Philip Barr, Afroz Zaman, and Félix Miranda

Glenn Research Center, Cleveland, Ohio

A Compact, Broadband Antenna for Planetary

Surface-to-Surface Wireless Communications

NASA/TM—2006-213885

November 2006
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A Compact, Broadband Antenna for Planetary

Surface-to-Surface Wireless Communications

NASA/TM—2006-213885

November 2006

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Philip Barr, Afroz Zaman, and Félix Miranda

Glenn Research Center, Cleveland, Ohio
Acknowledgments

The authors would like to acknowledge Kevin Lambert of Analex Corporation and

Richard Lee of the NASA Glenn Research Center for their contributions to this project.

Available from

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National Technical Information Service

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Trade names and trademarks are used in this report for identification

only. Their usage does not constitute an official endorsement,

either expressed or implied, by the National Aeronautics and

Space Administration.

Level of Review: This material has been technically reviewed by technical management.
NASA/TM—2006-213885 1

A Compact, Broadband Antenna for Planetary 

Surface-to-Surface Wireless Communications 

Philip Barr, Afroz Zaman, and Félix Miranda 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

The Compact Microstrip Monopole Antenna (CMMA) is a novel antenna design that combines a 

microstrip patch antenna with a three-dimensional structure to attain a highly directive, broadband, 

compact antenna. A Tri-Lobed Patch (TLP) was designed to minimize the patch’s area while reducing the 

antenna’s operating frequency. A Grounding Wall (GW) connects the patch to the ground plane and a 

Vertical Enclosure Wall (VEW) extends up away from portions of the patch’s perimeter. This VEW 

supplies the antenna with a higher directivity in the radial direction as well as reduces the operating 

frequency. The CMMA was designed to operate at 2.23 GHz, but experimental results have shown this 

antenna resonates at 2.05 GHz which is on the order of approximately λo/11.6 with respect to the 

antenna’s largest dimension, with a directivity and bandwidth of 6.0 dBi, and 130 MHz (6.3 percent), 

respectively. This miniature, radially emitting antenna makes the CMMA attractive for planetary-based 

surface-to-surface communications. 

1. Introduction 

NASA’s vision for space exploration calls for extending the human presence throughout the solar 

system through both human and robotic missions (ref. 1). This vision will be realized with a return to the 

moon by 2020 in preparation for future human missions to Mars and beyond. As NASA begins exploring 

these destinations a flexible, reliable, and cost-effective wireless communications network will be needed. 

This wireless communications network will be required to support various types of communications 

including voice, data, imaging, and video to and from an assortment of mobile and non-mobile nodes. To 

achieve these goals a concerted research effort into miniature antenna technologies is ongoing at the 

NASA Glenn Research Center (GRC). The Compact Microstrip Monopole Antenna (CMMA) presented 

in this paper is one of the outcomes of this ongoing effort. 

The CMMA radiates like a miniature monopole antenna with a height of less than λo/11.6, where λo is 

the wavelength of the electromagnetic signal in free space. This small size was achieved by attaching a 

Grounding Wall (GW) along a small section of the perimeter of a Tri-Lobed Patch (TLP) (ref. 2). Efforts 

by other groups (e.g., the Dime Antenna (refs. 3 and 4)) have shown that the operating frequency of these 

grounded patches was determined by the length of the ungrounded perimeter, plus the length of the GW. 

The TLP achieves a larger perimeter while maintaining a smaller area to reduce the operating frequency 

while minimizing size. Although this approach significantly reduces the antenna’s operating frequency, 

the directivity is greatly diminished. To address this problem a Vertical Enclosure Wall (VEW) was 

attached to portions of the TLP’s perimeter to increase the antenna’s directivity and further reduce the 

antenna’s operating frequency, in our case by as much as 500 MHz. 

2. Compact Microstrip Monopole Antenna (CMMA) Design and Fabrication 

The CMMA was designed and simulated using Zealand’s IE3D electromagnetic simulator to radiate 

at 2.23 GHz, a frequency within the band being considered for Lunar and Martian surface-to-surface 

communications (refs. 5 and 6). The TLP was designed on a 1.57 mm thick substrate with a relative 

dielectric constant of εr = 2.2 over a ground plane. A series of six connected circles located at the corners 
NASA/TM—2006-213885 2

of an equilateral hexagon defines the layout of this patch. The diameter of each circle is 4.60 mm which is 

also equal to one side of the equilateral hexagon. Figure 1 illustrates the design technique used for the 

TLP. In figure 2 the locations of the GW and the VEW are depicted. A GW approximately 1.20 mm wide 

was attached from the perimeter of the patch to the ground plane spanning the 1.57 mm thickness of the 

substrate. A VEW of 11.0 mm in height and 31.2 mm in length was attached to the perimeter of the TLP 

and distributed evenly around the 2 lobes which are directly opposite the lobe containing the GW. 
NASA/TM—2006-213885 3

The prototype shown in figure 3 was fabricated at NASA GRC on 1.57 mm Duroid® 5880 (Rogers 

Corporation, Chandler, AZ) with a relative dielectric constant of εr = 2.2. The copper surface of the 

Duroid® 5880 was etched to pattern the TLP used in the CMMA. The GW and VEW were fabricated 

using copper tape. The adhesive from the copper tape was removed using a ketone-based solvent. The 

50 μm thick walls were shaped appropriately and attached to the patch using Ablebond, a conductive 

epoxy. A coaxial probe was inserted through the Duroid® 5880 to feed an RF signal from below the 

antenna through the substrate to the TLP. This probe was attached 0.75 mm from the GW. The outer 

conductor of the coaxial probe was removed near the ground plane to prevent electrical shorting. 

3. Experimental Testing and Results 

The CMMA was measured using an HP 8510C network analyzer which showed an optimal S11

performance at 2.05 GHz. The measured difference in this operating frequency from simulation could be 

a result of fabrication constraints. The relative dielectric constant of the epoxy, which is nominally 4, may 

have been a factor contributing to the lowering of the operating frequency. Simulations that included this 

epoxy layer have shown a reduction in the operating frequency to what was observed in experiments. The 

10 dB bandwidth of the fabricated antenna was approximately 130 MHz (6.3 percent) which was larger 

than the simulated one of 50 MHz. Figure 4 compares the measured return loss of the CMMA with 

simulation. The broadening of the resonance is a result of the non-optimal matching and coupling losses 

between the RF probe feed and the antenna. 
NASA/TM—2006-213885 4
NASA/TM—2006-213885 5

Experimental measurements of the CMMA’s radiation patterns were performed in the Cylindrical 

Near Field Antenna Range at NASA GRC (ref. 7). The measured radiation patterns for the E-plane and 

H-plane are shown in figure 5. The radial radiation characteristic of the CMMA indicates that the 

dominant radiation mechanism of the antenna is the surface current flowing on the VEW. This current is 

fed at the base of the wall and is distributed in a manner determined by the TLP. Note that this 

distribution is a function of frequency and hence it is the TLP that controls the frequency behavior of the 

antenna. The current flows vertically and must terminate at the top edge of the wall resulting in the 

radiated field. These currents can be viewed in the current distribution plot shown in figure 6. The 

directivity of the CMMA prototype was calculated from the radiation pattern to be approximately 6.0 dBi 

which is comparable to the simulated directivity of 5.0 dBi and the quarter-wave monopole of 5.16 dBi 

(ref. 8). 
NASA/TM—2006-213885 6

4. Conclusion 

With the CMMA’s unique combination of a VEW and a microstrip patch, this miniature antenna 

retains its high directivity and large bandwidth properties as compared to typical miniature antennas 

which trade these properties to achieve their small sizes. Measured results have shown that the CMMA is 

capable of operating at less than λo/11.6 with no trade off in its directivity. The measured bandwidth and 

directivity for this antenna were 130 MHz and 6.0 dBi, respectively. The CMMA has the potential for 

many applications where monopole antennas are typically used. Many mobile components in NASA’s 

future missions such as sensors, rovers, robots, etc., will require radially directed antennas since the 
NASA/TM—2006-213885 7

antenna’s orientation and position cannot be predicted. The CMMA’s small size makes it more suitable 

for integration than other larger monopole antennas. Future work for this antenna includes an 

investigation into a linear array of the CMMA elements to produce a highly directive radially radiating 

antenna. 

References 

1. National Aeronautics and Space Administration, The new age of exploration. NASA’s direction for 

2005 and beyond, July 15, 2005, <http://www.nasa.gov/pdf/107490main_FY06_Direction.pdf> 

2. R. Waterhouse, Small microstrip patch antenna, IEE Electronics Letters, vol. 31, (1995), 604–605. 

3. B.A. Cetiner, L. Jofre, F. Flaviis, N. Alexopoulos, and G. P. Li, A miniature broadband antenna for 

portable communications terminals, IEEE Antennas and Propagation Society International 

Symposium, vol. 4, (2001), 108–111. 

4. B.A. Cetiner, L. Jofre, F. Flaviis, Reconfigurable miniature multielement antenna for wireless 

networking, IEEE Radio and Wireless Conference, (2001), 203–206. 

5. D.L. Brandel, Spectrum recommendations for lunar relay and lunar proximity links, Presentation to 

NASA Architecture Sub-Group for Spectrum on June 24, 2004. 

6. Space Frequency Coordination Group, Frequency assignment guidelines for communications in the 

mars region, July 15, 2005, <http://www.sfcgonline.org/handbook/rec/rec22-1r1.doc> 

7. K. Lambert, G. Anzic, R. Zakrajsek, and A. Zaman, Overview of antenna measurement facilities at 

the NASA Glenn Research Center, Proceedings of the Antenna Measurement Techniques Association 

24th Annual Meeting & Symposium, (2002), 549-554. Also found as NASA/TM—2002-211883, 

October 2002. 

8. W.L. Stutzman, G.A. Thiele, Antenna theory and design, Edition 2, John Wiley & Sons, Inc., (1998), 

68. 
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13

A Compact, Broadband Antenna for Planetary Surface-to-Surface Wireless

Communications

Philip Barr, Afroz Zaman, and Félix Miranda

Broadband antenna; Wireless communications; Compact microstrip monopole antenna;

S-band; Surface-to-surface communications; Miniature antenna

Unclassified -Unlimited

Subject Categories: 88 and 91

Responsible person, Philip Barr, organization code RCA, 216–433–6718.

The Compact Microstrip Monopole Antenna (CMMA) is a novel antenna design that combines a microstrip patch

antenna with a three-dimensional structure to attain a highly directive, broadband, compact antenna. A Tri-Lobed

Patch (TLP) was designed to minimize the patch's area while reducing the antenna's operating frequency. A Grounding

Wall (GW) connects the patch to the ground plane and a Vertical Enclosure Wall (VEW) extends up away from

portions of the patch's perimeter. This VEW supplies the antenna with a higher directivity in the radial direction as

well as reduces the operating frequency. The CMMA was designed to operate at 2.23 GHz, but experimental results

have shown this antenna resonates at 2.05 GHz which is on the order of approximately λo/11.6 with respect to the

antenna's largest dimension, with a directivity and bandwidth of 6.0 dBi, and 130 MHz (6.3 percent), respectively.

This miniature, radially emitting antenna makes the CMMA attractive for planetary-based surface-to-surface communications.