A CMOS sensor used to locate intermittent faults on live aircraft wires is presented. A novel architecture was developed to implement the Sequence Time Domain Reflectometry method on a 0.5-m integrated circuit. The sensor locates short or open circuits on active wires with an accuracy of +/-1 ft when running at a clock speed of 100 MHz. A novel algorithm is proposed that utilizes the shape of the correlation peak to account for sub-bit delay, thus increasing the accuracy of fault location. The power consumed by the microchip is 39.9 mW.Index Terms-CMOS sensor, pseudo-random noise, reflectometry methods, spread spectrum, wire fault location.

Wiring problems in aging aircraft have been identified as the cause of several tragic mishaps and hundreds of thousands of lost mission hours. Intermittent wiring faults, which occur during flight, have been and continue to be difficult to resolve. This makes it necessary to monitor live aircraft wires continuously, without affecting the aircraft signals on live wires. Monitoring of live aircraft wires can be accomplished by various Reflectometry methods. Sequence Time Domain Reflectometry (STDR) is one of the Time DomainReflectometry methods for detecting discontinuities on live wires carrying signals or data, without disturbing them. In this paper, we have modeled this STDR system using MATLAB coding and interfacing with the Simulink blocks. This model prototypes the STDR method along with correlation to detect either open or short circuits.

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