The Development Of The Ku-band Up-converter

Up-converter for the transmission link is an important part. Up-converter whichmakes use of the frequency spectrum of nonlinear device changes the IF signal to theRF signal. And then the signal through the power amplifier will be launched out. Due tothe rapid development of China’s satellite communications, people’s requirement forspectrum resource is not limited to the low frequency band. For example, UHF bandand C-band. Ku-band shows many characteristics such as large communication capacity,small external interference and high antenna gain. Therefore, researchers at home andabroad pay much attention to the Ku-band.The paper gives a detailed design process and test methods for the Ku-bandup-converter and presents three novel compact microstrip filters. The main works of thispaper are as follows:1. To develop programs. According to the technical requirements of the Ku-bandup-converter, system design program will be obtained after careful analysis. In thedesign of up-converter considering the problems needing attention such as port isolationimage rejection and self-excited. Depending on the developed programs, budgetanalysis about gain of the levels and noise factor for the entire link is shown. Gain,noise factor and VSWR of entire link are simulated using ADS software.2. The development of the Ku-band up-converter. Design of the system the unitcircuit is completed including passive circuit, conversion and amplification circuit and aDC power supply circuit. Passive circuit mainly refers to the design of image rejectionmicrostrip filter. Which frequency conversion and amplification circuit focuses on isselecting the IF amplifier, RF amplifier, LO amplifier and mixer.1dB compressionpoint and gain are considered for selecting chips. DC power supply circuit is primarilyresponsible for supplying power for the chips.3. Design of filters. Hairpin image rejection microstrip filter is designed. Proposingthree novel compact microstrip filters such as cross-coupled microstrip filter, T-sectionloaded dual-mode dual-band microstrip filter and the stubs loaded tri-mode microstripfilter. Theoretical analysis and simulation tests of filters are shown in detail. These filters have many advantages such as compact structure, small size and good bandrejection. These advantages determine that filters can be widely applied in the field ofwireless communication.4. System test. It describes a microwave circuit processing technology and thesolution method of electromagnetic compatibility problem. The Ku-band Up-converteris completely the assembly. Through the spectrum analyzer, signal source and the vectornetwork analyzer test show image-reject reached-47dB and meet the indicators. But theband flatness is not up to the requirements. Finally the index meets the indicators byincreasing the equalizer.