In this paper we have presented an approach to the problem of disrupting effectively a commercial nonlinear electronic system.
Our approach is based on a minimal understanding of the circuit concerned, the basic design and operational specifications,
rather than a detailed knowledge of the design implementation itself.
By designing a test circuit with identical specifications to the commercial circuit and concentrating on one method of in-band disruption, we have been able to determine an input signal which proves to be extremely effective at disrupting the system
in practice.
Analytical, numerical and experimental study of the test circuit confirms the effectiveness of our approach at inducing disruption
in a realistic PLL design. Experimental investigation of the commercial circuit itself demonstrates: that our disruptive signal
is effective against commercial equipment as well as a test circuit, that it is the PLL of the INMARSAT terminal which gives
rise to disruptive dynamics, and that our approach to circuit disruption is of practical value.
From the results presented in this paper it is clear that in-band disruption of commercial systems can be achieved using relatively low power levels. In consequence, the ideas outlined in this paper offer a methodology for two important tasks: the design of signals
with which to disrupt commercial systems in-band, and the design of signals with which to ensure that any commercial circuit
is robust against such disruption.