Study On RF Filter Of Digital Interphone For Oceanfishery Vessels

At present, most countries mainly use analog interphone in the field of oceanfishery vessels. Interphone is experiencing huge transformation from simulation technology to digital technology. Study of digital interphone has long-term significance. As electronic equipment has a higher request on reducing volume and weight, the miniaturization of passive filter has become new development tendency. But the traditional methods of design exist some disadvantages.This paper mainly studies RF filter on the slipway, a part of project research on digital interphone of oceanfishery vessels, launched by National Engineering Research Center of Maritime Navigation System. Currently, RF filter developed by relevant researchers is unsatisfied, containing stray wave and parasitic bandpass. This paper uses passive LC filter. When designing filter circuit, based on general methods of transformation from lowpass prototype filter to bandpass filter, this paper transforms it to coupling resonance bandpass filter by using circuit of impedance transformation, and cleverly tries methods of using port network transformation and cascading lowpass filter to increase attenuation poles and improve properties of filter. When optimizing filter circuit, by using methods of computer aided design, this paper makes actual output voltage be close to ideal output voltage to achieve ideal filtering effect. When making material object of filter, by using small and high quality inductance coils and small MLCC(Multiplayer Ceramic Chip Capacitors), and fixing values of inductors and parts of capacitances, and reducing use of part of capacitors, and considering loss of components, and using computer aided design, and reasonably designing layout of PCB(Printed Circuit Board), this paper overcomes shortcomings of traditional design methods, which reduces size and cost of filter and simplifies debugging process, which creates favorable conditions for miniaturization and mass production of passive LC filters and is of great significance. Filtering effect of material object of filter is well, which meets performance index. Experimental results show that the thought of design is correct and original, and the method is practical and effective, which has a certain value.