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

The theoretical basis and the practical implementation of an objective approach to voltage reflection coefficient (VRC) interpolation in the development of radio frequency coaxial impedance standards are presented. Variants of the scheme apply to three impedances commonly used to calibrate vector reflectometers and vector network analyzers. The scheme permits impedance standards to be characterized in the intermediate frequency (IF) range (where, broadly speaking, IF refers to the frequency range 10 kHz to 100 MHz) in terms of their VRC values and associated measurement uncertainties. The scheme allows the use of commercially available devices (rather than specially constructed calculable devices) as impedance standards with VRC values traceable to national measurement standards. Measurement results are presented which illustrate the capabilities of the scheme.

An interpolation scheme for precision intermediate frequency reflection coefficient measurement

The design and performance of 180 GHz substrate integrated waveguide filters is presented. It is shown that photoimageable thick film technology can achieve the precise dimensional control needed for design at G-band. TRL calibration standards are fabricated in the substrate integrated waveguide medium itself and excellent results are obtained for the 140–200 GHz frequency range. 0.1 and 0.01dB ripple filters are designed and fabricated, with 8 and 6.2% relative bandwidths. The measured results show excellent agreement with electromagnetic simulations.

Design and Characterization of 180 GHz Filters in Photoimageable Thick-Film Technology

Flexible front- and back-end RF/analogue system antennas were recently emerged. However, little flexible antenna system design is available so far, in planar hybrid technology with surface mounted components. This paper describes the design feasibility of flexible switching 1 × 2 antenna array system. It acts as a switching antenna implemented in hexapole configuration. The system is comprised of a key element RF switch terminated by two identical patch antennas associated to half-wave elementary transmission lines (TLs). A detailed theory illustrating the global S-parameter model determination in function of the given RF-switch return and insertion losses is established. In difference to the conventional microwave circuit theory, the proposed equivalent S-parameter model is originally built with the non-standard optimized antenna load. Thus, the synthesis method of the terminal antenna input impedance and the output access line characteristic impedance is formulated in function of the specified return and optimal transmission losses. The design method and theoretical approach feasibility is verified with the demonstrator of flexible switching 1 × 2 antenna array printed on Kapton substrate. The circuit prototype is implemented in hybrid planar technology integrating patch antenna operating at about 6 GHz and a packaged GaAs RF switch associated to the RF/DC signal decoupling accessory mounted surface components. Simulations of the designed circuit transmission and isolation losses from 5.5 GHz to 7 GHz were carried out by using the commercial RF switch S-parameter touchstone model provided by the manufacturer. The simulated and measured return losses are compared and discussed. Then, the measured radiation patterns confirm the proposed switched antenna concept feasibility.

Design and synthesis of flexible switching 1 × 2 antenna array on Kapton substrate

This paper describes the use of photoimageable thick-film technology for the fabrication of rectangular waveguides. Thick-film technology is attractive for volume manufacture and recent materials developments, such as photoimageable dielectric and conductor pastes, have led to improved edge definition and smaller feature sizes, so that thick-film circuits can equal the performance of thin-film processing. A dielectric-filled rectangular waveguide fabricated using photoimageable thick-film materials is presented. The waveguide incorporates a new transition from RFOW probe to rectangular waveguide. Results show low attenuation across the 60-90 GHz frequency range.

Paul R. Young

Papers

An interpolation scheme for precision intermediate frequency reflection coefficient measurement

Design and Characterization of 180 GHz Filters in Photoimageable Thick-Film Technology

Design and synthesis of flexible switching 1 × 2 antenna array on Kapton substrate

Fabrication of dielectric-filled rectangular waveguide using thick-film processing

Investigating the random error distribution of vector network analyser measurements.