Block diagram detailed description - page 3

The 1497MHz signal coming from each cavity is carried through 40ft of Heliax1/2" cable to a Down-Converter located in a rack behind the shield wall. The Down-Converter mixes the high-frequency signal with a 1496MHz signal produced by an oscillator, in order to obtain a 1MHz signal. Indeed, a 1.5GHz signal gets quickly attenuated in the line, so one need to decrease its frequency to be able to carry it to the counting house.

The outputs of the two Down-Converters are connected to a triaxial cable (200ft) which shields the signal from external noise.

Plans for the future are:

• replace the Heliax 1/2" cables by Heliax 7/8" (this will make the attenuation decrease by a factor 2)
• redesign the two Down-Converters in order to decrease the intermediate frequency from 1MHz to 10kHz; this will decrease the noise in the cables and make the cross-talk disappear.

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