Photonic technologies are recognised as key enablers to satisfy the flexibility, size, weight and power (SWaP) and performance requirements of next generation earth observation (EO) missions. The ability of photonics to handle high data rates and high frequencies and its easy reconfigurability is critical in this scenario, where current purely RF technologies are limited in SWaP and performance. However, the use of photonics is currently restricted to a few demonstrations in non-critical equipment, due to their perceived immaturity compared to RF.
RETINA will develop several key RF-photonic building blocks to TRL5-6, designing, fabricating and testing 1) multi-beam TTD phased array antennas for X band operation, 2) a photonic integrated beamforming network, 3) novel configuration active X-band antenna array and 4) miniaturized space-grade components and subsystems. Miniaturization will be achieved by integrating lasers and external modulators with electronics in the transmission side, integrating photodiodes, amplifiers and electronics at the receiver side and by fabricating a PIC (Photonic Integrated Circuit) beamformer. RETINA will integrate and demonstrate such building blocks in a test bed proving the suitability of the proposed architecture in a SAR (Synthetic Aperture Radar) scenario for 64 beams, demonstrating a flexible SAR payload for missions requiring flexible frequency plans and channelization and dynamic coverage operation. RETINA consortium comprises the multidisciplinary skills needed to achieve its objectives and fully exploit its results, with partners representing the whole value chain, from space-grade hardware developers to EO satellite integrators and by academia partners developing key technologies and fostering technology transfer.
RETINA success will contribute to enhance EU competitiveness and non-dependence by developing critical technologies for the EU satellite industry that can be transferred to non-space sectors.
CoordinatedDAS Photonics (Spain)
EU ContributionEUR 2.991.088.25
Call for proposalH2020-SPACE-2018-2020
Term of completion2018-11-01 to 2022-01-31
The RETINA consortium brings together a wealth of expertise and resources within the areas of: photonic components and modules, PIC fabrication, antennas and RF components fabrication, space grade technologies, and satellite integrators. The presence of main actors in the whole value chain demonstrates the critical mass of complimentary resources that will enable the RETINA project to achieve its targeted industrial, scientific and societal breakthroughs and commercial success.
DAS Photonics (Spain)http://www.dasphotonics.com/en
AMO GmbH (Germany)http://www.amo.de
United Kingdom Research and Innovation (UK)http://www.stfc.ac.uk/ralspace
Universitat Politècnica de València (Spain)http://www.ntc.upv.es
The main objective of RETINA project is the development of an advanced reconfigurable multi-beam photonic beamformer with centralised processing. In particular, a very innovative SAR approach based on photonic technologies whose main impact is to increase the EU competitiveness in payloads for advanced SAR missions by bringing to TRL5-6 previous developments in photonic enabled payloads for SAR applications, starting from the previous FP7 project GAIA, solving the limitations found in terms in power consumption and switching speed and incorporating new features such as centralised signal processing and a truly broadband frequency operation approach thanks to the multi-beam TTD reconfigurable beamforming architecture.
The RETINA specific objectives are summarized as follows:
The development of compact, suitable for space, broadband frequency operation multi-beam photonic beamformer with centralized processing for Next Generation SAR solving the limitations found in terms in power consumption and switching speed.
Development of a multi carrier laser with space-grade specifications reducing the power consumption associated to the thermal cooling by a factor of 3 per laser (laser thermo-cooling has resulted to be one of the major drivers in the power consumption of the optical payloads, according with the team experience).
Optimisation of a Photonic Integrated Circuits (PIC) in silicon-nitride technology implementing a designs of true-time delay beamforming networks, suitable to be used in broadband applications without beamsquint degradation, implementing a frequency-agnostic switchable True-Time delay beamforming matrix of 64 x 64 ports specifically designed to work in 4x configuration to achieve a 256 x 256 beamformer (256 spot beams, 256 antenna elements) with 4 PICs in a phased-array antenna.
Consolidate the Array Antenna Element design at X band suitable to be the basic building block of a large X phased-array antenna and integrating the antenna element, the amplification section and the opto/electronic converters.
Design and manufacturing of a TRL6 small footprint broadband beam optical transmitter module up to Ka-band including RF and optical amplification and modulation, reducing the size and footprint of the present GAIA design by a factor of 3.
Design and manufacturing of a TRL6 compact antenna optical receiver in X-band with a co-package of amplifiers, optical receiver and antenna element, reducing the size and footprint of the present solutions by a factor of 4.
Design, manufacturing and supply of photoreceivers in the X band with optimized footprint and self-stabilized gain vs temperature. The photodiode within the photoreceiver will cover up to Ka-band to address the objective of broadband frequency operation. Integration and test of preamplifiers working up to 30 GHz with this broadband photodiode will also be achieved.
To demonstrate the flexibility of beam-shaping and beam-switching in a PIC-based optical beamformer by the combination of a fixed beamformer network generating massive orthogonal beams with a co-integrated switching network to perform beam-shaping by multi-orthogonal beam synthesis. The level of flexibility should be comparable with a traditional beamforming network based on phase and amplitude control with an order of magnitude less complexity.
The proposed antenna concept consists of a Direct Radiating Array (DRA) Antenna System composed by a number of antenna elements that are all fed by the same signals, but with differences in delay and amplitude. The delay and amplitude control is performed by a dividing and delaying structure named beamforming network.
To implement a DRA antenna system with hundreds of elements, true-time delay (TTD) performance and dozens of simultaneous beams is not possible with the present RF technology… but is what the RETINA team wants to do by using integrated photonic technology. The optical beamforming network with TTD characteristic will be constructed by aggregating elementary Photonic Integrated Circuits (PIC)-based 8×8 beamforming networks with switching capabilities. The PIC component will control the delay of up to eight signals simultaneously and to route them and combine to a specific beamforming port.
A 3D aggregation approach will be performed to construct the complete SAR beamformer able to steer the beam in any direction of the space (within the coverage limits). This concept is very versatile since it can work as a multi-coverage antenna with beam-switching characteristics (nominal configuration) or as a flexible multi-beam system with flexible coverage if orthogonal beams are generated, which occurs when the direction of maximum radiation of one beam corresponds with a radiation minimum of the rest of the beams. In RETINA these kind of beams with TTD features in the fixed beamformer section of the unitary PIC will be constructed.
The combination of multiple orthogonal beams with proper phase/delay adjustment could synthesize any radiation patterns (beam coverage). This technique is known as Woodward Synthesis. The proper configuration of the switching matrix of the PIC would enable this synthesis by combining with a wavelength division multiplexing scheme in which the signals to be radiated by each orthogonal beam is modulated in an optical carrier with different central wavelength.
This fact results in that the complexity of the laser generation (theoretically 64 different lasers for 64 beams) could be high, and the associated mass and power consumption, especially considering that stable, WDM lasers needs to be thermally stabilized to operate, which could be the major driver of the power consumption of the system. To overcome this limitation, a multi-carrier laser system will be developed based on a mode-locked laser with mode filtering will also be developed in RETINA.
On the antenna optical receiver side, the elementary antenna will be co-packaged with a receiver module composed by photodetector up to 30 GHz and RF amplification and switching. This array antenna element will have optical interfaces to connect the optical fibres communicating the beamformer network and the antennas.
RETINA main achievements have been:
- Design, fabrication and test of a 1×8 sub-array EQM model and a 4×8 BB model at X-band, achieving TRL7 and TRL 6, respectively.
- Design, fabrication, packaging and test of a TRL4 X-band photoreceiver with optimized footprint and self-stabilized gain vs temperature.
- Design, fabrication, packaging and test of a Beamforming Network PIC based on Si3N4 (ultra-low-loss optical waveguides, below 0.1 dB/cm) which is capable to control 8 beams, providing 64 true-time delays (beam squint free), i.e, 8 pointing angles form 20º to -20º. The PIC includes a calibration input for system phase calibration and low loss grating couplers.
- Design and validation of an efficient fibre array-to-chip assembly process with a high number of input/output ports.
- Design and manufacturing of a TRL6 small footprint broadband beam optical transmitter (BOT) module up to Ka-band including RF and optical amplification and modulation.
- Demonstration at bread-board level of a multi carrier laser based on spectral slicing of a mode-locked laser. Estimated reduction in power consumption by a factor of 3.3 comparing with stand-alone BOTs with DFB CW lasers.
- Design and manufacturing of a TRL4 compact antenna optical receiver in X-band with a co-package of amplifiers, optical receiver and antenna arrays elements.
- Development and functional validation of a demonstrator representative of a full-scale system confirming the multibeam capability and the suitability of the TTD OBFN for SAR Applications.
- A. Brimont, D. Zurita, V. C. Duarte, T. Mengual, B. Chmielak, S. Suckow, A. Giesecke, M. A. Piqueras, P. Sanchis, “Optical fiber-to-chip assembly process for ultra-low loss photonic devices based on silicon nitride for space applications”, 22th European Conference on Integrated Optics, June 23-25, Paris (France), 2020.
- T. Mengual, V. C. Duarte, V. Polo, M. A. Piqueras, P. Sanchis, A. Brimont, D. Zurita, B. Chmielak, S. Suckow, A. Giesecke, E. Matarazzo, L. DiPalma, D. Maiarelli, H. Wang, P. G. Huggard, “Miniaturised photonic front-end for the next generation of space SAR applications,” Proc. SPIE 11852, International Conference on Space Optics — ICSO 2020, 1185255 (11 June 2021)
- Lo Forti, M. Scigliano, M. De Soricellis, T. Mengual, D. Moreno, P. Villalba, M.A. Piqueras, B. Chmielak, S. Suckow, H. Wang, P. Huggard, P. Sanchis,” Photonic Beamforming for EO and Telecom Applications”, Mediterranean Microwave Symposium, May 9-13, Pizzo Calabro (Italy), 2022.
- B.Chmielak, S. Suckow, J. Parra, V. C. Duarte, T. Mengual, M. A. Piqueras, A. L. Giesecke, M. C. Lemme, P. Sanchis, “High-efficiency grating coupler for ultra-low loss Si3N4 based platform”, Optics Letters, vol. 47, no. 10, 2022.
- Project announcement press release TEDAE Proespacio Magazine Number 41, January, 2019.
Dr. Miguel Angel Piqueras
DAS Photonics S.L.
Camino de Vera s/n, Acceso K, Edificio 8F, Planta 3
46022 Valencia, Spain