European Space Agency

ELSA+ Enhanced active Rx antenna system ELSA (ELectronically Steerable Antenna)+: Enhanced active Rx antenna system


Based on the heritage of ELSA antenna developed under the frame of ESA AG1, an enhanced system “ELSA+” has been demanded by the customers including enhanced performances. The evolution deal with the improvement from single to dual polarization, increased band from 250 MHz to 2050 MHz, inclusion of emitter Geolocation and Beam Hopping.

The activity objectives included the development and prototyping of the subassemblies considered critical, and the system level analysis based on the developed units, accommodation and performances.

The specific activities carried out under this ARTES 5.2 ESA contract are:

  • System level analysis and sizing of the units to fulfill the requirements of both functionalities: Rx Antenna and Geolocation system
  • Redesign of the radiator
  • Redesign of MMIC LNAs and Filters
  • Accommodation study to fit the double of the electronics in the same room
  • Revisiting the concept of the antenna central electronic (ICU/PSU) to give service to twice the number of elements and new functionalities
  • Design of the Down conversion new module for the Geolocation functionality,
  • Definition of the ADC module and the Frequency synthesizer


The customer expectations identify needs and associated challenges in the design and technologies versus the heritage:

  • The bandwidth required covers the full FSS band, more than 2 GHz about 8 times the reference heritage, meaning a strong evolution in all the RF components in the path, the Passive beam-forming network (BFN) elements, the active control module (MCCM) and the radiating element.
  • Beam bandwidth required is 500 MHz (target 1GHz), in front of the heritage 40 MHz, between 12 and 24 times larger, meaning a challenge in the design and processes associated with units in the RF path, to minimize and control de dispersion of the main parameters (Phase, amplitude and delays) both in design and manufacturing process: MMICs, alumina’s, PCBs, ceramic packages and wire bonding assemblies
  • Dual polarization operation imposes two challenges: twice the electronics and number of beams need to be accommodated, and radiating element dual pol operation, where a drastic evolution from planar patch technology to horn is considered.
  • Geolocation is a fully new functionality not present in heritage that requires the implementation of down conversion modules (in hybrid technology), Ku-band local oscillator with coherent distribution, and ADC conversion, handling significant amount of information.


The dual pol and the extended band objective of the development are motivated by the huge increase in capacity that can be offered to the customer. Dual pol means a x2 factor in the capacity, beam bandwidth x24 factor, operating bandwidth a 8x factor, and on top of that the capability of the frequency reuse in the 8 beams, with 2x or 3x factors. The increase number of beams from 4 to 8 allows to define x2 number of scenarios and customers

Geolocation allows to monitor the position, power and polarisation of interfering emitters on ground with a granularity below 2 MHz within the FSS band. Knowing the position of possible non authorised emitters or intentional jammers allows the operator to take corrective actions, such as pointing, shaping or nulling (feature already available in the product) in the affected direction.

All this features allow offering the customer more capacity, flexibility and interference immune product, currently not available in the European market.


An on-board unit which provides the multibeam, enhanced with dual-polarization and extended bandwidth capability for the required G/T, with the pointing, nulling and shaping capability, in one hand and will perform interferences detection in the other hand.

An on-ground unit to control the antenna system and also to process interference information in order to mitigate them properly, and to fully exploit the system features.


ELSA+ system architecture

The on board HW architecture has been designed to comply with the new market needs. At the same time, the modularity approach gives flexibility to adapt to other requirements by means of growing up the number of elements or redesigning the affected units. 

System Architecture

The architecture and main assemblies developed in the project correspond to the on-board unit including: Rx antenna • Radaiting chains (raditor+filter+OMT) provide RF signals which are connected to the input of the MCCMs. • Each MCCM-Rx manages 4H or 4V signals. The signal coming from the radiating elements is amplified in this unit, prior to be divided by 4 in order to get the contribution for the 4H or 4V beams. • After the MCCMs, the signal combination is done, 4:1, is implemented into the MCCM subassembly, and the next level of combination 21:1 is implemented by means of 6 combiners of 5:1. Geoloc • Sensors (raditor+filter+transition) of the incident signals and input filters reject signals outside interest-band • Inside MCCM-GEO the signals are down-converted to IF in order to operate in the input bandwidth of the ADC • Afterwards, inside the IFSAM module, signals are conditioned to the ADC • ADC digitizes the signal of ach sensor.


The activity allows risks mitigation on the development for a commercial telecom project, and is the first step of a global plan defined in 3 steps:

  • Step I (this ARTES 5.2) covering the work up to the prototyping of the antenna subassemblies identified as critical for the enhanced antenna system, and architecture and system definition
  • Step II (ARTES 3-4) covering the detailed design, manufacturing and qualification phase (out of scope of this activity) of the antenna system subassemblies.
  • Step III (PFM) covering the detailed design of the PFM, the production of the FM subassemblies followed by the integration and test campaign.

Total duration of the ARTES 5.2 was targeted in twelve months, with the following milestones

  • Kick-off , October 2014
    • Baseline Design Review, December 2014, to review the units sizing, assess de accommodation of the antenna and the preliminary performances
  • Mid Term Review, April 2014, to review the design of the identified S/A, and approval to proceed with the BB implementation and the system design and performances based on the S/A preliminary analysis

Final review, September 2015,  to review prototype performances, update performances prediction  and S/A sizing, confirm feasibility of the system design based on prototyping of the critical S/A.

Current status


All the goals of the projects have been successfully reached on time

Status date

Monday, July 2, 2018 - 10:04