Jun Fu

Bio: Jun Fu is an academic researcher from Tsinghua University. The author has contributed to research in topics: Heterojunction bipolar transistor. The author has an hindex of 1, co-authored 1 publications receiving 11 citations.

The Influence of Microwave Pulse Width on the Thermal Burnout Effect of an LNA Constructed by the SiGe HBT

Abstract: This paper presents the influence of the pulse width on the thermal burnout effect of a low-noise amplifier (LNA) constructed by a silicon–germanium heterojunction bipolar transistor (SiGe HBT) when it is injected by microwave pulses. Based on the characteristics of microwave pulses and the structure of the SiGe HBT, a theoretical model to predict the impact of the pulse width and power on the thermal burnout effect of the LNA is established by solving the heat conduction equation. The derivation of the theoretical model requires the pulse width less than a microsecond level. Using at least two groups of simulated or measured results to fit the coefficients, the proposed theoretical model can predict the other effect of the pulse width, which can greatly reduce the experimental costs and guide the rational selection of the pulse width in numerical simulations. At last, the theoretical model is verified by numerical simulations and experimental measurements. The results show that within the scope of pulse width (less than the microsecond level) the burnout power threshold can be effectively reduced by increasing the pulse width.

Thermal Burnout Effect of a GaAs PHEMT LNA Caused by Repetitive Microwave Pulses

Abstract: The thermal burnout effect of a gallium arsenide (GaAs) pseudomorphic high electron mobility transistor (PHEMT) low-noise amplifier (LNA) caused by repetitive microwave pulses is studied by theoretical analyses, simulations, and experiments. The theoretical model for thermal burnout under a single microwave pulse injection is first acquired by analyzing the power absorption in the electrical procedure and the heat distribution in the thermal procedure. By adopting two new assumptions and using the linear superposition theorem, the theoretical model for thermal burnout under a repetitive microwave pulse injection is acquired by further extension. Through derivation, the analytical relationship among the thermal burnout power threshold, the pulsewidth in a cycle, the pulse repetition frequency (PRF) and the pulse number is acquired. Because some assumptions and approximations are adopted, both the pulsewidth in a cycle and the total repetitive microwave pulselength must be between 10-ns scale and 1-μs scale. It shows that the theoretical results agree well with the simulation and experimental results. A minimum of two sets of data by experiment or simulation are needed to fit the analytical relationship. Therefore, experimental or simulation costs can be substantially reduced, and a helpful reference for

Analysis of Design Parameters Reducing the Damage Rate of Low-Noise Amplifiers Affected by High-Power Electromagnetic Pulses

Abstract: To protect the RF front end from electronic warfare, many studies have focused on damage phenomena of the low-noise amplifiers (LNAs). Existing studies have focused on the damage points of semiconductor devices because the peripheral circuit elements of LNAs are less susceptible to breakdown than nonlinear elements. However, their theoretical analysis is insufficient to explain the damage mechanism of LNAs under conditions such as changes in input power, frequency, and design parameters. To analyze the relationship between damage rate and parameters of the peripheral circuit of an LNA, this paper proposes a new definition of the power absorbed to a nonlinear element when input power to an LNA is very high by high-power electromagnetic pulses. In addition, LNAs having different input impedances and output impedances are designed to verify the power absorption. From the results, this paper identified parameters that increase the damage rate of LNAs, and suggested designs to reduce the damage rate.