Research On SiGe HBT And Their Applications In Circuit Of LNA

As an important component of receiver front-end, low noise amplifier plays an critical role in the whole system while the performance of its gain, noise figure and linearity is closely related to the receiver’s performance and sensitivity. The fast development of modern wireless communication technology, demands faster data transmission rate and larger band-width, and the performance of Ultra-wide band LNA need to be improved constantly.As a new category of radio-frequency device, the SiGe Hetero junction bipolar transistors are gradually used in the circuit design of LNA, which is with almost the same performance as a GaAs one in gain, noise feature and frequency performance. The SiGe device is compatible with current Si processes, and has excellent characteristics of larger band-width, lower power consumption and cost.Both the electrical properties and noise feature of SiGe HBT and the Low Noise amplifier of SiGe HBT circuit are analyzed and discussed in this thesis. The main job includes:(1) A theoretical analysis of SiGe HBT device is studied. With a review into the fundamental principles of hetero-j unction, the DC-performance and frequency performance, the relationship between multiple SiGe HBT device structure parameters and the transistor performance are analyzed and discussed. The results indicate that HBT has uniquely excellent noise and frequency performance in comparison with traditional bi-polar junction transistor. In this case, the frequency performance and the noise feature of transistor could be significantly improved with a reasonable optimized design of transistor structure parameters. Meanwhile, and the device has maximized current density and breakdown voltage, as well as enough current gain and characteristic frequency.(2) A deep research into the multiple HBT models is carried out in the second chapter, such as the Ebers-Moll model, the Grammel-Poon model, the SPICE model and the noise model. The results reveal that higher dopant concentration in the base-area and lower dopant concentration in the emitter-area lead to lower noise figure of the SiGe HBT circuit. Meanwhile, smaller base-area width which means shorter transit time could improve the transistor’s cut-off frequency and parasitic resistance.The following simulation of SiGe HBT device based on ADS software reveals that the minimum noise figure is non-linearly increasing with the increasing input working frequency. (3) An introduction is made including the multiple parameters of Low Noise amplifier circuit, and a theoretical analysis into the bias circuit and matching problem. The indicator parameter is both the foundation and goal of Low Noise amplifier circuit design, of which the first step is to choose topological structure. Balanced amplifier enjoys good stationary and linearity, yet ideal noise figure; negative feedback amplifier enjoys high stationary and more excellent gain flatness in cost of gain itself. The bias circuit provides both suitable biased-voltage and biased-current for transistor. Inductance bias circuit is characterized by good noise performance and linearity yet large circuit area and additional waste of power; resistance bias circuit out-performs the former in circuit area, but loses in noise feature and linearity. The mixed bias circuit bears the most excellent performance in noise feature, power consumption and linearity.(4) A Low Noise amplifier is designed based on JAZZ0.35um SiGe processing technology and simulated based on ADS software with the working frequency spanning between3.1-10.6GHz. The common-emitter structure is used in input stage design, with emitter series feedback inductance for input matching. The Darling structure is used in secondary stage design to provide suitable gain for input signal. Finally, a series of task including designing, optimizing and simulating is carried out based on the software of ADS2006. Results show noise figure of the amplifier is below3.3dB with working voltage of5V in3.1-10.6GHz, gain greater than25.1dB, Noise figure below3.3dB, S11and S22below-lOdB, VSWRin and VSWRout below1.9, and power consumptions32mW.The performance of overall circuit is affected by the gain of the device performance, noise characteristics and the design of circuit. For the device, the influencing factors include the structure and process and other factors. For the circuit, the impact of factors include the circuit topology, the bias circuit, and the matching circuit. SiGe HBT model and noise theory analysis are studied in this thesis to provide theoretical guidance for the circuit design. Then analysis and simulation of an application in the UWB frequency band LNA circuit by the theoretical of SiGe HBT LNA circuit are carried out. This thesis may provide theoretic guide for the design of SiGe HBT LNA circuit.