DEPARTMENT OF TECHNOLOGY Design a Highly Linear Power Amplifier Based on HBT
نویسندگان
چکیده
The RF power amplifier (PA) is one of the critical components in the 802.11 transceivers, and it is expected to provide a suitable output power at a very good gain with high efficiency and linearity. However, present-day telecommunication device technology is not well suited to the requirements of optical data communication. Digital CMOS is the most used technology in RF applications, nowadays; nevertheless HBT gives more advantage in terms of higher power gain and better thermal capabilities. In this thesis we are designing, manufacturing and testing a power amplifier based on HBT technology, in order to investigate its characteristics and performance for power amplifier applications and to prove that HBT power amplifiers can be widely used for this kind of applications. Therefore we will study the HBT technology, as well as the transistor characteristics and HBT structure and properties. Since we are designing a power amplifier for WIFI applications, we will also give an overview of WIFI and present the IEEE 802.11 physical layer standard and applications and features of it, and then we will present the advantages and disadvantages of WIFI and the specifications of the power amplifier to be designed and manufactured. This thesis will present a Class A PA design and discuss its performance. We will study parameters which quantify the various aspects of amplifier performance such as 1-dB compression point, 3 rd order intercept point, intermodulation distortion; efficiency and adjacent channel power ratio. The Class A amplifier was designed using NEC HBT (Heterojunction Bipolar Transistor) transistor models and its performance was simulated using ADS. Various procedures involved in the design of the Class A amplifier such as DC simulation, bias point selection, Load-pull characterization, input and output matching circuit design and the design of a bias network are explained. Memory effects in Power Amplifiers are also discussed and found to be very small, with less than 0.2 dB variation in the output at fundamental frequencies. The power gain, linearity, efficiency, power added efficiency, the input and output reflection coefficients, the Adjacent Channel Power Ratio (ACPR) and the memory effects of the PA SAAD PAUL M.Sc Thesis 05/06 Design a Highly Linear Power Amplifier Based on SiGe HBT were measured and have been found to be satisfying and meet the specifications for WIFI applications. The efficiency of 21% was found, which is in the practical efficiency range for class A PA. The Linearity of the power amplifier …
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