Substrate Integrated Waveguide Filtering Horn

Antenna Facilitated by Embedded Via Hole Arrays

Muhammad Talha Aimen Hafeez Muhammad Faizan Asif
School of Electrical Engineering and School of Electrical Engineering and School of Electrical Engineering and
Computer Science (SEECS) NUST Computer Science (SEECS) NUST Computer Science (SEECS) NUST
Islamabad, Pakistan Islamabad, Pakistan Islamabad, Pakistan
mtalha13.msee23seecs@seecs.edu.pk ahafeez.msee23seecs@seecs.edu.pk masif.msee23seecs@seecs.edu.pk

Abstract—The integrated substrate waveguide filtering an- crostrip antennas due to their unique blend of advantages,
tenna facilitates the insertion of integrated holes in the arrays. including compact size, low loss, ease of integration, and
This project delves into the design and implementation of a fil- compatibility with planar fabrication processes. The concept
tering horn antenna using substrate integrated waveguide (SIW)
technology with integrated holes in the arrays. This innovative of SIW was introduced in the early 2000s as a means of
approach harnesses the advantages of SIW technology, such as integrating waveguide-like structures into planar substrates,
compactness and high selectivity, to enhance the performance thereby combining the desirable characteristics of both waveg-
of the antenna system. SIW technology has been extensively uide and microstrip technologies. Since then, SIW antennas
researched and applied in antenna design due to its benefits have attracted significant attention from researchers and en-
in terms of compactness, low profile, and high efficiency. The
integration of SIW with horn antennas has demonstrated promis- gineers across various disciplines, ranging from microwave
ing results in various frequency bands, including milli-wave engineering to telecommunications and beyond. [4] At its core,
and terahertz ranges. Using SIW technology, the filtering horn
antenna can achieve both broadband and filtering capabilities,
which are crucial for modern communication systems.
Index Terms—SIW, Filtering Horn Antenna, Embedded Via
Hole Arrays, Bandwidth, Gain, Frequency Selectivity.

I. I NTRODUCTION
Traditional rectangular waveguide integration schemes in-
volve bulky and complex transitions, often comprising mul-
tiple separate pieces that necessitate careful assembly [1].
Furthermore, achieving precise machining at millimeter wave
frequencies poses significant challenges for mass production.
Furthermore, these integration schemes often require tun-
ing mechanisms to optimize performance, adding additional
complexity and cost to the process As shown in Figure 1.
Moreover, the need to cut the planar substrate into specific
shapes further complicates the integration process, making it
both challenging and costly. [2] These constraints not only Fig. 1. A potential SIW-based platform in which SIW antennas, couplers,
cavities, filters are all combined with active and DSP circuits on the same
hinder the seamless integration of rectangular waveguides with substrate or master board
planar circuits but also limit their practicality and scalability,
particularly for mass production and commercial deployment. the substrate integrated waveguide comprises a guided trans-
In light of these challenges, researchers have been exploring mission structure formed within a dielectric substrate, typically
alternative approaches to address the integration issues asso- using printed circuit board (PCB) or other planar fabrication
ciated with rectangular waveguides and planar circuits. These techniques. By confining electromagnetic waves within the
efforts have led to the development of innovative techniques dielectric substrate, SIW antennas offer the advantages of re-
and design methodologies aimed at simplifying integration, duced radiation losses, improved power handling capabilities,
reducing complexity, and enhancing manufacturability, thereby and enhanced electromagnetic interference (EMI) shielding
enabling the realization of compact and cost-effective solu- compared to traditional microstrip antennas [5]. One of the
tions for high-frequency applications [3]. Substrate Integrated key features of SIW antennas is their ability to support a wide
Waveguide (SIW) antennas have emerged as a promising range of operating frequencies, from microwave to millimeter-
technology to meet these demands. SIW antennas offer a wave bands, while maintaining excellent performance char-
compelling alternative to conventional waveguide and mi- acteristics. This versatility makes SIW antennas well-suited
for various applications, including wireless communication broad operational bandwidth. These strips serve as impedance
systems, radar systems, satellite communication, and more [6] transformers, facilitating a seamless transition between the
[7]. horn aperture and the surrounding free space. To effectively
excite the SIW horn antenna, a tapered transition structure
II. D ESIGN P ROCEDURE
is employed to achieve an exceptionally broad bandwidth
We redesigned the SIW Horn Antenna as per the parameters spanning from GCPW to SIW. This transition structure incor-
defined in the paper. Figure 2 and Figure 3 illustrates the porates a tapered coupling slot, meticulously etched to function
geometry of the proposed filtering horn antenna with the as an impedance transformer. As illustrated in Figure 4, the
overall size of 58.7 × 34 × 1.524 mm3 ,, and fabricated on GCPW transition mechanism enables the realization of a wide
Rogers 4350B substrate with (ϵr = 3.66, tan δ = 0.004). operational bandwidth ranging from 16.2 GHz to 16.9 GHz
The detailed dimensional parameters of the proposed filtering [10].
antenna are listed in Table I.

Fig. 2. Geometry of the proposed SIW filtering horn

Fig. 4. Reflection Coefficient of SIW Horn Antenna

B. Filtering Response by Embedding Metallized via hole Ar-

rays
By employing SIW technology, the filtering horn antenna
Fig. 3. Geometry of the proposed SIW filtering horn. (a) 3D view. (b) Top
can achieve both broadband and filtering capabilities, Fur-
view thermore, the incorporation of embedded via hole arrays in
the design further boosts the performance of the antenna
system. This approach enables improved signal manipulation
TABLE I and filtering capabilities within the horn antenna structure.
D IMENSIONAL PARAMETERS OF THE P ROPOSED A NTENNA
The amalgamation of SIW technology with via hole arrays
Variable Value [mm] Variable Value [mm] provides a compact and efficient solution for implementing
Dvia 1.2 D 32.4 advanced filtering functionalities in horn antennas. This paper
L1 9.0 L2 34.3
W 30.5 LS 3.8
introduces a novel and effective approach to designing high-
X 13.0 X12 5.3 performance filtering horn antennas. By capitalizing on the
X23 6 X34 6.9 benefits of SIW technology and embedded via hole arrays, the
Y1 2.7 Y2 6
Y3 3 S 0.4
proposed antenna system offers enhanced selectivity and signal
Svp 1.6 a 8 manipulation capabilities, making it a valuable contribution to
the field of antenna engineering [11]. In order to realize filter-
ing response without any increase of the antenna dimension,
A. SIW H-Plane Horn Antenna four rows of inductive metallized via holes are embedded into
the filtering horn antenna under is derived from a fundamen- the flare region of the horn antenna, forming three coupled
tal SIW H-plane optimal horn antenna. In order to enhance the resonant cavities to achieve filtering function. The Q factor of
impedance bandwidth of the SIW horn antenna, wo metallic cavities and the coupling coefficient between resonators within
strips (3.8 mm long, 30.5 mm wide) were added. [8] [9] A the flare structure of the horn exhibit disparities compared
tapered transition structure was used for excitation, achieving a to those within the waveguide. Initially, the numbers and
 as shown in Figure 5.
C. Gain Improvement by Optimizing EM Field Distribution
on the Radiating Aperture
The spacing between the via holes affect the electromagnetic
field distribution across the horn aperture. The electric field
distribution on radiating aperture gets more uniform if the
spacing between via holes of fourth row increases [14]. We
increase the distance between via holes from 1.5 mm to
3 mm. As a result, we achieve an increase in gain of 0.15 dB
for the filtering horn antenna and observe improved roll-off
characteristics [15] [16].

Fig. 5. Reflection Coefficient of SIW Filtering Horn Antenna

Fig. 7. Radiation Pattern of Filtering Horn Antenna (f=16.6GHz)

Fig. 6. Gain Plot vs Frequecy Plot

Fig. 8. Radiation Pattern of Filtering Horn Antenna (f=16.7GHz)

positions of embedded metallized via holes can be approxi-

mated by referencing design criteria for waveguide resonant
cavities. Subsequently, slight adjustments are made to these
parameters to achieve the desired filtering performance [12]
[13]. To improve the frequency selectivity performance, the
4th row of the metallized via holes is introduced to realize
a third-order filtering horn. The 4th row of metallized via
holes, with X34 = 6.9 mm, introduce a new resonant cavity
coupled with earlier formed two resonant cavities, a third-order
filtering response could be realized theoretically. Limited by
the longitudinal length of the horn, too many metallized via
holes in the 4th row will block the radiating aperture of the Fig. 9. Radiation Pattern of Filtering Horn Antenna (f=16.8GHz)
horn and bring large shunt inductance, which will decrease
the aperture efficiency and worsen the impedance matching
between the horn aperture and the free space, resulting in III. R ESULTS AND D ISCUSSION
decrease of the gain and deterioration of |S11 |. So the number The simulated |S11 | of the proposed antenna is illustrated
of metallized via holes in the 4th row is carefully optimized to in Fig. 4. It can be seen that a third-order filtering response
3 to obtain better impedance matching and filtering response with |S11 | < −10 dB and good frequency selectivity is
 [8] G. Q. Luo, W. Hong, H. J. Tang, J. X. Chen, X. X. Yin, Z. Q. Kuai, and
K. Wu, “Filtenna consisting of horn antenna and substrate integrated
waveguide cavity FSS,” IEEE Trans. Antennas Propag., vol. 55, no. 1,
pp. 92–98, Jan. 2007.
[9] M. Barbuto, F. Trotta, F. Bilotti, and A. Toscano, “Horn antennas with
integrated notch filters,” IEEE Trans. Antennas Propag., vol. 63, no. 2,
pp. 781–785, Feb. 2015.
[10] M. Hamedani, H. Oraizi, A. Amini, D. Zarifi, and A. U. Zaman, “Planar
H-plane horn antenna based on groove gap waveguide technology,” IEEE
Antennas Wireless Propag. Lett., vol. 19, no. 2, pp. 302–306, Feb. 2020.
[11] O. A. Nova, J. C. Bohorquez, N. M. Pena, G. E. Bridges, L. Shafai, and
C. Shafai, “Filter-antenna module using substrate integrated waveguide
cavities,” IEEE Antennas Wireless Propag. Lett., vol. 10, pp. 59–62,
2011.
Fig. 10. Radiation Pattern of Filtering Horn Antenna (f=16.9GHz) [12] C. A. Balanis, Antenna Theory: Analysis and Design. Hoboken, NJ,
USA: John Wiley & Sons, 2005, pp. 765–766.
[13] M. Esquius-Morote, B. Fuchs, J. Zürcher, and J. R. Mosig, “A printed
transition for matching improvement of SIW horn antennas,” IEEE
obtained from 16.6 GHz to 17 GHz. Moreover, it also shows Trans. Antennas Propag., vol. 61, no. 4, pp. 1923–1930, Apr. 2013.
a significant gain of more than 4 dBi over the band, as shown [14] R. Kazemi, A. E. Fathy, S. Yang, and R. A. Sadeghzadeh, “Development
of an ultrawide band GCPW to SIW transition,” in Proc. IEEE Radio
in Figure 6. Its 2D radiation pattern indicates that it is more Wireless Symp., Santa Clara, CA, USA, 2012, pp. 171–174.
directive in the azimuth plane and less directive in the elevation [15] D. Deslandes and K. Wu, “Single-substrate integration technique of
plane. planar circuits and waveguide filters,” IEEE Trans. Microw. Theory
Tech., vol. 51, no. 2, pp. 593–596, Feb. 2003.
[16] B. S. Kim, J. W. Lee, K. S. Kim, and M. S. Song, “PCB substrate
IV. C ONCLUSION integrated waveguide-filter using via fences at millimeter-wave,” in Proc.
IEEE Int. Microw. Symp. Dig., 2004, vol. 2, pp. 1097–1100.
This paper presents the design, analysis, and measurement
of a Substrate Integrated Waveguide (SIW) filtering horn an-
tenna featuring embedded metallized via hole arrays, achieving
robust frequency selectivity. In contrast to existing SIW filter-
ing horn antennas, which typically comprise directly cascaded
filters and horn antennas, the proposed design fulfills the
criteria of integration, miniaturization, and multi-functionality
for RF front-end applications. By incorporating two metal
strips adjacent to the radiating aperture on both sides of the
substrate, the bandwidth of the simple SIW H-plane horn is
significantly expanded. Additionally, four rows of metallized
via holes are strategically embedded into the flare region of
the horn antenna, forming three coupled resonant cavities. This
configuration enables the realization of filtering functionality
without any increase in antenna dimensions.

R EFERENCES
[1] W. Lin and H. Wong, “Polarization reconfigurable wheel-shaped antenna
with conical-beam radiation pattern,” IEEE Trans. Antennas Propag.,
vol. 63, no. 2, pp. 491–499, Feb. 2015.
[2] W. Lin, R. W. Ziolkowski, and J. Huang, “Electrically small, low profile,
highly efficient, Huygens dipole rectennas for wirelessly powering
Internet-of-Things (IoT) devices,” IEEE Trans. Antennas Propag., vol.
67, no. 6, pp. 3670–3679, Jun. 2019.
[3] W. Wu, Y. Yin, S. Zuo, Z. Zhang, and J. Xie, “A new compact filter-
antenna for modern wireless communication systems,” IEEE Antennas
Wireless Propag. Lett., vol. 10, pp. 1131–1134, 2011.
[4] C. Lin and S. Chung, “A compact filtering microstrip antenna with
quasi-elliptic broadside antenna gain response,” IEEE Antennas Wireless
Propag. Lett., vol. 10, pp. 381–384, 2011.
[5] Y. Lee, J. Tarng, and S. Chung, “A filtering diplexing antenna for dual-
band operation with similar radiation patterns and low cross-polarization
levels,” IEEE Antennas Wireless Propag. Lett., vol. 16, pp. 58–61, 2017.
[6] X. Y. Zhang, W. Duan, and Y. Pan, “High-gain filtering patch antenna
without extra circuit,” IEEE Trans. Antennas Propag., vol. 63, no. 12,
pp. 5883–5888, Dec. 2015.
[7] B. Froppier, Y. Mahe, E. M. Cruz, and S. Toutain, “Integration of a
filtering function in an electromagnetic horn,” in Proc. 33rd Eur. Microw.
Conf., Oct. 2003, vol. 3, pp. 939–942.