| The frequency of S band ranges from2to4GHz and Its wave length range is from150to75mm. Due to the transmission patterns and characteristics of this frequencyband, the electromagnetic wave of S band are widely used to relay, satellitecommunications and radar. At the same time, widely used devices such as bluetooth,wireless routing and wireless mouse also use this band. Because of its wide applicationprospect, more and more researchers develop new S-band devices.The paper analyzes the fundamental principle of the broadband spectrum receiverfront-end at2to3GHz frequency range in S band and introduce several typicalstructures of broad receiver front-end. Then, the superheterodyne secondary mixingstucture is used to make the2to3GHz broadband RF signal down conversion to lowmedium frequency70MHz for back-end data samping and processing. The first-levelmixing of the structure is high intermediate frequency and then the second-level mixingis low intermediate frequency in the overall scheme design. It greatly improves themirror frequency interference. In the design of passive parts of the system, some filterdesign methods are focused on and short-circuit side quarter wave filter stucture isimproved to overcome the disadvantage of its large scale and build the calculationinterface software for this type of filter and small wide stopband frequency suppressionlow-pass filter with the interpolation of T section is successfully designed. According totest performance, it is better than some demstic similar products. For design of activecomponents, the lossy equilibrium is introduced into the output match network ofbroadband low noise amplifier for increasing the stability of the circuit and improvingthe gain flatness.At last, a cross coupling coaxial cavity filter is designed as the first level ofintermediate frequency filtering. Two mixers and various small signal gain amplifiersand a dot frequency signal source are fabricated and debugged. At the same time, thetest results are given. |
PDF Full Text Request