The Allen Telescope Array (ATA) located in Northern California is a radio telescope optimized for the Search for Extraterrestrial Intelligence (SETI). The instrument is composed of 42 directional randomly distributed antennas with a maximum baseline of 300 meters. The recently upgraded cryo-cooled log-periodic antenna feed (Antonio Feed) is sensitive to a wide range of frequencies, 0.9-12 GHz. The digital signal processing software is comprised of a real-time correlator and beamformer that can be utilized for SETI, fast radio burst, and other kinds of radio astronomy science.
The received RF signal from each antenna is transmitted to a central processing room using a fiber-optic cable and digitized using a real-valued ADC onboard a Xilinx RFSoC. The digitized data are pre-channelized, filtered, and streamed down the chain via a 100GbE network. This pre-channelization step is based on a polyphase filterbank to achieve an excellent level of spectral leakage suitable for mitigating unwanted electromagnetic interference. The output of the polyphase filterbank frontend, i.e. the pseudo-IQ samples, are then FFT'ed to achieve channelization.
Inverting the critically-sampled polyphase filterbank is a lossy operation. However, the digitally filtered pseudo-IQ data can be used to demodulate strong terrestrial signals, such as LTE downlinks. Converting the ATA data to pseudo-IQ allows most of the Open-Source science dataset generated by the ATA to be used by GNU Radio.
To make the conversion process easily accessible to the user, we developed a GNU Radio Out-of-Tree (OOT) module that reads a GUPPI file generated by the telescope pipeline and outputs a pseudo-IQ complex stream ready to be used with standard blocks.
In this talk, I will explain the Allen Telescope Array processing pipeline, demonstrate the conversion of a GUPPI file into pseudo-IQ using the GNU Radio Out-of-Tree block, and illustrate what is possible to do with such data inside the GNU Radio Companion.
|Talk Length||15 Minutes|