Mega Channel Spectrometer

Status: Unfinished

Introduction

When implementing spectrometers in ROACH2 hardware with over 100,000 channels, using standard biplex FFT architecture becomes unfeasible due to the large amount of computational resources required. An alternative structure exists that make possible the implementation of over a million channel spectrometer in ROACH2, which consist in cascading two FFT blocks together (the output of one FFT is the input of the other). Specialized blocks called 'corner turner' are use between the FFTs with the purpose of input the data of the last FFT in the correct order (mathematically, they perform a matrix transposition). The disadvantages of this method are that memory requirements increase, and channel leakage is present in non-consecutive channels (different from the standard leakage from FFT blocks).