const epsilon = Math.sqrt( 10**(0.1*ripple) - 1 );

​

    let A = 4*R / (R+1)**2;

    if(!(order & 1))

        A *= 1 + epsilon**2;

    if(A > 1)

        return [];

​

    const gamma = (1/epsilon + Math.sqrt(1/epsilon**2 + 1))**(1/order),

            sigma = (Math.sqrt((1-A)/epsilon**2) + Math.sqrt((1-A)/epsilon**2 + 1))**(1/order),

            X = gamma - 1/gamma,

            Y = sigma - 1/sigma,

            alpha_i = (i)=> 2*Math.sin(Math.PI * i / 2 / order),

            beta_i  = (i)=> 2*Math.cos(Math.PI * i / 2 / order),

            B_i     = (i)=> X**2 + Y**2 - X*Y*beta_i(2*i) + alpha_i(2*i)**2;

​

    let elements = [ 2 * alpha_i(1) / (X - Y) ],

         t1, t2, t3, sub1, sub2, sub3, element_next;

​

    for(let i = 2; i <= order; i++) {

        [t1, t2, t3] = [-3, -1, -1];

        if(i & 1)

            [t1, t2, t3] = [-1, 1, 0];

        sub1 = 4 * Math.floor(i/2) + t1;

        sub2 = 4 * Math.floor(i/2) + t2;

        sub3 = 2 * Math.floor(i/2) + t3;

        element_next = 4 * alpha_i(sub1) * alpha_i(sub2) / (B_i(sub3) * elements[i-2]);

        elements.push(element_next);

    }

    return elements;

};

​

const low_pass = (Rs, Rl, ripple, order, Fc, isC)=> {

    const elements = chebyshev(Rl/Rs, ripple, order);

    let L = [], C = [];

​

    elements.forEach((e)=> {

        e = e / (2 * Math.PI * Fc);

        if(isC)     C.push(e / Rs);

        else        L.push(e * Rs);

        isC = !isC;

    });

​

    return [C, L];

};

​

const high_pass = (Rs, Rl, ripple, order, Fc, isC)=> {

    const elements = chebyshev(Rl/Rs, ripple, order);

    let L = [], C = [];

​

    elements.forEach((e)=> {

        e = 1 / (2 * Math.PI * Fc * e);

        if(isC)     C.push(e / Rs);

        else        L.push(e * Rs);

        isC = !isC;

    });

    return [C, L];  

};

​

const band_pass = (Rs, Rl, ripple, order, Fo, BW, isC)=> {

    const elements = chebyshev(Rl/Rs, ripple, order);

    const D = 1 / (2 * Math.PI**2 * Fo**2);

    let L = [], C = [];

​

    elements.forEach((e)=> {

        e = e / (Math.PI * BW);

        e = isC ? e / Rs : e * Rs;

        C.push(isC ? e/2 : D/e);

        L.push(isC ? D/e : e/2);

        isC = !isC;     

    });

    return [C, L];

};

​

const CalcFilter = (Ri, Ro, ripple, N, Fc, BW, type)=> {

  if(type == 0)      return low_pass(Ri, Ro, ripple, N, Fc, true);

  else if(type == 1) return low_pass(Ri, Ro, ripple, N, Fc, false);

  else if(type == 2) return high_pass(Ri, Ro, ripple, N, Fc, false);

  else if(type == 3) return high_pass(Ri, Ro, ripple, N, Fc, true);

  else if(type == 4) return band_pass(Ri, Ro, ripple, N, Fc, BW, true);

  return band_pass(Ri, Ro, ripple, N, Fc, BW, false);

}

​

​