Study On Influence Facts Of Shielding Effectiveness Of Marine Double Shielded Box

With the improvement of the degree of automation of ships,more and more electronic devices are used in marine communications,navigation,monitoring,diagnosis,and control,resulting in more complex electromagnetic environments.In order to ensure that the equipment is in a low-noise electromagnetic environment,the function of the equipment is not degraded.The electromagnetic compatibility standards for marine electronic equipment impose stringent requirements on the radiation disturbance limits of marine VHF communication frequency bands(156 to 165 MHz),and the radiation disturbance limits are determined by 54dB?V/m dropped sharply to 24dB?V/m.Aiming at the special requirements of the radiated disturbance limit of marine VHF communication frequency band,starting from cutting off the electromagnetic radiation emission path,a double-shielded box structure is proposed to achieve effective suppression of radiated noise in the test frequency band,especially in marine VHF communication frequency bands.The main research content is as follows:(1)Simulate and analysis the resonant characteristics,slot resonance characteristics,and slot-cavity coupling resonance characteristics of the marine single-shielded box,analysis the influence of the marine double-shielded tank geometry on the electromagnetic resonance characteristics,and comparative analysis the performance of the double-shielded box and the single-shielded box;(2)For the marine double-shielded box structure,based on the transmission line matrix method and streamlined model technology,the influence of the structural parameters of the inner and outer shield box and the coupling effect of the open gap on the shielding effectiveness of the double-shielded box is simulated;(3)Establish a double-shielded box model of the Lecal Engine Control Alarm System,using the pulse voltage circuit as the excitation,perform pulse transient circuit field-circuit co-simulation,cable induction common-mode current simulation and external cables radiation emission simulation,combined with tests,analysis the test results.Compared with the single-shielded box,the proposed double-shielded box structure significantly improves the shielding effectiveness under the premise that the outer shielding box has certain shielding effectiveness,and the double-shielded box resonance characteristics are determined by the inner shielding box.,to achieve the electromagnetic resonance frequency transfer.For the double-shielded box structure,through the simulation and analysis,some suggestions on the design of structural parameters for improving the shielding effectiveness are proposed.