Estimating and calibrating the response of multiple wideband digital radio frequency memories in a hardware-in-the-loop system using shuffled frog leaping algorithm
The frequency response of digital radio frequency memory (DRFM) kernel varies over frequency in its passband. This in turn causes distortion to the regenerated radar signal. For wide band DRFMs, this distortion can become more severe and is thus a problem to be solved. For a wide band DRFM kernel, the total magnitude variation in the passband can reach 8 dB. A novel method to estimate and compensate for the distortion is presented in this study. Data recorded during loop-back testing is used to estimate the response of the DRFM kernel. A digital finite impulse response filter with complex coefficients is then designed and optimised to compensate for this distortion using the shuffled frog leaping algorithm (SFLA), which is a specific implementation of the memetic algorithm. Simulation results demonstrate that, compared with inverse Fourier-based techniques and genetic algorithm (GA), the SFLA shows an improvement of 0.5 dB in magnitude ripple and 5.7° in phase ripple. The SFLA technique produces usable solutions for length 17 filters, whereas the GA requires filter lengths of more than 30 to reach the same performance. The shorter filters reduce the delay through the DRFM kernel, which is an important design specification in such systems.