Modified Roll-off Filter with Optimized Impulse Response for Reducing PAPR of Transmitted Signal

Abstract

This paper discusses a modified roll-off filter that yields lower PAPR (peak-to-average power ratio) than that of the conventional roll-off filter. The modified filter has a roll-off function expressed in a sum of sinusoidal functions such as α1 sin(x) and α2 sin(3x). Since a different combination of the coefficients of the sinusoidal functions yields a different impulse response as a candidate while satisfying the Nyquist theorem under the constant bandwidth condition given by the roll off factor, impulse response optimization to reduce a PAPR can be carried out through selecting the response with the lowest PAPR from among the candidates. The modified filter with the roll-off factor of 0.45 yields the same PAPR as that of the conventional filter with the roll-off factor of 0.5. The above result shows that a narrower signal bandwidth under a constant PAPR condition or a lower PAPR under a constant bandwidth condition than the conventional filter can be achieved by the impulse response optimization of the modified filter.