Research On DC-18GHz Ultra-wideband Low Noise Amplifier

Low noise amplifier(LNA)is located at the front of RF receiver,which is the core component of microwave system.Its performance directly affects the receiver sensitivity as well as the noise figure of the whole system.At the same time,Ultra Wide Band(UWB)technology has developed rapidly,and the UWB LNA with excellent performance has a high research value.The main content of this paper is to design and implement a DC-18GHz UWB LNA.In this paper,the research background and development status of UWB LNA are investigated at first,and then the theory and design method are analyzed.By comparing several common methods of broadband amplifier design,the negative feedback method is chosen as the design method of UWB LNA.To meet the design index,the HEMT die is selected,the LNA adopts three stage amplifier cascade circuit structure with single power supply,microstrip and discrete components combined to achieve matching network.The first stage amplifier circuit with parallel negative feedback structure to improve the stability of the amplifier,broaden the bandwidth,while using transistor parallel structure to optimize broadband noise performance.The second and third stage amplifier circuits are used to increase the power gain and reduce the gain flatness.Output matching network with consumption improves the system stability and reduce the output reflection coefficient.In this paper,the DC simulation,S-parameter simulation and momentum simulation are carried out in ADS.After the design of the LNA circuit,the tuning method is used to optimize the circuit,and the satisfactory simulation results are obtained.Finally,thin-film circuit and components are sintered on the cavity surface using micro-assembly process directly,goldwire bonding are used to achieve interconnection between components.The test results show that in the DC-18GHz bandwidth the noise figure of the LNA is less than 2.5dB,the gain is greater than 22dB,while the whole machine has a low power consumption of only 210mW.The results show that the amplifier has good characteristics in the ultra wide band.