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© Vereese van Tonder
A monotonic plane wave was synthesized by using the wave generators in the 4 back node fpga's on the UniBoard. Altogether 16 signals were generated, each with a progressive phase shift in order to approximate a plane wave arriving at 16 antenna's. The signals were then channelized by a polyphase filter bank after which the subband of interest was mapped to all 4 of the front node fpga's. The conjugate field matching weights for 16 signals in 180 (-90 deg to 90 deg) different directions were calculated and applied. After the complex weight multiplication the 16 signals were summed and integrated for 1 second.
Various experiments were conducted of which two are illustrated in the image above. One experiment entailed synthesizing a source with a DOA of 45 deg. It was expected and verified that the signals should add up constructively in this direction and destructively in the other directions, please see figure 1 in the above image. Further, the spacing between the elements were varied in terms of wavelength. This was done in order to verify that the main beam of the array becomes narrower for an overall length increase, please see figure 2 in the above image.
Vareese is from the group of David Davidson at Stellenbosch University in South Africa. She has spent the last 4 weeks at ASTRON as part of the MIDPREP program.
