Method and system for suppressing image frequency of receiver
By using frequency tuning and FFT operations in the receiver's single-conversion scheme, image frequency signals are identified and eliminated, solving the problem of image interference in existing technologies and simplifying receiver design while improving sensitivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-03-31
AI Technical Summary
Existing broadband receivers struggle to effectively suppress image interference signals in single-conversion schemes, resulting in complex receiver designs and low sensitivity.
By using a receiver single-conversion scheme, frequency tuning equations and FFT operations are employed to identify and eliminate image frequency signals, including frequency mapping of the RF input signal and fine-tuning of the local oscillator frequency, thereby achieving the identification and elimination of image frequencies.
It simplifies the design of the receiver's RF downconversion circuit, improves the receiver sensitivity, and reduces the residual response caused by multiple frequency conversions.
Smart Images
Figure CN121770542A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of radio frequency microwave communication technology, specifically a method and system for suppressing receiver image frequencies. Background Technology
[0002] Current broadband receivers generally use a superheterodyne method to convert broadband radio frequency signals to fixed intermediate frequency signals for analysis and processing. To suppress image frequencies, double or triple conversion is usually used for reception. This is a hardware design feature that ensures that image frequencies are filtered out before entering the mixer. However, to simplify the design, some receivers only use a single conversion scheme, which inevitably introduces image interference. Summary of the Invention
[0003] To address the shortcomings mentioned in the background section, the present invention aims to provide a method and system for suppressing receiver image frequencies, which can effectively identify and eliminate image interference signals under the premise of receiver single-conversion scheme design.
[0004] Firstly, the objective of this invention can be achieved through the following technical solution: a method for suppressing receiver image frequencies, the method comprising the following steps: The first digital intermediate frequency signal is received, wherein the first digital intermediate frequency signal is obtained by mixing the radio frequency input signal and the local oscillator signal by a mixer and then performing analog-to-digital conversion; the first digital intermediate frequency signal corresponds to the first local oscillator frequency; The first digital intermediate frequency signal is processed and the first frequency mapping result is obtained by FFT operation. The frequency mapping is the mapping relationship between the radio frequency, local oscillator frequency and intermediate frequency defined by the frequency tuning equation. The first local oscillator frequency is finely adjusted by a preset offset to obtain the second local oscillator frequency. The corresponding second digital intermediate frequency signal is obtained based on the second local oscillator frequency. The second digital intermediate frequency signal is processed and the second frequency mapping result is obtained through FFT operation. The first frequency mapping result is compared with the second frequency mapping result to identify and eliminate mirror frequency signals.
[0005] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: the radio frequency input signal passes through a radio frequency attenuator, a first amplifier, and a low-pass filter before entering the I port of the mixer, wherein the frequency range of the radio frequency input signal is 9kHz to 6GHz, and the cutoff frequency of the low-pass filter is 6GHz.
[0006] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: after entering the R port of the mixer, the radio frequency signal entering the mixer is mixed with the first local oscillator signal to output an IF intermediate frequency signal, the IF intermediate frequency signal passes through a bandpass filter and a second amplifier in sequence to obtain an intermediate frequency signal, and the intermediate frequency signal is entered into an analog-to-digital converter to obtain a first digital intermediate frequency signal.
[0007] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: the frequency of the IF intermediate frequency signal is 307.2MHz, the frequency range of the first local oscillator signal is 300MHz~6.4GHz; the center frequency of the bandpass filter is 307.2MHz, and the bandwidth is 100MHz; the analog-to-digital converter is a high-speed parallel output ADC, the sampling clock is not less than 250MHz, and the output valid data is not less than 14 bits.
[0008] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: the frequency tuning equation is as follows: = 307.2MHz (1) in, The intermediate frequency, The local oscillator frequency, This refers to the radio frequency.
[0009] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: the calculation process of processing the first digital intermediate frequency signal, comprising: For the same local oscillator frequency exist Image frequency: (2) The same frequency can be obtained by the following tuning equation. Signal: = 307.2MHz (3).
[0010] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: the calculation process of processing the second digital intermediate frequency signal, comprising: = 312.2MHz (4) = 302.2MHz (5) Through the tuning equations of equations (1) and (4), the same radio frequency signal is obtained through the frequency mapping relationship. The signal frequencies obtained from the two signal acquisition and analysis were the same. Through the tuning equations of equations (3) and (5), the same Frequency mapping relationship The frequency difference between the two signal acquisition and analysis results is 10MHz. Signals with the same frequency in two calculations are retained, while signals with different frequencies in two calculations are treated as mirror frequency signals and discarded.
[0011] Secondly, in order to achieve the above objectives, the present invention discloses a system for suppressing receiver image frequencies, comprising: A primary signal processing module is used to receive a first digital intermediate frequency (IF) signal, wherein the first IF signal is obtained by mixing the radio frequency input signal and the local oscillator signal by a mixer and then performing analog-to-digital conversion; the first IF signal corresponds to the first local oscillator frequency. The first mapping module is used to process the first digital intermediate frequency signal and obtain the first frequency mapping result through FFT operation. The frequency mapping is the mapping relationship between the radio frequency, local oscillator frequency and intermediate frequency defined based on the frequency tuning equation. The secondary processing mapping module is used to fine-tune the first local oscillator frequency by a preset offset to obtain the second local oscillator frequency, obtain the corresponding second digital intermediate frequency signal based on the second local oscillator frequency, perform signal processing on the second digital intermediate frequency signal, and obtain the second frequency mapping result through FFT operation. The identification and rejection module is used to compare the first frequency mapping result with the second frequency mapping result, identify and reject the mirror frequency signal.
[0012] In another aspect of the present invention, in order to achieve the above-mentioned objective, a terminal device is disclosed, including a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The memory stores the computer program capable of running on the processor, and when the processor loads and executes the computer program, it employs a method for suppressing receiver image frequencies as described above.
[0013] In another aspect of the present invention, in order to achieve the above-mentioned objective, a computer-readable storage medium is disclosed, wherein a computer program is stored in the computer program, and when the computer program is loaded and executed by a processor, a method for suppressing receiver image frequencies as described above is employed.
[0014] The beneficial effects of this invention are: This invention designs a receiver primary frequency conversion scheme by analyzing and processing the RF input signal a second time through a slightly modified local oscillator signal. This effectively identifies and eliminates image interference signals, simplifies the design of the receiver's RF down-conversion circuit, and effectively improves receiving sensitivity while reducing residual response caused by multiple frequency conversions. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a schematic diagram of the universal receiver secondary downconversion scheme of the present invention; Figure 3 This is a schematic diagram of the receiver's single downconversion scheme according to the present invention; Figure 4 This is after the first FFT operation of the present invention and Schematic diagram of analysis results; Figure 5 This invention increases the local oscillator LO1 frequency by 5MHz and performs FFT calculations. Schematic diagram of analysis results; Figure 6 This invention increases the local oscillator LO1 frequency by 5MHz and performs FFT calculations. Schematic diagram of analysis results; Figure 7 This is a schematic diagram of the system structure of the present invention. Detailed Implementation
[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0017] Example 1: like Figure 1 As shown, a method for suppressing receiver image frequencies includes the following steps: S101: Receive the first digital intermediate frequency signal, wherein the first digital intermediate frequency signal is obtained by mixing the radio frequency input signal and the local oscillator signal by a mixer and then performing analog-to-digital conversion; the first digital intermediate frequency signal corresponds to the first local oscillator frequency; The radio frequency input signal passes through the radio frequency attenuator, the first amplifier, and the low-pass filter before entering the R port of the mixer. The frequency range of the radio frequency input signal is 9kHz to 6GHz, and the cutoff frequency of the low-pass filter is 6GHz.
[0018] After entering the R port of the mixer, the RF signal and the first local oscillator signal are mixed to output the IF intermediate frequency signal. The IF intermediate frequency signal passes through the bandpass filter and the second amplifier in sequence to obtain the intermediate frequency signal. The intermediate frequency signal is then sent to the analog-to-digital converter to obtain the first digital intermediate frequency signal.
[0019] The IF intermediate frequency signal has a frequency of 307.2MHz, and the first local oscillator signal has a frequency range of 300MHz to 6.4GHz; the center frequency of the bandpass filter is 307.2MHz, and the bandwidth is 100MHz; the analog-to-digital converter is a high-speed parallel output ADC with a sampling clock of not less than 250MHz and an output effective data of not less than 14 bits.
[0020] S102: The first digital intermediate frequency signal is processed and the first frequency mapping result is obtained through FFT operation. The frequency mapping is the mapping relationship between the radio frequency, local oscillator frequency and intermediate frequency defined based on the frequency tuning equation. The frequency tuning equation is as follows: = 307.2MHz (1) in, The intermediate frequency, The local oscillator frequency, This refers to the radio frequency.
[0021] The calculation process for signal processing of the first digital intermediate frequency signal includes: For the same local oscillator frequency exist Image frequency: (2) The same frequency can be obtained by the following tuning equation. Signal: = 307.2MHz (3).
[0022] S103: Fine-tune the first local oscillator frequency by a preset offset to obtain the second local oscillator frequency, obtain the corresponding second digital intermediate frequency signal based on the second local oscillator frequency, perform signal processing on the second digital intermediate frequency signal, and obtain the second frequency mapping result through FFT operation; The calculation process for signal processing of the second digital intermediate frequency signal includes: = 312.2MHz (4) = 302.2MHz (5) Through the tuning equations of equations (1) and (4), the same Signal frequency mapping relationship The signal frequencies obtained from the two signal acquisition and analysis were the same, as shown in the attached figure. Figure 5 As shown; and through the tuning equations of equations (3) and (5), the same Frequency mapping relationship The signal frequencies obtained from the two signal acquisitions and analyses differed by 10MHz, as shown in the attached figure. Figure 6 As shown; the final result is to retain signals with the same frequency in the two calculations and to remove signals with different frequencies in the two calculations; therefore, increasing the frequency of the local oscillator 1 by 5MHz for secondary signal acquisition and analysis can effectively identify the image frequency signal and ensure the frequency accuracy of the measured signal.
[0023] S104: Compare the first frequency mapping result with the second frequency mapping result, identify and remove the mirror frequency signal.
[0024] Specifically, the present invention will be further illustrated below through embodiments: The radio frequency input frequency range Including but not limited to 9kHz~6GHz, intermediate frequency Including but not limited to 307.2MHz, local oscillator frequency Fine-tuning, including but not limited to 5MHz, can be achieved in a single-conversion receiver by using the method provided by this invention to perform secondary analysis of the radio frequency input signal, thereby effectively identifying the image frequency signal and ensuring the frequency accuracy of the measured signal.
[0025] Example 2: To achieve the above objective, such as Figure 7 As shown, based on Embodiment 1, this invention discloses a system for suppressing receiver image frequencies, comprising: The primary signal processing module 11 is used to receive the first digital intermediate frequency signal, wherein the first digital intermediate frequency signal is obtained by mixing the radio frequency input signal and the local oscillator signal by a mixer and then performing analog-to-digital conversion; the first digital intermediate frequency signal corresponds to the first local oscillator frequency; The first mapping module 12 is used to process the first digital intermediate frequency signal and obtain the first frequency mapping result through FFT operation. The frequency mapping is the mapping relationship between the radio frequency, local oscillator frequency and intermediate frequency defined by the frequency tuning equation. The secondary processing mapping module 13 is used to fine-tune the first local oscillator frequency by a preset offset to obtain the second local oscillator frequency, obtain the corresponding second digital intermediate frequency signal based on the second local oscillator frequency, perform signal processing on the second digital intermediate frequency signal, and obtain the second frequency mapping result through FFT operation. The identification and rejection module 14 is used to compare the first frequency mapping result with the second frequency mapping result, identify and reject the mirror frequency signal.
[0026] Based on the same inventive concept, this invention also provides a computer device, comprising: one or more processors, and a memory for storing one or more computer programs; the programs include program instructions, and the processor executes the program instructions stored in the memory. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, used to implement one or more instructions, specifically for loading and executing one or more instructions stored in a computer storage medium to implement the above-described method.
[0027] It should be further explained that, based on the same inventive concept, the present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, performs the above-described method. This storage medium can be any combination of one or more computer-readable media. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.
[0028] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0029] The foregoing has shown and described the basic principles, main features, and advantages of this disclosure. Those skilled in the art should understand that this disclosure is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this disclosure. Various changes and modifications can be made to this disclosure without departing from its spirit and scope, and all such changes and modifications fall within the scope of this disclosure as claimed.
Claims
1. A method for suppressing receiver image frequencies, characterized in that, The method includes the following steps: The first digital intermediate frequency signal is received, wherein the first digital intermediate frequency signal is obtained by mixing the radio frequency input signal and the local oscillator signal by a mixer and then performing analog-to-digital conversion; the first digital intermediate frequency signal corresponds to the first local oscillator frequency; The first digital intermediate frequency signal is processed and the first frequency mapping result is obtained by FFT operation. The frequency mapping is the mapping relationship between the radio frequency, local oscillator frequency and intermediate frequency defined by the frequency tuning equation. The first local oscillator frequency is finely adjusted by a preset offset to obtain the second local oscillator frequency. The corresponding second digital intermediate frequency signal is obtained based on the second local oscillator frequency. The second digital intermediate frequency signal is processed and the second frequency mapping result is obtained through FFT operation. The first frequency mapping result is compared with the second frequency mapping result to identify and eliminate mirror frequency signals.
2. The method for suppressing receiver image frequencies according to claim 1, characterized in that, The radio frequency input signal passes through a radio frequency attenuator, a first amplifier, and a low-pass filter before entering the R port of the mixer. The frequency range of the radio frequency input signal is 9kHz to 6GHz, and the cutoff frequency of the low-pass filter is 6GHz.
3. The method for suppressing receiver image frequencies according to claim 2, characterized in that, After entering the R port of the mixer, the radio frequency signal entering the mixer is mixed with the first local oscillator signal to output the IF intermediate frequency signal. The IF intermediate frequency signal passes through the bandpass filter and the second amplifier in sequence to obtain the intermediate frequency signal. The intermediate frequency signal is then entered into the analog-to-digital converter to obtain the first digital intermediate frequency signal.
4. The method for suppressing receiver image frequencies according to claim 3, characterized in that, The IF intermediate frequency signal has a frequency of 307.2MHz, and the frequency range of the first local oscillator signal is 300MHz~6.4GHz; the center frequency of the bandpass filter is 307.2MHz, and the bandwidth is 100MHz; the analog-to-digital converter is a high-speed parallel output ADC with a sampling clock of not less than 250MHz and an output effective data of not less than 14 bits.
5. The method for suppressing receiver image frequencies according to claim 1, characterized in that, The frequency tuning equation is as follows: = 307.2MHz (1) in, The intermediate frequency, The local oscillator frequency, This refers to the radio frequency.
6. The method for suppressing receiver image frequencies according to claim 1, characterized in that, The calculation process for processing the first digital intermediate frequency signal includes: For the same local oscillator frequency exist Image frequency: （2） The same frequency can be obtained by the following tuning equation. Signal: = 307.2MHz (3) 。 7. The method for suppressing receiver image frequencies according to claim 1, characterized in that, The calculation process for processing the second digital intermediate frequency signal includes: = 312.2MHz (4) = 302.2MHz (5) Through the tuning equations of equations (1) and (4), the same radio frequency signal is obtained through the frequency mapping relationship. The signal frequencies obtained from the two signal acquisition and analysis were the same. Through the tuning equations of equations (3) and (5), the same Frequency mapping relationship The frequency difference between the two signal acquisition and analysis results is 10MHz. Signals with the same frequency in two calculations are retained, while signals with different frequencies in two calculations are treated as mirror frequency signals and discarded.
8. A system for suppressing receiver image frequencies, employing the method for suppressing receiver image frequencies according to any one of claims 1 to 7, characterized in that, include: A primary signal processing module is used to receive a first digital intermediate frequency (IF) signal, wherein the first IF signal is obtained by mixing the radio frequency input signal and the local oscillator signal by a mixer and then performing analog-to-digital conversion; the first IF signal corresponds to the first local oscillator frequency. The first mapping module is used to process the first digital intermediate frequency signal and obtain the first frequency mapping result through FFT operation. The frequency mapping is the mapping relationship between the radio frequency, local oscillator frequency and intermediate frequency defined based on the frequency tuning equation. The secondary processing mapping module is used to fine-tune the first local oscillator frequency by a preset offset to obtain the second local oscillator frequency, obtain the corresponding second digital intermediate frequency signal based on the second local oscillator frequency, perform signal processing on the second digital intermediate frequency signal, and obtain the second frequency mapping result through FFT operation. The identification and rejection module is used to compare the first frequency mapping result with the second frequency mapping result, identify and reject the mirror frequency signal.
9. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that, The memory stores a computer program that can run on a processor. When the processor loads and executes the computer program, it employs a method for suppressing receiver image frequencies as described in any one of claims 1 to 7.
10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is loaded and executed by the processor, it employs a method for suppressing receiver image frequencies as described in any one of claims 1 to 7.