Research And Design Of 3.5GHz WiMAX Radiofrequency Front-end Circuits

While computers and communications technology are exploding, Wireless Broadband Access are prevailing increasingly in personal and commercial computer field. WLAN are evolving toward using higher frequencies, wider bandwidth and more functionality to satisfy growing demands of usersworldwide. Worldwide Interoperability for Microwave Access then emerge with the tide of the times. WiMAX Work frequency basis nation of dissimilarity but variety, from 2-11 GHz. 2.3-2.5 Ghz and 5.8 GHz common using frequency band in the United States, At Europe and Asia, common frequency band is 3.5 GHz.Authorization with openning a frequency band all can usage adoption the 256 OFDM modulation, transport speed is 1-75 Mbps.With increasing frequency and adding bandwidth, design of RF circuit is harder and harder. Tools of accessorial computer analysis and synthesis are underway, the results of these tools only can be references. So design of RF circuit is dependent to a great extend on test and experience of designer. The paper has discussed RF front-end design and simulation according to IEEE802.16 standard of Wimax with ADS.In this paper the main work is done as following:First, the standard of Wimax is introduced, and the general design theories and methods are discussed. Carried on summary to some foundation theories and concept of microwave electric circuit design, include S parameter, low nosie amplifer design, Nosie with non-line distortion. Then, we design and simulate separately link budget calculation of the transmit-receive RF system, getting circuit system in accord with the standard. Last, we customize the specifications according to link budget calculation, and finish the design and simulation of subcircuits. subcircuits consist of the low noise amplifier, RF filter, mixer, driver amp, image filter, power amplifier, transmit-receive switch and IF filter and so on. We design mainly amplifier including modeling high frequency modulation,than designing DC bias, analysing gain of amplifiers. Finally, We use broadband amplifier to finish IF amplifier in the 480MHz band same gain amplifier in the 3.5GHz band with different matching.