Photo-Digital Channelizer for Flexible Digital High Throughput Satellites

Project Information

PhLEXSAT

Grant agreement ID: 101004253

DOI

10.3030/101004253

Project closed

EC signature date 27 October 2020

Start date 1 November 2020

End date 30 September 2023

Funded under

• INDUSTRIAL LEADERSHIP - Leadership in enabling and industrial technologies – Space

Total cost

€ 2 960 024,25

EU contribution

€ 2 960 024,25

Coordinated by

DAS PHOTONICS SL
Spain

Periodic Reporting for period 2 - PhLEXSAT (Photo-Digital Channelizer for Flexible Digital High Throughput Satellites)

Reporting period: 2021-11-01 to 2023-09-30

Summary of the context and overall objectives of the project

Global demand of broadband communication services is growing year by year with a forecasted double-digit growth in this decade. Providing worldwide broadband internet by means of space-based communications has spurred the need of new satellite communication technologies that are able to provide high capacity and flexibility to satisfy every user on the network at the minimum in-orbit cost per Gbps. High Throughput Satellite (HTS) systems provide the optimally scalable solution to a wide range of bandwidth-intensive applications by combining regional and global beams for broadcast/multicast applications, serving low-density traffic zones, and spanning dense traffic zones with narrow spot beams for high-capacity broadband communications.
HTS systems are expected to supply more than 1 Tbps of capacity. To address this traffic need, the challenge is to minimize the hardware complexity in the satellite communication payload to fit the size, weight and power consumption (SWaP) within the limits of the platforms and, at the same time, to maximize the flexibility in the use of on-board resources. Such is only achievable with a reconfigurable digital signal processing (DSP) on-board.
Achieving more flexibility through DSP payloads, requires the implementation of ADCs (Analog to Digital Converter) and DACs (Digital to Analog Converter) in the payload core. This kind of satellites are known as Digital HTS, the other alternative to Analogue HTS. However, the current electronic ADC and DACs are limited in sampling frequency, frequency of operation and power consumption.
The use of the available bandwidth in V/W band is indispensable to feed the tremendous capacity of the forthcoming Tbps satellites. Photonic and V/W technologies are key enablers to overcome the challenges required to provide the capacity and flexibility to dynamically manage future Tbps communication satellites. The ability of Photonics to handle high data rates and high frequencies and its easy reconfigurability as well as its low SWaP is critical in this scenario, where currently purely RF technologies are limited in SWaP and performance.
PhLEXSAT took the next step in achieving the paradigm of the full-flexible Tbps-class payload by synergically mixing of V/W bands, photonics and DSP within the new concept of photo-digital channelizer. PhLEXSAT designed, fabricated and tested several modules and units to a Technology Readiness Level (TRL) of 5: 1) Photonic clock for precise sampling, 2) Photonic ADC and DAC for V/W band operation, 3) on-board DSP, 4) Miniaturization enabled by integrating Mach-Zehnder Interferometer (MZI) modulator Photonic Integrated Circuit (PIC) and high-linear photodiode (HL-PD) PIC in the Photonic ADC and Photonic DAC modules. PhLEXSAT integrated and demonstrated such building blocks in a test bed proving the suitability of the channelizer for Ka/Q/V/W band operation.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Two main application scenarios were identified for flexible satellite communication payloads: Very HTS (VHTS) and Software defined payload satellite, using active antennas. Selected target was a photonic payload operating at extremely high frequency (W band) and with high capacity (1 Tbps) and fulfill the requirements for the VHTS scenario.
The PhLEXSAT payload concept was defined incorporating advanced broadband photonic ADC and photonic DAC with DSP with high degree of miniaturization and power-consumption efficiency.
According with the above system requirements, the specifications were defined and the design was performed of the different units integrating the PhLEXSAT demonstrator.
A test plan was generated at module and unit level, determining the type and conditions of the assessment tests for the space environment up to TRL5.
One MZI PIC capable to operate in DC-86 GHz and four HL-PD array PIC with linearity optimized in DC-6, 17-20, 37.5-42.5 and 71-76 GHz, respectively, were designed, manufactured and tested. Furthermore, two packaged MZI PIC versions were manufactured, one DC-86 GHz for the Photonic ADC, the second one DC-6 GHz with additional RF amplifier for the Photonic DAC. Four packaged HL-PD PICs versions were manufactured, three 17-20, 37.5-42.5 and 71-76 GHz for the Photonic DAC, another DC-6 GHz with additional RF amplifier for the Photonic ADC.
One Photonic ADC-PD unit and two Photonic DAC-PD units were manufactured and tested, integrating the corresponding HL-PD modules.
One Photonic ADC-MZI unit and one Photonic DAC-MZI unit were manufactured and tested, integrating Commercial off-the-shelf (COTS) MZI. The units are ready to directly replace the COTS MZI by the PhLEXSAT MZI modules.
Photonic Clock unit was manufactured and tested based on a mode-locked laser at 2.6 GHz, optical amplification and splitting to provide a clock to the MZI units for photonic sampling.
All units were integrated with electronics and control firmware as well as mechanical interface.
DSP modules were developed and tested on FPGA hardware, including ADC and DAC interfaces, linearisation, channelization and multiplexing. Embedded and user interface software were developed and tested to control the PhLEXSAT demonstrator.
PhLEXSAT demonstrator was integrated including the photonic units with control software and power supply. Test results showed the correct behavior of the RF to optical back to RF conversion. The achievements are summarized below:
Photonic ADC in the Ka band (27.5-30 GHz), although the same concept can be applied to V/W bands.
Photonic DAC in the Q (37.5-42.5 GHz) and V (75-76 GHz) bands, although the same concept can be applied to the Ka band.
Photonic ADC (27.5-28.75 GHz) connected to Photonic DAC (41.25-42.5 GHz).

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The development of MZI and HL-PD devices that managed to increase the frequency of operation and hybrid module integration compatibility represents a significant improvement in the state-of-the-art of these devices, offering potential commercial benefits.
FP7 PHASER project demonstrated that significant progress beyond the state-of-the-art in ADC technology for Satcom applications can be achieved by employing photonic ADC technology. PhLEXSAT demonstrated that an end-to-end software-defined payload with an unprecedent level of miniaturization enabled by PICs, with SWaP reduction and improved frequency of operation respect to traditional RF implementations, is possible to be achieved to address >1 Tbps.
The impact of SATCOM in the EU society is huge, through jobs creation and by impacting in many ways in the citizens’ life, by increasing the connectivity to high-speed Internet services everywhere, which can only be provided by this technology.
PhLEXSAT contributes to this scenario by providing a very flexible high-performance digital payload that will allow the optimisation of operations, thanks to the technological features and SWaP reduction, which has a direct impact to SATCOM satellites usability and duration.

Block diagram of a photonics-based digital communication payload in the context of a VHTS mission.

Picture of the PhLEXSAT Demonstrator