边缘电容多项式的系数

嗨，我正在开展一个需要表征SOLT校准套件的项目。
该套件代表从3.5mm SMA连接器到长度为20mm的微带线的过渡。
对3GHz以上频率的测量需要将开放边缘电容模型化为3阶多项式。我执行以下步骤：在测试电缆末端进行1- 1端口校准（85033D校准套件）。
2-连接短标准（20mm 50欧姆微带线由2个并联的50欧姆电阻器结束）并使端口扩展直到180度相移。
3-断开短标准并连接开放标准。
4-调整延迟直到相位为负（整个波段的负相位）。
5-提取格式化的RI数据并跟踪并行电容值作为频率的函数。
6-使用数学工具拟合图形以评估电容多项式的系数。
注意，如果我们想要整个工作频带的负相位，则开路相位线路既不是平坦的也不是线性的，并且在频带末端（6 GHz）达到-28度。
我的问题是电容多项式的系数值很大。
（C0 = 38.33E-15; C1 = 79676.1E-27; C2 = -35687.91E-36; C3 = 4270.35E-45）。
VNA不接受超过10000或小于-10000的值。
实际上，我试图将乐队划分为两个子乐队，但同样的问题也会出现。
此外，我试图最小化频带以实现平坦相位（小于1度的变化），但也出现同样的麻烦。
谢谢你的帮助。



     以下为原文

  Hi,

I'm working on a project that needs the characterization of a SOLT calibration kit.
The kit represents a transition from 3.5mm SMA connector to a microstrip line of length 20mm.
The measurement for frequencies above 3GHz requires the modelization of the open fringing capacitance as a polynomial of order 3.

I perform the following steps:

1- 1-port calibration at the end of the test cable (85033D calibration kit).
2- Connect short standard (20mm 50ohm microstrip line ended by 2-parallel 50ohm resistors) and make port extension until 180 degrees phase shift.
3- Disconnect short standard and connect the open one.
4- Adjust the delay until the phase is negative (Negative phase across the whole band).
5- Extract the formatted RI data and trace the parallel capacitance values as a function of frequency.
6- Use mathematical tool to fit the graph in order to evaluate the coefficients of the capacitance polynomial.

Note that the open phase trace is neither flat nor linear and reaches -28 deg at the end of the band (6 GHz) if we want negative phase for the whole operating band.

My problem is that the values of the coefficients of the capacitance polynomial are big.
(C0=38.33E-15; C1=79676.1E-27; C2=-35687.91E-36; C3=4270.35E-45).
The VNA doesn't accept values more that 10000 or less than -10000.

Actually, I tried to divide the band into two sub-bands, but that same problem results.
Moreover, I tried to minimize the band in order to achieve flat phase (less than 1 deg variation) but also the same trouble arises.

Thanks for your help.