For the second order PLL with equation:
$$1-\dfrac{2\zeta\omega s + \omega^{2}}{s^{2}+2\zeta\omega s + \omega^{2}}$$
I used Matlab and obtained a Bode Magnitude (with zeta = 0.3, 0.5) like:
In the book "Phase Lock Loops and Frequency Synthesis" by V. F. Kroupa, the author has a plot that looks like this (for a 2nd order system found on page 14 of the book):
How can I get my slope, that is 40dB/decade, to match his 20dB/decade? Thanks.