function h = plotspectrum(type, centers, bandwidth, color, unit, varargin)


for n = 1:numel(centers)
    center = centers(n);
    switch type
    case 'sym'
        x = [-1,  -1,   0,   1,   1] * (bandwidth/2) + center;
        y = [ 0,  0.5,  1,  0.5,  0];
    case 'asym'
        x = [-1,  -1,   1,  1] * (bandwidth/2) + center;
        y = [0,   0.5,  1,  0];
    case 'asymflip'
        x = [-1,  -1,   1,    1] * (bandwidth/2) + center;
        y = [0,    1,   0.5,  0];
    otherwise
        error('Invalid type.');
    end
    switch unit
    case 'Hz'
        factor = 1;
    case 'kHz'
        factor = 1e3;
    case 'MHz'
        factor = 1e6;
    case 'GHz'
        factor = 1e9;
    otherwise
        error('Invalid unit');
    end
    tmp = patch(x/factor, y, color, varargin{:});
    if n == 1
        h = tmp;
    else
        h = [h, tmp];   %#ok<AGROW>
    end
end


switch unit
case 'Hz'
    xlabel('Frequency (Hz)', 'FontWeight', 'bold')
case 'kHz'
    xlabel('Frequency (kHz)', 'FontWeight', 'bold')
case 'MHz'
    xlabel('Frequency (MHz)', 'FontWeight', 'bold')
case 'GHz'
    xlabel('Frequency (GHz)', 'FontWeight', 'bold')
otherwise
    error('Invalid unit');
end
a = gca;
a.XAxis.FontWeight = 'bold';


end