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mathieu_Brm

Compute expansion coefficients 'Brm' and eigenvalue 'bm' for odd angular and radial Mathieu functions.

Calling Sequence

[ Brm, bm ] = mathieu_Brm( m, q )

Parameters

m

the order of Mathieu function

q

the value of q parameter (can be positive, negative or complex number)

Brm

expansion coefficients   for odd Mathieu functions

bm

characteristic value   for odd Mathieu functions

Description

Mathieu_Brm computes expansion coefficients for odd angular and radial Mathieu functions.

This function formes tri-diagonal matrix as an equaivalent to known recurrence relations [1-2]:

The size of matrix is calculated from values of q and m by the formulas from Zhang & Jin [3].

The matrixes have the following structure [4-6]:

and

This function is based on fcoef1 program, developed by Da Ma [7]. Using Scilab spec function mathieu_Brm founds at once expansion coefficients and eigenvalue .

During unit-testing of this function expansion coefficients and characteristic values were compared to well-known tables: Tables 20.1, 20.2 from [2], Tables 14.2, 14.4 from [3]. The results are very close.

Examples

// Example: Expansion coefficients Arm as continous functions of q
    f=scf(); mrgn = 50; font_sz = 4; f.figure_name='Expansion coefficients Brm as continous functions of q';
    sz = get(0, 'screensize_px') + [-1 mrgn-1 0 -2*mrgn ] ;

    q = linspace(0, 40, 40);
    Brm2n = zeros(6, length(q));
    Brm2n1 = zeros(6, length(q));
    for i=1:length(q)
        B2ns = mathieu_Brm(1, q(i));
        B2n1s = mathieu_Brm(2, q(i));
        Brm2n(1:6, i) = B2ns(1:6);
        Brm2n1(1:6, i) = B2n1s(1:6);
    end
    subplot(1,2,1)
        plot(q', Brm2n1');
        legend('$B_1^{(1)}$', '$B_3^{(1)}$', '$B_5^{(1)}$', '$B_7^{(1)}$', '$B_9^{(1)}$', '$B_{11}^{(1)}$');
        xlabel('$q$');
        ylabel('$B_m^{(1)}$');
        xgrid
        h = gca(); h.margins=[0.15 0.05 0.05 0.12]; h.font_size = font_sz - 1;
        h.x_label.font_size=font_sz; h.y_label.font_size=font_sz;
        h.children(1).font_size = font_sz;
    subplot(1,2,2);
        plot(q', Brm2n');
        legend('$B_0^{(2)}$', '$B_2^{(2)}$', '$B_4^{(2)}$', '$B_6^{(2)}$', '$B_8^{(2)}$', '$B_{10}^{(2)}$');
        xlabel('$q$');
        ylabel('$B_m^{(2)}$');
        xgrid
        h = gca(); h.margins=[0.15 0.05 0.05 0.12]; h.font_size = font_sz - 1;
        h.x_label.font_size=font_sz; h.y_label.font_size=font_sz;
        h.children(1).font_size = font_sz;
    f.figure_position=[sz(1) sz(2)];
    f.figure_size=[sz(3) sz(4)];

See Also

Authors

R.Coisson and G. Vernizzi, Parma University

N. O. Strelkov, NRU MPEI

Bibliography

1. N. W. McLachlan, Theory and Application of Mathieu Functions, Oxford Univ. Press, 1947.

2. M. Abramowitz and I.A. Stegun, Handbook of Mathematical Functions, Dover, New York, 1965.

3. S. Zhang and J. Jin. Computation of Special Functions. New York, Wiley, 1996.

4. J. J. Stamnes and B. Spjelkavik. New method for computing eigenfunctions (Mathieu functions) for scattering by elliptical cylinders. Pure Appl. Opt. 4 251–62, 1995.

5. L. Chaos-Cador, E. Ley-Koo. Mathieu functions revisited: matrix evaluation and generating functions. Revista Mexicana de Fisica, Vol. 48, p.67-75, 2002.

6. Julio C. Gutiérrez-Vega, “Formal analysis of the propagation of invariant optical fields in elliptic coordinates,”Ph. D. Thesis, INAOE, México, 2000. (online at http://homepages.mty.itesm.mx/jgutierr/).

7. Da Ma. General Mathieu functions with arbitrary parameters V1.0 - File Exchange - MATLAB Central.


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