The Design Of The Receiver RF Front-end In Mobile Terminal For Maritime Satellite Communication

RF receiver unit is an important part of the mobile terminals in maritime satellite communications, its main function is to transform the higher carrier frequency to a lower intermediate frequency. This article is mainly to design the front-end RF module circuit, including antenna, low noise amplifier and band-pass filter.Antenna is the first level of RF receiver to transmit and receive signals. The designed antenna in this thesis is right-hand circular polarized, we apply it in the maritime satellite communications to inhibit the rain and fog interference and multi-path reflection. This article firstly calculates the initial size of antenna according to the micro-strip transmission line theory, and then uses the electromagnetic simulation software HFSS to simulate and optimize it; meanwhile we use the electromagnetic simulation software ADS to simulate and design the feed power divider network. Finally we make in-kind and use the vector network analyzer to test the real antenna, and get a relatively satisfied test results.As the second stage of Receiver unit, the low noise amplifier (LNA) plays an important role, its noise performance directly affects the whole circuit, thus we hope the noise of it is as small as possible, meanwhile it can provide sufficient gain to overcome the noise of follow-up levels (such as the mixer). This article uses ADS to simulate LNA, the simulation results meet the index requirements of the system.Micro-strip hairpin filter has the advantages of small size, low cost, easy to integrate, it has a good prospect in the design of microwave planar circuit, so we apply it to the band-pass filter design. Firstly we use Ansoft Designer to get the initial size of the hairpin filter, then use HFSS to optimize it and use the LPKF carving machine to make in-kind. The test results of vector network analyzer show that the designed filter meets the scheduled target requirements.This thesis promotes the localization of the RF front-end circuit in maritime satelli-te communications and is expected to reduce the maintenance and repair cost, so it has some practical value.