Research And Design Of SiGe BiCMOS Ultra Wideband Variable Gain Amplifier

With the rapid development of wireless communication technology, more and more techniques and methods turn up.As a promising new wireless communication technologies,UWB(ultra wide band)with its high data speed,low power consumption is drawing more and more attention. Variable Gain Amplifier(VGA) is one of the key modules of wireless receiver.The research of VGA is of great importance.With the development of Bi CMOS process,RFIC can be achieved by Bi CMOS.Bi CMOS circuit design of UWB transceivers and components is of significant interest in the wireless communication research communit.Firstly this thesis introduces the background and research of the VGA,then describe the basic design parameter of this circuit.A quantitative analysis is carried out on broadband techniques,such as shunt-peeking,emitter capacitance negative feedback structure.According to the requirement of this circuit,we chose the Signal Summing strecture to realize the variable gain unit.At the same time emitter capacitance negative feedback structure are used to achieve broadband gain and its flatness.We use a control signal processing circuit to acquired linear gain control characteristic and design a DAC circuit which make up with the cascode current mirror to complete the digital control of ultra wideband variable gain amplifier.The result of simulation indicate that the strcture used in this circuit satisfy our requirement.At last of this paper layout design optimization and circuit post simulation are completed.In the JAZZ 0.18μm Si Ge Bi CMOS, 3.3V operating voltage,this VGA achieves a dynamic gain range of 31 d B at 6~18GHZ with gain step 1d B,gain flatness less than 1.4d B moreover, acquires input and output matching with input matching less than-12 d B,output matching less than-12 d B and input 1d B compression point greater than 4.85 d Bm.