CN109075808B

CN109075808B - Passive intermodulation interference cancellation method and device

Info

Publication number: CN109075808B
Application number: CN201680082731.2A
Authority: CN
Inventors: 王磊; 李晶; 陈莹莹; 谢尔盖·莫宁
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2016-02-29
Filing date: 2016-02-29
Publication date: 2021-02-09
Anticipated expiration: 2036-02-29
Also published as: CN109075808A; WO2017147759A1

Abstract

A passive intermodulation interference cancellation method and a device are used for solving the problem that the passive intermodulation interference affects the receiving performance of communication equipment. A passive intermodulation interference cancellation apparatus comprising: the acquisition module is used for acquiring transmitting signals from a plurality of transmitting channels; the frequency shifting module is used for respectively carrying out frequency shifting on the plurality of transmitting signals acquired by the acquisition module; the nonlinear transformation module is used for carrying out nonlinear transformation on the plurality of transmitting signals after frequency shifting to generate cancellation signals; and the reverse superposition module is used for reversely superposing the cancellation signal on the receiving signal so as to cancel the passive intermodulation interference in the receiving signal. When the communication equipment with a plurality of transmitting channels receives the receiving signal, the passive intermodulation interference in the receiving signal can be counteracted, and the receiving performance of the communication equipment is prevented from being influenced.

Description

Passive intermodulation interference cancellation method and device

Technical Field

The present disclosure relates to the field of wireless communications technologies, and in particular, to a Passive inter-modulation (PIM) interference cancellation method and apparatus.

Background

Passive intermodulation interference is an important factor limiting the capacity of wireless communication systems. Passive intermodulation interference is caused by the non-linear characteristics of various devices in the transmit path (e.g., duplexers, antennas, feed lines, rf line connectors, etc.). Due to the high-power characteristic of the wireless communication system, a passive device in the antenna feed system can generate a strong nonlinear effect, so that a group of signals with new frequencies, namely passive intermodulation signals, can affect the receiving performance of communication equipment if the passive intermodulation signals fall within a receiving frequency band and the power exceeds the minimum amplitude of useful signals in the system, and at the moment, the passive intermodulation signals are called passive intermodulation interference.

With the continuous increase of the bandwidth of the communication equipment, the influence of the passive intermodulation interference on the signal reception is larger and larger.

In summary, in a wireless communication system, there is a problem that passive intermodulation interference affects the receiving performance of a communication device.

Disclosure of Invention

In view of the above, the present application provides a passive intermodulation interference cancellation method and apparatus, so as to solve the problem that the passive intermodulation interference existing in the wireless communication system affects the receiving performance of the communication device.

In a first aspect, the present application provides a passive intermodulation interference cancellation apparatus, comprising:

the acquisition module is used for respectively acquiring digital intermediate frequency transmission signals from the plurality of transmission channels;

the frequency shifting module is used for respectively carrying out frequency shifting on the plurality of digital intermediate frequency transmitting signals acquired by the acquisition module according to the radio frequency band corresponding to each transmitting channel in the plurality of transmitting channels, the frequency interval of the radio frequency bands corresponding to different transmitting channels and the radio frequency band corresponding to one receiving channel in the plurality of receiving channels so as to enable the radio frequency signals corresponding to the offset signals generated after nonlinear conversion of the plurality of digital intermediate frequency transmitting signals after frequency shifting to fall into the radio frequency receiving band of the receiving channel;

the nonlinear conversion module is used for carrying out nonlinear conversion on the plurality of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting module to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel;

and the reverse superposition module is used for reversely superposing the generated cancellation signal on the digital intermediate frequency receiving signal so as to cancel the passive intermodulation interference in the digital intermediate frequency receiving signal.

The passive intermodulation interference is interference on a radio frequency receiving signal generated by nonlinear conversion among a plurality of transmitted radio frequency signals caused by a nonlinear device, and the passive intermodulation interference can be generated among the radio frequency signals transmitted among different transmitting channels.

By adopting the scheme, the passive intermodulation interference possibly generated among different transmitting channels is considered, the acquisition module acquires the digital intermediate frequency transmitting signals from the plurality of transmitting channels respectively, the frequency shifting module carries out frequency shifting on the digital intermediate frequency transmitting signals and then carries out nonlinear conversion by the nonlinear conversion module so as to generate offset signals for offsetting the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channels, therefore, the offset of the passive intermodulation interference can be realized under the application scene with a plurality of transmitting channels, and the problem that the passive intermodulation interference affects the receiving performance of communication equipment in a wireless communication system is solved.

In one possible implementation, the nonlinear transformation module is further configured to: before carrying out nonlinear conversion on a plurality of paths of digital intermediate frequency transmitting signals subjected to frequency shifting by a frequency shifting module to generate cancellation signals for canceling passive intermodulation interference in digital intermediate frequency receiving signals on a receiving channel, determining a multi-element nonlinear substrate used in the nonlinear conversion, wherein the element number of the multi-element nonlinear substrate is equal to the channel number of a plurality of transmitting channels; determining a coefficient of each nonlinear substrate in the multivariate nonlinear substrate;

the nonlinear conversion module is specifically configured to, when performing nonlinear conversion on the multiple paths of digital intermediate frequency transmission signals subjected to frequency shifting by the frequency shifting module to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency reception signals on the reception channel: and calculating a plurality of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting module according to the coefficients of the multiple nonlinear substrates and each nonlinear substrate to obtain a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel.

By adopting the scheme, the nonlinear transformation module determines the form of nonlinear transformation by determining the nonlinear substrate used by the nonlinear transformation and the coefficient of the nonlinear substrate, and the cancellation signal obtained after the nonlinear transformation can be used for canceling the passive intermodulation interference signal.

In one possible implementation, the nonlinear transformation module, when determining the coefficients of each of a set of nonlinear bases, is specifically configured to: when a counteracting signal is generated for the first time, presetting the coefficient of each nonlinear substrate in the multi-element nonlinear substrates; when a cancellation signal is generated subsequently, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is solved according to the error signal;

the error signal is a difference value between a digital intermediate frequency receiving signal received last time and a cancellation signal generated last time.

By adopting the scheme, the nonlinear conversion module presets the coefficient of each nonlinear substrate in the multiple nonlinear substrates when generating the cancellation signal for the first time, and the coefficient of the nonlinear substrate is solved according to the error signal when generating the cancellation signal for the subsequent time, so that the coefficient of the nonlinear substrate solved by the nonlinear conversion module is more accurate, the generated cancellation signal is more accurate, and the passive intermodulation interference can be more accurately counteracted.

In one possible implementation, each of the plurality of digital intermediate frequency transmit signals includes: a digital intermediate frequency transmitting signal at the current moment on a transmitting channel where the digital intermediate frequency transmitting signal is located; and/or the digital intermediate frequency transmitting signal of a plurality of moments before the current moment on the transmitting channel where the digital intermediate frequency transmitting signal is located;

the current moment is the moment when the generated cancellation signal is reversely superposed on the digital intermediate frequency receiving signal.

By adopting the scheme, the digital intermediate frequency transmitting signal is not only related to the digital intermediate frequency transmitting signal at the current moment, but also related to the transmitting signals at a plurality of moments before the current moment, namely, the memory characteristic is added in the expression of the digital intermediate frequency transmitting signal, so that the digital intermediate frequency transmitting signal is more accurately expressed, the expression of the counteracting signal is more accurate, and the passive intermodulation interference is counteracted more accurately.

In one possible implementation, the plurality of transmission channels respectively correspond to different radio frequency bands; or a plurality of transmitting channels are connected with the same antenna, and the antenna polarization directions corresponding to different transmitting channels are different; or a plurality of transmitting channels are connected with different antennas, wherein one transmitting channel corresponds to one antenna; or the plurality of transmitting channels are combined by the radio frequency matrix network and then connected with the plurality of antennas.

In a second aspect, the present application provides a passive intermodulation interference cancellation method, which may be performed by a communication device, such as: the base station or the wireless terminal executes, the method comprises:

respectively acquiring digital intermediate frequency transmitting signals from a plurality of transmitting channels;

for one of the plurality of receive channels, performing the following: according to the radio frequency band corresponding to each transmitting channel in the plurality of transmitting channels, the frequency interval of the radio frequency band corresponding to different transmitting channels and the radio frequency band corresponding to the receiving channel, respectively carrying out frequency shifting on the obtained plurality of digital intermediate frequency transmitting signals, so that the radio frequency signals corresponding to offset signals generated after nonlinear conversion of the plurality of digital intermediate frequency transmitting signals after frequency shifting fall into the radio frequency receiving frequency band of the receiving channel; carrying out nonlinear conversion on the plurality of digital intermediate frequency transmitting signals after frequency shifting to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel; and reversely superposing the generated cancellation signal on the digital intermediate frequency receiving signal so as to cancel the passive intermodulation interference in the digital intermediate frequency receiving signal.

By adopting the scheme, the passive intermodulation interference possibly generated among different transmitting channels is considered, the digital intermediate frequency transmitting signals are respectively obtained from the plurality of transmitting channels, the frequency of the digital intermediate frequency transmitting signals is shifted and then the nonlinear conversion processing is carried out, so that the offset signals for offsetting the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channels are generated, the offset of the passive intermodulation interference can be realized under the application scene with a plurality of transmitting channels, and the problem that the passive intermodulation interference affects the receiving performance of communication equipment in a wireless communication system is solved.

In a possible implementation manner, before performing nonlinear conversion on the multiple frequency-shifted digital intermediate frequency transmission signals to generate a cancellation signal for canceling passive intermodulation interference in the digital intermediate frequency reception signal on the reception channel, the method further includes: determining a multi-element nonlinear substrate used in nonlinear transformation, wherein the element number of the multi-element nonlinear substrate is equal to the channel number of a plurality of transmitting channels; determining a coefficient of each nonlinear substrate in the multivariate nonlinear substrate;

the method for carrying out nonlinear conversion on the frequency-shifted multi-channel digital intermediate frequency transmitting signals to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel comprises the following steps: and calculating the plurality of digital intermediate frequency transmitting signals after the frequency shifting according to the coefficients of the multiple nonlinear substrates and each nonlinear substrate to obtain a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel.

By adopting the scheme, the nonlinear transformation form is determined by determining the nonlinear substrate used by the nonlinear transformation and the coefficient of the nonlinear substrate, and the cancellation signal obtained after the nonlinear transformation can be used for canceling the passive intermodulation interference signal.

In one possible implementation, determining the coefficients for each of a set of non-linear bases includes: when a counteracting signal is generated for the first time, presetting the coefficient of each nonlinear substrate in the multi-element nonlinear substrates;

when a cancellation signal is generated subsequently, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is solved according to the error signal; the error signal is a difference value between a digital intermediate frequency receiving signal received last time and a cancellation signal generated last time.

By adopting the scheme, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is preset when the cancellation signal is generated for the first time, and the coefficient of the nonlinear substrate is solved according to the error signal when the cancellation signal is generated subsequently, so that the solved coefficient of the nonlinear substrate is more accurate, the generated cancellation signal is more accurate, and the passive intermodulation interference can be more accurately cancelled.

In one possible implementation, each of the plurality of digital intermediate frequency transmit signals includes: a digital intermediate frequency transmitting signal at the current moment on a transmitting channel where the digital intermediate frequency transmitting signal is located; and/or the digital intermediate frequency transmitting signal of a plurality of moments before the current moment on the transmitting channel where the digital intermediate frequency transmitting signal is located; the current moment is the moment when the generated cancellation signal is reversely superposed on the digital intermediate frequency receiving signal.

In a third aspect, the present application provides a passive intermodulation interference cancellation apparatus, which connects a plurality of transmitting channels and a receiving channel of a communication device, including:

the frequency shifting circuit is used for respectively carrying out frequency shifting on the digital intermediate frequency transmitting signals on each transmitting channel in the plurality of transmitting channels according to the radio frequency band corresponding to each transmitting channel in the plurality of transmitting channels, the frequency interval of the radio frequency band corresponding to different transmitting channels and the radio frequency band corresponding to one receiving channel in the plurality of receiving channels, so that the radio frequency signals corresponding to the offset signals generated after nonlinear conversion of the plurality of digital intermediate frequency transmitting signals after frequency shifting fall into the radio frequency receiving band of the receiving channel;

the canceller is used for carrying out nonlinear conversion on the plurality of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting circuit to generate cancelling signals for cancelling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel;

and the adder is used for reversely superposing the cancellation signal generated by the canceller on the digital intermediate frequency receiving signal received on the receiving channel so as to cancel the passive intermodulation interference in the digital intermediate frequency receiving signal and outputting the digital intermediate frequency receiving signal on which the cancellation signal is reversely superposed.

By adopting the scheme, the frequency shifting circuit carries out frequency shifting on the digital intermediate frequency transmitting signals acquired from the plurality of transmitting channels and then carries out nonlinear conversion by the canceller so as to generate the cancelling signals for cancelling the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel, thereby realizing the cancellation of the passive intermodulation interference under the application scene with a plurality of transmitting channels and solving the problem that the passive intermodulation interference influences the receiving performance of the communication equipment in a wireless communication system.

In one possible implementation, the canceller is further configured to: before carrying out nonlinear conversion on a plurality of paths of digital intermediate frequency transmitting signals subjected to frequency shifting by a frequency shifting circuit and generating a cancellation signal for canceling passive intermodulation interference in digital intermediate frequency receiving signals on a receiving channel, determining a multi-element nonlinear substrate used in the nonlinear conversion, wherein the element number of the multi-element nonlinear substrate is equal to the channel number of a plurality of transmitting channels; determining a coefficient of each nonlinear substrate in the multivariate nonlinear substrate;

the canceller specifically performs nonlinear conversion on the multiple paths of digital intermediate frequency transmission signals subjected to frequency shifting by the frequency shifting circuit to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency reception signals on the reception channel, and is configured to: and calculating a plurality of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting circuit according to the coefficients of the multiple nonlinear substrates and each nonlinear substrate to obtain a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel.

By adopting the scheme, the canceller determines the form of the nonlinear transformation by determining the nonlinear substrate used by the nonlinear transformation and the coefficient of the nonlinear substrate, and the cancellation signal obtained after the nonlinear transformation can be used for canceling the passive intermodulation interference signal.

In one possible implementation, the canceller, when determining the coefficient of each non-linear basis in the set of non-linear bases, is specifically configured to: when a counteracting signal is generated for the first time, presetting the coefficient of each nonlinear substrate in the multi-element nonlinear substrates; when a cancellation signal is generated subsequently, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is solved according to the error signal;

By adopting the scheme, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is preset when the canceller generates the cancellation signal for the first time, and the coefficient of the nonlinear substrate is solved according to the error signal when the cancellation signal is generated subsequently, so that the coefficient of the nonlinear substrate solved by the canceller is more accurate, the generated cancellation signal is more accurate, and the passive intermodulation interference can be more accurately counteracted.

Drawings

Fig. 1 is a schematic diagram of an intermodulation interference cancellation scheme when a communication device provided by the present application has one transmitting channel;

fig. 2 is a schematic diagram of a scene of a multiband radio frequency combiner provided in the present application;

fig. 3 is a schematic diagram of a scheme for canceling passive intermodulation interference in a second multi-antenna scenario provided in the present application;

fig. 4 is a schematic diagram of a scheme for canceling passive intermodulation interference in scenario four of a radio frequency matrix network according to the present application;

fig. 5 is a schematic diagram of a passive intermodulation interference cancellation scheme provided herein;

fig. 6 is a flowchart of a passive intermodulation interference cancellation method provided in the present application;

fig. 7 is a schematic diagram of a passive intermodulation interference cancellation method in a first scenario provided by the present application;

fig. 8 is a flowchart of a passive intermodulation interference cancellation method in a first scenario provided by the present application;

FIG. 9 is a schematic diagram of an adaptive solution process under one scenario provided by the present application;

fig. 10 is a schematic diagram of a passive intermodulation interference cancellation method in a second scenario provided by the present application;

fig. 11 is a flowchart of a passive intermodulation interference cancellation method in a second scenario provided by the present application;

fig. 12 is a schematic diagram of an adaptive solution process in a second scenario provided by the present application;

fig. 13 is a schematic diagram of a passive intermodulation cancellation apparatus provided in the present application.

Detailed Description

The following detailed description is provided for a better understanding of the above-described objects, aspects and advantages of the present application. The detailed description sets forth various embodiments of the devices and/or methods via the use of diagrams and/or examples of block diagrams, flowcharts, and the like. In these block diagrams, flowcharts, and/or examples, one or more functions and/or operations are included. Those skilled in the art will understand that: the various functions and/or operations within these block diagrams, flowcharts or examples can be implemented, individually and collectively, by a wide variety of hardware, software, firmware, or any combination of hardware, software and firmware.

In the present application, a scheme for passive intermodulation interference cancellation is proposed for a scenario where there are multiple transmit channels and passive intermodulation interference is related to signals transmitted on the multiple transmit channels.

In the scheme, a communication device, such as a base station, respectively acquires digital intermediate frequency transmission signals from a plurality of transmission channels; carrying out frequency shifting on the obtained plurality of digital intermediate frequency transmitting signals; for one receiving channel in a plurality of receiving channels, carrying out nonlinear conversion on a plurality of acquired digital intermediate frequency transmitting signals to generate a counteracting signal for counteracting passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel; and reversely superposing the generated cancellation signal on the digital intermediate frequency receiving signal so as to cancel the passive intermodulation interference in the digital intermediate frequency receiving signal.

The passive intermodulation interference is interference on a radio frequency receiving signal generated by nonlinear conversion among a plurality of transmitted radio frequency signals caused by a nonlinear device, and the passive intermodulation interference can be generated among the radio frequency signals transmitted among different transmitting channels. In the application, passive intermodulation interference possibly generated between different transmitting channels is considered, so that the data intermediate frequency transmitting signals are respectively acquired from the plurality of transmitting channels to generate cancellation signals for canceling the passive intermodulation interference, and the passive intermodulation interference between the plurality of transmitting channels can be effectively cancelled.

Next, a description will be given of a scenario to which the present application can be applied. In these scenarios, the communication device has multiple transmit channels, and the passive intermodulation interference is related to signals transmitted on the multiple transmit channels.

It should be noted that the following descriptions should not be construed as limiting the scope of the protection claimed in the present application.

Scene one and a plurality of transmitting channels respectively correspond to different transmitting frequency bands

In the engineering implementation, the scenario may also be referred to as a "multiband radio frequency combiner". In this scenario, the radio frequency signals transmitted by the communication device are located in different frequency bands. At this time, the source signal generating the passive intermodulation interference is not a signal on one frequency band, but a signal obtained by frequency-shifting and combining a plurality of transmitting signals located in a plurality of frequency bands.

Scene two, a plurality of transmitting channels respectively correspond to different transmitting antennas

In wireless communication systems, multiple antenna techniques are often employed to increase spectrum utilization and resource transmission efficiency.

In the multi-antenna technology, a plurality of transmitting antennas and a plurality of receiving antennas are configured on communication equipment, signals transmitted by different antennas are combined in a radiation field space near the antennas, and the combined signals can excite passive intermodulation interference at a common intermodulation interference source.

Here, the common passive intermodulation interference source may be a metal body in the radiation field near the antenna, such as: the antenna comprises an internal metal frame of the antenna, a metal rod on the front surface of the antenna, a multi-polarization antenna surrounding frame, a metal holding rod of a multi-polarization antenna radiation field and the like. After the multiple radio frequency signals transmitted by the communication equipment are combined in the radiation field space near the antenna, the passive intermodulation interference is excited at the public passive intermodulation interference source.

Scene three, multiple transmitting channels respectively corresponding to different polarization directions of transmitting antenna

In a third scenario, the communication device has multiple transmission channels, where the multiple transmission channels are connected to oscillators of the same antenna in different polarization directions, that is, the polarization modes adopted by signals transmitted on different transmission channels are different.

Such as: the communication device has two transmission channels, which are respectively connected with the + 45-degree polarization direction and the-45-degree polarization direction of the same antenna.

Scene four, a plurality of transmission channels respectively correspond to a plurality of input ports of the radio frequency matrix network

In a fourth scenario, the transmission signals on the multiple transmission channels are mixed by a radio frequency matrix network (such as a radio frequency bridge, a butler matrix) and then fed to the antenna, and these signals can excite a passive intermodulation interference source (such as a welding spot with a burr inside the antenna, a stress-failed screw, and the like) in the antenna, thereby forming passive intermodulation interference. The passive intermodulation interference is superposed in the received signal through the radio frequency matrix network again before being reversely input into the receiving channel.

In the above, a scenario applicable to the present application is introduced, it should be noted that the above scenario is only an example, and as long as the communication device has a plurality of transmitting channels, the passive intermodulation interference is related to signals transmitted on the plurality of transmitting channels, the scheme provided in the present application can be used to eliminate the passive intermodulation interference.

In addition, in the actual engineering implementation, there may be situations where the above several scenarios occur in a mixed manner, such as: the communication device is provided with a plurality of transmitting antennas, and each transmitting antenna transmits signals of a plurality of radio frequency bands; for another example: the communication device has a plurality of transmit antennas, each transmit antenna in turn transmitting a transmit signal on a different transmit path, with a different polarization direction, and so on.

When the communication device has only one transmit channel, the interference cancellation scheme shown in fig. 1 may be employed to cancel passive intermodulation interference.

In the scheme shown in fig. 1, the passive intermodulation interference is cancelled on the digital intermediate frequency side by a canceller. In fig. 1, PIM RXC is a canceller for cancelling passive intermodulation interference, x is a digital intermediate frequency transmit signal transmitted on a transmit channel, Rx is a digital intermediate frequency receive signal received on a receive channel, y is a cancel signal generated by RXC for cancelling passive intermodulation interference, and Rx is a digital intermediate frequency receive signal from which passive intermodulation interference is removed.

In fig. 1, according to the transmission direction of the signals, the transmission signals are transmitted in the transmission direction from left to right, and the channel through which the corresponding transmission signal passes is a transmission channel; the received signals are transmitted in the transmission direction from right to left, and the channel through which the corresponding received signal passes is a receiving channel.

For the transmission signal, the baseband signal is Up-sampled by a Sampling Rate Converter (SRC), the Up-sampled baseband transmission signal is subjected to Digital Up-conversion (DUC) to obtain a Digital intermediate frequency transmission signal, the Digital intermediate frequency transmission signal is subjected to Digital-to-Analog conversion (DAC) to generate an Analog intermediate frequency transmission signal, the Analog transmission signal is subjected to frequency mixing (i.e., the Analog intermediate frequency transmission signal is mixed with a radio frequency transmission local oscillator signal _ TX LO) to obtain an Analog radio frequency transmission signal, the Analog radio frequency transmission signal is subjected to signal amplification by a Power Amplifier (PA), and then the Analog radio frequency transmission signal is input to a transmission Duplexer (TX Duplexer, TX _ DUP) and then input to an antenna feed system (not shown in the figure). The digital intermediate frequency transmitting signal x output by the DUC is subjected to frequency shifting (x exp (jwt)), and then is input into a canceller (PIM RXC), and the PIM RXC generates a cancelling signal which is reversely superposed on the digital intermediate frequency receiving signal to cancel passive intermodulation interference.

For a received signal, an Analog radio Frequency received signal from an antenna feed system (not shown in the figure) is subjected to signal amplification processing by a Low Noise Amplifier (LNA) after passing through a receiving Duplexer (RX duplex, RX _ DUP), optionally, the amplified Analog radio Frequency received signal is subjected to filtering processing by a Surface Acoustic Wave (SAW) filter, the filtered Analog radio Frequency received signal is subjected to receiving mixing (i.e., the Analog radio Frequency signal is mixed with a received local oscillator signal RX _ Lo of radio Frequency) to obtain an Analog Intermediate Frequency received signal, and then the Analog Intermediate Frequency received signal is subjected to Intermediate Frequency filtering processing by an Intermediate Frequency (IF) filter and then converted into a digital Intermediate Frequency received signal by an Analog to digital converter (ADC)).

After a cancellation signal output by the canceller is reversely superposed on a Digital intermediate frequency receiving signal, passive intermodulation interference is cancelled, the obtained Digital intermediate frequency signal is processed by a Digital Down Converter (DDC) to become a Digital baseband receiving signal, and then the Digital baseband receiving signal is sent to SRC for downsampling processing, so that the intermediate frequency high-speed sampling point rate is converted into the baseband low-speed sampling point rate.

Where x may be a single-carrier signal or a multi-carrier signal. And taking x as the input of the canceller, obtaining a cancellation signal y after the cancellation signal is processed by the canceller, and subtracting the cancellation signal y from the received digital intermediate frequency signal Rx to obtain a digital intermediate frequency receiving signal Rx without passive intermodulation interference.

The interference cancellation scheme shown in fig. 1 is not applicable to the scenarios one to four described above, and is illustrated as follows.

First, the interference cancellation scheme shown in fig. 1 is not suitable for scenario one

Fig. 2 shows a scenario of multi-band radio frequency combining. Fig. 2 shows the passive intermodulation interference cancellation process on the first receiving channel, and the passive intermodulation interference cancellation processes on the other receiving channels are similar and are not shown in the figure.

Since the passive intermodulation interference is formed by frequency-shifting and combining a plurality of transmitting signals at radio frequencies, in order to realize the cancellation of the passive intermodulation interference by using the canceller architecture shown in fig. 1, the transmitting signals need to be mixed at a digital intermediate frequency, and then the mixed signals are input into the canceller to generate cancellation signals. However, this implementation has a great limitation, which is mainly reflected in the following two aspects:

1. the parameters required for mixing the transmitted signals at a digital intermediate frequency are difficult to obtain

As shown in fig. 2, when mixing the transmission signals at the digital intermediate frequency, it is necessary to perform frequency shift combining on the signals of each radio frequency band and accurately configure combining parameters, such as frequency point and initial phase. Wherein, the initial phase of the digital intermediate frequency is consistent with the combining phase of the analog radio frequency. It is difficult to obtain phase information for the modulator of the analog radio frequency at the digital intermediate frequency, which results in difficult to obtain the parameters needed to mix the transmitted signal at the digital intermediate frequency.

2. Mixing of the transmitted signals at a digital intermediate frequency requires a higher sampling rate

In the implementation shown in fig. 2, since the transmit signals are mixed at the digital intermediate frequency, and the intermodulation signals are generated after the radio frequency transmit signals on the transmit channel are mixed, the cancellation of the passive intermodulation interference after the intermediate frequency signal mixing at the digital intermediate frequency needs to reflect the relative frequency difference (frequency interval) of the radio frequency signals at the digital intermediate frequency. Sometimes, the frequency difference of the radio frequency is much higher than the sampling rate (or sampling point rate) of the intermediate frequency, so that the mixed radio frequency signal is expressed at the digital intermediate frequency, which requires a higher sampling rate (or sampling point rate) and is costly in engineering.

For simplicity of description, assume that there are two transmit channels: the device comprises a transmitting channel 1 and a transmitting channel 2, wherein the two transmitting channels respectively correspond to two radio frequency bands. The intermediate frequency corresponding to the transmitting channel 1 is 0MHz, the bandwidth is 10M, the intermediate frequency corresponding to the transmitting channel 2 is 10MHz, and the bandwidth is 20M; the radio frequency corresponding to the transmitting channel 1 is 1.8GHz, and the radio frequency corresponding to the transmitting channel 2 is 2.1 GHz. At this time, to express the mixed signal at the digital intermediate frequency, a sampling rate of (2120MHz-1795MHz) × 3 is required, so that the different transmitting channels can be distinguished at the digital intermediate frequency, and such a high sampling rate is difficult to realize at the digital intermediate frequency due to a high cost.

Along the interference cancellation scheme shown in fig. 1, it is difficult to mix the transmit signals of multiple transmit channels at a digital intermediate frequency, and then use the mixed signals to regenerate the cancellation signals.

Secondly, the interference cancellation scheme shown in fig. 1 is not suitable for scenario two

If a scheme for canceling the passive intermodulation interference in the second scenario with multiple antennas is along the interference cancellation scheme shown in fig. 1, as shown in fig. 3, for simplicity of description, two transmitting antennas and two receiving antennas are taken as an example in the scheme shown in fig. 3, and in practice, the number of the transmitting antennas and the number of the receiving antennas are not limited to two.

As shown in fig. 3, the multiple transmission signals are mixed to generate a mixed signal, and then the mixed signal is input to the canceller to generate a cancellation signal. The expression for the mixed signal may be:

c＝a*x₀*exp(jw₀t)+b*x₁*exp(jw₁t)

wherein x is₀Is a digital intermediate frequency transmission signal of a transmission channel 1, x₁Is a digital intermediate frequency transmission signal of a transmission channel 2, w₀Is the frequency difference, w, of the digital intermediate frequency transmission signal and the radio frequency transmission signal of the transmission channel 1₁Which is the frequency difference between the digital intermediate frequency transmit signal of the transmit channel 2 and the radio frequency signal, a, b represent the complex parameters of transmission (including amplitude and phase) of the transmission path from the two channels to the common passive intermodulation interference source, which parameters such as a, b are not usually accurately known at the digital intermediate frequency, so that in the multiple antenna scenario two, it is difficult to accurately cancel the passive intermodulation interference using the scheme shown in fig. 1.

Thirdly, the interference cancellation scheme shown in fig. 1 is not suitable for scenario four

If following the interference cancellation scheme shown in fig. 1, one scheme for canceling passive intermodulation interference in scenario four of the radio frequency matrix network may be as shown in fig. 4. Fig. 4 only exemplifies two transmitting antennas and two receiving antennas, and in practice, the number of transmitting antennas and receiving antennas is not limited to two. Fig. 4 illustrates an implementation manner in which multiple transmission signals are mixed and input to a canceller to generate a cancellation signal, where the signal input to the canceller may be denoted as c ═ a × x₀*exp(jw₀t)+b*x₁*exp(jw₁t), where a and b represent complex transmission parameters (including phase and amplitude) from the duplexer to the radio frequency matrix network and then to the passive intermodulation interference source on the antenna, the parameters a and b cannot be accurately known, so that the input signal of the passive intermodulation interference in the matrix feed network scene is difficult to accurately represent.

FIG. 5 shows the present applicationSchematic diagram of a passive intermodulation interference cancellation scheme is provided. As shown in fig. 5, in the present application, a plurality of transmission channels (e.g., transmission channel 0, transmission channel 1, transmission channel N in fig. 5, where N is a positive integer) are corresponding to a digital intermediate frequency transmission signal (e.g., x in fig. 5)₀、x₁...x_NEtc.) to perform frequency shifting (frequency shift factor is ω in fig. 5₀、ω₁...ω_N) And then sending the data into a canceller for canceling the passive intermodulation interference, wherein the canceller adopts a multivariate nonlinear model. The digital intermediate frequency transmitting signal is subjected to nonlinear conversion in the canceller to obtain a cancellation signal y for canceling the passive intermodulation interference in the digital intermediate frequency receiving signal Rx, and the cancellation signal y is subtracted from the actually received digital intermediate frequency receiving signal Rx to obtain the digital intermediate frequency receiving signal Rx without the passive intermodulation interference.

The process of the passive intermodulation interference cancellation method provided by the present application can be shown in fig. 6, and the specific steps may include:

s601: communication devices, such as: the base station respectively acquires digital intermediate frequency transmitting signals from a plurality of transmitting channels;

the communication system that the communication device in this application may apply to when sending and receiving signals includes but is not limited to: global System for Mobile communications (GSM), Code Division Multiple Access (CDMA) IS-95, Code Division Multiple Access (CDMA) 2000, Time Division Synchronous Code Division Multiple Access (TD-SCDMA), Wideband Code Division Multiple Access (WCDMA), Time Division duplex-Long Term Evolution (TDD LTE), Frequency Division duplex-Long Term Evolution (FDD), Long Term Evolution (Long Term Evolution-Evolution), LTE-Mobile, Personal Mobile phone (WiFi-held), Wireless internet protocol (WiFi-802), Wireless internet protocol (WiFi-11), WiMAX), and various wireless communication systems that evolve in the future.

In this application, the communication device may be a base station or a wireless terminal.

A wireless terminal may refer to a device that provides voice and/or data connectivity to a user, a handheld device having wireless connection capability, or other processing device connected to a wireless modem. Wireless terminals, which may be mobile terminals such as mobile telephones (or "cellular" telephones) and computers having mobile terminals, such as portable, pocket, hand-held, computer-included, or vehicle-mounted mobile devices, may communicate with one or more core networks via a Radio Access Network (e.g., RAN). For example, Personal Communication Service (PCS) phones, cordless phones, Session Initiation Protocol (SIP) phones, Wireless Local Loop (WLL) stations, Personal Digital Assistants (PDAs), and the like. A wireless Terminal may also be referred to as a Subscriber Unit (Subscriber Unit), a Subscriber Station (Subscriber Station), a Mobile Station (Mobile), a Remote Station (Remote Station), an Access Point (Access Point), a Remote Terminal (Remote Terminal), an Access Terminal (Access Terminal), a User Terminal (User Terminal), a User Agent (User Agent), a User Device (User Device), or a User Equipment (User Equipment).

For a GSM system, a Base Station may include a Base Transceiver Station (BTS) and/or a Base Station Controller (BSC); for TD-SCDMA systems, WCDMA systems, a base station may include a node B (NodeB, NB) and/or a Radio Network Controller (RNC); for an LTE system, the base station may be an eNB.

Optionally, the plurality of transmission channels correspond to different radio frequency bands, respectively; or a plurality of transmitting channels are connected with the same antenna entity, and the antenna polarization directions corresponding to different transmitting channels are different; or a plurality of transmitting channels are connected with different antenna entities, wherein one transmitting channel corresponds to one antenna; or the plurality of transmitting channels are combined by the radio frequency matrix network and then connected with the plurality of antennas. The multiple antennas include multiple ports of one antenna entity, each port corresponding to a different polarization direction, and may also include multiple entity antennas;

s602: according to the radio frequency band corresponding to each transmitting channel in the plurality of transmitting channels, the frequency interval of the radio frequency band corresponding to different transmitting channels and the radio frequency band corresponding to the receiving channel, respectively carrying out frequency shifting on the obtained plurality of digital intermediate frequency transmitting signals, so that the radio frequency signals corresponding to offset signals generated after nonlinear conversion of the plurality of digital intermediate frequency transmitting signals after frequency shifting fall into the radio frequency receiving frequency band of the receiving channel;

wherein, the cancellation signal can be a digital intermediate frequency cancellation signal;

optionally, the radio frequency signal corresponding to the cancellation signal falls into the radio frequency receiving frequency band of the receiving channel, where the frequency of the radio frequency signal corresponding to the cancellation signal is the same as the center frequency of the radio frequency receiving frequency band of the receiving channel, and the frequency spectrum of the radio frequency signal corresponding to the cancellation signal partially or completely overlaps with the frequency spectrum of the radio frequency receiving frequency band of the receiving channel.

Alternatively, the frequency shift factor used in frequency shifting may be determined according to different expressions of the non-linear basis.

S603: carrying out nonlinear conversion on the plurality of digital intermediate frequency transmitting signals after frequency shifting to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel;

the communication equipment carries out nonlinear conversion on the plurality of digital intermediate frequency transmitting signals after frequency shifting aiming at one receiving channel in a plurality of receiving channels to generate a counteracting signal for counteracting the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel;

optionally, each of the plurality of digital intermediate frequency transmit signals comprises: a digital intermediate frequency transmitting signal at the current moment on a transmitting channel where the digital intermediate frequency transmitting signal is located; and/or the digital intermediate frequency transmitting signal of a plurality of moments before the current moment on the transmitting channel where the digital intermediate frequency transmitting signal is located;

the current time is the time when the generated cancellation signal is reversely superposed on the digital intermediate frequency receiving signal.

Optionally, the performing a nonlinear conversion on the frequency-shifted multiple digital intermediate frequency transmission signals to generate a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency reception signal on the reception channel may include:

1. determining a multi-element nonlinear substrate used in nonlinear transformation, wherein the element number of the multi-element nonlinear substrate is equal to the channel number of a plurality of transmitting channels;

the expression of the multivariate nonlinear bases can be various, such as a power function base, an orthogonal polynomial base, a piecewise spline base, a trigonometric function base, and the like. The expression of the substrate has no direct influence on the cancellation result of the passive intermodulation interference.

2. Determining a coefficient of each nonlinear substrate in the multivariate nonlinear substrate;

optionally, determining the coefficients of each of a set of non-linear bases may include: when a counteracting signal is generated for the first time, presetting the coefficient of each nonlinear substrate in the multi-element nonlinear substrates; when a cancellation signal is generated subsequently, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is solved according to the error signal; the error signal is a difference value between a digital intermediate frequency receiving signal received last time and a cancellation signal generated last time.

Alternatively, the coefficients in the multivariate nonlinear base can be updated in real time by using adaptive solution criteria or methods such as Least Mean Square (LMS), Least Square (LS), Recursive Least Square (RLS), and the like.

Alternatively, the error signal and the non-linear basis may be separately narrow-band filtered when performing the adaptive solution.

3. And carrying out nonlinear transformation on the plurality of digital intermediate frequency transmitting signals after frequency shifting, and calculating according to the coefficients of the multi-element nonlinear substrate and each nonlinear substrate to obtain a cancellation signal.

Optionally, the passive intermodulation interference is generated when a plurality of digital intermediate frequency transmitting signals are subjected to passive intermodulation, so that the form of expressing the passive intermodulation interference by using the plurality of digital intermediate frequency transmitting signals is various, such as an intra-band intermodulation component, an inter-band third-order intermodulation component, an inter-band fifth-order intermodulation component, and the like. Specifically, which order of intermodulation components of the plurality of digital intermediate frequency transmission signals to express the passive intermodulation interference may be determined according to a combination of the transmission frequency point and the reception frequency point, and the decision process may be implemented by software.

Optionally, when performing nonlinear conversion, a plurality of digital intermediate frequency transmission signals may be mixed, the mixed digital intermediate frequency transmission signal is regarded as a digital intermediate frequency transmission signal, frequency shifting, nonlinear basis selection and coefficient calculation are performed on the mixed digital intermediate frequency transmission signal, and a signal obtained by performing operation according to a nonlinear basis and basis coefficients is used as a component of the cancellation signal.

S604: the cancellation signal generated in step S603 is reversely superimposed on the digital intermediate frequency reception signal to cancel the passive intermodulation interference in the digital intermediate frequency reception signal.

Fig. 7 is a flowchart illustrating a method for cancelling passive intermodulation interference in the foregoing scenario, where fig. 7 takes the case of cancelling passive intermodulation interference in a dual-band hybrid networking scenario as an example. In practice, the multi-band is not limited to two bands.

The passive intermodulation interference under the scene of the dual-band hybrid networking is related to digital intermediate frequency transmitting signals corresponding to two frequency bands. The basic principle of counteracting the passive intermodulation interference generated by the digital intermediate frequency transmitting signals of the dual-band is as follows: on the digital intermediate frequency side, two transmitting signals in different frequency bands are used, and a canceller (for example, PIM RXC in fig. 7) generates a component with the same size and the opposite direction as the actual passive intermodulation interference, so as to cancel the actual passive intermodulation interference.

Based on the above basic principle, the procedure of the passive intermodulation interference cancellation can be as shown in fig. 8, and the steps are as follows:

s801: determining a transmit signal that produces passive intermodulation interference;

when passive intermodulation interference cancellation is performed, x and z are required to be used as input signals of the canceller.

Where PIM RXC is an example of a canceller shown in fig. 5.

The transmit signals that generate passive intermodulation interference are:

tx＝x+z*exp(j*(f_{TX_LO1}-f_{TX_LO0})*t)

wherein x is a transmission signal of a frequency band as an input of a canceller (PIM RXC); z is a transmitted signal in another frequency band as input to a canceller (PIM RXC); f. of_{TX_LO0}Frequency of the radio frequency local oscillator signal of the transmission channel corresponding to x, f_{TX_LO1}And the frequency of the radio frequency local oscillation signal of the transmitting channel corresponding to the z is shown, and t is time.

Both x and z are required as input signals for the canceller when performing passive intermodulation interference cancellation.

S802: selecting a multi-element nonlinear substrate;

the expression of the multivariate nonlinear substrate has various modes, such as a polynomial, a piecewise broken line, a piecewise spline mode and the like, and the expression form of the substrate has no direct influence on the cancellation result of the passive intermodulation interference.

The following describes the cancellation process of passive intermodulation interference by taking a multivariate nonlinear substrate as a multivariate polynomial expression form as an example.

S803: determining a representation of the cancellation signal;

because the passive intermodulation interference is related to digital intermediate frequency transmission signals corresponding to a plurality of frequency bands, a plurality of passive intermodulation products are generated when the passive intermodulation is performed, and the intermodulation products can include the following forms:

in-band intermodulation products, in the form of:

inter-band third order intermodulation products, in the form of:

inter-band fifth order intermodulation products, shaped as:

v＝1，2，3，4；h＝5-v。

where NL (| x |, | z |) represents a multivariate nonlinear basis, conj () represents a conjugate operation, f_{TX_LO0}Representing the frequency, f, of the local oscillator signal of the transmission channel to which x corresponds_{TX_LO1}Representing the frequency, f, of the local oscillator signal of the transmit channel corresponding to z_{RX_LO0}Representing the frequency of the local oscillator signal of the receiving channel corresponding to x. Where the frequency of the local oscillator signal is equal to the center frequency of the transmit band.

When a communication radio frequency system is designed, only intermodulation products below a fifth-order expression are generally concerned, and the higher-order intermodulation products have small components, so that the engineering significance of modeling cancellation is not great.

Under a specific combination of transmitting and receiving frequency points, one or more intermodulation components form passive intermodulation interference of a certain receiving channel, so that the specific decision on which intermodulation component or intermodulation components to use is needed according to the combination of the transmitting and receiving frequency points; for example:

or

Or

Or

Where y is the output signal of the canceller, i.e., the aforementioned cancellation signal.

Determining whether a certain intermodulation component falls into a receiving frequency band after frequency shift according to the relative frequency relationship between a transmitting frequency band and the receiving frequency band;

among the various intermodulation products_{TX_LO0}-f_{RX_LO0}、f_{TX_LO1}-f_{RX_LO0}、2f_{TX_LO0}-f_{TX_LO1}-f_{RX_LO0}All are frequency shift factors, and the frequency shift factors correspond to the expression of a nonlinear substrate one by one.

The presence of the frequency shift factor represents the frequency shifting process in step S602. In fig. 7, the step performed by the multiplier before the input of the canceller PIM RXC is the frequency shift operation, and in fig. 7, the frequency shift factor is represented by ω₀₀、ω₀₁、ω₁₀、ω₁₁And (4) showing. For a detailed description of the frequency shifting, refer to the aforementioned step S602.

The intermodulation products are

The form of (a) is an example for the expression and solution of a multivariate nonlinear substrate.

S804: determining coefficients for each of the plurality of non-linear bases;

the multivariate nonlinear substrate can be expressed as:

wherein p is the degree of the | x (t) | polynomial; p is the maximum degree of the | x (t) | polynomial; q is a polynomial of | z (t) |The number of times of (c); q is the maximum degree of the | z (t) | polynomial; ch (channel)_p，qCoefficients for each of the plurality of non-linear bases.

To further enhance performance, memory characteristics were added to the multivariate nonlinear basis expression:

where m is the delay value for the | x (t) | signal; m is the maximum delay value of the | x (t) | signal; n is the delay value for the | z (t) | signal; n is the maximum delay value for the | z (t) | signal.

The cancellation error can be calculated by the following equation:

wherein, rx₀The received signal (including the passive intermodulation interference signal) of the upper receiving channel in fig. 7 is shown; e.g. of the type₀A cancelled signal representing a first receive channel; k is the delay value for the x signal; k is the maximum delay value for the x signal.

Optionally, the coefficient of the nonlinear substrate may be preset when the cancellation signal is generated for the first time, and when the cancellation signal is generated in the subsequent time, the coefficient of the nonlinear substrate is adaptively solved and updated in real time according to the cancellation error generated for cancelling the passive intermodulation interference last time, where the adaptive solution expression is:

wherein ch_{0，k，m，n，p，q}(t) is a coefficient of a nonlinear basis preset when the cancellation signal is first generated, ch_{0，k，m，n，p，q}And (t +1) is a coefficient of a nonlinear substrate generated after adaptive solution is carried out according to the last cancellation error when the cancellation signal is generated next time, and mu is a step factor in the adaptive coefficient updating process.

Optionally, in order to enhance the modeling performance in some transmission frequency bands (i.e., performing frequency shifting and nonlinear transformation on the multivariate nonlinear selection substrate and the multiple digital intermediate frequency transmission signal to simulate PIM interference falling into a reception frequency band), the error signal and the nonlinear substrate may be separately subjected to narrow-band filtering during adaptive calculation.

The process of performing the adaptive solution may be as shown in fig. 9. Wherein NL₁，NL₂...NL_PQRRepresenting one of the multiple nonlinear substrates.

Wherein, the general formula of the nonlinear substrate generation module is as follows:

(xs)^v*(conj(zs))^h*NL₁(|x|，|z|，|xz|)

(xs)^v*(conj(zs))^h*NL₂(|x|，|z|，|xz|)

…

(xs)^v*(conj(zs))^h*NL_PQR(|x|，|z|，|xz|)

in the application scenario shown in fig. 7, the nonlinear basis generation module is configured to have v equal to 1 and h equal to 0.

In the adaptive calculation process shown in fig. 9, no memory characteristic is added to the transmission signal, and in practical application, the memory characteristic may be added to the transmission signal by setting a delay.

S805: and acquiring a cancellation signal for canceling the passive intermodulation interference.

The expression after adding the memory characteristic to the output of the canceller is:

using the sum canceller output y in FIG. 7₀The adder connected with the canceller subtracts the output of the canceller from the actual received signal containing the passive intermodulation interference, so that the passive intermodulation interference can be cancelled.

The passive intermodulation interference cancellation scheme shown in fig. 7 is an example of the scheme shown in fig. 5, and embodiments not described in detail in the scheme shown in fig. 7 may refer to the description in the scheme shown in fig. 5.

Next, a method for cancelling passive intermodulation interference in a multi-antenna scenario two provided by the present application is described with reference to fig. 10, where fig. 10 exemplifies the cancellation of passive intermodulation interference in a dual-antenna scenario. In practice, the multiple antennas are not limited to dual antennas.

The passive intermodulation interference under the double-antenna scene is related to signals transmitted by two antennas, namely, the two transmitting signals are radiated to the space at the antennas, and are radiated to a common passive intermodulation interference source after being combined in the space, so that the passive intermodulation interference containing the two transmitting signals is generated and then is radiated to two receiving channels.

The basic principle of counteracting the passive intermodulation interference generated under the double-antenna scene is as follows: on the digital intermediate frequency side, the transmitting signals of the two antennas generate a component with the same size and the opposite direction as the actual passive intermodulation interference through a canceller (such as PIM RXC in fig. 10), so as to cancel the actual passive intermodulation interference.

Based on the above basic principle, the procedure of the passive intermodulation interference cancellation can be as shown in fig. 11, and the steps are as follows:

s1101: calculating a transmitting signal radiated to a common passive intermodulation interference source;

in fig. 10, the transmit signals radiated to the common passive intermodulation interference source are:

tx＝(x+βe^jθz)

wherein β is a combined amplitude factor, θ is a combined phase factor, x is a transmit signal in one transmit channel as an input of a canceller (PIM RXC), and z is a transmit signal in another transmit channel as an input of the canceller (PIM RXC).

Optionally, x and z are co-frequency signals.

S1102: selecting a multi-element nonlinear substrate;

there are many ways to express the multivariate nonlinear base, such as polynomial, piecewise broken line, piecewise spline, etc.), and the expression form of the base has no direct influence on the cancellation result of the passive intermodulation interference.

In a multi-antenna application scene, the expression of the multi-element nonlinear substrate needs to reflect amplitude and phase information in a combining process.

The following multivariate nonlinear substrate is taken as an example to illustrate how to obtain the cancellation signal:

S1103: determining a representation of the cancellation signal;

the wireless communication system generates a plurality of intermodulation products when performing passive intermodulation, and the mathematical expression of the intermodulation products can be as follows:

wherein v is 0, 1, 2, 3, h is 0, 1, 2, 3

Wherein f is_{TX_LO0}Frequency of the radio frequency local oscillator signal of the transmission channel corresponding to x, f_{RX_LO0}The frequency of the radio frequency local oscillator signal corresponding to the upper receiving channel in fig. 10. The frequency of the local oscillator signal is equal to the central frequency of the transmitting frequency band;

the expression of the cancellation signal is various, and the following one is taken as an example:

where y is the cancellation signal, f_{TX_LO0}-f_{RX_LO0}The frequency shift factor can be determined according to the expression form of the nonlinear substrate, and the frequency shift factors corresponding to the expression forms of different nonlinear substrates are different. Frequency shift factor w under different nonlinear substrate forms_Δ1Can be determined by the following general formula:

w_Δ1＝v*f_{TX_LO0}-h*f_{TX_LO1}-f_{RX_LO0}

wherein f is_{TX_LO0}Is the frequency of the local oscillator signal of the transmission channel corresponding to z.

The presence of the frequency shift factor represents the frequency shifting process in step S602. In fig. 10, the step performed by the multiplier before the transmission signal is input into the canceller is the frequency shifting process, and in fig. 9, the frequency shifting factor is represented by ω₀₀、ω₀₁、ω₁₀、ω₁₁And (4) showing. For a detailed description of the frequency shifting, refer to the aforementioned step S602.

In order to enhance performance, memory characteristics are increased on the basis of non-linear expression:

where K is a delay value for the x signal, K is a maximum delay value for the x signal, M is a delay value for the | x | signal, M is a | x | signal maximum delay value, N is a delay value for the | z | signal, N is a | z | signal maximum delay value, ch_{k，m，n，g，p，q，r}Is the coefficient of a multivariate nonlinear base, g is | x + β e^jθz | delay value of signal, G is | x + β e^jθMaximum delay value of z | signal.

S1104: determining coefficients for each of the plurality of non-linear bases;

when the passive intermodulation interference is counteracted, the counteracting error is as follows:

err₀＝rx₀-y₀

rx₀the actual received signal (including passive intermodulation interference) for the upper receive channel in fig. 10 is shown.

Optionally, the coefficient of each of the multiple nonlinear bases may be updated in real time through adaptive solution, and the solution formula of the coefficient of each of the multiple nonlinear bases is:

wherein ch_{0，k，m，n，g，p，q，r}(t) is a coefficient of a nonlinear basis preset when the cancellation signal is first generated, ch_{0，k，m，n，g，p，q，r}(t +1) is a coefficient of a nonlinear base generated after adaptive solution is performed according to a previous cancellation error when a cancellation signal is generated next time, mu is a step factor of an adaptive coefficient updating process, and conj () represents conjugate operation.

Optionally, in order to enhance the modeling performance (i.e., selecting a substrate, performing frequency shifting and performing nonlinear transformation to simulate PIM interference falling into a receiving frequency band) in some transmitting frequency bands, narrow-band filtering may be performed on the error signal and the nonlinear substrate respectively when performing adaptive solution.

The process of performing the adaptive solution may be as shown in fig. 12. Wherein NL₁，NL₂...NL_PQRepresenting one of the multiple nonlinear substrates.

(xs)^v*(conj(zs))^h*NL₁(|x|，|z|)

(xs)^v*(conj(zs))^h*NL₂(|x|，|z|)

…

(xs)^v*(conj(zs))^h*NL_PQ(|x|，|z|)

in the application scenario shown in fig. 10, the nonlinear basis generation module is configured to have v equal to 1 and h equal to 0.

In the adaptive calculation process shown in fig. 12, no memory characteristic is added to the transmission signal, and in practical application, the memory characteristic may be added to the transmission signal by setting a delay.

S1105: and acquiring a cancellation signal for canceling the passive intermodulation interference.

By summing the canceller output y in FIG. 10₀The connected summator subtracts the output of the canceller from the actual received signal containing the passive intermodulation interference, so that the cancellation of the passive intermodulation interference can be realized.

The solution shown in fig. 10 can be regarded as an example of the solution shown in fig. 5, and the embodiments not described in detail in the solution shown in fig. 10 can be described in the solution shown in fig. 5.

It should be noted that the passive intermodulation interference cancellation method and apparatus provided by the present application are not limited to be applied in two application scenarios, namely, a multiband radio frequency combining scenario and a multi-antenna scenario.

Fig. 13 is a schematic diagram of a passive intermodulation cancellation apparatus provided in the present application. As shown in fig. 13, the passive intermodulation cancellation apparatus includes:

an obtaining module 1301, configured to obtain digital intermediate frequency transmission signals from multiple transmission channels respectively;

a frequency shifting module 1302, configured to perform frequency shifting on the multiple digital intermediate frequency transmission signals acquired by the acquisition module 1301 according to a radio frequency band corresponding to each of the multiple transmission channels, a frequency interval of the radio frequency bands corresponding to different transmission channels, and a radio frequency band corresponding to one of the multiple reception channels, so that the radio frequency signals corresponding to cancellation signals generated after nonlinear conversion of the multiple digital intermediate frequency transmission signals after frequency shifting fall into the radio frequency reception band of the reception channel;

a nonlinear conversion module 1303, configured to perform nonlinear conversion on the multiple digital intermediate frequency transmit signals subjected to frequency shifting by the frequency shifting module 1302, so as to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receive signals on the receive channel;

and a reverse superposition module 1304, configured to reversely superpose the generated cancellation signal on the digital intermediate frequency reception signal to cancel the passive intermodulation interference in the digital intermediate frequency reception signal.

Optionally, the non-linear transformation module 1303 is further configured to: before performing nonlinear conversion on the multiple paths of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting module 1302 to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel, determining a multi-element nonlinear substrate used in the nonlinear conversion, wherein the element number of the multi-element nonlinear substrate is equal to the channel number of the plurality of transmitting channels; determining a coefficient of each nonlinear substrate in the multivariate nonlinear substrate;

the nonlinear conversion module 1303 is specifically configured to, when performing nonlinear conversion on the multiple paths of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting module 1302 to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel: the plurality of digital intermediate frequency transmission signals subjected to frequency shifting by the frequency shifting module 1302 are calculated according to the coefficients of the multiple nonlinear bases and each nonlinear base, so as to obtain a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency reception signal on the reception channel.

Optionally, the nonlinear transformation module 1303 is specifically configured to, when determining the coefficient of each nonlinear basis in a group of nonlinear bases: when a counteracting signal is generated for the first time, presetting the coefficient of each nonlinear substrate in the multi-element nonlinear substrates; when a cancellation signal is generated subsequently, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is solved according to the error signal;

Optionally, each of the plurality of digital intermediate frequency transmission signals acquired by the acquiring module 1301 includes: a digital intermediate frequency transmitting signal at the current moment on a transmitting channel where the digital intermediate frequency transmitting signal is located; and/or the digital intermediate frequency transmitting signal of a plurality of moments before the current moment on the transmitting channel where the digital intermediate frequency transmitting signal is located;

Optionally, the plurality of transmission channels where the plurality of digital intermediate frequency transmission signals acquired by the acquiring module 1301 are located satisfy: the plurality of transmitting channels respectively correspond to different radio frequency bands; or a plurality of transmitting channels are connected with the same antenna, and the antenna polarization directions corresponding to different transmitting channels are different; or a plurality of transmitting channels are connected with different antennas, wherein one transmitting channel corresponds to one antenna; or the plurality of transmitting channels are combined by the radio frequency matrix network and then connected with the plurality of antennas.

Other alternative implementations of the passive intermodulation cancellation device can refer to the implementations of the passive intermodulation cancellation device in fig. 5 to 12. The obtaining module 1301 may be configured to perform obtaining operation, the frequency shifting module 1302 may be configured to perform frequency shifting operation, the nonlinear transformation module 1303 may be configured to perform nonlinear transformation operation, and the reverse superposition module 1304 may be configured to perform reverse superposition operation. For other optional implementation manners of the obtaining module 1301 performing the obtaining operation, reference may be made to the obtaining operation in fig. 5 to 12, for other optional implementation manners of the frequency shifting module 1302 performing the frequency shifting operation, reference may be made to the frequency shifting operation in fig. 5 to 12, for other optional implementation manners of the nonlinear transformation module 1303 performing the nonlinear transformation operation, reference may be made to the nonlinear transformation operation in fig. 5 to 12, and for other optional implementation manners of the reverse superposition module 1304 performing the reverse superposition operation, reference may be made to the reverse superposition operation in fig. 5 to 12.

Fig. 5 is a schematic structural diagram of the passive intermodulation interference cancellation apparatus shown in fig. 13 in an alternative implementation manner. The passive intermodulation interference cancellation apparatus connects a plurality of transmit channels and a receive channel of a communication device. As shown in fig. 5, the passive intermodulation cancellation apparatus includes:

a frequency shifting circuit 501, configured to shift frequencies of the digital intermediate frequency transmission signals on each of the multiple transmission channels according to a radio frequency band corresponding to each of the multiple transmission channels, a frequency interval of the radio frequency bands corresponding to different transmission channels, and a radio frequency band corresponding to one of the multiple reception channels, so that the radio frequency signals corresponding to cancellation signals generated after nonlinear conversion of the multiple digital intermediate frequency transmission signals after frequency shifting fall into the radio frequency reception band of the reception channel;

a canceller 502, configured to perform nonlinear conversion on the multiple digital intermediate frequency transmit signals subjected to frequency shifting by the frequency shifting circuit 501, and generate a cancellation signal for canceling passive intermodulation interference in the digital intermediate frequency receive signal on the receive channel;

the adder 503 is configured to reversely superimpose the cancellation signal generated by the canceller 502 on the digital intermediate frequency reception signal received on the reception channel to cancel the passive intermodulation interference in the digital intermediate frequency reception signal, and output the digital intermediate frequency reception signal on which the cancellation signal is reversely superimposed.

Optionally, the canceller 502 is further configured to: before performing nonlinear conversion on the multiple paths of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting circuit 501 to generate cancellation signals for canceling passive intermodulation interference in digital intermediate frequency receiving signals on the receiving channel, determining a multi-element nonlinear substrate used in the nonlinear conversion, wherein the element number of the multi-element nonlinear substrate is equal to the channel number of the plurality of transmitting channels; determining a coefficient of each nonlinear substrate in the multivariate nonlinear substrate;

when the canceller 502 performs nonlinear conversion on the multiple paths of digital intermediate frequency transmission signals subjected to frequency shifting by the frequency shifting circuit 501 to generate a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency reception signals on the reception channel, the canceller is specifically configured to: the plurality of digital intermediate frequency transmission signals subjected to frequency shifting by the frequency shifting circuit 501 are calculated according to the coefficients of the multiple nonlinear substrates and each nonlinear substrate to obtain cancellation signals for canceling the passive intermodulation interference in the digital intermediate frequency reception signals on the reception channel.

Optionally, the canceller 502 is specifically configured to, when determining the coefficient of each nonlinear substrate in a group of nonlinear substrates: when a counteracting signal is generated for the first time, presetting the coefficient of each nonlinear substrate in the multi-element nonlinear substrates; when a cancellation signal is generated subsequently, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is solved according to the error signal;

Optionally, the plurality of transmission channels correspond to different radio frequency bands, respectively; or a plurality of transmitting channels are connected with the same antenna, and the antenna polarization directions corresponding to different transmitting channels are different; or a plurality of transmitting channels are connected with different antennas, wherein one transmitting channel corresponds to one antenna; or the plurality of transmitting channels are combined by the radio frequency matrix network and then connected with the plurality of antennas.

The application provides a scheme for counteracting the passive intermodulation interference aiming at a scene that a plurality of transmitting channels exist and the passive intermodulation interference is related to signals transmitted on the plurality of transmitting channels.

As will be appreciated by one skilled in the art, the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the embodiments of the present application without departing from the spirit and scope of the embodiments of the present application. Thus, if such modifications and variations of the embodiments of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to encompass such modifications and variations.

Claims

1. A passive intermodulation interference cancellation apparatus, comprising:

a frequency shifting module, configured to perform frequency shifting on the multiple digital intermediate frequency transmission signals acquired by the acquisition module according to a radio frequency band corresponding to each of the multiple transmission channels, a frequency interval of radio frequency bands corresponding to different transmission channels, and a radio frequency band corresponding to one of the multiple reception channels, so that radio frequency signals corresponding to cancellation signals generated after nonlinear conversion of the multiple digital intermediate frequency transmission signals after frequency shifting fall into the radio frequency reception band of the reception channel; the radio frequency signal corresponding to the cancellation signal falls into the radio frequency receiving frequency band of the receiving channel, wherein the frequency of the radio frequency signal corresponding to the cancellation signal is the same as the central frequency of the radio frequency receiving frequency band of the receiving channel, or the frequency spectrum of the radio frequency signal corresponding to the cancellation signal is partially or completely overlapped with the frequency spectrum of the radio frequency receiving frequency band of the receiving channel;

a nonlinear conversion module, configured to perform, for one receiving channel of multiple receiving channels, the nonlinear conversion on the multiple digital intermediate frequency transmitting signals subjected to the frequency shifting by the frequency shifting module, and generate a cancellation signal for canceling passive intermodulation interference in digital intermediate frequency receiving signals on the receiving channel;

2. The apparatus of claim 1, wherein the non-linear transformation module is further to: before the multi-channel digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting module are subjected to nonlinear conversion to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel,

determining a multivariate nonlinear substrate used in the nonlinear transformation, wherein the number of elements of the multivariate nonlinear substrate is equal to the number of channels of the plurality of transmitting channels;

determining a coefficient for each of the plurality of nonlinear bases;

the nonlinear conversion module is specifically configured to, when performing nonlinear conversion on the multiple paths of digital intermediate frequency transmission signals subjected to frequency shifting by the frequency shifting module to generate cancellation signals for canceling passive intermodulation interference in digital intermediate frequency reception signals on the reception channel:

and calculating the plurality of digital intermediate frequency transmitting signals subjected to frequency shifting by the frequency shifting module according to the multiple nonlinear substrates and the coefficient of each nonlinear substrate to obtain a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency receiving signal on the receiving channel.

3. The apparatus of claim 2, wherein the nonlinear transformation module, in determining the coefficients for each of a set of nonlinear bases, is specifically configured to:

presetting the coefficient of each nonlinear substrate in the multi-element nonlinear substrate when the counteracting signal is generated for the first time;

when the offset signal is generated subsequently, the coefficient of each nonlinear substrate in the multiple nonlinear substrates is solved according to the error signal;

the error signal is a difference value between the digital intermediate frequency receiving signal received last time and the cancellation signal generated last time.

4. The apparatus according to any one of claims 1 to 3, wherein each of the plurality of digital intermediate frequency transmission signals acquired by the acquisition module comprises:

a digital intermediate frequency transmitting signal at the current moment on a transmitting channel where the digital intermediate frequency transmitting signal is located; and/or

The digital intermediate frequency transmitting signals of a plurality of moments before the current moment on a transmitting channel where the digital intermediate frequency transmitting signals are located;

and the current moment is the moment when the generated cancellation signal is reversely superposed on the digital intermediate frequency receiving signal.

5. The device according to any one of claims 1 to 3, wherein the plurality of transmission channels where the plurality of digital intermediate frequency transmission signals acquired by the acquisition module are located satisfy:

the plurality of transmitting channels respectively correspond to different radio frequency bands; or

The plurality of transmitting channels are connected with the same antenna, and the antenna polarization directions corresponding to different transmitting channels are different; or

The plurality of transmitting channels are connected with different antennas, wherein one transmitting channel corresponds to one antenna; or

The plurality of transmitting channels are combined by the radio frequency matrix network and then connected with the plurality of antennas.

6. A passive intermodulation interference cancellation method, comprising:

respectively carrying out frequency shifting on the obtained plurality of digital intermediate frequency transmitting signals according to the radio frequency band corresponding to each transmitting channel in the plurality of transmitting channels, the frequency interval of the radio frequency bands corresponding to different transmitting channels and the radio frequency band corresponding to one receiving channel in the plurality of receiving channels, so that the radio frequency signals corresponding to offset signals generated after nonlinear conversion of the plurality of digital intermediate frequency transmitting signals after frequency shifting fall into the radio frequency receiving band of the receiving channel; the radio frequency signal corresponding to the cancellation signal falls into the radio frequency receiving frequency band of the receiving channel, wherein the frequency of the radio frequency signal corresponding to the cancellation signal is the same as the central frequency of the radio frequency receiving frequency band of the receiving channel, or the frequency spectrum of the radio frequency signal corresponding to the cancellation signal is partially or completely overlapped with the frequency spectrum of the radio frequency receiving frequency band of the receiving channel;

for one receiving channel in a plurality of receiving channels, performing the nonlinear conversion on the plurality of digital intermediate frequency transmitting signals after the frequency shifting, and generating a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel;

and reversely superposing the generated cancellation signal on the digital intermediate frequency receiving signal to cancel the passive intermodulation interference in the digital intermediate frequency receiving signal.

7. The method of claim 6, further comprising, before performing a nonlinear conversion on the frequency-shifted multiple digital intermediate frequency transmit signals to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receive signals on the receive channel:

determining a coefficient for each of the plurality of nonlinear bases;

the nonlinear conversion is performed on the frequency-shifted multi-channel digital intermediate frequency transmitting signals to generate cancellation signals for canceling passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel, and the method comprises the following steps:

and calculating the plurality of digital intermediate frequency transmitting signals after the frequency shifting according to the multiple nonlinear substrates and the coefficient of each nonlinear substrate to obtain a cancellation signal for canceling the passive intermodulation interference in the digital intermediate frequency receiving signals on the receiving channel.

8. The method of claim 7, wherein determining coefficients for each of a set of non-linear bases comprises:

9. The method of any one of claims 6 to 8, wherein each of the plurality of digital intermediate frequency transmit signals comprises:

10. The method according to any one of claims 6 to 8,