Inter-CubeSat Communication with V-band "Bull's eye" antenna

We present the study of a simple communication scenario between two CubeSats using a V-band “Bull's eye” antenna that we designed for this purpose. The return loss of the antenna has a -10dB bandwidth of 0.7 GHz and a gain of 15.4dBi at 60 GHz. Moreover, the low-profile shape makes it easily integrable in a CubeSat chassis. The communication scenario study shows that, using 0.01W VubiQ modules and V-band “Bull’s eye” antennas, CubeSats can efficiently transmit data within a 500 MHz bandwidth and with a 10-6 BER while being separated by up to 98m, under ideal conditions, or 50m under worst case operating conditions (5° pointing misalignment in E- and H-plane of the antenna, and 5° polarisation misalignment)

Bull's eye leaky wave antenna for terrestrial and space applications

This work presents the study of Bull's eye antenna designs, a type of leaky wave antenna (LWA), operating in the 60 GHz band. This band emerged as a new standard for specific terrestrial and space applications because the radio spectrumbecomes more congested up to the millimetre-wave band, starting at 30 GHz. Built on existing Bull's eye antenna designs, novel structures were simulated, fabricated and measured, so as to provide more exibility in the implementation of wireless solutions at this frequency. Firstly, the study of a 60 GHz Bull's eye antenna for straightforward integration onto a CubeSat is presented. An investigation of the design is carried out, from the description of the radiation mechanism supported by simulation results, to the radiation pattern measurement of a prototype which provides a gain of 19.1 dBi at boresight. Another design, based on a modified feed structure, uses a microstrip to waveguide transition to provide easier and inexpensive integration of a Bull's eye antenna onto a planar circuit. Secondly, the design of Bull's eye antennas capable of creating beam deflection and multi-beam is presented. In particular, a detail study of the deflection mechanism is proposed, followed by the demonstration of a Bull's eye antenna generating two separate beams at ±16° away from the boresight. In addition, a novel mechanically steerable Bull's eye antenna, based on the division of the corrugated area in paired sectors is presented. A prototype was fabricated and measured. It generated double beams at ±8° and ±15° from the boresight, and a single boresight beam. Thirdly, a Bull's eye antenna capable of generating two simultaneous orbital angular momentum (OAM) modes l = 3 is proposed. The design is based on a circular travelling wave resonator and would allow channel capacity increase through OAM multiplexing. An improved design based on two stacked OAM Bull's eye antennas capable of producing four orthogonal OAM modes l = (±3,±13) simultaneously is presented. A novel receiving scheme based on discretely sampled partial aperture receivers (DSPAR) is then introduced. This solution could provide a lower windage and a lower cost of implementation than current whole or partial continuous aperture

V-band Bull's eye antenna for multiple discretely steerable beams

We present a new approach to designing V-band Bull’s eye antenna so as to produce multiple beams, which are either fixed or discretely steerable. Bull’s eye antennas comprise concentric rings around a subwavelength aperture. Beam deflection is accomplished by adjusting the effective spacing of the rings, which we explain in terms of the coupling angle to free space and surface waves. We show that multiple beams can be obtained from a single antenna, with the deflection of each beam being controlled independently by the relevant portion of the ring pattern. We demonstrate the principle through rigorous full-wave simulations of two-beam antennas with symmetrical and asymmetrical shifts, and give experimental results for a prototype milled in aluminium, with two separate fixed beams each deflected 16° to either side of the broadside. We also propose means to obtain up to six different beam arrangements during operation by mechanically rotating a plate containing a special six-sector ring pattern. Our simulated example gives three patterns, a single broadside beam or two beams each deflected by 8° or 15°. The radiation efficiency of the antenna is 97%, and the gain of a single undeflected beam is 18.1dBi

A CubeSat for Calibrating Ground-Based and Sub-Orbital Millimeter-Wave Polarimeters (CalSat)

We describe a low-cost, open-access, CubeSat-based calibration instrument that is designed to support ground-based and sub-orbital experiments searching for various polarization signals in the cosmic microwave background (CMB). All modern CMB polarization experiments require a robust calibration program that will allow the effects of instrument-induced signals to be mitigated during data analysis. A bright, compact, and linearly polarized astrophysical source with polarization properties known to adequate precision does not exist. Therefore, we designed a space-based millimeter-wave calibration instrument, called CalSat, to serve as an open-access calibrator, and this paper describes the results of our design study. The calibration source on board CalSat is composed of five "tones" with one each at 47.1, 80.0, 140, 249 and 309 GHz. The five tones we chose are well matched to (i) the observation windows in the atmospheric transmittance spectra, (ii) the spectral bands commonly used in polarimeters by the CMB community, and (iii) The Amateur Satellite Service bands in the Table of Frequency Allocations used by the Federal Communications Commission. CalSat would be placed in a polar orbit allowing visibility from observatories in the Northern Hemisphere, such as Mauna Kea in Hawaii and Summit Station in Greenland, and the Southern Hemisphere, such as the Atacama Desert in Chile and the South Pole. CalSat also would be observable by balloon-borne instruments launched from a range of locations around the world. This global visibility makes CalSat the only source that can be observed by all terrestrial and sub-orbital observatories, thereby providing a universal standard that permits comparison between experiments using appreciably different measurement approaches

Directivity enhancement of V-band “Bull’s eye” antenna with dielectric superstrate

We study the performance of a V-band “Bull’s eye” antenna with addition of a dielectric superstrate. We find that a single 0.25mm RF-35 Taconic substrate, at a distance of 6.5mm from the “Bull’s eye” antenna structure, allows a directivity enhancement of 2.6dB, to reach 21.6dBi at 60GHz. Efficiency remains almost the same as without and bandwidth is slightly increased. Comparison of the E- and H-plane radiation patterns shows an improvement of the directivity with reduction of the secondary lobes. We discuss the directivity improvement over the frequency band of interest (55-65GHz) and investigate the cause of the enhancement by considering field plots and angle dependant Fresnel reflection from the superstrate

Analytical and full-wave analysis of square and ring patch structures for reflectarray unit cells

A theoretical analysis of a square structure, and a ring structure, for use in reflectarray antenna unit cells is presented. We calculate the complex reflection coefficient from the coupling between an incoming wave and the resonant modes of the studied structure. To obtain a more accurate model for both structures, we account for the ratio of resonator to cell size, fringing fields and high frequency effective permittivity. Fullwave simulation using periodic boundary conditions is used to compare the simulation results with the analytical model. The model shows a good agreement for the phase versus patch dimension over a greater range of thickness and dielectric permittivity than previous models. A prototype reflectarray antenna, using these structures, is currently being fabricated

Low-Profile Antenna Package for Efficient InterCubeSat Communication in S- and V-band

CubeSats have been under intensive investigation for the last decade or so. The concept of constellations has emerged in response to increasing CubeSat capabilities, especially in altitude and positioning control. A constellation will most likely consist of CubeSats distributed across a finite planar region parallel to the earth’s surface, perhaps a few hundred metres or a kilometre across (depending on numbers). Besides spreading the risks and the costs of a mission, constellations can be far larger from edge to edge than the arms of even the largest conventional satellites (typically a handful of metres). For example, the OLFAR (Orbiting Low Frequency Array) mission is designed for radio astronomy observation below 30MHz. At those low frequencies, large aperture of over 10km is a must to achieve required spatial resolution, operating as a distributed aperture synthesis array. High-data rate communication is key for the success of such a configuration. The 60GHz band provides 12GHz of bandwidth for inter-satellite communication (59GHz to 71GHz). Yet the communication system must respect the mechanical and electrical requirements of the Cubesat platform, such as the tradeoff between radio power and communication distance. We will first describe the design and simulation of a very low profile antenna package including two 60GHz Bull’s eye antennas and a low frequency antenna for channel control tasks. We previously experimentally demonstrated an individual Bull’s eye antenna with good agreement to simulated results. In our double antenna design, we expect to obtain 4.7GHz of bandwidth, a moderately high gain of 18dBi and a high efficiency (95%), using two orthogonal polarisations for the transmit and receive antennas. Each antenna is fixed as transmit or receive only, due to the 60 GHz chipset that is currently available to us. This antenna package is completed by an omnidirectional 2.4GHz-modified Planar Inverted F Antenna (PIFA) suitable for a reliable low-data-rate link over which channel management data can be sent. The full antenna package is readily integrable onto a 0.5U face of a CubeSat with a total thickness of 6.4mm. We finish with an evaluation of the 60GHz link budget and expected performance of such a system, based on commercially available V-band transmitter and receiver modules

Planar Antenna for Transmitting Microwave Power to Small Unmanned Aerial Vehicles

We present the design and simulation of a leaky wave antenna that has been modified to permit high power handling and produce a conical beam that is suitable for transmitting microwave power to small unmanned aerial vehicles (SUAV). We show a design with a single vertical beam of gain 25 dBi that could support the simultaneous transmission of power to three rotary winged SUAV. It would be powered by a 5 kW UHF (915 MHz) magnetron-based generator. We also show a design producing a conical beam of gain 18 dBi that would allow multiple conventionally winged, electrically propelled to fly in a circular path around the antenna, at altitudes of 10-30 m, whilst dipping a wing into the beam. The wing would contain a rectenna, or an array of rectennas, depending on mission requirements and SUAV design, and receive 15 W per rectenna at 10 m assuming a 30 kW transmitter

Leaky Wave Bull's Eye Antenna in V-Band with Mechanically Steered Dual Beams

We experimentally demonstrate a mechanical steering mechanism for a Bull's eye antenna. Following holographic antenna principles, a leaky wave is fed onto a circular plate. The circular plate contains three pairs of opposing sectors, each of which is patterned to achieve a different beam steering effect. The circular plate is rotated under a mask that obscures two of the pairs of sectors, leaving only one pair of sectors exposed and able to influence the beam. We illustrate the flexibility of our approach with a design allowing a single beam along the boresight (0°), or double beams at either ±8° or ±15°. The gain is better than 15dBi for all beams

Parametric study of a double shifted "bull's eye" structure at V-band for beamforming

We study a “Bull’s eye” antenna with double shifted rings structure at 60GHz. We conducted a parametric study of a symmetric configuration, and we predict that two lobes can be steered to opposite sides of the normal by up to 18.6°. This is a similar range to a single shifted “Bull’s eye” antenna that we studied earlier, except the double structure produces two lobes. These two lobes can be created without sacrificing the efficiency or directivity relative to a single “Bull’s eye” antenna