Selective vehicle identification system - uses multiplier and logic circuit for spectral analysis of IR from exhaust gases

摘要

The remote detection system uses the exhaust gases emitted by a vehicle IC engine to produce a selective identification. The exhaust gases provide an infrared absorption spectrum which presents an instant contrast to the spectrum of the ambient air. A spectral filter provides an electric signal which is amplified and applied to one input of a comparator. The second input receives a reference signal representing the ambient air. A circuit for correcting the reference signal includes a delay acting on the comparator output in parallel with a low-pass filter which eliminates the detector pulse signal. A variable multiplier signal introduces a contrast correction function, and an adder forms the algebraic sum of the delayed voltage and the multiplied voltage to form the reference voltage signal.