| Low Noise Amplifier（Low Noise Amplifier,LNA）is a key circuit unit at the front end of radio frequency receiver in wireless communication system.In order to meet the requirements of diverse communication standards（mainly for 5G communication standards）,transceivers need to work in multiple bands.On the other hand,due to the different transmission paths and media,the received signal intensity of the receiver changes to a great extent,which requires LNA to adjust the gain according to the strength of the input signal to ensure the output signal is stable.The disadvantages of traditional LNA circuit structure are:inadequate expansion of adjustable range,single gain regulation mode,not meeting the requirements of coexistence of multiple protocols including 5G at the same time.For the technology of LNA gain regulation,there are some problems such as small gain regulation range and large power consumption,which also affect the noise performance of LNA to a certain extent.In order to solve these problems,two LNA circuits using active devices are designed.First,a dual-adjustable gain LNA using a MOS switch array and an adjustable transconductor was designed.The LNA circuit includes input stage,amplifier stage and output stage.In the amplifier stage,discrete regulation of the gain was realized by using MOS transistor switching array,continuous regulation of the gain was realized by using adjustable transconductor.In the input stage,cascode structure was adopted,and resistance-capacitor parallel negative feedback and source inductance negative feedback were added to realize input impedance matching,while low noise figure was achieved at the output stage.The differential output with the same amplitude and opposite phase was realized by using the active Barron structure.Based on the TSMC 0.18μm CMOS process library,the circuit is simulated and verified by using the RF integrated circuit design tool ADS.The results show that,at 5.8 GHz frequency,the gain can be adjusted in the range of-7 dB to 20 dB under discrete and continuous regulation mode.The minimum noise coefficient NF is 3.7 dB,the maximum linearity IIP3 is-2.5 dBm,the input reflection coefficient S111 is less than-25 dB,and the output reflection coefficient S222 is less than–35 dB.The VGLNA gain has dual adjusting functions of discrete mode and continuous mode.It can be adjusted by digital and analog circuits at the same time.It also has good noise figure,linearity,input and output matching parameters.Secondly,an adjustable multi-band low power LNA with active inductor was designed.In the input stage,the LNA utilizes the adjustable inductance of the active inductor to achieve the input impedance matching in different frequency bands by adjusting the combined bias and changing the inductance.The LNA has a wide adjustable range,and uses the low noise performance of the noise cancellation branch to achieve the input noise matching of the LNA.In addition,in the amplifier stage,the common-emitter common-base-common-emitter two-stage amplifier structure is transformed into a current multiplexing structure with only one DC path,which not only realizes two-stage amplification but also reduces power consumption.A load resistor is used at the output terminal to achieve output impedance matching.Based on the Jazz 0.35 um SiGe BiCMOS process library,the circuit is simulated and verified by using the RF integrated circuit design tool ADS.The results show that the LNA has a voltage gain of 23.7 dB and 23.9 dB at 3.6 GHz and 5.6 GHz,a noise coefficient of 4.33dB and 4.51 dB,a IIP3 of-4.5 dBm at 3.6 GHz and 5.6 GHz,an input echo loss of-21.9 dB and-21.7 dB,an output echo loss of-23.5 dB and-16.0 dB,and a DC power loss of 14.9mW and 15.4 mW,respectively.The LNA has low power consumption at 3.6 GHz and 5.6GHz,and has good noise figure,linearity,input and output matching parameters. |
