On undershoot in SISO systems

In this technical note we show that the step response of an asymptotically stable strictly proper nonminimum phase continuous time system with m(sub 1) real open right half plane zeros, no conjugate complex zeros and poles, and with real open left half plane zeros and poles satisfying a given 'bracketing' condition, exhibits undershoot exactly int m(sub 1) + 1/2 times. Both qualitative and quantitative arguments are also introduced to highlight the main issues under discussion. Simple examples are given to illustrate and complement the main result of this note.