|Submitter:||Wim van Cappellen for the APERTIF team|
|Description:|| Over the last couple of years, APERTIF has been demonstrating the feasibility of Phased Array Feeds using a prototype system in one of the WSRT dishes. In parallel, hardware and firmware was developed for the final APERTIF system. This final system is now approaching completion. On 18 April 2013, two entire APERTIF signal paths based on the new subsystems were integrated and successfully tested for the first time. |
The left image shows the demonstrator setup: A test-tone was inserted into the Low Noise Amplifier (LNA) that amplifies and filters the signal. Next, the signal enters the Down Conversion Unit (DCU) in which the signal is converted to baseband. The baseband signal goes through the Gaincard to the ADU board where the signal is digitized. Finally, the digitized signal is sent to the UniBoard-based digital beamformer for further processing. The right image shows the resulting power spectrum, and indeed the test-tone appears at the expected position (which obviously triggered a tremendous wave of excitement across the entire lab).
This result is a major step in the integration of APERTIF. It demonstrates that the subsystems do not bite each other, but collaborate as a real system. Also, a new phase of system integration tests can now start to further characterize and debug the system.