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 new generation of high-frequency integrated circuits is presented, which is called substrate integrated circuits (SICs). Current state-of-the-art of circuit design and implementation platforms based on this new concept are reviewed and discussed in detail. Different possibilities and numerous advantages of the SICs are shown for microwave, millimeter-wave and optoelectronics applications. Practical examples are illustrated with theoretical and experimental results for substrate integrated waveguide (SIW), substrate integrated slab waveguide (SISW) and substrate integrated nonradiating dielectric (SINRD) guide circuits. Future research and development trends are also discussed with reference to low-cost innovative design of millimeter-wave and optoelectronic integrated circuits.

The substrate integrated circuits - a new concept for high-frequency electronics and optoelectronics

Phononic crystals are the acoustic wave analogue of photonic crystals. Here a periodic array of scattering inclusions located in a homogeneous host material forbids certain ranges of acoustic frequencies from existence within the crystal, thus creating what are known as acoustic bandgaps. The majority of previously reported phononic crystal devices have been constructed by hand, assembling scattering inclusions in a viscoelastic medium, predominantly air, water or epoxy, resulting in large structures limited to frequencies below 1 MHz. Recently, phononic crystals and devices have been scaled to VHF (30–300 MHz) frequencies and beyond by utilizing microfabrication and micromachining technologies. This paper reviews recent developments in the area of micro-phononic crystals including design techniques, material considerations, microfabrication processes, characterization methods and reported device structures. Micro-phononic crystal devices realized in low-loss solid materials are emphasized along with their potential application in radio frequency communications and acoustic imaging for medical ultrasound and nondestructive testing. The reported advances in batch micro-phononic crystal fabrication and simplified testing promise not only the deployment of phononic crystals in a number of commercial applications but also greater experimentation on a wide variety of phononic crystal structures.

https://iopscience.iop.org/article/10.1088/0957-0233/20/1/012002/pdf

Microfabricated phononic crystal devices and applications

Because of the low dimensional power of its force scaling law, surface tension is appropriate for carrying out reshaping and assembly in the microstructure size domain. This paper reviews work on surface tension powered self-assembly of microstructures. The existing theoretical approaches for rotational assembly are unified. The demonstrated fabrication processes are compared. Mechanisms for accurately determining the assembled shape are discussed, and the limits on accuracy and structural distortion are considered. Applications in optics, electronics and mechanics are described. More complex operations (including the combination of self-assembly and self-organization) are also reviewed.

Surface tension-powered self-assembly of microstructures - the state-of-the-art

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.

/pdf/characterization-of-the-propagation-properties-of-the-half-jv82wmu7p5.pdf

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

A W-band substrate integrated waveguide slot antenna has been designed and tested. The antenna has been realised using a reduced height waveguide in photoimageable thick film technology. Experimental and simulated return loss and radiation pattern measurements are presented.

W-band substrate integrated waveguide slot antenna

We present a method for the fabrication of vertical inductors for radio-frequency and microwave applications. This process uses five levels of lithography and electroplating, with no substrate removal, high temperatures or serial process steps. Rotation of the inductors perpendicular to the substrate is achieved by surface tension driven self-assembly, giving separation from the substrate and therefore increasing substantially the Q and self-resonant frequencies. Meander and spiral air-bridged inductors of up to 5.5 nH are demonstrated. The Q of 2 nH inductors shows an increase from 4 to 20 after having undergone the self-assembly process. Mechanical sensitivity is evaluated through finite element modelling, and the maximum displacements indicated are below 10 nm for 1 g of loading. Mechanical resonance frequencies are found within the 6-15 kHz range. (C) 2002 Elsevier Science B.V. All rights reserved.

Fabrication, RF Characteristics and Mechanical Stability of Self-Assembled 3D Microwave Inductors

A folded waveguide structure is presented farmed from microwave laminates as a space saving alternative of the rectangular waveguide. It is shown that the folded waveguide results in a width reduction of e r -1/2 /2 over standard air filled rectangular waveguide making integrated waveguide viable at low microwave frequencies. Via hole technology is used to manufacture this design, at low cost, using computer controlled drilling machines. The guide is integrated to planar circuitry using tapered stripline.

http://ieeexplore.ieee.org/iel5/9672/30681/01418992.pdf

Compact folded waveguides

A novel dielectric-filled metal-pipe rectangular waveguide has been fabricated using photoimageable thick-film materials. The waveguides incorporate a new transition from CPW-to-TFMS-to-MPRWG. Standard on-wafer measurement techniques, waveguide STD calibration standards, demonstrated low attenuation across the 60 to 90 GHz frequency range.

Photoimageable thick-film millimetre-wave metal-pipe rectangular waveguides

We present microwave inductors of 1.5 to 2.5 nH fabricated out-of-plane by a self-assembly process. The consequent de-coupling from the substrate allows improved Q (from 4 to 20) and frequency of maximum Q (from 0.5 GHz to 3 GHz) on low resistivity silicon substrates.

Paul R. Young

Papers

W-band substrate integrated waveguide slot antenna

Fabrication, RF Characteristics and Mechanical Stability of Self-Assembled 3D Microwave Inductors

Compact folded waveguides

Photoimageable thick-film millimetre-wave metal-pipe rectangular waveguides

MEMS high Q microwave inductors using solder surface tension self-assembly