Electrically Small Microstrip Antennas Targeting Miniaturized Satellites: the CubeSat Paradigm

Abstract

Mini-satellite (100-500 kg) 2. Micro-satellite (10-100 kg) 3. Nano-satellite (1-10 kg) 4. Pico-satellite (0.1-1 kg) 5. Femto-satellite (0.01-0.1 kg) CubeSats belong to the genre of pico-satellites; their maximum weight lies on the borderline between pico-and nano-satellites. The main reason for miniaturizing satellites is to reduce the cost of deployment: heavier satellites require larger rockets of greater cost to finance; smaller and lighter satellites require smaller and cheaper launch vehicles, and are often suitable for launch in multiples. They can also be launched "piggyback", using the excess capacity of larger launch vehicles (Wikipedia, 2010b). But small satellites are not short of technical challenges; they usually require innovative propulsion, attitude control, communication and computation systems. For instance, micro-/nano-satellites have to use electric propulsion, compressed gas, vaporizable liquids, such as butane or carbon dioxide, or other innovative propulsion systems that are simple, cheap and scalable. Micro-satellites can use radio-communication systems in the VHF, UHF, L-, S-, C-and X-band. On-board communication systems must be much smaller, and thus more up-to-date than what is used 12 in conventional satellites, due to space constraints. Furthermore, miniature satellites usually lack the power supply and size required for conventional bulky radio transponders. Various compact innovative communication solutions have been proposed for small satellites, such as optical (laser) transceivers, antenna arrays and satellite-to-satellite data relay. Electronics need to be rigorously tested and modified to be "space hardened", that is, resistant to the outer space environment (vacuum, microgravity, thermal extremes and radiation exposure) (Wikipedia, 2010b). The CubeSat programme was developed through the joint efforts of research laboratories from California Polytechnic State University (Cal Poly) and Stanford University, beginning in 1999. The concept was introduced to the scientific community as an opportunity for all universities to enter the field of space science and exploration. A large group of universities, along with certain companies and organizations, participate actively in the CubeSat programme; it is estimated that 40 to 50 universities were developing CubeSats in 2004. Featuring both small size and weight, a CubeSat can be built and launched for an estimated total of $65,000-80,000 (per fiscal year 2004 values). The standard 10 × 10 × 10 cm 3 basic CubeSat is often called a "1U" CubeSat, meaning one unit. CubeSats are roughly scalable in 1U increments and larger. The four basic sizes are 0.5U, 1U, 2U and 3U. The number corresponds to the length of the CubeSat in decimetres; width and depth are always 10 cm, or 1 dm. Orbiters such as a "2U" CubeSat (20 × 10 × 10 cm 3) and a "3U" CubeSat (30 × 10 × 10 cm 3) have been both built and launched. Since CubeSats are all 10 × 10 cm 2 (regardless of length) they can all be launched and deployed using a common deployment system. CubeSats ar...

A Microstrip Second-Iteration Square Koch Dipole Antenna for TT&C Downlink Applications in Small Satellites

“…CubeSats work typically in low earth orbits and have been used primarily by universities for research and space exploration, and they, as well as larger satellites, provide a wide range of research projects and applications. CubeSats are subject to a design protocol that specifies maximum outer dimensions equal to 100 × 100 × 100 mm 3 and it is worth mentioning that their electronic equipment is made of commercial off-the-shelf components [4][5][6]. The main reason for miniaturizing satellites is primarily to reduce deployment costs, since larger satellites require larger rockets of greater cost to finance.…”

“…Small satellites are not short of technical challenges, because they use innovative propulsion, attitude control, computer, communication, and power systems. Small satellites, as any wireless telecommunication system, also need to include antenna structures to perform core satellite functions [4]. Each of these functions requires different antenna configurations, which have commonly been helices, monopoles, and patches.…”

“…Other examples of microstrip antenna structures for small satellites are the patch antennas for the USUsat, including patch antennas for the up/downlinks resonating at 450 MHz and 2.26 GHz, respectively [9], and the square patch low-gain microstrip antenna at 2.45 GHz to optimize antenna placement for the ESEO and SSETI-Express [10]. Most antenna implementations target either the TTC or the payload data downlink subsystem [4] although recently a study on intersatellite cross-link antennas for picosatellites operating at 10.5 GHz has been conducted; this study consisted of modified Van Atta retrodirective arrays [11].…”

“…Printed antennas for small satellites have advantages such as integrating them into the structure, but, in scenarios like CubeSats, a challenging task is to print them on their reduced faces (100 × 100 mm 2 ) and make them resonate at relatively large wavelengths (70-centimeter band), since conventional /2 dipoles working at those frequencies are about 35 cm long and could not fit within those limited areas [4][5][6]. The aforementioned design challenge can be solved by using fractal antennas whose geometry is created through the successive iteration of a generator shape to a simple basis shape [12], using conventional antennas of size less than a quarter wavelength of the radiation bandwidth, and hence the efficiency is reduced [13].…”

A Hands-On Education Project: Antenna Design for Inter-CubeSat Communications [Education Column]

“…However, in the 437 MHz band, a square patch antenna with a side of A /2 would need a square surface of 155 mm on a side using an FR4 substrate, 50% more space than is available in a 100 mm x 100 mm face. From the antenna point of view, this means that innovative ways to miniaturize the antenna's size while maintaining adequate radiation features are required [10].…”