RF Cancellation Circuit

Abstract

The present application discloses a radio frequency cancellation circuit, including: a transmitting antenna, a receiving antenna, a transmitting channel, a receiving channel and a digital radio frequency memory, wherein the digital radio frequency memory is connected to the transmitting channel and the receiving channel respectively; the transmitting channel is used to generate a transmitting coupling signal corresponding to the transmitting signal, and the transmitting coupling signal is output or input to the digital radio frequency memory by the transmitting antenna respectively; the digital radio frequency memory is used to generate an equal-amplitude anti-phase cancellation signal corresponding to the transmitting coupling signal and the transmitting leakage signal existing in the receiving channel, so as to realize the radio frequency cancellation of the receiving channel. According to the embodiment of the present application, the designed digital radio frequency memory can be used to complete the transmission leakage cancellation of the continuous wave radar to improve the transmission and reception isolation. Compared with the traditional radio frequency cancellation signal generation method using a vector modulator or a phase shift attenuator, there is no device for the signal to flow directly through, which reduces the insertion loss of the system and improves the quality of the cancellation signal generation.

Description

Technical Field

[0001] The present application belongs to the technical field of radio frequency cancellation, and in particular to a radio frequency cancellation circuit. Background Art

[0002] Compared with pulse radar, continuous wave radar has significant advantages such as small transmission power, low intercept probability, low power consumption and low circuit complexity. Therefore, it has important application value in miniaturized seeker, radar, fuze and electronic warfare jammer systems. In order to improve the isolation between transmitter and receiver, RF cancellation technology can be used to solve the signal leakage problem of continuous wave radar.

[0003] At present, RF cancellation mainly uses vector modulators or phase shift attenuators to modulate the transmit coupled signal through amplitude and phase modulation to generate a cancellation signal with equal amplitude and opposite phase to the transmit leakage signal for RF cancellation. However, it has the following disadvantages: first, the insertion loss introduced is relatively large; second, since the RF cancellation signal is mainly generated by the vector modulator or phase shift attenuator, the signal quality is relatively low. Summary of the invention

[0004] The embodiment of the present application provides a radio frequency cancellation circuit, which is used to at least solve the problem of large insertion loss and low cancellation signal quality in the radio frequency cancellation system in the related art.

[0005] The embodiment of the present application provides a radio frequency cancellation circuit, comprising: a transmitting antenna, a receiving antenna, a transmitting channel, a receiving channel and a digital radio frequency memory, wherein the digital radio frequency memory is connected to the transmitting channel and the receiving channel respectively;

[0006] The transmitting channel is used to generate a transmitting coupled signal corresponding to the transmitting signal, and output or input the transmitting coupled signal from the transmitting antenna to the digital radio frequency memory;

[0007] The digital radio frequency memory is used to generate equal-amplitude anti-phase cancellation signals corresponding to the transmit coupling signal and the transmit leakage signal existing in the receive channel, so as to realize radio frequency cancellation of the receive channel.

[0008] The RF cancellation circuit of the embodiment of the present application utilizes the designed digital RF memory to realize the RF cancellation of the transmission leakage and the near-end blocking signal in the receiving link, and can complete the transmission leakage cancellation of the continuous wave radar to improve the transmission and reception isolation; compared with the traditional RF cancellation signal generation method using a vector modulator or a phase shift attenuator, no device is introduced through which the signal directly flows, which reduces the insertion loss of the system and improves the quality of the cancellation signal generation, thereby greatly improving the effect of the RF cancellation, thereby improving the RF cancellation capability of the continuous wave radar and improving the performance of the radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0010] Figure 1 is a structural schematic diagram of a radio frequency cancellation circuit provided in an embodiment of the present application;

[0011] Figure 2 It is a structural schematic diagram of a digital radio frequency memory provided in an embodiment of the present application.

[0012] Reference numerals:

[0013] Transmitting antenna 100, receiving antenna 200, cancellation database 600, sampling module 700, processing control module 800,

[0014] Digital radio frequency memory 300, down converter 301, analog-to-digital converter ADC302, memory 303, signal conditioning circuit 304, digital-to-analog converter DAC305, filter 306, up converter 307, amplitude control module 308, controller 309, programmable frequency synthesizer 310,

[0015] A first amplifying module 401 , a bandpass filtering module 402 , a first coupling module 403 , a second coupling module 501 , a second amplifying module 502 , and a third coupling module 503 . DETAILED DESCRIPTION

[0016] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0017] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0018] Compared with pulse radar, continuous wave radar has significant advantages such as small transmission power, low intercept probability, low power consumption and lower circuit complexity. Therefore, it has important application value in systems such as miniaturized seekers, radars, fuzes and electronic warfare jammers.

[0019] In radar applications, isolation is a critical indicator. Insufficient isolation will have at least two effects: first, the receiving noise will deteriorate, and the transmitter sideband noise may even directly drown out weak signals; second, the sensitivity will decrease, and large transmission leakage signals can push the receiving amplifier to saturation. Pulse radar can use electronic switches to switch the transmit and receive signals to obtain an isolation of more than 30dB, and the isolation can be very ideal through time-sharing and electrical isolation of the transmit and receive signals. However, in addition to using a dual-antenna system, continuous wave radar can only improve the transmit and receive isolation through RF cancellation technology.

[0020] In order to improve the isolation between transmit and receive, and to address the signal leakage problem, in the development history of continuous wave radar, the methods to solve the signal leakage problem mainly include: using dual antenna spatial isolation, using circulator as isolation element, using radio frequency cancellation technology and using intermediate frequency cancellation technology.

[0021] The use of dual antenna space isolation, that is, using one antenna for transmission and one antenna for reception, and using various different absorbing materials between the two antennas and good antenna design, can improve the isolation between transmission and reception and increase the suppression of leakage. Its isolation is mainly limited by the reflection of antenna side lobes, near targets and ground. Usually this isolation technology can achieve an isolation of more than 70dB. The disadvantage of dual antenna space isolation technology is that it increases the volume and weight of the entire radar. This method is not suitable for occasions with high volume and weight requirements, and it does not conform to the development trend of low power consumption and miniaturization of electronic equipment. In addition, if the transmission signal power increases, the isolation will also decrease.

[0022] A circulator is used as an isolation element. When the radar system uses a single antenna to achieve dual functions of transmission and reception, the circulator is the component that realizes the isolation of transmission and reception. Due to the limitation of the circulator isolation (generally 25-30dB), the isolation of the transceiver is very limited and far from meeting the requirements.

[0023] Using RF cancellation technology, part of the transmission power is taken as the feedthrough signal, and the amplitude and phase of the feedthrough signal are modulated by a vector modulator under the control of a manual or closed-loop control circuit, so that the modulated feedthrough signal is equal in amplitude and opposite in phase to the leakage signal entering the receiver. Finally, the modulated feedthrough signal is fed into the receiving channel and superimposed with the leakage signal to cancel each other. In engineering practice, a closed-loop control circuit is usually used to control the vector modulator to form an adaptive closed-loop control cancellation system.

[0024] The intermediate frequency cancellation technology is used, that is, an adaptive closed-loop control cancellation system similar to the RF cancellation technology is used in the intermediate frequency circuit to cancel the leakage signal. A feedback cancellation system can be established in the intermediate frequency range to cancel the carrier leakage signal to obtain an extremely narrow stopband bandwidth. The advantage of this method is that the leakage signal is cancelled at the front end of the intermediate frequency amplifier, thereby reducing the noise; the disadvantage is that it cannot solve the problem of saturation of the low-noise amplifier at the front end of the transmitter and receiver caused by the leakage signal, and it needs to be used in conjunction with other methods.

[0025] Among these measures to improve the isolation between transmitters and receivers, RF cancellation technology is an active cancellation suppression, which is the main technology to solve the isolation between transmitters and receivers, and is also a must for almost all linear frequency modulation continuous wave radars with high requirements. The importance of RF cancellation technology lies not only in its ability to suppress microwave leakage signals to a certain extent, but also in its ability to prevent receiver saturation and reduce AM noise, thus ensuring the application of other transmission leakage signal suppression technologies.

[0026] At present, RF cancellation mainly uses vector modulators or phase shift attenuators to modulate the transmit coupled signal through amplitude and phase modulation to generate a cancellation signal with equal amplitude and opposite phase to the transmit leakage signal for RF cancellation. However, it has the following disadvantages: first, the insertion loss introduced is relatively large; second, since the RF cancellation signal is mainly generated by the vector modulator or phase shift attenuator, the signal quality is relatively low.

[0027] In order to solve the problems of the related art, an embodiment of the present application provides a radio frequency cancellation circuit.

[0028] The radio frequency cancellation circuit provided in the embodiment of the present application is described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0029] refer to Figure 1 , is a schematic diagram of the structure of a radio frequency cancellation circuit according to an embodiment of the present application. Figure 1As shown, the RF cancellation circuit includes a transmitting antenna 100, a receiving antenna 200, a transmitting channel, a receiving channel and a digital radio frequency memory (DRFM) 300. The digital radio frequency memory 300 is connected to the transmitting channel and the receiving channel respectively.

[0030] Specifically, the transmit channel is used to generate a transmit coupling signal corresponding to the transmit signal, and output or input the transmit coupling signal to the digital RF memory 300 from the transmit antenna 100; the digital RF memory 300 is used to generate an equal-amplitude anti-phase cancellation signal corresponding to the transmit coupling signal and the transmit leakage signal existing in the receive channel, so as to realize the RF cancellation of the receive channel.

[0031] Optional, such as Figure 1 As shown, the transmitting channel includes a first amplifying module 401, a bandpass filtering module 402 and a first coupling module 403; the receiving channel includes a second coupling module 501, a second amplifying module 502 and a third coupling module 503; the digital RF memory 300 is connected to the first coupling module and the second coupling module respectively. Among them, the second coupling module 501 is used to couple the receiving signal input through the receiving antenna 200 and the cancellation signal to obtain an echo signal that completes the RF cancellation.

[0032] That is to say, the coupled signal of the transmitted signal generates an equal amplitude anti-phase cancellation signal for the transmitted leakage signal and the near-end shielding signal through the digital RF memory 300, and is processed with the received signal through the coupler of the receiving channel (i.e., the second coupling module 501) to complete the RF cancellation. In this way, the channel isolation can be increased through coupling, and a part of the signal brought in by the transmission mixed in the received signal can be cancelled, so that the signal after eliminating the interference can be used for subsequent signal processing and data processing.

[0033] Furthermore, in some optional embodiments, the RF cancellation circuit also includes a cancellation database 600, a sampling module 700 and a processing control module 800. After the RF cancellation is completed, the echo signal is coupled out and sampled, and the result is transmitted to the processing control module 800. According to the cancellation result, the amplitude and phase of the output signal of the digital RF memory 300 are fine-tuned to improve the quality of the RF cancellation.

[0034] In some embodiments, the cancellation database 600 stores historical test data of the continuous wave radar. Specifically, the historical test data includes frequency characteristics of transmission leakage signals of transmission signals of different frequencies and amplitudes in the receiving channel within a historical time period. That is, the waveform data, amplitude information, phase information, etc. of the transmission signal of the radar obtained by the test at each transmission stage (for example, at different frequencies, different cycles or different working modes).

[0035] It should be noted that the cancellation database 600 is a dynamic database. Since the historical test data is the average value of the frequency characteristic data obtained by testing within a preset time period, the mean value of the amplitude information may increase or decrease, so the cancellation database 600 is dynamically managed. In this way, the waveform data, amplitude, and phase information emitted are basically stable, that is, each different mode corresponds to the frequency characteristic data. During the debugging process, the frequency characteristic data can be recorded and stored in the cancellation database 600 to provide a judgment basis for the comparison process of the subsequent processing control module 800.

[0036] It can be seen that the cancellation database 600 is mainly formed by the data collected in the early stage of the radar test. The test process is mainly aimed at the transmission leakage signals of the transmission signals of different frequencies and amplitudes in the receiving link. The collected data includes the amplitude and phase information of the transmission leakage signal, which is used to control the amplitude and phase of the transmission leakage cancellation signal during the cancellation process.

[0037] In some embodiments, the processing control module 800 is respectively connected to the sampling module 700, the cancellation database 600 and the digital RF memory 300, and is used to compare the echo signal with the historical test data stored in the cancellation database 600 after the echo signal is recoupled through the second amplification module 502 and the third coupling module 503 and sampled by the sampling module 700 to obtain a deviation signal.

[0038] As an optional embodiment, the processing control module 800 at least includes a comparator, and the processing control module 800 generates a deviation signal after the comparison process is completed by the comparator through external control. In this way, in the RF cancellation circuit, the transmission signal is coupled and stored in the digital RF memory 300, the reverse RF signal is coupled twice with the received signal through the receiving antenna 200, and then sampled once, and then the historical test data stored in the cancellation database 600 is compared with the real-time sampled signal currently collected. If the comparison result shows that there is a deviation, the deviation between the two signals is generated into a deviation amount, and then sent to the digital RF memory 300, so as to re-adjust multiple times according to the fine-tuning information to achieve a basic balance, that is, to achieve a satisfactory amplitude and phase adjustment range. In this way, a cyclic process of multiple adjustments is realized, that is, after a period of cancellation is completed, the balance may not be completely achieved, so the next period is re-sampled and compared with the cancellation database 600 again.

[0039] Furthermore, Figure 2 The specific structural diagram of the digital radio frequency memory 300 is shown. Figure 2 The internal circuit principle of the digital radio frequency memory 300 is described in detail.

[0040] like Figure 2As shown, the digital radio frequency memory 300 includes a down converter 301, an analog-to-digital converter ADC302, a memory 303, a signal conditioning circuit 304, a digital-to-analog converter DAC305, a filter 306, an up converter 307, an amplitude control module 308, a controller 309 and a programmable frequency synthesizer 310.

[0041] The controller 309 is respectively connected to the memory 303, the signal conditioning circuit 304 and the programmable frequency synthesizer 310; the control signal of the digital radio frequency memory 300 is generated by the cancellation database 600 through the processing control module 800; the controller 309 and the programmable frequency synthesizer 310 are used to cooperate to compare and eliminate the deviation signal with the signal stored in itself to perform signal conditioning and other steps before outputting.

[0042] Therefore, the digital RF memory 300 is specifically used to down-convert the input transmission coupling signal into an intermediate frequency signal through the down-converter 301, then perform sampling quantization encoding, and save the result in the memory 303, read the digital signal from the memory 303 under the control of the controller 309 and decode it to restore it to an intermediate frequency analog signal, perform phase adjustment through the signal conditioning circuit 304 according to the deviation signal, up-convert it into an RF signal through the up-converter 307, and perform amplitude adjustment through the amplitude control module 308 to obtain a cancellation signal.

[0043] It can be seen that the RF cancellation circuit in the embodiment of the present application adopts DRFM technology to realize the RF cancellation of the transmission leakage and near-end obstruction signal in the receiving link, and can complete the transmission leakage cancellation of the continuous wave radar to improve the transmission and reception isolation; compared with the traditional RF cancellation signal generation method by vector modulator or phase shift attenuator, it reduces the insertion loss of the system and improves the quality of the cancellation signal generation, thereby greatly improving the effect of RF cancellation, thereby improving the RF cancellation capability of the continuous wave radar to enhance the performance of the radar.

[0044] It should be noted that, for the convenience of description, the above device or system is described as various modules according to their functions. Of course, when implementing this application, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0045] The functional blocks shown in the structural block diagram described above can be implemented as hardware, software, firmware or a combination thereof. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present application are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link by a data signal carried in a carrier. "Machine-readable medium" may include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memories, erasable ROMs (EROMs), floppy disks, CD-ROMs, optical disks, hard disks, optical fiber media, radio frequency (RF) links, etc. The code segment can be downloaded via a computer network such as the Internet, an intranet, etc.

[0046] It should also be noted that the exemplary embodiments mentioned in this application describe some methods or systems based on a series of steps or devices. However, this application is not limited to the order of the above steps, that is, the steps can be performed in the order mentioned in the embodiment, or in a different order from the embodiment, or several steps can be performed simultaneously.

[0047] The above describes various aspects of the present application with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products according to the embodiments of the present application. It should be understood that each box in the flowchart and / or block diagram and the combination of each box in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine so that these instructions executed by the processor of the computer or other programmable data processing device enable the implementation of the functions / actions specified in one or more boxes of the flowchart and / or block diagram. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field programmable logic circuit. It can also be understood that each box in the block diagram and / or flowchart and the combination of boxes in the block diagram and / or flowchart can also be implemented by dedicated hardware that performs a specified function or action, or can be implemented by a combination of dedicated hardware and computer instructions.

[0048] The above is only a specific implementation of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, modules and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in this application, and these modifications or replacements should be included in the protection scope of this application.

Claims

1. A radio frequency cancellation circuit, characterized in that: include: A transmitting antenna, a receiving antenna, a transmitting channel, a receiving channel, a digital radio frequency memory, a cancellation database, a sampling module and a processing control module, wherein the digital radio frequency memory is connected to the transmitting channel and the receiving channel respectively, the processing control module is connected to the sampling module, the cancellation database and the digital radio frequency memory respectively, and the cancellation database stores historical test data of the continuous wave radar; The transmitting channel is used to generate a transmitting coupled signal corresponding to the transmitting signal, and output or input the transmitting coupled signal from the transmitting antenna to the digital radio frequency memory; The transmitting channel includes a first amplifying module, a bandpass filtering module and a first coupling module, the receiving channel includes a second coupling module, a second amplifying module and a third coupling module, and the digital radio frequency memory is connected to the first coupling module and the second coupling module respectively; The second coupling module is used to couple the receiving signal input through the receiving antenna and the cancellation signal to obtain an echo signal that completes the radio frequency cancellation; The digital radio frequency memory is used to generate equal-amplitude anti-phase cancellation signals corresponding to the transmit coupling signal and the transmit leakage signal existing in the receive channel, so as to realize radio frequency cancellation of the receive channel; The processing control module is used for comparing the real-time sampling signal with the historical test data stored in the cancellation database after the echo signal is re-coupled by the second amplification module and the third coupling module and sampled by the sampling module to obtain the real-time sampling signal, and when the comparison result shows that there is a deviation between the real-time sampling signal and the historical test data, generating a deviation signal according to the deviation between the real-time sampling signal and the historical test data, and sending the deviation signal to the digital radio frequency memory, so that the digital radio frequency memory is adjusted according to the deviation signal to obtain the cancellation signal, and cyclically executing to realize multiple adjustments until the preset amplitude and phase adjustment range is met.

2. The radio frequency cancellation circuit according to claim 1, characterized in that: The historical test data includes frequency characteristics of transmission leakage signals of transmission signals of different frequencies and amplitudes in the receiving channel within a historical time period.

3. The radio frequency cancellation circuit according to claim 1, characterized in that: The cancellation database is a dynamic database.

4. The radio frequency cancellation circuit according to claim 1, characterized in that: The digital radio frequency memory comprises a down converter, an analog-to-digital converter ADC, a memory, a signal conditioning circuit, a digital-to-analog converter DAC, a filter, an up converter, an amplitude control module, a controller and a programmable frequency synthesizer, and the controller is respectively connected to the memory, the signal conditioning circuit and the programmable frequency synthesizer.

5. The radio frequency cancellation circuit according to claim 4, characterized in that: The digital radio frequency memory is specifically used to down-convert the input transmission coupling signal into an intermediate frequency signal through a down-converter, then perform sampling quantization encoding, and store the result in the memory; read the digital signal from the memory under the control of the controller and decode it to restore it into an intermediate frequency analog signal; perform phase adjustment through a signal conditioning circuit according to a deviation signal, up-convert the signal into an radio frequency signal through an up-converter, and perform amplitude adjustment through an amplitude control module to obtain a cancellation signal.

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