GMSK digital baseband signal coherent demodulation method and system

Abstract

The invention discloses a GMSK digital baseband signal coherent demodulation method and system, and relates to the technical field of communication signal processing, and the method comprises the steps: carrying out the correlation operation of a frame header sequence of a GMSK digital baseband signal according to a pre-coded GMSK digital baseband signal, and obtaining a signal meeting a preset demand phase; a QPSK signal is obtained by carrying out delay processing on a signal meeting a preset demand phase; performing timing error estimation on the QPSK signal, and performing symbol interpolation processing on the QPSK signal to obtain a GMSK digital baseband signal after timing synchronization; and correcting the GMSK digital baseband signal after timing synchronization according to the estimated residual phase offset of the GMSK digital baseband signal after timing synchronization, thereby obtaining a coherent demodulation output result. The waveform overhead of continuous signal segmented pilot frequency can be reduced to a great extent.

Description

Technical Field

[0001] This invention relates to the field of communication signal processing technology, and more specifically, to a GMSK digital baseband signal coherent demodulation method and system. Background Technology

[0002] Traditional GMSK demodulation methods include coherent and non-coherent demodulation. Non-coherent demodulation is insensitive to frequency and phase offsets and can achieve demodulation without precise carrier synchronization, but its demodulation performance is poor. Coherent demodulation is highly sensitive to timing and frequency / phase offsets, often relying on segmented pilots for precise timing and carrier synchronization, resulting in significant waveform overhead. Currently, there is a lack of existing technologies that can achieve coherent demodulation of GMSK digital baseband signals without segmented pilots. Summary of the Invention

[0003] The purpose of this invention is to provide a coherent demodulation method for GMSK digital baseband signals, which can overcome the shortcomings of existing segmented pilot methods with large waveform overhead.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] On the one hand, this specification provides a method for coherent demodulation of GMSK digital baseband signals, including:

[0006] Based on the pre-encoded GMSK digital baseband signal, a signal that meets the preset phase requirements is obtained by performing correlation operations on the determined frame header sequence of the GMSK digital baseband signal.

[0007] By delaying the signal that meets the preset phase requirements, a QPSK signal is reassembled.

[0008] Based on the timing error estimation result obtained by timing error estimation of the QPSK signal, symbol interpolation processing is performed on the QPSK signal to obtain the timing synchronized GMSK digital baseband signal;

[0009] By estimating the residual phase bias of the GMSK digital baseband signal after timing synchronization, and correcting the GMSK digital baseband signal after timing synchronization, the coherent demodulation output result is obtained.

[0010] On the other hand, this specification provides a GMSK digital baseband signal coherent demodulation system, comprising:

[0011] The arithmetic module is used to obtain a signal with a preset phase by performing correlation operations on the frame header sequence of the pre-encoded GMSK digital baseband signal based on the acquired pre-encoded GMSK digital baseband signal.

[0012] The assembly module is used to reassemble the QPSK signal by delaying the signal that meets the preset phase requirements;

[0013] The timing synchronization module is used to perform symbol interpolation on the QPSK signal based on the timing error estimation result obtained by timing error estimation on the QPSK signal, so as to obtain the timing synchronized GMSK digital baseband signal.

[0014] The coherent demodulation module is used to obtain the coherent demodulation output by correcting the residual phase bias of the estimated timing-synchronized GMSK digital baseband signal.

[0015] Based on the above technical solution, this specification can achieve the following technical effects:

[0016] The coherent demodulation method for GMSK digital baseband signals described above performs correlation operations on the frame header sequence of the GMSK digital baseband signal, and then estimates the timing error and residual phase offset. It can achieve timing synchronization by relying only on the frame header and the GMSK digital baseband signal, without relying on segmented pilots. It can be seen that the above method can greatly reduce the waveform overhead of segmented pilots for continuous signals. Moreover, by performing segmented correction on the timing-synchronized GMSK digital baseband signal in the above method, the demodulation reliability of burst signals can be effectively improved. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a GMSK digital baseband signal coherent demodulation method proposed in this invention.

[0018] Figure 2 This refers to the applicable frame structure proposed in this invention.

[0019] Figure 3 This is a block diagram of the GMSK digital baseband signal coherent demodulation method proposed in this invention.

[0020] Figure 4 This is a block diagram of the structure proposed in this invention for initial timing synchronization and phase pre-compensation using frame header sequences.

[0021] Figure 5 This is a block diagram of the GMSK digital baseband signal timing synchronization and carrier synchronization proposed in this invention.

[0022] Figure 6 The proposed GMSK modulation method, with a 2x oversampling rate, achieves a signal-to-noise ratio of 10dB, a sampling clock skew of 100PPM, and a frequency deviation of 3.66×10⁻⁶. -4 ×R s The constellation diagram of the symbolic interpolation result.

[0023] Figure 7 The proposed GMSK modulation method, with a 2x oversampling rate, achieves a signal-to-noise ratio of 10dB, a sampling clock skew of 100PPM, and a frequency deviation of 3.66×10⁻⁶. -4 ×R s The constellation diagram at that time, showing the phase offset correction result.

[0024] Figure 8 The proposed GMSK modulation method, with a 2x oversampling rate, achieves a signal-to-noise ratio of 10dB, a sampling clock skew of 100PPM, and a frequency deviation of 3.66×10⁻⁶. -4 ×R s At that time, the constellation diagrams of the symbol interpolation results and the phase offset correction results during the loop locking process are compared.

[0025] Figure 9 The proposed GMSK modulation method, with a 2x oversampling rate, achieves a signal-to-noise ratio of 10dB, a sampling clock skew of 100PPM, and a frequency deviation of 3.66×10⁻⁶. -4 ×R s At that time, the final demodulation result is a constellation chart.

[0026] Figure 10 The proposed GMSK modulation method, with a 2x oversampling rate, achieves a signal-to-noise ratio of 10dB, a sampling clock skew of 100PPM, and a frequency deviation of 3.66×10⁻⁶. -4 ×R s The bit error rate at different signal-to-noise ratios was calculated and compared with the theoretical value.

[0027] Figure 11 This is a schematic diagram of a GMSK digital baseband signal coherent demodulation system according to an embodiment of the present invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and are not to a precise scale, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0029] It should be noted that, in order to clearly illustrate the content of this invention, several embodiments are provided to further explain different implementations of the invention. These embodiments are enumerated rather than exhaustive. Furthermore, for the sake of brevity, content mentioned in the preceding embodiments is often omitted in the following embodiments. Therefore, content not mentioned in the later embodiments can be referred to in the preceding embodiments.

[0030] Please refer to Figures 1 to 10 One embodiment of this specification provides a method for coherent demodulation of GMSK digital baseband signals, comprising:

[0031] Step 102: Based on the acquired pre-encoded GMSK digital baseband signal, perform correlation operations on the determined frame header sequence of the GMSK digital baseband signal to obtain a signal that meets the preset phase requirements.

[0032] Step 104: By delaying the signal that meets the preset phase requirements, the signal is reassembled into a QPSK signal;

[0033] Step 106: Based on the timing error estimation result obtained by timing error estimation of the QPSK signal, perform symbol interpolation on the QPSK signal to obtain the timing-synchronized GMSK digital baseband signal;

[0034] Step 108: Using the estimated residual phase bias of the timing-synchronized GMSK digital baseband signal, the coherent demodulation output is obtained by correcting the timing-synchronized GMSK digital baseband signal.

[0035] Specifically, the above method performs correlation operations on the frame header sequence of the GMSK digital baseband signal, and then performs timing error estimation and residual phase offset estimation. Timing synchronization can be achieved solely by the frame header and the GMSK digital baseband signal, without relying on segmented pilots. It is evident that the above method can greatly reduce the waveform overhead of segmented pilots for continuous signals. Moreover, by performing segmented correction on the timing-synchronized GMSK digital baseband signal using the above method, the demodulation reliability of burst signals can be effectively improved.

[0036] In this embodiment, before step 102, the following steps are also included:

[0037] Step 112: Receive GMSK digital baseband signal;

[0038] Step 114: Determine the frame header sequence of the GMSK digital baseband signal;

[0039] Step 116: Perform pre-coding processing on the GMSK digital baseband signal.

[0040] In this embodiment, the signal rate of the GMSK digital baseband signal is R. s For detailed frame structure, please refer to Figure 2 The frame header contains known information, and the data contains information to be demodulated. The frame header and data participate in GMSK modulation together. The sampling rate of the GMSK digital baseband signal is 2R. s That is, the oversampling rate is 2, the sampling clock offset is 100 PPM, and the frequency offset is 3.66 × 10⁻⁶. -4 ×R s B b T b The value is 0.5.

[0041] In this embodiment, the GMSK digital baseband signal can be obtained by sampling through an ADC module.

[0042] In this embodiment, the precoding method described above is detailed as follows:

[0043] The linear approximation of the GMSK digital baseband signal is not only related to the current data symbol a i It is related to other symbols as well. To avoid the influence of other symbols, precoding is performed before transmission, as follows:

[0044]

[0045] Among them, a -1 =0, a i ∈{0,1} is the original code element, b i ∈{0,1} represents the code elements after precoding. This is the XOR operation, and ~ is the NOT operation. In GMSK modulation, 0 is mapped to 1, and 1 is mapped to -1.

[0046] After precoding, a0, a2, a4, ... are mapped to the Q-path, with 0 mapped to 1j and 1 mapped to -1j; a1, a3, a5, ... are mapped to the I-path, with 0 mapped to 1 and 1 mapped to -1.

[0047] In this embodiment, the GMSK digital baseband signal after the above precoding process is input to a matched filter, and noise interference can be effectively filtered out after filtering. The first-order coefficients after Laurent decomposition are used as the coefficients of the matched filter, as detailed below:

[0048] C0(t)=sinψ(t)×sinψ(t+T b )×sinψ(t+2T b )×sinψ(t+3T b )×sinψ(t+4T b )

[0049] Among them, T b For the duration of each transmitted bit, the Gaussian filter truncation length is 5T. b ,

[0050] In the formula:

[0051]

[0052] Where Q(·) is the right-tail function of the standard normal distribution, and B b t represents the bandwidth of the Gaussian filter, and t is the time variable.

[0053] In this embodiment, Bb T b =0.5, under 2x oversampling, the matched filter coefficients are [0.0045, 0.0970, 0.4711, 0.8751, 0.8751, 0.4711, 0.0970, 0.0045].

[0054] In this embodiment, one implementation of step 102 is as follows:

[0055] Step 122: Determine the receiver's local frame header sequence;

[0056] Step 124: Perform correlation operations on the frame header sequence of the GMSK digital baseband signal and the local frame header sequence to obtain the correlation result;

[0057] Step 126: Determine the preset threshold;

[0058] Step 128: Determine whether the relevant result exceeds the preset threshold and is a maximum value;

[0059] Step 130: If yes, then determine the position corresponding to the relevant result as the starting position of the frame header sequence of the GMSK digital baseband signal;

[0060] Step 132: Determine the initial phase offset estimate based on the correlation results corresponding to the starting position of the frame header sequence of the GMSK digital baseband signal;

[0061] Step 134: Using the initial phase offset estimate, compensate the starting position of the frame header sequence of the GMSK digital baseband signal and the subsequent pre-coded GMSK digital baseband signal to obtain the signal that meets the preset phase requirements.

[0062] In this embodiment, the frame header sequence of the GMSK digital baseband signal is taken as r(n), and the local frame header sequence is taken as h(n). The relevant results are as follows:

[0063]

[0064] Where n is the bit index corresponding to the frame header sequence, and its value range is n∈[0,N-1], and conj[h(n)] is the conjugate of the local frame header sequence h(n).

[0065] In this embodiment, the aforementioned initial phase offset estimate for:

[0066]

[0067] In this embodiment, the signal r'(n) that meets the preset phase requirement is:

[0068]

[0069] Where j is the imaginary unit of the complex number.

[0070] In this embodiment, one implementation of step 104 is as follows:

[0071] Step 142: The signal that meets the preset phase requirement consists of an I-channel signal and a Q-channel signal; the Q-channel signal is delayed by a preset number of symbols;

[0072] Step 144: Reassemble the delayed Q-channel signal and the I-channel signal into a QPSK signal.

[0073] In this embodiment, the reassembled QPSK signal can be:

[0074] x(t)=Q(t)+1j×I(t+T) b )

[0075] In this embodiment, when the Q-channel signal is specifically delayed by 1 symbol, i.e., 2 sampling points, the reassembled QPSK signal can be:

[0076] x(n) = Q(n) + 1 / j × I(n+2)

[0077] In this embodiment, combined with the precoding method, the effective information of the 0th, 2nd, 4th, ... symbols is in the Q channel, and the effective information of the 1st, 3rd, 5th, ... symbols is in the I channel. It can be seen that the effective information of the GMSK digital baseband signal can be effectively extracted by the above reassembly method.

[0078] In this embodiment, one implementation of step 106 is as follows:

[0079] Step 152: Segment the QPSK signal;

[0080] Step 154: Using the OM timing error estimation algorithm, the timing error of each signal segment is estimated to obtain the timing error estimation result of the QPSK signal.

[0081] Step 156: Based on the timing error estimation result, perform symbol interpolation on the QPSK signal to obtain the timing-synchronized GMSK digital baseband signal.

[0082] By using the above method, real-time timing error correction is performed on each signal segment, providing reliable demodulation results without waiting for loop locking, which greatly improves the demodulation reliability of burst signals.

[0083] In this embodiment, each segment consists of 512 symbols, and the timing error within a segment is considered to be a fixed value.

[0084] In this embodiment, the timing error is estimated using the OM algorithm, namely:

[0085] x k =|x'(n)| 2

[0086]

[0087] x'(n) is a baseband complex signal, which is a QPSK signal oversampled by 4 times. k X is the square of the modulus of the k-th baseband complex signal. m For a segment x k After Fourier transform, take the spectral line corresponding to the sign rate. By X m The angle is obtained. This is the result of timing error estimation.

[0088] In this embodiment, the existing sampled signals of the baseband complex signal are y(0), y(1), y(2), y(3), y(4), y(5), y(6), y(7)... The sampling points can be adjusted according to the timing error estimation results so that the optimal sampling points are between y(1) and y(2), between y(5) and y(6), and so on. At the same time, the normalized timing deviation μ∈[0,1) can be obtained according to the timing error estimation results.

[0089] In this embodiment, the timing-synchronized GMSK digital baseband signal y is obtained by Farrow cubic interpolation. op (n):

[0090] y op (n)=c -1 y(4n)+c0y(4n+1)+c1y(4n+2)+c2y(4n+3)

[0091] In the formula:

[0092]

[0093] In this embodiment, at a signal-to-noise ratio of 10dB, the constellation diagram of the GMSK digital baseband signal after timing synchronization is as follows: Figure 6 As shown, it can be seen that the original code element 'a' can now be distinguished relatively accurately. i ∈{0,1}.

[0094] In this embodiment, one implementation of step 108 is as follows:

[0095] Step 162: Rotate the phase of the even-numbered signals of the GMSK digital baseband signal after timing synchronization by a specific angle;

[0096] Step 164: Combine the even-numbered signals rotated by a specific angle with the odd-numbered signals of the GMSK digital baseband signal after timing synchronization to form a new signal;

[0097] Step 166: Obtain residual phase bias by demodulating the new signal.

[0098] Specifically, the GMSK digital baseband signal y after timing synchronization op (0), y op (2) y op (4) ... phase rotation π / 2, y op (1) y op (3) y op (5) ...remain unchanged, that is:

[0099]

[0100] GMSK digital baseband signal y after timing synchronization op (0), y op (2) y op (4) ...the effective information is in path Q, y op (1) y op (3) y op (5) ...the valid information is in path I, then according to A new signal y can be obtained bpsk (n):

[0101]

[0102] For y bpsk (n) Perform a square operation to remove the modulation information, then take its angle to obtain the residual phase offset θ. k That is:

[0103]

[0104] In this embodiment, after squared demodulation, a specific number of symbols (preferably 128 symbols) are accumulated, which can effectively improve the reliability of residual phase bias under low signal-to-noise ratio.

[0105] In this embodiment, one implementation of step 108 is as follows:

[0106] Step 172: Based on the residual phase offset, perform phase offset correction on the GMSK digital baseband signal after timing synchronization to obtain the correction result;

[0107] Step 174: By performing Q / I alternating sampling on the correction result, a coherent demodulation output result is obtained.

[0108] In this embodiment, the above correction result y out (n) is:

[0109]

[0110] By using the phase bias correction method described above, it can be ensured that regardless of whether the phase-locked loop (PLL) is locked (i.e., whether the loop filter that inputs the residual phase bias is locked), the input used to calculate the coherent demodulation result will be free of phase bias. Specifically, once the PLL is stably locked, the residual phase bias θ... k =0, the GMSK digital baseband signal after timing synchronization has no phase offset. During the phase-locked loop locking process, the residual phase offset θ k ≠0. The GMSK digital baseband signal after timing synchronization has phase bias. However, by using the above correction method, the input used to calculate the coherent demodulation result can always be free of phase bias.

[0111] In this embodiment, the coherent demodulation output result output(n) is:

[0112]

[0113] In this embodiment, the imaginary parts of even-numbered signals are taken, and the real parts of odd-numbered signals are taken, which is the final demodulation result. Simulation results at a signal-to-noise ratio of 10dB can be found by referring to... Figure 9 .

[0114] Please refer to Figure 10 The above method achieves a bit error rate close to the theoretical value when SNR≥2dB, with extremely low performance loss.

[0115] In this embodiment, the following steps are included after step 166:

[0116] Step 182: Perform loop filtering on the residual phase bias to obtain the frequency control word;

[0117] Step 184: Generate a local carrier based on the frequency control word;

[0118] Step 186: Update the initial phase offset estimate with the local carrier to correct the frequency and phase offset of the next segment of the signal.

[0119] In this embodiment, the following steps are included after step 182:

[0120] Step 192: Determine the parameters of the digital oscillator for the current segment signal;

[0121] Step 194: Determine the parameters of the digital oscillator for the next segment of the signal based on the frequency control word and the parameters of the digital oscillator for the current segment of the signal. The parameters of the digital oscillator for the next segment of the signal are used to generate the local carrier.

[0122] In this embodiment, a first-order loop filter is used to form a second-order phase-locked loop, and the frequency control word FCW of the k-th segment signal is used. kfor:

[0123] FCW k =FCW k-1 +c0·(θ k -θ k-1 )+c1·θ k

[0124] Among them, FCW -1 =0, θ -1 =0, c0=2 -10 c1 = 2 -20 .

[0125] In this embodiment, the local carrier phase of the k-th signal k for:

[0126] phase k =nco k -2π×FCW k ×(0:255)

[0127] nco k+1 =nco k -2π×FCW k ×256

[0128] Among them, nco k These are the parameters of the digital oscillator for the k-th segment of the signal, which are also the parameters of the digital oscillator for the current segment of the signal.

[0129] In this embodiment, the above-mentioned phase k Used to update the initial phase offset estimate in order to correct the spectral phase offset of the next segment of the signal.

[0130] In this embodiment, the phase-locked loop update period is 128 symbols, or 256 sampling points; therefore, each local carrier segment has 256 sampling points. To ensure the phase continuity of the local carrier, the variable nco is introduced. k .

[0131] In this embodiment, the precoded GMSK digital baseband signal is multiplied by the local carrier to perform digital frequency conversion processing on the precoded GMSK digital baseband signal. The frequency and phase offset of the precoded GMSK digital baseband signal after digital frequency conversion processing are eliminated and used for timing deviation estimation and symbol interpolation recovery in steps 154 to 156.

[0132] Please refer to Figure 11 Another embodiment of this specification provides a GMSK digital baseband signal coherent demodulation system, comprising:

[0133] The arithmetic module 202 is used to obtain a signal with a preset phase requirement by performing correlation operations on the frame header sequence of the pre-encoded GMSK digital baseband signal based on the acquired pre-encoded GMSK digital baseband signal.

[0134] The assembly module 204 is used to reassemble the QPSK signal by delaying the signal that meets the preset phase requirements.

[0135] The timing synchronization module 206 is used to perform symbol interpolation processing on the QPSK signal based on the timing error estimation result obtained by timing error estimation of the QPSK signal, so as to obtain the timing synchronized GMSK digital baseband signal.

[0136] The coherent demodulation module 208 is used to obtain the coherent demodulation output result by correcting the residual phase bias of the estimated timing-synchronized GMSK digital baseband signal.

[0137] Specifically, the above method performs correlation operations on the frame header sequence of the GMSK digital baseband signal, and then performs timing error estimation and residual phase offset estimation. Timing synchronization can be achieved solely by the frame header and the GMSK digital baseband signal, without relying on segmented pilots. It is evident that the above method can greatly reduce the waveform overhead of segmented pilots for continuous signals. Moreover, by performing segmented correction on the timing-synchronized GMSK digital baseband signal using the above method, the demodulation reliability of burst signals can be effectively improved.

[0138] The processing module 202 is used to receive GMSK digital baseband signals; determine the frame header sequence of the GMSK digital baseband signals; and perform precoding processing on the GMSK digital baseband signals. It determines the receiver's local frame header sequence; performs correlation operations on the frame header sequence of the GMSK digital baseband signals and the local frame header sequence to obtain a correlation result; determines a preset threshold; determines whether the correlation result exceeds the preset threshold and is a maximum value; if so, it determines the position corresponding to the correlation result as the starting position of the frame header sequence of the GMSK digital baseband signals; determines an initial phase offset estimate based on the correlation result corresponding to the starting position of the frame header sequence of the GMSK digital baseband signals; and uses the initial phase offset estimate to compensate the starting position of the frame header sequence of the GMSK digital baseband signals and the subsequent precoded GMSK digital baseband signals to obtain a signal that meets the preset phase requirements.

[0139] The assembly module 204 is used to assemble the signal that meets the preset phase requirements, which consists of an I-channel signal and a Q-channel signal; delay the Q-channel signal by a preset number of symbols; and reassemble the delayed Q-channel signal with the I-channel signal to form a QPSK signal.

[0140] The timing synchronization module 206 is used to segment the QPSK signal; by using the OM timing error estimation algorithm, the timing error of each segment of the signal is estimated to obtain the timing error estimation result of the QPSK signal; based on the timing error estimation result, the QPSK signal is subjected to symbol interpolation to obtain the timing synchronized GMSK digital baseband signal.

[0141] The coherent demodulation module 208 is used to rotate the phase of the even-numbered signals of the timing-synchronized GMSK digital baseband signal by a specific angle; to reconstruct a new signal using the even-numbered signals rotated by a specific angle and the odd-numbered signals of the timing-synchronized GMSK digital baseband signal; and to obtain a residual phase offset by demodulating the new signal. Based on the residual phase offset, the timing-synchronized GMSK digital baseband signal is phase-biased to obtain a correction result; and the correction result is obtained by Q / I alternating sampling to obtain a coherent demodulation output result. The residual phase offset is subjected to loop filtering to obtain a frequency control word; a local carrier is generated based on the frequency control word; and the initial phase offset estimate is updated with the local carrier to correct the frequency and phase offset of the next signal segment. The parameters of the digital oscillator for the current signal segment are determined; and the parameters of the digital oscillator for the next signal segment are determined based on the frequency control word and the parameters of the digital oscillator for the current signal segment, and the parameters of the digital oscillator for the next signal segment are used to generate the local carrier.

[0142] Another embodiment of this specification provides an electronic device including a processor, an internal bus, a network interface, memory, and non-volatile memory, and may also include other hardware required for business operations. The processor reads the corresponding computer program from the non-volatile memory into memory and then runs it, forming a GMSK digital baseband signal coherent demodulation method at the logical level. Of course, in addition to software implementation, this specification does not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc., that is, the execution subject of the following processing flow is not limited to individual logic units, but can also be hardware or logic devices.

[0143] Network interfaces, processors, and memory can be interconnected via a bus system. These buses can be categorized as address buses, data buses, control buses, etc.

[0144] Memory is used to store programs. Specifically, programs may include program code, which includes computer operation instructions. Memory may include read-only memory and random access memory, and provides instructions and data to the processor.

[0145] The processor is used to execute the program stored in the aforementioned memory, and specifically perform the following:

[0146] A processor may be an integrated circuit chip with signal processing capabilities. In implementation, the steps of the above method can be completed through the processor's integrated hardware logic circuits or software instructions.

[0147] Based on the same invention, embodiments of this specification also provide a computer-readable storage medium that stores one or more programs, which, when executed by an electronic device including multiple applications, cause the electronic device to perform... Figure 1 A corresponding embodiment provides a method for coherent demodulation of GMSK digital baseband signals.

[0148] Those skilled in the art will understand that the embodiments of this specification can be provided as methods, systems, or computer program products. Therefore, this specification may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this specification may take the form of a computer program product embodied on one or more computer-readable storage media containing computer-usable program code.

[0149] Furthermore, the specific implementation of the above system is basically similar to the method implementation, so the description is relatively simple. For relevant details, please refer to the description of the method implementation. Moreover, it should be noted that in the various modules of the system of this application, the components are logically divided according to the functions they are to perform. However, this application is not limited to this and can re-divide or combine the components as needed.

[0150] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences between it and other embodiments.

[0151] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than those shown in the embodiments and still achieve the desired result. Furthermore, the specific order or sequential order shown in the drawings is not necessarily required to achieve the desired result; in some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0152] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method for coherent demodulation of GMSK digital baseband signals, characterized in that, include: Based on the pre-encoded GMSK digital baseband signal, a signal that meets the preset phase requirements is obtained by performing correlation operations on the determined frame header sequence of the GMSK digital baseband signal. By delaying the signal that meets the preset phase requirements, a QPSK signal is reassembled. Based on the timing error estimation result obtained by timing error estimation of the QPSK signal, symbol interpolation processing is performed on the QPSK signal to obtain the timing synchronized GMSK digital baseband signal; By estimating the residual phase bias of the GMSK digital baseband signal after timing synchronization, and correcting the GMSK digital baseband signal after timing synchronization, the coherent demodulation output result is obtained.

2. The GMSK digital baseband signal coherent demodulation method according to claim 1, characterized in that, Before obtaining a signal with a preset phase requirement by performing correlation operations on the determined frame header sequence of the pre-encoded GMSK digital baseband signal based on the acquired pre-encoded GMSK digital baseband signal, the process includes: Receive GMSK digital baseband signals; Determine the frame header sequence of the GMSK digital baseband signal; The GMSK digital baseband signal is pre-encoded.

3. The GMSK digital baseband signal coherent demodulation method according to claim 2, characterized in that, The step of obtaining a signal with a preset phase requirement by performing correlation operations on the frame header sequence of the pre-encoded GMSK digital baseband signal based on the acquired pre-encoded GMSK digital baseband signal includes: Determine the receiver's local frame header sequence; The frame header sequence of the GMSK digital baseband signal and the local frame header sequence are correlated to obtain the correlation result; Determine the preset threshold; Determine whether the relevant result exceeds the preset threshold and is a maximum value; If so, then the position corresponding to the relevant result is determined to be the starting position of the frame header sequence of the GMSK digital baseband signal; The initial phase offset estimate is determined based on the correlation results corresponding to the starting position of the frame header sequence of the GMSK digital baseband signal. Using the initial phase offset estimate, the starting position of the frame header sequence of the GMSK digital baseband signal and the subsequent pre-coded GMSK digital baseband signal are compensated to obtain the signal that meets the preset phase requirements.

4. The GMSK digital baseband signal coherent demodulation method according to claim 1, characterized in that, The step of delaying the signal that meets the preset phase requirement and reassembling it into a QPSK signal includes: The signal that meets the preset phase requirements consists of an I-channel signal and a Q-channel signal; The Q-channel signal is delayed by a preset number of symbols; The delayed Q-channel signal and the I-channel signal are reassembled into a QPSK signal.

5. The GMSK digital baseband signal coherent demodulation method according to claim 3, characterized in that, The step of performing symbol interpolation on the QPSK signal based on the timing error estimation result obtained by timing error estimation on the QPSK signal to obtain the timing-synchronized GMSK digital baseband signal includes: Segment the QPSK signal; The timing error estimation results of the QPSK signal are obtained by estimating the timing error of each signal segment using the OM timing error estimation algorithm. Based on the timing error estimation result, the QPSK signal is subjected to symbol interpolation to obtain the timing-synchronized GMSK digital baseband signal.

6. The GMSK digital baseband signal coherent demodulation method according to claim 1, characterized in that, The estimated residual phase offset of the timing-synchronized GMSK digital baseband signal includes: Rotate the phase of the even-numbered signals of the GMSK digital baseband signal after timing synchronization by a specific angle; The even-numbered signals rotated by a specific angle are combined with the odd-numbered signals of the GMSK digital baseband signal after timing synchronization to form a new signal; By performing demodulation processing on the new signal, residual phase bias is obtained.

7. The GMSK digital baseband signal coherent demodulation method according to claim 6, characterized in that, The residual phase bias of the estimated time-synchronized GMSK digital baseband signal is used to correct the time-synchronized GMSK digital baseband signal to obtain the coherent demodulation output result, including: Based on the residual phase offset, the phase offset correction is performed on the timing-synchronized GMSK digital baseband signal to obtain the correction result; By performing Q / I alternating sampling on the correction results, coherent demodulation output results are obtained.

8. The GMSK digital baseband signal coherent demodulation method according to claim 5, characterized in that, After the residual phase offset of the estimated timing-synchronized GMSK digital baseband signal, the following is included: The residual phase bias is subjected to loop filtering to obtain the frequency control word; A local carrier is generated based on the frequency control word; The initial phase offset estimate is updated with the local carrier to correct the frequency and phase offset of the next segment of the signal.

9. The GMSK digital baseband signal coherent demodulation method according to claim 8, characterized in that, After performing loop filtering on the residual phase offset to obtain the frequency control word, the process includes: Determine the parameters of the digital oscillator for the current segment of the signal; Based on the frequency control word and the parameters of the digital oscillator of the current segment signal, the parameters of the digital oscillator of the next segment signal are determined, and the parameters of the digital oscillator of the next segment signal are used to generate the local carrier.

10. A GMSK digital baseband signal coherent demodulation system, characterized in that, include: The arithmetic module is used to obtain a signal with a preset phase requirement by performing correlation operations on the frame header sequence of the pre-encoded GMSK digital baseband signal based on the acquired pre-encoded GMSK digital baseband signal. The assembly module is used to reassemble the QPSK signal by delaying the signal that meets the preset phase requirements; The timing synchronization module is used to perform symbol interpolation on the QPSK signal based on the timing error estimation result obtained by timing error estimation on the QPSK signal, so as to obtain the timing synchronized GMSK digital baseband signal. The coherent demodulation module is used to obtain the coherent demodulation output by correcting the residual phase bias of the estimated timing-synchronized GMSK digital baseband signal.

Images