A tunable coaxial resonant probe for passive intermodulation imaging detection

Abstract

The application discloses a tunable coaxial resonant probe for passive intermodulation imaging detection, which comprises a probe feed connector, a PIM analyzer, a coaxial resonant cavity, a probe and a three-dimensional moving platform for adjusting the relative position between the probe and a measured object; the conductor end in the probe feed connector is inserted into the coaxial resonant cavity, the upper end of the probe is inserted into the coaxial resonant cavity, and there is a gap between the probe and the conductor end; the measured object is located below the probe; and the probe feed connector is connected with the PIM analyzer. The probe can meet the requirement of passive intermodulation high-sensitivity imaging detection.

Description

TECHNICAL FIELD

[0001] The present application relates to a tunable coaxial resonant probe, in particular to a tunable coaxial resonant probe for passive intermodulation imaging detection. BACKGROUND

[0002] Since the 1980s, mobile communication technology has maintained a rapid iterative development trend, and system architecture, signal processing, circuit design, and material technology have been constantly evolving. With the increasing number of users, the saturation of spectrum resources, and especially the development trend of co-siting technology in recent years, the interference problem caused by passive intermodulation has become one of the key basic problems that need to be solved in the field of mobile communication.

[0003] Passive intermodulation effect refers to the physical effect of linear combination of carrier frequencies excited by weak nonlinear passive devices, antennas, etc. under the excitation of two or more carrier frequencies. For example, under the excitation of carrier frequencies f1 and f2, new signals such as 2f1-f2 and 2f2-f1 may be excited due to passive intermodulation effect. These new signals are called passive intermodulation products. When the passive intermodulation products fall into the receiving frequency band of the communication system (i.e. passive intermodulation interference occurs), it may affect the normal work of the high-sensitivity receiver and cause system performance degradation. For example, when the base station antenna has passive intermodulation interference, it will directly affect the reception of the uplink signal of the communication terminal of the base station system, resulting in a smaller coverage range of the base station.

[0004] Common passive intermodulation interference sources in mobile communication systems include coaxial connectors, power dividers, antenna arrays, etc. From the physical mechanism, the nonlinear effects that cause passive intermodulation include metal contact nonlinearity and material nonlinearity. The typical case of metal contact nonlinearity causing passive intermodulation interference is a loose coaxial connector; the typical case of material nonlinearity causing passive intermodulation interference is an isolator made of ferrite material and a nickel-plated coaxial connector.

[0005] Radio frequency / microwave planar circuit (such as microstrip circuit) gradually obtains wide application in mobile communication system due to its low cost, low profile, light weight, easy integration and other advantages. Due to the effects of electro-thermal coupling, material nonlinearity and other effects, the problem of passive intermodulation interference of planar circuit becomes one of the main factors hindering its wide application in high-performance communication system. In order to study the generation mechanism and law of passive intermodulation of planar circuit, it is necessary to image and detect the passive intermodulation product. At present, the technical means for passive intermodulation imaging detection is to use a reflective coaxial probe. Whether it is an electrically coupled probe or a magnetically coupled probe, the probe itself does not have frequency selectivity, and the coupling degree is adjusted by controlling the position of the probe relative to the measured object. Since the frequency of the passive intermodulation product is very close to the carrier frequency, when the probe can effectively couple the intermodulation product, it can also effectively couple the carrier frequency, resulting in a large carrier frequency power entering the probe, increasing the intermodulation of the probe itself and reducing the dynamic range of the detection system, which is difficult to meet the needs of high-sensitivity imaging detection of passive intermodulation. SUMMARY

[0006] The purpose of the present application is to overcome the above-mentioned shortcomings of the prior art, and to provide a tunable coaxial resonant probe for passive intermodulation imaging detection, which can meet the needs of high-sensitivity imaging detection of passive intermodulation.

[0007] To achieve the above-mentioned purpose, the tunable coaxial resonant probe for passive intermodulation imaging detection comprises a probe feed connector, a PIM analyzer, a coaxial resonant cavity, a probe, and a three-dimensional moving platform for adjusting the relative position between the probe and the measured object.

[0008] The end of the conductor in the probe feed connector is inserted into the coaxial resonant cavity, the upper end of the probe is inserted into the coaxial resonant cavity, and there is a gap between the probe and the end of the conductor, the measured object is located below the probe, and the probe feed connector is connected to the PIM analyzer.

[0009] A piece supporting table is provided on the three-dimensional moving platform, and the measured object is placed on the piece supporting table.

[0010] The cross section of the coaxial resonant cavity is a T-shaped structure.

[0011] It also includes a base and a support, the three-dimensional moving platform is located on the base, the lower end of the support is fixed to the base, and the upper end of the support is connected to the coaxial resonant cavity.

[0012] The type of probe feed connector is L29 or N.

[0013] The coupling gap between the end of the conductor in the probe feed connector and the coaxial resonant cavity is optimized to reach the critical coupling state.

[0014] The probe feed connector is a silver-plated N-type connector.

[0015] The coaxial resonant cavity is silver-plated.

[0016] The present application has the following beneficial effects:

[0017] The probe for passive intermodulation imaging detection has the following advantages: the upper end of the probe is inserted into the coaxial resonant cavity, the length of the resonant section is adjusted by the insertion depth of the probe, the relative position between the probe and the measured object is adjusted by the three-dimensional moving platform, imaging detection is realized, the coupling degree is adjusted by the vertical displacement, the probe has tunability, the application range of the probe is increased, the coaxial resonant cavity is used to realize the selectivity of the probe frequency, the passive intermodulation signal level picked up by the probe is much higher than the carrier frequency level, and the detection sensitivity is improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 The present application has the following beneficial effects:

[0019] Fig. 2 The present application has the following beneficial effects:

[0020] Fig. 3 The present application has the following beneficial effects:

[0021] Fig. 4 The present application has the following beneficial effects:

[0022] Wherein, 1 is a PIM analyzer, 2 is a coaxial resonant cavity, 3 is a probe feed connector, 4 is a measured object, 5 is a piece holder, 6 is a three-dimensional moving platform, 7 is a base, and 8 is a probe. DETAILED DESCRIPTION

[0023] In order to better understand the present application by those skilled in the art, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments, and are not intended to limit the scope of the present application. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0024] The structural schematic diagram according to the disclosed embodiment of the present application is shown in the accompanying drawings. The drawings are not drawn to scale, in which some details are enlarged for the purpose of clear expression, and some details can be omitted. The shapes of various regions, layers and the relative size and position relationship therebetween shown in the drawings are only exemplary, and in practice, they can be deviated due to manufacturing tolerance or technical limitation, and a person skilled in the art can additionally design regions / layers with different shapes, sizes and relative positions according to actual needs.

[0025] With reference to Figs. 1 to 4 The tunable coaxial resonant probe for passive intermodulation imaging detection comprises a PIM analyzer 1, a probe feed connector 3, a coaxial resonant cavity 2, a probe 8, a support, a base 7 and a three-dimensional moving platform 6 for adjusting the position between the probe 8 and the measured object 4.

[0026] The conductor end in the probe feed connector 3 is inserted into the coaxial resonant cavity 2, the upper end of the probe 8 is inserted into the coaxial resonant cavity 2, and there is a gap between the probe 8 and the conductor end, a piece supporting table 5 is arranged on the three-dimensional moving platform 6, the measured object 4 is placed on the piece supporting table 5, the cross section of the coaxial resonant cavity 2 is a T-shaped structure, the three-dimensional moving platform 6 is located on the base 7, the lower end of the support is fixed on the base 7, the upper end of the support is connected with the coaxial resonant cavity 2, and the probe feed connector 3 is connected with the PIM analyzer 1.

[0027] Specifically, in actual operation, according to the requirements of detection frequency and dynamic range of passive intermodulation level in actual application scenarios, the type of the probe feed connector 3 and the length, inner diameter and material of the coaxial resonant cavity 2 are determined, the type of the probe feed connector 3 is L29 type or N type, and the coupling gap between the conductor end in the probe feed connector 3 and the coaxial resonant cavity 2 needs to be optimized to reach the critical coupling state. In order to realize imaging detection and adjust the coupling degree through vertical displacement, the measured object 4 is fixed on the three-dimensional moving platform 6, so as to realize two-dimensional scanning of the measured object 4 located directly below the probe 8. The input port of the measured object 4 feeds in double carrier frequency signals, the output port of the measured object 4 is connected with a high-power low intermodulation load, and then the detection of intermodulation signals is realized through the PIM analyzer 1. The relative position between the probe 8 and the probe 8 is realized through software control, and finally the imaging detection is completed.

[0028] In order to reduce the intermodulation of the probe itself, the following measures can be taken: the probe feed connector 3 is a silver-plated N type connector, a coaxial resonant cavity 2 with a larger diameter is used to reduce the surface circuit density and realize the suppression of intermodulation, the silver-plated treatment of the coaxial resonant cavity 2 is performed to realize the increase of Q value to increase the frequency selectivity and reduce the intermodulation. The frequency selectivity of the probe can also be realized by using different resonant modes.

[0029] The upper end of the probe 8 is nested in the coaxial resonant cavity 2, so that the resonant section length can be tuned within a certain length range, similar to a mechanical coaxial phase shifter; through mechanical structure design.

[0030] It should be noted that the present application introduces a resonant coaxial probe to realize the frequency selectivity of the probe, so that the passive intermodulation signal level picked up by the probe is much higher than the carrier frequency level, thereby realizing the improvement of detection sensitivity; in addition, to realize the tunability of the probe, the following approaches are proposed: the physical length of the resonant section is adjustable to adapt to passive intermodulation detection at different frequency points, the coupling degree is realized through the three-dimensional moving platform 6 to adapt to different objects to be measured, and the resonant characteristics of the probe are realized through the replaceable flange to adapt to different objects to be measured. Compared with the existing test method, the main improvement of the present application is that the frequency selectivity is realized by introducing the resonant coaxial probe to increase the system detection sensitivity, and the tunability of the probe is realized through multiple approaches to increase the applicable scene range of the probe.

[0031] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: the specific embodiments of the present application can still be modified or replaced by the same, without departing from the spirit and scope of the present application. Any modification or equivalent replacement, which should be covered within the protection scope of the claims of the present application.

Claims

1. A tunable coaxial resonant probe for passive intermodulation imaging detection, characterized in that, Includes a probe feed connector (3), a PIM analyzer (1), a coaxial resonant cavity (2), a probe (8), and a three-dimensional moving platform (6) for adjusting the position between the probe (8) and the test piece (4). The conductor end inside the probe feed connector (3) is inserted into the coaxial resonant cavity (2), the upper end of the probe (8) is inserted into the coaxial resonant cavity (2), and there is a gap between the probe (8) and the conductor end. The test piece (4) is located below the probe (8), and the probe feed connector (3) is connected to the PIM analyzer (1). The coupling gap between the inner conductor end of the probe feed connector (3) and the coaxial resonant cavity (2) is optimized to reach the critical coupling state; The probe feed connector (3) is a silver-plated N-type connector; The coaxial resonant cavity (2) is silver-plated.

2. The tunable coaxial resonant probe for passive intermodulation imaging detection according to claim 1, characterized in that, A support platform (5) is provided on the three-dimensional moving platform (6), and the test piece (4) is placed on the support platform (5).

3. The tunable coaxial resonant probe for passive intermodulation imaging detection according to claim 2, characterized in that, It also includes a base (7) and a bracket. The three-dimensional moving platform (6) is located on the base (7), the lower end of the bracket is fixed on the base (7), and the upper end of the bracket is connected to the coaxial resonant cavity (2).

4. The tunable coaxial resonant probe for passive intermodulation imaging detection according to claim 1, characterized in that, Replace the type N of the probe feed connector (3) with the type L29 of the probe feed connector (3).

5. The tunable coaxial resonant probe for passive intermodulation imaging detection according to claim 1, characterized in that, The cross-section of the coaxial resonant cavity (2) is a T-shaped structure.

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