Disclosure of Invention
The purpose of the invention is as follows: the optimal radio frequency stealth power distribution method for the bistatic radar in the frequency spectrum coexistence environment is provided, the total transmitting power of a bistatic radar system can be effectively reduced, and the radio frequency stealth performance of the bistatic radar system is effectively improved.
The method considers a bistatic radar system consisting of a monostatic radar and a communication base station, the communication base station transmits communication signals which can be received by a radar receiver through target scattering, namely when the radar receiver works, the receiver simultaneously receives a scattered echo of a radar detection target and a target echo of omnidirectional radiation of the communication base station. In a bistatic radar system, the communication base station can be regarded as a radar transmitter. Acquiring a radar-target-communication base station path response, a radar-target-radar path response and a communication base station-target-radar path response according to the prior knowledge; on the basis, the estimation precision of the specified radar target time delay and the service quality of the communication base station are met as constraint conditions, the minimum bistatic radar total transmitting power is used as an optimization target, an optimal radio frequency stealth power distribution model of the bistatic radar in a spectrum coexistence environment is established, and sub-carrier distribution is optimized in a self-adaptive and overall mode, so that the minimum bistatic radar total transmitting power is achieved, and the purpose of improving the radio frequency stealth performance of the system is achieved.
The technical scheme is as follows: in order to realize the purpose, the invention adopts the following technical scheme:
the invention aims at a bistatic radar system formed by a monostatic radar and a communication base station, and the communication base station can be regarded as a radar transmitter. And according to the priori knowledge, acquiring path response, and respectively constructing a Claramen-Rou lower bound representing the estimation precision of the bistatic radar target time delay and a channel capacity expression of the service quality of the communication base station. Meanwhile, an optimal radio frequency stealth power distribution model of the bistatic radar under the spectrum coexistence environment is established by taking the time delay estimation precision meeting the specified radar target and the service quality of the communication base station as constraint conditions and taking the total emission power of the minimum bistatic radar as an optimization target. The radar subcarrier power distribution scheme obtained by solving the optimization model can adaptively optimize the radar transmitting power distribution on each subcarrier under the condition of meeting a certain radar target time delay estimation precision threshold and a communication base station channel capacity threshold, and the solution obtained by adopting standard linear programming is the radar transmitting power on each subcarrier. The method specifically comprises the following steps:
the bistatic radar optimal radio frequency stealth power distribution method under the spectrum coexistence environment comprises the following steps:
(1) determining a bistatic radar system model and environment prior knowledge;
(2) respectively deducing a Claimei-Rou lower bound expression for representing the radar target time delay estimation precision and a channel capacity expression for representing the service quality of a communication base station;
(3) estimating the precision threshold delta according to the preset radar target time delayCRLBAnd channel capacity threshold CsetEstablishing an optimal radio frequency stealth power distribution model of the bistatic radar in a spectrum coexistence environment;
(4) and (4) solving the bistatic radar optimal radio frequency stealth power distribution model in the spectrum coexistence environment in the step (3) by adopting a linear programming method.
Further, in the step (1), a bistatic radar system formed by a monostatic radar and a communication base station is considered, the communication base station transmits communication signals to be received by a radar receiver through target scattering, namely when the radar receiver works, the receiver simultaneously receives a scattered echo of a radar detection target and a target echo radiated by the communication base station in an omnidirectional manner; in a bistatic radar system, a communication base station is regarded as a radar transmitter; according to the prior knowledge of the environment, the response h of the radar-target-radar path A on the nth subcarrier is obtainedA,nResponse h of communication base station-target-radar path BB,nAnd response h of radar-target-communication base station path CC,n。
Further, in the step (2), a Clarmet-Luo lower bound is adopted to represent the target time delay estimation precision of the bistatic radar system, and the expression is as follows:
CRLBJS(τ)=FIJS(τ)-1 (1);
in the formula, τ is the target time delay, and since the fisher information is the inverse of the lower cramer-lo bound, the expression of the lower cramer-lo bound of the target time delay estimation accuracy of the bistatic radar system is as follows:
in the formula, n is an orthogonal frequency division multiplexing radar emission waveform subcarrier index; n is the number of sub-carriers of the OFDM radar transmission signal;
is the background noise power; Δ f is the subcarrier frequency spacing; | α
r,n|
2Representing the radar transmission power on the nth subcarrier; | α
c,n|
2Representing the communication base station transmission power on the nth subcarrier; mu.s
A,nRepresenting the gaussian mean on the nth subcarrier of path a; mu.s
B,nRepresenting the gaussian mean on the nth subcarrier of path B;
representing the operation of the real part; (.)
*Represents a conjugate operation; h is
A,nRepresents the response of the radar-target-radar path A on the nth sub-carrier, h
B,nRepresents the response of the communication base station-target-radar path B;
the channel capacity of the communication base station is adopted to represent the service quality of the communication base station in the bistatic radar system, and the expression is as follows:
in the formula, Pr,n=|αr,n|2Representing the radar transmission power on the nth subcarrier; pc,n=|αc,n|2Representing the communication base station transmission power on the nth subcarrier; h isC,nIndicating the response of the radar-target-communication base station path C.
Further, in the step (3), the optimal radio frequency stealth power distribution model of the bistatic radar in the spectrum coexistence environment is as follows:
wherein, Pr,n=|αr,n|2Representing the radar transmission power on the nth subcarrier; n is the number of sub-carriers of the OFDM radar transmission signal; deltaCRLBRepresenting a time delay estimation precision threshold of a radar target; csetRepresents a channel capacity threshold; CRLBJS(τ) represents a Cramer-Row lower bound on target delay estimation accuracy for the bistatic radar system; cnIndicating the channel capacity of the communication base station;
the first constraint condition indicates that the target time delay estimation accuracy Clarame-Row lower bound of the bistatic radar system cannot be larger than a given Clarame-Row lower bound threshold value so as to meet the preset target time delay estimation accuracy requirement; the second constraint condition indicates that the channel capacity of the communication base station should not be less than the set channel capacity threshold value to ensure the service of the communication base stationQuality; the third constraint condition represents that the upper limit of the transmitting power of each radar subcarrier is PmaxThe lower limit is 0.
Further, in the step (4), the bistatic radar optimal radio frequency stealth power distribution model established in the step (3) under the spectrum coexistence environment is simplified, that is, the following steps are performed:
wherein h is
C,nIndicating the response, P, of the radar-target-communication base station path C
c,n=|α
c,n|
2Represents the communication base station transmission power on the nth subcarrier,
as background noise power, C
setRepresents a channel capacity threshold;
meanwhile, the inverse of the lower bound of Cramer-Rao, namely the Fisher information, is used for representing the estimation precision of the target time delay, so that the optimal radio frequency stealth power distribution model of the bistatic radar in the spectrum coexistence environment equivalently converts into:
wherein, Pr,n=|αr,n|2Representing the radar transmission power on the nth subcarrier; n is the number of sub-carriers of the OFDM radar transmission signal; Δ f is the subcarrier frequency spacing; n is the subcarrier index of the emission waveform of the orthogonal frequency division multiplexing radar; h isA,nRepresents the response of the radar-target-radar path A on the nth sub-carrier, hB,nRepresents the response of the communication base station-target-radar path B; deltaCRLBRepresenting a time delay estimation precision threshold of a radar target; pmaxRepresenting the upper limit of the radar subcarrier transmitting power;
since the formula (6) is a non-convex problem, a standard linear programming method is adopted to solve, and the obtained solution is the radar transmitting power on each subcarrier.
Has the advantages that: compared with the prior art, the invention has the following beneficial effects:
(1) the invention provides a bistatic radar optimal radio frequency stealth power distribution method under a frequency spectrum coexistence environment, which is mainly used for acquiring the response of a radar-target-radar path A, the response of a communication base station-target-radar path B and the response of a radar-target-communication base station path C on a subcarrier in a bistatic radar system according to prior knowledge; on the basis, the estimation precision of the time delay of the specified radar target and the service quality of the communication base station are met as constraint conditions, the minimum total emission power of the bistatic radar is used as an optimization target, an optimal radio frequency stealth power distribution model of the bistatic radar in the spectrum coexistence environment is established, and the radar emission power distribution on each subcarrier is adaptively optimized, so that the total emission power of the bistatic radar is minimized, and the purpose of effectively improving the radio frequency stealth performance of the system is achieved.
The method has the advantages that the requirements of the time delay estimation precision of the given radar target and the service quality of the communication base station are met, the total transmitting power of the bistatic radar is effectively reduced, and the radio frequency stealth performance of the system is improved. The reason for the advantage is that the optimal radio frequency stealth power distribution method of the bistatic radar in the frequency spectrum coexistence environment is adopted, the time delay estimation precision of the specified radar target and the service quality of the communication base station are met as constraint conditions, the total emission power of the minimum bistatic radar is used as an optimization target, and the optimal radio frequency stealth power distribution model of the bistatic radar in the frequency spectrum coexistence environment is established. By solving the power distribution scheme of the radar subcarriers obtained by the optimization model, the radar transmitting power distribution on each subcarrier can be adaptively optimized under the condition of meeting a certain radar target time delay estimation precision threshold and a certain communication base station channel capacity threshold, so that the total transmitting power of the bistatic radar is minimized, and the aim of improving the radio frequency stealth performance of the system is fulfilled.
(2) Compared with the prior art, the optimal radio frequency stealth power distribution method for the bistatic radar in the frequency spectrum coexistence environment not only guarantees the radar target detection performance and the service quality requirement of the communication base station, but also effectively improves the radio frequency stealth performance of the system.
Detailed Description
The technical solution of the present invention is further explained with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the method for allocating optimal radio-frequency stealth power of bistatic radar in spectrum coexistence environment of the present invention includes the following steps:
1. determining a bistatic radar system model and environment prior knowledge:
considering a bistatic radar system composed of a monostatic radar and a communication base station, the model diagram of the system is shown in fig. 2, the communication base station transmits communication signals which can be received by a radar receiver through target scattering, namely when the radar receiver works, the receiver simultaneously receives a scattered echo of a radar detection target and a target echo radiated by the communication base station in an omnidirectional manner. In a bistatic radar system, the communication base station can be regarded as a radar transmitter. According to the prior knowledge of the environment, the response h of the radar-target-radar path A on the nth subcarrier is obtainedA,nResponse h of communication base station-target-radar path BB,nAnd response h of radar-target-communication base station path CC,n。
2. Respectively deducing a Clarmet-Rou lower bound expression for representing the radar target time delay estimation precision and a channel capacity expression for representing the service quality of a communication base station, as follows:
the time delay estimation precision of the radar target is represented by a Clarame-Luo lower bound, and the expression is as follows:
CRLBJS(τ)=FIJS(τ)-1(1);
in the formula, FIJS(τ)-1Denotes the CrLB lower Cramer-Lou boundaryJSAnd (tau) represents the estimation precision of the radar target time delay, and tau is the target time delay. Since the fischer information is the inverse of the lower cramer-lo bound, the lower cramer-lo bound expression that characterizes the accuracy of the radar target time delay estimation is:
in the formula, n is an orthogonal frequency division multiplexing radar emission waveform subcarrier index; n is the number of sub-carriers of the OFDM radar transmission signal;
is the background noise power; Δ f is the subcarrier frequency spacing; | α
r,n|
2Representing the radar transmission power on the nth subcarrier; | α
c,n|
2Representing the communication base station transmission power on the nth subcarrier; mu.s
A,nRepresenting the gaussian mean on the nth subcarrier of path a; mu.s
B,nRepresenting the gaussian mean on the nth subcarrier of path B;
representing the operation of the real part; (.)
*Representing a conjugate operation.
The channel capacity is adopted to represent the service quality of a communication base station in the bistatic radar system, and the expression is as follows:
in the formula, Pr,n=|αr,n|2Representing the radar transmission power on the nth subcarrier; pc,n=|αc,n|2Representing the communication base station transmit power on the nth subcarrier.
3. Estimating the precision threshold delta according to the preset radar target time delayCRLBAnd channel capacity threshold CsetEstablishing an optimal radio frequency stealth power distribution model of the bistatic radar in a spectrum coexistence environment, which is as follows:
the first constraint condition represents that the Clarmet-Row lower bound representing the radar target time delay estimation precision cannot be larger than a given Clarmet-Row lower bound threshold value so as to meet the preset radar target time delay estimation precision requirement; the second constraint condition indicates that the channel capacity of the communication base station should not be less than the set channel capacity threshold value so as to ensure the service quality of the communication base station; the third constraint represents that the upper limit of the radar transmission power on the nth subcarrier is PmaxThe lower limit is 0.
4. And (3) solving the bistatic radar optimal radio frequency stealth power distribution model (4) in the spectrum coexistence environment established in the step (3) by adopting a linear programming method.
Simplifying the bistatic radar optimal radio frequency stealth power distribution model (4) in the spectrum coexistence environment, namely:
meanwhile, the inverse of the lower bound of the Cramer-Rao, namely the Fisher information is used for representing the estimation precision of the target time delay, so that the optimal radio frequency stealth power distribution model (4) of the bistatic radar in the spectrum coexistence environment can be equivalently converted into the following steps:
because the optimization model formula (6) is a non-convex problem, a standard linear programming method can be adopted for solving, and the obtained solution is the radar transmitting power on each subcarrier.
5. Simulation result
Assume that the parameters in step 2 are as shown in table 1.
Table 1 simulation parameter settings
The communication base station transmitting power is shown in fig. 3, the response of the radar-target-radar path a is shown in fig. 4, the response of the communication base station-target-radar path B is shown in fig. 5, the response of the radar-target-communication base station path C is shown in fig. 6, the optimal radio frequency stealth power distribution result of the bistatic radar system is shown in fig. 7, and the most effective radio frequency stealth power distribution result of the monostatic radar system is shown in fig. 8. As can be seen from fig. 7 to 8, the total radar transmission power of the bistatic radar system is significantly reduced by the optimal radio frequency stealth power allocation method, compared with the most available radio frequency stealth power allocation method of the monostatic radar system. With the help of the communication base station, the radio frequency stealth performance of the bistatic radar system is obviously improved. The total radar transmit power ratio for the different power allocation algorithms is shown in fig. 9. Under the condition that external conditions are not changed, the minimum radar transmitting power can be obtained by the bistatic radar optimal radio frequency stealth power distribution method under the spectrum coexistence environment, and therefore the best radio frequency stealth performance is obtained. The communication base station in the bistatic radar system contributes to the estimation accuracy of the radar target, and the optimal radio-frequency stealth power distribution method of the bistatic radar under the spectrum coexistence environment comprehensively considers prior information such as path response. The average power distribution method only distributes the radar transmitting power evenly on the transmittable subcarriers, and does not consider the path response quality of the subcarriers.
According to the simulation result, the optimal radio-frequency stealth power distribution method of the bistatic radar under the frequency spectrum coexistence environment can adaptively optimize the radar transmission power distribution on each subcarrier by taking the total transmission power of the bistatic radar as an optimization target when certain radar target time delay estimation precision and the service quality of a communication base station are met as constraint conditions, so that the total transmission power of the bistatic radar is minimized, and the purpose of effectively improving the radio-frequency stealth performance of the system is achieved.
The working principle and the working process of the invention are as follows:
the invention firstly considers a bistatic radar system formed by a monostatic radar and a communication base station, the communication base station transmits communication signals which can be received by a radar receiver through target scattering, namely, when the radar receiver works, the receiver simultaneously receives the scattered echo of a radar detection target and the target echo of the omnidirectional radiation of the communication base station. In a bistatic radar system, the communication base station can be regarded as a radar transmitter. Then according to prior knowledge, obtaining path response, and respectively constructing a Clarmet-Rou lower bound representing the radar target time delay estimation precision and a channel capacity expression of the communication base station service quality; on the basis, the bistatic radar optimal radio frequency stealth power distribution method under the spectrum coexistence environment takes the time delay estimation precision and the service quality of a communication base station which meet the requirements of a specified radar target as constraint conditions, takes the total emission power of the minimum bistatic radar as an optimization target, and establishes a bistatic radar optimal radio frequency stealth power distribution model under the spectrum coexistence environment. By solving the radar subcarrier power distribution scheme obtained by the optimization model, the radar transmitting power distribution of each subcarrier can be adaptively optimized under the condition of meeting a certain radar target time delay estimation precision threshold and a certain communication base station channel capacity threshold. And finally, solving by adopting a standard linear programming method, wherein the obtained solution is the radar transmitting power on each subcarrier.