#!/usr/bin/env python3

import numpy as np

def rrc_design(N, samples_per_symbol, roll_off = 0.35):
    coef = np.zeros(N)

    k0 = N/2
    Ts = samples_per_symbol

    for k in range(len(coef)):
        t = k - k0

        if t == 0:
            coef[k] = 1 / np.sqrt(Ts) * (1 - roll_off + 4 * roll_off / np.pi)
        elif abs(t) == (Ts / (4*roll_off)):
            coef[k] = roll_off / np.sqrt(2 * Ts) * \
                    ( (1 + 2/np.pi) * np.sin(np.pi / (4 * roll_off)) + \
                        (1 - 2/np.pi) * np.cos(np.pi / (4 * roll_off)) )
        else:
            coef[k] = 1 / np.sqrt(Ts) * \
                    ( np.sin(np.pi * t / Ts * (1 - roll_off)) + 4 * roll_off * t / Ts * np.cos(np.pi * t / Ts * (1 + roll_off)) ) / \
                    ( np.pi * t / Ts * (1 - (4 * roll_off * t / Ts)**2) )

    return coef

if __name__ == "__main__":
    import matplotlib.pyplot as pp

    c = rrc_design(50, 5, 0.35)
    print(np.sum(c))
    pp.plot(c)
    pp.show()