Design Of A C-Ku Band Ultra-Wideband Low Noise Amplifier And Optimization Techniques Research

Recently,Ultra-Wideband(UWB)wireless communication system has been making a rapid development due to its excellent technical features.It not only can solve the problem of communication capacity and rate but can alleviate the problem of increasingly scarce spectrum resources today,and shows great application prospect in the future communications.Meanwhile,the UWB wireless communication system also presents some challenges to the design of the RF front-end,especially the design of low noise amplifier.To design an LNA meeting all the requirements,firstly the analytical method of LNA is discussed and then the broadband input matching technique,high frequency gain compensation technique and linearization technique are studied and analyzed in this thesis.Finally,the designed ultra-wideband LNA is based on a cascode structure which decreases the Miller effect and improves wideband performance.To enhance the linearity of the designed circuit,a low value resistor R_e is inserted between the emitter of the input transistor and the small signal ground,intentionally.The wideband input matching is realized using resistive feedback combined with a preceding passive network.A peaking inductor is added in series with the load resistor,which can overcome the problem of gain roll-off at high frequency and maintain a wideband flat gain.A passive network is designed between the output port and the core of the LNA to achieve a good linearity and output matching.The design results of the band-gap circuit are also given in this thesis.Compared with traditional band-gap,compensation circuit is added here which can produce compensating current at very low or very high temperature.Reference current is the summation of the current from the traditional band-gap and the compensating current,which has a better temperature characteristic.Detailed theoretical analysis and derivation have been made around the designed LNA in input matching,gain,noise,and linearity.Based on 0.18?m SiGe BiCMOS technology,the schematic and layout have been finished on Cadence platform and the post simulation shows excellent results.Within the frequency range of C-Ku,the input return loss varies from-15dB to-11dB,realizing a good matching.The gain is 16dB at 4GHz and increases with frequency to 17.8dB at 18GHz.The fluctuation of which is 1.8dB.Through the impedance transformation effect of the output passive network,a wideband output matching better than-12.5dB is also achieved in the interested band.The results indicate that the NF over the C-Ku band is less than 3.3dB,and the linearity of the LNA expressed by IP1dB is-12dBm@15GHz,meeting project requirements.This LNA works under a3.3-volt supply and dissipates a total DC power of 57mW.Monte Carlo and temperature simulations are gave out in this thesis.The results show that with process variation and mismatch,the input and output matching are all meet the requirement and the gain is larger than 15dB,the NF less than 3.5dB over the C-Ku band.With the temperature varying in the range of-50~100 degrees Celsius,the simulation results indicate that at 11GHz,the input return loss is less than-10.6dB,the output return loss less than-14.2dB,the gain larger than 14.7dB and the NF less than 4dB.