Substrate Integrated Waveguide Line Research Articles

SIW based in-phase Gysel equal power divider for X-band application

This article presents a novel approach to designing fixed-width Gysel equal power divider (PD) in Substrate integrated waveguide (SIW) technology. Since the width and impedance of SIW are functions of its cut-off frequency, therefore, conventional Gysel PD design equations become non-applicable in SIW technology. Keeping this constraint, dependency of SIW line widths on operating frequency, novel design equations for the equal Gysel PD are derived for the fixed width line. Based on the derived equations, a circuit model of Gysel PD is developed, and the results are presented at 10 GHz. A simulation analysis of the proposed PD in SIW technology is carried out to support the theoretical analysis. Further, a prototype of the device is fabricated, and measurements have been done. From the experimental results, the reflection coefficients of all the ports are better than 15 dB, and isolation is better than 25 dB for the entire frequency band 9.5 to 10.5 GHz. The insertion loss varies between 1.88 to 3.28 dB in the operating band.

A technique for the passband and stopband control of wideband band-pass substrate integrated waveguide (SIW) filters designed with elliptic stepped impedances

In this paper, a design technique based on a stepped impedance synthesis is proposed for the first time for the passband and stopband control of band-pass filters in substrate integrated waveguide (SIW) technology. The structure of the band-pass filters is implemented by means of elliptic patterns etched on the top side of the SIW, which work as impedance inverters. The design method consists of previously mapping the height of the elliptic patterns and the phase shift (cut-off angle) of the SIW lines, connected to the input and output ports of the ellipses, as a function of the passband and stopband characteristics of various stepped impedance SIW filters, to then select the design parameters of the band-pass SIW filter that achieve the desired frequency response. This new approach is applied to the design of two fourth-order Chebyshev stepped impedance band-pass SIW filters with different passband and stopband characteristics. One of the band-pass SIW filters is characterized by a fractional bandwidth FBW1 = 14.5% and a spurious-free range SFR1 = 2.8 GHz, while the other filter has a FBW2 = 22.3% and a SFR2 = 1.55 GHz. Both band-pass filters were designed with a SIW TE10 mode cut-off frequency and a higher passband cut-off frequency fixed at fcTE10 = 2.85 GHz and fc,H = 3.9 GHz, respectively. Electromagnetic (EM) simulations showed that the lower passband cut-off frequency fc,L can vary with respect to fc(TE10) by 13.6% and that the first spurious frequency can appear higher than fc,H by 69.3%. The measurement results agreed well with the EM simulations, thus confirming that this method can be useful to design high-performance wideband Chebyshev stepped impedance band-pass SIW filters with a high degree of control on the passband and stopband characteristics.

Compact UWB Half-Mode SIW Bandpass Filter With Fully Reconfigurable Single and Dual Notched Bands

Compact ultra-wideband (UWB) bandpass filters based on the half-mode substrate integrated waveguide (SIW) with fully reconfigurable single and dual notched bands are proposed in this article. The lower stopband of the UWB bandpass filter is formed by the intrinsic cutoff frequency of the half-mode SIW, and transmission zeros in the upper stopband are created by utilizing three U-shaped slot resonators. Coupling microstrip resonators loaded by varactor diodes are placed along the open side of the half-mode SIW and microstrip feeding line to construct the in-band notches. By controlling the bias voltages and the size of resonators, fully reconfigurable single and dual notched bands can be obtained. Moreover, the frequency and bandwidth of each notched band can be controlled independently. To demonstrate the proposed technique, five and seven distributed coupling microstrip resonators are first applied to obtain the fully reconfigurable single notched band with the suppression level of 30 and 36 dB, respectively. Then, reconfigurable dual notched bands are demonstrated by changing the bias voltages using the same prototype with seven resonators. At last, nine resonant cells with two sets of different sizes are shown to design reconfigurable dual notched bands with frequency tuning range covering almost the full UWB passband.

Ka-Band Passive Phased-Array Antenna With Substrate Integrated Waveguide Tunable Phase Shifter

A low-cost and low-profile Ka-band passive phased-array antenna (PAA) using continuously tunable substrate-integrated waveguide (SIW) phase shifter is presented in this article. The phase shifting mechanism is based on perturbing the electric field of the slotted SIW (SSIW) line by putting a high dielectric constant slab over the slot of SIW. A systematic approach based on a simple transmission line (TL) circuit model which can support different modes is developed as a fast method for design optimization. It provides insightful physical understanding of the operating mechanism of the proposed phase shifter. In addition, a fully verified TL model of the 1 x 4 SIW PAA is presented and used to predict and optimize the overall reflection coefficients and radiation patterns at different scanning angles. The TL circuit model is verified by full-wave simulations. As a design example, a 1 x 4 SIW-based phased-array is designed, fabricated, and measured to validate phase shifter performance and capabilities. The prototype exhibits a continuous beam scanning range from -20° to +20° covering the whole operating band of 29-31 GHz.

Substrate Integrated Waveguide Bandpass Filtering With Fourier-Varying Via-Hole Walling

In this article, an optimization-driven methodology is proposed for the design of substrate integrated waveguide (SIW) bandpass filters (BPFs) with predefined passbands. The width between the metallic walls of via-holes is governed by a truncated Fourier series to achieve the desired filtering performance. The theory of rectangular waveguide is used to establish the optimization framework and obtain the series coefficients under predefined physical constraints. Two types of end-terminations are studied; specifically, with and without SIW-to-microstrip transitions. To validate the proposed methodology, two Ku-band BPF prototypes with 2.5% and 5.8% 15-dB fractional bandwidth (FBW) are designed, simulated, and measured. Furthermore, the half-mode SIW (HMSIW) concept is incorporated in one prototype to facilitate a miniaturized physical structure. Simulations and measurements are in close proximity with passband matching and transmission losses better than -15 dB and -2.5 dB, respectively. The proposed methodology allows for designing BPFs with predefined wideband or narrowband FBW by modifying the underlying physical constraints and optimization parameters. The resulting filters are planar, compact, and have wide stopband rejection. In addition, a derivation for the characteristic impedance of the SIW line is provided, which can be used to find the optimum SIW-to-microstrip transition without performing a parametric study.

Fabrication of Microwave Devices Based on Magnetic Nanowires Using a Laser-Assisted Process.

This paper compares two laser-assisted processes developed by the authors for the fabrication of microwave devices based on nanowire arrays loaded inside porous alumina templates. Pros and cons of each process are discussed in terms of accuracy, reproducibility and ease of fabrication. A comparison with lithography technique is also provided. The efficiency of the laser-assisted process is demonstrated through the realization of substrate integrated waveguide (SIW) based devices. A Nanowired SIW line is firstly presented. It operates between 8.5 and 17 GHz, corresponding to the first and second cut-off frequency of the waveguide, respectively. Next, a Nanowired SIW isolator is demonstrated. It shows a nonreciprocal isolation of 12 dB (corresponding to 4.4 dB/cm), observed in absence of a DC magnetic field, and achieved through an adequate positioning of ferromagnetic nanowires inside the waveguide cavity.

Compact Leaky SIW Feeder Offering TEM Parallel Plate Waveguide Launching

A planar and low-cost parallel-plate waveguide (PPW) launcher based on substrate integrated waveguide (SIW) technology is proposed. It can launch the fundamental TEM mode with a collimated wave front into a PPW structure while also being low profile and easy to fabricate. The launcher is implemented using a network of SIW transmission lines and its design is based on the leaky-wave (LW) theory. In our proposed structure, a selection of the SIW lines is made to leak power into the desired PPW region by means of a partially reflective surface, enabling planar wave front propagation of the TEM mode where efficiency values of over 90% are achieved. Measurements of a fabricated prototype are also reported at 15 GHz to demonstrate the design procedure and validate structure operation. When compared with similar co-axial and metallic waveguide launchers, our proposed SIW structure represents a compact, integrated, and unique design solution which may be useful to feed planar parallel-plate slot arrays and end-fire antennas. In addition, our novel and simple approach for PPW excitation can also be applied to other parallel-plate-based guides, low-cost transitions, and compact dividing/combining circuits for a new antenna and non-radiating LW feed systems at microwave and millimeter-wave frequencies.

Design of wide band-pass substrate integrated waveguide (SIW) filters based on stepped impedances

A full-wave design technique of n-order Chebyshev stepped impedance band-pass filters in substrate integrated waveguide (SIW) is presented for the first time. The structure of the filter is based on including elliptic patterns etched on the SIW top surface to synthesize Chebyshev transfer functions. The band-pass response is obtained from the high-pass characteristic of the SIW line together with the behavior of the elliptic patterns, which implement the impedance inverters needed to control an upper cut-off frequency in the response of the filter. The synthesis technique is applied to the design of a sixth-order Chebyshev stepped impedance band-pass SIW filter. It is shown that the use of elliptic patterns instead of circular patterns can increase the spurious free range of the filter. In addition, when exponential microstrip-to-SIW transitions are integrated into the design process, a reduction in size and improvement in return loss are achieved, as compared to a base-line filter (sixth-order Chebyshev stepped impedance band-pass filter) designed with transitions separately. Electromagnetic (EM) simulation and measurements results have shown the effectiveness of the proposed design technique to carry out high-performance band-pass filters in SIW technology.

Characterization of a 4 × 4 substrate integrated waveguide Butler matrix at 60 GHz for two‐dimensional beam steering

A 4x4 substrate integrated waveguide (SIW) Butler matrix for two-dimensional (2-D) beam steering operating at 60 GHz is developed and experimentally evaluated in this article. The SIW beamforming network is a Butler matrix that is implemented with new designs of its constituent components in order to achieve a compact design. Namely, an SIW phase shifter that uses periodic rectangular slots is introduced for the first time at 60 GHz to replace the more area-consuming meandered SIW. The phase shifter prototype, fabricated and measured as a proof of concept, demonstrates achieving an additional 20.3° of phase shift with using only 3 apertures without increasing the length or meandering the SIW line. The hybrid coupler and crossover sections of the SIW Butler matrix are also optimized to reduce the overall area of Butler matrix by 53.9%. The SIW Butler matrix prototype is fabricated and measured demonstrating achieving the differential output phase values needed to switch the beam of a 2-D array in four quadrants while keeping the insertion loss magnitude imbalance of below 1.47 dB from simulations and 3.34 dB from measurements.

Tunable ferrite-based metamaterial structure and its application to a leaky-wave antenna

In this paper, a new magnetically tunable substrate integrated waveguide (SIW) with composite right/left-handed (CRLH) response is presented. The structure consists of an array of interdigital slots on the upper wall of a SIW line with normally magnetized ferrite substrate. The electromagnetic properties of this structure are studied and the dispersion diagram is considered. The simulated results show that the proposed structure has a separate right- and left-handed leakage frequency region which can be simply controlled by varying the applied ferrite magnetic bias field. As an application, this leakage frequency band is exploited to build a new leaky-wave antenna (LWA) which its radiation pattern can be independently scanned by varying the frequency or the magnetic bias field. As another advantage, there is not any mechanical switch or electrical tuning chip in the proposed leaky-wave antenna.

Electromagnetic band gap waveguide and bends substrate integrated waveguide

AbstractA planar waveguide and a rounded bend is proposed, designed, and implemented through a hybrid structure of substrate integrated waveguide (SIW) and electromagnetic bandgap (EBG) material. In order to design the EBG waveguide, a square lattice of air holes situated between two metal plates is used. The SIW line and bend are inserted on EBG waveguide to enhance performance. These devices were fabricated and measured. The experimental results show a homogeneous agreement with the simulation. The combination EBG‐SIW covers almost the whole EBG bandwidth of 6 GHz (17%) around 35 GHz. The proposed hybrid integration technique presents a competitive candidate for the development of millimeter‐wave circuits and systems.

Gap Waveguide PMC Packaging for Two-Layer PEC Surfaces

This paper shows the investigation of gap waveguide (GW) packaging for an irregular perfect electric conductor (PEC) composed of two layers of metal surfaces. The stopband for a GW with two-layer PEC surfaces is carefully studied, considering the top-layer PEC width, pin size, pin height, columns of pins, as well as dielectric substrate thickness and permittivity. A strategy of the GW packaging for such an irregular PEC surface is presented. In addition to the unit cell-based stopband study, such GW packaging is also demonstrated for a substrate-integrated waveguide (SIW)–microstrip line structure, which is typical of the circuit with two-layer PEC surfaces. A Chebychev bandpass filter built on the SIW and microstrip line is finally designed and fabricated to provide experimental verifications. In particular, a dedicated defect of the side air gap existing in the SIW-based circuits using the GW PMC packaging is found, and an effective remedy is presented.

Novel Four-Way Multilayer SIW Power Divider With Slot Coupling Structure

A novel four-way multilayer substrate integrated waveguide (SIW) power divider with slot coupling structure is proposed in this letter. Two rectangular slots located in the right and left arms of SIW T-junction are employed to achieve efficient transition with two microstrip lines. Good impedance matching and signal transmission between SIW and microstrip lines are achieved. Two isolation resistors are used to improve the isolation between output ports. The even- and odd-mode analysis method is used in the proposed circuit. A prototype of the presented power divider is designed, fabricated, and measured. The measured results show a reasonable agreement with the simulated ones.

Wideband Excitation Technology of <formula formulatype="inline"><tex Notation="TeX">${\rm TE}_{20}$</tex></formula> Mode Substrate Integrated Waveguide (SIW) and Its Applications

The higher order mode substrate integrated waveguide (SIW) has advantages in the applications, which are: 1) simplifying the structure with reduced fabrication cost and 2) enhancing the stability of performance by relaxed fabrication tolerance. In this paper, two wideband ${\rm TE}_{20}$ mode excitation structures are presented and investigated for the SIW. A slot along the mid line in the longitudinal direction of the SIW is employed to convert the electromagnetic field pattern between slotline and the ${\rm TE}_{20}$ mode SIW. The second structure is based on the slot aperture coupling and can realize wideband direct transition between the ${\rm TE}_{20}$ mode SIW and microstrip line. Both transitions have a simple and compact structure, as well as broadband characteristics. The wideband transition performance is demonstrated in this paper. As application examples of the transitions, two broadband substrate integrated baluns are presented and fabricated based on the ${\rm TE}_{20}$ mode excitation structures and ${\rm TE}_{20}$ mode characteristics. The 180 $^{\circ}$ out-of-phase and equal magnitude of the balun outputs in a wide frequency range can be achieved inherently. The balun based on the slotline excitation has a fractional bandwidth of 50.2%, from 7.3 to 12.2 GHz, with measured return loss, amplitude imbalance, and phase imbalance better than 10 and 0.45 dB and 3.8 $^{\circ}$ . The balun based on the aperture coupling excitation shows a fractional bandwidth of 50.3%, from 7 to 11.7 GHz, with measured return loss, insertion loss, amplitude imbalance, and phase imbalance better than 10, 1, and 0.27 dB and 2.4 $^{\circ}$ , respectively. Both baluns not only show good performance, but also demonstrate the existence of the ${\rm TE}_{20}$ mode in the SIW.

Low-profile, high-gain and broadband array of corner cube reflector antenna based on substrate integrated waveguide

A novel array of a corner-cube reflector antenna targeting the 10.7–13.5 GHz frequency band is presented. The proposed antenna has the advantages of low-profile, broadband and high gain with linear polarisation. The substrate integrated waveguide (SIW) technology is employed effectively for feeding the antenna. The proposed antenna is formed of four corner-cube reflectors which are fed by SIW lines. The concept is validated by simulations and measurements.

A Millimeter-Wave E-Plane Band-pass Filter using Multilayer Low Temperature Co-Fired Ceramic (LTCC) Technology

This paper presents a substrate integrated waveguide (SIW)-based millimeter-wave E-plane band-pass filter (BPF) with multilayer Low Temperature Co-fired Ceramic (LTCC) technology. The vertical metal walls of SIW and metal fins of the evanescent waveguides are realized by closely spacing metallic via-holes. A three-order Chebyshev E-plane BPF is developed and verified by full-wave simulation. The proposed filter is fabricated using LTCC technology, and a tapered line is designed as the transition between the SIW and microstrip line. Good agreement between simulated and measured results is observed.