CN107171995B - GMSK signal generation device and method, and signal detection device and method - Google Patents
GMSK signal generation device and method, and signal detection device and method 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
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/12—Modulator circuits; Transmitter circuits
- H04L27/122—Modulator circuits; Transmitter circuits using digital generation of carrier signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
- H04L27/144—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements
- H04L27/148—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using filters, including PLL-type filters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
- H04L27/144—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements
- H04L27/152—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using controlled oscillators, e.g. PLL arrangements
- H04L27/1525—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using controlled oscillators, e.g. PLL arrangements using quadrature demodulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
- H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
Abstract
The invention discloses a GMSK signal generation device and method and a signal detection device and method, relates to the technical field of communication, and is used for achieving full digitalization of GMSK signal generation. The GMSK signal generation method comprises the following steps: generating a random code according to the user data, and carrying out differential encoding on the random code; oversampling the differentially encoded signal, filling with zero values, and performing Gaussian filtering with a total interpolation multiple of L0，L0Is a positive integer greater than 0; the Gaussian filtered signal is multiplied by pi/2, accumulated phase by phase, and divided by the total interpolation multiple L at each accumulation0Obtaining a phase fei (t); processing the phase fei (t) by using an orthogonal modulation mode or a cosine phase superposition mode to obtain a phase output numerical value; obtaining a GMSK signal of orthogonal modulation according to the phase output value; the GMSK signal is transmitted to the digital-to-analog converter. The invention is used for realizing the full digitalization of GMSK signal generation.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a GMSK signal generation apparatus and method, and a signal detection apparatus and method.
Background
Modulation of a signal generator is a key technique for improving communication quality in a communication system to match signal characteristics with channel characteristics. Most modern communication systems use digital modulation techniques, but general digital modulation techniques such as ASK (Amplitude-Shift Keying), FSK (Frequency-Shift Keying), PSK (Phase-Shift Keying), QPSK (Quadrature Phase Shift Keying), and MSK (Minimum-Shift Keying) cannot satisfy the requirements of mobile communication.
GMSK (Gaussian Filtered Minimum-shift keying) is a technology developed from MSK, a GMSK modulation method can meet strict requirements for adjacent channel interference in a Mobile Communication environment, and the GMSK modulation method is widely used by GSM (Global System for Mobile Communication) with good performance. Fig. 1 is a spectrum diagram of different modulation schemes, and it can be seen from fig. 1 that QPSK spectrum is slowly faded, resulting in relatively serious spectrum leakage; MSK frequency spectrum leakage is small; the GMSK spectrum has the fastest and steepest stopband fading, the fastest spectral fading and the smallest spectral leakage. The GMSK signal most easily meets the spectral template requirements and therefore the signal stability is the best.
The GMSK signal generator is generally implemented by using an analog filter and a voltage-controlled oscillator, but the implementation mode of an analog circuit applied in the analog filter is low in flexibility, and parameter configuration needs to be implemented by changing off-chip hardware parameters, so that the GMSK signal generator using analog or analog-digital mixing cannot adapt to the development of a full-digital communication system.
Disclosure of Invention
The invention aims to provide a GMSK signal generation device and method, a GMSK signal detection device and method, which are used for realizing full digitalization of GMSK signal generation so as to adapt to development of a full digitalization communication system.
In order to achieve the above object, a first aspect of the present invention provides a GMSK signal generating method, which adopts the following technical solution:
a GMSK signal generation method includes:
step S1, generating a random code according to the user data, and differentially encoding the random code;
step S2, oversampling the signal after differential coding, filling zero value, and Gaussian filtering, wherein the total interpolation multiple adopted in the Gaussian filtering is L0，L0Is a positive integer greater than 0;
step S3, the signal after Gaussian filteringThe sign is multiplied by pi/2, phase-by-phase accumulated, and divided by the total interpolation factor L at each accumulation0Obtaining a phase fei (t);
step S4, processing the phase fei (t) by using an orthogonal modulation mode or a cosine phase superposition mode to obtain a phase output numerical value;
step S5, obtaining a GMSK signal of orthogonal modulation according to the phase output value;
and step S6, transmitting the GMSK signal to a digital-to-analog converter.
Further, the total interpolation factor L used in the gaussian filtering in step S20＝fs/fbWherein f issAs the sampling rate, fbIs the baseband signal rate.
Alternatively, when the FIR gaussian filtering is performed in step S2, the 3dB bandwidth BT is 0.3, 0.5, or 0.7.
Optionally, the gaussian filtering in step S2 includes: sequentially performing FIR Gaussian filtering and multi-stage HB filtering, and obtaining total interpolation multiple L of the Gaussian filtering0Is the product of the interpolation multiple of FIR gaussian filtering and the interpolation multiple of multilevel HB filtering.
Exemplarily, in step S4, the phase fei (t) is processed by using the quadrature modulation mode, and a specific formula for obtaining the GMSK signal is as follows:
Ith(t)＝cos(fei(t))；
Qth(t)＝sin(fei(t))；
Gsmk(t)＝Ith(t)*cos(2*π*fc/fs*t)-Qth(t)*sin(2*π*fc/fs*t)；
wherein Gsmk (t) is GMSK signal; ith (t) is the I branch signal; qth (t) is Q branch signal; f. ofcIs the carrier frequency; f. ofsIs the sampling rate; t is time.
Exemplarily, in step S4, the phase fei (t) is processed by using a cosine phase superposition mode, and a specific formula for obtaining the GMSK signal is as follows:
Gsmk(t)＝cos(2*π*fc/fs*t)+fei(t)+θ(0)；
wherein Gsmk (t) is GMSK signal; f. ofcIs the carrier frequency; f. ofsIs the sampling rate; theta (0) is an initial phase angle; t is time.
The GMSK signal generating method provided by the invention comprises the steps, so that digitization is realized in the process of generating the GMSK signal by using the GMSK signal generating method, and the GMSK signal generating method can be well adapted to the development of a full-digitization communication system.
A second aspect of the present invention provides a GMSK signal generating apparatus, which adopts the following technical solution:
the GMSK signal generating device comprises a difference module, a filtering module, a linear phase accumulation module, a phase mixing and superposition module and a COSLUT table module which are sequentially connected; the difference module is used for generating a random code according to the user data and carrying out difference coding on the random code; the filtering module is used for oversampling the differentially encoded signals, filling zero values and carrying out Gaussian filtering, wherein the total interpolation multiple adopted during the Gaussian filtering is L0，L0Is a positive integer greater than 0; the linear phase accumulation module is used for multiplying the Gaussian filtered signals by pi/2, carrying out phase accumulation one by one, and dividing the accumulated signal by the total interpolation multiple L during each accumulation0Obtaining a phase fei (t); the phase mixing and superposing module is used for processing the phase fei (t) by using an orthogonal modulation mode or a cosine phase superposing mode to obtain a phase output numerical value; the COSLUT table module is used for obtaining a GMSK signal which is orthogonally modulated according to the phase output value and transmitting the GMSK signal to the digital-to-analog converter.
Further, the filtering module comprises an FIR Gaussian filter and a multistage HB filter.
The GMSK signal generating device provided by the invention has the structure, so that digitization is realized in the process of generating the GMSK signal by using the GMSK signal generating device, and the GMSK signal generating device can be well adapted to the development of a full-digitization communication system.
The third aspect of the present invention provides a GMSK signal detection method, which adopts the following technical scheme:
a GMSK signal detection method comprises the following steps:
step S1', quadrature-demodulating the GMSK signal acquired from the analog-to-digital converter;
step S2 ', performing multilevel HB filtering and extraction on the two signals obtained after orthogonal demodulation, and performing gaussian filtering to obtain an I branch signal and a Q branch signal, where a bandwidth BT' used in the gaussian filtering is different from a bandwidth BT used in generating a GMSK signal, and BT ═ BT (1+ x), where x is a value greater than 0, and the size of x is determined according to the size of frequency offset;
step S3', respectively carrying out bit synchronization adjustment on the I branch signal and the Q branch signal, and finishing extraction to obtain a plurality of optimal sampling points;
step S4', measuring and correcting frequency offset, and measuring and correcting phase offset to obtain I (k) and Q (k), wherein k is the serial number of the sampling point, and k is a positive integer greater than 1;
step S5', performing one-bit differential detection on i (k) and q (k), respectively;
step S6', differentially decodes the detection result.
The GMSK signal detection method provided by the invention comprises the steps, so that the process of detecting the GMSK signal by using the GMSK signal detection method is simple, and a good detection effect can be achieved.
The fourth aspect of the present invention provides a GMSK signal detection apparatus, which adopts the following technical scheme:
the GMSK signal detection device comprises an orthogonal demodulation module, a filtering extraction module, a synchronous adjustment module, a correction module, a differential detection module and a differential decoding module which are sequentially connected; the orthogonal demodulation module is used for carrying out orthogonal demodulation on GMSK signals acquired from the analog-to-digital converter; the filtering and extracting module is used for respectively performing multistage HB filtering and extraction on the two signals obtained after orthogonal demodulation and Gaussian filtering to obtain an I branch signal and a Q branch signal, wherein the bandwidth BT 'adopted in the Gaussian filtering is different from the BT adopted in the GMSK signal generation, and the BT' ═ BT (1+ x), wherein x is a numerical value larger than 0, and the size of x is determined according to the frequency offset; the synchronous adjusting module is used for respectively carrying out bit synchronous adjustment on the I branch signal and the Q branch signal, completing extraction and obtaining a plurality of optimal sampling points; the correction module is used for measuring and correcting frequency offset and phase offset to obtain I (k) and Q (k), wherein k is the serial number of a sampling point, and k is a positive integer greater than 1; the differential detection module is used for carrying out one-bit differential detection on I (k) and Q (k) respectively; and the differential decoding module is used for carrying out differential decoding on the detection result.
The GMSK signal detection device provided by the invention has the structure, so that the process of detecting the GMSK signal by using the GMSK signal detection device is simple, and a good detection effect can be achieved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a spectrum diagram of different modulation schemes;
fig. 2 is a diagram of the phase path of a GMSK signal in an embodiment of the present invention;
fig. 3 is a flowchart of a GMSK signal generation method in an embodiment of the present invention;
FIG. 4 shows the total interpolation factor L in the embodiment of the present invention0A phase superposition diagram equal to 8;
fig. 5 is a schematic structural diagram of a GMSK signal generating apparatus according to an embodiment of the present invention;
fig. 6 is a flowchart of a GMSK signal detection method in an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a GMSK signal detection apparatus according to an embodiment of the present invention.
Description of reference numerals:
1-a difference module; 2, a filtering module; 3-a linear phase accumulation module;
4-a phase mixing and superimposing module; 5-COSLUT table module; 1' -quadrature demodulation module;
2' -a filter decimation module; 3' -a synchronization adjustment module; 4' -a correction module;
5' -a differential detection module; 6' -differential decoding module.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to facilitate the understanding of the technical solutions of the present application by those skilled in the art, some theoretical bases related to the technical solutions of the present application are described in detail herein.
The model for GMSK is as follows:
wherein E iscFor the energy of each symbol, T is the symbol duration, fcIs the carrier frequency, t is the time, Φ (t) is the GMSK modulation phase, θ is the random phase from the guard band, and is constant during a burst.
The GMSK modulation phase Φ (t) is:
wherein g (x) is the impulse response of the Gaussian premodulation filter; h is the modulation index, typically 0.5; t is time; t is a symbol duration; NRZ (Non-Return to Zero) bitcells modulated at time i are denoted as ai。
As can be seen from the above, the phase path of the GMSK signal is determined by the shape of the pulse, or the phase of the modulated wave changes within a symbol depending on the area of the pulse between them. Since the gaussian filtered pulse has no sharp edges and no inflection points, its phase path is further smoothed, as shown in fig. 2. It should be noted that, since adjacent pulses overlap, the influence of adjacent symbols is considered when determining the area of a pulse within a symbol. Thus, under different code stream patterns, the pulse area in one code element is different, and the corresponding phase path is also different.
Example one
An embodiment of the present invention provides a method for generating a GMSK signal, and specifically, as shown in fig. 3, the method for generating GMSK signal includes:
step S1, generating a random code according to the user data, and differentially encoding the random code;
step S2, oversampling the signal after differential coding, filling zero value, and Gaussian filtering, wherein the total interpolation multiple adopted in the Gaussian filtering is L0，L0Is a positive integer greater than 0; the output signal after gaussian filtering is actually a phase instantaneous value.
Step S3, multiplying the Gaussian filtered signal by pi/2, accumulating phase by phase, and dividing by the total interpolation multiple L during each accumulation0Obtaining a phase fei (t);
step S4, processing the phase fei (t) by using an orthogonal modulation mode or a cosine phase superposition mode to obtain a phase output numerical value; the algorithm implementation typically selects the quadrature modulation mode.
Step S5, obtaining a GMSK signal of orthogonal modulation according to the phase output value;
and step S6, transmitting the GMSK signal to a digital-to-analog converter.
The GMSK signal generating method provided by the invention comprises the steps, so that digitization is realized in the process of generating the GMSK signal by using the GMSK signal generating method, and the GMSK signal generating method can be well adapted to the development of a full-digitization communication system.
Further, the total interpolation factor L used in the gaussian filtering in step S20Can be determined according to the signal bandwidth and the sampling rate of the signal, for example, if the signal bandwidth is 1MHZ and the signal rate is 32MSPS, then the total interpolation multiple L is required0Should be less than or equal to32. Since the signal bandwidth and the baseband signal rate have a corresponding relationship, L0The specific value of (b) may also be determined based on the baseband signal rate and the sampling rate of the signal. Exemplarily, L0＝fs/fbWherein f issAs the sampling rate, fbIs the baseband signal rate.
Optionally, when performing gaussian filtering in step S2, the 3dB bandwidth BT used is 0.3, 0.5, or 0.7, preferably 0.5.
Optionally, the gaussian filtering in step S2 includes: sequentially performing FIR (Finite Impulse Response) Gaussian filter and multistage HB (Half-Band) filter, wherein the total interpolation multiple L of the Gaussian filter0Is the product of the interpolation multiple of FIR gaussian filtering and the interpolation multiple of multilevel HB filtering. To require a total interpolation factor L0For example, the FIR gaussian filter can perform 8-fold interpolation, and the multi-stage HB filter can perform 4-fold interpolation, hierarchical processing. From the above, the interpolation multiple of the multi-stage HB filtering is determined by the total interpolation multiple L0And (6) determining. In addition, since the interpolation multiple of the multi-stage HB filtering is implemented by multiple stages, the performance can be guaranteed while saving resources.
FIG. 4 shows the total interpolation factor L0And 8, representing the superposition of phases at different moments. In fig. 4, the vertical axis Y represents the instantaneous value of the phase of the gaussian-filtered signal phase superposition, the horizontal axis X represents the time of the input signal, and the value of X is the time T divided by the sampling period TbAnd the sampling points are represented. In fig. 4, the total interpolation multiple is 8, and the amplitude oscillation period is 8, as can be seen from fig. 4, in the GMSK modulation mode, the ripple of the input signal after GMSK filtering appears smooth, and in the MSK modulation mode, because there is no filtering, the curve is straight.
Exemplarily, in step S4, the phase fei (t) is processed by using the quadrature modulation mode, and a specific formula for obtaining the GMSK signal is as follows:
Ith(t)＝cos(fei(t))；
Qth(t)＝sin(fei(t))；
Gsmk(t)＝Ith(t)*cos(2*π*fc/fs*t)-Qth(t)*sin(2*π*fc/fs*t)；
wherein Gsmk (t) is GMSK signal; ith (t) is the I branch signal; qth (t) is Q branch signal; f. ofcIs the carrier frequency; f. ofsIs the sampling rate; t is time.
Exemplarily, in step S4, the phase fei (t) is processed by using a cosine phase superposition mode, and a specific formula for obtaining the GMSK signal is as follows:
Gsmk(t)＝cos(2*π*fc/fs*t)+fei(t)+θ(0)；
wherein Gsmk (t) is GMSK signal; f. ofcIs the carrier frequency; f. ofsIs the sampling rate; theta (0) is an initial phase angle, and the value of theta (0) can be selected as 0 for calculation convenience; t is time.
Corresponding to the GMSK signal generation method described above, an embodiment of the present invention further provides a GMSK signal generation apparatus, and specifically, as shown in fig. 5, the GMSK signal generation apparatus includes a difference module 1, a filtering module 2, a linear phase accumulation module 3, a phase mixing and superimposing module 4, and a COSLUT table module 5, which are sequentially connected; the difference module 1 is used for generating a random code according to user data and differentially encoding the random code; the filtering module 2 is used for oversampling the differentially encoded signals, filling zero values, and performing Gaussian filtering, wherein the total interpolation multiple adopted in the Gaussian filtering is L0，L0Is a positive integer greater than 0; the linear phase accumulation module 3 is used for multiplying the Gaussian filtered signals by pi/2, carrying out phase-by-phase accumulation, and dividing the accumulated signals by the total interpolation multiple L during each accumulation0Obtaining a phase fei (t); the phase hybrid superposition module 4 is configured to process the phase fei (t) by using an orthogonal modulation mode or a cosine phase superposition mode to obtain a phase output value; the COSLUT table module 5 is configured to obtain a GMSK signal of quadrature modulation according to the phase output value, and transmit the GMSK signal to the digital-to-analog converter.
Specifically, the signal output by the filtering module 2 is a phase instantaneous value, the phase instantaneous value is processed by the linear phase accumulation module 3 and then output to the phase mixing and superimposing module 4, the phase mixing and superimposing module 4 performs phase mixing and superimposing with the frequency control word, and the phase instantaneous value is used as a final phase output value and sent to the coslaut table module 5, and the coslaut table module 5 performs COS-ROM table lookup to obtain a final quadrature-modulated GMSK signal.
It should be noted that the specific details of each step in the GMSK signal generation method are all applicable to the GMSK signal generation apparatus mentioned herein, and are not described herein again.
In order to facilitate understanding and implementation for those skilled in the art, the following embodiments of the present invention further describe the filtering module 2, the phase mixing and superimposing module 4, and the coslout table module 5.
In order to ensure that the filtering module 2 has a good effect, the filtering module 2 is selected to comprise an FIR Gaussian filter and a multistage HB filter in the embodiment of the invention, wherein the FIR Gaussian filter is responsible for a typical Gaussian filtering forming function, the multistage HB filter has expansibility, and simultaneously, the coefficient of the Gaussian filter can be dynamically configured after the coefficient of the Gaussian filter is calculated in real time, so that the method is more flexible and accurate than a storage mode. The coefficients of the FIR gaussian filter should not be too long. Total interpolation factor L of the filter module 20Is the product of the interpolation multiple of the FIR gaussian filter and the interpolation multiple of the multistage HB filter. To require a total interpolation factor L0For example, the FIR gaussian filter can perform 8 times interpolation, and the multi-stage HB filter can perform 4 times interpolation, hierarchical processing. From the above, the interpolation multiple of the multi-stage HB filter is determined by the total interpolation multiple L0And (6) determining. In addition, since the interpolation multiple of the multi-stage HB filter is implemented by multiple stages, the performance can be guaranteed while saving resources.
The GMSK signal generating device provided by the invention has the structure, so that digitization is realized in the process of generating the GMSK signal by using the GMSK signal generating device, and the GMSK signal generating device can be well adapted to the development of a full-digitization communication system.
Example two
In order to facilitate detection of a GMSK signal generated by using the GMSK signal generation method and/or the apparatus in the first embodiment, an embodiment of the present invention provides a GMSK signal detection method (i.e., a receiving method), as shown in fig. 6, where the GMSK signal detection method includes:
step S1', quadrature-demodulating the GMSK signal acquired from the analog-to-digital converter;
step S2 ', performing multilevel HB filtering and extraction on the two signals obtained after orthogonal demodulation, and performing gaussian filtering to obtain an I branch signal and a Q branch signal, where a bandwidth BT ' used in the gaussian filtering is different from the BT used in generating the GMSK signal, and BT ' ═ BT (1+ x), where x is a value greater than 0, and the size of x is determined according to the magnitude of frequency offset, where the larger the frequency offset is, the larger x is, for example, when the frequency offset is 20khz, x is 0.5, when the frequency offset is 10khz, x is 0.25, and so on; illustratively, x is 0.5, i.e., BT 'is 1.5, and BT' is 0.99.
Step S3', respectively carrying out bit synchronization adjustment on the I branch signal and the Q branch signal, and finishing extraction to obtain a plurality of optimal sampling points;
step S4', measuring and correcting frequency offset, and measuring and correcting phase offset to obtain I (k) and Q (k), wherein k is the serial number of the sampling point, and k is a positive integer greater than 1;
step S5', performing one-bit differential detection on i (k) and q (k), respectively;
step S6', differentially decodes the detection result.
The GMSK signal detection method provided by the invention comprises the steps, so that the process of detecting the GMSK signal by using the GMSK signal detection method is simple, and a good detection effect can be achieved. In addition, the use of one-bit differential detection also has the advantage of simple algorithm and easy implementation.
As can be seen from the above description, in the GMSK signal detection process, the modulated GMSK signal is digitally down-converted and then restored to two branch signals, i (k) and q (k), and then demodulated by using one-bit differential detection.
Using one-bit differential detection, the amount of change in phase of the signal received in one bit period can be found. This amount of change in phase can be represented by:
wherein T is time, TbIs one symbol time; d (t) is input data; h (t) is the impulse response of a gaussian filter,
BT is the 3dB bandwidth of the Gaussian filter;
according to the formula, the compound has the advantages of,
does not exceed TbSo that the maximum value of the phase change possible within one bit period
The amount of phase change of a transmitted symbol in a bit period time can also be found by one-bit differential detection. This amount of change in phase can be expressed as:
when Q (k) branch signal data
Is greater than or equal to zero, the received data is "1"; when I (k) branch signal data
Is less than zero, the received data is "1".
Similarly, corresponding to the GMSK signal detection method described above, an embodiment of the present invention further provides a GMSK signal detection apparatus, and specifically, as shown in fig. 7, the GMSK signal detection apparatus includes an orthogonal demodulation module 1 ', a filtering extraction module 2', a synchronization adjustment module 3 ', a correction module 4', a differential detection module 5 ', and a differential decoding module 6' that are sequentially connected; the orthogonal demodulation module 1' is used for performing orthogonal demodulation on GMSK signals acquired from an analog-to-digital converter; the filtering and extracting module 2 'is configured to perform multistage HB filtering and extraction on the two signals obtained after the orthogonal demodulation, and perform gaussian filtering to obtain an I branch signal and a Q branch signal, where a bandwidth BT' used in the gaussian filtering is different from a bandwidth BT used in generating a GMSK signal, and BT ═ BT (1+ x), where x is a numerical value greater than 0, and a size of x is determined according to a size of a frequency offset; the synchronous adjusting module 3' is used for respectively carrying out bit synchronous adjustment on the I branch signal and the Q branch signal, completing extraction and obtaining a plurality of optimal sampling points; the correction module 4' is used for measuring and correcting frequency offset and phase offset to obtain I (k) and Q (k), wherein k is the serial number of a sampling point, and k is a positive integer greater than 1; the differential detection module 5' is used for carrying out one-bit differential detection on I (k) and Q (k), respectively; the differential decoding module 6' is used for performing differential decoding on the detection result.
It should be noted that the specific details of each step in the GMSK signal detection method are all applicable to the GMSK signal detection apparatus mentioned herein, and are not described herein again.
The GMSK signal detection device provided by the invention has the structure, so that the process of detecting the GMSK signal by using the GMSK signal detection device is simple, and a good detection effect can be achieved.
Through the above description of the embodiments, those skilled in the art will clearly understand that the present invention may be implemented by software plus necessary general hardware, and certainly may also be implemented by hardware, but in many cases, the former is a better embodiment. Based on such understanding, the technical solutions of the present invention may be substantially implemented or a part of the technical solutions contributing to the prior art may be embodied in the form of a software product, which is stored in a readable storage medium, such as a floppy disk, a hard disk, or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the methods according to the embodiments of the present invention.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (3)
1. A method of generating a GSMK signal, comprising:
step S1, generating a random code according to the user data, and differentially encoding the random code;
step S2, oversampling the differentially encoded signals, filling zero values, and performing Gaussian filtering, wherein the total interpolation multiple adopted during the Gaussian filtering is L0, and L0 is a positive integer greater than 0;
step S3, multiplying the Gaussian-filtered signals by pi/2, accumulating the phases one by one, and dividing the accumulated signals by the total interpolation multiple L0 to obtain a phase fei (t);
step S4, processing the phase fei (t) by using an orthogonal modulation mode or a cosine phase superposition mode to obtain a phase output numerical value;
step S5, obtaining a GMSK signal of orthogonal modulation according to the phase output value;
step S6, transmitting the GMSK signal to a digital-to-analog converter;
when performing gaussian filtering in step S2, the total interpolation multiple L0 is fs/fb, where fs is the sampling rate and fb is the baseband signal rate;
the gaussian filtering in step S2 includes: sequentially performing FIR Gaussian filtering and multi-stage HB filtering, wherein the total interpolation multiple L0 of the Gaussian filtering is the product of the interpolation multiple of the FIR Gaussian filtering and the interpolation multiple of the multi-stage HB filtering;
in step S4, the phase fei (t) is processed using the quadrature modulation mode, and the specific formula for obtaining the GMSK signal is:
Ith(t)＝cos(fei(t))；
Qth(t)＝sin(fei(t))；
Gsmk(t)＝Ith(t)*cos(2*π*fc/fs*t)-Qth(t)*sin(2*π*fc/fs*t)；
wherein Gsmk (t) is GMSK signal; ith (t) is the I branch signal; qth (t) is Q branch signal; fc is the carrier frequency; fs is the sampling rate; t is time;
in step S4, the cosine phase superposition mode is used to process the phase fei (t), and the specific formula of the GMSK signal is as follows:
Gsmk(t)＝cos(2*π*fc/fs*t)+fei(t)+θ(0)；
wherein Gsmk (t) is GMSK signal; fc is the carrier frequency; fs is the sampling rate; theta (0) is an initial phase angle; t is time;
after transmitting the GMSK signal to the digital-to-analog converter, detecting the GSMK signal, specifically including:
step S1', quadrature-demodulating the GMSK signal acquired from the analog-to-digital converter;
step S2 ', performing multilevel HB filtering and extraction on the two signals obtained after orthogonal demodulation, and performing gaussian filtering to obtain an I branch signal and a Q branch signal, where BT' used in gaussian filtering is different from BT used in gsm k signal generation, BT ═ BT (1+ x), where x is a value greater than 0, and the size of x is determined according to the size of frequency offset;
step S3', respectively carrying out bit synchronization adjustment on the I branch signal and the Q branch signal, and finishing extraction to obtain a plurality of optimal sampling points;
step S4', measuring and correcting frequency offset, and measuring and correcting phase offset to obtain I (k) and Q (k), wherein k is the serial number of the sampling point, and k is a positive integer greater than 1;
step S5', performing one-bit differential detection on i (k) and q (k), respectively;
step S6', differentially decoding the detection result;
using one-bit differential detection to find the amount of change in phase of the signal received in one bit period is expressed by:
wherein t is time, and Tb is a code element time; d (t) is input data;
BT is the 3dB bandwidth of the Gaussian filter;
the amount of phase change of a transmitted symbol in a bit period time, expressed as bit differential detection, can also be found out
When the value of the q (k) branch signal data is greater than or equal to zero, the received data is "1"; when the value of the i (k) branch signal data is less than zero, the received data is "1".
2. The method of claim 1, wherein the 3dB bandwidth BT used in the gaussian filtering in step S2 is 0.3, 0.5 or 0.7.
3. The GSMK signal generating device is characterized by comprising a difference module, a filtering module, a linear phase accumulation module, a phase mixing superposition module and a COSLUT table module which are sequentially connected; the difference module is used for generating a random code according to the user data and carrying out difference coding on the random code; the filtering module is used for oversampling the differentially encoded signals, filling zero values and carrying out Gaussian filtering, wherein the total interpolation multiple adopted in the Gaussian filtering is L, and L is a positive integer greater than 0; the linear phase accumulation module is used for multiplying the signals subjected to Gaussian filtering by pi/2, accumulating the phases one by one, and dividing the accumulated signals by a total interpolation multiple L during each accumulation to obtain a phase fei (t); the phase mixing and superposing module is used for processing the phase fei (t) by using an orthogonal modulation mode or a cosine phase superposing mode to obtain a phase output numerical value; the COSLUT table module is used for obtaining a GMSK signal which is orthogonally modulated according to the phase output value and transmitting the GMSK signal to the digital-to-analog converter;
the filtering module comprises an FIR Gaussian filter and a multistage HB filter;
the phase hybrid superposition module is specifically configured to process the phase fei (t) in the quadrature modulation mode, and a specific formula for obtaining the GMSK signal is as follows:
Ith(t)＝cos(fei(t))；
Qth(t)＝sin(fei(t))；
Gsmk(t)＝Ith(t)*cos(2*π*fc/fs*t)-Qth(t)*sin(2*π*fc/fs*t)；
wherein Gsmk (t) is GMSK signal; ith (t) is the I branch signal; qth (t) is Q branch signal; fc is the carrier frequency; fs is the sampling rate; t is time;
the phase hybrid superposition module is specifically configured to process the phase fei (t) in a cosine phase superposition mode, and the specific formula for obtaining the GMSK signal is as follows:
Gsmk(t)＝cos(2*π*fc/fs*t)+fei(t)+θ(0)；
wherein Gsmk (t) is GMSK signal; fc is the carrier frequency; fs is the sampling rate; theta (0) is an initial phase angle; t is time;
after the COSLUT table module transmits GMSK signals to the digital-to-analog converter, the COSLUT table module further comprises an orthogonal demodulation module, a filtering extraction module, a synchronous adjustment module, a correction module, a differential detection module and a differential decoding module which are connected in sequence; the orthogonal demodulation module is used for carrying out orthogonal demodulation on GMSK signals acquired from the analog-to-digital converter; the filtering and extracting module is used for respectively carrying out multistage HB filtering and extraction on the two signals obtained after orthogonal demodulation and Gaussian filtering to obtain an I branch signal and a Q branch signal, wherein the bandwidth BT 'adopted in the Gaussian filtering is different from the BT adopted in the GSMK signal generation, and the BT' ═ BT (1+ x), wherein x is a numerical value larger than 0, and the size of x is determined according to the size of frequency offset; the synchronous adjusting module is used for respectively carrying out bit synchronous adjustment on the I branch signal and the Q branch signal, completing extraction and obtaining a plurality of optimal sampling points; the correction module is used for measuring and correcting frequency offset and phase offset to obtain I (k) and Q (k), wherein k is the serial number of a sampling point, and k is a positive integer greater than 1; the differential detection module is used for carrying out bit differential detection on I (k) and Q (k) respectively; and the differential decoding module is used for carrying out differential decoding on the detection result.
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