This paper presents the Thales Alenia Space in Italy design and development of an EM-model of a Ka-Band Beacon Tx based on RF-on-PCB technology.
The new Ka-Beacon Tx has been conceived with the aim of strong reduction of product cost and time.
The technology selected to reach the target is the RF-On-PCB based n MEGTRON6 substrate. This technology will allow the reduction of the costs of the hardware, allowing the use of Commercial Of The Shelf (COTS) components.
The delivery time will be reduced as well due to the tuningless approach and automatic mounting processes.
Basing on standard equipment specification the target is to develop a new Ka-Beacon Tx with the following key Characteristics:
• Output power :1W Minimum
• Power consumption: 19W maximum
• Simplified Product Three: with 1RF PCB and 1 DCDC Converter PCB
• Production time reduction:
o Tuningless Circuits
o All the components are packaged SMD
o Automatic mounting of the RF on PCB
The Ka-Beacon Tx includes a DC/DC converter PCB providing the power supply voltages to the RF section, which implements the following functions:
• Downlink Carrier generation in Ka - Band
• Power amplification up to 1W
• Hardwire Frequency carrier selection
• Dual frequency option selectable by means of Low Level Command (LLC)
• Phase Modulation of the Carrier modulation performed @10 GHz, x2 multiplier to arrive to 20GHz (optional function)
• Loop Stress TLM, Power TLM, Temperature TLM, Secondary Voltage TLM, Lock detection TLM
• SMA Ka RF Output foreseen. Further implementation will also foresee the use of Ka waveguide.
The paper will describe the architecture and enabling technology, the design phase with simulation results and the developed RF-on-PCB at Engineering Model level.

Following Philae-Rosetta and Mascot-Haybusa2 Intersatellite links successes, CNES decided to develop a new generation of ISL link equipment for future exploration missions. The two main requirements for this new development were to address a multipoint communication protocol between units with localization capabilities.

This demonstrator developed with Syrlinks is based on the NanoTT&C equipment of Syrlinks product line. The addressed network topology is based on a star network with a master node (orbiter) and up to 1024 slave nodes (landers). The link is established and closed in a session way in S-band by the orbiter, in full-duplex, with one of the lander nodes. The developed communication protocol is derived from the CCSDS Proximity Link protocol and reuses thus the same header and frames strategy. The access resource is shared by the different lander nodes following a Time Division Multiplex method. Each node may be addressed on two different frequencies in case of jamming detected by the orbiter after a channel sounding achieved before each session beginning. A low-complexity ranging algorithm was implemented on the orbiter side allowing transmitting tones in a coherent way to the lander unit. The retransmitted signal is then processed by the orbiter OBC to compute the distance between both nodes. Several custom tone frequencies are used, in order to allow iterative disambiguation of the distance as presented in the ESA-100K standard.
The developed communication protocol is able to handle data transmission sessions, ranging sessions or data plus ranging sessions. A precision of one meter may be reached in case of favorable link budgets.
Data transmissions may be established up to a 512 kb/s uncoded data rate for the telemetry link, the link being protected with a ½ convolutional code.
Radiofrequency adaptations were also done on the equipment and especially on the diplexer in order to cope with ISL link specificities. The first part of this paper will thus detail the ISL demonstrator requirements and its associated detailed definition. The presentation of the measured performances of the currently developed demonstrator (1 orbiter and 2 lander nodes) will then assess the use of this new development for future exploration missions.

The demonstrator previously developed went through multiple table tests in Syrlinks premises to validate on one hand the multipoint protocol functionalities: session opening and closing, jamming, unexpected session closing and on the other hand the ranging measurements performances. For this part of validation, orbiter and lander elements were communicating through a cable with a variable attenuation simulating a shorter or a longer distance. A full validation tests campaign is foreseen in CNES premises to assess the demonstrator performances in a more representative environment: open-field radiating, jamming, quick distance variations, link breaks. The second part of this paper will detail this test plan and its objectives.

Finally, the objective of this demonstrator is to embark this new generation of ISL product on the future exploration missions. One of these opportunities could be the MMX mission. The MMX mission is a JAXA ambitious mission to return samples from Phobos or Deimos (Mars moons) foreseen for a launch in 2024. Accompanying the main probe, a rover issued from a CNES/DLR/JAXA cooperation aims at exploring in-situ the small body. The developed nano rover will communicate through the probe via an intersatellite link based on the demonstrator initiated by CNES and Syrlinks. The communication will be established on S-band in full-duplex at a rate between 128 kb/s and 512 kb/s for the telemetry link depending on the distance between both units. This paper will discuss the proposed RF architecture and its expected performances according to the constraints of an asteroid touchdown. The further adaptations required for the current demonstrator to be accommodated on the MMX mission will be also presented.

Recently, a novel X-band multi-filar helix downlink antenna has been developed at RUAG Space. The antenna has been brought to an EQM status within an ESA GSTP program, and flight models are currently manufactured and tested for the MetOp SG satellites, as well as for several US missions. The antenna achieves a peak gain of around 6.5 dBi at EOC and an XPD better than 18 dB, which is superior to much larger aperture type antennas. In another recent ESA study (X-Band TT&C and K-Band downlink antennas for future LEO Missions) X-band TT&C antennas as well as Ka-Band downlink antennas have been designed using the knowledge from the above mentioned multi-filar helix design.

The X-Band TT&C antenna developed is a compact and low mass dual band design for 7.19-7.25 GHz (RX band) and 8.025- 8.400 GHz (TX Band) operation. It thus has a wider transmit frequency band than normally used. It has a hemispherical coverage with an EOC gain of better than -2 dBi to -1 dBi depending frequency. The antenna is fed through a conventional strip-line network to keep the height low and no protrusion inside the spacecraft needed. This antenna is now being manufactured as an EM activity in an add-on to the original study. For high power applications a waveguide fed antenna ca be envisaged.

The machining of the multi-filar helix is challenging, as the cross-section and the required tolerances are quite small. Hitherto, conventional CNC machining has offered a satisfactory yield. As the RF performance is excellent for the X-band antennas in the ESA GSTP program, it is tempting to scale to even higher frequencies. Recently, development was started with ESA/EOPP funding for a Ka-band (26 GHz) beacon and data downlink antenna for LEO earth observation missions. This antenna is one of the alternatives that were in the trade-off for Ka-band antennas in the study for X-Band TT&C and K-Band Downlink Antennas for Future LEO Missions. The frequency scaling makes the antenna very small; including radome and waveguide interface the total height is 76 mm, the interface diameter 50 mm, and the mass less than 130 g. The multi-filar helix radiator per se is only 44 mm tall, and the diameter is less than 2 mm. With such small dimensions, the machining now becomes very challenging. However a prototype of this antenna has been conventional manufactured with very good results. We have also looked in to the possibility to use additive layer manufacturing for the antenna.

The paper will describe the design considerations and results, as well as the measured performance of the above mentioned antennas.

Figure 1 The X-band antenna (waveguide fed and strip-line fed) and the predicted antenna patterns for RX and TX

Figure 2 The Ka-band multi-filar helix beacon / downlink antenna and the measured antenna pattern

The main technical objectives of the ESA financed activity currently underway at Thales Alenia Space Italia are the design, development of a breadboard of an integrated Payload Data Transmitter (PDT) and TT&C equipment and its validation. To this purpose, a comprehensive end-to-end system analysis has been performed first. In accordance to the unit-level requirements and the trade-offs results, the architectural design, applicable to the flight model as well, has been addressed. The identified architecture is able to provide the following main capabilities: a) to manage uplink signals in the 7190-7250 MHz band (telecommand) and downlink signals in the 8025-8400 MHz band (both housekeeping TM and P/L data TM); b) to operate when required in “transponder mode”, implementing all standard TT&C functionalities including coherent mode and ranging capabilities in order to support LEOP or S/C navigation as necessary; c) to implement during nominal operation the “PDT mode” with TX configured to provide high rate downlink (for HK and P/L TM) and RX active for telecommand reception.
The paper will describe major achievements, key technologies and specific issues of the future integrated communication unit (ICU), integrating both the X-Band transponder and the high data rate payload data transmitter functions in a single very compact equipment.
The ICU under development in TAS-in-Italy is based on new design concepts as well as disruptive technologies aiming to face the emerging so called “NewSpace” market. Leveraging on the many years of experiences on transponder line (well consolidated DSP building blocks are used) and developing new and very attractive architecture approach (direct synthesis as opposed to traditional conversion approaches) the paper will show how a very lightweight equipment with reduced components can be conceived.
The paper will provide equipment architecture description highlighting on the key concepts and main components. Then the main expected performances will be discussed. A section will be devoted to the component quality level assessing the main assumption along with new qualification approach. As far as technology is concerned, the RF-on-PCB will be introduced as a key cornerstone to achieve driver requirements as required by constellation market, e.g., low cost, short lead time and high production rate.