Design And Implementation Of 5GHz-6GHz Low Noise Amplifier Applied In WLAN

With the development of wireless communication technology,the corresponding data transmission rate of WLAN 802.11ac(5GHz band)increases,which poses a new challenge to the radio frequency receiving system.As the key module of the receiver,Low Noise Amplifier(LNA)has important engineering application value.This paper designs and implements a 5GHz?6GHz low noise amplifier for WLAN basing on 0.18?m SiGe BiCMOS process.The main work is as follows.First of all,the main performance indicators of WLAN LNA products at home and abroad are summarized,the design focus and problems of WLAN LNA are analyzed.Secondly,the 5GHz?6GHz LNA is designed based on SiGe BiCMOS process,including main amplifying circuit,bias circuit,matching circuit and bypass path.The main part of amplifying circuit adopts a two-stage common emitter cascade structure to improve the LNA gain.By adjusting the number of parallel transistors(m)to change the input real part of impedance,the distance between the maximum power transmission impedance point and the best noise matching point is reduced,the input matching is simplified and the noise performance is improved.Then a new structure of active bias circuit is proposed,which has better temperature stability than traditional active bias circuit.The temperature drift coefficient of working current is reduced from 8.91e-4/? to 17.4e-6/?.Input and output impedance matching adopt L-type network,which has simple structure,less influence on circuit noise and high stability.The bypass circuit is added to effectively block the influence of large signal on the circuit.Thirdly,the layout of important components in LNA layout is designed,the RF signal path is designed as straight as possible,and the SiGe HBT is designed with 3×2 distribution by M4-M6 metal wiring.Finally,the test results show that the LNA is stable from 5GHz to 6GHz at 3.3V.The noise figure is about 2.18dB and the corresponding gain is about 23.5dB at 5.5GHz.The gain in bypass mode is about-10.4dB.The DC power consumption is about 20.79mW.All indexes meet the design requirements.