CN111817749B - Anti-forwarding interference direct sequence spread spectrum receiver and anti-forwarding interference method - Google Patents
Anti-forwarding interference direct sequence spread spectrum receiver and anti-forwarding interference method Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7075—Synchronisation aspects with code phase acquisition
Abstract
The invention discloses an anti-retransmission interference direct sequence spread spectrum receiver and an anti-retransmission interference method, and belongs to the field of communication. The invention firstly calculates the power of the correlation value after the spread spectrum code is matched and filtered, searches several maximum power values in a spread spectrum code period, then groups the power values, judges whether forwarding interference exists or not by combining the grouping, the power value and the interval delay of two maximum groups, and simultaneously switches the frequency point by utilizing the alarm mechanism of a control console, thereby realizing the aim of resisting the forwarding interference. The invention has the characteristics of simple and effective algorithm realization, no need of adding extra anti-forwarding interference overhead to a channel link and no need of adding an anti-forwarding interference function to other equipment in a receiving system, and is particularly suitable for the conditions of simple hardware realization requirement and high link utilization rate requirement of a direct sequence spread spectrum receiver.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to an anti-interference-to-forward direct sequence spread spectrum receiver and an anti-interference-to-forward method.
Background
Space-to-air communication countermeasure technologies mainly based on satellite and airborne play an important role in the information battlefield. The radio signal is easy to intercept and is easy to interfere, so that the retransmission interference can completely destroy the receiving of the remote control and remote measuring signals by the remote control and remote measuring system.
Most of the currently researched anti-forwarding interference schemes need radar in a receiving system to assist in achieving identification and suppression of forwarding interference, a part of the schemes need a channel link to provide extra instructions to assist in judging the real-time performance of remote control and remote measurement signals, and a part of the schemes need complex mathematical operation in a receiver to achieve identification and suppression of forwarding interference, so that the problems that the receiving system is high in complexity, the channel link is high in cost, and an algorithm is complex and cannot be achieved are caused.
Disclosure of Invention
The invention aims to avoid the defects in the prior art and provides an anti-transfer interference direct sequence spread spectrum receiver and an anti-transfer interference method.
The purpose of the invention is realized as follows:
a direct sequence spread spectrum receiver with anti-forwarding interference comprises an acquisition unit 1, a search unit 2, a grouping unit 3, a judgment unit 4 and a console 5, wherein:
the acquisition unit 1 receives an externally input digital baseband signal for acquiring a spread spectrum code, and sends a power value and related information after matched filtering processing to the search unit 2;
the search unit 2 sequences power values in a spreading code period and sends the maximum power values and position information thereof to the grouping unit 3;
the grouping unit 3 groups the power values and the position information according to the input power values and the position information thereof and outputs the grouping condition to the judging unit 4;
the judging unit 4 judges whether forwarding interference exists according to the grouping condition, the power value range and the position interval, and if the forwarding interference exists, the alarm information is fed back to the control console 5 through a channel link;
if the console 5 receives the alarm information, the frequency point is switched to avoid forwarding interference.
Further, the specific working mode of the capturing unit 1 is as follows:
step S101, the capture unit 1 buffers the input digital baseband signal to a shift register with the length of a spread spectrum code period, and performs full correlation operation on the digital baseband signal and a known spread spectrum code;
step S102, taking a spread spectrum code period as a calculation unit, starting a counter to carry out cycle counting from 1 to the spread spectrum code period length, and enabling the cycle counting to be synchronous with the full correlation operation result in the step S101, thereby identifying position information for each full correlation operation result;
step S103, the calculating unit in the step S102 is accumulated for multiple times to obtain a full correlation value after multiple averaging, and in the calculating unit of the last accumulation, the averaged power value and the synchronized position information are output to the searching unit 2, and in addition, a power valid flag is set and output to the searching unit 2, wherein the power valid flag is set to be high only in the calculating unit of the last accumulation, and is set to be low in other times.
Further, the specific working mode of the search unit 2 is as follows:
step S201, initializing power value registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4 and corresponding position registers reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 to be 0, jumping to step S202 if the input power valid flag is high, otherwise continuing to wait;
step S202, if the currently input power value is larger than reg _ data1, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to reg _ data1, reg _ data1 to the currently input power value, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, reg _ addr2 to reg _ addr1, reg _ addr1 to the position information of the currently input power value, and then jumping to step S206; otherwise, jumping to step S203;
step S203, if the power value of the current input is larger than reg _ data2, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to the power value of the current input, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, updating reg _ addr2 to the position information of the power value of the current input, and then jumping to step S206; otherwise, jumping to step S204;
step S204, if the power value input currently is larger than reg _ data3, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to the power value input currently, simultaneously sequentially updating reg _ addr4 to reg _ addr3, updating reg _ addr3 to the position information of the power value input currently, and then jumping to step S206; otherwise, jumping to step S205;
step S205, if the currently input power value is larger than reg _ data4, updating reg _ data4 to the currently input power value, and updating reg _ addr4 to the position information of the currently input power value, and then jumping to step S206; otherwise, directly jumping to the step S206;
step S206, if the input power effective flag is detected to be set to be high or low, the registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4, as well as reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 are output to the grouping unit 3, and meanwhile, an end flag high pulse is output to the grouping unit 3, and the step S201 is jumped to; otherwise, the process jumps to step S202.
Further, when grouping, if the positions of each group are adjacent or independent, the grouping unit 3 considers that the grouping is not established and outputs the identifier set to the judgment unit 4; otherwise, the grouping is considered to be established, the mark is set to be high, and the grouped power value and the position information thereof are output to the judging unit 4.
Further, the specific working mode of the determining unit 4 is as follows:
step S401, if the flag sent by the grouping unit 3 is high, the maximum power value of each group is taken for comparison, the maximum power value is recorded into the register reg _ max1_ val, the position of the maximum power value is recorded into the register reg _ max1_ addr, the second maximum power value is recorded into the register reg _ max2_ val, the position of the second maximum power value is recorded into the register reg _ max2_ addr, and then the step S402 is skipped; otherwise, jumping to step S404;
step S402, if reg _ max1_ val is less than or equal to 2 times reg _ max2_ val, then the 2 power peaks are not considered to be the noise floor, and step S403 is skipped, otherwise step S404 is skipped;
step S403, calculating the difference between reg _ max1_ addr and reg _ max2_ addr, wherein the absolute value of the difference is the position interval of the two peak values, recording the position interval value, and then jumping to step S405;
step S404, setting the position interval of the two peak values at the moment as 0 and recording, and then jumping to step S405;
step S405, if the position interval values recorded for a plurality of times are not equal to 0, determining that forwarding interference possibly exists, and skipping to step S406, otherwise, not outputting an alarm signal, and skipping to step S407;
step S406, taking a plurality of continuous position interval values with a fixed quantity as a calculation unit, wherein the fixed quantity is more than or equal to 6, calculating the difference value of each position interval value and the two position interval values before the position interval value from the third position interval value in the calculation unit, and if the two difference values do not exceed the threshold value, the position interval value meets the requirement; counting the number of all position interval values meeting the requirements in a computing unit, if the number is more than or equal to half of the fixed number, determining that forwarding interference exists, and outputting an alarm signal, otherwise, not outputting the alarm signal; jumping to step S407;
in step S407, steps S401 to S406 are repeated.
In addition, the invention also provides an anti-forwarding interference method based on the direct sequence spread spectrum receiver, which comprises the following steps:
s1, receiving the digital baseband signal for capturing the spread spectrum code inputted from the outside by the capturing unit 1, and sending the power value and the relevant information after the matched filtering processing to the searching unit 2;
s2, sorting the power values in a spread spectrum code period through the search unit 2, and sending the maximum power values and the position information thereof to the grouping unit 3;
s3, grouping the power values according to the input power values and the position information thereof by the grouping unit 3 and the principle that the positions are adjacent to form a group, and then outputting the grouping condition to the judging unit 4;
s4, judging whether there is transfer interference by the judging unit 4 according to the grouping condition, the power value range and the position interval, if there is transfer interference, feeding back the alarm information to the control station 5 through the channel link;
and S5, receiving the alarm information through the console 5, and if the alarm information is received, switching the frequency point to avoid forwarding interference.
Further, the specific manner of step S1 is as follows:
step S101, the capture unit 1 buffers the input digital baseband signal to a shift register with the length of a spread spectrum code period, and performs full correlation operation on the digital baseband signal and a known spread spectrum code;
step S102, taking a spread spectrum code period as a calculation unit, starting a counter to carry out cycle counting from 1 to the spread spectrum code period length, and enabling the cycle counting to be synchronous with the full correlation operation result in the step S101, thereby identifying position information for each full correlation operation result;
step S103, the calculating unit in the step S102 is accumulated for multiple times to obtain a full correlation value after multiple averaging, and in the calculating unit of the last accumulation, the averaged power value and the synchronized position information are output to the searching unit 2, and in addition, a power valid flag is set and output to the searching unit 2, wherein the power valid flag is set to be high only in the calculating unit of the last accumulation, and is set to be low in other times.
Further, the specific manner of step S2 is as follows:
step S201, initializing power value registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4 and corresponding position registers reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 to be 0, jumping to step S202 if the input power valid flag is high, otherwise continuing to wait;
step S202, if the currently input power value is larger than reg _ data1, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to reg _ data1, reg _ data1 to the currently input power value, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, reg _ addr2 to reg _ addr1, reg _ addr1 to the position information of the currently input power value, and then jumping to step S206; otherwise, jumping to step S203;
step S203, if the power value of the current input is larger than reg _ data2, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to the power value of the current input, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, updating reg _ addr2 to the position information of the power value of the current input, and then jumping to step S206; otherwise, jumping to step S204;
step S204, if the power value input currently is larger than reg _ data3, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to the power value input currently, simultaneously sequentially updating reg _ addr4 to reg _ addr3, updating reg _ addr3 to the position information of the power value input currently, and then jumping to step S206; otherwise, jumping to step S205;
step S205, if the currently input power value is larger than reg _ data4, updating reg _ data4 to the currently input power value, and updating reg _ addr4 to the position information of the currently input power value, and then jumping to step S206; otherwise, directly jumping to the step S206;
step S206, if the input power effective flag is detected to be set to be high or low, the registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4, as well as reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 are output to the grouping unit 3, and meanwhile, an end flag high pulse is output to the grouping unit 3, and the step S201 is jumped to; otherwise, the process jumps to step S202.
Further, when grouping, if the positions of each group are adjacent or independent, the grouping unit 3 considers that the grouping is not established and outputs the identifier set to the judgment unit 4; otherwise, the grouping is considered to be established, the mark is set to be high, and the grouped power value and the position information thereof are output to the judging unit 4.
Further, the specific manner of step S4 is as follows:
step S401, if the flag sent by the grouping unit 3 is high, the maximum power value of each group is taken for comparison, the maximum power value is recorded into the register reg _ max1_ val, the position of the maximum power value is recorded into the register reg _ max1_ addr, the second maximum power value is recorded into the register reg _ max2_ val, the position of the second maximum power value is recorded into the register reg _ max2_ addr, and then the step S402 is skipped; otherwise, jumping to step S404;
step S402, if reg _ max1_ val is less than or equal to 2 times reg _ max2_ val, then the 2 power peaks are not considered to be the noise floor, and step S403 is skipped, otherwise step S404 is skipped;
step S403, calculating the difference between reg _ max1_ addr and reg _ max2_ addr, wherein the absolute value of the difference is the position interval of the two peak values, recording the position interval value, and then jumping to step S405;
step S404, setting the position interval of the two peak values at the moment as 0 and recording, and then jumping to step S405;
step S405, if the position interval values recorded for a plurality of times are not equal to 0, determining that forwarding interference possibly exists, and skipping to step S406, otherwise, not outputting an alarm signal, and skipping to step S407;
step S406, taking a plurality of continuous position interval values with a fixed quantity as a calculation unit, wherein the fixed quantity is more than or equal to 6, calculating the difference value of each position interval value and the two position interval values before the position interval value from the third position interval value in the calculation unit, and if the two difference values do not exceed the threshold value, the position interval value meets the requirement; counting the number of all position interval values meeting the requirements in a computing unit, if the number is more than or equal to half of the fixed number, determining that forwarding interference exists, and outputting an alarm signal, otherwise, not outputting the alarm signal; jumping to step S407;
in step S407, steps S401 to S406 are repeated.
Compared with the background technology, the invention has the following advantages:
1. the invention does not need complex mathematical operation (such as PartialFFT and FractionalFFT), has simple and effective algorithm and low realization complexity, and is favorable for being realized in a direct sequence spread spectrum receiver through embedded software (such as VHDL/Verilog) programming.
2. The invention utilizes the necessary spread spectrum code capture module in the direct sequence spread spectrum receiver and designs the interference judgment algorithm which is adaptive to the spread spectrum code capture module, thereby saving hardware resources.
3. The invention can enable the existing direct sequence spread spectrum receiver to have the capability of resisting the forwarding interference without additional equipment in a receiving system, has low complexity of system realization, and is suitable for airborne application scenes and the like with higher requirements on miniaturization.
4. The invention does not need to reserve extra overhead for the channel link to support the function of anti-forwarding interference, and can improve the utilization rate of the channel link.
In conclusion, the invention realizes a forwarding interference identification method suitable for a direct sequence spread spectrum receiver through a capture power and interference identification algorithm, and realizes the purpose of resisting forwarding interference by combining a console alarm mechanism, thereby changing the current situation that the existing direct sequence spread spectrum receiver does not have the capability of resisting forwarding interference and having important application value.
Drawings
Fig. 1 is a schematic block diagram of an embodiment of the present invention.
Fig. 2 is a flowchart of a search process of the search unit in the embodiment of the present invention.
FIG. 3 is a flowchart of a determining process of the determining unit in the embodiment of the present invention.
Detailed Description
The technical solution of the present invention is further described in detail below with reference to the accompanying drawings.
Referring to fig. 1, a direct sequence spread spectrum receiver resistant to forward interference includes an acquisition unit 1, a search unit 2, a grouping unit 3, a judgment unit 4, and a console 5. Fig. 1 is a schematic block diagram of the present embodiment, which connects lines according to fig. 1.
The acquisition unit 1 is used for performing full correlation operation on a digital baseband signal which is input from the outside and used for acquiring a spread spectrum code and a known spread spectrum code word to obtain a power value and related information; the searching unit 2 is used for sequencing the power values in a spreading code period and searching several maximum power values; the grouping unit 3 groups the power values and the position information according to the searched power values and the position information thereof; the judging unit 4 judges whether forwarding interference exists according to the grouping condition, the power value range and the position interval; the console 5 judges whether measures such as frequency point switching are needed to avoid forwarding interference according to the obtained alarm information.
Further, the specific working mode of the capturing unit 1 is as follows:
step S101, the capture unit 1 buffers the input digital baseband signal to a shift register with the length of a spread spectrum code period, and performs full correlation operation on the digital baseband signal and a known spread spectrum code;
step S102, taking a spread spectrum code period as a calculation unit, starting a counter to carry out cycle counting from 1 to the spread spectrum code period length, and enabling the cycle counting to be synchronous with the full correlation operation result in the step S101, thereby identifying position information for each full correlation operation result;
step S103, in order to improve the accuracy, the calculating unit in step S102 is accumulated for multiple times to obtain N1 averaged full correlation values, in the last accumulated calculating unit, the averaged power value and the synchronized position information are output to the searching unit 2, and in addition, a power valid flag is set and output to the searching unit 2, wherein the power valid flag is set to be high only in the last accumulated calculating unit, and is set to be low at other times. In this example, N1 is 32.
The searching unit 2 searches out the largest N2 values according to the power value input by the capturing unit 1 and records the position information thereof, in this example, a bubble sorting method is adopted, and N2= 4. Fig. 2 is a flow chart of a search process of a search unit, comprising the steps of:
step S201, initializing power value registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4 and corresponding position registers reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 to be 0, jumping to step S202 if the input power valid flag is high, otherwise continuing to wait;
in order to improve the operation efficiency, the input low-multiple clock can be changed into high-multiple clock, so that the input signal is also copied into a plurality of signals, and at the moment, only one signal is selected from the plurality of copied signals to perform the following operations:
step S202, if the currently input power value is larger than reg _ data1, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to reg _ data1, reg _ data1 to the currently input power value, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, reg _ addr2 to reg _ addr1, reg _ addr1 to the position information of the currently input power value, and then jumping to step S206; otherwise, jumping to step S203;
step S203, if the power value of the current input is larger than reg _ data2, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to the power value of the current input, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, updating reg _ addr2 to the position information of the power value of the current input, and then jumping to step S206; otherwise, jumping to step S204;
step S204, if the power value input currently is larger than reg _ data3, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to the power value input currently, simultaneously sequentially updating reg _ addr4 to reg _ addr3, updating reg _ addr3 to the position information of the power value input currently, and then jumping to step S206; otherwise, jumping to step S205;
step S205, if the currently input power value is larger than reg _ data4, updating reg _ data4 to the currently input power value, and updating reg _ addr4 to the position information of the currently input power value, and then jumping to step S206; otherwise, directly jumping to the step S206;
step S206, if the input power effective flag is detected to be set to be high or low, the registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4, as well as reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 are output to the grouping unit 3, and meanwhile, an end flag high pulse is output to the grouping unit 3, and the step S201 is jumped to; otherwise, the process jumps to step S202.
The judging unit 4 judges whether forwarding interference exists according to the grouping information input by the grouping unit 3, and informs the control console of the judgment result as alarm information through a channel link so that the control console can take anti-interference measures. Fig. 3 is a flowchart of a judging process of the judging unit, including the steps of:
step S401, if the input flag is set high, each group of maximum power values is taken for comparison, the maximum power value is recorded into a register reg _ max1_ val, the position of the maximum power value is recorded into a register reg _ max1_ addr, the second maximum power value is recorded into a register reg _ max2_ val, the position of the second maximum power value is recorded into a register reg _ max2_ addr, and then the step S402 is skipped; otherwise, jumping to step S404;
step S402, if reg _ max1_ val is less than or equal to 2 times reg _ max2_ val, then the 2 power peaks are not considered to be the noise floor, and step S403 is skipped, otherwise step S404 is skipped;
step S403, calculate the position interval addr _ margin of the two peaks:
addr_margin = |reg_max1_addr-reg_max2_addr|，
then jumping to step S405;
step S404, making addr _ margin =0, and jumping to step S405;
step S405, if addr _ margin is not equal to 0 for 3 times continuously, jumping to step S6, otherwise, continuously waiting and not outputting an alarm signal;
step S406, taking each 8-time input as 1 calculation cycle, counting the times meeting the condition if the difference value between the addr _ margin input each time and the addr _ margin input last time or last time is less than or equal to 4 (ignoring the first time), and if the difference value exceeds 4 times within 8 times, determining that forwarding interference exists and outputting an alarm signal, otherwise, not outputting the alarm signal.
The console 5 judges whether measures such as frequency point switching are needed to avoid forwarding interference according to the alarm signal input by the judging unit 4, so that the purpose of resisting forwarding interference of the receiver is achieved.
The simple working principle of the direct sequence spread spectrum receiver is as follows:
the device judges whether the forwarding interference exists or not by using the correlation performance of the spread spectrum code and an interference identification algorithm, and then achieves the purpose of resisting the forwarding interference by switching the frequency point through the alarm control console. The device mainly comprises a capturing unit, a searching unit, a grouping unit, a judging unit and a console. The capture unit performs matched filtering of the input digital baseband signal. The search unit finds the maximum N2 power values within one spreading code period. The grouping units group the N2 power values in groups that are located adjacently. The judging unit judges whether forwarding interference exists according to the grouping situation, the power value range and the position interval. And the console judges whether measures such as frequency point switching and the like need to be taken to avoid forwarding interference according to the alarm information.
An anti-forwarding interference method based on a direct sequence spread spectrum receiver comprises the following steps:
s1, receiving the digital baseband signal for capturing the spread spectrum code inputted from the outside by the capturing unit 1, and sending the power value and the relevant information after the matched filtering processing to the searching unit 2;
s2, sorting the power values in a spread spectrum code period through the search unit 2, and sending the maximum power values and the position information thereof to the grouping unit 3;
s3, grouping the power values according to the input power values and the position information thereof by the grouping unit 3 and the principle that the positions are adjacent to form a group, and then outputting the grouping condition to the judging unit 4;
s4, judging whether there is transfer interference by the judging unit 4 according to the grouping condition, the power value range and the position interval, if there is transfer interference, feeding back the alarm information to the control station 5 through the channel link;
and S5, receiving the alarm information through the console 5, and if the alarm information is received, switching the frequency point to avoid forwarding interference.
Specifically, in the method, a direct sequence spread spectrum receiver receives an analog signal, the analog signal is subjected to AD sampling and filtering, a digital baseband signal is sent to a capture unit, a full correlation value of the signal and a spread spectrum code is obtained through matched filtering, and a power value and position information of the power value in a spread spectrum code period are obtained through multiple accumulation and averaging. The search unit orders the power values in one input spreading code period and searches the maximum N2 power values and corresponding position information. The grouping unit groups N2 power values into a group by adjacent positions, if N2 positions are adjacent or N2 positions are independent, the grouping is not determined and the flag is set to be low, otherwise, the flag is set to be high according to the group recording power values and the corresponding positions. The judgment unit judges the input flag, if the level is low, the peak position interval addr _ margin is set to be 0, otherwise, each input group is arranged from high to low according to the power value, the maximum value of each group is compared, two groups with the maximum value are found, if the 2 maximum values of power do not meet the condition, the peak position interval addr _ margin is set to be 0, otherwise, the 2 peak position intervals addr _ margin are calculated, and if the addr _ margin is not equal to 0 for N3 times continuously, the forwarding interference is considered to possibly exist. The method for judging the deviation of the peak position interval addr _ margin is to take input every 8 times as 1 calculation period, if the difference value of the addr _ margin input every time and the addr _ margin input last time or last time is less than or equal to 4 (neglecting the first time), counting the times meeting the condition, if the difference value exceeds 4 times within 8 times, considering that forwarding interference exists, and outputting an alarm signal. If the control station receives the alarm information, the control station adopts measures such as frequency point switching and the like to avoid forwarding interference, thereby realizing the purpose of resisting the forwarding interference in the direct sequence spread spectrum receiver.
In a word, the invention adopts the design of the joint judgment of the capture power and the interference recognition algorithm and the alarm mechanism of the control console, has the characteristics of simple and effective algorithm realization, no need of adding extra anti-forwarding interference overhead to a channel link, no need of adding the anti-forwarding interference function to other equipment (such as a radar) in a receiving system, and is particularly suitable for the conditions of simple hardware realization requirement and high link utilization rate requirement of a direct sequence spread spectrum receiver.
Claims (8)
1. An anti-retransmission interference direct sequence spread spectrum receiver is characterized by comprising an acquisition unit (1), a search unit (2), a grouping unit (3), a judgment unit (4) and a console (5), wherein:
the acquisition unit (1) receives an externally input digital baseband signal for acquiring a spread spectrum code, and sends a power value and related information after matched filtering processing to the search unit (2); the specific working mode of the capturing unit (1) is as follows:
step S101, a capturing unit (1) buffers an input digital baseband signal to a shift register with the length of a spread spectrum code period, and performs full correlation operation on the digital baseband signal and a known spread spectrum code;
step S102, taking a spread spectrum code period as a calculation unit, starting a counter to carry out cycle counting from 1 to the spread spectrum code period length, and enabling the cycle counting to be synchronous with the full correlation operation result in the step S101, thereby identifying position information for each full correlation operation result;
step S103, accumulating the calculating units in the step S102 for multiple times to obtain a full correlation value after multiple averaging, outputting the averaged power value and the synchronous position information to the searching unit (2) in the calculating unit of the last accumulation, and setting a power effective identifier and outputting the power effective identifier to the searching unit (2), wherein the power effective identifier is only set to be high in the calculating unit of the last accumulation, and is set to be low in other times;
the search unit (2) sequences the power values in a spread spectrum code period and sends the maximum power values and position information thereof to the grouping unit (3);
the grouping unit (3) groups the power values and the position information according to the input power values and the position information thereof and the principle that the positions are adjacent to form a group, and then outputs the grouping condition to the judging unit (4);
the judging unit (4) judges whether forwarding interference exists according to the grouping condition, the power value range and the position interval, and if the forwarding interference exists, the alarm information is fed back to the control console (5) through a channel link;
if the console (5) receives the alarm information, the frequency point is switched to avoid forwarding interference.
2. The direct sequence spread spectrum receiver with immunity to forward interference according to claim 1, wherein said search unit (2) operates in a specific manner:
step S201, initializing power value registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4 and corresponding position registers reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 to be 0, jumping to step S202 if the input power valid flag is high, otherwise continuing to wait;
step S202, if the currently input power value is larger than reg _ data1, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to reg _ data1, reg _ data1 to the currently input power value, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, reg _ addr2 to reg _ addr1, reg _ addr1 to the position information of the currently input power value, and then jumping to step S206; otherwise, jumping to step S203;
step S203, if the power value of the current input is larger than reg _ data2, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to the power value of the current input, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, updating reg _ addr2 to the position information of the power value of the current input, and then jumping to step S206; otherwise, jumping to step S204;
step S204, if the power value input currently is larger than reg _ data3, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to the power value input currently, simultaneously sequentially updating reg _ addr4 to reg _ addr3, updating reg _ addr3 to the position information of the power value input currently, and then jumping to step S206; otherwise, jumping to step S205;
step S205, if the currently input power value is larger than reg _ data4, updating reg _ data4 to the currently input power value, and updating reg _ addr4 to the position information of the currently input power value, and then jumping to step S206; otherwise, directly jumping to the step S206;
step S206, if the input power effective identification is detected to be set to be high or low, the registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4, as well as reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 are output to the grouping unit (3), and meanwhile, an end identification high pulse is output to the grouping unit (3), and the step S201 is jumped to; otherwise, the process jumps to step S202.
3. The direct sequence spread spectrum receiver of claim 1, wherein the grouping unit (3) is configured to, when grouping, consider that the grouping is not true and output the flag to the determining unit (4) if the positions of the groups are adjacent or independent; otherwise, the grouping is considered to be established, the mark is set to be high, and the grouped power value and the position information thereof are output to a judging unit (4).
4. The direct-sequence spread spectrum receiver with immunity to forward interference according to claim 3, wherein the determining unit (4) is specifically operated as follows:
step S401, if the mark sent by the grouping unit (3) is high, each group of maximum power values is taken for comparison, the maximum power value is recorded into a register reg _ max1_ val, the position of the maximum power value is recorded into a register reg _ max1_ addr, the second maximum power value is recorded into a register reg _ max2_ val, the position of the second maximum power value is recorded into a register reg _ max2_ addr, and then the step S402 is skipped; otherwise, jumping to step S404;
step S402, if reg _ max1_ val is less than or equal to 2 times reg _ max2_ val, then the 2 power peaks are not considered to be the noise floor, and step S403 is skipped, otherwise step S404 is skipped;
step S403, calculating the difference between reg _ max1_ addr and reg _ max2_ addr, wherein the absolute value of the difference is the position interval of the two peak values, recording the position interval value, and then jumping to step S405;
step S404, setting the position interval of the two peak values at the moment as 0 and recording, and then jumping to step S405;
step S405, if the position interval values recorded for a plurality of times are not equal to 0, determining that forwarding interference possibly exists, and skipping to step S406, otherwise, not outputting an alarm signal, and skipping to step S407;
step S406, taking a plurality of continuous position interval values with a fixed quantity as a calculation unit, wherein the fixed quantity is more than or equal to 6, calculating the difference value of each position interval value and the two position interval values before the position interval value from the third position interval value in the calculation unit, and if the two difference values do not exceed the threshold value, the position interval value meets the requirement; counting the number of all position interval values meeting the requirements in a computing unit, if the number is more than or equal to half of the fixed number, determining that forwarding interference exists, and outputting an alarm signal, otherwise, not outputting the alarm signal; jumping to step S407;
in step S407, steps S401 to S406 are repeated.
5. An anti-forward interference method based on a direct sequence spread spectrum receiver is characterized by comprising the following steps:
s1, receiving the digital baseband signal for capturing the spread spectrum code inputted from the outside by the capturing unit (1), and sending the power value and the relevant information after the matched filtering processing to the searching unit (2);
the specific manner of step S1 is:
step S101, a capturing unit (1) buffers an input digital baseband signal to a shift register with the length of a spread spectrum code period, and performs full correlation operation on the digital baseband signal and a known spread spectrum code;
step S102, taking a spread spectrum code period as a calculation unit, starting a counter to carry out cycle counting from 1 to the spread spectrum code period length, and enabling the cycle counting to be synchronous with the full correlation operation result in the step S101, thereby identifying position information for each full correlation operation result;
step S103, accumulating the calculating units in the step S102 for multiple times to obtain a full correlation value after multiple averaging, outputting the averaged power value and the synchronous position information to the searching unit (2) in the calculating unit of the last accumulation, and setting a power effective identifier and outputting the power effective identifier to the searching unit (2), wherein the power effective identifier is only set to be high in the calculating unit of the last accumulation, and is set to be low in other times;
s2, sorting the power values in a spread code period by the search unit (2), and sending the maximum power values and the position information thereof to the grouping unit (3);
s3, grouping the power values according to the input power values and the position information thereof by the grouping unit (3) and the principle that the positions are adjacent to form a group, and then outputting the grouping condition to the judging unit (4);
s4, judging whether there is transfer interference by the judging unit (4) according to the grouping condition, the power value range and the position interval, if there is transfer interference, feeding back the alarm information to the console (5) through the channel link;
and S5, receiving the alarm information through the console (5), and if the alarm information is received, switching the frequency point to avoid forwarding interference.
6. The anti-forward interference method based on direct sequence spread spectrum receiver according to claim 5, wherein the step S2 is implemented by:
step S201, initializing power value registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4 and corresponding position registers reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 to be 0, jumping to step S202 if the input power valid flag is high, otherwise continuing to wait;
step S202, if the currently input power value is larger than reg _ data1, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to reg _ data1, reg _ data1 to the currently input power value, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, reg _ addr2 to reg _ addr1, reg _ addr1 to the position information of the currently input power value, and then jumping to step S206; otherwise, jumping to step S203;
step S203, if the power value of the current input is larger than reg _ data2, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to reg _ data2, reg _ data2 to the power value of the current input, simultaneously sequentially updating reg _ addr4 to reg _ addr3, reg _ addr3 to reg _ addr2, updating reg _ addr2 to the position information of the power value of the current input, and then jumping to step S206; otherwise, jumping to step S204;
step S204, if the power value input currently is larger than reg _ data3, sequentially updating reg _ data4 to reg _ data3, reg _ data3 to the power value input currently, simultaneously sequentially updating reg _ addr4 to reg _ addr3, updating reg _ addr3 to the position information of the power value input currently, and then jumping to step S206; otherwise, jumping to step S205;
step S205, if the currently input power value is larger than reg _ data4, updating reg _ data4 to the currently input power value, and updating reg _ addr4 to the position information of the currently input power value, and then jumping to step S206; otherwise, directly jumping to the step S206;
step S206, if the input power effective identification is detected to be set to be high or low, the registers reg _ data1, reg _ data2, reg _ data3 and reg _ data4, as well as reg _ addr1, reg _ addr2, reg _ addr3 and reg _ addr4 are output to the grouping unit (3), and meanwhile, an end identification high pulse is output to the grouping unit (3), and the step S201 is jumped to; otherwise, the process jumps to step S202.
7. The anti-forward interference method based on direct sequence spread spectrum receiver according to claim 5, wherein the grouping unit (3) considers that the grouping is not true and outputs the identifier low to the judging unit (4) if the positions of the groups are adjacent or independent when grouping; otherwise, the grouping is considered to be established, the mark is set to be high, and the grouped power value and the position information thereof are output to a judging unit (4).
8. The anti-forward interference method based on direct sequence spread spectrum receiver according to claim 7, wherein the step S4 is implemented by:
step S401, if the mark sent by the grouping unit (3) is high, each group of maximum power values is taken for comparison, the maximum power value is recorded into a register reg _ max1_ val, the position of the maximum power value is recorded into a register reg _ max1_ addr, the second maximum power value is recorded into a register reg _ max2_ val, the position of the second maximum power value is recorded into a register reg _ max2_ addr, and then the step S402 is skipped; otherwise, jumping to step S404;
step S402, if reg _ max1_ val is less than or equal to 2 times reg _ max2_ val, then the 2 power peaks are not considered to be the noise floor, and step S403 is skipped, otherwise step S404 is skipped;
step S403, calculating the difference between reg _ max1_ addr and reg _ max2_ addr, wherein the absolute value of the difference is the position interval of the two peak values, recording the position interval value, and then jumping to step S405;
step S404, setting the position interval of the two peak values at the moment as 0 and recording, and then jumping to step S405;
step S405, if the position interval values recorded for a plurality of times are not equal to 0, determining that forwarding interference possibly exists, and skipping to step S406, otherwise, not outputting an alarm signal, and skipping to step S407;
step S406, taking a plurality of continuous position interval values with a fixed quantity as a calculation unit, wherein the fixed quantity is more than or equal to 6, calculating the difference value of each position interval value and the two position interval values before the position interval value from the third position interval value in the calculation unit, and if the two difference values do not exceed the threshold value, the position interval value meets the requirement; counting the number of all position interval values meeting the requirements in a computing unit, if the number is more than or equal to half of the fixed number, determining that forwarding interference exists, and outputting an alarm signal, otherwise, not outputting the alarm signal; jumping to step S407;
in step S407, steps S401 to S406 are repeated.
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