CN110221142B - Nonlinear test positioning method and device based on passive intermodulation radiation field - Google Patents
Nonlinear test positioning method and device based on passive intermodulation radiation field Download PDFInfo
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Abstract
The invention discloses a nonlinear test positioning method and device based on a passive intermodulation radiation field. The method for testing and positioning uses a slotted coaxial and different intermodulation testers to be connected in a combined manner, a slot is formed on an outer conductor of the slotted coaxial and serves as a carrier transmitting window and an intermodulation receiving window, the slotted coaxial and the intermodulation tester are connected to achieve carrier transmitting and intermodulation signal receiving, a carrier transmitting port and an intermodulation receiving port serve as physical reference points, and the physical reference points are used for achieving the relative position prediction of power measurement of intermodulation abnormal points. The invention can improve the accuracy and efficiency of intermodulation test.
Description
Technical Field
The invention relates to the technical field of microwave circuit device detection, in particular to a nonlinear test positioning method and device based on a passive intermodulation radiation field.
Background
When two or more carrier signals pass through components with non-linear responses, new signals different from the carrier frequency are generated, a phenomenon known as passive intermodulation. Passive Intermodulation (PIM) refers to a spurious signal generated by mixing two or more frequencies of transmitted carriers in a passive nonlinear device, which has caused interference to modern high-power, multi-channel communication systems.
The method for testing the passive intermodulation radiation field is mainly based on an antenna pair structure, a carrier antenna is used for irradiating a piece to be tested, another receiving antenna with selective characteristics is used for receiving an intermodulation signal radiated by the piece to be tested, and the intermodulation level received by the receiving antenna is compared with a background level to realize the test of the intermodulation power level and the positioning of an intermodulation power point. In the actual operation process of the method, the following problems exist:
1. in order to distinguish intermodulation source points of a to-be-tested element, an actual antenna is often a high-gain narrow-band antenna, so that the test bandwidth is limited, the test antenna needs to be correspondingly replaced after the frequency band is replaced, and uncertainty among antenna connections is introduced for many times.
2. For a metal part to be measured with a special structure, carrier irradiation is difficult due to the singularity of the structure of the part to be measured. Such as isolation and resonance structures with electromagnetic shielding and frequency selection, so that the carrier wave cannot be fed with full power, and thus individual abnormal nonlinear source points cannot be discriminated.
3. The current PIM analyzer combines a signal amplification part and a weak signal detection part, so that an occupied large signal source cannot be multiplexed, and the waste of instrument resources is caused.
Disclosure of Invention
The invention aims to provide a nonlinear test positioning method and device based on a passive intermodulation radiation field to solve the problems of narrow band, air attenuation and difficult carrier irradiation of the conventional passive intermodulation test based on an antenna radiation field, so as to improve the accuracy and efficiency of the intermodulation test.
The technical scheme adopted for realizing the purpose of the invention is as follows:
a nonlinear test positioning method based on a passive intermodulation radiation field uses a slotted coaxial and different intermodulation testers to be connected in a combined mode, a slot is formed in an outer conductor of the slotted coaxial and serves as a carrier transmitting window and an intermodulation receiving window, the slotted coaxial and the intermodulation testers are connected to achieve carrier transmitting and intermodulation signal receiving, a carrier transmitting port and an intermodulation receiving port serve as physical reference points, and power measurement relative position prediction of an intermodulation abnormal point is achieved through the physical reference points.
Preferably, the clamping structure is used for being connected with the end face to be detected through the fastening screw, and the electromagnetic radiation intensity and the direction of the end face to be detected are controlled by controlling the size and the shape of the slot.
The slotting coaxiality is divided into single-end slotting coaxiality and periodic slotting coaxiality;
the single-end slotted coaxial termination is matched with a low intermodulation load or a short-circuit surface with a slotted 1/4 wavelength at the section closest to the end is used for manufacturing a radiation and receiving probe which is used as a slotted coaxial probe, and a carrier irradiation area can be changed by moving the position of a window;
the periodic slotted coaxial line and the single-end slotted coaxial line are used independently or in combination, and are connected with different intermodulation testers in a combined mode to achieve contact PIM testing.
Preferably, the single-ended slotted coaxial access single-port reflective intermodulation tester enables the single-ended slotted coaxial to simultaneously realize the functions of carrier wave transmission and intermodulation signal reception; the periodic slotted coaxial and the single-end slotted coaxial are combined together, or when the two slotted coaxial are combined together to form a double-slotted coaxial combination according to the periodic slotted coaxial, one of the two slotted coaxial is used for transmitting carrier waves, and the other slotted coaxial is used for receiving and detecting intermodulation signals.
Preferably, one end of the coaxial probe is connected with one end of the high-power low-intermodulation load, the coaxial probe is provided with a slot, the coaxial probe is used as a carrier transmitting probe and an intermodulation receiving probe, the coaxial probe is connected to a single-port reflection intermodulation tester, and the power value of an intermodulation abnormal point and the positioning of the abnormal point are realized by moving the position of the slot and changing the irradiation position of the carrier.
Preferably, a periodic slotted coaxial is used as a carrier transmitting and intermodulation receiving coaxial, two ends of the periodic slotted coaxial are connected to a transmission and reflection intermodulation tester, the periodic slotted coaxial and the reflection intermodulation coaxial are laid along a suspected intermodulation abnormal point, the difference value of the transmission and reflection intermodulation values is read and compared with a calibration value before testing, and the power value testing and the abnormal point positioning of the intermodulation abnormal point are realized based on the following formula:
in formula (II), PIM'r，PIM'fRespectively representing the reflected power value and the transmitted intermodulation power value read and displayed by using a calibration radiation PIM source arranged at the first slit at the ends of the coaxial two sides of the slit before testfPIM for the value of the transmit intermodulation power read during the testrFor the values of the reflected power read during the test,/f，lrRespectively, the distance of the intermodulation anomaly point from the transmission test port and the distance from the reflection test port, ltotIndicating the total coaxial length of the slot.
Preferably, a periodic slotted coaxial is used as a carrier receiving coaxial, connected to a reflection intermodulation test port of a transmission and reflection intermodulation tester, and laid along a suspected intermodulation abnormal point; and scanning the suspected intermodulation abnormal point by using another single-ended slotted coaxial probe, comparing the measured transmission intermodulation with the reflection intermodulation value, and testing the power value of the intermodulation abnormal point and positioning the abnormal point by the fluctuation of the transmission intermodulation value.
Preferably, a periodic slotted coaxial is used as a carrier receiving coaxial, connected to a reflection intermodulation test port of a transmission and reflection intermodulation tester, and laid along a suspected intermodulation abnormal point; forming a radiation array based on a leakage coaxial by using another periodic slotted coaxial for carrier irradiation; the distance and the phase of an intermodulation signal on the periodic slotted coaxial relative to the double-connection port are tested by the intermodulation tester with carrier separation, the position of an intermodulation abnormal point can be obtained by comparing a coaxial length scale, an intermodulation attenuation value of unit length is calculated through insertion loss after phase verification, and the absolute power value of the intermodulation test point is inversely calculated.
The invention also aims to provide a device for nonlinear test positioning based on a passive intermodulation radiation field, which comprises an intermodulation tester coaxially matched with the slot, wherein the amplitude and position detection of an intermodulation abnormal point is realized through two-way signal acquisition and self-calibration; the intermodulation tester is provided with two paths of intermodulation receiving paths which are respectively used for amplitude attenuation and phase verification of intermodulation signals by taking ports at two ends of a slotted coaxial as a reference, and a single intermodulation detection path for amplitude detection of the intermodulation signals comprises a filter, a low-noise amplifier, a directional coupler, a phase shifter, an attenuator and a mixing phase discriminator; after the two paths of intermodulation detection signals are modulated by the attenuator to have equal amplitude, the two paths of intermodulation detection signals enter a frequency mixing phase discriminator to carry out phase comparison to obtain relative phase information of the two paths of intermodulation signals, and the phase shifter is used for correcting the phase asymmetry in the signal channel when the intermodulation tester is subjected to self-calibration; the relative phase information of the two paths of bidirectional intermodulation signals is used for self-checking of amplitude test; by obtaining amplitude and phase information from the dual ports, the power values and relative positions of the intermodulation points are predicted according to the following relations:
lf+lr＝ltot
ILu＝abs(PIM'f-PIM’r)/ltot
PIMabs＝lf×ILu+PIMf＝lr×ILu+PIMr
in the formula (II)uIndicating loss of slotted coax per unit length with respect to intermodulation signals, PIMabsIndicating intermodulation anomaly powerM is an integer, Δ φf-rPhase difference of transmission and reflection intermodulation:
the characteristic of the slotted coaxial broadband used for the test is suitable for multi-band frequency-sweeping type intermodulation test, and meanwhile, the coaxial broadband can be suitable for intermodulation detection occasions with specific structures by changing the coaxial diameter and length.
The method for testing and positioning can avoid the interference of a singular structure of a piece to be tested on an electromagnetic radiation field, has broadband test characteristics similar to those of a coaxial structure compared with an antenna radiation test method, and can position an intermodulation point while testing an intermodulation power value.
The method for testing and positioning based on slotting coaxiality can realize the modularized passive intermodulation test with lower cost and realize the multiplexing of an intermodulation tester. On the occasion of having a whole set of intermodulation test equipment, the method for slotting coaxial test positioning can be compatible with the existing intermodulation test equipment, and the test and positioning of intermodulation abnormal points are realized.
The intermodulation test positioning device provided together with the coaxial test positioning method can enable a high-power signal source to be independently controlled and realize multiplexing.
Drawings
Fig. 1-a is a schematic view of a regularly slotted coaxial cable.
Fig. 1-b is a schematic illustration of slotted coaxial electromagnetic field radiation.
Fig. 1-c is a schematic view of the splayed slotted coaxial.
Fig. 2-a is a schematic view of a simple slotted coaxial made by low PIM coaxial lines.
Fig. 2-b, fig. 2-c, and fig. 2-d are schematic views of PIM test tools implemented in cooperation with a bolt fastening yoke, respectively.
Fig. 3 is a diagram of the effect of using a slotted coaxial line to access a single-port reflective intermodulation tester.
Fig. 4 is a block diagram of a dual mode intermodulation tester.
Fig. 5 is a block diagram of an intermodulation test based on a single regular slotted coaxial and dual mode intermodulation tester.
Fig. 6 is a block diagram of the dual mode intermodulation tester after access with a regularly slotted coaxial using a slotted coaxial probe.
Fig. 7 is a schematic diagram of an intermodulation tester based on carrier separation and intermodulation detection of a double slotted coax.
Fig. 8 is a block diagram of an intermodulation tester receiver based on a carrier separation mode.
Fig. 9 is a schematic diagram of intermodulation detection of an intermodulation tester and a single slotted coaxial probe based on carrier separation.
In the figure: the coaxial cable comprises an inner conductor 1, an outer conductor 2, a dielectric layer 3, a slotted window 4, an insulating skin 6, an insulating layer 7, an outer conductor 8, a through hole 9, a fastening bolt of a clamping tool, a termination test surface 10, a leakage port 11, an attenuator 12, a directional coupler 13, a phase shifter 14 and an attenuator 15, wherein the inner conductor is a standard slotted coaxial conductor, the outer conductor is a standard slotted coaxial conductor, the dielectric layer is arranged between the inner conductor and the outer conductor, the slotted window 4 is a standard slotted coaxial conductor, the insulating skin is a standard slotted coaxial conductor, the insulating layer is a low-PIM coaxial line 6, the outer conductor is a low-PIM coaxial line.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention discloses a nonlinear test positioning method based on a passive intermodulation radiation field, which is a slotting coaxial nonlinear test positioning method based on leakage window radiation, and is a method for irradiating a to-be-tested piece and receiving an intermodulation signal by using a slotting coaxial line as a radiation source.
When the single coaxial electromagnetic field radiation source is used as an electromagnetic field emission source and also used as an intermodulation signal receiving unit and used as a radiation source to irradiate a to-be-detected piece, the irradiation of a to-be-detected interface is tested through a periodic array or a single slotted window, wherein a matched clamping and choking structure can be used for evaluating the nonlinear intermodulation characteristics of the metal material.
Two slotted coaxial lines are used, one slotted coaxial line serves as a radiation source to irradiate the piece to be tested, the other slotted coaxial line serves as an intermodulation signal receiving unit, the receiving coaxial line is connected with a reflection intermodulation interface of the dual-mode intermodulation tester, intermodulation signals radiated by the nonlinear point source are transmitted along the two directions of the slotted coaxial line, are received by the reflection intermodulation test channel along opposite paths and are received by the transmission intermodulation test channel along the same direction of carrier waves. Because the attenuation of the slotted coaxial line is larger, the distance between the intermodulation point and the coaxial line is obtained by comparing the amplitude difference of the intermodulation signals transmitted along the positive direction and the negative direction, and the position prediction of the intermodulation abnormal point is realized.
As shown in fig. 1-a, the basic structure of a standard slotted coaxial cable comprises an inner conductor 1, an outer conductor 2 wrapped by an insulating sheath 5 and a dielectric layer 3 between the inner conductor and the outer conductor, wherein a slotted window 4 is formed on the surface of the outer conductor 2. The electromagnetic radiation field uniformly irradiates the coaxial outer side through the outer conductor gap, as shown in fig. 1-b, to form a radiation array to the intermodulation point to be measured. Or a splayed slot, as shown in fig. 1-c, by successively increasing slot inclination angle thetanAnd the equal-interval slotting pitch P realizes the equal-amplitude irradiation of the electromagnetic signals among the radiation oscillators.
As shown in fig. 2-a, the slotted coaxial cable can also be made by forming a slotted window by forming a through hole 8 with a certain diameter d on an outer conductor 7 of the existing low PIM coaxial cable covered with an insulating layer 6. As shown in fig. 2-b, a termination test surface 10 is formed for a yoke structure implemented by customizing a special fastening bolt 9 according to the diameter of a homemade low PIM slotted coaxial outer conductor, and the termination test surface is irradiated through a leakage port 11 for testing. When the PIM testing device is used, only the clamp and the fastening screw 9 need to be replaced, the contact surface to be tested is placed in an electromagnetic radiation field, and PIM index testing of different contact end surfaces under different pressures is achieved.
For a single structure, the clamp tool shown in fig. 2-b can be used for testing the PIM of the fastening end face, and the impact of the material and the fastening torque on the PIM can be evaluated. Or only one section of open slot with one end is coaxially connected into the single reflection mode intermodulation tester, the other end is terminated with the low PIM load to absorb the carrier wave, the position of the slot irradiation area is moved to carry out carrier wave irradiation and intermodulation signal reception on different positions of the piece to be tested, and the intermodulation source point is positioned by observing the change of the intermodulation power value.
As shown in fig. 3, a slot may be formed only at one end of the coaxial cable and terminated by a low PIM load (terminating load), the slot becomes a radiation test area, the coaxial cable is connected to a single-port reflective intermodulation tester, that is, connected to a low PIM connector of a PIM analyzer (single-port reflective intermodulation tester), and the detection and positioning of the intermodulation abnormal point can be realized by moving the position irradiated by the radiation area and observing the variation of the intermodulation signal.
For the slotted coaxial of the regular array, the slotted coaxial of the regular array can be accessed into the existing dual-mode intermodulation tester, the slotted coaxial of the regular array is laid along the integral component to be tested, and the PIM source point can be positioned while the PIM value is tested by testing the reflection and transmission intermodulation values and comparing the power.
As shown in fig. 4, the basic framework of a dual-port transmission and reflection intermodulation tester (dual-mode intermodulation tester) is provided with an intermodulation detection function of one-port or dual-port transmission carrier and two-port, including a reflection intermodulation reception module and a transmission intermodulation reception module, where the reflection intermodulation reception module includes a duplexer, a filter and a spectrum analyzer, where the duplexer is connected with a corresponding connector and is connected with a transmission combiner, two paths of the transmission combiner are respectively connected with two signal sources through a power amplifier, the transmission intermodulation reception module includes a duplexer, a filter, a spectrum analyzer and a low intermodulation load, the duplexer is connected with the low intermodulation load and is connected with the filter, and the filter is connected with the spectrum analyzer.
As shown in fig. 5, a periodic regularly slotted array of coax is used to connect to the reflected intermodulation test port on the basis of the dual-mode intermodulation tester (PIM analyzer) of fig. 4, and the periodic regularly slotted coax is laid along the suspected intermodulation fault point path to form a leaky coax-based receiving array for intermodulation signal reception. Before use, the reflected power value PIM 'displayed is read by respectively using a calibration radiation PIM source arranged at the first slit at the ends of two coaxial sides of the slit'rAnd transmitting intermodulation power value PIM'fThen the slot coaxial per unit length has loss IL related to intermodulation signaluAnd slotted coaxial assemblyLength ltotSatisfies the following relationship ILu＝abs(PIM'f-PIM’r)/ltot. Reading the difference between the transmitted and reflected intermodulation power, the distance l between the intermodulation abnormal point and the transmission test portfDistance l relative to the reflective test portrIs satisfied with
Thereby realizing the positioning of the intermodulation power point.
Based on the above results, the absolute value PIM of the intermodulation anomaly powerabsPIM value read during testingfPIM (intermodulation product) with reflection intermodulation valuerSatisfy PIM therebetweenabs＝lf×ILu+PIMf＝lr×ILu+PIMr。
As shown in fig. 6, on the basis of a dual-mode intermodulation tester (PIM analyzer), a periodic regular slotted array is coaxially connected to a reflective intermodulation test port, another transmission intermodulation test port is coaxially connected to a probe with a slot at one end, the periodic regular slotted coaxial is laid along a suspected intermodulation fault point path, the dual-mode test function of the intermodulation tester is started, a slotted probe connected to the transmission intermodulation test port is moved to be in contact with different suspected intermodulation fault points, so as to scan the fault path, and the intermodulation fault point is positioned by reading the change in the transmission intermodulation value.
As shown in fig. 7, it is a frame diagram of an intermodulation test based on carrier separation, which uses two periodic regular slotted coaxiality, one of which forms a radiation array based on leakage coaxiality for carrier irradiation, and the other forms a receiving array based on leakage coaxiality for intermodulation signal reception, and a frame of an intermodulation tester receiver is as shown in fig. 8, the intermodulation tester based on carrier separation realizes the test of the distance and phase of the intermodulation signal relative to the dual connection ports on the periodic slotted coaxiality, the intermodulation abnormal point position can be obtained by comparing the coaxial length scales, the intermodulation attenuation value of unit length is calculated by the insertion loss after phase verification, and the absolute power value of the intermodulation test point is inversely calculated.
Fig. 8 is a frame diagram of an intermodulation tester receiver based on carrier separation, which is composed of a filter, a low noise amplifier, a directional coupler, a phase shifter, an attenuator, a mixing phase discriminator and a computer positioning program, and a single intermodulation detection path is composed of the filter, the low noise amplifier, the directional coupler 13 and the attenuator 12, and is used for intermodulation signal amplitude detection. Receiving intermodulation signals from a forward direction and a reverse direction through a double-path channel, enabling the double-path intermodulation detection signals to pass through a filter, a low-noise amplifier and a directional coupler, enabling an attenuator 12 to enter a frequency spectrograph to read an amplitude value, enabling the other signal to have the same amplitude after being modulated by an attenuator 15, and enabling the double-path intermodulation signals to have the same amplitude for phase detection, so that when the double-path intermodulation signals enter a frequency mixing phase discriminator to carry out phase comparison, relative phase information of the two paths of intermodulation signals is obtained; the phase shifter 14 is used for correcting the internal phase asymmetry of the signal channel when the intermodulation tester performs self-calibration before testing, and the relative phase information of the two paths of bidirectional intermodulation signals is used for self-calibration of amplitude testing. Obtaining amplitude and phase information from the double ports, comparing amplitude signals, correcting intermodulation values of amplitude attenuation by using the phase information of the two-way signals, predicting the power value and the relative position of an intermodulation point, and obtaining the positions of the intermodulation abnormal point relative to two ends of a detection coaxial, wherein the calibration test step comprises the following steps;
1) before testing, in order to eliminate the asymmetry of the cable and the receiving channel, a manually placed strong PIM radiation source is placed in the middle physical section of the receiving slotted cable, and the two attenuators 12 connected to the spectrometers are adjusted until the detected power values of the two spectrometers are equal.
2) Meanwhile, the phase shifter 14 is adjusted, and the attenuator 15 of the phase shifter 14 is connected, so that the output direct current component of the mixing phase discriminator is 0, and at the moment, the two channels of the receiving system are in a symmetrical state.
3) On the basis, for further increasing the accuracy, the slotting coaxial deviation center is selected, the leakage windows which are positioned at two sides of the cable and are closest to the double receiving ports of the intermodulation tester are placed with the same strong PIM radiation source, and the phase shifter and the attenuator are adjusted, so that the physical position of the intermodulation signal calculated by the computer is the same as the actual position, and the intermodulation detection tester realizes self calibration.
4) Before use, a calibration radiation PIM source is respectively arranged at the first slit at two coaxial ends of the slit, and the displayed reflection power value PIM 'is read'rAnd transmitting intermodulation power value PIM'fDefining slot-per-length coaxial loss IL with respect to intermodulation signalsuAnd total length of slotted coaxial line ltotDistance l of intermodulation abnormal point relative to transmission test portfDistance l relative to the reflective test portr，Δφf-rIs the phase difference of the transmitted and reflected intermodulation, the absolute value PIM of the power of the intermodulation anomaly pointabsRead transmit intermodulation value PIMfPIM, intermodulation value of reflectionrSatisfies the relationship that additional phase detection is used for correction of intermodulation positioning point positions in less than one wavelength range, m is an integer, and delta phif-rIs the phase difference of the transmitted and reflected intermodulation.
lf+lr＝ltot
ILu＝abs(PIM'f-PIM’r)/ltot
PIMabs＝lf×ILu+PIMf＝lr×ILu+PIMr
As shown in fig. 9, a periodic regular slotted array of coaxial cables is used to connect to the intermodulation tester dual receive ports on the basis of the intermodulation tester receiver based on carrier separation, and the other carriers are transmitted coaxially through a probe with a slotted end part. The method comprises the steps of laying coaxial lines with periodic regular slots along a suspected intermodulation fault point path, and moving a slot probe connected to a carrier signal source to enable the slot probe to be in contact with different suspected intermodulation fault points, so that scanning of the fault path is achieved. After calibration according to the steps illustrated in fig. 8, the location and power measurement of the intermodulation fault point are achieved by reading the intermodulation power value and the intermodulation position on the intermodulation tester.
In summary, the present invention provides a method for using a slotted coaxial joint ready-made intermodulation tester for intermodulation detection, and particularly, a slotted coaxial based intermodulation detection positioning method for carrier separation of a microwave system, which obtains a reference distance of an intermodulation point relative to a slotted coaxial by comparing amplitudes and phases of transmitted and reflected intermodulation signals, wherein phase information is used for attenuation error correction, so that a relative distance between the intermodulation point and the slotted coaxial can be directly read out by a scale on the slotted coaxial in a test process, and real-time positioning of an intermodulation abnormal point can be realized.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. A nonlinear test positioning method based on a passive intermodulation radiation field is characterized in that a slotted coaxial is used for being connected with different intermodulation testers in a combined mode, a slot is formed on an outer conductor of the slotted coaxial and serves as a carrier wave transmitting window and an intermodulation receiving window, the slotted coaxial and the intermodulation testers are connected to achieve carrier wave transmitting and intermodulation signal receiving, a carrier wave transmitting port and an intermodulation receiving port serve as physical reference points, and power measurement and relative position prediction of an intermodulation abnormal point are achieved through the physical reference points;
the slotting coaxial is divided into single-end slotting coaxial and periodic slotting coaxial;
the single-end slotted coaxial termination is matched with a low intermodulation load or a short-circuit surface with a slotted 1/4 wavelength at the section closest to the end is used for manufacturing a radiation and receiving probe which is used as a slotted coaxial probe, and a carrier irradiation area can be changed by moving the position of a window;
the periodic slotted coaxial and the single-end slotted coaxial are used independently or in combination, and are connected with different intermodulation testers in a combined manner to realize a contact type passive intermodulation test;
when one slotting coaxial line is used for positioning the intermodulation abnormal point, one period slotting coaxial line is used as a carrier transmitting line and an intermodulation receiving coaxial line, two ends of the carrier transmitting line and the intermodulation receiving coaxial line are connected to a transmitting intermodulation tester and a reflecting intermodulation tester, the carrier transmitting line and the intermodulation receiving coaxial line are laid along a suspected intermodulation abnormal point, the difference value of the transmission intermodulation value and the reflection intermodulation value is read, the difference value is compared with a calibration value before testing, and the positioning of the intermodulation abnormal point is realized based on the following formula:
in formula (II), PIM'r，PIM'fRespectively representing a reflected power value and a transmitted intermodulation power value which are read and displayed by using a calibration radiation passive intermodulation source placed at the first slit position at two ends of a slit coaxial line before test, and PIMfPIM for the value of the transmit intermodulation power read during the testrFor the values of the reflected power read during the test,/f，lrRespectively, the distance of the intermodulation anomaly point from the transmission test port and the distance from the reflection test port, ltotIndicating the total coaxial length of the slot.
2. The method according to claim 1, wherein the connection between the terminal test surface formed inside the yoke structure and the end surface to be tested is realized by fastening screws, and the electromagnetic radiation intensity and direction of the end surface to be tested are controlled by controlling the size and shape of the slot.
3. The method of claim 1, wherein when single-ended slotted coaxial is used alone, the single-ended slotted coaxial is accessed to a single-port reflective intermodulation tester, such that single-ended slotted coaxial can simultaneously implement carrier transmit and intermodulation signal receive functions;
when the periodic slots are used independently, one of the periodic slots forms a radiation array based on leakage coaxiality for carrier emission, and the other periodic slot forms a receiving array based on leakage coaxiality for receiving and detecting intermodulation signals;
when the periodic slotted coaxial and the single-ended slotted coaxial are combined, the periodic slotted coaxial is connected to a reflection intermodulation test port of the dual-mode intermodulation tester, and the single-ended slotted coaxial is connected to a transmission intermodulation test port of the dual-mode intermodulation tester.
4. The method of claim 1, wherein a single-ended slotted coaxial is used as the carrier transmitting and intermodulation receiving probe, one end of the slotted coaxial is connected to a high-power low intermodulation load, the other end of the slotted coaxial is connected to a single-port reflective intermodulation tester, and the power value of the intermodulation abnormal point is tested and the abnormal point is located by moving the position of the slot and changing the irradiation position of the carrier.
5. The method of claim 1, wherein a periodic slotted coaxial is used as a carrier receive coaxial, connected to a reflected intermodulation test port of a transmit and reflected intermodulation tester, and routed along suspected intermodulation anomaly points; and scanning along the suspected intermodulation abnormal point by using another single-ended slotted coaxial probe, comparing the measured transmission intermodulation value with the reflection intermodulation value, and testing the power value of the intermodulation abnormal point and positioning the abnormal point by the fluctuation of the transmission intermodulation value.
6. The method of passive intermodulation radiation field based nonlinear test positioning of claim 1,
a periodic slotted coaxial line is used as a carrier receiving coaxial line, connected to a reflection intermodulation test port of a transmission and reflection intermodulation tester and laid along a suspected intermodulation abnormal point; forming a radiation array based on a leakage coaxial by using another periodic slotted coaxial for carrier irradiation; the intermodulation tester with carrier separation realizes the test of the distance and the phase of the intermodulation signal on the periodical slotted coaxial relative to the double-connection port, the position of an intermodulation abnormal point can be obtained by comparing a coaxial length scale, the intermodulation attenuation value of unit length is calculated through the insertion loss after phase verification, the absolute power value of the intermodulation test point is inversely calculated, and the calculation mode is as follows:
lf+lr＝ltot
ILu＝abs(PIM'f-PIM′r)/ltot
PIMabs＝lf×ILu+PIMf＝lr×ILu+PIMr
in the formula (II)uIndicating loss of slotted coax per unit length with respect to intermodulation signals, PIMabsExpressing the absolute value of the intermodulation anomaly power, m is an integer, and delta phif-rIs the phase difference of the transmission and reflection intermodulation;
in formula (II), PIM'r，PIM'fRespectively representing a reflected power value and a transmitted intermodulation power value which are read and displayed by using a calibration radiation passive intermodulation source placed at the first slit position at two ends of a slit coaxial line before test, and PIMfPIM for the value of the transmit intermodulation power read during the testrFor the values of the reflected power read during the test,/f，lrRespectively, the distance of the intermodulation anomaly point from the transmission test port and the distance from the reflection test port, ltotIndicating the total coaxial length of the slot.
7. A nonlinear test positioning device based on a passive intermodulation radiation field is characterized by comprising an intermodulation tester which is coaxially matched with a slot for use, and the detection of the power value and the position of an intermodulation abnormal point is realized through two-way signal acquisition and self-calibration;
a slot is formed on the slotted coaxial outer conductor and used as a carrier transmitting and intermodulation receiving window, the slotted coaxial and the intermodulation tester are connected to realize carrier transmitting and intermodulation signal receiving, a carrier transmitting port and an intermodulation receiving port are used as physical reference points, and power measurement and relative position prediction of an intermodulation abnormal point are realized by using the physical reference points;
the intermodulation tester is provided with two paths of intermodulation receiving paths which are respectively used for amplitude attenuation and phase verification of intermodulation signals by taking ports at two ends of a slotted coaxial as a reference, and a single intermodulation detection path for amplitude detection of the intermodulation signals comprises a filter, a low-noise amplifier, a directional coupler, a phase shifter, an attenuator and a mixing phase discriminator; after the two paths of intermodulation detection signals are modulated by the attenuator to have equal amplitude, the two paths of intermodulation detection signals enter a frequency mixing phase discriminator to carry out phase comparison to obtain relative phase information of the two paths of intermodulation signals, and the phase shifter is used for correcting the phase asymmetry in the signal channel when the intermodulation tester is subjected to self-calibration; the relative phase information of the two paths of bidirectional intermodulation signals is used for self-checking of amplitude test; by obtaining amplitude and phase information from the dual ports, the power values and relative positions of the intermodulation points are predicted according to the following relations:
lf+lr＝ltot
ILu＝abs(PIM'f-PIM′r)/ltot
PIMabs＝lf×ILu+PIMf＝lr×ILu+PIMr
in the formula (II)uIndicating loss of slotted coax per unit length with respect to intermodulation signals, PIMabsExpressing the absolute value of the intermodulation anomaly power, m is an integer, and delta phif-rIs the phase difference of the transmission and reflection intermodulation;
in formula (II), PIM'r，PIM'fRespectively representing a reflected power value and a transmitted intermodulation power value which are read and displayed by using a calibration radiation passive intermodulation source placed at the first slit position at two ends of a slit coaxial line before test, and PIMfPIM for the value of the transmit intermodulation power read during the testrFor the values of the reflected power read during the test,/f，lrRespectively, the distance of the intermodulation anomaly point from the transmission test port and the distance from the reflection test port, ltotIndicating the total coaxial length of the slot.
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