[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.
[0035] A method for reducing the fringe capacitance of the opener calibration piece, the capacitance of the opener calibration piece is set as a coaxial gradient capacitance, wherein the dimensions of the inner conductor and the outer conductor at the beginning of the axis of the opener calibration piece are respectively set to be the same as those of the vector network analyzer The matching size of the ports, the size of the inner conductor and the outer conductor at the end of the axis of the opener calibration piece is set to be smaller than the size of the inner conductor and the outer conductor at the beginning of the axis;
[0036] The distance from the start end of the axis to the end end of the axis is l; z is the distance between any point on the axis between the start end of the axis and the end end of the axis and the start end of the axis, and z≤l; the diameter of the inner conductor is represented by d(z) , the diameter of the outer conductor is represented by D(z), and the impedance of the coaxial tapered capacitor Among them, μ is the magnetic permeability, ε is the dielectric constant; the ratio of the outer conductor diameter D(z) to the inner conductor diameter d(z) is a constant value.
[0037] The characteristic impedance analysis of the coaxial gradient capacitor is as follows:
[0038] Take a section of the transmission line with a very small length, and its length is Δz, then its equivalent circuit is as follows figure 1 As shown, set R(z) as the series resistance per unit length at z, L(z) as the series inductance per unit length at z, G(z) as the parallel conductance per unit length at z, C(z ) is the parallel capacitance per unit length at z, i(z,t) and v(z,t) are the current and voltage loaded on this tiny transmission section respectively, so at Δz, resistance, inductance, conductance, capacitance The values are RΔz, LΔz, GΔz, and CΔz; i(z+Δz,t), v(z+Δz,t), respectively, are the current and voltage signal functions at the output end, then this short transmission line satisfies the telegraph equation, namely:
[0039]
[0040]
[0041] in, When it is assumed that the transmission line has approximately zero loss (for the open circuit device calibration part, the loss can be ignored when calculating the impedance), at this time, the impedance of this tiny section of the transmission line is:
[0042]
[0043] in:
[0044]
[0045] μ is the magnetic permeability, D(z) is the diameter of the outer conductor at z, d(z) is the diameter of the inner conductor at z, and ε is the permittivity. thereby
[0046]
[0047] That is, the characteristic impedance is only related to the ratio of the diameter of the outer conductor to the diameter of the inner conductor. When the value of the transmission line D(z)/d(z) is constant, the impedance of the transmission line is also consistent.
[0048] Specifically, the function of the outer conductor diameter D(z) and the inner conductor diameter d(z) is set as a straight line function.
[0049]Specifically, on the axis of the opener calibrator, the distance from the end of the axis of the inner conductor to the start of the axis is smaller than the distance from the end of the axis of the outer conductor to the start of the axis, that is, the length of the outer conductor is greater than the length of the inner conductor. On the basis of the above structure, the influence of the fringe capacitance on the measurement result is further reduced, and the measurement accuracy of the open circuit calibration part is improved.
[0050] An open circuiter calibration kit such as figure 2 and image 3 As shown, it includes an outer conductor 1 and an inner conductor 2. The outer conductor 1 is a hollow shell with a conical chamber 3 inside; the inner conductor 2 is a solid conical core; the inner conductor 2 is coaxially installed on the cone of the outer conductor 1. In the cavity 3, and the end faces of the starting ends of the outer conductor 1 and the inner conductor 2 are large-diameter ends, and they are on the same end face, wherein the inner diameter of the outer conductor 1 on any radial section along the axial direction of the opener calibrator The ratio to the outer diameter of the inner conductor 2 is a constant value. Preferably, the structures of the outer conductor 1 and the inner conductor 2 are both conical.
[0051] Specifically, the opener calibration part also includes a shielding cover 4, which is fixedly installed on the end end of the outer conductor 1, and the shielding cover 4 is provided to prevent electromagnetic waves from radiating to the outside. The shape of the shielding cover 4 is not specifically limited in this embodiment. The structure of the shielding case 4 in the existing opener calibrator can be used in this embodiment. Preferably, the shape of the shielding case 4 is a cylinder.
[0052] Specifically, the outer conductor 1 of the opener calibration piece is provided with an external thread 5, and the end of the inner conductor 2 is provided with a socket 6 at the beginning end, and the opener calibration piece can be screwed and installed on the port of the vector network analyzer through the external thread 5 Above, the pin of the vector network analyzer port is inserted into the jack 6, and the structure of the beginning end of the opener calibration part is the same as that of the coaxial opener calibration part in the prior art, and can be directly installed on the existing vector network analyzer For testing and calibration, it is not necessary to specially set up a vector network analyzer port matching this embodiment. Since the external shape of the opener calibrator of this embodiment is a conical structure, and a shielding cover 4 is arranged at the end of the conical structure, since the end face of the shielding cover 4 is larger than the end face of the conical structure, it is easy to be damaged or damaged during use. In the case of breaking, it is preferable to cover the outside of the opener calibrator with an insulating material to change the external shape into a cylindrical shape. When this shape is used, it is easy to pull out and plug in, and it is not easy to break, which increases the calibration of the opener. service life of the parts.
[0053] Specifically, such as image 3 As shown, the end of the outer conductor 1 and the inner conductor 2 of the opener calibrator are arranged flush with each other.
[0054] Specifically, such as Figure 4 As shown, on the axis of the opener calibrator, the distance from the end to the start of the inner conductor 2 is smaller than the distance from the end to the start of the outer conductor 1, that is, the length of the outer conductor 1 is greater than the length of the inner conductor 2. This structure On the basis of the above structure, the influence of the fringe capacitance on the measurement result is further reduced, and the measurement accuracy of the open circuit calibration part is improved.
[0055] Specifically, the opener calibrator also includes an internal insulating support 7, and the inner conductor 2 is fixed in the tapered cavity 3 of the outer conductor 1 through the internal insulating support 7. In this embodiment, the specific shape of the internal insulating support 7 It is not limited, it only needs to achieve mutual fixation between the inner conductor 2 and the outer conductor 1, such as Figure 5 and Image 6 Shown are the two fixing methods listed in this embodiment; the material of the internal insulating support frame can be insulating material, preferably, it is made of polytetrafluoroethylene material.
[0056] Specifically, in order to make the inner conductor 2 and the outer conductor 1 of the open circuit calibration piece have better electrical conductivity, the materials of the inner conductor 2 and the outer conductor 1 are both set to brass, and the inner conductor 2 and the outer conductor 1 Gold plated finish on the surface.
[0057] The entire open circuit device calibration part, the capacitor is designed as a coaxial gradient capacitor, so that the cross-sectional area of the starting end of the inner conductor and the outer conductor is larger than the cross-sectional area of the ending end, and the cross-sectional area of the ending end is reduced, which can effectively reduce the edge effect of the capacitor and make the vector network When the analyzer is calibrated, there will be no large deviation, and the measurement error of the vector network analyzer to the external instrument will be further reduced.
[0058] The present invention has been further described above with the help of specific embodiments, but it should be understood that the specific description herein should not be construed as limiting the spirit and scope of the present invention. Various modifications made in the embodiments all belong to the protection scope of the present invention.
