Research On The Key Technology Of RF Front-End For Mid-Frequency Aperture Array Of Square Kilometer Array

The design of a new radio telescope known as the Square Array(SKA)is well under way in the international astronomical community,it's two orders of magnitude more seansitive than the best radio telescope in the world today.When the whole telescope is completed,the total receiving area reaches one square kilometer,and the telescope needs tens of millions of receiving units.Therefore,it is the requirement of the telescope to design a high performance,low power consumption and low cost receiving unit.The design goal of the low noise amplifier(LNA)and the variable gain amplifier(VGA)is estimated by the performance of other components.Considering the cost,integration level and technical maturity,SiGe technology is adopted,the design of LNA and VGA is based on HHNEC 180nm SiGe BiCMOS technology.The main content and results of this thesis are as follows:(1)The LNA adopts heterojunction bipolar transistor(HBT)to realize low noise performance.The first stage adopts capacitance and resistance load in series based on feedback inductor,expanding the bandwidth by parasitic capacitance of the HBT;the second stage is the emitter follower amplifier,providing broadband output match.The good noise performance is realized by the multi LC resonant structure,the result is verified by simulation:the noise figure of LNA is lower than 1.4dB over 500MHz?1500MHz,the lowest noise figure is 0.84dB.The LNA achieves power gain greater than 15dB,both input and output reflection coefficient are greater than-10dB and 1dB compression point is more than-25.3dBm with 34mW power consumption at 3.3V power supply.The LNA layout area is 1.1 mm*0.98mm including pad(2)The VGA adopts metal-oxide semiconductor field-effect transistor(MOS)to realize low power.There are three parts in the VGA,a gain-fixed noise-cancelling amplifier,an amplifier with variable gain consisting of three current steering amplifiers and a source follower amplifier as ouput circuit.The result is verified by simulation:the VGA achieves a noise figure under 15dB,a dynamic gain of 20.5dB,gain step is 3dB,both input and output reflection coefficient greater than-lOdB and 1dB compression point more than-5.2dBm with 18.9mW power consumption at 1.8V power supply.The VGA layout area is 1.5mm*1.16mm including pad.After the analysis,we found both LNA and VGA have nice noise performance and other indicators meets the design target,they can well be applied to SKA intermediate frequency array front-end.