Dear CASPER List, I am a postdoc working with Jonathan Weintroub and am new to CASPER.
We are working on bitcode for ROACH2 to reformat the data product at the Submillimeter Array in real time so that it can be used directly in VLBI observations as part of the Event Horizon Telescope. As part of that reformatting, we wish to convert the demultiplexed frequency domain streams of the SWARM F-engine (https://arxiv.org/abs/1611.02596 <https://arxiv.org/abs/1611.02596>) to time domain streams. In other words, we want to take the inverse FFT of demultiplexed frequency-domain samples. Ordinarily, we would would achieve the inverse fft using the CASPER complex_conj and fft blocks in series; however, the SWARM frequency domain output comes from an fft_wideband_real block, which discards the negative frequencies, so direct application of complex_conj+fft will not work. One approach to inverting the data would be to buffer and copy the positive (complex) frequencies emitted by fft_wideband_real, assemble a stream of positive and (mirrored) negative frequencies, then feed the complete spectrum into complex_conj+fft blocks. Jonathan suggested I check with the CASPER community to see, is there a more efficient way of performing our inverse FFT? Is there a way to take advantage of the knowledge that the output from our iFFT block should be real-valued? We appreciate any guidance the mailing list can provide. Sincerely, Alex Raymond -- You received this message because you are subscribed to the Google Groups "[email protected]" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected].
