Design And Realization Of X-band Down-converter

With the popularization of smartphones and tablets and the development of wireless communication technology,the problem of frequency band scarcity has become more and more obvious,especially in the lower frequency band congestion phenomenon,has been the biggest problem to curb the development of wireless communications,so the development of high-frequency microwave equipment is the inevitable choice to solve the problem.X-Band(8GHz~12GHz)is an important microwave frequency band,mainly used as military frequency band,because of its small interference and strong data transmission ability,in radar,guidance,remote sensing,electronic warfare and other fields have been widely used.Transceiver System is an important part of wireless communication system,the core component that affects its performance is the frequency converter.Almost all transceiver systems are required to convert the RF signal and the IF signal through the frequency converter.This approach is used in modern communications,radar,navigation,remote sensing,electronic warfare,and so on.Therefore,it is necessary to study X-band converter,and it is also a hotspot.The research content of this thesis is to design and manufacture an X-band down-converter.Its input signal frequency range is 9.35GHz~9.85 GHz,and through the down-converter,its output signal frequency range is 1.25GHz~1.75 GHz.Its noise,phase noise,gain flatness and other electrical properties are better than the existing band converters.In this paper,the basic theory and realization method of frequency converter are introduced,including phase-locked frequency source,mixer,amplifier and filter.In order to facilitate the analysis and debugging,according to the modular design idea,the lower frequency converter is divided into the local oscillator module and the frequency conversion channel module.The local oscillator module is implemented by sampling phase-locked loop,and the input reference signal is used to produce a stable 8.1GHz local oscillator signal.The input signal of X-band is amplified,down-converted to L-band through the local oscillator signal,further amplified and filtered by the frequency conversion channel module.Design or select individual devices,optimization and estimation of the entire link through simulation software,finally complete the circuit design combined the shape.The design difficulty mainly lies in how to realize the low noise of LNA and the requirement of gain flatness.Use the balanced amplifier structure to match the input and output port,and amplitude equalizer structure to achieve and exceed the gain flatness requirements of the indicator.The size of the down-converter is 110mm×80mm×40mm.In-40℃~+70℃ temperature range,its main indicators are: at most 1.4 of both the input and output voltage standing wave ratios(VSWR),at least 47.5dB of Gain,at most ±0.3dB passband ripple,at least 2.2dB of noise figure,at least 65 dBc of clutter suppression,the local oscillator output of 8.1 GHz has low phase noise(better than,-74dBc/Hz@100Hz、-91dBc/Hz@1KHz、-112dBc/Hz@10KHz、-122dBc/Hz@100KHz).The test results of the down-converter show that all the indicators meet the requirements of the research...