978-1-5386-7333-1/18/$31.00 ©2018 IEEE

Design of a C-band High Gain Microstrip Antenna Array for CubeSat Standard

Vladimir A. Juarez-Ortiz and Robert Perea-Tamayo

Space Agency of Peru, Lima, Peru, vjuarez@conida.gob.peand rperea@conida.gob.pe

Abstract — This paper presents a low cost C-band microstrip

antenna array with high gain, composed of 2 x 2 patches of 14.38mm by 18.42mm each, and compatible with CubeSat standard at 5.8 GHz center frequency. The feeding method is corporate feed network matched to 50 Ω line by different impedance lines. The patch´s Mutual Coupling is decreased by rotating 45o each patch, obtaining a return loss of -32.02 dB, a Voltage Standing Wave Ratio of 0.4 dB and a maximum gain of 13.34 dB. Simulations with a 3U CubeSat structure with deployed VHF and UHF antennas shows little deviations. The final array size is of 74 mm x 74 mm.

Index Terms — Antenna Array, Corporate Feed Network, CubeSat, Microstrip, Mutual Coupling.

I. INTRODUCTION

The CubeSat standard is based on cubes of 10 cm by side that

reduces the complexity of designing a satellite, therefor it has

become popular for students at universities all over the world,

motivating the innovation in aerospace science [1]. Commonly

CubeSat communications are realized in VHF and UHF bands,

which have little Bandwidth and large dimensions compared to

the satellite. An alternative is found with microstrip antennas

[2], which can work at higher frequencies, thus reducing the

dimensions using simpler and precise manufacturing

techniques.

Currently the CubeSat have used scientific applications in

radio bands in 2450 MHz [3] and 5800 MHz [4], which are

available for scientific applications [5]. In these frequencies, a

Microstrip Antenna (MSA) array fits the CubeSat standard and

allows increasing the gain by design.

In order to comply with space standards, the antenna board

should minimize the contamination of the satellite and the

surrounding systems during launch phase. Thus the design is

proposed in RT/duroid®6002 substrate, that is adequate for its

low outgassing and dielectric losses [6]

II. ANTENNA ARRAY DESIGN

The chosen working frequency is 5.8 GHz (C-band) and the

substrate is based on RT/duroid®6002 laminates, whose

physical characteristics are as detailed in Table I

The MSA array is based on four rectangular patches, that

requires to reduce the mutual coupling (MC) between them. A

common recommendation is to keep the separation between

patches bigger than 0.5λ0 [7], where λ0 is the resonance

wavelength.

The dimensions of each patch are calculated using equations

(1), (2), (3) and (4). Where W is the width of the patch, L is the

length of the patch, c is the speed of light in vacuum, fres is the

resonance frequency, εr is the dielectric permittivity, h and t the

thickness of substrate and copper respectively.

(1)

(2)

(3)

(4)

For each patch the resulting width (W) is 14.38mm and length

(L) is 18.42mm. The patches’ integration and matching are

made by Corporate Feed Network method, using Wilkinson

Power Dividers, T-junction and quarter wave transformers with

microstrip lines with impedances of 50 Ω, 70 Ω and 100 Ω [8].

Under the size of 74 mm x 74 mm, the MC can’t be avoided

and some optimization is required [9]. A rotation of 45o was

applied to the MSA patches, creating a separation of 0.31λ0 in

the E-plane and of 0.43λ0 in the H-plane. The optimization was

TABLE I

CHARACTERISTICS OF RT/DUROID® 6002 SUBSTRATE

Substrate Characteristics Value Unit

Dielectric Constant 2.94 -

Dissipation Factor (tan α) 0.0012 -

Thickness

Substrate 1.524 mm

Copper 0.035 mm

Ground 0.035 mm

Dimensions 74 x 74 mm

completed by a recursive variation of the patches dimensions.

The final MSA array is shown in Fig. 1.

Fig. 1. Upper view of the microstrip antenna array with dimension.

III. SIMULATIONS & RESULTS

The designed MSA array was simulated using HFSSTM tools

in a free space environment. At center frequency the resulting

S11 parameter or Return Loss (RL) is -32.02 dB, the Bandwidth

is around 180 MHz and the Voltage Standing Wave Ratio

(VSWR) is 0.48 dB as shown in Fig. 2.

Fig. 2. MSA array simulated Return Loss and VSWR.

The realized gain in theta plane is 13.34 dB at the center

frequency, as shown in Fig. 3, which is higher compared to a

single C-band patch antenna. The improvements were obtained

by reducing the side-lobes during the optimization process.

Fig. 3. Realized Gain for the MSA array.

Under the Ludwig-3 (L3) definition [10] this antenna has

dual polarization as it is shown in the Fig. 4, where the

polarization ratio is approximately 1 for L3X and L3Y planes.

It is confirmed comparing the distribution of radiated power,

which is 48.3% for L3X and 51.7% L3Y. This result finds this

MSA array suitable also for meteorological radars [11].

Fig. 4. Radiated power magnitude (main) and polarization ratio (inset) for the L3X and L3Y.

IV. ANTENNA PLACEMENT OVER THE CUBESAT

ENVIRONMENT WITH DEPLOYED VHF AND UHF ANTENNAS

The antenna is designed to be used on a CubeSat, where the

structures and other components of the satellite would influence

its electromagnetic characteristics. Simulations were performed

in two possible positions as shown in Fig. 5, considering a

typical 3U CubeSat with VHF and UHF antennas deployed.

The MSA array is located on one side of the CubeSat

considering the Poly-Picosatellite Orbital Deployer (P-POD)

[12] requirements and perpendicular to the UHF antenna.

Fig. 5. MSA array Radiation Pattern after deployment of VHF and UHF antennas, the insets show the different MSA array positions.

The resulting maximum RL is -40 dB, but center frequency

shifted to 5.81 GHz as shown in Fig. 6. For the top position the

RL is -26.96 dB with 180 MHz (3.1%) of Bandwidth, and for

bottom position the RL was improved to -29.51 dB but with 160

MHz (2.8%) of Bandwidth.

Fig. 6. Simulated Return Loss of the MSA array for two antenna positions over a 3U CubeSat.

The realized gain of the antenna located over the structure

was of 13.25 dB for the top position and 13.13 dB for bottom

position, meaning a reduction of 0.12 dB, as shown in Fig. 7.

Fig. 7. Simulated realized gain of the MSA array for two antenna positions over a 3U CubeSat.

The Half Power Beam Width (HPBW) is shown in Fig. 8,

with 32.8º for top position and 29.7º for bottom position. Also,

the First-Null Beam Width (FNBW) is found between -46º and

+46º in both cases.

Fig. 8. Simulated HPBW of the MSA array for two antenna positions over a 3U CubeSat.

V. CONCLUSION

The microstrip antenna array designed in C-band can fit

under the dimensions of a CubeSat, and with a central

frequency of 5.8 GHz showed to get a RL of -32.03 dB, a

realized gain of 13.34 dB and of Bandwidth of 180 MHz, which

could provide improved communication links for CubeSat

applications. And considering its dual polarization it can be

applied for meteorological radar applications too.

The analysis of the antenna located over the body of a

CubeSat within the environment of deployed VHF and UHF

antennas proves to have some deviation, like a shift of the

center frequency to 5.81 GHz and increase of the RL and the

VSWR, which does not affect the performance of the antenna

in a meaningful way.

ACKNOWLEDGEMENT

The microstrip antenna array was supported by the

Microsatellite laboratory from Beihang University in China,

and the Space Agency of Peru (CONIDA) allowing the further

research of the initial designs. Also, special collaboration was

received from HFSSTM software support, providing

recommendations while performing the simulations.

REFERENCES

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