随着航空航天、深空探测、量子计算等前沿领域对电子系统在极端温度环境下工作的需求日益增长，锗硅异质结双极晶体管（SiGe HBT）因其优异的低温性能和与硅基工艺的兼容性，成为宽温区高性能集成电路的关键器件。然而，现有商用集约模型在极低温条件下精度不足，难以准确描述器件行为。本文基于Mextram模型架构，提出了一种适用于80K至400K宽温范围的SiGe HBT集约模型。通过对主电流模型和基极电流模型中理想因子与饱和电流的温度依赖性建模，并引入异质结势垒效应模型，显著提升了模型在低温下的仿真精度。进一步设计了涵盖直流与射频特性的宽温测试方案，并提出了系统化的参数提取流程。实验结果表明，所提出的模型在宽温范围内与实测数据吻合良好，平均相对误差小于20%，验证了模型的有效性与实用性。

With the rapid development of frontier fields such as aerospace, deep space exploration, and quantum computing, electronic systems are required to operate reliably under extreme temperature conditions, particularly at cryogenic temperatures. Silicon-Germanium Heterojunction Bipolar Transistors (SiGe HBTs) have emerged as a promising candidate for wide-temperature-range analog/mixed-signal integrated circuits due to their high performance and compatibility with silicon-based processes. However, existing commercial compact models, such as HICUM and Mextram, exhibit insufficient accuracy at cryogenic temperatures, limiting their applicability. This paper presents an improved Mextram-based compact model for SiGe HBTs operating from 80K to 400K. Key enhancements include temperature-dependent modeling of ideality factors and saturation currents in both the main current and base current models, as well as the incorporation of a heterojunction barrier effect model. A comprehensive characterization methodology and parameter extraction strategy for DC and RF behaviors across the wide temperature range are also proposed. Experimental validation shows that the proposed model achieves good agreement with measured data, with an average relative error of less than 20%, demonstrating its accuracy and practicality for extreme-environment circuit design.