Patch Antenna System for CubeSats in L band

An L-band patch-antenna system for CubeSat applications is presented in this paper. The high-permittivity dielectric loading reduces the size of individual antennas to make them suitable for a CubeSat platform. Two circularly polarized patch antennas were designed for the downlink and uplink frequencies of 1.53 and 1.63 GHz, respectively, and the antenna prototypes were characterized. A two-element, sequentially rotated antenna array was designed using the uplink patch element at 1.63 GHz, with a beam tilt of 20° from broadside. The array is to be employed in a system of four arrays that provide two tilted beams with dual-band coverage in each beam, for an increased system capacity. The arrays are located on the backside of the 3U-CubeSat solar panels, facing Earth. While the panels are stowed, the antennas of two arrays are interleaved, reducing the required stowage volume

Wideband Cavity-Backed CubeSat Antenna in S band

The Telemetry, Tracking and Command (TT&C) antennas are a crucial component of small satellites, as their in-orbit attitude is not always well-defined. The TT&C antenna design for a CubeSat is an even more challenging task, considering the volume restrictions imposed by the standard, and the bandwidth requirements for a duplex communication. A detailed design process of a low profile S-band antenna, suitable for CubeSat applications, is presented in this paper. The fabricated prototype exhibits a 10-dB impedance bandwidth of 40%, and a 3-dB AR-bandwidth of 32%

GABA-Producing Natural Dairy Isolate From Artisanal Zlatar Cheese Attenuates Gut Inflammation and Strengthens Gut Epithelial Barrier in vitro

Probiotic bacteria are recognized for their health-promoting properties, including maintenance of gut epithelial integrity and host immune system homeostasis. Taking into account the beneficial health-promoting effects of GABA, the presence of the gadB gene, encoding glutamate decarboxylase that converts L-glutamate to GABA, was analyzed in Lactic Acid Bacteria (LAB) natural isolates from Zlatar cheese. The results revealed that 52% of tested Lactobacillus spp. and 8% of Lactococcus spp. isolates harbor the gadB gene. Qualitative and quantitative analysis of GABA production performed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) revealed the highest GABA production by Lactobacillus brevis BGZLS10-17. Since high GABA-producing LAB natural isolates are the most valuable source of naturally produced GABA, the probiotic properties of BGZLS10-17 were characterized. This study demonstrated high adhesion of BGZLS10-17 strain to Caco-2 cells and the ability to decrease the adhesion of Escherichia coli ATCC25922 and Salmonella enterica C29039. Treatment of differentiated Caco-2 cells monolayer with BGZLS10-17 supernatant containing GABA alleviated inflammation (production of IL-8) caused by IL-1β and significantly stimulated the expression of tight junction proteins (zonulin, occludin, and claudin 4), as well as the expression of TGF-β cytokine leading to the conclusion that immunosuppression and strengthening the tight junctions can have significant role in the maintenance of intestinal epithelial barrier integrity. Taken together the results obtained in this study support the idea that using of GABA producing BGZLS10-17 probiotic strain could be a good strategy to modulate immunological response in various inflammatory diseases, and at the same time, it could be a good candidate for adjunct starter culture for production of GABA-enriched dairy foods and beverages offering new perspectives in designing the novel functional foods

Antennas for CubeSat Communication

CubeSats are a type of small satellites (< 500 kg) that weigh several kilograms and consist of multiple Units (U) measuring 100 × 100 × 113.5 mm3. CubeSats emerged as a low-cost alternative to conventional large satellites, and have since demonstrated capabilities for communication, Earth observation, technology demonstration and many other. The primary goal of CubeSats, as it is the case with any miniaturized satellite, is to reduce the cost of orbital deployment. CubeSats are commonly launched as a secondary payload on large launch vehicles. One or several satellites are placed in a dedicated deployment system, which typically accommodates three CubeSat Units. The deployment system strictly limits the dimensions of any features on the CubeSat surface. CubeSat antennas perform the same functions as antennas on conventional satellites, such as telemetry and command, communication, navigation or inter-satellite links (ISL). However, most traditional antennas for small satellites are not suitable for CubeSats due to the profile constraints of the deployment system. Two approaches for antenna design are generally adopted. In the first, one or several low-profile antennas are placed on the CubeSat exterior. In the second, deployable antenna structures are used if the CubeSat platform does not offer sufficient dimensions. At low frequencies, the additional space is required to achieve a good radiation efficiency, whereas at high frequencies an increased antenna aperture provides a high gain. This thesis describes several antenna geometries, both low-profile and deployable, which enable several communication aspects of an Internet-of-Things (IoT) constellation of 3U CubeSats in the Low Earth Orbit (LEO). The main novelty of the proposed solutions is in their electromagnetic performance, as opposed to most CubeSat antenna designs where the mechanical design is the main achievement. The presented antennas succeed to exhibit a wide bandwidth or a specified radiation under strict size constraints. The thesis presents several wideband aperture-coupled patch antennas for TT&C and data downlink in S and X bands. A thoroughly investigated shielded-stripline feeding structure enables a wideband circular polarization (CP) with a unidirectional radiation, and demonstrates capabilities such as interference suppression of adjacent frequencies and efficient CubeSat integration. Patch-antenna arrays in L band are then presented, which radiate several independent beams for the capacity increase of an IoT machine-to-machine (M2M) communication system. The high permittivity of the antenna substrates lead to a strong coupling to the 3U CubeSat structure, emphasizing the importance of the antenna placement. Finally, different configurations of high-gain fixed-beam reflectarrays (RA) and transmitarrays (TA) are for the first time proposed for CubeSat ISL LEO communications in K band. Two novel unit cells are presented for RA and TA antennas, based on coupled loops and aperture-coupled patches, respectively. An axially corrugated CP horn antenna is designed as the feeding element for the arrays. A prototype of this antenna is fabricated using additive manufacturing in aluminum. The performance of all antennas, presented in this thesis, is validated by agreements between the calculation and 3D-simulation results and the VNA and anechoic-chamber measurements of several prototypes

A Comparison of Three Feeding Networks for CubeSat L/S-dual-band Stacked-Patch Antennas

The CubeSat nanosatellite standard puts strict limitations on the antenna volume, resulting in a low impedance and axial-ratio (AR) bandwidths of patch antennas. The AR of a circularly polarized patch antenna can be improved with the introduction of a dedicated feeding network. However, the antenna gain cannot be influenced, and it will be comparable to a conventional single-feed CP patch. This is demonstrated on three different feeding networks for dual-feed stacked-patch antennas in L and S bands, based on T-junction dividers, Wilkinson dividers, and branchline couplers. Based on their performance and size, the model based on Wilkinson dividers has the optimal performance for CubeSat applications in L and S bands

Circularly Polarized Transmitarray Antenna for CubeSat Intersatellite Links in K-Band

A circularly polarized transmitarray antenna based on aperture-coupled patches is presented for CubeSat intersatellite-link applications in K-band. The concept of aperture coupling simplifies the design of transmitarray elements, as it omits the need for metallized vias. Compared to a five-layer element geometry previously proposed in the literature, the total number of metallic layers is reduced to three metallic layers, as a result of a simple modification in the shape of the crossed coupling slot. The new element has a total profile of 0.13 lambda(0) at 24.6 GHz and exhibits a stable performance over a range of incidence angles. The element is incorporated in a 900-element offset-fed transmitarray antenna. The antenna prototype exhibits a gain of 31.6 dBi with a maximum efficiency of 57% and a 1 dB gain bandwidth of 5.7%. The measured axial ratio is below 0.6 dB across the entire gain bandwidth

Aperture-Coupled Low-Profile Wideband Patch Antennas for CubeSat

This communication presents the design and measurement results of aperture-coupled stripline-fed wideband patch antennas for nanosatellite applications. The low-profile requirements lead to a strong back radiation from the coupling aperture. Instead of suppressing the resulting electric field in the feeding stripline, an advantageous field distribution is used to boost the electromagnetic coupling to the radiating element. This effect is achieved by enclosing the stripline feeding structure with vertical conductive walls, effectively creating a cavity. The obtained antenna has a low profile of 0.08 lambda 0 at 2 GHz and exhibits 3 dB gain and axial ratio bandwidths of 27% and 32%, respectively. The effect of cavity resonances is analyzed in detail and we show how it is used to reduce the interference in adjacent frequency bands. This communication also proposes an elegant method of integrating this type of antennas into the satellite chassis, which reduces the antenna extrusion on the satellite surface. The two proposed methods are demonstrated through another antenna prototype mounted on a low-cost CubeSat mock-up

Circularly Polarized Axially Corrugated Feed Horn for CubeSat Reflectarray Applications

Retlectarray (RA) and transmitarray (TA) antennas that use the element-rotation technique require the radiation from the feeding antenna to be circularly polarized (CP). A CP axially corrugated horn antenna is developed as a feeding element for CubeSat RA and TA antennas. The CP operation is enabled using a septum polarizer. The all-metal geometry is attractive for space applications and allows the horn to be 3D printed in aluminum in a single piece. A prototype of the feed chain was fabricated using the Direct Metal Laser Sintering (DMLS) technique. The results of 3D simulations and VNA/far-field measurements of the feed chain arc presented in this paper

Antenna for a Cranial Implant: Simulation Issues and Design Strategies

The design of a specific antenna for a cranial implant is used to illustrate design and simulation issues linked to implantable antennas. After a brief introduction, we will review the requirements for the antenna, and go through the design process, discussing the tools used and the issues encountered. The final design will then be presented and discusse