Radar receiving link AGC distribution method based on third-order intermodulation and noise coefficient

Abstract

The invention belongs to the technical field of radar receiving link AGC distribution, and particularly relates to a radar receiving link AGC distribution method based on third-order cross-harmonic and noise coefficients, during specific application, the optimal AGC distribution combination can be selected according to the radar working state and AGC control value demand real-time data, the gain value of a receiving link multi-stage attenuator can be adjusted in real time, and the radar receiving link AGC distribution method based on the third-order cross-harmonic and noise coefficients can be realized. By means of the method, the radar system third-order intermodulation component can meet the false alarm rate index, meanwhile, the noise coefficient of the radar system is minimum, AGC optimal distribution can be carried out in the FPGA in real time under different radar system working states, and the effect of rapidly optimizing the radio frequency link index in real time is achieved.

Description

Technical Field

[0001] The present application belongs to the technical field of radar receiving link AGC allocation, and in particular relates to a radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient. Background Art

[0002] In the actual pulse Doppler radar signal environment, the echo spectrum includes not only height clutter, mainboard clutter, sidelobe clutter and target echo, but also internal noise of the receiver. When a large target is at a close distance, its reflected signal may cause the receiver to overload and destroy the normal operation of the receiver. When a small target is at a long distance, its reflected signal is very weak, resulting in the target echo intensity failing to pass the detection threshold.

[0003] The automatic gain control system is a circuit used to ensure the normal operation of the receiver. When the signal is strong, the receiving link attenuator value is increased to reduce the overall gain of the receiver link. When the signal is weak, the receiving link attenuator value is reduced to increase the overall gain of the receiver link.

[0004] The automatic gain control system adopts automatic gain control (AGC), which is a feedback control technology that can automatically adjust the gain of the receiver. There are two ways to implement AGC: analog and digital. Among them, the AGC control value distribution method implemented in digital form has a fixed adjustment method. The AGC control value is continuously adjusted based on the echo data characteristics of the actual test flight process in an empirical manner. The AGC control value is usually increased sequentially starting from the intermediate frequency. As the total attenuation increases, the noise coefficient and false alarm rate indicators of the receiving link are difficult to achieve the optimal. In view of this, this application is proposed.

[0005] This application is proposed in view of the above-mentioned technical defects. Summary of the invention

[0006] The purpose of this application is to provide a radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient. By adjusting the gain value of the multi-stage attenuator of the receiving link in real time, the third-order intermodulation component of the radar system can meet the false alarm rate index while minimizing the noise coefficient of the radar system.

[0007] The technical solution of this application is:

[0008] A radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient, comprising:

[0009] Step 1: According to the radar working state and AGC control value requirements, traverse each AGC allocation combination to calculate the corresponding radar pulse accumulation point gain GFFT, AD end thermal noise TN, and the third-order intermodulation product IM3 of the receiving link;

[0010] Step 2: Determine whether there is an AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, where R is the detection threshold;

[0011] Step 3: If there is an AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, then use the AGC allocation combination with the smallest receiving link noise figure F among them as the optimal AGC allocation combination;

[0012] Step 4: If there is no AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, then use the AGC allocation combination corresponding to the largest TN - IM3 among them as the optimal AGC allocation combination;

[0013] Step 5: Change the radar operating state and the AGC control value requirement, and repeat the above Steps 1 - 4 to obtain the optimal AGC allocation combination under different radar operating states and AGC total attenuation requirements.

[0014] According to at least one embodiment of the present application, in the above radar receiving link AGC allocation method based on third - order intermodulation and noise figure, GFFT = 10·lg(M);

[0015] where,

[0016] M is the number of radar pulse accumulations, taking 4096 for long distances, 512 for medium distances, and 128 for short distances.

[0017] According to at least one embodiment of the present application, in the above radar receiving link AGC allocation method based on third - order intermodulation and noise figure, R takes 13 dB.

[0018] According to at least one embodiment of the present application, in the above radar receiving link AGC allocation method based on third - order intermodulation and noise figure, TN = 10lg(KTB)+F + G;

[0019]

[0020] where,

[0021] K is the Boltzmann constant;

[0022] T is the temperature constant, taking 290 K;

[0023] B is the radar signal bandwidth;

[0024] F is the receiving link noise figure;

[0025] G is the total gain of the receiving link;

[0026] F n is the noise figure of the nth device in the receiving link;

[0027] G n-1 is the noise figure of the n-1th device in the receiving chain.

[0028] According to at least one embodiment of the present application, in the above-mentioned radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient, IM3=3*Pout-2*OIP3;

[0029]

[0030] in,

[0031] Pout is the input power of AD terminal;

[0032] OIP3 is the total third-order intercept point of the receiving link;

[0033] OIP3 n is the third-order intermodulation point of the nth device in the receiving chain;

[0034] G n-1 is the noise figure of the n-1th device in the receiving chain.

[0035] According to at least one embodiment of the present application, in the above-mentioned radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient, the correction amount Δ corrects the third-order intermodulation product IM3 of the receiving link;

[0036] Δ is -3 to -5dBm.

[0037] This application has at least the following beneficial technical effects:

[0038] The invention provides an AGC allocation method for a radar receiving link based on third-order intermodulation and noise coefficient. In specific applications, the method can select an optimal AGC allocation combination according to the radar working state and the real-time data of the AGC control value requirement, and adjust the gain value of the multi-stage attenuator of the receiving link in real time, so that the third-order intermodulation component of the radar system can meet the false alarm rate index while minimizing the noise coefficient of the radar system. The method can perform AGC optimization allocation in real time in FPGA under different radar system working states, so as to achieve the effect of fast and real-time optimization of radio frequency link indicators. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of a radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient provided in an embodiment of the present application.

[0040] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. In addition, the drawings are only used for illustrative purposes and should not be construed as limitations on the present application. DETAILED DESCRIPTION

[0041] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be described in further detail in detail and in detail with reference to the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design.

[0042] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application shall have the usual meanings understood by those of ordinary skill in the art to which this application belongs. The words used in the description of this application to indicate orientation are only used to indicate relative directions or positional relationships. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. The word "include" used in the description of this application indicates that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0043] In addition, it should be noted that, unless otherwise clearly specified and limited, the words "installation", "connection" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Technical personnel in the field can understand its specific meaning in this application according to the specific circumstances.

[0044] The pulse Doppler radar calculates the AGC control value of the receiving link by the maximum value of AD sampling, and distributes it to each attenuator of the receiving link according to certain criteria, usually according to the following empirical method:

[0045] When the receiving link attenuation is mainly located at the back end of the link, the system noise factor is optimal;

[0046] When the attenuation of the receiving link is mainly located at the front end of the link, the third-order intermodulation effect of the system is minimal.

[0047] The embodiment of the present application provides a radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient, such as Figure 1 shown.

[0048] Design of the radar receiving link third-order intermodulation and noise coefficient optimization conditions are as follows:

[0049] GFFT-R <TN-IM3……(1)

[0050] in,

[0051] GFFT is the radar pulse accumulation point gain;

[0052] R is the detection threshold, usually 13dB;

[0053] TN is the thermal noise at the AD end;

[0054] IM3 is the third-order intermodulation product of the receive chain.

[0055] GFFT=10·lg(M)……(2)

[0056] in,

[0057] M is the number of radar pulse accumulation points.

[0058] TN=10lg(KTB)+F+G……(3)

[0059] in,

[0060] K is the Boltzmann constant;

[0061] T is the temperature constant, usually 290K;

[0062] B is the radar signal bandwidth;

[0063] F is the noise factor of the receiving link;

[0064] G is the total gain of the receiving link.

[0065]

[0066] in,

[0067] F n is the noise figure of the nth device in the receiving chain;

[0068] G n-1 is the noise figure of the n-1th device in the receiving chain.

[0069] IM3=3*Pout-2*OIP3……(5)

[0070] in,

[0071] Pout is the input power of AD terminal;

[0072] OIP3 is the total third-order intercept point of the receiving link.

[0073]

[0074] in,

[0075] OIP3 n is the third-order intermodulation point of the nth device in the receive chain.

[0076] Step 1: According to the radar operating state and the AGC control value requirements, traverse each AGC allocation combination, and calculate the corresponding radar pulse integration point gain GFFT, the thermal noise TN at the AD end, and the third-order intermodulation product IM3 of the receiving link.

[0077] Different radar operating states correspond to different radar pulse integration points M, detection thresholds R, signal bandwidths B, input signal power Pout at the AD end, etc.

[0078] Step 2: Determine whether there is an AGC allocation combination that satisfies the condition GFFT - R < TN - IM3.

[0079] With the total third-order intercept point OIP3 of the receiving link fixed, due to the unequal powers of the two double-tone signals received by the radar, the actual value of the third-order intermodulation product IM3 of the receiving link will decrease, resulting in an increase in TN - IM3. It is necessary to correct the third-order intermodulation product IM3 of the receiving link. The correction amount Δ is -3 to -5 dBm, and the above judgment condition becomes GFFT - R < TN - (IM3 + Δ).

[0080] The radar pulse integration point M can take 4096 at long distances, 512 at medium distances, and 128 at short distances.

[0081] The total AGC attenuation is 0:2:64. If the maximum value of the total AGC value that satisfies the condition is Max_AGC_Total, then the range of the total AGC value in the AGC allocation combination is 0:2:Max_AGC_Total.

[0082] Step 3: If there is an AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, then use the AGC allocation combination with the smallest noise figure F of the receiving link as the optimal AGC allocation combination.

[0083] Step 4: If there is no AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, then use the AGC allocation combination corresponding to the largest TN - IM3 as the optimal AGC allocation combination to reduce the false alarm rate.

[0084] AGC allocation combinations with a total AGC attenuation value range of Max_AGC_Total + 2:2:64.

[0085] Step 5: Change the radar operating state and the AGC control value requirements, and repeat the above Steps 1 to 4 to obtain the optimal AGC allocation combinations under different radar operating states and total AGC attenuation requirements.

[0086] The radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient disclosed in the above embodiment can select the optimal AGC allocation combination according to the radar working state and the real-time data of the AGC control value requirement in specific applications, and adjust the gain value of the multi-stage attenuator of the receiving link in real time, so that the third-order intermodulation component of the radar system can meet the false alarm rate index while minimizing the radar system noise coefficient, and can perform AGC optimization allocation in real time in FPGA under different radar system working states, so as to achieve the effect of fast and real-time optimization of RF link indicators. The AGC control value requirement can be selected according to the radar AD input signal power, with reference to radar waveform parameters, beamforming channel and other parameters.

[0087] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. In the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0088] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A radar receiving link AGC allocation method based on third-order intermodulation and noise coefficient, characterized in that: Including: Step 1: According to the radar working state and the AGC control value requirement, traverse each AGC allocation combination, and calculate the corresponding radar pulse accumulation point gain GFFT, AD - side thermal noise TN, and third - order intermodulation product IM3 of the receiving link; Step 2: Determine whether there is an AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, where R is the detection threshold; Step 3: If there is an AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, then take the AGC allocation combination with the smallest receiving - link noise figure F among them as the optimal AGC allocation combination; Step 4: If there is no AGC allocation combination that satisfies the condition GFFT - R < TN - IM3, then take the AGC allocation combination corresponding to the largest TN - IM3 among them as the optimal AGC allocation combination; Step 5: Change the radar working state and the AGC control value requirement, and repeat the above Steps 1 - 4 to obtain the optimal AGC allocation combinations under different radar working states and AGC total attenuation requirements.

2. The radar receiving - link AGC allocation method based on third - order intermodulation and noise figure according to claim 1, characterized in that GFFT = 10·lg(M); where M is the radar pulse accumulation point number, taking 4096 at long distance, 512 at medium distance, and 128 at short distance.

3. The radar receiving - link AGC allocation method based on third - order intermodulation and noise figure according to claim 1, characterized in that R takes 13 dB.

4. The radar receiving - link AGC allocation method based on third - order intermodulation and noise figure according to claim 1, characterized in that TN = 10lg(KTB)+F + G; where K is the Boltzmann constant; T is the temperature constant, taking 290 K; B is the radar signal bandwidth; F is the receiving - link noise figure; G is the total gain of the receiving link; F n is the noise figure of the nth device in the receiving chain; G n-1 is the noise figure of the n-1th device in the receiving chain.

5. The radar receiving - link AGC allocation method based on third - order intermodulation and noise figure according to claim 1, characterized in that IM3 = 3*Pout - 2*OIP3; where Pout is the AD - side input power; OIP3 is the total third - order intermodulation point of the receiving link; OIP3 n is the third-order intermodulation point of the nth device in the receiving chain; G n-1 is the noise figure of the n-1th device in the receiving chain.

6. The radar receiving - link AGC allocation method based on third - order intermodulation and noise figure according to claim 1, characterized in that The correction amount Δ corrects the third - order intermodulation product IM3 of the receiving link; Δ takes - 3 to - 5 dBm.

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