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

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

A novel design method of low profile cavity backed planar slot antenna has been described in this paper. The whole antenna including backed cavity and feeding element is completely constructed at a single substrate by using substrate integrated waveguide technique and grounded coplanar waveguide. An example with 1.7% bandwidth has been presented, which has 5.4 dBi gain, 16.1 dB front-to-back ratio and -19 dB maximum cross polarized radiation level with its total thickness less than lambda0/50. The proposed antenna keeps good radiation performance of conventional cavity backed antenna and has advantages of conventional planar antenna including low profile, light weight, easy fabrication with low cost and convenient integration with planar circuit.

Planar Slot Antenna Backed by Substrate Integrated Waveguide Cavity

The propagation properties of the half-mode substrate integrated waveguide (HMSIW) are studied theoretically and experimentally in this paper. Two equivalent models of the HMSIW are introduced. With the first model, equations are derived to approximate the field distribution inside and outside the HMSIW. Using the second model, an approximate closed-form expression is deduced for calculating the equivalent width of an HMSIW that takes into account the effect of the fringing fields. The obtained design formulas are validated by simulations and experiments. Furthermore, the attenuation characteristics of the HMSIW are studied using the multiline method in the frequency range of 20-60 GHz. A numerical investigation is carried out to distinguish between the contributions of the conductive, dielectric, and radiation losses. As a validation, the measured attenuation constant of a fabricated HMSIW prototype is presented and compared with that of a microstrip (MS) line and a substrate integrated waveguide (SIW). The SIW is designed with the same cutoff frequency and fabricated on the same substrate as the HMSIW. The experimental results show that the HMSIW can be less lossy than the MS line and the SIW at frequencies above 40 GHz.

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Characterization of the Propagation Properties of the Half-Mode Substrate Integrated Waveguide

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

By etching longitudinal slots on the top metallic surface of the substrate integrated waveguide (SIW), an integrated slot-array antenna is proposed in this letter. The whole antenna and feeding system are fabricated on a single substrate, which takes the advantage of small size, low profile, and low cost, etc. The design process and experimental results of a four-by-four SIW slot array antenna at X-band are presented.

Simulation and experiment on SIW slot array antennas

In this paper, a novel realization of the Integral Equation in combination with the fast Fourier transform for the CFIE is established by Fitting both the Green's function and its Gradient onto the nodes of a uniform Cartesian grid. The new method has been compared with several existing popular FFT-based methods, including the AIM, the IE-FFT, and the p-FFT. The accuracy of the proposed method is significantly higher than other FFT-based methods, and the method is not sensitive to both the grid spacing and the expansion order. The outstanding merit of the proposed method is that the fitting procedure is independent of the basis functions. Therefore, when the higher order basis functions would be adopted in the method of moments, only one fitting procedure for the Green's function and its gradient on a basis function support is needed to meet all of basis functions defined on this support. Some numerical examples are provided in this paper to demonstrate the accuracy and efficiency of the proposed method.

A Highly Accurate FGG-FG-FFT for the Combined Field Integral Equation

An omnidirectional slot array antenna based on substrate integrated waveguide (SIW) technology is developed in this letter, which inherits the merits of small size, low profile, and low cost etc. form SIW. Omnidirectional SIW slot array antennas are realized by etching longitudinal slots on both sides of the top and bottom metallic planes of a SIW. The experiment results for 6 GHz wireless access applications show that 3% bandwidth (VSWRles1.5) and a very good omnidirectional radiation pattern are achieved.

Design of an omnidirectional line array with SIW longitudinal slot antenna

Directional couplers are widely used in microwave or millimeter wave power splitters or antenna feeding circuits for generating desired power division ratio at a specified bandwidth. The bandwidth and size are the two key parameters in the specifications of couplers. A compact coupler could save space and reduce the metal loss, and also the wide band properties will bring a generalized usage of couplers. Rectangular waveguide directional couplers have been seriously investigated for a long time [1]-[3] and numbers of circuits or structures have been obtained to achieve high performance flat coupling properties. However, manufacturing such a coupler requires high accurate machining and thus results in high cost. Substrate Integrated Waveguide (SIW) is a dielectric filled waveguide structure that has the similar propagating modes as rectangular waveguide, but manufacturing of such a waveguide structure requires only the normal Print Circuit Board (PCB) process and results in the merit of low cost and mass production ability. SIW directional couplers also have been successfully designed and fabricated [4]-[5]. But most of the couplers are designed by H-plane wall of two adjacent SIW which is guided wavelength depended and requires large PCB area. Single layer SIW compact size crossed waveguide directional coupler also been mentioned [6], the bandwidth of the coupler is limited. This paper introduced a double layer wide band compact directional coupler with two SIWs crossed over each other. Large range of coupling coefficient and wide band characteristics are achieved. The coupling is realized by the cross slots between upper layer SIW and lower layer SIW. Structures and parameters, simulated and experiment results are presented. Such a coupler could be a good candidate in antenna feeding structure or power divider applications.

A double layer crossed over Substrate Integrated Waveguide wide band directional coupler

A microstrip asymmetric folded dipole antenna on chip is proposed in this paper. The construction of balun feed line is adopted to provide wideband. A new design procedure based on the odd-even mode method to calculate the input impedance of an asymmetric strip folded dipole antenna is presented. The folded dipole antenna has the advantage of small size, low profile, low cost, and so forth. The measured results show that a miniaturized antenna has the bandwidth of more than 14.2% (VSWR 2); gain of the antenna is 5.7 dB at 35 GHz.

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Guang Hua

Papers

Simulation and experiment on SIW slot array antennas

A Highly Accurate FGG-FG-FFT for the Combined Field Integral Equation

Design of an omnidirectional line array with SIW longitudinal slot antenna

A double layer crossed over Substrate Integrated Waveguide wide band directional coupler

Microstrip Folded Dipole Antenna for 35 GHz MMW Communication