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SUBSTRATE INTEGRATED WAVEGUIDESSubstrate integrated waveguides belong to the family of substrate integrated circuits.

Substrate Integrated Circuits (SICs):

Substrate Integrated Waveguide (SIW)

Substrate Integrated Non-Radiative Dielectric Waveguide (SINRDW)

Substrate Integrated Image Guide (SIIG)

Plated-through (metallized) via holes

Air holes

Air holes

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In the upper microwave and the lower millimeter-wave range, substrate-integrated waveguide circuits form a reasonable compromise between microstrip and waveguide technologies.

Microstrip is light weight and compact but has high ohmic losses.

Waveguide has low ohmic losses but is bulky and difficult to integrate.

Substrate-integrated waveguide uses the top and bottom metallizations of the substrate and metallized via holes to create an artificial waveguide.

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Fundamental Mode Propagation in

Regular Waveguide Substrate Integrated Waveguide

SIW is a compromise between microstrip and all-metal waveguide

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1. DESIGN OF VIA DIAMETER AND VIA SEPARATION

Leakage loss in Np/rad as a function of via diameter and via separation normalized to the cutoff wavelength.

Deslandes, Wu, IEEE Trans. MTT, June 2006

SIW circuits with d/p between 0.4 and 0.8 have been published. In order to limit leakage losses to those of dielectric and conductors, d/p>0.5 is recommended.

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2. EQUIVALENT WAVEGUIDE WIDTH

The equivalent waveguide width determines the SIW’s cutoff frequency (cutoff wavelength) for applying rectangular waveguide design procedures.

equc r

ca2f

Design an SIW circuit for a given frequency (waveguide band). Note that only TEm0 modes can propagate in SIW.

c is the speed of light

Different models to calculate the equivalent waveguide width:

2

equda a

0.95p

Model (1) (Cassivi et al, IEEE MWCL, Sep. 2002):

Model (2) (Yan et al, IEEE MWCL, Sep. 2004):

1 2 3equ 1 2

3 1

x x xpa a x xd x x

1

2

3

x 1.0198 0.3465 a p 1.0684

x 0.1183 1.2729 a p 1.2010

x 1.0082 0.9163 a p 0.2152

Model (3) (Xu, Wu, IEEE Trans. MTT, Jan. 2005):

2 2equa a 1.08d p 0.1d a

Model (4) (Che et al, IET MAP, Feb. 2008):

equ

equ

2a p pa arcctg ln4a 2d

Model (5) (Salehi, Mehrshahi, IEEE MWCL, Jan. 2011):

equ 32 2

4

aa2a d d 4a d1

p a d a d5p

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d/p=0.4: Models (1), (2), (3), (5) d/p=0.6: Model (2) Models (1), (3), (5)

d/p=0.8: Models (1), (3) Models (2), (5)

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3. SQUARE-TO-CIRCULAR VIA CONVERSION

When the via holes are produced by a laser, they can have any shape. Square via holes can be fabricated closer together than circular ones. Square via holes are also easier to model, e.g., in MMT, FEM, etc

W-band SIW-to-waveguide transition with square via holes (Dousset, Wu, Claude, El. Lett., Nov. 2010)

The side length of the square via is the arithmetic mean of the inscribed and circumscribed squares of the circular via:

112 2 2

o ia a da

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Examples:

Two-resonator K-band SIW post filter Four-resonator K-Band SIW dual-band filter

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Examples (cont’d):

K-band SIW 2-way power divider

K-band SIW 3-way power divider

24-slot 3 dB W-band SIW aperture coupler realized by cascading two 8.34 dB couplers

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4. DESIGN OF SIW COMPONENTS- For given frequency range, select substrate material and determine via-hole diameter and

separation.

- Design the component in all-dielectric-filled rectangular waveguide (H-plane technology)

using the equivalent waveguide width.

- Set certain parameters (iris thickness, coupling aperture thickness, etc) to via-hole

dimensions so that they can easily be replaced by via holes later.

- Optimize the rectangular waveguide component for given specifications.

- Replace waveguide walls by via holes using the equivalent waveguide-to-SIW width and use

all-dielectric waveguide ports.

- Use square via holes if that is easier to handle in modelling procedures (MMT,

WaveWizard, FEM, etc).

- Fine-optimize the SIW component.

- Verify with a different field solver.

- Include microstrip-to-SIW tapers for measurements.

- Design calibration standards.

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5. PRACTICAL EXAMPLES OF SIW TECHNOLOGY

Power Dividers (Germain, Deslandes, Wu, CCECE 2003)

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Couplers (Cassivi, Deslandes, Wu, APMC 2002)

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Filters (Chen, Wu, Drolet, IEEE Trans. MTT, Mar 2009)

Fourth-order filter with three oversized SIW cavities

Fourth-order filter with two oversized SIW cavities

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Filters cont’d (Chen, Wu, Li, IEEE Trans. MTT, Dec 2007)

K-band SIW dual-band filter K-band SIW triple-band filter

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Di/Triplexers

Ka-band SIW diplexer (Tang Hong Chen Luo Wu, IEEE Trans. MTT, Apr 2007)

2 GHz SIW triiplexer (Hou, Hong, Tian, Liu, Tang, APMC, Dec 2009)

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Leakage waves

Leaky Wave Antenna

Slot Array Antenna

Antipodal Linearly Tapered Slot Antenna (ALTSA)

Antenna Applications

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Antenna coupled diplexer (D. Deslandes, PhD Diss, Ecole Polytechnique, Montreal, 2005)

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10 GHz ALTSA Array (Hao, Hong, Chen,Chen, Wu, IEEE MTT-S IMS, June 2005)

Top metallization

Bottom metallization

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37.5 GHz Multibeam Antenna with Parabolic Reflector (Cheng, Hong, Wu, IEEE Trans. AP, Jan 2008)

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Radiation pattern when excited at Port 1

Radiation pattern when excited at Port 3

94 GHz Monopulse Array (Cheng, Hong, Wu, IEEE Trans. AP, Jan 2012)