A target screening method for secondary radar

Abstract

The application discloses a target screening method of secondary radar, which comprises the following steps: a interrogator transmits a synchronization sequence P1 and a synchronization sequence P2 to a responder; the interrogator transmits a sequence containing weight and check information to the responder; the responder uses the same spread spectrum code as the interrogator to complete synchronization processing, takes the energy value of the synchronization sequence P1 as the energy value E1 of the sum channel, takes the energy value of the synchronization sequence P2 as the energy value E2 of the difference channel, resolves the weight of the sum channel and the difference channel from the sequence P3, and takes the weight value W1 of the sum channel and the difference channel after completing the check; the responder judges the energy value E1 of the sum channel and the energy value E2 of the difference channel to complete the screening of the targets in front of the interrogator. The application can greatly improve the accuracy of the target screening of the interrogator.

Description

Technical Field

[0001] This invention relates to the field of secondary radar technology, and in particular to a target selection method for secondary radar. Background Technology

[0002] With the rapid development of integrated circuit technology, the trend towards miniaturization and intelligence of electronic devices is becoming increasingly clear. Secondary radar systems generally consist of an interrogator and a transponder. Their basic working principle is as follows: the interrogator transmits an interrogation signal to the transponder; the transponder correctly decodes the signal and responds within a specified time; the interrogator decodes the response signal and obtains the result. Secondary radar systems are characterized by collaborative operation, employing spread spectrum, frequency hopping, and time-division multiplexing modes, and are widely used in military and civil aviation fields. Their typical hardware architecture includes a directional antenna (interrogator), an omnidirectional antenna (transponder), an excitation and receiving module, a signal processing module, and a display and control module. Based on the current development of digital and analog integrated circuit technology and software-defined radio technology, the miniaturization of the excitation and receiving module and the signal processing module has become largely mature. Due to limitations in target selection and lobe performance, the miniaturization of the interrogator's directional antenna has become a major challenge restricting the miniaturization of secondary radar. Simultaneously, finding a high-performance target selection method with a small antenna size has become a research hotspot.

[0003] Existing secondary radar target selection methods rely entirely on the physical characteristics of the antenna for target resolution and selection: the larger the antenna aperture, the better the resolution and selection capabilities. However, in miniaturized, portable secondary radar systems, the antenna size requirements are more stringent due to the overall device size constraints. With small antennas, existing technologies cannot achieve satisfactory target selection and resolution. Summary of the Invention

[0004] In view of this, the present invention provides a target selection method for secondary radar, which can overcome the problems of small antenna aperture, poor target selection and resolution in miniaturized secondary radar systems, and enable it to be applied to miniaturized secondary radar systems.

[0005] This invention discloses a target selection method for secondary radar, applied to a miniaturized secondary radar system, comprising:

[0006] Step 1: The interrogator transmits synchronization sequence P1 and synchronization sequence P2 to the transponder; the interrogator and transponder use the same pre-agreed spreading code;

[0007] Step 2: The interrogator transmits sequence P3 containing weight and verification information to the transponder;

[0008] Step 3: The transponder uses the same spreading code as the interrogator to complete the synchronization process. The energy value of the synchronization sequence P1 is used as the energy value E1 of the sum channel, and the energy value of the synchronization sequence P2 is used as the energy value E2 of the difference channel. The weights of the sum channel and the difference channel are decomposed from the sequence P3. After verification, they are used as the weight values ​​W1 of the sum channel and the difference channel.

[0009] Step 4: The transponder judges the energy value E1 of the sum channel and the energy value E2 of the difference channel to complete the screening of the target in front of the interrogator.

[0010] Further, step 1 includes:

[0011] Synchronization sequence P1 is transmitted from the sum channel and synchronization sequence P2 is transmitted from the difference channel. Synchronization sequences P1 and P2 are used for receiver synchronization by the transponder and consist of a spread spectrum code. The interrogator and the transponder use the same spread spectrum code agreed upon in advance. At the same time, the interrogator counter starts counting.

[0012] Further, step 2 includes:

[0013] The interrogator transmits sequence P3 containing the weights and verification information of the sum and difference channels; verification information is generated using CRC verification based on the weights of the sum and difference channels; the weights of the sum and difference channels are used to weight the sum and difference channels.

[0014] Further, step 4 includes:

[0015] If E1≥E2×W1, then respond; otherwise, discard the query information and do not respond.

[0016] The three targets located in the direction of the interrogator's main lobe are denoted as Q1, Q2, and P3, respectively.

[0017] If E 11 ≥E 21 ×W 11 And E 12 <E 22 ×W 12 And E 13 <E 23 ×W 13 Then Q2 and Q3 do not respond, and Q1 responds; where E 11 E 12 E 13 The sum and channel energies, E, are Q1, Q2, and Q3, respectively. 21 E 22 E 23 The difference channel energies W for Q1, Q2, and Q3, respectively. 11 W 12 W 13These are the difference channel weights for Q1, Q2, and Q3, respectively.

[0018] Furthermore, after step 4, the method further includes:

[0019] The interrogator uses the same spreading code as the transponder for synchronous reception. After receiving a valid response, the counter stops counting and calculates the distance between the interrogator and the transponder based on the count value.

[0020] Furthermore, the formula for calculating the distance between the interrogator and the transponder is as follows:

[0021]

[0022] In the formula, D r K1 is the target distance value, K2 is the count value when the response signal is obtained, K1 is the count value when the interrogation signal is sent, K3 is the fixed delay value, C is the speed of light, and T is the processor's clock cycle.

[0023] Furthermore, after calculating the distance between the interrogator and the transponder based on the count value, the method further includes:

[0024] Calculate the energy value E based on the signal returned by the transponder. r ;

[0025] According to the transponder energy value E r Distance value D from the target r Further screening to complete the target.

[0026] Furthermore, the transponder energy value E r The calculation formula is:

[0027]

[0028] Among them, S I With Q I These are the sums of the I and Q signals generated after the received signal is digitally down-converted and correlated with the spreading code used for receiving.

[0029] Furthermore, the statement based on the transponder energy value E r Distance value D from the target r Further screening of the target audience, including:

[0030] If E r ≤E lim And D r ≤L r If the target is found to be a valid target, then discard it; otherwise, retain it.

[0031] Among them, E limThis is the energy threshold, which can be measured based on the interrogator antenna back lobe pattern and the transponder's transmit power; L r The distance threshold is adaptively adjusted based on the interrogator and transponder sensitivity and back lobe directional gain.

[0032] Furthermore, in step 4:

[0033] The process by which the transponder judges the energy value E1 of the sum channel and the energy value E2 of the difference channel can be incorporated into the interrogation process. That is, if E1 ≥ E2 × W1, then the target is retained; otherwise, the target is discarded and no further processing is performed.

[0034] Because of the adoption of the above technical solution, the present invention has the following advantages:

[0035] 1. Without changing the existing antenna aperture or increasing hardware resources, digital signal processing can significantly improve the accuracy of interrogators in selecting targets in multi-transponder scenarios, thus resolving the contradiction between target resolution and antenna aperture to some extent. This method is implemented in software, has low complexity, and offers good flexibility and feasibility.

[0036] 2. This invention addresses the contradiction between the aperture of a miniaturized secondary radar antenna and its target selection performance. By leveraging the collaborative operation of the interrogator and transponder in a secondary radar system and employing signal processing technology, it comprehensively improves the interrogator's target selection capability and accuracy without altering the antenna size or increasing hardware resources.

[0037] 3. The secondary radar target selection method designed in this invention incorporates sum and difference weight values ​​into the information and performs a weighted comparison of the energy values ​​of the sum and difference channels based on these weight values, thereby improving the target selection capability in front of the interrogator. Simultaneously, using the transponder's energy and distance values ​​as target selection conditions improves the target selection capability behind the interrogator. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0039] Figure 1 This is a schematic diagram of a target selection scenario under multiple targets according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the target screening inquiry and response process according to an embodiment of the present invention;

[0041] Figure 3This is a schematic diagram of the signal processing of the target selection method of the secondary radar according to an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the interrogator / responder hardware architecture according to an embodiment of the present invention. Detailed Implementation

[0043] The present invention will be further described in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art should fall within the protection scope of the present invention.

[0044] For target filtering scenarios:

[0045] A multi-objective target selection scenario, such as Figure 1 As shown. In some cases, it is necessary to select target Q1 and eliminate other targets. Figure 1 In the diagram, targets Q2 and Q3 are adjacent to Q1 and located in the main lobe direction of the interrogator, while target Q4 is located in the back lobe direction. When the interrogator transmits an interrogation signal, without further processing, all transponders can correctly receive the signal and respond normally, resulting in interference. Without changing the antenna aperture, using traditional processing methods, the interrogator can no longer filter out target Q1, leading to a significant performance degradation.

[0046] Therefore, this application provides an embodiment of a target selection method using secondary radar. Utilizing digital processing technology and the characteristics of sum and difference antennas, and based on the cooperative operation characteristics of secondary radars, target selection is completed. The basic structure of the secondary radar system used in this embodiment is as follows:

[0047] The secondary radar system consists of an interrogator and a transponder. A hardware structure diagram is shown below. Figure 4 As shown. The signal processing module consists of processors (DSP, FPGA, etc.) and mainly performs the processing of transmitted and received signals. The excitation receiving module realizes the up-conversion and down-conversion of signals and the control of transmission and reception. The interrogator's excitation receiving module has two channels, sum and difference, and the antennas connected to it are sum and difference antennas. The transponder's excitation receiving module has only one channel, and the antenna connected to it is an omnidirectional antenna.

[0048] See Figure 3 The target screening method in this embodiment includes the following steps:

[0049] S1. Transmitting the interrogation signal: First, a synchronization sequence P1 is transmitted from the sum channel, followed by a synchronization sequence P2 from the difference channel. Synchronization sequences P1 and P2 are used for receiver synchronization by the transponder and consist of a spreading code. The interrogator and transponder use the same pre-agreed spreading code. Simultaneously, the interrogator counter begins counting, such as... Figure 2 As shown;

[0050] S2. Next, transmit sequence P3 containing sum and difference channel weights and verification information. The weight information can be flexibly set as needed. For example, the weight information can be set to a 7-bit binary number, and the step value can be set to 1dB / 2dB. Based on the weight information, weight verification information is generated using CRC verification. The verification information method can be other methods, agreed upon in advance by the interrogator and the transponder. Other verification methods can be selected for the weight information; the verification method is not unique.

[0051] S3. Finally, send other information (such as some custom information agreed upon by both parties).

[0052] S4. The transponder receives the interrogation signal: The same spreading code as the interrogator is used to complete the synchronization process. The energy value of the synchronization sequence P1 is calculated as the energy value E1 of the sum channel, and the energy value of the synchronization sequence P2 is calculated as the energy value E2 of the difference channel. The set weight information is deciphered from the sequence P3. After the verification is completed, it is used as the sum and difference weight value W1.

[0053] S5. The transponder judges the sum and difference energy values: if E1 ≥ E2 × W1, then a response is made; otherwise, the query information is discarded and no response is made. For example... Figure 1 Given three objectives Q1, Q2, and Q3, if the calculated E 11 ≥E 21 ×W 11 E 12 <E 22 ×W 12 E 13 <E 23 ×W 13 Then Q2 and Q3 do not respond, Q1 responds, and E 11 E 12 E 13 The sum and channel energies, E, are Q1, Q2, and Q3, respectively. 21 E 22 E 23 The difference channel energies, W, are Q1, Q2, and Q3, respectively. 11 W 12 W 13 These are the difference channel weights for Q1, Q2, and Q3, respectively. This process completes the screening of targets in front of the interrogator.

[0054] Optionally, the process of the transponder judging the sum and difference energy values ​​in S5 can be incorporated into the interrogation process, that is: if E1≥E2×W1, then the target is retained; otherwise, the target is discarded and no further processing is performed.

[0055] S6. The interrogator uses the same spreading code as the transponder for synchronous reception. Upon receiving a valid response, the counter stops counting and calculates the distance between the interrogator and the transponder based on the count value. The calculation formula is as follows: In the formula, K2 is the count value when the response signal is obtained, K1 is the count value when the interrogation signal is sent, K3 is the fixed delay value (fixed delay of hardware such as processor), C is the speed of light, which is 299792458m / s, and T is the clock cycle of the processor. The processor can generally be implemented by a programmable logic device, and the common clock cycles are 12.5ns (80MHz) and 10ns (100MHz).

[0056] S7. Calculate the energy value E based on the signal returned by the transponder. r .

[0057] S8. Based on the transponder energy value E r Distance value D from the target r This completes further screening of the target. If E r ≤E lim And D r ≤L r If the condition is met, the target is discarded; otherwise, the target is retained. Where E... lim This is the energy threshold, which can be determined based on the interrogator antenna back lobe pattern and the transponder's transmit power. r The distance threshold is adaptively adjusted based on the interrogator and transponder sensitivity and back lobe directional gain.

[0058] Optionally, the formula for calculating the energy value of interrogators and transponders is as follows: Where S I With Q I These are the sums of the I and Q signals generated after the received signal is digitally down-converted and correlated with the spreading code used for receiving. The spreading code can be set to 128 bits, 256 bits, 512 bits, etc., as needed.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A target selection method for secondary radar, applied to a miniaturized secondary radar system, characterized in that, include: Step 1: The interrogator transmits synchronization sequence P1 and synchronization sequence P2 to the transponder; the interrogator and transponder use the same pre-agreed spreading code; Step 2: The interrogator transmits sequence P3 containing weight and verification information to the transponder; Step 3: The transponder uses the same spreading code as the interrogator to complete the synchronization process, and uses the energy value of the synchronization sequence P1 as the energy value of the synchronization channel. The energy value of the synchronization sequence P2 is used as the energy value of the difference channel. The weights of the sum and difference channels are extracted from sequence P3, and after verification, they are used as the weight values ​​of the sum and difference channels. ; Step 4: Energy values ​​of the transponder pair and channel Energy values ​​of sum and difference channels Make judgments to complete the screening of targets in front of the interrogation machine; Step 4 includes: like If the query is successful, a response will be provided; otherwise, the query information will be discarded and no response will be provided. The three targets located in the direction of the interrogator's main lobe are denoted as Q1, Q2, and P3, respectively. like and and Then Q2 and Q3 will not respond, and Q1 will respond; among them, , , The sum and channel energies are Q1, Q2, and Q3, respectively. , , The difference channel energies for Q1, Q2, and Q3 are respectively. , , These are the difference channel weights for Q1, Q2, and Q3, respectively.

2. The method according to claim 1, characterized in that, Step 1 includes: Synchronization sequence P1 is transmitted from the sum channel and synchronization sequence P2 is transmitted from the difference channel. Synchronization sequences P1 and P2 are used for receiver synchronization by the transponder and consist of a spread spectrum code. The interrogator and the transponder use the same spread spectrum code agreed upon in advance. At the same time, the interrogator counter starts counting.

3. The method according to claim 2, characterized in that, Step 2 includes: The interrogator transmits sequence P3 containing the weights and verification information of the sum and difference channels; verification information is generated using CRC verification based on the weights of the sum and difference channels; the weights of the sum and difference channels are used to weight the sum and difference channels.

4. The method according to claim 1, characterized in that, After step 4, the following is also included: The interrogator uses the same spreading code as the transponder for synchronous reception. After receiving a valid response, the counter stops counting and calculates the distance between the interrogator and the transponder based on the count value.

5. The method according to claim 4, characterized in that, The formula for calculating the distance between the interrogator and the transponder is: In the formula, The target distance value. To determine the count value when the response signal is received, To query the count value when the signal was emitted, For a fixed delay value, At the speed of light, This represents the processor's clock cycle.

6. The method according to claim 4, characterized in that, After calculating the distance between the interrogator and the transponder based on the count value, the method further includes: Calculate the energy value based on the signal returned by the transponder. ; Based on the transponder energy value Distance to target value Further screening of the target was completed.

7. The method according to claim 6, characterized in that, The transponder energy value The calculation formula is: in, and These are the signals generated after digital down-conversion of the received signal. Road and The sum of the path signal and the spreading code used for reception.

8. The method according to claim 6, characterized in that, According to the transponder energy value Distance to target value Further screening of the target audience, including: like and If the target is found to be a valid target, then discard it; otherwise, retain it. in, This is the energy threshold value, measured based on the back lobe pattern of the interrogator antenna and the transmit power of the transponder; The distance threshold is adaptively adjusted based on the interrogator and transponder sensitivity and back lobe directional gain.

9. The method according to claim 1, characterized in that, In step 4: transponder pair and channel energy value Energy values ​​of sum and difference channels The process of making a judgment is incorporated into the interrogation process, that is: if If the target is selected, it will be retained; otherwise, it will be discarded without further action.

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