This thesis presents the design and fabrication of the surge protective devices(SPDs) for computer networks. The study has involved a broad review of the international standards together with experimental as well as theoretical simulation works on the SPDs design. Surge measurements have been carried out in places where computer network devices are installed to investigate the distribution of surge level and occurrence. Electrical equivalent models of a gas tube and a bi-directional avalanche diode are proposed.
Computer simulations were conducted using PSpice to derive an optimal configuration of the SPDs. Several types of the SPDs available for Local Area Networks up to 8 lines were designed and fabricated.
The fabricated SPDs are composed of 10[kA] rated gas tubes, solid resistors, bi-directional avalanche diodes. A fast recovery diode is added to the SPDs in series with the bi-directional avalanche diode to reduce insertion loss due to the large stray capacitance of the bi-directional avalanche diode in high frequency domain.
Test set-ups and measurement techniques were conducted according to the terms of the international standards IEC 61000-4-5 and IEC 61643-21 which are prescribing test procedures on the surge characterization of the SPDs.
8/20[㎲] 5[kA], 5/300[㎲] 100[A] and 10/1000[㎲] 100[A] were used to test the surge blocking performance of the SPDs. In the application of these surge waveforms, the SPDs clamped the surges below 20[V] that is safe level for computer networks.
Network analyzer(HP8753D, 30[kHz]～6[GHz]) was used to estimate signal transmission performance as standing wave ratio, frequency bandwidth, insertion loss, return loss and near-end crosstalk. The high cut-off frequency of -3[dB] was 204[MHz] and return loss and near-end crosstalk in ranges from 500[kHz] to 100[MHz] were under -10[dB] and -20[dB], respectively.
The test results of the SPDs showed a good agreement with the simulation data and are satisfied with the international standards.