Sat-IP

2-way Satellite Flat Antenna in the Ku-Band for Use on Watercraft​

Two-way satellite flat antenna in the Ku-band for use on watercraft

Project Description

The project objective (see Figure 1) includes the development of a transceiver module for two-way satellite communication with an integrated flat antenna in the Ku-Band. To control the radiation characteristics, the flat antenna has the capability of beam steering in two spatial dimensions. Azimuth control is achieved mechanically through EANT’s platform, while electronic beam tracking is accomplished using reflection phase shifters developed at TUB. Additionally, a space-saving, unobtrusive, and robust design is sought, which is built using cost-effective printed circuit board technology. Besides watercraft in inland and open waters, potential applications include sailing yachts and motorboats. With adjustments and further developments, the concept can also be adapted for use in road and rail transport.

Work packages

The SAT-IP system generally addresses satellite communication technology. Specifically, a two-way satellite flat antenna is being developed for mobile use on both land and watercraft, offering significant functional and cost advantages over conventional parabolic antennas. This planar antenna, integrated with both transmit and receive capabilities, can be utilized on inland waters as well as on the open sea.
3 icons representing the application scenario
Fig. 1: Application scenario
The system is part of a closed satellite communication link, essentially consisting of three units: the ground station (hub or uplink station), the satellite itself, and a satellite antenna on the ship (Satcom terminal). In the ground station (hub), data is initially processed by encoders and modulators and transmitted to all participants who possess the satellite terminal. Each participant receives their respective data based on their IP address. This data is then recovered using a DVB-S2 receiver (ETSI standard). This constitutes the forward channel (pink arrow). Since the modem of the end device in the SAT-IP system is expected to be multimedia-capable, it is recommended to use the DVB-S2 standard as the transmission method. Currently, this is the most powerful satellite standard transmission method. For the return channel (green arrow), the TDMA (Time-Division Multiple Access) method is used as the multiplex access method or DVB-RCS (ETSI standard). The complete specification and partial parameters of the SAT-IP system in this work package have been defined in close collaboration with TU Berlin. To determine the size (aperture size) of the SAT-IP terminal antenna, a link analysis between the satellite and the ground station was conducted. Signals transmitted by satellites can only be received within predefined areas called “footprints” or coverage areas. Almost all programs broadcast in the German language are receivable through the Astra and Eutelsat satellite systems. The footprint represents the geographic area where a television or radio program is broadcast with a specific transmission power. The footprint is defined by outlining a geographical area with a specified radiation power (dBW). Often, the required parabolic antenna size within the footprint is specified. Large footprints with relatively low radiation power are referred to as “Global Beam,” while small footprints with high radiation power are referred to as “Spot Beam.” As mentioned above, we have chosen the satellite groups Astra and Eutelsat-Hot-Bird. To determine the available radiation power, the coverage areas of these two European satellites (Figure 2 and 3) were examined and compared. The centimeter measurements in Figure 2 indicate the antenna size required in each coverage area.
Fig. 2: Footprint Astra 19,2° East
Fig. 3: Footprint Eutelsat 13° East
Calculations can be performed in both directions: either starting from the diameter value or using the dBW value to determine the corresponding diameter. For example, in the following example: Dish diameter of 120 cm corresponds to EIRP (Effective Isotropic Radiated Power) = 45 dBW Dish diameter of 75/90 cm corresponds to EIRP = 47 dBW Dish diameter of 75 cm corresponds to EIRP = 48 dBW Dish diameter of 60 cm corresponds to EIRP = 50 dBW Consequently, the footprints of the ASTRA and EUTELSAT satellites cover wide parts of Europe. Therefore, we will choose a parabolic dish with a diameter of 75 cm and an EIRP value of 48 dBW. After determining the EIRP values for both satellites and the diameter of the parabolic dish, the antenna parameters of the SAT-IP system, such as gain, bandwidth, beamwidth, etc., for transmission and reception were calculated. Since the SAT-IP antenna radiates in two directions, we need to determine the antenna sizes in both directions. Downlink to the SAT-IP Terminal (Forward Channel) After determining the diameter of the parabolic antenna, the antenna gain was calculated. Assuming a typical aperture efficiency of 70% or 0.7, the gain of such an antenna for the Ku-Band downlink can be calculated as follows. The beamwidth of the parabolic antenna can be determined from the equation assuming a symmetric beam: The satellite signal on its way to Earth is subject to various sources of interference:
Drawing of a ship and a satellite communicating with each other during a storm
Fig. 4: Noise influence on the Sat-IP system
The power ratios on the downlink path from the satellite to the SAT-IP system are determined by the following factors:
  • Radiated power density of the satellite
  • Free-space path loss from satellite to Earth antenna
  • Atmospheric attenuation
  • Rain attenuation
We do not intend to calculate these factors in detail; rather, our focus is on the noise sources directly at the SAT-IP system that need to be determined individually. These relevant noise sources in the system are combined into equivalent noise temperatures at the antenna feed point. This noise source is called the overall system noise temperature (Tsystem). The noise temperature in the terminal station is composed as follows: Given: GAnt = 37.7 dBi TA = TSky + TBoden = 28 K Verlust im Feed (TX/RX) LFeed = 0.5 dB Positionierungsfehler = 0.5 dB TF = 290 K TR = 60 K TErdstation = TA / LFeed + TF (1 – 1 / LFeed) + TR = 116.4 K = 20.66 dB; The quality of reception at the SAT-IP terminal depends on the ratio of the antenna gain to the total noise temperature. This ratio is known as the G/T ratio and is a measure of the performance of the receiving system, taking into account environmental influences, the antenna, and the receiver. This means that the larger the gain and the lower the temperature, the better the result. More signal strength with less noise = a larger number = a better solution. To determine the G/T value, further losses (such as LR and LFRX, among others) must be considered in the calculation. A good starting point is to derive the system noise temperature expressed in its composite temperatures found in a satellite system. This requires initially determining the individual noise sources in the system. These are then combined into an overall noise source characterizing the entire system to derive the gain-to-temperature ratio (G/T). The noise temperature of the overall system (TSys) should be determined first. TSys = (1 / LR)Erdstation (1 / LFeed)Erdstation (1 / T)Erdstation = 0.5 dB+0.5 dB+20.66 dB = 21.66 K Then, the G/T ratio is calculated:

Uplink to SAT-IP Terminal (Return Channel)

The following two figures and Table 1 have been taken from the book “VSAT Networks Second Edition.” From the lower figure, you can read the antenna gain calculations for frequencies from 4 to 14 GHz:
Grafik
Fig. 5: Calculation of antenna gain / dB
In Figure 6, the uplink and downlink gain values for a 0.7m antenna diameter are visible, ranging between 36 and 39 dB.
Grafik
Fig. 6: Calculation of the maximum EIRP values from the terminal to the satellite at 14 GHz and output power of the power amplifier
From the figure shown above, the desired EIRP uplink values can be discerned. These values are also readable for a 0.7m antenna diameter. In the following table, previously tested common values for the Ku-band (14 GHz) are presented. The VSAT values for a 1.2-meter antenna diameter are of particular interest for this project.
Bild einer Tabelle
Fig. 7: Usual values of the Ku-band
To calculate the maximum output power (EIRPmax) achievable by the SAT-IP antenna, we use the Maximum EIRP and Current EIRP values. The calculated EIRPmax should fall within the values provided in the table. We calculate as follows: EIRPmax = Pout * Gmax / LFeed; where Pout = Maximum output power of the power amplifier Gmax = Maximum antenna gain LFeed = Loss between power amplifier and feedhorn We assume Pout = 2 watts, Gmax = 39 dB, and a loss LFeed = 1 dB. Thus, EIRPmax = 3 dBW + 39 dB – 0.5 dB = 41.5 dBW. This value of EIRP, as derived from the above table, corresponds to an antenna diameter of approximately 1.1m to 1.2m. The gain, EIRP, and G/T values calculated here are the established baseline values for the entire SAT-IP system. This comprehensive package was determined in collaboration with our partner, TU Berlin. The results have been documented in the requirements specification along with the circuit architecture by TU Berlin, concluding this work package.

When selecting the substrates for the antenna elements, there is usually a compromise between cost, processability, and radio frequency (RF) suitability.

EANT GmbH and its partner, TU Berlin, agreed on a two-step material selection process. First, the material properties of the FR4 substrate were examined. If the losses in this material became unacceptable at higher frequencies, the HF substrate Megtron 6 would be chosen. Both materials are readily available and relatively cost-effective.

For assembly reasons, the casing should be manufactured in two shells that need to be joined and screwed together via a structured interface. Adhesives cannot be used in this location since most adhesives absorb water and could promote corrosion. At the same time, the casing must meet the requirements of electromagnetic waves and should only minimally attenuate them. Additionally, it is necessary to consider potential aging processes of the casing. A conventional solution involves using Teflon, but considering the intended dimensions, this would become extremely expensive, and its mechanical durability is relatively low. Within the collaborative project, alternative material selection and suitable sealing concepts are being explored to address these challenges while maintaining a compact form. Radome materials that meet both the required mechanical and electrical properties include glass-fiber-reinforced plastics (organic resins such as epoxy resins or polycarbonates).

EANT has a supply chain for simple plastic radomes as well as more complex fiberglass radomes with a foam core. During the work on the demonstrator, significant investigations were carried out regarding the more complex fiberglass radomes due to their superior RF properties.

For this work package, all known feeding methods for the patch antenna were thoroughly examined. In comparison of all feeding possibilities, aperture-coupled patch antennas prove to be particularly advantageous. This patch antenna is suitable for integration into a group antenna, as it exhibits a high bandwidth and high gain. To enable a flexible concept, the aperture-coupled antenna elements are polarization-dependent on a feeding network, which allows two directions (vertical and horizontal). Our ultimate goal is a compact, small design. Therefore, it was of the highest priority to apply the elements and feeding network as flat as possible. The calculated gain of the parabolic antenna was transferred to our flat Satcom antenna to determine the effective surface area of the Satcom antenna: This resulted in an area of 29.5×118.4 cm2. Depending on the spacing between the elements, the antenna elements for the entire antenna are determined. For example, with 16×64 antenna elements, a spacing of 1.85 centimeters between the elements was determined. Initially, a single element was simulated and optimized using the above-mentioned aperture-coupled patches.
3D Ansicht Einzelpatch
Fig. 8: 3D View Single Patch
Design model of the single element The model consists of two patches. Typically, the upper patch is applied to an air-like substrate (e.g., foam). However, in our case, it cannot be directly printed onto the foam substrate, so we examined and chose the FR4 (Radome) substrate as the carrier for the patch. Patch 2 is directly on the FR4. The two patches are coupled with two slots each (vertical and horizontal), which, in turn, are excited by two microstrip lines (vertical and horizontal). Both microstrips are located on the FR4 substrate (see Figure 9).
Querschnitt
Fig. 9: 3D View Single Patch
For the design presented in this work, substrate 1 with a thickness of 0.5 mm and a dielectric constant εr = 4.4 and tan δ = 0.02, and substrate 2 with a thickness of 1.9 mm and a dielectric constant εr = 1.057 and tan δ = 0.02 were used. The dielectric conductivity of the foam is nearly the same as that of air, thus avoiding losses and optimizing the radiation effect. Substrate 3 had a thickness of 0.8 mm, and substrate 4 had a thickness of 0.5 mm, both with a dielectric constant εr = 4.4 and tan δ = 0.02. Therefore, the microstrip width for a targeted impedance of 50 Ω is determined to be 0.9 mm. The thickness of the copper sheet is 35 µm.

Simulation results

3D Darstellung des Gains
Fig. 10: Gain in 3D display: 8.22 dBi
Grafik: Anpassung und Isolation
Fig. 11: Adaptation and isolation
The simulation results showed very good values. According to the initial expectations, the gain value should be between 7 to 8 dB. The simulation result, as shown in Figure 10, achieves a gain of 7.4 dB at a frequency of 13 GHz with an efficiency of 70%. The isolation between the two polarizations (horizontal and vertical) is over 40 dB, as expected. Additionally, Figure 11 demonstrates a bandwidth of more than 2 GHz. From this single element, we simulated a row of the group antenna, consisting of a 1×8 module. Subsequently, its results were optimized according to our requirements. The feed system of the 1×8 row was integrated onto a substrate (dielectric) along with the antenna module. This attractive solution saves us a complete substrate for the feed system.

Beschreibung des Designmodells

3D-Model
Fig. 12: 1×8 elements model

Results of the Simulation

By decoupling the individual radiators, a significant improvement of the radiation characteristics was achieved. The results agree very well with the expected values.
3D Darstellung des Gains
Fig. 13: Gain in 3D display: 16.1 dBi
Grafik
Fig. 14: Adaptation and isolation of 1×8 elements
The next step was to develop an antenna consisting of 1×16 elements (design and construction).

Design model description

3D-Model top and bottom view
Fig. 15: 1×16 elements model

Simulation results

The simulation results for 1×16 elements also showed very good values. After optimising all parameters of the single element, several elements are combined into groups. Closely neighbouring antenna elements influence each other, which means that the composition of the individual elements has a great influence on the parameters of the group antenna. Step by step, elements are linked together and more are added.
3D Darstellung des Gains
Fig. 16: Adjustment and isolation of 1×8 elements
Graphic: Fitting and isolation of 1x16 elements
Fig. 17: Adjustment and isolation of 1×16 elements
Based on the simulation, an optimised 16×16 element antenna board was developed. The design for this is shown in Figure 18.
Graphic: 16x16 antenna element with transition to the control network
Fig. 18: 16×16 antenna element with transition to the control network
This allowed the final selection of the antenna concept.

Together with TU Berlin, a construction concept was developed. The focus of our work package was the review of the concept and the selection of the Block-Down Converter and Block-Up Converter.

The receiving and transmitting modules are used for communication with a satellite with the aim of transmitting data for internet applications. These consist of three essential components:

  1. Antenna with high gain and narrow beamwidth.
  2. Block-Down Converter, abbreviated as LNB (Ku-Band to L-Band).
  3. Block-Up Converter, abbreviated as BUC (L-Band to Ku-Band).

Satellites transmit their high-frequency signals (payload signals) from orbit at approximately 36,000 km above the Earth to receiving antennas on the ground. Due to the long path to Earth, these payload signals are heavily attenuated. A converter, consisting of a series of components, is required for post-amplification and conversion of the high-frequency signal into the intermediate frequency range. Initially, the operation of a conventional converter, as found in every satellite LNB, was considered. In such a converter, there is a low-noise preamplifier (LNA), a mixer for converting the signal into the frequency range (mixer), an intermediate frequency amplifier (IF Amplifier), two local oscillators with low phase noise (LO), and two filters before and after the mixer.

A Down Converter (LNB) functions to amplify and convert the signals focused by the satellite reception antenna into a lower frequency range. The converted signal is then sent to a DVB-S2 receiver via a coaxial cable. The signal coming from the modulator runs through another cable to the Upconverter (including an amplifier). The Upconverter converts the lower frequencies into a higher frequency range and amplifies the signal using power amplifiers (PA).

All necessary switching functions for the operation of BUC/LNB (e.g., the “idle mode” of the BUC, LNB band switching) must be possible through the processor of the integrated modem. Desirable BUC functions include an “idle” mode controlled by the modem and low power consumption when not transmitting.

To preserve the signal-to-noise ratio (SNR), low-noise amplifiers (LNAs) are preferred in high-frequency and microwave technology. They provide the ability to effectively eliminate the additional noise caused by lossy structures by pre-amplifying the signal. With suitable design of the amplifier, this can be achieved with very little increase in noise figure, even for high losses.

The use of LNAs is an old, proven, and methodical approach for preserving signal quality at the input of a receiver structure. In the following design document, this method is also used to protect the received signal from the losses caused by the phase shifters.

Without the use of these LNAs, the losses in the phase shifters of the phased-array antenna would reduce the signal-to-noise ratio by the amount of their losses. Assuming a 4dB insertion loss through the phase shifters, this would result in a reduction of SNR by exactly 4dB. Based on EANT’s long-standing experience, the following converter was selected: Universal Ku-Band LNB: NJR2842SN – 10.75 GHz – 12.7 GHz.

The Satcom modem is designed to ensure reliable digital data exchange using TDMA (Time Division Multiple Access) technology. The goal is to provide high-speed broadband internet access with cost-effective end-user equipment that offers targeted additional services beyond basic internet access. At the time of working on this task, the focus was on supporting geostationary services. Accordingly, the iDirect X7 modem (Rx: 950 MHz – 2150 MHz; Tx: 950 MHz – 1700 MHz) was selected, which is a common and widely used platform.

Satelliten-Modem: iDirect X7

Link: https://www.idirect.net/products/x7-satellite-router/

This modem offers an OpenAMIP (Open Antenna Management Interface Protocol) interface for antenna control, which has been implemented and tested. It automatically transfers satellite parameters, including orbit position, downlink and uplink frequencies, and symbol rate, to the tracking receiver’s control unit. The interface supports both a serial connection protocol and an Ethernet interface. After extensive testing of the modem on the Telenor network with broadband services and the OpenAMIP protocol for antenna control, this task was completed. Since the OpenAMIP interface is a standardized interface for antenna control, the results of this task are also applicable to other SatCom modems and are not limited to the model used here.

In the 6th work package, the industrial manufacturing process for the individual components was developed. These components are divided into the antenna aperture, the mechanical positioner, and the housing/radome.

Antenna Aperture and Connection to the RF Frontend

In the first step of manufacturing a functional prototype, the antenna structures (feeding, honeycomb core, and patch array) were initially manufactured separately. The honeycomb core is glued to the feeding network using epoxy adhesive and then connected to the patch array. The schematic structure is shown in Figure 19, and photos of the components are provided in Figures 20 and 21.
simple graphic representation of the structure
Fig. 19: Schematic structure of the antenna
Vereinzelter Aufbau der Antennen mit Feeding Netzwerk, Rohacell und Patch-Array Abbildung
Fig. 20: Separate construction of the antennas with feeding network, Rohacell and patch array
Feeding Netzwerk der Apertur
Fig. 21: Feeding network of the aperture
The shown layer structure is still being manufactured by TU Berlin as part of the project and assembled individually. In parallel, discussions were held with the company Becker und Müller, which is supposed to implement the industrial assembly. One disadvantage of Rohacell is that it is not a standard substrate for printed circuit board technology. However, Becker und Müller, as one of the first manufacturers, has pressed the Rohacell material into layer structures for printed circuit boards. It is planned to approach Becker und Müller with the layout data for industrialization in the next step to have it examined. Subsequently, the further practical implementation of the industrial manufacturing process will be coordinated with the company. The work is intended to be finalized after the project.

Mechanical Positioner

Next, the development and assembly of the mechanical positioner will be presented. The starting point for the positioner is the requirement to align the antenna aperture in azimuth with the satellite, as well as to provide all mechanical interfaces for electronic components and the aperture. Since the antenna aperture realizes tracking and alignment in the elevation axis and skew electronically, a mechanical drive was provided for alignment in the azimuth direction. The original “turntable” principle has been further developed into a belt drive with an additional gear stage. Azimut-Antrieb des DemonstratorsDriven by a stepper motor, this setup allows positioning in the hundredth degree range and provides sufficiently high acceleration (> 500°/s²) and speed (approximately 100°/s). With these values, the mechanical positioner is suitable for both maritime and land mobile use. Furthermore, a 2-channel rotary coupling for high-frequency signals up to 2.5 GHz was provided, as well as 2 slip rings for the DC power supply of the electronic components. This setup allows unlimited rotation and positioning of the system in azimuth and the transmission of all necessary signals between the outdoor and indoor units (modem) via a terminal assembly integrated into the housing/radome of the system. The mechanical interface to the aperture is formed by 2 milled parts that create a 45° angle to the baseplate of the positioner. While angling the aperture increases the profile of the system, it significantly enlarges the operating range of the antenna system for geostationary satellites, as lower elevation angles can be targeted. The positioner also includes mechanical interfaces for attaching the antenna control and an IMU (Inertial Measurement Unit). The following illustrations show the CAD construction model, which serves as the basis for all derived construction drawings and the assembly of the positioner.
Rückansicht des Technologie-Demonstrators
Fig. 22: Rear view of the technology demonstrator
Frontansicht des Technologie-Demonstrators
Fig. 23: Front view of the technology demonstrator

Gehäuse / Radom

In addition to the outer shape, the general structure and material selection were of great importance in the development of the radome. The material composition determines the strength, environmental, and high-frequency properties, and high demands must be placed on each of these properties. The antenna system is used exclusively outdoors and is exposed to environmental factors such as rain, wind, temperature fluctuations, and UV radiation. The high wind loads should only lead to limited deformations, and the structure must withstand wind speeds of up to 200 km/h. The attenuation values in the receive and transmit frequency range should be as low as possible, and the radiation pattern should be minimally influenced by the radome in every “line of sight” of the aperture.
Radom-Entwurf transparent
Fig. 24: Radome design transparent
Radom-Entwurf
Fig. 25: Radom design
To ensure these properties while maintaining a low-profile design, close discussions were held with potential suppliers, and the possible design was iteratively adjusted. As a result, a manufacturing process was defined that met all the requirements. The planned structure involves a composite construction consisting of foam and glass fiber-reinforced resin layers with a predetermined thickness. The final radome design was not commissioned for production during the Sat-IP project’s runtime. To manufacture it, an expensive tooling process would have been necessary, which would not have been economically justifiable for a technical demonstrator (approximately 20,000 EUR). Since a modular design was chosen for the aperture concept depending on the target application, the final dimensions in an end-use scenario are not yet known. However, all the technological prerequisites have been created for a simple and quickly feasible adaptation development, in case the radome production is to be commissioned for a changed aperture geometry.
In WP7, the prototype was built based on both the existing antenna control technology of EANT GmbH and the mechanical and electronic interfaces and requirements of the antenna aperture specified in the project. The adapted mechanical components for the prototype were developed using the CAD program Inventor. Based on these models, manufacturing drawings were derived, and subcontracting companies were subsequently commissioned for production. After delivery and quality control, the assemblies were assembled and finally adjusted.
Teilaufbau des Positionierers ohne Apertur
Fig. 26: Partial structure of the positioner without aperture
To facilitate subsequent tests of the demonstrator, a substructure was integrated, suitable for mounting on a “lake simulator,” a car, or a ship, providing an ideal platform for field tests with the system. After completing the mechanical positioner, the interfaces for integrating the flat antenna aperture were incorporated, and at the end of the work package, an evaluation platform was available for further testing.

The tasks to be carried out in the context of WP8 include tests with the prototype to empirically analyze its characteristics and all necessary preparatory work. Fundamentally, these tasks can be divided between work and tests on the mechanical positioner and those on the aperture. Tests on the overall system primarily focused on mechanical mounting and integration, as well as tests on the electronic interfaces for controlling the aperture.

During the preparations for WP8, a significant change in the market situation for the technology developed in the project became apparent. This is detailed in the final report. Accordingly, this development influenced the definition of field tests and the work carried out, shifting the project’s focus more towards LEO constellations. However, the final parameters for gain, tracking range, polarization, and terminal calculation are not fully known and can only be partially estimated for this application. The EANT has been in discussions with constellation operators and partners to finalize these parameters. For instance, the requirements for polarization have changed to now include support for circular polarization. Initial estimates suggest that the necessary EIRP levels will be lower than those of common geostationary applications with comparable 45 cm reflector antennas. The frequency range of some prevalent constellations will fall within the specified range for the aperture.

Considering these circumstances, a single module was initially manufactured for the prototype, as it allows for flexibility in responding to changing market conditions. At this point, field tests with a satellite connection could not be conducted because such tests currently require proprietary hardware that EANT does not possess. The evaluation of the performance of the developed aperture module is conducted by the project partner, and the results are discussed in the final report from TU Berlin. Even with the altered requirements regarding suitability for constellations, the final evaluation of the aperture will be completed after the project.

Gesamtaufbau des Positionierers mit Flach-Antennen-Apertur (Einzelmodul)
Fig. 27: The overall structure of the positioner with flat antenna aperture (individual module)

Static and dynamic tests were performed on the mechanical positioner. To control the aperture, the existing antenna control system was expanded to include an electronic interface for aperture control. An EMC and EMI-suitable connection with differential line routing was specified and integrated in consultation with the project partner from TU Berlin, as well as tested. Alongside the selection of interface drivers, a transmission protocol was defined with predefined commands for transmitting diagnostic information and controlling the aperture. For instance, this protocol is used to set the elevation target angle and query the state of the antenna aperture.

All electronic connections and cables were assembled and then electrically and, where necessary, measured and tested on high-frequency measurement devices. It was ensured that the achieved reflection factors and transmission behavior allow for trouble-free operation.

To prepare for the tests, the mechanical positioner was put into operation in individual assemblies during assembly and final assembly. The result was that the motor control, in conjunction with the mechanical drive, achieved the desired characteristics. However, when driven with high accelerations and speeds, weaknesses in the torsional rigidity of the base plate and substructure of the system became apparent. These weaknesses were reworked and resolved as part of a redesign.

The algorithms for determining the antenna’s position and optimizing its alignment were expanded to support electronic deflection in the elevation axis. Since in mechanical optimization, the sensor system itself is deflected, and in electronic deflection only the main beam direction but not the sensor system (IMU) itself is moved, corresponding adjustments had to be made to the existing tracking algorithm. For this purpose, on the one hand, the model of the KALMAN filter for position estimation in sensor data fusion was extended with corresponding routines, and the motor control within the optimization routines was adapted to instead generate purely electronic adjustment. The routines for controlling the aperture and position estimation as well as signal optimization were tested and verified in laboratory setups.

Based on the described work, the predefined functionalities and specifications were compared with the realized characteristics. The results are presented in tabular form below. It should be noted that only a single aperture was implemented, and adjustments had to be made to accommodate a partially modified requirements profile.

The basis for the further development and optimization of the antenna system was formed by the insights from WP8 and the analysis of market developments. As a direct result of the findings from the conducted functional tests, the stability and rigidity of the mechanical positioning had to be improved for further tests of the optimization and localization algorithms. For this purpose, the base plate and support system were revised. The base plate was completely manufactured as an aluminum milled part with multiple bends to avoid open vibration-prone profiles. On the support system, cutouts on aluminum profiles were reduced to ensure mechanical integrity under all operating conditions. The results were verified through field tests on a car and using a vibration platform. No further problems were identified with other components of the mechanical positioner and the electronic interfaces between the antenna control and the aperture, so no adjustments were necessary.
überarbeitete gefräste Grundplatte
Fig. 28: revised milled baseplate
An important factor in planning the redesign of the system and adaptation developments to Sat-IP technology, both during and beyond the project’s duration, was the analysis of the market situation. As previously described, in the field of satellite communication, new privately funded technology companies have entered the market as part of the NewSpace developments to compete with traditional geostationary service providers in the maritime “On The Move” market. This year marks the first time that a corresponding commercial service is being offered. The constellation providers are offering high-performance data with extremely competitive contracts compared to traditional geostationary offerings. Since satellite flat antennas benefit significantly from constellation developments and offer the greatest growth potential, the further development and marketing of Sat-IP technology will focus on these applications. In coordination with TU Berlin, relevant work will continue together until December 2022. In summary, the following performance parameters for the Sat-IP aperture were achieved in collaboration with TU Berlin:
Parameter Values according to specifications Values reached in project
Size 30 x 30 cm2 40 x 30 cm2
Weight <6 kg <6 kg
Frequency range Tx 13.75 – 14.5 GHz 13.75 – 14.5 Ghz
Frequency range Rx 10.7 – 12.75 GHz 10.7 – 12.75 GHz
Max. Transmitting power 39 dBw 41 dBw
Max. Backflow attenuation >10 dB >10 dB
Antenna gain Tx 33 dBi 30 dBi
Antenna gain Rx 33 dBi 30 dBi
Half-width Tx 2° 2°
Half-width Rx 1° 1°
Angle resolution Tx (Phase shifter) 1.5° 1.5°
Winkelauflösung Rx (Phasen shifter) 1° 1°
Control range (Azimuth) 360° 360°
Control range (Elevation) 60° 60°
Polarisation Dual (vertical/horizontal) Dual
Temperature range -20…60°C 20…60°C

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