resonant frequency significantly by increasing the capacitance between the semicircular metal and the upper ground metal but also facilitates fine frequency tuning by using appropriate varactor $C_{\mathrm{tune}}$ . Surface mount varactors between two resonators change the inter-resonator coupling to adjust the 3 dB BW. Another varactor on the feed line can be used to adjust the external coupling. This filter demonstrates a BW range of 75–130 MHz around 1.5 GHz, a 3 dB BW range of 46–130 MHz around 1.3 GHz and a 3 dB BW range of 55–90 MHz around 1.11 GHz with 10 dB minimum return loss. Insertion loss ranging from 2.262 dB to 7 dB have been obtained.

A Half-mode Substrate-Integrated Filter With Tunable Center Frequency and Reconfigurable Bandwidth

A novel varactor tunable dual-band bandpass filter (BPF) using stub-loaded stepped-impedance resonators is proposed in this letter. Compared with the traditional tunable filters, the source-load coupling and T-shape stub-loaded lines are employed in this design. The proposed BPF architecture has the advantages of high selectivity and less control voltages. In the overall tuning range, the proposed filter is designed with 5–6 transmission zeros and more than 30 dB rejection between the two passbands. Meanwhile, only one control voltage is needed for each passband. A prototype of this filter is fabricated and measured. The measurement results show great agreement with simulated results, which show that the first passband can be tuned in a frequency range from 0.8 to 1.02 GHz, and the second passband varies from 2.02 to 2.48 GHz.

A High-Selectivity Tunable Dual-Band Bandpass Filter Using Stub-Loaded Stepped-Impedance Resonators

This article presents a novel class of dual-mode substrate-integrated waveguide (SIW) bandpass filters exploiting perturbed SIW rectangular cavities. By introducing metallized via-holes along the central line of an SIW rectangular cavity, the resonant frequency of TE101 mode can be shifted close to that of TE201 mode, thus creating a dual-mode resonator. This structure implements a doublet, which provides two poles and one or two transmission zeros (TZs). The pass bandwidth, spurious-free bandwidth, and positions of the TZs can be fully controlled by modifying the length of the perturbation, the side ratio of the rectangular cavity, and the offset of the input/output ports, respectively. Eight two-pole SIW filters are designed and investigated to demonstrate the high design flexibility. Moreover, a four-pole SIW filter with the asymmetric response and a five-pole SIW filter with quasi-elliptic response are designed, fabricated, and measured to describe the extension of the proposed approach to higher order filters.

Planar Dual-Mode Bandpass Filters Using Perturbed Substrate-Integrated Waveguide Rectangular Cavities

This letter presents a miniaturized eighth-mode substrate-integrated waveguide (EMSIW) filter with tunable center frequency and variable bandwidth. The filter uses a stub-capacitor-loaded EMSIW structure which not only achieves miniaturization but also tunes the center frequency. The edge electrical coupling strength between the two resonators can be adjusted by loading varactor to achieve the bandwidth tunability. In addition, two transmission zeros are introduced to improve the upper stopband rejection. Both the simulated and measured results show a center frequency tuning range of 2.17–2.72 GHz, as well as demonstrate a 3-dB BW tuning range of 140–208 MHz around 2.17 GHz, 231–355 MHz around 2.45 GHz, and 314–435 MHz around 2.72 GHz. The measured insertion loss is 1.7–4.8 dB, and the return loss is better than 10 dB for all tuning ranges.

A Miniaturized Eighth-Mode Substrate-Integrated Waveguide Filter With Both Tunable Center Frequency and Bandwidth

The contribution of this paper is to present a reconfigurable double-layer half-mode substrate integrated waveguide (HMSIW) bandpass filter with continuous center frequency and 3 dB bandwidth (BW) ...

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Papers

A Half-mode Substrate-Integrated Filter With Tunable Center Frequency and Reconfigurable Bandwidth

A High-Selectivity Tunable Dual-Band Bandpass Filter Using Stub-Loaded Stepped-Impedance Resonators

Planar Dual-Mode Bandpass Filters Using Perturbed Substrate-Integrated Waveguide Rectangular Cavities

A Miniaturized Eighth-Mode Substrate-Integrated Waveguide Filter With Both Tunable Center Frequency and Bandwidth

The novel reconfigurable double-layer half-mode SIW filter with tunable DMS structure