Multiplier and Accumulator

The Multiplier and Accumulator (MAC) accepts data from the FFT in order to produce all possible self and cross products, ((30 x (30 +1)) / 2 = 465). Each MAC has 256 accumulators, hence it can produce either 256 complex numbers for one polarization or 128 complex numbers for two polarizations using the same unit by averaging the two adjacent channels of FFT output from the same polarization, and accumulate for the one STA (Short Term Accumulation) cycle of 128 $ms$ duration. Since MAC (Multiplier and Accumulator) section can be reconfigured to give all four stokes parameters for any one of the two sidebands, there are 3 modes of operation of the correlator.

• Non-polar mode : To measure only one of the two polarization RR or LL with the full band information.

• Indian-Polar mode : For the measurement of the total intensity stoke I on non polarized source. The measurement of both the polarization RR & LL per sideband is possible, but gives 128 channels of the same polarization giving limited resolution. This is mainly used for continuum observations

• Polar mode : To measure all the four stokes parameters using either upper or lower sideband which passes through both sidebands of the correlator. In this mode each MAC unit gives a pair of RR, LL or LL, LR having 128 spectral channels for each stoke.