CN114285435B - Method, device, equipment and medium for correcting frequency offset of spread spectrum communication - Google Patents

Abstract

The invention discloses a spread spectrum communication frequency offset correction method, device, equipment and medium, which includes: receiving spread spectrum signals; setting the first frequency for iteration according to the tuning value; in each iteration, setting a numerically controlled oscillator The frequency is the current first frequency. Verify the despread binary bit sequence corresponding to the current first frequency and the original binary bit sequence. If the verification fails, obtain the current second frequency based on the current first frequency and set the numerically controlled oscillator. The frequency is the current second frequency. Verify the despread binary bit sequence corresponding to the current second frequency and the original binary bit sequence. If the verification fails, set the frequency of the numerically controlled oscillator to the first frequency of the next iteration, Until the verification of the despread binary bit sequence and the original binary bit sequence is successful, the current frequency of the numerically controlled oscillator is the frequency offset. The invention ensures that the correct frequency offset between the receiving end and the transmitting end is searched within the entire maximum frequency offset range between the receiving end and the transmitting end.

Description

A spread spectrum communication frequency offset correction method, device, equipment and medium

Technical field

The invention belongs to the technical field of spread spectrum communication, and specifically relates to a spread spectrum communication frequency offset correction method, device, equipment and medium.

Background technique

Spread spectrum communication (spread spectrum communication for short) technology has noise-like concealment, strong anti-interference properties, and good confidentiality. It is widely used in military communications and modern civilian communications. Spread spectrum communication includes direct sequence spread spectrum, frequency hopping, time hopping spread spectrum and linear frequency modulation. In the point-to-point communication scenario using direct sequence spread spectrum technology, the inconsistency of the reference clock of the communication equipment will be between the transmitter and the receiver. Introducing carrier frequency offset (referred to as frequency offset), if the frequency offset is large, it will directly affect the demodulation recovery of the signal at the receiving end.

When demodulating and recovering signals, a feedback control loop is usually used to correct frequency offset and phase difference. The feedback control loop includes phase detectors, loop filters, and numerically controlled oscillators. However, the feedback control loop can be directly The captured frequency offset range is limited by the bit rate R of the signal: taking BPSK (Binary Phase Shift Keying, binary phase shift keying) modulation as an example, the maximum frequency offset range that the feedback control loop can directly capture under an ideal signal-to-noise ratio is [-R/4,+R/4]; Taking QPSK (Quadrature Phase Shift Keying) modulation as an example, the maximum frequency offset range that the feedback control loop can directly capture under an ideal signal-to-noise ratio is [ -R/8,+R/8]. When the bit rate R and signal-to-noise ratio of the signal are low, the carrier frequency offset between the receiving end and the transmitting end during the actual communication process will exceed the maximum frequency offset range that the feedback control loop can directly capture. At this time, the feedback control loop Correction of carrier frequency offset cannot be achieved.

Contents of the invention

Purpose of the invention: In view of the problems existing in the prior art, the present invention discloses a spread spectrum communication frequency offset correction method, device, equipment and medium, which solves the problem of frequency offset that exceeds the maximum frequency offset range that the feedback control loop can directly capture. Problems that cannot be corrected expand the correctable frequency offset range.

Technical solution: In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solution:

A spread spectrum communication frequency offset correction method includes the following steps:

Receive a spread spectrum signal, which is obtained by calculating the original binary bit sequence sent by the transmitter and the spread spectrum sequence;

The minimum frequency offset is used as the initial value of the first frequency, and the first frequency is iterated according to the tuning value within the frequency offset range;

In each iteration, the current first frequency is used as the current frequency of the numerically controlled oscillator, a despread binary bit sequence corresponding to the current first frequency is obtained, and the despread binary bit sequence corresponding to the current first frequency is verified with Raw binary bit sequence;

If the verification is successful, the current frequency of the numerically controlled oscillator is frequency offset;

If the verification fails, obtain the current second frequency based on the current first frequency, use the current second frequency as the current frequency of the numerically controlled oscillator, obtain the despread binary bit sequence corresponding to the current second frequency, and verify that the current second frequency corresponds to the current second frequency. The despread binary bit sequence of the two frequencies and the original binary bit sequence. If the verification is successful, the current frequency of the numerically controlled oscillator is the frequency offset; if the verification fails, the first frequency of the next iteration is used as the numerically controlled oscillator. The current frequency, the first frequency of the next iteration is calculated according to the current first frequency and tuning value; repeat the above iteration process until the verification of the despread binary bit sequence and the original binary bit sequence is successful, the numerically controlled oscillator The current frequency of is the frequency offset;

The frequency offset is used as the frequency of a numerically controlled oscillator, and the frequency offset of the subsequently received spread spectrum signal is corrected by the numerically controlled oscillator.

Further, the tuning value is calculated based on the maximum frequency offset range that the feedback control loop can capture under an ideal signal-to-noise ratio, the maximum signal-to-noise ratio, and the current signal-to-noise ratio.

Further, the tuning value f _tune is:

Among them, W is the interval length of the maximum frequency offset range that the feedback control loop can capture under the ideal signal-to-noise ratio, SNR _max is the maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio, and α is the empirical value.

Further, the current first frequency is added to the tuning value to obtain the first frequency of the next iteration.

Further, obtaining the current second frequency based on the current first frequency includes:

The spread spectrum signal is sequentially operated with a numerically controlled oscillator and a spread spectrum sequence to obtain a despread signal;

In the despread signal, one correlation peak is detected for each fixed sequence length, the fixed sequence length is the sequence length of the spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;

The rotation angle between the coordinate points corresponding to adjacent correlation peaks is obtained according to the I signal value and Q signal value of each correlation peak position;

Obtain the correction frequency according to the rotation angle between the coordinate points corresponding to the adjacent correlation peaks;

The current second frequency is obtained according to the correction frequency and the current first frequency.

Further, the rotation angle between the coordinate points corresponding to the adjacent correlation peaks is:

Among them, θ(k) is the rotation angle between the coordinate point corresponding to the k+1-th correlation peak and the coordinate point corresponding to the k-th correlation peak, I _xcorr (k) and Q _xcorr (k) are the k-th correlation peak respectively. The I signal value and Q signal value of the correlation peak, I _xcorr (k+1) and Q _xcorr (k+1) are the I signal value and Q signal value of the k+1th correlation peak respectively, K is Number of relevant peaks;

The correction frequency f _{guess_ave} is:

Among them, R is the bit rate;

The current second frequency for:

in, is the current first frequency, and l represents the number of iterations.

Further, the I-channel signal value and Q-channel signal value at each correlation peak position are represented by signed numbers, and each signal value is determined based on the sign bit of the I-channel signal value and the Q-channel signal value at each correlation peak position. Binary data corresponding to the despread signal of a fixed sequence length, and the binary data corresponding to the despread signal of each fixed sequence length are sequentially combined to obtain a despread binary bit sequence.

Further, the original binary bit sequence includes characteristic bit sequence information, and the despread binary bit sequence includes characteristic bit sequence information. If the characteristic bit sequence information of the original binary bit sequence is the same as the characteristic bit sequence of the despread binary bit sequence, If the information matches, the despread binary bit sequence and the original binary bit sequence are successfully verified.

Further, the original binary bit sequence and the deexpanded binary bit sequence are represented by data frames. Each data frame includes several bytes. The byte at a fixed position in front of each data frame is defined as a feature bit, and the binary data corresponding to the feature bit is the characteristic bit sequence information.

A spread spectrum communication frequency offset correction device, including:

A signal receiving module, configured to receive a spread spectrum signal, which is obtained by calculating the original binary bit sequence sent by the transmitter and the spread spectrum sequence;

An iteration module, used to use the minimum frequency offset as the initial value of the first frequency, and the first frequency is iterated according to the tuning value within the frequency offset range;

In each iteration, the current first frequency is used as the current frequency of the numerically controlled oscillator, a despread binary bit sequence corresponding to the current first frequency is obtained, and the despread binary bit sequence corresponding to the current first frequency is verified with The original binary bit sequence; if the verification is successful, the current frequency of the numerically controlled oscillator is the frequency offset; if the verification fails, the current second frequency is obtained based on the current first frequency, and the current second frequency is used as the current frequency of the numerically controlled oscillator. frequency, obtain the despread binary bit sequence corresponding to the current second frequency, and verify the despread binary bit sequence corresponding to the current second frequency and the original binary bit sequence. If the verification is successful, then the numerically controlled oscillator The current frequency is the frequency offset; if the verification fails, the first frequency of the next iteration is used as the current frequency of the CNC oscillator, and the first frequency of the next iteration is calculated based on the current first frequency and the tuning value; repeat the above iteration process, until the verification of the despread binary bit sequence and the original binary bit sequence is successful, the current frequency of the numerically controlled oscillator is the frequency offset;

A frequency offset correction module is used to use the frequency offset as the frequency of a numerically controlled oscillator, and use the numerically controlled oscillator to correct the frequency offset of subsequently received spread spectrum signals.

A spread spectrum communication frequency offset correction device, including a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the program, any one of the aforementioned spread spectrum is realized. Communication frequency offset correction method.

A computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to execute any one of the aforementioned spread spectrum communication frequency offset correction methods.

Beneficial effects: Compared with the existing technology, the present invention has the following beneficial effects:

The present invention sets the first frequency iteratively according to the tuning value within the maximum frequency offset range, taking the minimum frequency offset as the initial value, and verifies the despread binary bit sequence obtained according to the first frequency. If the verification fails, then Correct the first frequency to the second frequency, and verify the despread binary bit sequence obtained based on the second frequency. If the verification fails, verify the despread binary bit sequence obtained based on the first frequency of the next iteration, Repeating the above process can ensure that the correct frequency offset between the receiving end and the transmitting end is searched within the entire maximum frequency offset range between the receiving end and the transmitting end.

Description of the drawings

Figure 1 is a flow chart of the frequency offset correction method according to Embodiment 1 of the present invention;

Figure 2 is an overall block diagram of the frequency offset correction method according to Embodiment 2 of the present invention;

Figure 3 is a specific block diagram of the receiving end frequency offset correction method according to Embodiment 2 of the present invention;

Figure 4 is a waveform diagram of the original binary bit sequence at the transmitting end and the signal after spread spectrum modulation according to Embodiment 2 of the present invention;

Figure 5 is a structural diagram of a data frame sent by the sending end according to Embodiment 2 of the present invention;

Figure 6 is a phase rotation diagram of I/Q data on a constellation diagram at two adjacent correlation peak positions at the receiving end according to Embodiment 2 of the present invention;

FIG. 7 is a structural diagram of a frequency offset correction device according to Embodiment 4 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

Example 1:

This embodiment discloses a spread spectrum communication frequency offset correction method, as shown in Figure 1, including the following steps:

Receive a spread spectrum signal, which is obtained by calculating the original binary bit sequence sent by the transmitter and the spread spectrum sequence;

The minimum frequency offset is used as the initial value of the first frequency, and the first frequency is iterated according to the tuning value within the frequency offset range;

In each iteration, the current first frequency is used as the current frequency of the numerically controlled oscillator, a despread binary bit sequence corresponding to the current first frequency is obtained, and the despread binary bit sequence corresponding to the current first frequency is verified with Raw binary bit sequence;

If the verification is successful, the current frequency of the numerically controlled oscillator is frequency offset;

If the verification fails, obtain the current second frequency based on the current first frequency, use the current second frequency as the current frequency of the numerically controlled oscillator, obtain the despread binary bit sequence corresponding to the current second frequency, and verify that the current second frequency corresponds to the current second frequency. The despread binary bit sequence of the two frequencies and the original binary bit sequence. If the verification is successful, the current frequency of the numerically controlled oscillator is the frequency offset; if the verification fails, the first frequency of the next iteration is used as the numerically controlled oscillator. The current frequency, the first frequency of the next iteration is calculated according to the current first frequency and tuning value; repeat the above iteration process until the verification of the despread binary bit sequence and the original binary bit sequence is successful, the numerically controlled oscillator The current frequency of is the frequency offset;

The frequency offset is used as the frequency of a numerically controlled oscillator, and the frequency offset of the subsequently received spread spectrum signal is corrected by the numerically controlled oscillator.

In this embodiment, the first frequency is set iteratively according to the tuning value within the maximum frequency offset range, with the minimum frequency offset as the initial value, and the despread binary bit sequence obtained according to the first frequency is verified. If the verification fails, Then correct the first frequency to the second frequency, and verify the despread binary bit sequence obtained based on the second frequency. If the verification fails, verify the despread binary bit sequence obtained based on the first frequency of the next iteration. , repeating the above process can ensure that the correct frequency offset between the receiving end and the transmitting end is searched within the entire maximum frequency offset range between the receiving end and the transmitting end.

In this embodiment, when the feedback control loop is used to open the loop, the gradient scan configuration frequency offset of the numerically controlled oscillator is the first frequency of the iteration, which avoids the need to adjust the intermediate frequency point of the analog part of the receiver and avoid waiting for the feedback control loop to lock. The response time of the CNC oscillator frequency is fast, and the configuration speed can be quickly implemented.

Further, the tuning value is calculated based on the maximum frequency offset range that the feedback control loop can capture under an ideal signal-to-noise ratio, the maximum signal-to-noise ratio, and the current signal-to-noise ratio.

Further, the tuning value f _tune is:

Among them, W is the interval length of the maximum frequency offset range that the feedback control loop can capture under the ideal signal-to-noise ratio, SNR _max is the maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio, and α is the empirical value.

In this embodiment, the dynamically set tuning value can be adjusted according to the real-time communication status, and is more accurate than the fixed tuning value.

Further, the current first frequency is added to the tuning value to obtain the first frequency of the next iteration.

Further, obtaining the current second frequency based on the current first frequency includes:

The spread spectrum signal is sequentially operated with a numerically controlled oscillator and a spread spectrum sequence to obtain a despread signal;

In the despread signal, one correlation peak is detected for each fixed sequence length, the fixed sequence length is the sequence length of the spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;

The rotation angle between the coordinate points corresponding to adjacent correlation peaks is obtained according to the I signal value and Q signal value of each correlation peak position;

Obtain the correction frequency according to the rotation angle between the coordinate points corresponding to the adjacent correlation peaks;

The current second frequency is obtained according to the correction frequency and the current first frequency.

Further, the rotation angle between the coordinate points corresponding to the adjacent correlation peaks is:

Among them, θ(k) is the rotation angle between the coordinate point corresponding to the k+1-th correlation peak and the coordinate point corresponding to the k-th correlation peak, I _xcorr (k) and Q _xcorr (k) are the k-th correlation peak respectively. The I signal value and Q signal value of the correlation peak, I _xcorr (k+1) and Q _xcorr (k+1) are the I signal value and Q signal value of the k+1th correlation peak respectively, K is Number of relevant peaks;

The correction frequency f _{guess_ave} is:

Among them, R is the bit rate;

The current second frequency for:

in, is the current first frequency, and l represents the number of iterations.

Further, the I-channel signal value and Q-channel signal value at each correlation peak position are represented by signed numbers, and each signal value is determined based on the sign bit of the I-channel signal value and the Q-channel signal value at each correlation peak position. Binary data corresponding to the despread signal of a fixed sequence length, and the binary data corresponding to the despread signal of each fixed sequence length are sequentially combined to obtain a despread binary bit sequence.

Further, the original binary bit sequence includes characteristic bit sequence information, and the despread binary bit sequence includes characteristic bit sequence information. If the characteristic bit sequence information of the original binary bit sequence is the same as the characteristic bit sequence of the despread binary bit sequence, If the information matches, the despread binary bit sequence and the original binary bit sequence are successfully verified.

In this embodiment, the accuracy of frequency offset estimation is ensured by using characteristic bit sequence information for verification during frequency offset estimation.

Further, the original binary bit sequence and the deexpanded binary bit sequence are represented by data frames. Each data frame includes several bytes. The byte at a fixed position in front of each data frame is defined as a feature bit, and the binary data corresponding to the feature bit is the characteristic bit sequence information.

Example 2:

This embodiment discloses a spread spectrum communication frequency offset correction method, as shown in Figure 2, including the transmitter sending a spread spectrum signal, the receiving end receiving the spread spectrum signal, frequency offset estimation and locking the numerically controlled oscillator frequency correction frequency offset to achieve the frequency The four parts of synchronization are used to expand the frequency offset correction range of the receiving end and are suitable for low signal-to-noise ratio fixed point-to-point BPSK/QPSK spread spectrum communication application scenarios.

As shown in Figure 3, the method described in this embodiment specifically includes the following steps:

Step S1: The transmitter sends a spread spectrum signal

Before the synchronous communication between the receiving end and the transmitting end is established, the transmitting end continues to send the original binary bit sequence S _T . After the original binary bit sequence S _T is operated with the spreading sequence C _PN , the spread spectrum signal X _T is obtained:

X _T =S _T C _PN

The transmitting end sends the _spread spectrum signal

In this embodiment, the sending end sends the original binary bit sequence in the form of a data frame (Frame). Each data frame includes several bytes (BYTE), and each byte includes 8 bits (Bit). For example, as shown in Figure 5, the bit rate R of the original binary bit sequence sent by the sender is 8kHz, that is, 8000 bits are sent per second. The sender sends data frames at a rate of 20 frames per second, so each data frame includes 50 bytes.

The byte at a specific position in each data frame of the original binary bit sequence is set as a signature bit, and the bit sequence information corresponding to the signature bit is the signature bit sequence information used for verification. In this embodiment, the first 2 bytes of each data frame are defined as signature bits (BYTE1 and BYTE2), and the corresponding binary data is signature bit sequence information. This embodiment uses characteristic bit sequence information for verification during frequency offset estimation to ensure the accuracy of frequency offset estimation.

Step S2: The receiving end receives the spread spectrum signal;

The minimum frequency offset is used as the initial value of the first frequency, and the first frequency is iterated according to the tuning value within the frequency offset range;

In each iteration, the current first frequency is used as the current frequency of the numerically controlled oscillator, a despread binary bit sequence corresponding to the current first frequency is obtained, and the despread binary bit sequence corresponding to the current first frequency is verified with Raw binary bit sequence;

If the verification is successful, the current frequency of the numerically controlled oscillator is frequency offset;

If the verification fails, obtain the current second frequency based on the current first frequency, use the current second frequency as the current frequency of the numerically controlled oscillator, obtain the despread binary bit sequence corresponding to the current second frequency, and verify that the current second frequency corresponds to the current second frequency. The despread binary bit sequence of the two frequencies and the original binary bit sequence. If the verification is successful, the current frequency of the numerically controlled oscillator is the frequency offset; if the verification fails, the first frequency of the next iteration is used as the numerically controlled oscillator. The current frequency, the first frequency of the next iteration is calculated according to the current first frequency and tuning value; repeat the above iteration process until the verification of the despread binary bit sequence and the original binary bit sequence is successful, the numerically controlled oscillator The current frequency of is the frequency offset;

Step S21: After the receiving end receives the signal sent by the transmitter of the transmitting end, the receiver of the receiving end performs ADC sampling on the received signal to obtain the spread spectrum signal Y _R .

At this time, since synchronous communication has not been established between the receiving end and the transmitting end, there is a frequency offset between the spread spectrum signal Y _R received by the receiving end and the spread spectrum signal X _T sent by the transmitting end, and this frequency offset may exceed the feedback The maximum frequency offset range that the control loop can directly capture, so the loop switch of the feedback control loop needs to be set to the open state, and the frequency offset is searched through the open-loop control of the numerically controlled oscillator (NCO) and the verification information. After the correct frequency offset is obtained, the frequency of the CNC oscillator is set to the searched frequency offset, and then the loop switch of the feedback control loop is set to the closed state to achieve communication synchronization.

The process of searching for frequency offset through the open-loop control of the numerically controlled oscillator (NCO) and the verification information is as follows:

Step S22: Set the frequency of the numerically controlled oscillator to the initial first frequency The initial first frequency is the minimum frequency offset between the receiving end and the transmitting end obtained through actual testing.

Taking BPSK modulation as an example, the single-tone beacon signal with frequency f _trs is directly loaded on the transmitting end. The frequency and power of the single-tone beacon signal are known; the receiving end analyzes and obtains the frequency of the single-tone beacon signal as f _rec , so it can pass the actual test. The obtained frequency offset range (f _trs -f _rec ) between the receiving end and the transmitting end is [-12kHz, +12kHz], that is, the minimum frequency offset is f _{offset_min} =-12kHz, and the maximum frequency offset is f _{offset_max} =12kHz, so Set the initial first frequency to -12kHz. The maximum signal-to-noise ratio SNR _max can also be obtained through the above measurement method of the single tone beacon signal.

Step S23: Calculate the despread binary bit sequence corresponding to the current frequency of the numerically controlled oscillator

The spread spectrum signal Y _R is passed through a numerically controlled oscillator to obtain the signal Y _R ′ to be despread.

The signal to be despread Y _R ′ performs a despread correlation operation with the spreading sequence C _PN at the transmitter to obtain the despread signal U _R . The despread correlation operation is:

Among them, N is the sequence length of the spreading sequence, that is, the number of bits contained in the spreading sequence, m and n are integers between 0 and N-1; j=0,1,...,J-1, J is The ratio of the sequence length of the signal Y _R ′ to be despread to the sequence length of the spreading sequence.

For the despread signal _UR , segment it with a fixed sequence length, that is, each segmented signal has a fixed sequence length, and the fixed sequence length is the sequence length of the spreading sequence C _PN ; detect each segmented signal _The correlation peak position _of The signal amplitude at is

According to the I signal value I _xcorr and the Q signal value Q _xcorr at the correlation peak position of each segmented signal, the calculation decision is made to obtain the despread binary bit sequence S _R corresponding to the current frequency of the CNC oscillator. The calculation decision method is as follows: use The signed number represents the I signal value I _xcorr and the Q signal value Q _xcorr at the correlation peak position of each segment signal. Each segment is obtained according to the sign bit of the I signal value I _xcorr and the Q signal value Q _xcorr . The binary data corresponding to the signal. Among them, the mapping relationship between the sign bits of the I signal value I _xcorr and the Q signal value Q _xcorr and the binary data is determined by the original binary bit sequence.

For example, in BPSK modulation, the Q signal values are all 0. Therefore, if the sign bit of the signed number representing the I signal value I _xcorr is 0, then the binary data corresponding to the segmented signal is 1. If it represents the I signal value I _xcorr The sign bit of the signed integer is 1, then the binary data corresponding to the segmented signal is 0; the binary data corresponding to each segmented signal is sequentially combined according to the position of each segmented signal in the despread signal U _R , The despread binary bit sequence S _R can be obtained.

Step S24: Verify the original binary bit sequence S _T and the despread binary bit sequence _SR corresponding to the current frequency of the digital oscillator. If the verification is successful, the current frequency of the digital oscillator is the frequency between the receiving end and the transmitting end. Offset; if the verification is unsuccessful, the current first frequency will be corrected to the second frequency.

The verification method of the original binary bit sequence S _T and the despread binary bit sequence S _R is: express the despread binary bit sequence S _R in the same data frame format as the original binary bit sequence S _T , and compare the original binary bit sequence S _T The characteristic bit sequence information in each data frame and the despread binary bit sequence S _R The characteristic bit sequence information in each data frame. If they match, the verification is successful; if there is a mismatch, the verification is unsuccessful.

Adjust the frequency of the digital oscillator to: based on the first frequency of the current l-th iteration Correct the frequency of the digital oscillator to the second frequency/> include:

As shown in Figure 6, according to the coordinate points corresponding to the I-channel signal value I _xcorr and the Q-channel signal value Q _xcorr on the constellation diagram at the position of each segmented signal correlation peak, the distance between the coordinate points corresponding to adjacent correlation peaks is calculated. The rotation angle θ(k) is:

Among them, θ(k) is the rotation angle between the coordinate point corresponding to the k+1-th correlation peak and the coordinate point corresponding to the k-th correlation peak, I _xcorr (k) and Q _xcorr (k) are the k-th correlation peak respectively. The I signal value and the Q signal value at the correlation peak position of the segmented signal, I _xcorr (k+1) and Q _xcorr (k+1) are the I signal value at the kth segment signal correlation peak position respectively. and Q signal value, K is the number of segmented signals, that is, the number of correlation peaks.

Calculate the corrected frequency offset f _{guess_ave} based on the rotation angle between the coordinate points corresponding to adjacent correlation peaks as:

Among them, R is the bit rate at which the sending end sends the original binary bit sequence.

Use the corrected frequency offset f _{guess_ave} to correct the first frequency of the current l-th iteration is the second frequency/>

Step S25: Set the frequency of the digital oscillator to the current second frequency According to the process of step S23, the despread binary bit sequence S _R corresponding to the current frequency of the numerically controlled oscillator is obtained. The original binary bit sequence _ST is verified according to the verification method described in step S24. The despread binary bit sequence S _R is verified. If the verification is successful, the current frequency of the digital oscillator is the frequency offset between the receiving end and the transmitting end; if the verification is unsuccessful, the current first frequency is adjusted to the first frequency of the next iteration.

Adjust the current first frequency to the first frequency of the next iteration: Modify the current first frequency to the first frequency of the next iteration according to the tuning value, and the tuning value f _tune is:

Among them, W is the interval length of the maximum frequency offset range that the feedback control loop can capture under the ideal signal-to-noise ratio, SNR _max is the maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio, α is the empirical value, and both W and α are related to the modulation Method related.

So the first frequency for the next iteration is:

in, is the first frequency of the current l-th iteration,/> is the first frequency of the next iteration, that is, the l+1th iteration.

For example, the signal bit rate at the transmitter is 8kHz, so the maximum frequency offset range that the feedback control loop in BPSK modulation can capture under the ideal signal-to-noise ratio is [-2kHz, +2kHz], which is actually limited by the signal-to-noise ratio SNR. Below, each tuning value is dynamically set by the signal-to-noise ratio:

Step S26: Set the frequency of the digital oscillator to the first frequency of the next iteration, and repeat steps S23 to S25 until the verification of the original binary bit sequence S _T and the despread binary bit sequence S _R are successful. At this time, the digital oscillator The current frequency is the frequency offset between the receiving end and the transmitting end.

Step 3: Use the frequency offset as the frequency of a numerically controlled oscillator, and use the numerically controlled oscillator to correct the frequency offset of the subsequently received spread spectrum signal.

After obtaining the frequency offset between the receiving end and the transmitting end, set the frequency of the numerically controlled oscillator to the frequency offset, and set the loop switch of the feedback control loop to a closed state. At this time, communication synchronization is achieved through the numerically controlled oscillator. .

After correcting the frequency offset problem between the receiving end and the transmitting end, the feedback control loop phase-locked loop is closed to correct the phase error between the receiving end and the transmitting end.

In this embodiment, the initial first frequency is set to the minimum frequency offset between the receiving end and the transmitting end obtained by actual testing, the tuning value is dynamically set according to real-time signal-to-noise ratio and other conditions, and then the tuning value is obtained based on the dynamically set tuning value. The first frequency of the next iteration, and then searching for the second frequency near the first frequency of each iteration, can ensure that the correct frequency offset is searched within the entire maximum frequency offset range between the receiving end and the transmitting end; at the same time, only through The calculated first frequency and second frequency adjust the numerically controlled oscillator, and the adjustment speed is fast.

In this embodiment, the dynamically set tuning value can be adjusted according to the real-time communication status, and is more accurate than the fixed tuning value.

In this embodiment, when the feedback control loop is open, the gradient scan configuration frequency offset of the numerically controlled oscillator is to set the first frequency of the iteration and the second frequency obtained by correcting the first frequency, avoiding the need to adjust the analog part of the receiver. Frequency points avoid the response time of waiting for the feedback control loop to lock the frequency of the CNC oscillator. The configuration is fast and can be implemented quickly.

Example 3:

This embodiment discloses a spread spectrum communication frequency offset correction device, as shown in Figure 7, including the following steps:

A signal receiving module, configured to receive a spread spectrum signal, which is obtained by calculating the original binary bit sequence sent by the transmitter and the spread spectrum sequence;

An iteration module, used to use the minimum frequency offset as the initial value of the first frequency, and the first frequency is iterated according to the tuning value within the frequency offset range;

In each iteration, the current first frequency is used as the current frequency of the numerically controlled oscillator, a despread binary bit sequence corresponding to the current first frequency is obtained, and the despread binary bit sequence corresponding to the current first frequency is verified with The original binary bit sequence; if the verification is successful, the current frequency of the numerically controlled oscillator is the frequency offset; if the verification fails, the current second frequency is obtained based on the current first frequency, and the current second frequency is used as the current frequency of the numerically controlled oscillator. frequency, obtain the despread binary bit sequence corresponding to the current second frequency, and verify the despread binary bit sequence corresponding to the current second frequency and the original binary bit sequence. If the verification is successful, then the numerically controlled oscillator The current frequency is the frequency offset; if the verification fails, the first frequency of the next iteration is used as the current frequency of the CNC oscillator, and the first frequency of the next iteration is calculated based on the current first frequency and the tuning value; repeat the above iteration process, until the verification of the despread binary bit sequence and the original binary bit sequence is successful, the current frequency of the numerically controlled oscillator is the frequency offset;

A frequency offset correction module is used to use the frequency offset as the frequency of a numerically controlled oscillator, and use the numerically controlled oscillator to correct the frequency offset of subsequently received spread spectrum signals.

Further, in the iteration module, the tuning value is calculated based on the maximum frequency offset range that the feedback control loop can capture under an ideal signal-to-noise ratio, the maximum signal-to-noise ratio, and the current signal-to-noise ratio.

Further, in the iterative module, the tuning value f _tune is:

Among them, W is the interval length of the maximum frequency offset range that the feedback control loop can capture under the ideal signal-to-noise ratio, SNR _max is the maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio, and α is the empirical value.

Further, in the iteration module, the current first frequency is added to the tuning value to obtain the first frequency of the next iteration.

Further, in the iteration module, the current second frequency is obtained based on the current first frequency, including:

The spread spectrum signal is sequentially operated with a numerically controlled oscillator and a spread spectrum sequence to obtain a despread signal;

In the despread signal, one correlation peak is detected for each fixed sequence length, the fixed sequence length is the sequence length of the spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;

The rotation angle between the coordinate points corresponding to adjacent correlation peaks is obtained according to the I signal value and Q signal value of each correlation peak position;

Obtain the correction frequency according to the rotation angle between the coordinate points corresponding to the adjacent correlation peaks;

The current second frequency is obtained according to the correction frequency and the current first frequency.

Further, in the iteration module, the rotation angle between the coordinate points corresponding to the adjacent correlation peaks is:

Among them, θ(k) is the rotation angle between the coordinate point corresponding to the k+1-th correlation peak and the coordinate point corresponding to the k-th correlation peak, I _xcorr (k) and Q _xcorr (k) are the k-th correlation peak respectively. The I signal value and Q signal value of the correlation peak, I _2corr (k+1) and Q _xcorr (k+1) are the I signal value and Q signal value of the k+1th correlation peak respectively, K is number of relevant peaks;

The correction frequency f _{guess_ave} is:

Among them, R is the bit rate;

The current second frequency for:

in, is the current first frequency, and l represents the number of iterations.

Further, in the iterative module, the I-channel signal value and Q-channel signal value at each correlation peak position are represented by signed numbers. According to the sign bit of the I-channel signal value and Q-channel signal value at each correlation peak position, The sign bit determines the binary data corresponding to the despread signal of each fixed sequence length, and the binary data corresponding to the despread signal of each fixed sequence length is sequentially combined to obtain a despread binary bit sequence.

Further, in the iteration module, the original binary bit sequence includes characteristic bit sequence information, and the despread binary bit sequence includes characteristic bit sequence information. If the characteristic bit sequence information of the original binary bit sequence is the same as the despread binary bit sequence If the characteristic bit sequence information matches, the despread binary bit sequence and the original binary bit sequence are successfully verified.

Further, the original binary bit sequence and the deexpanded binary bit sequence are represented by data frames. Each data frame includes several bytes. The byte at a fixed position in front of each data frame is defined as a feature bit, and the binary data corresponding to the feature bit is the characteristic bit sequence information.

Example 4:

This embodiment discloses a spread spectrum communication frequency offset correction device, which includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the program, any one of the above is implemented. The spread spectrum communication frequency offset correction method described in the item. The memory can be various types of memory, such as random access memory, read-only memory, flash memory, etc. The processor may be various types of processors, such as a central processing unit, a microprocessor, a digital signal processor or an image processor, etc.

This embodiment also discloses a computer-readable storage medium that stores computer-executable instructions, and the computer-executable instructions are used to execute any one of the aforementioned spread spectrum communication frequency offset correction methods. Storage media include: U disk, mobile hard disk, ROM, RAM, magnetic disk or optical disk and other media that can store program code.

The above are only preferred embodiments of the present invention. It should be pointed out that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (11)

1. A frequency offset correction method for spread spectrum communication is characterized by comprising the following steps:

receiving a spread spectrum signal, wherein the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;

taking the minimum frequency offset as a first frequency initial value, and iterating the first frequency within the frequency offset range according to the tuning value;

in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence;

if the verification is successful, the current frequency of the numerical control oscillator is frequency offset;

if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;

taking the frequency offset as the frequency of a numerical control oscillator, and correcting the frequency offset of a subsequently received spread spectrum signal through the numerical control oscillator;

the obtaining the current second frequency according to the current first frequency includes:

the spread spectrum signal is sequentially operated with a numerical control oscillator and a spread spectrum sequence to obtain a despread signal;

detecting a correlation peak in each fixed sequence length in the despread signal, wherein the fixed sequence length is the sequence length of a spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;

obtaining a rotation angle between coordinate points corresponding to adjacent correlation peaks according to the I-path signal value and the Q-path signal value of each correlation peak position;

obtaining correction frequency according to the rotation angle between coordinate points corresponding to the adjacent correlation peaks;

obtaining a current second frequency according to the correction frequency and the current first frequency;

the correction frequency is as follows: and summing the products of the rotation angles and the bit rates between the coordinate points corresponding to the adjacent correlation peaks.

2. The method of claim 1, wherein the tuning value is calculated according to a maximum frequency offset range, a maximum signal-to-noise ratio, and a current signal-to-noise ratio that can be captured by the feedback control loop under an ideal signal-to-noise ratio.

3. The method for correcting a spread spectrum communication frequency offset as claimed in claim 2, wherein said tuning value f _tune The method comprises the following steps:

wherein W is the interval length of the maximum frequency offset range which can be captured by the feedback control loop under the ideal signal-to-noise ratio, SNR _max For maximum signal-to-noise ratio, SNR is the current signal-to-noise ratio and α is the empirical value.

4. The method of claim 1, wherein the current first frequency is added to the tuning value to obtain the first frequency of the next iteration.

5. The method for correcting a spread spectrum communication frequency offset according to claim 1, wherein the rotation angle between coordinate points corresponding to adjacent correlation peaks is:

wherein θ (k) is a rotation angle between a coordinate point corresponding to the (k+1) th correlation peak and a coordinate point corresponding to the (k) th correlation peak, I _xcorr (k) And Q _xcorr (k) I-path signal value and Q-path signal value of kth correlation peak respectively, I _xcorr (k+1) and W _xcorr (k+1) is the I-path signal value and the Q-path signal value of the (k+1) -th correlation peak, and K is the number of the correlation peaks;

the correction frequency f _{guess_ave} The method comprises the following steps:

wherein R is the bit rate;

the current second frequencyThe method comprises the following steps:

wherein,for the current first frequency, l represents the number of iterations.

6. The method for correcting frequency offset of spread spectrum communication according to claim 1, wherein the I-path signal value and the Q-path signal value of each correlation peak position are represented by signed numbers, binary data corresponding to the despread signals of each fixed sequence length are determined according to the sign bit of the I-path signal value and the sign bit of the Q-path signal value of each correlation peak position, and the binary data corresponding to the despread signals of each fixed sequence length are sequentially combined to obtain the despread binary bit sequence.

7. The method for correcting frequency offset of spread spectrum communication according to claim 1, wherein the original binary bit sequence includes characteristic bit sequence information, the despread binary bit sequence includes characteristic bit sequence information, and if the characteristic bit sequence information of the original binary bit sequence matches the characteristic bit sequence information of the despread binary bit sequence, the despread binary bit sequence and the original binary bit sequence are successfully checked.

8. The method of claim 7, wherein the original binary bit sequence and the despread binary bit sequence are represented by data frames, each data frame includes a plurality of bytes, the bytes defining a fixed position before each data frame are characteristic bits, and binary data corresponding to the characteristic bits is characteristic bit sequence information.

9. A spread spectrum communication frequency offset correction apparatus, comprising:

the signal receiving module is used for receiving a spread spectrum signal, and the spread spectrum signal is obtained by operation according to an original binary bit sequence and a spread spectrum sequence sent by a sending end;

the iteration module is used for taking the minimum frequency offset as a first frequency initial value, and the first frequency is iterated within the frequency offset range according to the tuning value;

in each iteration, taking the current first frequency as the current frequency of the numerical control oscillator to obtain a despread binary bit sequence corresponding to the current first frequency, and checking the despread binary bit sequence corresponding to the current first frequency and an original binary bit sequence; if the verification is successful, the current frequency of the numerical control oscillator is frequency offset; if the verification fails, obtaining a current second frequency according to the current first frequency, taking the current second frequency as the current frequency of the numerical control oscillator, obtaining a despread binary bit sequence corresponding to the current second frequency, and verifying the despread binary bit sequence corresponding to the current second frequency and an original binary bit sequence, wherein if the verification is successful, the current frequency of the numerical control oscillator is frequency deviation; if the verification fails, taking the first frequency of the next iteration as the current frequency of the numerical control oscillator, wherein the first frequency of the next iteration is calculated according to the current first frequency and the tuning value; repeating the iterative process until the binary bit sequence and the original binary bit sequence are successfully checked and despread, wherein the current frequency of the numerical control oscillator is frequency offset;

the frequency offset correction module is used for taking the frequency offset as the frequency of a numerical control oscillator and correcting the frequency offset of a subsequently received spread spectrum signal through the numerical control oscillator;

the obtaining the current second frequency according to the current first frequency includes:

the spread spectrum signal is sequentially operated with a numerical control oscillator and a spread spectrum sequence to obtain a despread signal;

detecting a correlation peak in each fixed sequence length in the despread signal, wherein the fixed sequence length is the sequence length of a spread spectrum sequence, and the correlation peak is the position with the maximum signal amplitude in each fixed sequence length;

obtaining a rotation angle between coordinate points corresponding to adjacent correlation peaks according to the I-path signal value and the Q-path signal value of each correlation peak position;

obtaining correction frequency according to the rotation angle between coordinate points corresponding to the adjacent correlation peaks;

obtaining a current second frequency according to the correction frequency and the current first frequency;

the correction frequency is as follows: and summing the products of the rotation angles and the bit rates between the coordinate points corresponding to the adjacent correlation peaks.

10. A spread spectrum communication frequency offset correction apparatus comprising a processor, a memory and a computer program stored on the memory and operable on the processor, wherein the processor implements the spread spectrum communication frequency offset correction method as claimed in any one of claims 1 to 8 when the program is executed by the processor.

11. A computer-readable storage medium having stored thereon computer-executable instructions for performing the spread spectrum communication frequency offset correction method of any one of claims 1 to 8.