Design of a Deployable Helix Antenna at L-Band for a 1-Unit CubeSat: From Theoretical Analysis to Flight Model Results

Abstract

The 3Cat-4 mission aims at demonstrating the capabilities of a CubeSat to perform Earth Observation (EO) by integrating a combined GNSS-R and Microwave Radiometer payload into a 1-Unit CubeSat. One of the greatest challenges is the design of an antenna that respects the 1-Unit CubeSat envelope while operating at the different frequency bands: Global Positioning System (GPS) L1 and Galileo E1 band (1575 MHz), GPS L2 band (1227 MHz), and the microwave radiometry band (1400-1427 MHz). Moreover, it requires between 8 and 12 dB of directivity depending on the band whilst providing at least 10 dB of front-to-back lobe ratio in L1 and L2 GPS bands. After a trade-off analysis on the type of antenna that could be used, a helix antenna was found to be the most suitable option to comply with the requirements, since it can be stowed during launch and deployed once in orbit. This article presents the antenna design from a radiation performance point of view starting with a theoretical analysis, then presenting the numerical simulations, the measurements in an Engineering Model (EM), and finally the final design and performance of the Flight Model (FM).

Keywords: CubeSat; Earth Observation; L-Band; antenna; deployable; helix; nanosatellite.

Figure 6

Analysis ground plane models. (a) Square model with 0.5 $\mathsf{\lambda }$ GP. (b) Square model with 1.5 $\mathsf{\lambda }$ GP. (c) Model with conical GP. (d) Model with cylindrical GP.

Figure 1

Overall geometry of helical antennas. (a) Geometry of helical antenna. (b) Unrolled turn of helical antenna.

Figure 2

Helix antenna radiation modes. (a) Normal mode. (b) Axial mode. (c) Conical mode.

Figure 3

Model with infinite GP.

Figure 4

Model with CubeSat GP.

Figure 5

Ground plane models and dimension parameters. (a) Square GP. (b) Cylindrical GP. (c) Conical GP.

Figure 7

Results for the ground planes shapes analysis. (a) Directivity results for ground plane shapes analyzed. (b) Front-to-back lobe ratio results for ground plane shapes analyzed.

Figure 8

Directivity results for a sweep in parameters for the cylindrical GP. (a) Directivity for different cylindrical GP diameters and optimum height ($h=0.25\mathsf{\lambda }$). (b) Directivity for different cylindrical GP heights and optimum diameter ($d_{gp}=\mathsf{\lambda }$).

Figure 9

Model with cubic cup ground plane.

Figure 10

Model with cubic cup ground plane and CubeSat structure.

Figure 11

Prototype assembled in CubeSat structure.

Figure 12

Extruded view of the NADS.

Figure 13

S11 parameters results for the NADS FM.

Figure 14

NADS FM in the UPC Antenna Lab Anechoic Chamber.

Figure 15

Radiation patterns measured in an Anechoic Chamber from the NADS Flight Model. (a) Radiation at 1227.6 MHz. (b) Radiation at 1400 MHz. (c) Radiation at 1427 MHz. (d) Radiation at 1575 MHz.

Figure 16

Axial ratio measured in an Anechoic Chamber from the NADS Flight Model. (a) Axial ratio at 1227.6 MHz. (b) Axial ratio at 1400 MHz. (c) Axial ratio at 1427 MHz. (d) Axial ratio at 1575 MHz.