CN117061291A - FM signal demodulation method, system, electronic equipment and medium - Google Patents
FM signal demodulation method, system, electronic equipment and medium Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
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Abstract
The application relates to the technical field of signal processing, and provides a demodulation method, a demodulation system, electronic equipment and a demodulation medium for FM signals, wherein the demodulation method comprises the following steps: quadrature down-conversion is carried out on the input FM signals, and I paths of local signals and Q paths of local signals are output; carrying out low-pass filtering according to the I-path local signal and the Q-path local signal, and outputting an I-path output signal and a Q-path output signal; performing frequency discrimination according to the I-path output signal and the Q-path output signal; and carrying out bit synchronization on the signals after frequency discrimination to obtain code element information. The scheme can be applied to high-performance demodulation scenes of FM signals with any modulation degree without knowing modulation degree information in advance, and simultaneously reduces processing resources required by FM signal demodulation and reduces the requirement on processing hardware.
Description
Technical Field
The present application relates to the field of signal processing technologies, and in particular, to a method, a system, an electronic device, and a medium for demodulating an FM signal.
Background
Telemetry plays an important role in the field of aerospace measurement and control. Missile and spacecraft flight tests often use telemetry systems to acquire their internal operating state and environmental data. The PCM (PCM: pulse Code Modulation), pulse code modulation) -FM (FM: frequency modulation, frequency modulation) telemetry system is a rocket and missile main system at home and abroad. The current common FM signal demodulation method is mostly based on an MSD (Multi-symbol Detection) Detection algorithm, and the algorithm can realize demodulation of FM signals under a fixed modulation degree. However, in practical use, the receiver often needs to demodulate FM signals with different modulation degrees, and even FM signals with unknown modulation degrees, where MSD-based demodulation methods face a significant performance degradation and are not even usable.
In the existing MSD-based FM signal demodulation method, the modulation degree of a received FM signal is required to be known in advance, so that a reference signal which is the same as the modulation degree of the received FM signal is locally reconstructed, then the received signal and the local reference signal are subjected to maximum likelihood calculation, the local reference signal corresponding to the maximum likelihood value is searched, and local code element information corresponding to the reference signal is output as demodulation code element information.
However, in practical applications, the modulation information of the received FM signal is often unknown, which may cause the performance of the MSD algorithm to be significantly reduced or even completely unusable. In addition, the MSD-based FM signal demodulation method also requires a great deal of processing resources, and has high requirements on processing hardware.
Therefore, there is a need to provide a demodulation method, system, electronic device and medium for FM signals, which can apply a high performance demodulation scenario for FM signals with an arbitrary modulation degree without knowing the modulation degree information in advance, and reduce the processing resources required for FM signal demodulation and the requirements for processing hardware.
The above information disclosed in the background section is only for enhancement of understanding of the background of the application and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
The application mainly aims to solve the problem of low demodulation performance of an unknown modulation degree by FM signal modulation, and provides a demodulation method, a demodulation system, electronic equipment and a demodulation medium for an FM signal, which can apply a high-performance demodulation scene of an FM signal with any modulation degree without knowing modulation degree information in advance, reduce processing resources required by FM signal demodulation and reduce the requirement on processing hardware.
To achieve the above object, a first aspect of the present application provides a demodulation method for an FM signal, including the steps of:
quadrature down-conversion is carried out on the input FM signals, and I paths of local signals and Q paths of local signals are output;
carrying out low-pass filtering according to the I-path local signal and the Q-path local signal, and outputting an I-path output signal and a Q-path output signal;
performing frequency discrimination according to the I-path output signal and the Q-path output signal;
and carrying out bit synchronization on the signals after frequency discrimination to obtain code element information.
According to an exemplary embodiment of the present application, the demodulation method of an FM signal further includes: before frequency discrimination, gain control is performed.
According to an exemplary embodiment of the present application, the I-way local signal is cos (2πf c t); the Q-path local signal is sin (2 pi f) c t)；
Wherein f c For the carrier frequency, t represents time.
According to an exemplary embodiment of the present application, the I-path output signal is obtained by using equation 3:
the Q paths of output signals are obtained by adopting a formula 4:
wherein S is I (t) represents an I-way output signal, S Q (t) represents a Q-way output signal; s (t) represents FM signal, f c For carrier frequency, t represents time, cos (2pi.f c t) is an I-path local signal, sin (2pi.f) c t) is Q paths of local signals, h is a modulation degree, A is a signal amplitude, a i Representing symbols, a k For a sequence of symbols, T is the symbol period and q (T) is the behavioral response function.
According to an exemplary embodiment of the present application, the expression of S (t) is formula 1:
wherein S (t) represents an FM signal，f c For carrier frequency, t represents time, cos (2pi.f c t) is an I-path local signal, sin (2pi.f) c t) is Q paths of local signals, h is a modulation degree, A is a signal amplitude, a i Representing symbols, a k For a sequence of symbols, T is the symbol period, q (T) is the behavioral response function, and k is the symbol sequence number.
According to an exemplary embodiment of the present application, the behavioral response function employs equation 2:
where q (T) is the behavioral response function, T is the symbol period, and T is time.
According to an exemplary embodiment of the present application, the method for performing frequency discrimination according to an I output signal and a Q output signal includes: and performing arctangent operation on the I output signal and the Q output signal, and performing first-order differential operation on the signals after the arctangent operation.
According to an exemplary embodiment of the present application, the method for performing the arctangent operation on the I output signal and the Q output signal uses equation 5:
the method for performing first-order differential operation on the signal after the arctangent operation adopts a formula 6:
wherein S is I (t) represents an I-way output signal, S Q (t) represents Q-channel output signal, h is modulation degree, a i Representing the symbol; a, a k For a symbol sequence, T is the symbol period, q (T) is the behavioral response function, and k represents the symbol sequence number.
As a second aspect of the present application, the present application provides a demodulation system for FM signals, comprising, in order:
the quadrature down-conversion module is used for performing quadrature down-conversion on an input FM signal and outputting an I path of local signal and a Q path of local signal;
the low-pass filtering module is used for carrying out low-pass filtering according to the I-path local signal and the Q-path local signal and outputting an I-path output signal and a Q-path output signal;
the frequency discrimination module is used for discriminating frequency according to the I-path output signal and the Q-path output signal; and
and the bit synchronization module is used for carrying out bit synchronization on the signals after frequency discrimination to obtain code element information.
According to an exemplary embodiment of the present application, the gain control module is further provided between the low-pass filtering module and the frequency discrimination module, and is used for performing gain control.
As a third aspect of the present application, the present application provides an electronic apparatus comprising:
one or more processors;
a storage means for storing one or more programs;
the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method of demodulating FM signals.
As a fourth aspect of the present application, the present application provides a computer-readable medium having stored thereon a computer program which, when executed by a processor, implements the FM signal demodulation method.
The demodulation method provided by the application is insensitive to the modulation degree of the FM signal, and can realize high-performance demodulation of the FM signal with any modulation degree; the demodulation algorithm provided by the application does not need large-scale multiplication parallel operation required by the MSD algorithm, so that the processing resource required by demodulation is greatly reduced, and engineering realization is facilitated; the high-performance demodulation of the FM signal can be realized without knowing the modulation degree of the received FM signal in advance, so that the method is very suitable for stable and reliable demodulation under the condition that the modulation degree of the FM signal is rapid and changeable, and has less required processing resources, thereby being very beneficial to engineering realization.
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The above and other objects, features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. The drawings described below are only some embodiments of the present application and other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
Fig. 1 schematically shows a block diagram of a demodulation system of an FM signal.
Fig. 2 schematically shows a step diagram of a demodulation method of an FM signal.
Fig. 3 schematically shows a schematic diagram of bit synchronization.
Fig. 4 schematically illustrates a block diagram of an electronic device.
Fig. 5 schematically shows a block diagram of a computer readable medium.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be embodied in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the application. One skilled in the relevant art will recognize, however, that the application may be practiced without one or more of the specific details, or with other methods, components, devices, steps, etc. In other instances, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the application.
The block diagrams depicted in the figures are merely functional entities and do not necessarily correspond to physically separate entities. That is, the functional entities may be implemented in software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor devices and/or microcontroller devices.
The flow diagrams depicted in the figures are exemplary only, and do not necessarily include all of the elements and operations/steps, nor must they be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the order of actual execution may be changed according to actual situations.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one element from another element. Accordingly, a first component discussed below could be termed a second component without departing from the teachings of the present inventive concept. As used herein, the term "and/or" includes any one of the associated listed items and all combinations of one or more.
Those skilled in the art will appreciate that the drawings are schematic representations of example embodiments and that the modules or flows in the drawings are not necessarily required to practice the application and therefore should not be taken to limit the scope of the application.
According to a first embodiment of the present application, the present application provides a demodulation system for FM signals, as shown in fig. 1, comprising, in order: the device comprises a quadrature down-conversion module, a low-pass filtering module, a gain control module, a frequency discrimination module and a bit synchronization module.
The quadrature down-conversion module is used for performing quadrature down-conversion on the input FM signal and outputting an I path of local signal and a Q path of local signal. The digital signal generally received by the quadrature down-conversion module is often an intermediate frequency signal, and the frequency is higher, which is unfavorable for the processing of the back end. The quadrature down-conversion module is used for down-converting the digital intermediate frequency signal to zero intermediate frequency, so that the signal frequency band is reduced, the rear-end processing rate is reduced, and engineering realization is facilitated.
The low-pass filtering module is used for performing low-pass filtering according to the I-path local signal and the Q-path local signal and outputting an I-path output signal and a Q-path output signal. The low-pass filtering adopts an FIR filter, on one hand, the frequency doubling component generated by the down-conversion part is filtered, and on the other hand, the noise signal outside the band is filtered, so that the signal-to-noise ratio is improved.
The gain control module is arranged between the low-pass filtering module and the frequency discrimination module and is used for performing gain control. The gain control module generally adopts a digital AGC module for controlling the amplitude value of the digital signal, thereby realizing the basically consistent amplitude of the digital signal under different receiving signal to noise ratios, eliminating the influence of amplitude fluctuation on the back-end processing and greatly improving the adaptability of demodulation calculation pairs.
The frequency discrimination module is used for discriminating frequency according to the I-path output signal and the Q-path output signal. The frequency discrimination module is a key processing part of the application. The frequency discrimination output of the FM signal with any modulation degree can be realized by the part.
The bit synchronization module is used for carrying out bit synchronization on the signals after frequency discrimination to obtain code element information. Bit synchronization employs a data transition tracking loop. The synchronization method is insensitive to signal amplitude.
The system of the scheme is insensitive to the modulation degree of the FM signal, and can realize high-performance demodulation of the FM signal with any modulation degree; the demodulation process does not need large-scale multiplication parallel operation required by an MSD algorithm, so that the processing resources required by demodulation are greatly reduced, and engineering realization is facilitated; meanwhile, the system provides complete engineering realization modules, details the function of each module, is very suitable for stable and reliable demodulation under the condition that the FM signal modulation degree is rapid and changeable, has few required processing resources and has high engineering realizability.
According to a second embodiment of the present application, the present application provides a demodulation method of an FM signal, as shown in fig. 2, using the demodulation system of the FM signal of the first embodiment, including the steps of:
s1: and performing quadrature down-conversion on the input FM signal, and outputting an I-path local signal and a Q-path local signal.
I-path local signal is cos (2 pi f) c t); q paths of local signals are sin (2 pi f) c t)；
Wherein f c For the carrier frequency, t represents time.
The quadrature down-conversion is realized by a quadrature down-conversion module, and the digital signal generally received by the quadrature down-conversion is often an intermediate frequency signal, so that the frequency is higher, and the processing of the back end is not facilitated. The quadrature down-conversion module is used for down-converting the digital intermediate frequency signal to zero intermediate frequency, so that the signal frequency band is reduced, the rear-end processing rate is reduced, and engineering realization is facilitated.
S2: and carrying out low-pass filtering according to the I-path local signal and the Q-path local signal, and outputting an I-path output signal and a Q-path output signal.
The low-pass filtering is realized by a low-pass filtering module, and the low-pass filtering adopts an FIR (finite impulse response) filter, so that on one hand, the frequency doubling component generated by the down-conversion part is filtered, and on the other hand, the noise signal outside the band is filtered, and the signal to noise ratio is improved. And carrying out signal estimation according to the I-path local signal and the Q-path local signal, selecting corresponding low-pass filtering parameters, and filtering the I-path local signal and the Q-path local signal to output an I-path output signal and a Q-path output signal with higher signal to noise ratios.
The input FM signal is a digital intermediate frequency signal, and the expression of the FM signal S (t) is formula 1:
wherein S (t) represents an FM signal, f c For carrier frequency, t represents time, cos (2pi.f c t) is an I-path local signal, sin (2pi.f) c t) is Q paths of local signals, h is a modulation degree, A is a signal amplitude, a i Is symbol, a k For a sequence of symbols, T is the symbol period, q (T) is the behavioral response function, and k is the symbol sequence number.
The behavioral response function uses equation 2:
where q (T) is the behavioral response function, T is the symbol period, and T is time.
The output signal of the I path is obtained by adopting a formula 3:
the Q paths of output signals are obtained by adopting a formula 4:
wherein S is I (t) represents an I-way output signal, S Q (t) represents a Q-way output signal; s (t) represents FM signal, f c For carrier frequency, t represents time, cos (2pi.f c t) is an I-path local signal, sin (2pi.f) c t) is Q paths of local signals, h is a modulation degree, A is a signal amplitude, a i Is symbol, a k For a sequence of symbols, T is the symbol period, q (T) is the behavioral response function, and k is the symbol sequence number.
S3: gain control is performed.
The gain control is realized by a gain control module, and a digital AGC (AGC: automatic Gain Control, automatic gain control) module is generally adopted for controlling the amplitude value of the digital signal, so that the amplitude of the digital signal is basically consistent under different receiving signal to noise ratios, the influence of amplitude fluctuation on the back end processing is eliminated, and the adaptability of demodulation calculation pairs is greatly improved.
S4: and carrying out frequency discrimination according to the I-path output signal and the Q-path output signal.
The frequency discrimination part is a key processing part of the application. The frequency discrimination output of the FM signal with any modulation degree can be realized by the part.
The method for frequency discrimination according to the I-path output signal and the Q-path output signal comprises the following steps: and performing arctangent operation on the I output signal and the Q output signal, and performing first-order differential operation on the signals after the arctangent operation.
The method for performing arctangent operation on the I output signal and the Q output signal adopts the formula 5:
the method for performing the first-order differential operation on the signal after the arctangent operation adopts the formula 6:
wherein S is I (t) represents an I-way output signal, S Q (t) represents Q-channel output signal, h is modulation degree, a i Representing the symbol; a, a k For a sequence of symbols, T is the symbol period, q (T) is the behavioral response function, and k is the symbol sequence number.
As can be seen from equation 6, where pi is a constant, T is the symbol period, and is also a constant value when demodulating at a certain rate. The different modulation degrees h are expressed in terms of only the magnitude of the symbol information, without causing a change in the symbol polarity. When the code element is demodulated, the current code element information is judged to be +1 or-1 only by the code element polarity, the code element amplitude has no influence on the judgment, and therefore, the different modulation degrees h have no influence on the final code element demodulation judgment. In the subsequent processing, the application selects a high-performance bit synchronization algorithm insensitive to the code element amplitude, and completes the high-performance demodulation of the FM signal under any modulation degree by matching with the frequency discrimination part.
S5: and carrying out bit synchronization on the signals after frequency discrimination to obtain code element information.
Bit synchronization is performed by a synchronization module, and the bit synchronization adopts a data conversion tracking loop, as shown in fig. 3. The synchronization method is insensitive to signal amplitude.
In fig. 3, in-phase integration is used to integrate over the time interval from the start time to the end time of the symbol, the result of this integration is used to decide the symbol polarity, and when the result of integration is positive, the symbol demodulation output is +1; when the integration result is negative, the symbol demodulation output is-1.
The intermediate phase integration is used for integrating from the middle time of the current code element to the middle time of the next code element, the obtained result of the integration represents the time error value between the bit synchronous clock and the received code element, after the error value is subjected to polarity conversion judgment, loop filtering can be carried out, and the result after the loop filtering is used for generating the bit synchronous clock completely synchronous with the code element, so that stable demodulation of the code element is realized.
Because the principles and methods of the bit synchronization part are mature, the application is only explained in principle here and the implementation process will not be described in detail. It can be seen from the above explanation that the method is insensitive to signal amplitude, and correct code element information can be obtained by demodulating only through polarity judgment of in-phase integration, so that the method can be matched with the previous frequency discrimination part to realize high-performance demodulation of FM signals under any modulation degree.
The scheme can be seen that:
1. the demodulation method provided by the application is insensitive to the modulation degree of the FM signal, and can realize high-performance demodulation of the FM signal with any modulation degree;
2. the demodulation method provided by the application does not need large-scale multiplication parallel operation required by an MSD algorithm, greatly reduces the processing resources required by demodulation, and is beneficial to engineering realization;
3. the application provides a complete engineering realization method based on the proposed demodulation method, details the function of each module, and has high engineering realizability.
Therefore, the scheme of the application can realize high-performance demodulation of the FM signal without knowing the modulation degree of the received FM signal in advance, and is very suitable for stable and reliable demodulation under the condition that the modulation degree of the FM signal is rapid and changeable. And the required processing resources are few, which is very beneficial to engineering realization.
According to a third embodiment of the present application, an electronic device is provided, as shown in fig. 4, and fig. 4 is a block diagram of an electronic device according to an exemplary embodiment.
An electronic device 400 according to such an embodiment of the application is described below with reference to fig. 4. The electronic device 400 shown in fig. 4 is merely an example and should not be construed as limiting the functionality and scope of use of embodiments of the present application.
As shown in fig. 4, the electronic device 400 is embodied in the form of a general purpose computing device. The components of electronic device 400 may include, but are not limited to: at least one processing unit 410, at least one memory unit 420, a bus 430 connecting the different system components (including memory unit 420 and processing unit 410), a display unit 440, and the like.
Wherein the storage unit stores program code that is executable by the processing unit 410 such that the processing unit 410 performs the steps according to various exemplary embodiments of the present application described in the present specification. For example, the processing unit 410 may perform the steps shown in the second embodiment.
The memory unit 420 may include readable media in the form of volatile memory units, such as Random Access Memory (RAM) 4201 and/or cache memory 4202, and may further include Read Only Memory (ROM) 4203.
The storage unit 420 may also include a program/utility 4204 having a set (at least one) of program modules 4205, such program modules 4205 including, but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of which may include an implementation of a network environment.
Bus 430 may be a local bus representing one or more of several types of bus structures including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or using any of a variety of bus architectures.
The electronic device 400 may also communicate with one or more external devices 400' (e.g., keyboard, pointing device, bluetooth device, etc.), devices that enable a user to interact with the electronic device 400, and/or any devices (e.g., routers, modems, etc.) that the electronic device 400 can communicate with one or more other computing devices. Such communication may occur through an input/output (I/O) interface 450. Also, electronic device 400 may communicate with one or more networks such as a Local Area Network (LAN), a Wide Area Network (WAN), and/or a public network, such as the Internet, through network adapter 460. The network adapter 460 may communicate with other modules of the electronic device 400 via the bus 430. It should be appreciated that although not shown, other hardware and/or software modules may be used in connection with electronic device 400, including, but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, data backup storage systems, and the like.
From the above description of embodiments, those skilled in the art will readily appreciate that the example embodiments described herein may be implemented in software, or may be implemented in software in combination with the necessary hardware.
Thus, according to a fourth embodiment of the present application, the present application provides a computer readable medium. As shown in fig. 5, the technical solution according to the embodiment of the present application may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (may be a CD-ROM, a U-disk, a mobile hard disk, etc.) or on a network, and includes several instructions to cause a computing device (may be a personal computer, a server, or a network device, etc.) to perform the above-described method according to the embodiment of the present application.
The software product may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. The readable storage medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: an electrical connection having one or more wires, a portable 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), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The computer readable storage medium may include a data signal propagated in baseband or as part of a carrier wave, with readable program code embodied therein. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A readable storage medium may also be any readable medium that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a readable storage medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.
Program code for carrying out operations of the present application may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device, partly on a remote computing device, or entirely on the remote computing device or server. In the case of remote computing devices, the remote computing device may be connected to the user computing device through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computing device (e.g., connected via the Internet using an Internet service provider).
The computer-readable medium carries one or more programs which, when executed by one of the devices, cause the computer-readable medium to implement the functions of the second embodiment.
Those skilled in the art will appreciate that the modules may be distributed throughout several devices as described in the embodiments, and that corresponding variations may be implemented in one or more devices that are unique to the embodiments. The modules of the above embodiments may be combined into one module, or may be further split into a plurality of sub-modules.
From the above description of embodiments, those skilled in the art will readily appreciate that the example embodiments described herein may be implemented in software, or in combination with the necessary hardware. Thus, the technical solution according to the embodiments of the present application may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (may be a CD-ROM, a U-disk, a mobile hard disk, etc.) or on a network, and includes several instructions to cause a computing device (may be a personal computer, a server, a mobile terminal, or a network device, etc.) to perform the method according to the embodiments of the present application.
The exemplary embodiments of the present application have been particularly shown and described above. It is to be understood that this application is not limited to the precise arrangements, instrumentalities and instrumentalities described herein; on the contrary, the application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (10)
1. A method for demodulating an FM signal, comprising the steps of:
quadrature down-conversion is carried out on the input FM signals, and I paths of local signals and Q paths of local signals are output;
carrying out low-pass filtering according to the I-path local signal and the Q-path local signal, and outputting an I-path output signal and a Q-path output signal;
performing frequency discrimination according to the I-path output signal and the Q-path output signal;
and carrying out bit synchronization on the signals after frequency discrimination to obtain code element information.
2. The method for demodulating an FM signal according to claim 1, further comprising: before frequency discrimination, gain control is performed.
3. The method of demodulating an FM signal according to claim 1, wherein said I-path local signal is cos (2ρf c t); the Q-path local signal is sin (2 pi f) c t)；
Wherein f c For the carrier frequency, t represents time.
4. The method for demodulating an FM signal according to claim 1, wherein said I output signal is obtained by using formula 3:
the Q paths of output signals are obtained by adopting a formula 4:
wherein S is I (t) represents an I-way output signal, S Q (t) represents a Q-way output signal; s (t) represents FM signal, f c For carrier frequency, t represents time, cos (2pi.f c t) is an I-path local signal, sin (2pi.f) c t) is Q paths of local signals, h is a modulation degree, A is a signal amplitude, a i Representing symbols, a k For a sequence of symbols, T is the symbol period and q (T) is the behavioral response function.
5. The method for demodulating an FM signal according to claim 4, wherein the expression of S (t) is formula 1:
wherein S (t) represents an FM signal, f c For carrier frequency, t represents time, cos (2pi.f c t) is an I-path local signal, sin (2pi.f) c t) is Q paths of local signals, h is a modulation degree, A is a signal amplitude, a i Representing symbols, a k For the symbol sequence, T is the symbol period, q (T) is the behavioral response function, and k is the symbol sequence number;
the behavioral response function employs equation 2:
where q (T) is the behavioral response function, T is the symbol period, and T is time.
6. The method for demodulating an FM signal according to claim 1, wherein said method for frequency discrimination based on an I-path output signal and a Q-path output signal comprises: and performing arctangent operation on the I output signal and the Q output signal, and performing first-order differential operation on the signals after the arctangent operation.
7. The method for demodulating an FM signal according to claim 6, wherein said method for performing an arctangent operation on an I output signal and a Q output signal uses equation 5:
the method for performing first-order differential operation on the signal after the arctangent operation adopts a formula 6:
wherein S is I (t) represents an I-way output signal, S Q (t) represents Q-channel output signal, h is modulation degree, a i Representing the symbol; a, a k For a sequence of symbols, T is the symbol period, q (T) is the behavioral response function, and k is the symbol sequence number.
8. A demodulation system for FM signals, comprising, in order:
the quadrature down-conversion module is used for performing quadrature down-conversion on an input FM signal and outputting an I path of local signal and a Q path of local signal;
the low-pass filtering module is used for carrying out low-pass filtering according to the I-path local signal and the Q-path local signal and outputting an I-path output signal and a Q-path output signal;
the frequency discrimination module is used for discriminating frequency according to the I-path output signal and the Q-path output signal; and
and the bit synchronization module is used for carrying out bit synchronization on the signals after frequency discrimination to obtain code element information.
9. An electronic device, comprising:
one or more processors;
a storage means for storing one or more programs;
the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method of demodulating FM signals of any of claims 1-7.
10. A computer readable medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements a method of demodulating an FM signal according to any one of claims 1-7.
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| CN202310994608.XA CN117061291A (en) | 2023-08-09 | 2023-08-09 | FM signal demodulation method, system, electronic equipment and medium |
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Application publication date: 20231114 |