Status report for the antenna subsystem

Introduction

We have decided to use a dipole antenna for the Uplink RX (145 MHz) and the AIS RX (162 MHz) and a ¼-wavelength monopole antenna for the downlink UHF TX (435 MHz). The antennas will be made of measuring tape. These antennas have to be deployed when the satellite is in orbit. This can be done whit a fishing line and a nichrome wire, similar methods have been used by other cubesat projects.

The L-band TX frequency is not determined, but we want to combine a broadband patch antenna for this frequency and the GPS RX frequency. We can place two patches on the cubesat, one on the side of the gravitation bom and the other on the opposite side of the bom. The patch witch faces the earth will be used for L-band TX and the other will be used for the GPS RX.

Fig 1: The dipole and monopole antennas

Antenna deployment

When the satellite is deployed from the launching tube the dipole- and monopole antennas will be folded up in a track around the cubesat. After the satellite is deployed we have to wait a certain amount of time before we deploy the antennas. If we deploy them to early they could come in contact with the launching tube or other cubesats.

The antennas can be deployed by using a fishing line to tie down the antennas in the track. To break the wire we can use a nichrome wire which we coil around a piece of the fishing line. The Fishing line is broken by applying a voltage across the nichrome wire.

Power supply . The voltage level needed to break the fishing line should be somewhere between 2 and 3.5 V. This is not yet tested, but will be done as soon as we get the nichrome wire from the supplier. A similar project [1] has shown that the smaller we make the diameter of the nichrome wire coil and the more voltage we apply the faster the fishing line breaks. By applying 3.2 V they broke the wire after 1.8 seconds.

Suggested hardware components

Quantity Type Description Supplier Unit price Delivery time

1 Nichromewire 20 FT WireTronic Inc $ 45 +shipping

?

2 Measuring tape

6mm width, 300mm lengt

Via Jernia NOK 80,- 21.10.02

1 Fishing line A sportsstore ?

Other specifications

Antennas made from measuring tape: - Estimated weight: ~ 5 g - Estimated length dipole: 2 x 400 mm - Estimated length monopole: 160 mm- Estimated antenna width: 6 mm

Technical Challenges

Antennas take up space. The main challenge is not to obstruct the other groups to much.The antenna track, that has to fit the antennas that are 6 mm wide, will take up space so that there will be less area for the solar cells. This might be in conflict with the needs of the power group.

The patch antennas will also take up space. A solution here might be replacing metallic patches by solar cells in planar antennas. This concept is described in [2] but has to be studied further.

Referanses

[1] T. Hiroshige: CubeSat Antenna Team, Spring 2002

[2] Vaccaro, Mosig and Maagt: Making planar antennas out of solar cells, Electronic Letters online No:200220675