A Wide-Band FFT Polarimeter for Radio Astronomy Based on Commercial Hardware
Maik Wolleben; DRAO, Canada.
A new FPGA-based FFT polarimeter has been developed at DRAO. The polarimeter samples two input channels with 8-bit resolution and a sampling frequency of 1 GHz, providing 2048 channels over 500 MHz of bandwidth. The polarimeter is currently used on the DRAO 26-m single antenna telescope for an all-sky rotation measure survey in the frequency range 1300 to 1800 MHz. I will discuss the basic hardware design of the polarimeter as well as the software processing chain, with an emphasis on our experience regarding RFI detection and mitigation. The VHDL code for the FPGAs has been developed at DRAO, while the hardware is based on commercially available components. The polarimeter is designed to be portable, requiring a minimum of external connections: an ethernet connection for polarimeter control and data transfer, and TTL signals for switching external noise sources for gain and phase calibration. I will describe the interface between the polarimeter and the telescope, and will present wide-band polarization data taken in RFI polluted frequency bands.