WO2019200663A1 - Beam control method based on frequency diversity array antenna - Google Patents

Abstract

Provided by the present invention are a beam control method based on a frequency diversity array antenna, comprising: establishing a random frequency offset antenna array transmission signal model by configuring a transmission frequency offset of each antenna array element transmission signal in an antenna array to be distributed uniformly; calculating, according to spatial position information of a desired target, a receiving signal model at a desired target spatial position; calculating a weight coefficient of each antenna element in the antenna array according to the receiving signal model; and controlling, according to the weight coefficient of each antenna element, the transmission of each antenna array element transmission signal so as to form a beam. In the method provided by the present invention, frequency offsets are configured to be distributed uniformly on the basis of a traditional frequency diversity antenna, thus the periodicity of distance dimensions during a beam transmission process of the antenna array elements may be effectively eliminated, thereby enhancing the signal receiving power at the target.

Description

Beam control method based on frequency diversity array antenna Technical field

The invention relates to a beam control method based on a frequency diversity array antenna, and relates to the technical field of antenna arrays.

Background technique

In the traditional satellite navigation carrier phase real-time dynamic differential (RTK, Real Time Kinematic) technology, the base station transmitting station usually adopts an ordinary omnidirectional antenna. Therefore, the anti-interference ability of the base station transmitting antenna is weak, and there is no directional gain function. If a phased array antenna is used, the antenna beam and the pointing shape can be quickly and flexibly changed in a set airspace, so that the gain in the desired target direction is maximized, and a null can be formed at the interference, thereby reducing the gain at the interference.

However, with the rapid development of interference technology, phased array antennas have gradually received challenges. When the main lobe interference occurs, that is, the interference signal angle is the same as or close to the transmission signal angle, the phased array antenna will not be able to distinguish the desired signal from the interference signal, thereby suppressing the reception of the desired signal. With the development of array signal processing theory and technology, the emergence of frequency diversity array antennas has brought new ideas to solve the main lobe interference. The literature "P.Antonik, MCWicks, HDGriffiths, and CJBaker, "Frequency diverse array radars," Proc. IEEE Radar Conf., pp. 215-217, Apr. 2006" was first proposed at the 2016 International Radar Conference. The concept of frequency diversity array antennas has since attracted the attention of many scholars in the radar field.

The Frequency Dividing Array Antenna (FDA) introduces a linear frequency increment far smaller than the carrier frequency in the signal transmitted by each array element, so that the transmission frequencies of the antenna elements are different. Different from the traditional phased array, the frequency diversity array antenna can generate the steering vector which is two-dimensionally related to the angle and the distance by using the small frequency offset between the array elements, so that the beam pattern of the two dimensions of the airspace-distance domain can be formed. If the main lobe interference occurs, the difference between the desired signal and the interference signal to the target can be utilized, so that the main dimension interference suppression can be effectively realized by using the distance dimension zero point of the transmission pattern of the frequency diversity array antenna. However, this conventional frequency diversity array antenna pattern has a periodic characteristic in the distance dimension, thereby reducing the received signal power at the target. In 2015, scholars W.Khan, IMQureshi, and S.Saeed Frequency (Diverse array radar with logarithmically increasing frequency offset, IEEE Antennas Wireless Propag. Lett., vol. 14, pp. 499-502, Feb, 2015) A logarithmic frequency offset FDA antenna is proposed. This approach designs the frequency offset to be in the form of a logarithmic distribution to eliminate periodicity in the FDA pattern distance dimension. However, the main pattern of the pattern formed by this method is wider, which amplifies the noise power, thereby reducing the signal-to-interference ratio of the FDA antenna output.

Therefore, the prior art needs further improvement.

Summary of the invention

In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a user with a frequency diversity array antenna-based beam control method, which overcomes the periodic defect in the beam emission distance dimension in the prior art, and enhances the target location. Signal reception power.

The invention provides a beam control method based on a frequency diversity array antenna, which comprises:

Step A: setting a transmission frequency offset of each antenna array element in the antenna array to a uniform distribution, and establishing a random frequency offset antenna array transmission signal model;

Step B: Calculate a received signal model at the desired target spatial location according to spatial location information of the desired target;

Step C: Obtain a steering vector of the antenna array transmit signal reaching the desired target spatial position according to the received signal model, and calculate a weight coefficient of each antenna array element in the antenna array according to the steering vector;

Step D: According to the weight coefficient of each antenna element, control the transmission of the signal of each antenna element to form a beam.

The random frequency offset antenna array transmitting signal model in step A is:

Where x _m (t) represents the transmitted signal at time t on the mth antenna element, w _m represents the weight coefficient on the mth antenna element, (·) ^H represents conjugate transpose, and t represents signal At the time of transmission, T represents the signal transmission interval; f _m represents the carrier frequency of the transmitted signal on the mth antenna element.

The transmit signal carrier frequency is expressed as:

f _m =f ₀ +δ _m Δf,m=0,1,...,M-1;

Where f ₀ is the reference carrier frequency, Δf is a fixed carrier frequency offset, Δf is much smaller than f ₀ , and δ _m ～ U(0, 1) is expressed as a uniform distribution between 0 and 1.

The received signal model at the desired target spatial location in step B is:

Where c represents the speed of light, R ₀ and θ ₀ represent the distance and angle of arrival of the desired target spatial position to the reference array element of the antenna array, respectively, and R _m represents the distance at which the desired target spatial position reaches the mth antenna element.

The weight coefficients of the respective antenna array elements calculated according to the steering vector in step C are:

Where w _m is the weight coefficient on the mth antenna element, d is the spacing between two adjacent antenna elements, and λ ₀ is the wavelength of the reference signal.

The method provided by the present invention is based on the fact that the frequency diversity array antenna is a conventional FDA antenna, and the frequency offset is set to a uniform distribution, which can effectively eliminate the periodicity in the distance dimension of the antenna array element beam transmission process. Thereby enhancing the signal reception power at the target.

DRAWINGS

1 is a flow chart showing the steps of a beam diversity array antenna based beam steering method provided by the present invention;

2 is a prior art frequency diversity array beam pattern;

3 is a beam pattern obtained in the beam steering method provided by the present invention.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Since the traditional FDA antenna frequency shift is in a uniformly increasing form, the FDA array pattern will appear periodic in the distance dimension, resulting in multiple main lobes affecting the signal received power at the actual target. To solve this problem, the invention employs a random frequency offset method.

The embodiment provided by the present invention is a beam control method based on a frequency diversity array antenna. As shown in FIG. 1 , the steps of the beam control method include:

Step S1: setting a transmission frequency offset of each antenna array element in the antenna array to a uniform distribution, and establishing a random frequency offset antenna array transmission signal model.

For the traditional FDA antenna station, assuming that there are M antenna elements, using a uniform line array, the carrier frequency of the transmitted signal on the mth antenna element is:

f _m =f ₀ +(m-1)·Δf,m=1,2,...,M (1)

In the above formula, f ₀ is the reference carrier frequency, Δf is a fixed carrier frequency offset, and Δf is negligible compared to f ₀ . It should be noted that Δf will affect the pattern distribution of the frequency diversity antenna in the distance dimension.

Since the traditional FDA antenna frequency shift is in a uniformly increasing form, the FDA array pattern will appear periodic in the distance dimension, resulting in multiple main lobes affecting the signal received power at the actual target. To solve this problem, the invention employs a random frequency offset method.

In the present invention, the uniform line matrix method of M array elements is also used, and the carrier frequency of the transmitted signal on the mth antenna array element is expressed as:

f _m =f ₀ +δ _m ·Δf,m=0,1,...,M-1 (2)

In the above formula, δ _m to U (0, 1) are expressed as a uniform distribution between 0 and 1.

The transmitted signal of the mth antenna element at time t can be expressed as:

In the above formula, w _m represents the weight coefficient on the mth antenna element, (·) ^H represents the conjugate transposition operation, t represents the signal transmission timing, and T represents the signal transmission interval.

Step S2: Calculate a received signal model at the desired target spatial location according to spatial location information of the desired target.

If a distant target arrives at the array antenna reference element (m=0) at a distance of R ₀ and the arrival angle is θ ₀ , the distance at which the target reaches the mth antenna is expressed as:

R _m =R ₀ +md sinθ ₀ m=1,2,...,M-1 (4)

In the above formula, d is the spacing between two adjacent elements, expressed as:

In the above formula, c represents the speed of light.

Therefore, the target received signal model can be expressed as:

Bring formula (4) into formula (6) and get

In the above formula, λ ₀ is the wavelength of the reference signal,

Observing the last term in equation (7), the δ _{m m} Δfd sin θ _{0 is} much smaller than the denominator c. Therefore, by ignoring the term, the target received signal model can be obtained as:

Step S3: Calculate a received signal model at the desired target spatial location according to spatial location information of the desired target.

In order to be able to form the main lobe at the desired target (distance R ₀ , arrival angle θ ₀ ), the weight coefficients on the array antenna elements need to be designed. First, according to equation (8), we can get the steering vector at which the array antenna transmits a signal to the target.

Then based on the spatial matching filtering criteria, ie

w ^H a(R ₀ ,θ ₀ )=M (10)

In the above formula, the vector w=[w ₀ , w ₁ , . . . , w _M-1 ] ^H is the array antenna weight coefficient. Thereby, the weight coefficient on the mth antenna element element can be obtained as

Step S4: Control the transmission of the signal transmission of each antenna array element according to the weight coefficient of each antenna array element to form a beam.

According to the array weight of the antenna element obtained in step S3, the transmission control of the antenna element transmitting signal is performed, and the beam can be obtained at the spatial position of the desired target.

In this step, the simulation calculation of the calculation method described in the above method is performed to obtain the pattern response of the frequency diversity array:

In the above formula, R and θ are the arbitrary distances and spatial angles that the array antenna can detect, respectively.

Bringing the formula (11) into the formula (12),

The above formula (13), that is, the beam pattern and the distance and spatial angle functions, are simulated and simulated, and a beam pattern diagram as shown in FIG. 3 can be obtained.

Based on the traditional frequency diversity array antenna technology, the present invention introduces a random frequency offset method and proposes a direction map design method based on frequency offset array. The invention introduces a random frequency offset antenna array into a satellite navigation RTK base station transmitting station, flexibly controls the direction of the RTK base station transmitting antenna, and eliminates the periodicity in the distance dimension in the FDA pattern, and enhances the signal receiving at the target. power.

In order to prove the effectiveness of the present invention, the above method was simulated and verified.

Assume that the array antenna adopts a uniform line array, the number of array elements is 10, the angle of arrival of the incident signal and the distance are 0° and 100 km, the reference carrier frequency is f ₀ =1.5 GHz, and the signal transmission interval is T=1 ms. 2 and 3 are respectively a pattern obtained by a conventional frequency diversity array beam pattern and a frequency diversity array antenna based beam control method.

As is apparent from Figures 2 and 3, both methods can form a main beam at the target. However, the main lobe of the beam pattern in Figure 2 has significant periodic characteristics in the distance dimension, while this is not the case in Figure 3, thereby enhancing the received signal power at the target.

Claims (5)

A beam control method based on a frequency diversity array antenna, comprising: Step A: setting a transmission frequency offset of each antenna array element in the antenna array to a uniform distribution, and establishing a random frequency offset antenna array transmission signal model; Step B: Calculate a received signal model at the desired target spatial location according to spatial location information of the desired target; Step C: Obtain a steering vector of the antenna array transmit signal reaching the desired target spatial position according to the received signal model, and calculate a weight coefficient of each antenna array element in the antenna array according to the steering vector; Step D: According to the weight coefficient of each antenna element, control the transmission of the signal of each antenna element to form a beam. The beam diversity array antenna-based beam control method according to claim 1, wherein the random frequency offset antenna array transmission signal model in step A is;

Where x _m (t) represents the transmitted signal at time t on the mth antenna element, w _m represents the weight coefficient on the mth antenna element, (·) ^H represents conjugate transpose, and t represents signal At the time of transmission, T represents the signal transmission interval; f _m represents the carrier frequency of the transmitted signal on the mth antenna element. The beam control method for a frequency diversity array antenna according to claim 1, wherein the carrier frequency of the transmitted signal is expressed as: f _m =f ₀ +δ _m ·Δf,m=0,1,...,M-1; Where f ₀ is the reference carrier frequency, Δf is a fixed carrier frequency offset, Δf is much smaller than f ₀ , δ _m ～ U(0, 1) is expressed as a uniform distribution between 0 and 1, and M is an antenna array. The number of yuan. The beam diversity array antenna-based beam steering method according to claim 3, wherein the received signal model at the desired target spatial location in step B is:

Where w _m represents the weight coefficient on the mth antenna element, (·) ^H represents the conjugate transpose, t represents the signal transmission time, c represents the speed of light, and R ₀ and θ ₀ represent the desired target space position, respectively. The distance and angle of arrival at the antenna array reference array element, R _m represents the distance at which the desired target spatial location reaches the mth antenna array element. The beam diversity array antenna-based beam control method according to claim 4, wherein the weight coefficients of the respective antenna array elements calculated according to the steering vector in step C are:

Where d is the spacing between two adjacent antenna elements, and λ ₀ is the wavelength of the reference signal.

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