Vision

To optimise the quality process when manufacturing plastic parts with RF shielding characteristics.

Rationale

I was tasked with the creation of a basic attenuation meter, and the formation of a suitable test routine. The client uses a commercially available stainless-steel fibre impregnated ABS in one of their products. This material has RF shielding properties, but only if processed correctly. During the injection moulding process, once the material is heated up, is is forced along a barrel using a screw mechanism. Under certain circumstances, it is possible for the stainless-steel fibres to be broken up leading to a reduced RF attenuation performance.

The client wanted to reduce possible supply issues by allowing the moulding company to characterise electrical performance alongside the standard dimensional checks already performed therein. Although the client was using a signal generator and spectrum analyzer internally to qualify the plastic parts but it was deemed inappropriate to loan them to the moulding company for the duration of the moulding process. As the main focus of the attenuation meter was as a go-nogo gauge only relative values were required, and absolute values could be ignored.

Features

• Two coupled antenna
• Red/Green LED

Realisation

To emulate the functionality of the signal generator and spectrum analyzer combination, an RF transmitter and RF power meter could be used.

Atmel offer the ATA5749; a programmable transmitter capable of transmitting over a range of frequencies using a single crystal. The job of RF power meter would be fulfilled by Maxim's MAX2015. The basic operation is to characterise a number of pre-production samples of the ABS moulding using the signal generator and spectrum analyzer. Once characterised, the client will select the worst acceptable product for use as a golden-sample. This golden-sample will then be used by the supplier to calibrate the attenuation meter.

Future

N/A