ASKAP Smart Feeds
This project will develop the focal plane array (FPA) for ASKAP. This device provides the antenna with a wide field-of-view (FoV) by creating 30 separate (simultaneous) beams to give a FoV of 30 square degrees. Successive versions of FPAs will tested on the test-bed antenna at Parkes before the final design for ASKAP is selected.
The protype FPA being lowered into position on the Parkes testbed facility (July 2008). Photo credit: David McClenaghan
An additional goal of the project effort is to build the skills which will enable the development of improved smart feeds for more general use within radio astronomy: This may ultimately lead to operation at higher frequencies (10 GHz and above), development of designs where cryogenic cooling of the receivers improves the system temperature (Tsys), and also to improvement of system aspects such as use of beamformer weights to adaptively correct for reflector distortions and pointing.
The smart feed project will work closely with the ASKAP receiver project, but does not directly include this aspect in the project. It is anticipated that the LNA design requirements can be sufficiently decoupled from the smart feed electromagnetics.
The project activities include:
- Electromagnetic design and modelling
- Improved array designs and in particular, improved LNA coupling designs
- Modelling tool development including integration of commercial tools with locally developed tools
- Modelling of actual array to be prototyped including details of PCB and connector structures
- Array mechanical design
- Designs for low cost manufacture, eg PCB array structures which can be easily assembled
- Enclosure design - weight, strength, thermal, moisture ingress, etc
- Array system design
- Development of performance criteria and measures for improved array
- Beamformer optimisation and requirements
- Prototype manufacture and integration
- Array prototype manufacture
- Integration with receiver and optical fibre data transmission
- Testing on Parkes interferometer
- Interferometric measurement of element beams
- Demonstration of beamformed efficiency and system temperature
- Design modifications and re-test (if necessary)
- Manufacture FPAs for inital 6 and complete 30 antennas.
The targets are to attain:
- Efficiency after beamforming in the range 60-75%
- Tsys (after beamforming) of 50K
- FOV of 30 sq degrees at 1.8 GHz
- A frequency range of 700 MHz to 1.8 GHz with stretch target to extend to 2.5 GHz.