Implementation considerations for SDF technique

The Tasman International Geospace Environment Radars (TIGER) form part of an international network of similar HF radars called Super Dual Auroral Radar Network (SuperDARN) which explore the impact of solar disturbances on Earth by monitoring the location and velocity of plasma of plasma irregularities and related phenomena occurring in the ionosphere. These radars utilise an Auto Correlation Function (ACF) to measure the changing phase of the ACF between lag times to determine the Doppler frequency and thus the target velocity. With the development of TIGER-3, an all digital radar platform, a novel method of determining target velocities has been proposed. In the proposed method, a comparison of the transmit and receive signal magnitude spectrums is performed to determine the Spectrum Difference Function (SDF). It has been shown that the gradient of SDF in the vicinity of the carrier frequency is proportional to the target Doppler shift. In this paper we consider the constraints of hardware processing on the implementation of the technique and suggest an alternate architecture for the TIGER-3 radar that will allow a dramatic reduction in computational complexity to allow the real-time determination of velocity in conjunction with the normal operation of the receivers. The proposed technique moves the processing from the RF frequency band to a low frequency IF band to reduce the computational length of the Fast Fourier transform (FFT) without compromising the validity of the technique.