Research And Implementation Of SiGe BiCMOS Low Noise Amplifier For 5GHz WLAN

The field of wireless communications has continued to flourish for the past two decades.In recent years,the rapid growth of communication users and the rapid update of the technology have placed higher demands on modern wireless communications.WLAN(Wireless local area network)avoids bloated physical connections among mobile devices.The improvement of bandwidth,data throughput and data rate requirements of LAN applications has promoted the development of WLAN,which brings an evolution from the original single-band 802.11 b/g to 802.11 ac.802.11 ac in Multiple Input Multiple Output(MIMO)mode provides up to 6 Gbps of transmission rate per transmit/receive link.In order to save manufacturing costs,most wireless modules of WLAN are currently based on highly integrated IC modules.The noise figure and gain of the low noise amplifier(LNA)are quite important to the sensitivity of the entire receiver.Higher frequency LNAs often use expensive GaAs,Si-BJT or MESFET processes to reduce the effects of parasitic parameters.Although Si CMOS technology has an obvious price advantage,while its linearity and efficiency are quite poor.Therefore,the SiGe BiCMOS process is a compromise between high performance and low price.It not only combines the characteristics of bipolar process and CMOS process,but also meets the requirements of RF system performance and low power consumption.The structure of LNA is divided into single-ended and differential types,the former is sensitive to the parasitic inductance of the grounding hole,and the latter consumes a large amount of power and noise.This paper presents a 802.11 ac low-noise amplifier integrated in 0.35 um SiGe BiCMOS process with bypass function to balance the larger input signal.In the circuit design,the SiGe HBTs were designed with inductive emitter degeneration structure.While increasing the real part of the input impedance,the distance between the minimum noise circle and the maximum gain circle is reduced,and the stability is also improved.The innovation of this paper's design is mainly reflected in the Bypass function of the LNA circuit,which makes it have a bypass effect on large signals and also can optimize the noise figure.And it also has some novelty in the adaptive bias structure and matching design based on the traditional current mirror structure adopted in the circuit design.According to the simulation results,the HBT low-noise amplifier is unconditionally stable when the power supply voltage is 5 volts and the noise figure(NF)is about 2.2 dB with small signal gain 13.3 dB,and 7.2 dB with insertion loss for LNA enabled and LNA bypass status,respectively.The input third order intercept point is about 10.2dBm with two-tone signal while total input power is 0 dBm(-3 dBm/tone).The chip measured results show that the noise figure(NF)is about 2.4 dB with small signal gain 11.5 dB,and 9 dB with insertion loss for LNA enabled and LNA bypass status,respectively.The input third order intercept point is about 12.2dBm with two-tone signal while total input power is-10 dBm(-13 dBm/tone),which has basically achieved the low noise and high stability design requirements.