Half mode substrate‐integrated waveguide‐loaded evanescent‐mode bandpass filter

In this article, a filter size reduction of 46% is achieved by reducing a substrate‐integrated waveguide (SIW)‐loaded evanescent‐mode bandpass filter to a half‐mode SIW (HMSIW) structure. SIW and HMSIW filters with 1.7 GHz center frequency and 0.2 GHz bandwidth were designed and implemented. Simulation and measurements of the proposed filters utilizing combline resonators have served to prove the underlying principles. SIW and HMSIW filter cavity areas are 11.4 and 6.2 cm², respectively. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

A broadband filter based on hybrid spoof surface plasmon and half‐mode substrate integrated waveguide structure

In this article, a novel design way of wideband bandpass filter (BPF) is proposed. A hybrid sharing waveguide based on spoof surface plasmon (SSP) and half‐mode substrate integrated waveguide (HMSIW) is developed. With low‐pass feature of SSP and high‐pass feature of HMSIW, the proposed waveguide is a BPF naturally and the filter bandwidth can be controlled by adjusting parameters easily. A filter sample is fabricated for verification and the measured 3‐dB bandwidth is 46%. The proposed new concept of filter design is attractive and can be used to develop different wideband BPFs.     

A novel substrate integrated waveguide equivalent inductive‐post filter

A novel substrate integrated waveguide equivalent inductive‐post filter is presented and optimally designed by HFSS and equivalent circuit method. The filter is fabricated with a standard low cost PCB process. Measured data are in agreement with the simulated results. Excellent performance in selectivity, out of band rejection and passband insertion loss are shown. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

A novel wideband bandpass filter based on CSRR‐loaded substrate integrated folded waveguide

A novel wideband bandpass filter based on folded substrate integrated waveguide (FSIW) is presented in the article. Five square complementary split‐ring resonators (CSRRs) are etched in the middle layer of the FSIW. By adjusting the physical size of the CSRR structure, the resonant frequency of the CSRRs can be tuned at the same time and the stopband performance can be changed. As transverse electromagnetic (TEM) mode can be transmitted in the stripline, FSIW excited by stripline shows wider passband than that excited by microstrip line directly. To achieve perfect impedance matching, two microstrip lines to stripline transitions are added in two ports of the filter. The proposed bandpass filter exhibits compact size, high selectivity, good stopband rejection, lower radiation loss, and wideband performances. The measured results show that the fractional bandwidth of the filter is about 35.5%. The measured return loss is better than 15 dB from 4.84 GHz to 6.90 GHz, and the insertion loss is less than 1.2 dB. The comparison between the simulated results and the measured ones validate the possibility of the technology that combines the FSIW and CSRR.     

A novel circularly polarized half mode circular substrate integrated waveguide antenna using meandered strip feeding technique

A technique to design a compact half mode substrate integrated circular cavity (HMSICC) cavity backed antenna is presented in this letter. The proposed antenna achieves left‐handed circularly polarized(LHCP) using a crossed slot, The feeding meandered stripline on the middle layer are able to achieve better impedance match and axial ratio bandwidth. Measured results show that the prototype achieves a bandwidth of 10.5% for ?10dB return loss, axial ratio(AR) bandwidth is about 3% with maximum gain of 6.5dBi. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:668–673, 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.     

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.     

Wideband bandpass filter based on U‐slotted SW‐HMSIW cavities

A wideband bandpass filter (BPF) is designed based on U‐slotted slow wave half mode substrate integrated waveguide (SW‐HMSIW) cavities. Similar to the substrate integrated waveguide (SIW), the SW‐HMSIW can also achieve a highpass characteristic while the lateral dimensions can be reduced by about 50%. By etching a U‐shape slot on the SW‐HMSIW cavity, a multiple‐mode resonator (MMR) can be realized, which can achieve a wide passband response and make the overall dimension of the filter much more compact. A wide passband, covering from 6.0 GHz to 10.65 GHz with a FBW about 58.13% is achieved. The measured minimum insertion losses including the losses from SMA connectors are 1.1 dB and return losses are better than 10 dB. Besides, the group delay varies between 0.2 and 0.5 ns within the passband. To validate its practicability, a wideband SW‐HMSIW BPF fabricated on a double‐layer printed circuit board (PCB) is designed and examined. The proposed filter has a more than 54% size reduction compared to the other designs reported in open literatures. The measured results have a good agreement with the simulated results. The effective size of the fabricated filter is about 27 mm × 8.55 mm.     

A dual band leaky wave antenna based on modified substrate integrated waveguide

In this article, a new leaky wave antenna (LWA) based on modified substrate integrated waveguide (SIW) is introduced. At first, the modified SIW structure is presented and it is shown that it supports propagation of quasi‐TEM with nearly uniform electric field distribution. Then, a new cell based on diagonal‐shaped slots embedded on top surface of the structure is introduced and its dispersion characteristics and its different radiation regions are determined. A LWA made of 15 unit cells is designed and a prototype of the antenna is fabricated. The proposed LWA is simulated using a software package and its radiation characteristics are also measured. It is shown that a good agreement is obtained between simulated and measured results and two frequency bands are obtained. In the frequency range of 7 GHz to 8.25 GHz, it radiates in forward region with maximum gain of 11.3 dB and scan angles from 54° to end‐fire. In addition, it radiates in backward region from ?70° to broadside from 14 GHz up to 20 GHz with maximum gain of 16.47 dB. High gain, compactness, and wide scan angles are the advantages of the proposed LWA.     

Planar integrated substrate integrated waveguide circularly polarized filtering antenna

A new design of substrate integrated waveguide (SIW) circularly‐polarized (CP) filtering antenna is presented, which is based on dual‐mode (TE₁₀₂ and TE₂₀₁) cavities. The satisfying filtering performance of the antenna is realized by a coupled‐resonator circuit of two dual‐mode SIW cavities. And the radiating element of the antenna is a cavity‐backed CP slot antenna which is formed by a nonuniform ring slot integrated with the back cavity. To demonstrate the idea, a prototype antenna operating at X band is designed, fabricated, and measured. Measured results show that the 10‐dB impedance bandwidth is 4.2% (from 11.6 to 12.1 GHz), the 3‐dB axial‐ratio (AR) bandwidth is 4%, and the gain is 5.6 dBi at the center frequency of 11.8 GHz.     

Compact,dual-band,and hybrid filter based on combline and substrate integrated waveguide resonators

A novel compact hybrid dual-band bandpass filter based on combline and substrate integrated waveguide (SIW) resonators is proposed. By exploring an SIW-based hybrid cavity structure, a controllable dual-band response is achieved. The low-frequency passband is obtained by the combline, or mushroom resonators and the high-frequency passband is formed by the TE₁₀₁ and TE₃₀₁ modes. Unlike other designs that use the main mode and the high-order mode of the same resonator, we innovative use the TE301 mode of the rectangular cavity and cleverly divide this rectangular cavity into two small cavities, and use its TE101 mode to form the second passband with the TE301 mode of the large cavity. To improve the selectivity and out-of-band suppression, three transmission zeros are configured in this design. In order to verify the proposed design concept, a compact dual-band filter using this hybrid resonance structure is fabricated and measured. It demonstrates good filtering performance, including a compact size of 0.45 × 1.09 λ₀, a low insertion loss of 0.57 and 1.67 dB in the two bands, and a high-design flexibility.     

Miniaturized substrate integrated waveguide filter using fractal open complementary split‐ring resonators

A miniaturized substrate integrated waveguide (SIW) bandpass filter using fractal open complementary split‐ring resonators (FOCSRRs) unit‐cell is proposed. The proposed structure is realized by etching the proposed FOCSRR unit‐cells on the top metal surface of the SIW structure. The working principle of the proposed filter is based on the evanescent‐mode propagation. The proposed FOCSRRs behave as an electric dipoles in condition of the appropriate stimulation, which are able to generate a forward‐wave passband region below the cutoff frequency of the waveguide structure. Since, the electrical size of the proposed FOCSRRs unit‐cell is larger than the conventional OCSRRs unit‐cell; therefore, the FOCSRR unit‐cell is a good candidate to miniaturize the SIW structure. The proposed filter represents high selectivity and compact size because of the utilization of the sub‐wavelength resonators. The introduced filter is simulated by a 3D electromagnetic simulator. In order to validate the ability of the proposed topology in size reduction, 1‐ and 2‐stage of the proposed filters have been fabricated based on the standard printed circuit board process. The measured S‐parameters of the fabricated filters are in a good agreement with the simulated ones. The proposed SIW filters have many advantages in term of compact size, low insertion loss, high return loss, easy fabrication and integration with other circuits. It is the first time that the FOCSRR unit‐cells were combined with the SIW structure for miniaturization of this structure. Furthermore, a wide upper‐stopband with the attenuation >20 dB in the range of 3–8 GHz is achieved. The results show that, a miniaturization factor about 75.5% has been obtained.     

Compact half‐mode SIW cavity filters designed by exploiting resonant mode control

This article presents a novel band‐pass filter topology, based on the half‐mode substrate integrated waveguide (HMSIW), which allows for the simple design and easy manufacturing of filters with different bandwidth and number of poles. The design strategy, based on the modification of HMSIW cavity modes, is discussed in the case of two‐pole and four‐pole filters, and two prototypes are implemented and experimentally verified. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:72–79, 2016.     

Ultra‐wideband bandpass filter on coplanar waveguide: Proposal and implementation

In this paper, a novel ultra‐wideband (UWB: 3.1 ～ 10.6 GHz) bandpass filter on coplanar waveguide (CPW) is presented, designed and implemented. At first, an open‐ended nonuniform or multiple‐mode resonator with three distinctive sections is constructed and investigated toward generating the first three resonant modes occurring around the lower‐end, center, and higher‐end of the UWB band. Then, a CPW interdigital capacitor element with enlarged ground‐to‐ground distance is characterized to excite two additional resonant poles below and above the UWB's center. As a result, a five‐pole UWB bandpass filter with only one full‐wavelength is constituted. Its performance is studied on the basis of a simple cascaded transmission‐line network, whose parameters are extracted from our self‐calibrated method of moments. After the optimized results are confirmed by full‐wave simulation over the filter layout, a UWB filter sample is fabricated to demonstrate the actual UWB passband behavior with the 2.8–10.2 GHz bandwidth, where the insertion loss is less than 1.5 dB and variation in group delay is less than 0.33 ns. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Compact metamaterial unit‐cell based on stepped‐impedance resonator technique and its application to miniaturize substrate integrated waveguide filter and diplexer

In this article, a new miniaturized metamaterial unit‐cell using stepped‐impedance resonator technique is proposed. The proposed unit‐cell is used to miniaturize the physical size of the conventional complementary split‐ring resonators (CSRRs). In the proposed unit‐cell which is called complementary G‐shaped resonator (CGR), the slot line in the conventional circular CSRR is replaced with the stepped‐impedance slot line. As well as, by carving two trapezoidal shapes inside the inner ring, the resonance frequency of the proposed CGR unit‐cell has been more decreased. Compared to the conventional circular CSRR structure, the electrical size of the proposed CGR is decreased and miniaturization is occurred. To investigate the performance of the proposed CGR unit‐cell in the size reduction, two substrate integrated waveguide filters and a diplexer are designed. To validate the proposed miniaturization technique, the designed filters and diplexer loaded by the CGR unit‐cell are fabricated and measured. The measured results are in a good agreement with the simulated ones. The results shows that, a miniaturization factor about 0.69 is achieved.     

Design of miniaturized substrate integrated coaxial line bandpass filters with quarter‐wavelength spiral resonator

In this article, several miniaturized bandpass filters (BPFs) with substrate integrated coaxial line quarter‐wavelength spiral resonators were proposed. The coupling coefficients and external quality factors of proposed structures were examined by using the commercial simulation software. With different combinations of the proposed resonators, three two‐order and two high‐order miniaturized BPFs operating at 1.2 GHz with 3‐dB fractional bandwidth of 8% were designed, fabricated, and measured. The measured results showed that all the return losses were better than 10 dB over the entirely passbands, and the overall circuit sizes of two‐order and high‐order BPFs were only 0.044λ₀ × 0.028λ₀ and 0.047λ₀ × 0.047λ₀, where λ₀ is the wavelength in free space at the center frequency of the passband. Good agreements were observed between the simulated and measured results. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:489–495, 2016.     

A new type of the air‐filled substrate integrated gap waveguide resonator

This article presents the design and analysis of an air‐filled substrate integrated gap waveguide (ASIGW) resonator. The electromagnetic field of each resonant mode in the resonator is studied by theoretical modeling and EM simulation. Besides, the relationship between the dimensions and Q_u is analyzed and the Q_u of the resonator can be as high as 2080 at Ku band. Compared with conventional rectangular waveguide resonator and gap waveguide (GW) resonator, the proposed ASIGW resonator can be fabricated more easily. Compared with the substrate integrated waveguide resonator, the ASIGW resonator is more tolerant with dimensional errors and with less degenerate modes. As an example, a fifth‐order band‐pass filter based on the ASIGW resonators is presented to verify the previous conclusions.     

Design and optimization of cross‐coupled substrate integrated waveguide filters using space mapping method

This work presents an efficient method for the design of substrate integrated waveguide (SIW) filters. The proposed design approach is based on a combined use of equivalent circuit model of a filter and a space mapping technique. A reduced number of full‐wave evaluations are needed, leading to a reduced optimization time. A novel SIW filter with improved stop‐band characteristic using cross‐coupling has been proposed. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:360–366, 2014.     

A novel symmetrical folding miniaturized substrate integrated waveguide tunable bandpass filter

In order to improve the utilization of spectrum resources, dynamic frequency allocation technology has become a method of spectrum saving. The research of electric tunable filter has received much attention in recent years. Substrate integrated waveguide (SIW) is a new technology of microwave integration in the field. The innovation of this article is to combine the SIW miniaturization technology with tunable technology. In this article, a miniaturized symmetrically folded substrate integrated waveguide (SFSIW) filter is designed. Based on the miniaturization of SIW filter, the center frequency can be adjusted electrically and the measured data show that the tunable filter can achieve eight states under the condition that the bandwidth below ?3 dB remains approximately constant 300 MHz. The center frequency varies from 3.23 GHz to 3.9 GHz. The range of the filter's insertion loss is 1.2 dB to 2.04 dB, and the return loss is higher than 20.9 dB. This filter has practical value in the electronic countermeasures of military communication.     

Novel single-layer dual-band half-mode substrate integrated waveguide filter and filtering power dividers with very compact sizes

In this article, a novel single-layer dual-band (DB) half-mode substrate integrated waveguide (HMSIW) filter and three equal/unequal DB HMSIW filtering power dividers (FPDs) with super-compact sizes have been proposed. In order to design the proposed devices, the evanescent mode technique and the metamaterial concept have been used, simultaneously. Two passbands have been generated below the cut-off frequency of the HMSIW structure by etching a new compact DB metamaterial unit cell with effective negative permittivity in two different frequencies on the metal surface of the HMSIW structure. The center frequencies of these two passbands can be simply controlled by changing the size of the DB metamaterial unit cell. To confirm the design concept, three prototypes of the DB structures working at 2.4 and 3.5 GHz are simulated, constructed, and measured. The overall dimension of the designed DB HMSIW filter and DB HMSIW FPDs are approximately 0.12 λ_g × 0.11 λ_g. Compared to other existing devices, the performance of the proposed structures is very satisfactory. Compact size, easy integration, easy fabrication process, low cost, low loss, and high selectivity are the advantages of the designed structures.