An AWF digital spectrometer for a radio telescope

A radio telescope analyzes radio frequency (RF) signal from celestial objects. It consists of an antenna, a receiver, and a spectrometer. The spectrometer converts signal in the time domain into one in the frequency domain by an FFT operation. In the conventional spectrometer, first, it multiples the window coefficient by the received signal. Second, it performs the FFT operation. Third, it converts the signal into the magnitude of the complex number. Finally, to reduce the noise, it accumulates obtained power spectrum. We call this a WFA spectrometer. Since the analog-to-digital converter (ADC) is faster than an FPGA, a parallel FFT computation is desired. However, since the number of on-chip memories for the FFT becomes the bottleneck, the conventional WFA spectrometer could not realize the wide-band and high-resolution. This paper proposes an AWF spectrometer which replaces the order of operations. Since the AWF spectrometer reduces the parallelism of the FFT, it is smaller than the conventional WFA spectrometer. Also, the AWF spectrometer can use a sequential FFT rather than the parallel one. It can be realized by an off-chip memory. Thus, it reduces the number of on-chip memories. Experimental results show that the proposed AWF spectrometer outperforms conventional WFA spectrometers.