Substrate-integrated waveguide (SIW) technology represents an emerging and very promising candidate for the development of circuits and components operating in the microwave and millimetre-wave region. SIW structures are generally fabricated by using two rows of conducting cylinders or slots embedded in a dielectric substrate that connects two parallel metal plates, and permit the implementation of classical rectangular waveguide components in planar form, along with printed circuitry, active devices and antennas. This study aims to provide an overview of the recent advances in the modelling, design and technological implementation of SIW structures and components.

Review of substrate-integrated waveguide circuits and antennas

A dielectric loaded substrate integrated waveguide (SIW) H-plane sectoral horn antenna has been proposed in this paper. The horn and the loaded dielectric are integrated by using the same single substrate resulting in easy fabrication and low cost. Two antennas with rectangular and elliptical shaped loaded dielectrics were designed and fabricated. These antennas have high gain and narrow beamwidths both in the E-plane and in the H-plane. The results from the simulation and those from the measurement are in good agreement. To demonstrate applications of the array, the small aperture elliptical dielectric loaded antenna has been used to form an array to obtain higher gain and to form a one-dimensional monopulse antenna array.

Dielectric Loaded Substrate Integrated Waveguide (SIW) ${H}$ -Plane Horn Antennas

This paper presents the modeling of lossy substrate integrated waveguide interconnects and components by using the boundary integral-resonant mode expansion method. The extension of the numerical technique to account for conductor, dielectric and radiation losses is discussed. Moreover, a systematic investigation of the different contributions of loss and their dependence on some geometrical parameters is performed in the case of interconnects and components, aiming at minimizing the losses. The physical explanation of the different effects is also provided. Finally, the validity of the equivalent waveguide concept is extended to the case of lossy interconnects and components.

Modeling of Conductor, Dielectric, and Radiation Losses in Substrate Integrated Waveguide by the Boundary Integral-Resonant Mode Expansion Method

This paper presents a substrate integrated waveguide (SIW) multibeam slot array operating at $\sim 30$ GHz for future 5G mobile terminal applications. The multibeam forming network is realized with a Butler matrix that is composed of hybrid couplers, crossovers, and phase shifters (135° and 0°). The crossovers are formed with two cascaded hybrid couplers. In the design of 135° and 0° phase shifters, the phase compensation technique is employed. The slot array is a $2 \times 4$ type, in which each column has two slot elements that are longitudinally staggered with respect to one another (in half-wavelength). In addition, mutual couplings reduction techniques applied in the proposed slot array are also discussed. The SIW technique is adopted in case for the related components, as it can be highly integrated in mmWave circuits at low fabrication cost and has low profile characteristics. The overall dimension of the SIW multibeam slot array (including the Butler matrix feeding network) is $72 \times 27.4 \times 0.508$ mm3, and the total area of the slot array is only $10.1\times 20.4$ mm2. The measured 10 dB bandwidth was 28–32 GHz, and the measured gains at 30 GHz for each port were 10.8, 12.1, 12, and 11 dBi. The proposed slot array also possesses wide angle coverage of $\sim 40^{\circ }$ with good steerable radiation.

SIW Multibeam Array for 5G Mobile Devices

A substrate integrated waveguide (SIW) H-plane sectoral horn antenna, with significantly improved bandwidth, is presented. A tapered ridge, consisting of a simple arrangement of vias on the side flared wall within the multilayer substrate, is introduced to enlarge the operational bandwidth. A simple feed configuration is suggested to provide the propagating wave for the antenna structure. The proposed antenna is simulated by two well-known full-wave packages, Ansoft HFSS and CST Microwave Studio, based on segregate numerical methods. Close agreement between simulation results is reached. The designed antenna shows good radiation characteristics and low VSWR, lower than 2.5, for the whole frequency range of 18-40 GHz.

Wideband H-Plane Horn Antenna Based on Ridge Substrate Integrated Waveguide (RSIW)

Rectangular waveguide (RW) with sidewalls of vertical conducting cylinders (i.e. SIW, substrate-integrated waveguide) becomes popular with the advent of low-temperature co-fired ceramic structure; its analysis is usually numerical, or modal, leading to empirical design formulas. However, its analytical equivalence to the common RW of the solidwall is identified; in other words, analytical design formulas of the SIW and the equivalent RW of solid sidewalls are the same. The equivalence is established on comparing the surface impedances along the side walls, of the SIW and of an RW through analytical continuation. The equivalence formulas, propagation and cut off frequency show very good agreement with the results from both numerical simulations and measurements of hardware experiments, and over wide frequencies. The good agreements are easily understood on the basis of the conformal maps and the variational principle.

Y.L. Chow

Papers

Analytical equivalence between substrate-integrated waveguide and rectangular waveguide