Method and system for identifying external pim sources

Abstract

Methods and systems for identifying PIM sources of an antenna under test (AUT) are provided, wherein the AUT is installed in a desired operating environment. The system includes a PIM analyzer connected to the AUT for applying first and second RF stimulus signals to input ports of the AUT, and a portable RF transmitter configured to apply a third RF stimulus signal to a suspected external PIM source. The PIM analyzer is configured to measure one or more characteristics of PIM signals received by the AUT generated by the first, second, and third RF stimulus signals.

Description

Technical Field

[0001] This invention relates to the identification of passive intermodulation (PIM) sources. In particular, although not exclusively, this invention relates to the identification of external PIM sources of in-situ cellular communication antennas. Background Technology

[0002] Antennas are essential components of many radio communication systems, especially cellular communication systems. With the growth and development of cellular communication networks, new antennas are being installed at greater densities, particularly in cities and urban areas.

[0003] Passive intermodulation (PIM) distortion is of particular concern in such cellular communication systems because it can significantly impact antenna performance. In short, PIM is a form of electromagnetic interference caused by devices or components with nonlinear transmission characteristics. Examples of PIM sources in antennas include oxidized metal-to-metal junctions, loose connectors, and numerous other manufacturing defects.

[0004] Modern mobile communication antennas have very complex internal structures, and they typically contain hundreds of interconnects, cables, and components, resulting in numerous possible pin-in-molecular (PIM) locations. Therefore, PIM testing is often complex and is frequently performed in a laboratory environment when manufacturing antennas.

[0005] However, the problem is that even if the antenna has no PIM source when tested in a laboratory environment, PIM may still be present when the antenna is installed. This PIM may originate from the antenna's own installation, such as problems with the wiring, or from external sources, such as objects in the surrounding environment.

[0006] There are methods that can perform distance testing to PIM sources based on reflection measurements. These methods are useful when the PIM source is contained within a transmission line, cable, filter, or antenna itself, as they help identify the PIM source's location. However, these methods are not particularly useful when the PIM source is exposed to the open air and activated by radiated power from the antenna. Thus, methods also exist for physically scanning the exterior of an antenna for suspected PIM sources using probes.

[0007] Figure 1A schematic diagram of a system 100 for detecting PIM in an AUT 105, according to the prior art, is shown. A PIM tester 110 is coupled to the AUT 105 and configured to apply an RF excitation signal to the AUT 105, thereby stimulating an external PIM source 115. A probe 120, including a receiver, then physically moves around the object, receives the signal and filters it with a bandpass filter 120a, and analyzes it with a signal analyzer 120b. When approaching the PIM source 115, the signal analyzer 120b detects a high PIM level, thereby identifying the PIM source 115.

[0008] The problem with this probe-based testing is that there are often many PIM sources in an area, and it may be impossible to access all potential PIM sources. This is especially true in cities where antennas are often mounted on rooftops. A further problem is that clearing all identified PIM sources from the area can be very expensive, or simply impossible.

[0009] Therefore, it is clear that there is a need to improve the identification of external PIM sources, especially those related to on-site cellular communication antennas.

[0010] It should be clearly understood that if prior art publications are cited in this document, such citation does not constitute an acknowledgment that such publications form general knowledge in the art in Australia or any other country. Summary of the Invention

[0011] The present invention relates to methods and systems for identifying external PIM sources for antenna installations, methods and systems that can at least partially overcome at least one of the disadvantages mentioned above or provide consumers with useful or commercial options.

[0012] In view of the foregoing, in one form, the invention is widely found in a system for identifying an external passive intermodulation (PIM) source of an antenna under test (AUT) installed in a desired operating environment, the system comprising: A PIM analyzer, connected to the AUT, is used to apply a first RF excitation signal and a second RF excitation signal to the input ports of the AUT; and A portable RF transmitter configured to apply a third RF excitation signal to a suspected external PIM source; The PIM analyzer is configured to measure one or more characteristics of the PIM signal generated by the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal and received by the AUT.

[0013] Advantageously, the use of a third RF excitation signal applied by a portable RF transmitter to a suspected external PIM source enables the system not only to identify the location of the external PIM source but also to determine its impact on the AUT. This, in turn, allows the external PIM source to be considered based on its impact on the AUT, which further reduces the time and cost associated with handling PIM sources in the AUT's operating environment.

[0014] By essentially encoding suspicious external PIM sources, the system can measure whether that encoding is detected in the network, thus measuring whether the suspicious PIM source actually causes interference in the network. Subsequently, any suspicious PIM sources detected in the network that affect the network can be reduced or eliminated to meet installation specifications. Similarly, any suspicious PIM sources that do not affect the network (or significantly affect the network) can be simply ignored, thereby reducing the time and cost of masking or otherwise handling these suspicious PIM sources.

[0015] Preferably, the portable RF transmitter is configured to generate a third RF excitation signal at a selected frequency among a plurality of different operating frequencies. This allows the portable RF transmitter to be configured according to a specific scenario or AUT configuration.

[0016] Preferably, the third RF excitation signal is generated at a frequency such that the resulting PIM signal from the third RF excitation signal is at a frequency within the receiver band of the PIM analyzer.

[0017] The resulting PIM signal measured by the PIM analyzer may include a third-order PIM signal from the first RF excitation signal and the second RF excitation signal. Alternatively, the resulting PIM signal measured by the PIM analyzer may include third-order PIM signals from the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal. Preferably, the resulting PIM signal measured by the PIM analyzer includes 1) a third-order PIM signal from the first RF excitation signal and the second RF excitation signal, and 2) a third-order PIM signal from the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal.

[0018] The first RF excitation signal and the second RF excitation signal can be provided at a first frequency and a second frequency (F1 and F2), and a third RF excitation signal can be provided at a third frequency (F3).

[0019] A first frequency and a second frequency (F1 and F2) can be selected such that F1, F2, the third-order PIM signal (IM3) from the first RF excitation signal and the second RF excitation signal, or any local oscillator do not generate internal interference from any intermodulation (IM) products being created.

[0020] A third frequency (F3) can be selected so that the resulting PIM frequency (IM3new, F1+F2-F3) falls within the receiver band of the PIM analyzer, and is obtained through the formula F3=F1+F2-IM3new.

[0021] The first and second signals may include signals generated using one or more local oscillators. Alternatively, the first and second signals may include BTS radio signals. In this case, the BTS radio signals may include pulse envelope signals.

[0022] Preferably, the system is configured to determine the effect of a suspected external PIM source that applies a third RF excitation signal to the AUT on the AUT.

[0023] The system can be configured to determine the impact of a suspected external PIM source based on the amplitude of a third-order PIM signal from a first RF excitation signal, a second RF excitation signal, and a third RF excitation signal.

[0024] The system can be configured to determine the influence of a suspected external PIM source based on the amplitude of a third-order PIM signal from a first RF excitation signal, a second RF excitation signal, and a third RF excitation signal, and with reference to the amplitude of a third-order PIM signal from the first RF excitation signal and the second RF excitation signal.

[0025] The system can be configured to determine the influence of a suspected external PIM source by determining the coexistence of a third-order PIM signal from a first RF excitation signal, a second RF excitation signal, and a third RF excitation signal with a third-order PIM signal from the first RF excitation signal and the second RF excitation signal above a specific threshold.

[0026] The system may include a second AUT configured to be tested simultaneously with the first AUT. A second PIM analyzer may be connected to the second AUT. A third RF excitation signal may be provided, such that a PIM received by the first and second AUTs is generated from the third RF excitation signal.

[0027] The second PIM analyzer can be used to apply a fourth RF excitation signal and a fifth RF excitation signal to the input port of the second AUT, so that the PIM signal received by the second AUT is generated by the third RF excitation signal, the fourth RF excitation signal and the fifth RF excitation signal.

[0028] The portable RF transmitter can be configured to apply a third RF excitation signal to a suspected external PIM source by applying a third RF excitation signal near the suspected external PIM source. The portable RF transmitter can be configured to apply the third RF excitation signal within approximately 1 m of the suspected external PIM source.

[0029] Portable RF transmitters may include an elongated rod from which a third signal is emitted. This configuration allows a user to apply a third RF excitation signal to a suspected external PIM source while keeping his or her body away from the suspected external PIM source, thereby reducing the likelihood that the person's body will shield the PIM.

[0030] A portable RF transmitter may include a receiver for receiving one or more PIM signals. The receiver may be configured to determine the amplitude of a third-order PIM signal from a first RF excitation signal and a second RF excitation signal.

[0031] The system may include a display associated with the receiver. The display may be configured to show the amplitude of the PIM signal. The system may be configured to emit an alarm (e.g., an audible alarm) when the signal exceeds a threshold.

[0032] The portable RF transmitter and receiver can be configured to operate in a switching manner between a first mode and a second mode, such that it can operate in a first PIM positioning mode and a second signal generation mode. In the first PIM positioning mode, the receiver is configured to receive PIM signals from a first signal and a second signal for positioning, and in the second signal generation mode, the transmitter is configured to transmit a third RF excitation signal. This, in turn, enables the portable RF transmitter and receiver to have the capability to communicate with... Figure 1 The dual functionality operates in a similar manner to the existing technology mentioned.

[0033] The system may include a fault range (RTF) module to determine the distance to one or more suspected PIM sources. This RTF module can simplify the identification of PIM sources.

[0034] In another form, the invention is widely found in a method for identifying an external passive intermodulation (PIM) source of an antenna under test (AUT) installed in a desired operating environment, the method comprising: Apply a first RF excitation signal and a second RF excitation signal to the input port of the AUT; Apply a third RF excitation signal to a suspected external PIM source using a portable RF transmitter; and A PIM analyzer is used to measure one or more characteristics of the PIM signal generated by the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal and received by the AUT.

[0035] In yet another form, the invention is widely found in a system for identifying passive intermodulation (PIM) sources of an antenna under test (AUT), the system comprising: A signal generator, connected to the AUT, is used to apply one or more RF excitation signals to the input ports of the AUT; and A portable RF transmitter configured to apply an RF excitation signal to a suspected PIM source.

[0036] In another form, the invention is broadly found in a method for performing passive intermodulation (PIM) or harmonic testing on at least one antenna under test (AUT), the method comprising: Apply one or more RF excitation signals to the input port of the AUT; and Use a portable RF transmitter to apply an RF excitation signal to the suspected PIM source.

[0037] The PIM signal generated by the RF excitation signal and received by the AUT comes from the signal generator and the portable RF transmitter, and can then be used to identify the PIM source.

[0038] The antenna under test can be a phased array antenna. Suspicious PIM sources may include branches of a phased array antenna.

[0039] Any feature described herein may be arbitrarily combined with any one or more other features described herein within the scope of this invention.

[0040] Any reference to prior art in this specification is not and should not be construed as an admission or any implication that the prior art is part of common general knowledge. Attached Figure Description

[0041] Various embodiments of the present invention will be described with reference to the following figures, wherein:

[0042] Figure 1 A schematic diagram of a system for detecting PIM in an AUT according to the prior art is shown.

[0043] Figure 2 A schematic diagram of a system for identifying external passive intermodulation (PIM) sources of the antenna under test (AUT) according to an embodiment of the present invention is shown.

[0044] Figures 3a-3f The effect of changing the amplitude of the third RF excitation signal (F3) on the three-tone PIM signal is shown.

[0045] Figure 4 The graphs of the four IM3 signals with reference F3 power are shown.

[0046] Figure 5 A schematic diagram of a system for identifying external PIM sources of an AUT according to an embodiment of the present invention is shown.

[0047] Figure 6A schematic diagram of a system for identifying external PIM sources of a first AUT and a second AUT according to an embodiment of the present invention is shown.

[0048] Figure 7 A schematic diagram of a system for identifying external PIM sources of an AUT according to an embodiment of the present invention is shown.

[0049] Figure 8 A schematic diagram of a system for identifying external PIM sources of a first AUT and a second AUT according to an embodiment of the present invention is shown.

[0050] Figure 9 A schematic diagram of a system for identifying the PIM source of an AUT according to an embodiment of the present invention is shown.

[0051] Figure 10 A schematic diagram of a system for performing PIM testing in an AUT according to an embodiment of the present invention is shown.

[0052] Figure 11 A method for identifying an external passive intermodulation (PIM) source of an antenna under test (AUT) according to an embodiment of the present invention is shown.

[0053] Preferred features, embodiments, and variations of the present invention will become apparent from the following detailed description, which provides sufficient information for those skilled in the art to carry out the invention. This detailed description should not be construed as limiting the scope of the foregoing summary of the invention in any way. Detailed Implementation

[0054] Figure 2 A schematic diagram of a system 200 for identifying an external passive intermodulation (PIM) source 205 in an antenna under test (AUT) 210 according to an embodiment of the present invention is shown.

[0055] System 200 is able to identify both the location of external PIM sources (such as PIM source 205) and their impact on AUT 210. This allows external PIM sources to be considered based on their impact on AUT 210, which in turn reduces the time and cost associated with processing PIM sources in an AUT operating environment that does not affect AUT 210.

[0056] System 200 includes a portable RF transmitter 215 used by field technicians to detect suspicious PIM sources. Specifically, the portable RF transmitter emits a tone to "encode" the suspicious PIM source. A PIM tester 220, coupled to AUT 210, is then able to measure whether this encoding is detected, thus measuring whether the suspicious PIM source 205 actually causes interference in the network.

[0057] This allows technicians to focus on correcting suspicious PIM sources detected in the network that are impacting the network, while ignoring any suspicious PIM sources that do not affect the network (or significantly affect the network). This, in turn, reduces the time and cost of masking or otherwise handling suspicious PIM sources that do not affect the network.

[0058] PIM tester 220 is configured to apply a first RF excitation signal and a second RF excitation signal to the input port of AUT 210, causing AUT 210 to transmit a signal with frequency F1 and a signal with frequency F2. The first RF excitation signal and the second RF excitation signal excite PIM source 205 and generate a third-order PIM signal (2*F1-F2).

[0059] Choose a first frequency and a second frequency (F1 and F2) such that F1, F2, the third-order PIM signal (2*F1-F2), and any local oscillator (e.g., of the PIM tester 220) do not generate internal interference from any intermodulation (IM) products being created.

[0060] The PIM tester 220 can, for example, use a fault range (RTF) module to analyze the third-order PIM signal to determine the distance to the PIM source 205. This distance data can be useful in helping technicians identify the physical location of the PIM source 205.

[0061] The portable RF transmitter 215 includes a local oscillator 215a configured to generate a third RF excitation signal at a frequency of F3 and transmit such signal from its antenna 215b. As will be readily understood by those skilled in the art, the portable RF transmitter 215 further includes an amplifier 215c, a bandpass filter 215d, and other components.

[0062] Frequency F3 is selected to excite PIM source 205 and generate a third-order PIM signal (F1+F2-F3) that falls within the receiver band of the PIM tester.

[0063] Once configured to transmit the F3 signal, the portable RF transmitter 215 is used to manually scan the area to apply a third RF excitation signal to suspected external PIM sources (including PIM source 205). Specifically, the RF transmitter 215 is moved around so that the antenna 215b directs the third RF excitation signal to different areas in order to identify PIM source 205.

[0064] When the portable RF transmitter 215 is transmitting the third RF excitation signal, the PIM tester 205 is configured to measure one or more characteristics of the PIM signal (i.e., the three-tone PIM signal (F1+F2-F3) and the two-tone PIM signal (2*F1-F2)) generated by the first RF excitation signal, the second RF excitation signal and the third RF excitation signal and received by the AUT.

[0065] The PIM tester 220 determines the influence of the suspected external PIM source 205 on the AUT 210 based on the amplitude of the three-tone PIM signal, especially with reference to the two-tone PIM signal.

[0066] In one embodiment, PIM tester 220 determines the impact of a suspected external PIM source 205 by determining the coexistence of a three-tone PIM signal (F1+F2-F3, referred to as IM3New) and a two-tone PIM signal (2*F1-F2) above a certain threshold.

[0067] Once it is determined whether PIM source 205 is affecting AUT 210 and therefore whether it needs to be corrected, technicians can correct PIM source 205, reassess AUT 210, and potentially address other suspected PIM sources.

[0068] While the portable RF transmitter 215 has been described as being held by a technician to detect suspicious PIM sources, in other embodiments, the portable RF transmitter 215 can be mounted on, for example, a robot, autonomous vehicle, or drone. As a result, the technician does not actually need to approach the suspicious PIM source.

[0069] The amplitude of the third RF excitation signal can be selected such that if the PIM source 205 is affecting the AUT 210, only the three-tone PIM signal is received at the AUT 210. Alternatively, the third RF excitation signal can be transmitted at multiple amplitudes to determine whether the PIM source 205 is affecting the AUT 210, may be affecting the AUT 210, or does not affect the AUT 210. Typically, the third tone is modulated to mark its products. In the case of CW tone amplitude modulation, amplitude shift keying allows for clear identification of the products because these are the only signals that will have amplitude shift keying at the same rate. In the case of biphasic modulation, phase shift keying allows for clear separation of the products generated by the third tone.

[0070] Figures 3a-3f The effect of changing the amplitude of the third RF excitation signal (F3) on the three-tone PIM signal is shown. The amplitudes of the first and second excitation signals are equal and constant in all figures, resulting in a constant two-tone PIM signal (2*F1-F2,IM3).

[0071] Figures 3a-3cIt shows the effect with a certainty ( Figure 3a ), and has potential impacts ( Figure 3b ) and has no influence ( Figure 3c Each of the multiple PIM sources has a third RF excitation signal (F3) with an amplitude lower than that of the first and second excitation signals. (As from...) Figures 3a-3c It can be seen that the three-tone PIM signal (F1+F2-F3,IM3') only exists in PIM sources with a definite influence. Figure 3a ).

[0072] Figure 3d-3f It shows the effect with a certainty ( Figure 3d ), and has potential impacts ( Figure 3e ) and has no influence ( Figure 3f Each of the PIM sources has a third RF excitation signal (F3) with an amplitude equal to the amplitudes of the first and second excitation signals. (Example from...) Figure 3d-3f It can be seen that the three-tone PIM signal (F1+F2-F3,IM3') exists in the PIM source with a definite influence ( Figure 3d ) and potentially influential PIM sources ( Figure 3e ).

[0073] In this way, by using two different amplitudes for the third RF excitation signal (F3), the system is able to determine whether the PIM source has a definite effect, a possible effect, or no effect on the AUT.

[0074] exist Figures 3a-3f The model used makes the following assumptions: - The amplitudes of F1, F2, and F3 are A1, A2, and A3, respectively; - The amplitude of IM3 created by 2*F1-F2 is - The amplitude of IM3new created by F1+F2-F3 is - The amplitudes of F1 and F2 are similar; - In the dB term, A4 = 20Log10(3) - 20Log10(4) + 40Log10(A1) + 20Log10(A2) + 20Log10(α3), where α3 depends on the PIM source. -A5=20log10(3)-20log10(2)+20log10(A1)+20log10(A2)+20log10(A3)+20log10(α3) A change of -1dB corresponds to a 12% increase in amplitude. -When all A1, A2, and A3 are equal, the factor -20Log10(2) that is the difference between the three-tone IM3 and the two-tone IM3 is 6dB. - The PIM source was not saturated by F1 and F2, nor was it saturated by F3; -PIM slope 3:1 model; and -PIM source is -60dBm at 2×43dBm excitation. - IM3 and IM3New are both low-side products (e.g., the Rx band of interest is only low-side).

[0075] And the following results: ΔA4=2*ΔA1+ΔA2 For example, where A4 = -60dBm, and A1 and A2 = 43dBm. A1 and A2 decreased to 40 dBm A4 = A4 - (6 + 3) A4 = -69dBm ΔA5=ΔA1+ΔA2+ΔA3 For example, A5 = -60dBm, and A1, A2, A3 = 41dBm. A3 increased to 43dBm A5 = A5 + (0 + 0 + 2) A5 = -58dBm A5 = A4 + 6dB, where A1, A2, and A3 are equal; For example, where A4 = -60dBm, and A1 and A2 = 43dBm. A5 = A4 + 6, where A3 = 43 dBm A5 = -54dBm

[0076] The inventors have also observed the effect of the amplitude of the third RF excitation signal (F3) on the third-order PIM signal.

[0077] Specifically, the spectrum analyzer is connected to a 4-way microstrip combiner, where one input of the combiner is terminated and the other three signal inputs are connected to three separate signal generators.

[0078] The first RF excitation signal and the second RF excitation signal (F1 and F2) are injected into the combiner at frequencies of 1001MHz and 1001.02MHz respectively, with a power level of -25dBm.

[0079] The third RF excitation signal (F3) is injected into the third port of the combiner at a frequency of 1001.05MHz and scanned in power levels between -50dBm and 0dBm in steps of 5dB.

[0080] Four IM3 signals were simultaneously measured on the spectrum analyzer, namely: IM3F1F2=2*F1-F2=1000.98MHz IM3F1F2F3=F1+F2-F3=1000.97MHz IM3F1F3=2*F1-F3=1000.95MHz IM3F2F3=2*F2-F3=1000.99MHz

[0081] Figure 4 The graphs of the four IM3 signals with reference F3 power are shown.

[0082] As from Figure 4 It can be seen that: 1) The amplitude of F3 in the double tone IM3 is only affected by the amplitude of F3 when the amplitude of F3 is 10dBm higher than the amplitudes of F1 and F2. 2) The amplitudes of IM3F1F2 begin to change upwards, and then a similar decrease is seen in IM3 products containing F3; and 3) The amplitude of IM3F1F2F3 in the three notes IM3 is equal to that of IM3F1F2, and the amplitude of F3 is about 6dB lower than that of F1 and F2.

[0083] The inventors believe that a common amplitude change will occur when the PIM source begins to compress or saturate.

[0084] Now return to Figure 2 The portable RF transmitter 215 can take any suitable form, such as handheld, enabling it to be moved to a suspected PIM source.

[0085] The portable RF transmitter 215 may include an elongated rod from which a third RF excitation signal is emitted. This configuration allows a user to apply a third RF excitation signal to a suspected external PIM source while keeping his or her body away from the suspected external PIM source, thereby reducing the likelihood that the person's body will shield the PIM.

[0086] Although the above description refers to the third excitation signal in the singular, those skilled in the art will readily understand that different AUT configurations, as well as different first and second excitation signal configurations, will require different third excitation signal frequencies. Therefore, the portable RF transmitter 215 is configured to generate the third RF excitation signal at one of a plurality of different operating frequencies that it can operate at. In other words, the portable RF transmitter 215 is configurable with respect to its operating frequency.

[0087] Although the system 200 described above utilizes a portable RF transmitter 215, a portable RF transceiver can also be used. In this case, the receiver portion of the portable RF transceiver can be used to first identify the location of a suspected PIM source in a manner similar to probe 120, upon which further analysis of the PIM source can be conducted.

[0088] Figure 5 A schematic diagram of a system 500 for identifying an external PIM source 205 in an AUT 210 according to an embodiment of the present invention is shown.

[0089] System 500 is similar to System 200, but includes a portable RF transceiver 505 instead of a portable RF transmitter 215.

[0090] The portable RF transceiver includes a transmitter section 505a similar to a portable RF transmitter 215 and a receiver section 505b similar to a probe 120.

[0091] In use, the portable RF transceiver 505 first receives a two-tone PIM signal (F1F2-IM3), which allows a technician to identify the location of the PIM source 205 by scanning an area. The portable RF transceiver 505 may include a display associated with the receiver, configured to display the amplitude of the two-tone PIM signal. The portable RF transceiver 505 may also be configured to transmit an alarm (e.g., an audible alarm) when the two-tone PIM signal exceeds a threshold.

[0092] The portable RF transceiver 505 can function much like a scanning device and can provide the operator with a signal indicating the presence of a PIM source. In particular, the transceiver 505 can be configured, for example, to beep louder or at a higher frequency the closer it is to the PIM source.

[0093] Similarly, the portable RF transceiver 505 can function as, or provide, an integrated compass to facilitate triangulation of PIM sources. Furthermore, the portable RF transceiver 505 can be used to generate a map of the area including the identified PIM sources, or can provide input to another device or module to enable the generation of a map of the area including the identified PIM sources. This map can then be used to identify and locate all PIM sources and their potential impact on the system, enabling the operator to make better decisions regarding the area.

[0094] Once the location of the PIM source 205 has been identified, the portable RF transceiver 505 can be configured to operate in transmit mode, in which the portable RF transceiver 505 transmits a third RF excitation signal. Specifically, the portable RF transceiver 505 can be configured to operate in a switching manner between a first mode and a second mode, allowing it to switch between operation in a first PIM positioning mode and a second signal generation mode.

[0095] The portable RF transceiver 505 includes a switch 505c for this purpose, which allows the transmitting section 505a and the receiving section 505b to be selectively coupled to the antenna 215b.

[0096] System 500 includes a PIM tester 220' coupled to antenna 210. PIM tester 220' may be similar to or the same as PIM tester 220, but is shown in more detail. PIM tester 220' includes a local oscillator for generating a first excitation signal and a second excitation signal, an amplifier, a bandpass filter, and related components for outputting the first and second excitation signals to AUT 210 and receiving PIM signals from AUT 210.

[0097] Although the example above shows a single AUT, those skilled in the art will readily understand that the system and method can be applied to multiple AUTs.

[0098] Figure 6 A schematic diagram of a system 600 for identifying an external PIM source 205 in a first AUT 210a and a second AUT 210b according to an embodiment of the present invention is shown.

[0099] System 600 is similar to system 500, but has a first AUT 210a and a second AUT 210b, and a first PIM tester 220a and a second PIM tester 220b coupled to the respective first AUT 210a and second AUT 210b.

[0100] The first PIM tester 220a and the second PIM tester 220b are identical to the PIM tester 220', but are configured to generate RF excitation signals of different frequencies. Specifically, the first PIM tester 220a is configured to generate a first RF excitation signal at frequency F1 and a second RF excitation signal at frequency F2, and the second PIM tester 220b is configured to generate a fourth RF excitation signal at frequency F4 and a fifth RF excitation signal at frequency F5. As outlined above, the portable RF transceiver 505 is configured to generate a third RF excitation signal.

[0101] Each of the first PIM tester 220a and the second PIM tester 220b can be configured to detect a three-tone PIM signal based on the RF excitation signal they transmit and a third RF excitation signal from the portable RF transceiver 505.

[0102] Alternatively, the first PIM tester and the second PIM tester can be configured to each emit a single RF excitation signal (e.g., the first PIM tester emits a first RF signal F1, and the second PIM tester emits a second RF signal F2).

[0103] While the above embodiments describe pure tone signals, other embodiments may use base transceiver station (BTS) radio signals to excite the PIM source.

[0104] Figure 7 A schematic diagram of a system 700 for identifying an external PIM source 205 in an AUT 210 according to an embodiment of the present invention is shown.

[0105] System 700 is similar to System 200, but has a BTS radio 720 instead of the PIM tester 220. The BTS radio is configured to output an RF excitation signal in the form of a pulse envelope signal on the downlink of band A.

[0106] The system includes a portable RF transmitter 715 similar to a portable RF transmitter 215, but configured to transmit a pulse envelope signal at a frequency of F3.

[0107] The encoded PIM signal (encoded by F3) is then received at BTS radio 720 as a rise in impulse noise floor.

[0108] Figure 8 A schematic diagram of a system 800 for identifying an external PIM source 205 in a first AUT 210a and a second AUT 210b according to an embodiment of the present invention is shown.

[0109] System 800 is similar to System 700, but extends to the use of a first BTS radio 720a and a second BTS radio 720b, as well as a first AUT 210a and a second AUT 210b.

[0110] The first BTS radio 720a outputs signals in frequency band A, and the second BTS radio 720b outputs signals in frequency band B.

[0111] While the example above illustrates the identification of external PIM sources, those skilled in the art will readily understand that the method and system can be used in relation to any type of PIM source. In particular, the techniques described herein can be used to troubleshoot PIM faults within complex RF systems, such as antennas.

[0112] Figure 9 A schematic diagram of a system 900 for identifying a PIM source 905 in an AUT 210a according to an embodiment of the present invention is shown.

[0113] System 900 is similar to system 700, but in which the AUT includes a phased array antenna 910, which includes multiple radiating elements, and the PIM source 905 is located in (or associated with) one of the radiating elements.

[0114] The portable RF transmitter 715 is used in the same way for external PIM sources, but with a different radiating element pointing towards the antenna itself to help identify the location and influence of the PIM source 905.

[0115] Figure 10 A schematic diagram of a system 1000 for performing PIM testing in an AUT 210 according to an embodiment of the present invention is shown.

[0116] System 1000 is similar to System 200, but in which PIM tester 220 is configured to apply only a first RF excitation signal to the input port of AUT 210, causing AUT 210 to transmit a signal at frequency F1, and portable RF transmitter 215 to transmit a signal at frequency F2 from its antenna 215b.

[0117] The first RF excitation signal from AUT 210 and the second RF excitation signal from portable RF transmitter 215 excite the PIM source 205 and generate PIM signals (2*F1-F2 and 2*F2-F1) falling within the receiver frequency band of the PIM tester.

[0118] System 1000 may not be able to identify the location and impact of external PIM sources in the same way as System 200, but it is better than... Figure 2 The system 200 is simpler.

[0119] The signal F2 from the portable RF transmitter 215 is typically at least as strong as signal F1, and can be much stronger, because the level of the third-order product received at AUT 210 will depend largely on the power level of the F2 signal.

[0120] In an alternative embodiment, the frequency of the portable RF transmitter 215 can be changed from F2 to F3, wherein, F3 = 2 * F2. This results in a second-order PIM product (instead of a third-order one), namely, F3 - F1.

[0121] Some benefits of this approach are that, because F1 and F3 have a much larger separation, the need for filter 215d is greatly reduced. This also enables broadband functionality, as narrowband filters are not required for each transmit / receive plan.

[0122] Furthermore, F3 is out-of-band, which would typically require a license to transmit from AUT 210. However, the portable RF transmitter 215 operates at a much lower transmission level because it only needs to match the power of F1 after a path loss that is typically at least 30 dB, due to the lower order of the product. Thus, the portable RF transmitter 215 can be operated licensed without a license.

[0123] Similarly, embodiments of the present invention include a system in which the AUT transmits signals at frequencies F1 and F2, and the portable RF transmitter 215 transmits signals at frequencies F3 and F4.

[0124] This system can detect the presence of PIM products based on two signals occurring at frequencies 2*F1-F2 or 2*F2-F1, and can also detect the presence of PIM products together based on three signals occurring at frequencies F1+F2-F3, F1-F2+F3, and -F1+F2+F3. The three frequency products are generated only from the PIM source under investigation, and the product with frequency F4 (e.g., F1+F2-F4) can be used for detection. The detection can be performed out-of-band, or even the power level of the F4 signal can be selected as low to save power.

[0125] The portable RF transmitter 215 can detect third-order products generated by its own signals (such as 2*F3-F4 and 2*F4-F3).

[0126] The exemplary embodiments described above can be generalized to many signals and many antennas at many frequencies.

[0127] In its most general form, “n” excitation signals are transmitted from the AUT and “m” signals are transmitted from the portable RF transmitter. For system testing against an intermodulation product order of “0”, the number of products generated solely from the AUT is P_AUT = (2n + O - 1)! / O! (2n - 1)!, and the number of intermodulation products generated solely from the handheld transmitter is P_transmitter = (2m + O - 1)! / O! (2m - 1)!. The total number of tones is P_total = (2(n + m) + O - 1)! / O! (2(n + m) - 1)!. Depending on the two sources (i.e., the AUT and the portable RF transmitter), the number of mixed tones is P_mixed = P_total - P_AUT - P_transmitter. The above details are special cases where n = 2, m = 1, and o = 3.

[0128] It is important to note that not all PIM products are detectable; some PIM products at DC or higher harmonics may be outside the band of interest. During normal operation, P_AUT products can be monitored to ensure that the portable RF transmitter does not alter the bias conditions of the nonlinear junction. P_mixing is an encoded product that identifies whether nearby nonlinearities are influential. P_transmitter products can be used to identify any nonlinearities near the mobile transmitter.

[0129] While the example above illustrates PIM testing, the system can be modified to perform harmonic testing. In this case, an RF excitation signal in the 800-900MHz range can create a second harmonic in the 1800MHz range. This configuration is particularly useful for cellular base stations operating in different frequency bands.

[0130] Figure 11 A method 1100 for identifying an external passive intermodulation (PIM) source for an antenna under test (AUT) according to an embodiment of the present invention is shown. The AUT is installed in a desired operating environment, and the method may be similar to or equivalent to the method performed with respect to the system described above.

[0131] In step 1105, a first RF excitation signal and a second RF excitation signal are applied to the input port of the AUT. As outlined above, the first RF excitation signal and the second RF excitation signal may have frequencies F1 and F2.

[0132] In step 1110, a third RF excitation signal is directly applied to the suspected external PIM source using a portable RF transmitter.

[0133] In step 1115, one or more characteristics of the PIM signal generated by the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal and received by the AUT are measured. As outlined above, this may include comparing the amplitude of the three-tone PIM signal with the amplitude of the two-tone PIM signal generated from the first RF excitation signal and the second RF excitation signal.

[0134] While method 1100 uses a first RF excitation signal and a second RF excitation signal at the AUT, in an alternative embodiment, the method uses only a single RF excitation signal at the AUT. Similarly, while only a single (third) excitation signal is used at the portable RF transmitter, in an alternative embodiment, the method uses multiple RF excitation signals at the portable RF transmitter.

[0135] Although the above description refers to the third-order PIM signal (IM3) of the two-tone PIM signal of 2*F1-F2, those skilled in the art will readily understand that the corresponding third-order PIM signal is provided with 2*F2-F1, and the corresponding method is also applied to the low-side IM and the high-side IM.

[0136] Advantageously, the system and method described above provide an efficient way to handle PIMs in antennas installed in their operating environment. In particular, the system and method are able to identify both the location of PIM sources (including external PIM sources) and the impact of such PIM sources on the AUT. This, in turn, allows external PIM sources to be considered based on their impact on the AUT, which further reduces the time and cost associated with handling PIM sources in the AUT's operating environment.

[0137] In this specification and claims (if any), the word "comprising" and its derivatives including "including" and "containing" include each of the stated integers, but do not exclude the inclusion of one or more additional integers.

[0138] Throughout this specification, the terms "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in one or more combinations in any suitable manner.

[0139] According to regulations, the invention has been described in language that is more or less specific to structural or methodological features. It should be understood that the invention is not limited to the specific features shown or described, as the means described herein include preferred forms for carrying out the invention. Therefore, the invention is claimed in any form or with modifications within the appropriate scope of the appended claims (if any) as properly interpreted by those skilled in the art.

Claims

1. A system for identifying an external passive intermodulation (PIM) source of at least one antenna under test (AUT), the AUT being installed in a desired operating environment, characterized in that, The system includes: A PIM analyzer, connected to the AUT, is used to apply a first RF excitation signal and a second RF excitation signal to the input port of the AUT; and A portable RF transmitter configured to transmit a third RF excitation signal to each of a plurality of suspicious external PIM sources by directing the portable RF transmitter to each of the plurality of suspicious external PIM sources; The PIM analyzer is configured to measure one or more characteristics of a PIM signal generated by the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal and received by the AUT.

2. The system according to claim 1, characterized in that, The portable RF transmitter is configured to generate the third RF excitation signal at a selected frequency among a plurality of different operating frequencies.

3. The system according to claim 1, characterized in that, The third RF excitation signal is generated at a frequency such that the resulting PIM signal from the third RF excitation signal is at a frequency within the receiver band of the PIM analyzer.

4. The system according to claim 3, characterized in that, The resulting PIM signal measured by the PIM analyzer includes a third-order PIM signal from the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal.

5. The system according to claim 1, characterized in that, The first RF excitation signal and the second RF excitation signal include signals generated using one or more local oscillators.

6. The system according to claim 1, characterized in that, The first RF excitation signal and the second RF excitation signal include BTS radio signals, wherein the BTS radio signals include pulse envelope signals.

7. The system according to claim 1, characterized in that, It is further configured to determine the effect of a suspected external PIM source that applies the third RF excitation signal to the AUT on the AUT.

8. The system according to claim 7, characterized in that, It is configured to determine the influence of the suspected external PIM source based on the amplitude of the third-order PIM signal from the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal.

9. The system according to claim 1, characterized in that, The system further includes a second AUT, which is configured to be tested simultaneously with the first AUT.

10. The system according to claim 9, characterized in that, It further includes a second PIM analyzer connected to the second AUT.

11. The system according to claim 1, characterized in that, The portable RF transmitter is configured to apply the third RF excitation signal to the suspected external PIM source by applying the third RF excitation signal to the vicinity of the suspected external PIM source.

12. The system according to claim 11, characterized in that, The portable RF transmitter is configured to apply the third RF excitation signal within approximately 1 m of the suspected external PIM source.

13. The system according to claim 1, characterized in that, The portable RF transmitter includes an elongated rod, wherein the third RF excitation signal is emitted from its end.

14. The system according to claim 1, characterized in that, The portable RF transmitter includes a receiver for receiving one or more PIM signals, wherein the receiver is configured to determine the amplitude of a third-order PIM signal from the first RF excitation signal and the second RF excitation signal.

15. The system according to claim 14, characterized in that, It further includes a display associated with the receiver, the display being configured to display the amplitude of the PIM signal.

16. The system according to claim 14, characterized in that, It is configured to issue an alarm when the amplitude of the signal is higher than a threshold.

17. The system according to claim 14, characterized in that, The portable RF transmitter and receiver are configured to operate in a switching manner between a first mode and a second mode, such that it can operate in a first PIM positioning mode and a second signal generation mode. In the first PIM positioning mode, the receiver is configured to receive PIM from the first RF excitation signal and the second RF excitation signal for positioning, and in the second signal generation mode, the transmitter is configured to transmit the third RF excitation signal.

18. A method for identifying an external passive intermodulation (PIM) source for at least one antenna under test (AUT), the AUT being installed in a desired operating environment, characterized in that, The method includes: A first RF excitation signal and a second RF excitation signal are applied to the input port of the AUT; A third RF excitation signal is applied to each of the plurality of suspected external PIM sources by directing a portable RF transmitter to each of the multiple suspected external PIM sources; and A PIM analyzer is used to measure one or more characteristics of the PIM signal received by the AUT, which is generated by the first RF excitation signal, the second RF excitation signal, and the third RF excitation signal.

19. A system for performing passive intermodulation modulation (PIM) testing or harmonic testing on at least one antenna under test (AUT), characterized in that, The system includes: A signal generator, connected to the AUT, for applying one or more RF excitation signals to the input port of the AUT; and A portable RF transmitter configured to apply an RF excitation signal to each of a plurality of suspected external PIM sources by directing the portable RF transmitter to each of the plurality of suspected external PIM sources.

20. The system according to claim 19, characterized in that, The one or more RF excitation signals include a single tone.

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