直接采样微波辐射计统计模型及定标研究

The Statistic Model and Calibration Research of Direct Sampling Microwave Radiometer

直接采样微波辐射计对射频信号直接采样,是一种结构简单的数字辐射计。受高速、宽带模数转换器(ADC)采样、非理想量化的影响,直接采样数字接收机输出信号的统计特性将改变,传统辐射计的定标方法不再完全适用于直接采样微波辐射计。论文分析ADC的非理想量化,建立直接采样数字接收机输出信号的统计模型和直接采样微波辐射计的定标方程;实验采用多点定标方法对直接采样微波辐射计进行定标,并用三次样条插值拟合直接采样数字接收机输出信号功率估计值与输入噪声温度之间的转移曲线,提高直接采样微波辐射计的测量精度。

Direct sampling microwave radiometer （DSMR） is a digital radiometer of simple structure, which directly samples radio frequency signals. The output signal statistic characteristics of direct sampling digital receiver （DSDR） will be changed by the impact of sampling, non-ideal quantization of high-speed, wide-band analog-to-digital converter （ADC）, so the calibration method of traditional radiometer is not fully applicable to the DSMR. This paper analyzes the non-ideal to quantify of ADC, to model the output signal statistics of DSDR and deduce the calibration equation of DSMR. In experiment, the methods of multi-point calibration and cubic-spline interpolation will be introduced to calibrate the DSMR and to fit the transfer function between DSDR output signal power estimated and input noise temperature, respectively, which improved the measurement accuracy of DSMR.