Passive Feed Methods for Meshed Antennas

Jason R. Saberin* (1), Cynthia Furse (1), Tursunjan Yasin(2) , and Reyhan Baktur(2) (1)Department of Electrical and Computer Engineering

University of Utah, Salt Lake City, UT, 84103

(2) Department of Electrical and Computer Engineering Utah State University, Logan, UT, 84322

E-mail: jasonsaberin@gmail.com, reyhan.baktur@usu.edu

Introduction

Meshed patch antennas have been shown to be a simple and cost effective solution for applications where antennas are required to be transparent to light. One good example is to integrate highly transparent antennas with solar cells on small satellites to save surface real estate [1]. These meshed antennas can be conveniently constructed from electroformed metal mesh or be printed with conductive ink [1].

Previous studies have concentrated on rectangular meshed patches [1]. However, circular and triangular shapes can improve polarization and bandwidth characteristics not addressed in rectangular patches. One of the challenges with these shapes is effective feed design and an efficient fabrication method. To solve these two problems, we have examined several types of antenna feeds using inkjet printing with conductive ink on plastic substrate or copper tape on glass. Furthermore, it was found that printing methods are effective in fabricating meshed antennas and that passive feed methods can be easily and efficiently implemented for single patch or antenna array designs.

Passive Feed System

In order to achieve circular polarization and wider bandwidths desired for satellite communication, the circular patch and triangular shapes where found to be good antenna candidates, but these alternative antenna shapes may require different feeds than for rectangular patches [1]. A circular meshed patch antenna was designed with a line feed of 50 Ω to passively feed the entire antenna structure, seen in Figure 1. In this case both antenna and feed can be simultaneously printed with an inkjet printer using conductive ink. For the triangular or bowtie meshed patch, a 50 Ω line feed can be placed on the side of the patch also passively feeding the entire geometry. Furthermore, several triangular antennas can be placed by the coupled line, Figure 2, to form an antenna array and potentially improve overall gain and widen the overall bandwidth.

Figure 1 - Geometry of

Figure 2 - Triang

Building

Both Ansoft’s HFSS ® aantennas and their respecinput impedance. The Optimally the gap distanlosses and improving ante The circular patch anteconductive ink. The antethis demonstrates a gooantennas and feed on a ththe antenna on a layer permittivity εr=2.6, and copper ground plate. Thtransparency of 60% whemeasured radiation patter

Couplin

a meshed circular patch antenna with side coupled lin

ular meshed patch antenna array with a side feed line

g and Testing of Coupled Fed Antennas

and CST Microwave Studio ® were used to simctive feeds. In both cases, the feed gap can detelarger the coupling gap the higher the im

nce should be less than 0.1λ, thus limiting theenna efficiency [3].

enna was simulated and built using a prinenna was measured to have return losses belowod match. The fabrication details include prihin polyethylene Terephthalate substrate, later aof Plexiglass with substrate height, h= 2 mmloss tangent of 0.0057. The Plexiglass is bac

he meshed patch antenna is able to achieve aen compared to a solid copper circular patch antern is normalized to its maximum value, seen in F

50 Ohm feed

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The triangular antenna array feed was built using copper tape and copper foil on a glass substrate with εr=6 with a substrate height of 3mm. The triangular antenna was found to be relatively wideband, 100 MHz bandwidth, seen in Figure 4. Moreover, the triangular antenna possessed a transparency of 70% when compared to a solid rectangular patch. These findings show promising results in the study of passive feeds for meshed antennas. Further research is necessary to determine optimal feed distance, wider bandwidth and circular polarization of arrays or individual antennas.

Figure 3 - Measured E-plane radiation pattern

Figure 4 - Return loss of triangular array

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Conclusion

Circular and triangular meshed patch antennas are important in applications where antennas are required to be transparent to light, have a wide bandwidth and provide circular polarization. These meshed antennas can be effectively fed with a coupled line feed and can be fabricated using an inkjet printing method or with a more rudimentary method such as with copper tape. Although the study experimented with the antenna of transparency of 60% an 70%, the fabrication and feed design presented can be easily applied to antennas with transparency higher than 90%, making the meshed antennas favored design for integration with solar cells, windows, and LED displays.

References

[1] T. W. Turpin, and R. Baktur, “Integrated Solar Cell Meshed Patch Antennas”, to appear on IEEE Antennas and Wireless Propagation Letters, 8: 693-696, 2009.

[2] L. Zhu and K. Wu, “Line-to-ring Coupling Circuit Model and its Parametric Effects for Optimized Design of Microstrip Ring Circuits and Antennas”, 1997 IEEE MTT-S Digest Volume: 1, page(s): 289-292.

[3] J. Liu, H. C. Wu, M. S. Chiang, H. Tsou, “T-coupled circular microstrip antenna with H-shaped aperture for bandwidth and radiation-gain improvements”, Microwave and Optical Technology Letters, Volume 37 Issue 6, Pages 414 - 417