  This paper addresses a phenomenon caused by resetting only one of the two
states of a so-called second order "Constant in gain Lead in phase" (CgLp)
element. CgLp is a recently introduced reset-based nonlinear element, bound to
circumvent the well-known linear control limitation -- the waterbed effect. The
ideal behaviour of such a filter in the frequency domain is unity gain while
providing a phase lead for a broad range of frequencies, which clearly violates
the linear Bode's gain phase relationship. However, CgLp's ideal behaviour is
based on a describing function, which is a first order approximation that
neglects the effects of higher order harmonics in the output of the filter.
Consequently, achieving the ideal behaviour is challenging when higher order
harmonics are relatively large. It is shown in this paper that by resetting
only one of the two states of a second order CgLp, the nonlinear filter will
act as a linear one at a certain frequency, provided that some conditions are
met. This phenomenon can be used to the benefit of reducing higher order
harmonics of CgLp's output and achieving the ideal behaviour and thus better
performance in terms of precision.
