Wide Band Single Pixel Feeds

WideBandSinglePixelFeeds_blue

The WBSPF consortium had a productive period with advancement of the design of the Band A feed, successful tests of the Band B feed and good progress with the design of the Receiver and Cryostat.

The WBSPF Board meeting was held on 12th of May. Main points of discussion were the time plan for achieving PDR by the end of 2017 and potential continuation of the WBSPF work during 2018. The advancement in all work packages is quite good and the plan is to prepare for PDR in November 2017. There are delays with finalising the concept for the WBSPF cryostat but it is believed that the work will advance and in few months bring the design at PDR level. All consortium partners are positive for continuation of the work in 2018. Details about that were discussed with SKAO representatives during the AIP meeting and the Engineering meeting in June. The plan is to form new AIP consortium that will bring together work on advanced technologies for single pixel feeds and receivers and include universities and companies working with design and prototype of feeds, LNAs, receives and cooling technologies. This proposal will be submitted to the SKAO Board for approval.

There were also number of interesting discussions about the future of the WBSPF consortium during the AIP meeting in Dwingeloo 8-9th of June and the 5th Engineering meeting, which was held in Rotterdam 12-15 of June.

Feed and LNAs for Band A

Lead Institute: JLRAT

Lead engineer: Niu Chuanfeng

The concept for the design of Band A feed was changed from using exponential profile to utilising spline profile. Simulated performance is very good. Significant work was done co-optimising the feed together with choke structure around the cryostat to improve the efficiency (Figure 1, left). Simulated Aeff/Tsys of the feed in cryostat without chokes is shown in Figure 1 together with Aeff/Tsys for cryostat with the choke structure. As seen from the figure, the improvement is significant.

Figure 1: EM model of the Band A feed with choke shaped cryostat (left) and simulated Aeff/Tsys (right)

Feed for Band B feed and LNAs

The Band B feed and the LNAs from Low Noise Factory were integrated in test cryostat at Onsala Space Observatory, Figure 2. Up to date three cryogenic tests using the on-sky measurement facility were done. The measured Y-factor is around 12 – 15 K over nearly 80 % of the band (Figure 3). There are still problems with sharp peak at around 12 GHz that is most likely due to mechanical problem in one of the polarisations.

Figure 2: The Band B feed and Band B LNAs integrated in the test cryostat at OSO (left). On-sky Y-factor measurement in progress (right).

Figure 3: Measured Y-factor of the Band B feed and LNA.

Receiver

The work with the analogue part of the receiver is progressing. The layouts of the filters and conditioning modules is ready.

Time plan

The current time plan until the PDR is as follows:

  • Manufacture and test Band A feed – August 2017
  • Manufacture WBSPF cryostat and do thermal loading tests – September 2017
  • Preparation of WP description for the new AIP consortium, successor of WBSPF – October 2017
  • PDR in December 2017

Report provided by the WBSPF consortium