CN111257638B - Broadband passive intermodulation test and positioning system - Google Patents
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Abstract
The invention discloses a broadband passive intermodulation testing and positioning system. The method of the invention generates equal-frequency equal-amplitude reverse-phase excitation signals through the vector modulator so as to inhibit excitation signal components in the passive intermodulation signals, samples the down-converted passive intermodulation signals and reference signals by using the analog-to-digital converter, extracts phase information through correction, locates the position of a passive intermodulation generation point, and can be used for measuring the passive intermodulation. The invention realizes the broadband positioning of the passive intermodulation generation point and can be used for the measurement of the passive intermodulation of a high-power device.
Description
Technical Field
The invention relates to a test positioning system for microwave devices, in particular to a test and positioning system and a method for broadband passive intermodulation generation points.
Background
Passive Intermodulation (PIM) refers to nonlinear distortion generated by electromagnetic nonlinearity of Passive devices in high power wireless communication systems. With the rapid development of high-power communication technology, the requirement for the sensitivity of a receiving system is increasingly increased, and once a weak passive intermodulation signal generated by nonlinearity falls into a receiving frequency band, the operation of the system may be greatly influenced. Therefore, detecting the location of the passive intermodulation generation point is important to effectively suppress and reduce the occurrence of passive intermodulation in design and engineering.
In early studies of passive intermodulation, the research was mainly directed to the generation mechanism, suppression and cancellation of passive intermodulation, but relatively few studies were made on the localization of passive intermodulation. As shown in fig. 1, a narrowband positioning system of passive intermodulation adopts a band-pass filter to filter carrier components in the passive intermodulation and utilizes a phase discriminator to extract a phase difference between a reference signal and a passive intermodulation signal to position a passive intermodulation generation point. The bandpass filter has a passband that limits practical positioning applications due to the introduction of the bandpass filter, and the design of the bandpass filter with a high quality factor also incurs significant manufacturing costs.
Disclosure of Invention
In order to solve the problems in the background art, the invention aims to provide a broadband passive intermodulation testing and positioning system and a broadband passive intermodulation positioning method.
The technical scheme adopted by the invention is as follows:
a broadband passive intermodulation test and positioning system:
the system comprises a first excitation signal source, a second excitation signal source, a passive intermodulation component reference signal source, a first power amplifier, a second power amplifier, a first coupler, a second coupler, a combiner, a directional coupler, a first vector modulator, a second vector modulator, a first low-pass filter, a second low-pass filter, a first 3dB electric bridge, a second 3dB electric bridge, a digital-to-analog converter, a power divider, a first down-conversion demodulator, a second down-conversion demodulator and an analog-to-digital converter; the first driving signal source is connected to the input port of the first coupler through the first power amplifier, and the output port of the first coupler is connected to one input end of the combiner; the second driving signal source is connected to the input port of the second coupler through the second power amplifier, and the output port of the second coupler is connected to the other input end of the combiner; the output end of the combiner is connected to the input end of the directional coupler, the output end of the directional coupler is connected to a device to be tested/low intermodulation matched load, the coupling end of the directional coupler is connected to one input end of the first 3dB bridge, the coupling end of the first coupler connected with the first excitation signal source is connected to one input end of the first vector modulator, and the output end of the first vector modulator is connected to the other input end of the first 3dB bridge through the first low-pass filter; the output end of the first 3dB bridge is connected to one input end of the second 3dB bridge, the coupling end of a second coupler connected with a second excitation signal source is connected to one input end of a second vector modulator, and the output end of the second vector modulator is connected to the other input end of the second 3dB bridge through a second low-pass filter; the output end of the signal source with lower output signal frequency in the first excitation signal source and the second excitation signal source is respectively connected to one input end of a first down-conversion demodulator and one input end of a second down-conversion demodulator through a power divider, the passive intermodulation product reference signal source is connected to the other input end of the first down-conversion demodulator, the output end of a second 3dB bridge is connected to the other input end of the second down-conversion demodulator, the output ends of the first down-conversion demodulator and the second down-conversion demodulator are both connected to an analog-to-digital converter,
the first power amplifier and the second power amplifier have the same structure and are formed by sequentially connecting a preceding power amplifier, a third low-pass filter and a rear power amplifier.
The first excitation signal source and the second excitation signal source respectively generate two paths of excitation signals with different frequencies, and the passive intermodulation component reference signal source generates one path of passive intermodulation component reference signal.
The device to be tested is a diode or a coaxial connection port.
The low intermodulation matching load is a resistor, one end of the resistor is connected with the device to be tested, and the other end of the resistor is grounded.
The power divider adopts a 1:1 power uniform dividing mode.
The first vector modulator and the second vector modulator are also connected with a digital-to-analog converter, and external control signals are input into the digital-to-analog converter to further control the phase modulation of the first vector modulator and the second vector modulator.
Secondly, a broadband passive intermodulation test and positioning method:
by adopting the system, two paths of excitation signals and one path of passive intermodulation component reference signal are generated by the three paths of coherent signal source generators, and the frequency f is generated by the first excitation signal source1Is generated by a second excitation signal source at a frequency f2Excitation signal of f2>f1Taking one path of excitation signal with lower frequency as an intrinsic signal, generating one path of passive intermodulation component reference signal by a passive intermodulation component reference signal source, sequentially passing the two paths of excitation signals through respective power amplifiers and couplers, then entering a combiner, generating one path of two-tone signal by a directional coupler, feeding the two paths of two-tone signal into a device to be tested to generate the passive intermodulation signal, feeding the passive intermodulation signal of the device to be tested back to the directional coupler, entering a 3dB electric bridge from a coupling end of the directional coupler, and feeding the two paths of two-tone signal into two electric bridgesPart of excitation signals coupled by a first coupler connected with the excitation signal source are input into a 3dB bridge after being subjected to amplitude and phase adjustment by a vector modulator, so that the part of the excitation signals and excitation signal components of the passive intermodulation signals are in the same amplitude and opposite phase, and the effect of carrying out amplitude and phase inversion on the frequency f in the passive intermodulation signals is realized1Power suppression of the excitation signal component, as shown in fig. 3; the 3dB bridge output signal enters a second down-conversion demodulator and a sampling module consisting of a power divider, two down-conversion demodulators and an analog-to-digital converter is used for measuring the amplitude phase of the excitation signal and the amplitude phase of the reference signal, so that the passive intermodulation is measured; and calculating the phase difference between the two paths of signals of the excitation signal and the reference signal, and correcting the fixed phase difference of the device to be detected in the signal transmission process by using the phase difference to obtain the signal phase generated by the passive intermodulation generation point in the device to be detected, so that the passive intermodulation can be more accurately positioned.
The method comprises the following steps:
1) under the condition that a directional coupler is directly connected with a low intermodulation matching load, two paths of excitation signals and one path of passive intermodulation component reference signals are generated by a three-path coherent signal source generator, and a first excitation signal source generates a signal with the frequency f1Is generated by a second excitation signal source at a frequency f2Excitation signal of f2>f1One path of excitation signal with lower frequency is taken as an intrinsic signal, one path of passive intermodulation component reference signal is generated by a passive intermodulation component reference signal source, the two paths of excitation signals enter a combiner after sequentially passing through respective power amplifiers and couplers to generate one path of double-tone signal,
the signal passes through the device to be tested through the straight-through end of the directional coupler to generate a passive intermodulation signal which is absorbed by the low intermodulation matched load, the passive intermodulation signal generated by the device to be tested is reflected back to the directional coupler, the passive intermodulation signal enters the first 3dB electric bridge through the coupling end of the directional coupler, meanwhile, part of excitation signals coupled by the first coupler connected with the first excitation signal source are input to the first 3dB electric bridge after being subjected to amplitude phase adjustment through the first vector modulator, and the frequency of the part of the excitation signals and the frequency of the passive intermodulation signal are f1The excitation signal components are in the same amplitude and opposite phase, and in the first 3dBImplementation of frequency f in passive intermodulation signal in bridge1Power suppression of excitation signal components, i.e. elimination of frequency f in passive intermodulation signals1An excitation signal component;
the output signal of the first 3dB bridge enters a second 3dB bridge, and meanwhile, part of the excitation signal coupled by a second coupler connected with a second excitation signal source is input to the second 3dB bridge after being subjected to amplitude and phase adjustment by a second vector modulator, so that the frequency of the part of the excitation signal and the frequency of the passive intermodulation signal are f2Excitation signal components of the same amplitude and opposite phase, and a frequency f in the second 3dB bridge to the passive intermodulation signal2Power suppression of excitation signal components, i.e. elimination of frequency f in passive intermodulation signals2An excitation signal component;
the first excitation signal source generates a frequency f1The excitation signal is divided into two paths by the power divider, and one path of the power divider enters the first down-conversion demodulator and the passive intermodulation component reference signal to be resolved to obtain the phase of the passive intermodulation component reference signal and input the phase; the output signal of the first 3dB electric bridge enters a second down-conversion demodulator, the other path of the power divider enters the second down-conversion demodulator, and the second down-conversion demodulator resolves to obtain the phase of the excitation signal; the analog-to-digital converter makes the difference between the phase of the passive intermodulation component reference signal and the phase of the excitation signal as a fixed phase difference;
2) under the condition that the directional coupler is directly connected with a low intermodulation matching load through a device to be tested, two paths of excitation signals and one path of passive intermodulation component reference signal are generated by a three-path coherent signal source generator, and a first excitation signal source generates a signal with the frequency f1Is generated by a second excitation signal source at a frequency f2Excitation signal of f2>f1Taking one path of excitation signal with lower frequency as an intrinsic signal, generating one path of passive intermodulation component reference signal by a passive intermodulation component reference signal source, sequentially passing the two paths of excitation signals through respective power amplifiers and couplers, generating one path of double-tone signal by a combiner, then feeding the double-tone signal into a device to be tested through a direct end of a directional coupler to generate the passive intermodulation signal, and feeding the passive intermodulation signal of the device to be tested back to the directional couplingAnd the part of the excitation signal coupled by the first coupler connected with the first excitation signal source is input to the first 3dB bridge after being subjected to amplitude and phase adjustment by the first vector modulator, so that the frequency of the part of the excitation signal and the frequency of the passive intermodulation signal are f1Excitation signal components are in the same amplitude and opposite phase, and the frequency f of the passive intermodulation signals is realized in the first 3dB electric bridge1Power suppression of excitation signal components, i.e. elimination of frequency f in passive intermodulation signals1An excitation signal component;
the output signal of the first 3dB bridge enters a second 3dB bridge, and meanwhile, part of the excitation signal coupled by a second coupler connected with a second excitation signal source is input to the second 3dB bridge after being subjected to amplitude and phase adjustment by a second vector modulator, so that the frequency of the part of the excitation signal and the frequency of the passive intermodulation signal are f2The excitation signal components are in the same amplitude and opposite phase, and the frequency f of the passive intermodulation signal is realized in a second 3dB electric bridge2Power suppression of excitation signal components, i.e. elimination of frequency f in passive intermodulation signals2An excitation signal component;
the first excitation signal source generates a frequency f1The excitation signal is divided into two paths by the power divider, and one path of the power divider enters the first down-conversion demodulator and the passive intermodulation component reference signal to be resolved to obtain the phase of the passive intermodulation component reference signal and input the phase; the output signal of the first 3dB electric bridge enters a second down-conversion demodulator, the other path of the power divider enters the second down-conversion demodulator, and the second down-conversion demodulator resolves to obtain the phase of the excitation signal; and (3) subtracting the fixed phase difference obtained in the step 1) from the phase difference between the passive intermodulation component reference signal and the excitation signal obtained in the analog-to-digital converter, and taking the difference as the final signal phase generated by the passive intermodulation generation point.
The sampling module comprises a reference signal and a zero-adjusted passive intermodulation signal which are respectively input into two down-conversion demodulators, and meanwhile, components with smaller frequency in the excitation signal are respectively output from OUT1 and OUT2 of the power divider and are respectively connected with the intrinsic signal input ends of the down-conversion demodulators to be used as the intrinsic signals of down-conversion.
The output ends of the two down-conversion demodulators are connected with the analog-to-digital converter to realize the sampling of two paths of signals.
The method of the invention generates equal-frequency equal-amplitude reverse-phase excitation signals through the vector modulator so as to inhibit excitation signal components in the passive intermodulation signals, samples the down-converted passive intermodulation signals and reference signals by using the analog-to-digital converter, extracts phase information through correction, locates the position of a passive intermodulation generation point, and can be used for measuring the passive intermodulation.
The invention has the following beneficial effects:
the invention realizes the amplitude suppression of the excitation signal component in the passive intermodulation signal through the vector modulator and the electric bridge, and further measures the phase information of the passive intermodulation signal and the passive intermodulation reference signal through the analog-to-digital converter to realize the broadband positioning of the passive intermodulation generation point.
Meanwhile, the invention can also be used for measuring the passive intermodulation of the high-power device.
Drawings
Fig. 1 is a block diagram of a narrowband structure of a passive intermodulation positioning in a prior art method.
Fig. 2 is a block diagram of the apparatus of the present invention.
Fig. 3 is a schematic down-conversion diagram of a sampling module of the present invention.
In the figure: the device comprises a first excitation signal source (1), a second excitation signal source (2), a passive intermodulation component reference signal source (3), a first power amplifier (4), a second power amplifier (5), a first coupler (6), a second coupler (7), a combiner (8), a directional coupler (9), a device to be tested (10), a low intermodulation matched load (11), a first vector modulator (14), a second vector modulator (17), a first low-pass filter (13), a second low-pass filter (16), a first 3dB electric bridge (12), a second 3dB electric bridge (15), a digital-to-analog converter (18), a power divider (19), a first down-conversion demodulator (20), a second down-conversion demodulator (21), an analog-to-digital converter (22), a preceding stage power amplifier (23), a third low-pass filter (24) and a post-stage power amplifier (25).
FIG. 4 is a diagram of a device under test simulated by positioning test in the present invention.
In the figure: (1) showing a cable coaxial feed, (2) showing a multi-screw rectangular filter.
Detailed Description
The following describes the implementation process of the present invention in detail with reference to the attached drawings in the embodiment of the present invention.
As shown in fig. 1, the embodied system includes a first excitation signal source 1, a second excitation signal source 2, a passive intermodulation product reference signal source 3, a first power amplifier 4, a second power amplifier 5, a first coupler 6, a second coupler 7, a combiner 8, a directional coupler 9, a first vector modulator 14, a second vector modulator 17, a first low pass filter 13, a second low pass filter 16, a first 3dB bridge 12, a second 3dB bridge 15, a digital-to-analog converter 18, a power divider 19, a first down-conversion demodulator 20, a second down-conversion demodulator 21, and an analog-to-digital converter 22; the first driving signal source 1 is connected to an input port of a first coupler 6 through a first power amplifier 4, and an output port of the first coupler 6 is connected to one input end of a combiner 8; the second driving signal source 2 is connected to an input port of a second coupler 7 through a second power amplifier 5, and an output port of the second coupler 7 is connected to the other input end of the combiner 8; the output end of the combiner 8 is connected to the input end of a directional coupler 9, the output end of the directional coupler 9 is connected to a device under test 10/low intermodulation matched load 11, the coupling end of the directional coupler 9 is connected to one input end of a first 3dB bridge 12, the coupling end of a first coupler 6 connected to a first excitation signal source 1 is connected to one input end of a first vector modulator 14, and the output end of the first vector modulator 14 is connected to the other input end of the first 3dB bridge 12 through a first low-pass filter 13; the output terminal of the first 3dB bridge 12 is connected to one input terminal of the second 3dB bridge 15, the coupling terminal of the second coupler 7 to which the second excitation signal source 2 is connected to one input terminal of a second vector modulator 17, and the output terminal of the second vector modulator 17 is connected to the other input terminal of the second 3dB bridge 15 via a second low pass filter 16; the output end of the signal source with lower output signal frequency in the first excitation signal source 1 and the second excitation signal source 2 is connected to one input end of a first down-conversion demodulator 20 and a second down-conversion demodulator 21 respectively through a power divider 19, the passive intermodulation component reference signal source 3 is connected to the other input end of the first down-conversion demodulator 20, the output end of a second 3dB bridge 15 is connected to the other input end of the second down-conversion demodulator 21, the output ends of the first down-conversion demodulator 20 and the second down-conversion demodulator 21 are connected to an analog-to-digital converter 22, and a sampling module is formed by the first down-conversion demodulator 20, the second down-conversion demodulator 21 and the analog-to-digital converter 22.
The first power amplifier 4 and the second power amplifier 5 have the same structure, and are formed by sequentially connecting a front-stage power amplifier 23, a third low-pass filter 24 and a rear-stage power amplifier 25.
The first excitation signal source 1 and the second excitation signal source 2 respectively generate two paths of excitation signals with different frequencies, one path of excitation signal with lower frequency is used as an intrinsic signal, and the passive intermodulation component reference signal source 3 generates one path of passive intermodulation component reference signal.
In one embodiment, the device under test 10 is a diode or a coaxial port (e.g., a metal fixture with a coaxial port). The low intermodulation matched load 11 is a resistor, one end of the resistor is connected with the device to be tested 10, and the other end of the resistor is grounded. The power divider 19 adopts a 1:1 power equalizing mode.
The first vector modulator 14 and the second vector modulator 17 are further connected to a digital-to-analog converter 18, and an external control signal is input to the digital-to-analog converter 18 to control phase modulation of the first vector modulator 14 and the second vector modulator 17.
The invention adopts a system architecture as shown in fig. 2, a radio frequency signal source adopts two paths of excitation signals 1 and 2 and a reference signal source 3, and the two paths of excitation signals share the same reference clock. The two excitation signals respectively pass through power amplifiers 4 and 5 and couplers 6 and 7, and form a path of two-tone excitation signal through a combiner 8. The power amplifiers represented by 4 and 5 are respectively composed of three partially straight lines as shown by the dashed boxes in fig. 2, and are respectively a front stage power amplifier 23, a low pass filter 24 and a rear stage power amplifier 25. The function of the couplers 6, 7 is to couple part of the signal for amplitude suppression of the excitation signal. The double-tone signal enters the device to be tested 10 through the directional coupler 9, a passive intermodulation signal is generated by a passive intermodulation generation point at a certain position in the device to be tested, and the double-tone signal once enters the electric bridges 12 and 15 through the coupling port of the directional coupler. The passive intermodulation signal output from the bridge 15 and the reference signal generated by the reference signal source 3 pass through down-conversion demodulators 21, 20, respectively, and then signal data is collected by a digital-to-analog converter 22.
Specific examples of the present invention and its implementation are as follows:
in the concrete implementation, the first coupler (5) and the second coupler (6) at the front end, the combiner and the directional coupler are considered to be in the relation of electrical connection in the actual system architecture, so the design is that the three are designed and manufactured as a whole, the operating frequency band of the whole structure is 0.7-2.3 GHz, and the carrying power range is more than 43 dBm. The device to be tested adopts a cable coaxial feeder line and a high-power multi-screw rectangular filter as shown in fig. 4 to simulate single-point and multi-point passive intermodulation generation sources, wherein the low intermodulation matching load adopts a high-power 50-ohm resistor, an input port of the device to be tested is connected with the directional coupler, and an output port of the device to be tested is grounded through the 50-ohm low intermodulation matching load.
The down-converted eigen signal selects one of the two paths of excitation signals with lower frequency as an eigen signal. As shown in fig. 3, taking the third-order intermodulation product as an example, the frequency relationship of the two excitation signals is as follows:
f2>f1 Δf＝f2-f1
wherein, with f1The down-converted frequency component 2 Δ f represents the target third order intermodulation product as an intrinsic signal.
The amplitude suppression of the excitation signal component and the sampling dynamic range of the digital-to-analog converter of the sampling module need to be designed according to the power difference between the generated passive intermodulation signal and the excitation signal. Their relationship is as follows:
PSE+SNR≥ΔP
wherein, the amplitude suppression degree represented by the PSE, the SNR represents the sampling dynamic range of the digital-to-analog converter in the sampling module, and Δ P represents the power difference between the excitation signal component in the generated passive intermodulation signal and the target signal, which is described herein by using dB as a unit.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (8)
1. A broadband passive intermodulation test and positioning system, characterized by: the passive intermodulation component signal source comprises a first excitation signal source (1), a second excitation signal source (2), a passive intermodulation component reference signal source (3), a first power amplifier (4), a second power amplifier (5), a first coupler (6), a second coupler (7), a combiner (8), a directional coupler (9), a first vector modulator (14), a second vector modulator (17), a first low-pass filter (13), a second low-pass filter (16), a first 3dB electric bridge (12), a second 3dB electric bridge (15), a digital-to-analog converter (18), a power divider (19), a first down-conversion demodulator (20), a second down-conversion demodulator (21) and an analog-to-digital converter (22); the first excitation signal source (1) is connected to an input port of a first coupler (6) through a first power amplifier (4), and an output port of the first coupler (6) is connected to one input end of a combiner (8); the second excitation signal source (2) is connected to the input port of the second coupler (7) through the second power amplifier (5), and the output port of the second coupler (7) is connected to the other input end of the combiner (8); the output end of the combiner (8) is connected to the input end of a directional coupler (9), the output end of the directional coupler (9) is connected to a device to be tested (10)/low intermodulation matched load (11), the coupling end of the directional coupler (9) is connected to one input end of a first 3dB bridge (12), the coupling end of a first coupler (6) connected with a first excitation signal source (1) is connected to one input end of a first vector modulator (14), and the output end of the first vector modulator (14) is connected to the other input end of the first 3dB bridge (12) through a first low-pass filter (13); the output end of the first 3dB bridge (12) is connected to one input end of a second 3dB bridge (15), the coupling end of a second coupler (7) connected with a second excitation signal source (2) is connected to one input end of a second vector modulator (17), and the output end of the second vector modulator (17) is connected to the other input end of the second 3dB bridge (15) through a second low-pass filter (16); the output end of a signal source with lower output signal frequency in a first excitation signal source (1) and a second excitation signal source (2) is respectively connected to one input end of a first down-conversion demodulator (20) and one input end of a second down-conversion demodulator (21) through a power divider (19), a passive intermodulation component reference signal source (3) is connected to the other input end of the first down-conversion demodulator (20), the output end of a second 3dB bridge (15) is connected to the other input end of the second down-conversion demodulator (21), and the output ends of the first down-conversion demodulator (20) and the second down-conversion demodulator (21) are both connected to an analog-to-digital converter (22).
2. The broadband passive intermodulation test and positioning system of claim 1, wherein: the first power amplifier (4) and the second power amplifier (5) have the same structure and are formed by sequentially connecting a front-stage power amplifier (23), a third low-pass filter (24) and a rear-stage power amplifier (25).
3. The broadband passive intermodulation test and positioning system of claim 1, wherein: the first excitation signal source (1) and the second excitation signal source (2) respectively generate two paths of excitation signals with different frequencies, and the passive intermodulation component reference signal source (3) generates one path of passive intermodulation component reference signal.
4. The broadband passive intermodulation test and positioning system of claim 1, wherein: the device to be tested (10) is a diode or a coaxial connection port.
5. The broadband passive intermodulation test and positioning system of claim 1, wherein: the low intermodulation matched load (11) is a resistor, one end of the resistor is connected with the device to be tested (10), and the other end of the resistor is grounded.
6. The broadband passive intermodulation test and positioning system of claim 1, wherein: the power divider (19) adopts a 1:1 power uniform dividing mode.
7. The broadband passive intermodulation test and positioning system of claim 1, wherein: the first vector modulator (14) and the second vector modulator (17) are also connected with a digital-to-analog converter (18), and external control signals are input into the digital-to-analog converter (18) to further control the phase modulation of the first vector modulator (14) and the second vector modulator (17).
8. A broadband passive intermodulation test and positioning method is characterized in that: using the system of any of claims 1-7:
the method comprises the following steps:
1) in the case of a directional coupler (9) directly connected to a low-intermodulation matched load (11) via a device under test (10), the frequency f produced by the first excitation signal source (1) is1Is generated by a second excitation signal source (2) at a frequency f2Excitation signal of f2>f1A passive intermodulation component reference signal source (3) generates a passive intermodulation component reference signal, two excitation signals sequentially pass through respective power amplifiers and couplers and then enter a combiner (8) to generate a path of double-tone signal, the signal passes through a straight-through end of a directional coupler (9) and passes through a device to be tested (10) to generate a passive intermodulation signal which is absorbed by a low intermodulation matching load, the passive intermodulation signal generated by the device to be tested (10) is reflected back to the directional coupler (9), and enters a first 3dB electric bridge (12) from a coupling end of the directional coupler (9), meanwhile, a part of excitation signals coupled by a first coupler (6) connected with a first excitation signal source (1) are input to a first 3dB bridge (12) after being subjected to amplitude and phase adjustment through a first vector modulator (14), so that the frequency of the part of excitation signals and the frequency of passive intermodulation signals are f.1The excitation signal components are in phase with and out of phase with each other, and the frequency of the passive intermodulation signals is f in a first 3dB bridge (12)1Power suppression of the excitation signal component;
the output signal of the first 3dB bridge (12) enters a second 3dB bridge (15), and part of the excitation signal coupled by a second coupler (7) connected with a second excitation signal source (2) is input after being subjected to amplitude and phase adjustment through a second vector modulator (17)To a second 3dB bridge (15) such that the frequency of the portion of the excitation signal and the passive intermodulation signal is f2The excitation signal components are of the same amplitude and opposite phase, and the frequency of the passive intermodulation signals is f in a second 3dB bridge (15)2Power suppression of the excitation signal component;
the first excitation signal source (1) generates a frequency f1The excitation signal is divided into two paths by the power divider (19), one path of the power divider (19) enters the first down-conversion demodulator (20) and the passive intermodulation component reference signal to be resolved to obtain the phase of the passive intermodulation component reference signal and input the phase; the output signal of the first 3dB electric bridge (12) enters a second down-conversion demodulator (21), the other path of the power divider (19) enters the second down-conversion demodulator (21), and the second down-conversion demodulator (21) resolves to obtain the phase of the excitation signal; the difference between the phase of the passive intermodulation product reference signal and the phase of the excitation signal is used as a fixed phase difference in the analog-to-digital converter (22);
2) under the condition that the directional coupler (9) is directly connected with the device to be tested (10) and is not connected with the low intermodulation matching load (11), the frequency f generated by the first excitation signal source (1)1Is generated by a second excitation signal source (2) at a frequency f2Excitation signal of f2>f1A passive intermodulation component reference signal source (3) generates a path of passive intermodulation component reference signal, two paths of excitation signals sequentially pass through respective power amplifiers and couplers and then pass through a combiner (8) to generate a path of double-tone signal, then the double-tone signal is fed into a device to be tested (10) through a straight-through end of a directional coupler (9) to generate a passive intermodulation signal, the passive intermodulation signal of the device to be tested (10) is fed back to the directional coupler (9), the passive intermodulation signal enters a first 3dB electric bridge (12) through a coupling end of the directional coupler (9), and meanwhile, part of excitation signals coupled by a first coupler (6) connected with a first excitation signal source (1) are input to the first 3dB electric bridge (12) after being subjected to amplitude and phase adjustment through a first vector modulator (14), so that the frequency of the part of the excitation signals and the passive intermodulation signals is f1The excitation signal components are in phase with and out of phase with each other, and the frequency of the passive intermodulation signals is f in a first 3dB bridge (12)1Power suppression of the excitation signal component;
the first 3dB bridge (12) outputs a signal into the second 3dB bridge (15),meanwhile, part of excitation signals coupled by a second coupler (7) connected with a second excitation signal source (2) are input into a second 3dB bridge (15) after being subjected to amplitude and phase adjustment through a second vector modulator (17), so that the frequency of the part of excitation signals and the frequency of passive intermodulation signals are f2The excitation signal components are of the same amplitude and opposite phase, and the frequency of the passive intermodulation signals is f in a second 3dB bridge (15)2Power suppression of the excitation signal component;
the first excitation signal source (1) generates a frequency f1The excitation signal is divided into two paths by the power divider (19), one path of the power divider (19) enters the first down-conversion demodulator (20) and the passive intermodulation component reference signal to be resolved to obtain the phase of the passive intermodulation component reference signal and input the phase; the output signal of the first 3dB electric bridge (12) enters a second down-conversion demodulator (21), the other path of the power divider (19) enters the second down-conversion demodulator (21), and the second down-conversion demodulator (21) carries out resolving to obtain a second phase of the excitation signal; and (2) in the analog-to-digital converter (22), subtracting the fixed phase difference obtained in the step 1) from the difference between the phase of the passive intermodulation product reference signal and the second phase of the excitation signal, and taking the result as the final phase of the signal generated by the passive intermodulation generation point.
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| CN102156139B (en) * | 2011-04-08 | 2012-08-22 | 浙江大学 | Method and system for measuring passive intermodulation generation point of microwave device by using electromagnetic wave phase |
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