Carrier elimination system and method based on automatic tuning

Abstract

The invention provides a carrier elimination system and method based on automatic tuning. The system comprises an orthogonal phase splitter, an adder, an output circuit connected with the adder, a first circuit and a second circuit, wherein the first circuit and the second circuit are arranged between the orthogonal phase splitter and the adder; wherein a carrier signal of a radio frequency end to be processed is input into a coupling carrier input end of the orthogonal phase splitter and forms two paths of signals after passing through the orthogonal phase splitter; two paths of signals are respectively input into the first circuit and the second circuit; output signals of the first circuit and the second circuit are combined through an adder, and a combined signal is output to the output circuit; performing subtraction and polling processing on the combined signal and the initial signal through an output circuit and a preset polling algorithm to obtain a modulation signal after the carrier signal is eliminated; wherein the initial signal comprises the carrier signal and the corresponding modulation signal. According to the invention, the elimination of the carrier wave can be realized through the passive device.

Description

Technical Field

[0001] The present invention relates to the technical field of signal transmission, and more specifically, to a carrier elimination system and method based on automatic tuning. Background Art

[0002] RFID (Radio Frequency Identification) is a contactless automatic identification technology that mainly uses magnetic fields or electromagnetic fields as media to transfer energy and information, completing information interaction between the host and the object being measured.

[0003] At present, in RFID systems, in order to provide energy to the tag chip, the reader needs to continuously transmit a large unmodulated continuous carrier signal. The carrier signal leaks into the receiver front end through a circulator or directional coupler. Due to the return mechanism of the tag backscatter, the receiving and sending signals are determined to have the same carrier frequency. Therefore, it is impossible to filter out the leaked carrier signal through the RF bandpass filter at the receiving front end, causing desensitization and blocking at the receiver front end, affecting the dynamics of the receiving link. Summary of the invention

[0004] In view of the above problems, the present invention provides a carrier elimination system and method based on automatic tuning to solve the problem that the leaked carrier signal cannot be filtered out, causing desensitization and blocking of the receiver front end, affecting the dynamics of the receiving link.

[0005] The carrier elimination system based on automatic tuning provided by the present invention comprises an orthogonal phase splitter, an adder, an output circuit connected to the adder, and a first circuit and a second circuit arranged between the orthogonal phase splitter and the adder; wherein, The carrier signal of the radio frequency end to be processed is input into the coupled carrier input end of the orthogonal phase splitter, and forms two signals after passing through the orthogonal phase splitter; The two signals are respectively input into the first circuit and the second circuit; The output signals of the first circuit and the second circuit are combined by the adder, and the combined signal is output to the output circuit; The combined signal and the initial signal are subtracted and processed in a round-robin manner through the output circuit and a preset round-robin algorithm to obtain a modulated signal after the carrier signal is eliminated; wherein the initial signal includes the carrier signal and the corresponding modulated signal.

[0006] In addition, an optional technical solution is that the first circuit includes a first balun converter, a first switch switch, a second balun converter and a first digitally controlled attenuator connected in sequence; wherein, The first balun converter is used to convert one of the two signals into a balanced and unbalanced signal; The first switch is used to perform phase inversion on the signal after balanced and unbalanced conversion; The second balun converter is used to convert the signal after the phase flip into balanced and unbalanced signal; The first digitally controlled attenuator is used to adjust the amplitude and phase of the signal output by the second balun converter.

[0007] In addition, an optional technical solution is that the second circuit includes a third balun converter, a second switch switch, a fourth balun converter and a second digitally controlled attenuator connected in sequence; wherein, The third balun converter is used for performing balanced and unbalanced conversion on the other signal of the two signals; The second switch is used to perform phase inversion on the signal after balanced and unbalanced conversion; The fourth balun converter is used to convert the signal after the phase flip into a balanced and unbalanced signal; The second digitally controlled attenuator is used to adjust the amplitude and phase of the signal output by the fourth balun converter.

[0008] In addition, an optional technical solution is that the phase difference between the two signals is 90 degrees.

[0009] In addition, an optional technical solution is that the output circuit includes a combiner and an amplifier connected in sequence, and the initial signal and the combined signal are both input into the combiner; The combiner is used to perform subtraction processing on the combined signal and the initial signal; The amplifier is used to amplify and output the modulated signal output by the combiner.

[0010] In addition, an optional technical solution is to further include a coupler connected to the amplifier and a detector and an MCU connected to the coupler in turn; wherein, The MCU is used to control the states of the first circuit and the second circuit according to the voltage value of the detector.

[0011] In addition, an optional technical solution is that the state of the first circuit includes the switch state of the first switch switch and the attenuation value of the first digitally controlled attenuator; The state of the second circuit includes the switching state of the second switch and the attenuation value of the second digitally controlled attenuator.

[0012] In addition, an optional technical solution is that the preset patrol algorithm includes: The MCU controls the first switch switch and the second switch switch to flip the phase of the signal in the corresponding circuit respectively, so that the phase of the carrier signal is opposite to that of the initial signal and cancels each other out; at the same time, the voltage value of the detector is monitored, and when the voltage value is the minimum value, it is determined that the phase satisfies the opposite relationship, and the switching states of the first switch switch and the second switch switch are locked.

[0013] In addition, an optional technical solution is that the preset patrol algorithm further includes: The voltage value of the detector is monitored by the MCU, and the attenuation values ​​of the first digitally controlled attenuator and the second digitally controlled attenuator are adjusted. When the voltage value is the minimum value, the attenuation values ​​of the first digitally controlled attenuator and the second digitally controlled attenuator are locked and fixedly set.

[0014] On the other hand, the present invention also provides a carrier elimination method based on automatic tuning, which eliminates the target carrier signal by using the above-mentioned carrier elimination system based on automatic tuning.

[0015] By utilizing the above-mentioned carrier elimination system and method based on automatic tuning, passive components and a preset patrol algorithm are adopted to realize the function of automatic tuning to cancel the carrier signal, and obtain the modulated signal after eliminating the carrier signal, which can avoid the introduction of additional noise to affect the system and is applicable to RFID systems of various frequency bands. In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] By referring to the following description in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more clear and easy to understand. In the accompanying drawings: Figure 1 A schematic diagram of a carrier elimination system based on automatic tuning according to an embodiment of the present invention; Figure 2 4 is a flowchart of a patrol algorithm according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0018] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that the term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0019] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the field to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0020] At present, one solution to overcome carrier signal interference is to set up two RF paths at the receiving front end: a linear RF path and a nonlinear limiting RF path. The signals on the two paths are subtracted to retain the useful tag signal and cancel the leakage signal. However, the disadvantage of this solution is that it is necessary to detect the amplitude of the input and output signals, and then adjust the gain of the nonlinear limiting path through a digital algorithm controlled by an FPGA so that its output signal and the linear path carrier leakage signal have the same amplitude and phase, and subtract them at the output end to cancel the carrier leakage signal. It can be seen that the cancellation effect of this method is affected by the phase and amplitude matching degree of the two paths. Not only is the control algorithm complex, but it also introduces additional redundant noise.

[0021] The other method is to eliminate the negative feedback loop through carrier leakage. The carrier signal coupled from the front end is passed through the amplifier and phase shifter to generate a reverse signal to cancel the carrier. However, most of the solutions use active devices, which not only introduces excess noise, but also makes it difficult for the phase shifter to achieve a wide bandwidth and a narrow frequency coverage, which cannot meet the requirements of versatility. In addition, the adjustable amplifier and adjustable phase shifter need to be adjusted at the same time, which is relatively complicated in terms of control.

[0022] To this end, the present invention provides a carrier elimination system and method based on automatic tuning. To describe the carrier elimination system and method based on automatic tuning of the present invention in detail, specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0023] Figure 1 The principle of the carrier elimination system based on automatic tuning according to an embodiment of the present invention is shown. Figure 2The figure shows a schematic flow of a patrol algorithm according to an embodiment of the present invention.

[0024] like Figure 1 and Figure 2 As shown together, the carrier elimination system based on automatic tuning of the embodiment of the present invention includes an orthogonal phase splitter, an adder, an output circuit connected to the adder, and a first circuit and a second circuit arranged between the orthogonal phase splitter and the adder; wherein, the carrier signal of the RF end to be processed is input into the coupled carrier input end of the orthogonal phase splitter, and two signals are formed after passing through the orthogonal phase splitter, and then the two signals are respectively input into the first circuit and the second circuit for processing respectively, and the output signal processed by the first circuit and the second circuit is combined through the adder, and the combined signal is output to the output circuit, and the combined signal and the initial signal are subtracted and processed in a patrol process through the output circuit and a preset patrol algorithm, and finally a modulated signal after the carrier signal is eliminated is obtained; wherein, the initial signal includes a carrier signal and a corresponding modulation signal, and after being processed by the output circuit, the carrier signal can be effectively eliminated, thereby obtaining a high-quality modulation signal.

[0025] Among them, the RFID reader will emit a carrier signal, which is transmitted through the antenna to provide energy to the tag. After the tag obtains the energy, it will load its own modulated signal and reflect it back to the RFID reader. The radio frequency signal output by the RFID reader is coupled to the coupled carrier input terminal through the coupler on the right, and then passes through a 90-degree bridge as an orthogonal phase splitter to generate two signals with a limit difference of 90 degrees, which are processed separately through the first circuit and the second circuit respectively.

[0026] Specifically, the first circuit further includes a first balun converter, a first switch, a second balun converter and a first digitally controlled attenuator connected in sequence; wherein, after being processed by the orthogonal phase splitter, the circuit is first converted between balanced and unbalanced through the first balun converter; then the phase of the signal after the balanced and unbalanced conversion is flipped through the first switch, and then the signal after the phase flip is converted between balanced and unbalanced through the second balun converter, and finally the amplitude and phase of the signal output by the second balun converter are regulated through the first digitally controlled attenuator.

[0027] Similarly, the second circuit includes a third balun converter, a second switch, a fourth balun converter and a second digitally controlled attenuator connected in sequence; wherein, the other circuit after being processed by the orthogonal phase splitter is first converted between balanced and unbalanced through the third balun converter; then the phase of the signal after the balanced and unbalanced conversion is flipped through the second switch, and then the signal after the phase flip is converted between balanced and unbalanced through the fourth balun converter, and finally the amplitude and phase of the signal output by the fourth balun converter are regulated through the second digitally controlled attenuator.

[0028] Specifically, the phase difference between the two signals formed after passing through the orthogonal phase splitter is 90 degrees. After the two signals are processed by the first circuit and the second circuit, whether the final output signal is forward or reverse can be determined by a subsequent patrol algorithm, thereby finding the optimal combination state to effectively eliminate the carrier signal.

[0029] In a specific embodiment of the present invention, the output circuit further includes a combiner and an amplifier connected in sequence, the initial signal and the combined signal are input into the combiner, the combined signal and the initial signal are subtracted by the combiner, so that only the modulated signal is retained, and the modulated signal output by the combiner is amplified and output by the amplifier. However, in actual application, the carrier signal cannot be completely offset. For this reason, the subsequent amplifier, coupler, detector and MCU (Microcontroller Unit) can be used to perform patrol algorithm processing to fine-tune the amplitude and phase of the signal, so as to weaken the carrier signal as much as possible and find the optimal solution.

[0030] Among them, the carrier elimination system based on automatic tuning of the embodiment of the present invention also includes a coupler connected to the amplifier and a detector and an MCU connected to the coupler in turn; wherein the MCU can control the states of the first circuit and the second circuit according to the voltage value of the detector, the state of the first circuit includes the switching state of the first switch switch and the attenuation value of the first digitally controlled attenuator; the state of the second circuit includes the switching state of the second switch switch and the attenuation value of the second digitally controlled attenuator.

[0031] Therefore, the preset patrol algorithm in the process of determining the state of the first circuit and the second circuit includes: controlling the first switch switch and the second switch switch through the MCU to flip the phase of the signal in the corresponding circuit respectively, so that the phase of the carrier signal is opposite to the initial signal and cancels it; at the same time, monitoring the voltage value of the detector, when the voltage value is the minimum value, judging that the phase satisfies the opposite relationship, and locking the switch state of the first switch switch and the second switch switch. And, monitoring the voltage value of the detector through the MCU, and adjusting the attenuation value of the first digitally controlled attenuator and the second digitally controlled attenuator, when the voltage value is the minimum value, locking the attenuation value of the first digitally controlled attenuator and the second digitally controlled attenuator and fixing the setting.

[0032] As a specific example, when the input signal at the coupled carrier input end is Acosx, after being processed by the 90° quadrature phase splitter, the two signals are Acosx and Acos(x-90°)=sinx, where A represents the coefficient and x represents the independent variable. Then, the two signals are respectively distributed through the 180° balanced-to-unbalanced balun converter to generate two outputs with equal amplitude but 180 degrees phase difference, and then the two signal phases are flipped through the switch switch, and finally the signal amplitude and phase are adjusted through the digitally controlled attenuator.

[0033] Specifically, after the orthogonal phase splitter processes the two signals Acosx and Asinx, after the balun converter, the output signals corresponding to the signal Acosx are Acosx and Acos(x-180)=-cosx; the output signals corresponding to the signal Asinx are Asinx and Asin(x-180)=-sinx; among them, after one signal is combined and converted by the switch switch and the digitally controlled attenuator, the output signal is U1cosx or -U1cosx; after the other signal is combined and converted by the switch switch and the digitally controlled attenuator, the output signal is U2sinx or -U2sinx, where U1 and U2 respectively represent the amplitudes of the corresponding signals; therefore, the patrol algorithm can be used to determine whether the specific output signal is forward or reverse.

[0034] Then, the combined signal is transformed by the trigonometric function, that is, the combined signal is: ,in, , θ represents the phase angle of the combined signal.

[0035] Then, the combined signal and the initial signal received at the reverse signal input end are subtracted through the combiner, i.e., the 90° bridge, and only the modulation signal is retained, thereby eliminating the carrier signal. At this time, the obtained modulation signal is: , k represents the independent variable of the modulated signal, bcosx is the signal returned by the antenna coupling, which is input into the combiner through the return signal input terminal, b represents the amplitude of the signal, and R represents the amplitude of the combined signal. It can be seen that in actual situations, the carrier signal cannot be completely offset, but can only be weakened as much as possible. Therefore, the power amplifier, coupler, and detector in the output circuit can be further coordinated with the MCU for patrol scheduling, so as to fine-tune the amplitude and phase of the signal in the circuit and determine the best combination state.

[0036] Among them, the MCU first detects the voltage of the output power of the un-cancelled carrier through the detector as the initial calibration value V1, that is, the voltage when there is no return input signal is set as the initial calibration value V1, and then the return input signal is loaded, and the MCU controls the switch switch to flip the signal phase in the corresponding circuit, so that the coupled carrier signal and the returned input signal are in opposite phase and cancel each other out, that is, The patrol algorithm traverses the voltage values ​​detected in various states and compares them with the initial value V1 to find the minimum value. To achieve the best state, for example, monitor the voltage value of the detector. When the voltage value is the minimum, it can be determined that the phase satisfies the opposite relationship. The switching state of the two switch switches at this time is fixed, and this value is used as the calibration value V2; then adjust the corresponding digitally controlled attenuator, and monitor the voltage value of the detector for fine-tuning. Through the patrol algorithm, the voltage value V3 under various attenuation states is traversed, and the best digitally controlled attenuation value is found and fixed, that is, the amplitude R=b, to achieve complete carrier cancellation.

[0037] Corresponding to the above-mentioned carrier elimination system based on automatic tuning, the present invention also provides a carrier elimination method based on automatic tuning, which eliminates the target carrier signal by using the above-mentioned carrier elimination system based on automatic tuning.

[0038] It should be noted that the embodiments of the above-mentioned carrier elimination method based on automatic tuning can refer to the description in the embodiment of the carrier elimination system based on automatic tuning, which will not be described in detail here.

[0039] According to the carrier elimination system and method based on automatic tuning of the present invention, passive components and preset patrol algorithms are used. There is no need to worry about the use of phase shifters causing additional noise. The function of automatic tuning to offset the carrier signal can be realized, and the modulated signal after the carrier signal is eliminated can be obtained, thereby avoiding the influence of additional noise on the system. The control algorithm is simple and can be applied to RFID systems in various frequency bands. As described above with reference to the accompanying drawings, the carrier elimination system and method based on automatic tuning according to the present invention are described by way of example. However, it should be understood by those skilled in the art that various improvements can be made to the carrier elimination system and method based on automatic tuning proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A carrier elimination system based on automatic tuning, characterized in that: The invention comprises an orthogonal phase splitter, an adder, an output circuit connected to the adder, and a first circuit and a second circuit arranged between the orthogonal phase splitter and the adder; wherein, The carrier signal of the radio frequency end to be processed is input into the coupled carrier input end of the orthogonal phase splitter, and forms two signals after passing through the orthogonal phase splitter; The two signals are respectively input into the first circuit and the second circuit; The output signals of the first circuit and the second circuit are combined by the adder, and the combined signal is output to the output circuit; The combined signal and the initial signal are subtracted and processed in a round-robin manner through the output circuit and a preset round-robin algorithm to obtain a modulated signal after the carrier signal is eliminated; wherein the initial signal includes the carrier signal and the corresponding modulated signal.

2. The carrier elimination system based on automatic tuning according to claim 1, characterized in that: The first circuit includes a first balun converter, a first switch switch, a second balun converter and a first digitally controlled attenuator connected in sequence; wherein, The first balun converter is used to convert one of the two signals into a balanced and unbalanced signal; The first switch is used to perform phase inversion on the signal after balanced and unbalanced conversion; The second balun converter is used to convert the signal after the phase flip into balanced and unbalanced signal; The first digitally controlled attenuator is used to adjust the amplitude and phase of the signal output by the second balun converter.

3. The carrier elimination system based on automatic tuning according to claim 2, characterized in that: The second circuit includes a third balun converter, a second switch switch, a fourth balun converter and a second digitally controlled attenuator connected in sequence; wherein, The third balun converter is used for performing balanced and unbalanced conversion on the other signal of the two signals; The second switch is used to perform phase inversion on the signal after balanced and unbalanced conversion; The fourth balun converter is used to convert the signal after the phase flip into a balanced and unbalanced signal; The second digitally controlled attenuator is used to adjust the amplitude and phase of the signal output by the fourth balun converter.

4. The carrier elimination system based on automatic tuning according to claim 1, characterized in that: The phase difference between the two signals is 90 degrees.

5. The carrier elimination system based on automatic tuning according to claim 3, characterized in that: The output circuit comprises a combiner and an amplifier connected in sequence, and the initial signal and the combined signal are both input into the combiner; The combiner is used to perform subtraction processing on the combined signal and the initial signal; The amplifier is used to amplify and output the modulated signal output by the combiner.

6. The carrier elimination system based on automatic tuning according to claim 5, characterized in that: It also includes a coupler connected to the amplifier and a detector and an MCU connected to the coupler in turn; wherein, The MCU is used to control the states of the first circuit and the second circuit according to the voltage value of the detector.

7. The carrier elimination system based on automatic tuning according to claim 6, characterized in that: The state of the first circuit includes the switch state of the first switch switch and the attenuation value of the first digitally controlled attenuator; The state of the second circuit includes the switching state of the second switch and the attenuation value of the second digitally controlled attenuator.

8. The carrier elimination system based on automatic tuning according to claim 7, characterized in that: The preset patrol algorithm includes: The MCU controls the first switch switch and the second switch switch to flip the phase of the signal in the corresponding circuit respectively, so that the phase of the carrier signal is opposite to that of the initial signal and cancels each other out; at the same time, the voltage value of the detector is monitored, and when the voltage value is the minimum value, it is determined that the phase satisfies the opposite relationship, and the switching states of the first switch switch and the second switch switch are locked.

9. The carrier elimination system based on automatic tuning according to claim 8, characterized in that: The preset patrol algorithm also includes: The voltage value of the detector is monitored by the MCU, and the attenuation values ​​of the first digitally controlled attenuator and the second digitally controlled attenuator are adjusted. When the voltage value is the minimum value, the attenuation values ​​of the first digitally controlled attenuator and the second digitally controlled attenuator are locked and fixedly set.

10. A carrier elimination method based on automatic tuning, characterized in that: The target carrier signal is eliminated using the carrier elimination system based on automatic tuning as described in any one of claims 1 to 9.

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