| 20th of December 2019 |
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| ASKAP signal processing |
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The ASKAP Phased Array Feed (PAF) is a 188-port chequerboard receive-only array.
The signal processing chain comprises an analog front-end and digital back-end.
The analog part of the system primarily resides at the focus of the antenna, whereas
all digital signal processing (including the analog-to-digital conversion) resides
in a shielded central site building to protect again Radio Frequency (RF) interference.
RF-over-fibre links the PAF electronics with the central site digital signal
processing hardware that may be located up to 7km away.
A digital signal processing board called the Dragonfly has been developed for ASKAP. Each Dragonfly card processes 16 PAF channels and contains the ADCs and coarse filterbank. The ADCs digitise the PAF ports at over 1200 mega-samples per second and firmware running the Field Programmable Gate Array (FPGA) processes the input bandwidth into coarse oversampled 1MHz channels. From the output of the Dragonfly boards all signal processing is purely digital and is handled by the Redback boards, which are capable of both beamforming and correlation functions. The image above shows the layout of the multi-layer Dragonfly board. |