A dynamic frequency offset-based frequency diversity array time domain beam control method

Abstract

The application discloses a frequency diversity array time domain beam control method based on dynamic frequency offset and belongs to the field of microwave and radio frequency electronic technologies. The method comprises the following steps: obtaining a transmission time window and a target angle corresponding to a target beam pointing direction in the transmission time window; in the duration of the transmission time window, based on the target angle, dynamically determining a frequency offset increment between each array element in the frequency diversity array, wherein the frequency offset increment is in inverse proportional relationship with the value of an equivalent time parameter; based on the frequency offset increment, controlling each array element of the frequency diversity array to transmit a signal of a corresponding frequency, so that the synthesized beam continuously points to the target beam pointing direction in the transmission time window. Through dynamic phase compensation, the application offsets the phase drift caused by time accumulation; meanwhile, while reducing the bandwidth requirement, the application physically eliminates beam distortion by using frequency symmetric distribution.

Description

Technical Field

[0001] This invention relates to the field of microwave and radio frequency electronics technology, and specifically to a time-domain beam control method for frequency diversity arrays based on dynamic frequency offset. Background Technology

[0002] The beamout of a traditional fixed-frequency offset frequency diversity array (FDA) suffers from distance-angle coupling. The beamout not only depends on the observation angle but is also tightly coupled with the propagation distance and time.

[0003] Existing technologies have attempted to improve the array structure. While such solutions can change the shape of the beam distribution, their parameter settings are usually static and cannot reconstruct or lock the main lobe pointing within any selected time period according to real-time detection requirements.

[0004] To overcome the shortcomings of a single FDA, some existing technologies have adopted a hybrid architecture of phased array and FDA. This approach requires the simultaneous integration of a large number of phase shifters and high-precision multi-channel frequency sources, resulting in a large system size and high cost.

[0005] On the other hand, traditional unidirectional linear indexing designs often result in the maximum frequency offset required by edge elements exceeding the operating bandwidth of ordinary frequency synthesizers. Furthermore, unidirectional increments lead to uneven array phase distribution, which can easily cause beam distortion and increase sidelobe levels, thus reducing detection resolution.

[0006] In a fixed-frequency offset FDA, the frequency offset between array elements For a fixed constant The calculation formula is:

[0007]

[0008] Therefore, with the start time Increase, window center equivalent time It also increases accordingly, because In the denominator, the frequency shift required to maintain the same angle increases as the observation time becomes later. The smaller it is, the better. Therefore, The fixed value cannot satisfy the requirement of maintaining the same pointing angle, thus causing the phenomenon of drift within the window. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention proposes a time-domain beam control method for frequency diversity arrays based on dynamic frequency offset.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A first aspect of the present invention relates to a time-domain beam control method for a frequency diversity array, comprising the following steps:

[0012] Obtain a launch time window and the target angle corresponding to the target beam pointing within that launch time window;

[0013] During the duration of the transmission time window, based on the target angle, the frequency offset increment between each element in the frequency diversity array is dynamically determined, wherein the frequency offset increment is inversely proportional to the value of an equivalent time parameter.

[0014] Based on the frequency offset increment, each element of the frequency diversity array is controlled to transmit a signal of the corresponding frequency so that the synthesized beam continuously points to the target beam within the transmission time window.

[0015] Optionally, the frequency offset increment Δf ( t It is determined by the following formula:

[0016]

[0017] in, t The current time within the launch time window. The center carrier frequency, d For the spacing between array elements, For the target angle, c At the speed of light, The equivalent time parameter;

[0018] The equivalent time parameter ;

[0019] in, This is a preset reference time;

[0020] The preset reference time The value is set to ensure that during the duration of the launch time window... The calculation result is not zero.

[0021] Optionally, the step of controlling each element of the frequency diversity array to transmit a signal of a corresponding frequency specifically includes:

[0022] Use center-aligned index For the first n Each array element is assigned a frequency offset weight, where m n = n - ( N - 1) / 2, n For array element sequence number, N The total number of array elements;

[0023] Based on the centering index and the frequency offset increment Δ ( ), determine the first n The emission frequency of each element at time t for:

[0024]

[0025] in The center carrier frequency.

[0026] Optionally, the following steps are also included:

[0027] Obtain a second transmission time window and a second target beam pointing within the second transmission time window, wherein the second transmission time window does not overlap with the transmission time window and the second target beam pointing is different from the target beam pointing;

[0028] During the duration of the second transmission time window, the steps of dynamically determining the frequency offset increment and controlling the transmission signals of each array element are repeated to ensure that the synthesized beam continuously points to the second target beam within the second transmission time window.

[0029] A second aspect of the present invention relates to a time-domain beam control system for a frequency diversity array, comprising:

[0030] The acquisition module is used to acquire a transmission time window and the target angle corresponding to the target beam pointing within the transmission time window;

[0031] The determination module is used to dynamically determine the frequency offset increment between each element in the frequency diversity array based on the target angle during the duration of the transmission time window, wherein the frequency offset increment is inversely proportional to the value of an equivalent time parameter.

[0032] And a control module, used to control each element of the frequency diversity array to transmit signals of the corresponding frequency based on the determined frequency offset increment, so that the synthesized beam continuously points to the target beam within the transmission time window.

[0033] Optionally, the determining module is configured to determine the frequency offset increment using the following formula. Δf (t) is determined by the following formula:

[0034]

[0035] in, t The current time within the launch time window. The center carrier frequency, d For the spacing between array elements, For the target angle, c At the speed of light, The equivalent time parameter;

[0036] The equivalent time parameter ;

[0037] in, This is a preset reference time;

[0038] The preset reference time The value is set to ensure that during the duration of the launch time window, The calculation result is not zero.

[0039] Optionally, the control module is configured to:

[0040] Use center-aligned index For the first n Each array element is assigned a frequency offset weight, where = n - ( N - 1) / 2, n For array element sequence number, N The total number of array elements;

[0041] Based on the centering index and the frequency offset increment Δ ( ), determine the first n Each element in time t transmission frequency ( )for:

[0042]

[0043] in The center carrier frequency.

[0044] Optionally, the acquisition module is further configured to acquire a second transmission time window and a second target beam pointing within the second transmission time window, wherein the second transmission time window does not overlap with the transmission time window and the second target beam pointing is different from the target beam pointing;

[0045] The determining module is further configured to dynamically determine the second frequency offset increment based on the direction of the second target beam during the duration of the second transmission time window;

[0046] The control module is further configured to control each element of the frequency diversity array to transmit a signal of a corresponding frequency based on the second frequency offset increment, so that the synthesized beam continuously points to the second target beam within the second transmission time window.

[0047] A third aspect of the invention relates to a computer program stored thereon, which, when executed by a processor, implements the time-domain beam control method for a frequency diversity array as described above.

[0048] A fourth aspect of the invention relates to a radar device configured with the aforementioned computer-readable storage medium and a processor for executing a computer program stored in the computer-readable storage medium.

[0049] The beneficial effects of this invention are:

[0050] The FDA time-domain directional beam theory design of this invention enables rapid angle switching and programmable scanning of the radar system beam between different time windows, enhancing the multi-target surveillance capability of the radar system. Furthermore, by using fixed frequency offset compensation, it eliminates phase deviation caused by the time dimension, ensuring that the beam is always locked at the target angle at a specific time point, thereby improving the detection gain.

[0051] Furthermore, this invention proposes a control method that causes the frequency offset to change with the reciprocal of time, namely... This achieves beam pointing lock throughout the entire time period, overcoming the problem of linear drift of the main lobe pointing over time caused by the fixed frequency offset of traditional FDA.

[0052] Finally, this invention abandons the traditional one-way linear index (0 to 1). N - 1) Introduce a centered index m n This method defines the position and frequency offset weights of array elements, thereby solving the problem of excessive bandwidth pressure on RF front-end hardware (such as mixers and filters) caused by the excessive frequency offset of edge array elements. It also corrects the problem of uneven array phase distribution caused by the unidirectional frequency offset increase, thus significantly improving the system's working stability at the nanosecond scale and reducing the risk of beam distortion. Attached Figure Description

[0053] The invention will now be further described with reference to the accompanying drawings.

[0054] Figure 1 The images show the beam heatmap and beam cross-sections at different sampling points under time-varying frequency shifts in this application; the left image is the beam heatmap with a directional angle of 30° within a time window of 5-15ns; the right image is the angular cross-section of the corresponding beam.

[0055] Figure 2This is a comparison diagram of the FDA time-domain directional beam theory optimization schemes for this application. Within the time window of 5-15ns, the directional angle is 30°. The red dashed line represents the fixed frequency offset design, which accurately points to 30° at the center of the time window. The blue solid line represents the time-varying frequency offset optimization design, which points to 30° throughout the entire time window.

[0056] Figure 3 This is a schematic diagram of the FDA time-domain multi-stage pointing switching in this application, where the left image shows the multi-stage FDA pointing switching trajectory and the right image shows a panoramic view of spatiotemporal coverage. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] In some embodiments of the present invention, a dynamic beamforming method for FDA based on time-varying frequency offset control is disclosed. This method aims to solve the problems of distance-angle coupling and the inability to flexibly control beam pointing in the time domain in traditional FDA beamforming by designing the frequency offset. Specifically, the method may include the following steps:

[0059] In some specific examples of this invention, the FDA time-domain directional beam theory analysis process is provided, including the following steps:

[0060] For a n The array factor of the FDA linear array under its narrowband approximation. It can be represented as the superposition of the signals of each array element. Ignoring common terms, its basic form is:

[0061]

[0062] in That is, the first n Phase terms of each array element.

[0063]

[0064] in, Let n be the positions of the array elements relative to the reference array element.

[0065] It can be seen that the phase term is composed of three core physical components: the spatial geometric phase term, the time-varying phase term caused by frequency shift, and the initial phase term.

[0066] 1.2 Instructions for setting relevant parameters

[0067] 1. Time parameter settings

[0068] Divide time into K A time window.

[0069] No. k The time window is: ,in This represents the duration of the time window.

[0070] Objective: Within this time window, the main lobe points to... .

[0071] In some examples of the present invention, considering that smaller frequency offsets are more conducive to the stable operation of the RF front-end, mixer, and frequency synthesizer, and reduce the requirements for device broadband linearity, centering indexes are used to reduce the maximum frequency offset. Specifically, this may include the following steps:

[0072] make:

[0073]

[0074] The frequency offset of each array element is set as follows:

[0075]

[0076] Thus, the maximum frequency shift is Compared to designs that do not use a centered index (frequency offset range is 0 to...), The method reduced the frequency offset by half.

[0077] Furthermore, the center index makes the frequency offset of the array element at the center close to 0, while the frequencies of the array elements on both sides are symmetrically distributed. This symmetrical frequency distribution helps to maintain the symmetry of the beam shape, reduce beam distortion caused by the unidirectional monotonic growth of frequency, make the main lobe more directional and the side lobe level easier to control.

[0078] 1.3 Principle of Phase Coherence Superposition

[0079] At the far-field observation point, the total field strength of the linear array is the vector sum of the radiation fields of each element.

[0080] When the waves emitted by all array elements are in a certain direction When they reach the observation point, if their phases are exactly the same, the wave crests will coincide, and the amplitude of the superimposed wave will reach its maximum value, thus forming the main lobe.

[0081] To make the main lobe point in a specific direction, the frequency offset term of each array element needs to cancel out the spatial path difference term. When the sum of these two components equals 0, the "equivalent phase gradient" of the array as a whole disappears, and the waves emitted by all array elements behave like an infinitely large plane wavefront in the specified direction, with completely consistent phase.

[0082] Therefore, in order to make the main lobe at time... t Precise pointing This requires that the phase difference between adjacent array elements be zero. Ignore the initial phase. Assuming within the time window k Inside, The phase difference between adjacent array elements is a constant. With a value of 0, the frequency offset design formula can be obtained:

[0083]

[0084] in Take the equivalent time at the center of the window, with the reference time as follows. ,Right now:

[0085]

[0086] In summary, At any given time, the frequency offset of each array element is designed according to formulas (4) and (5), and the angle is... The phase difference in direction is completely smoothed out, and the main lobe is precisely pointed to that angle, achieving angle control in a specific direction.

[0087] In other examples of the present invention, the FDA time-domain directional beam theory optimization method described above is disclosed, including the following steps:

[0088] Using window center equivalent time is equivalent This results in a directional beam reaching the center point within that time window. Because within the time window... It is changing. If Δf is fixed within the time slice, the beam pointing will be slightly offset. To ensure accurate pointing throughout the entire time window, rather than just at the center point, a theoretical optimization scheme is proposed.

[0089] In the frequency offset design process described in the above example, the equivalent time at the window center was used as an equivalent... In other examples, a time-varying frequency offset strategy is used, employing equivalent time... , To replace the original window center equivalent time, that is to Within the time window, a small frequency adjustment is performed. Thus, based on the original formula (5), a new design formula for the time-varying frequency offset can be obtained:

[0090]

[0091] This means that a frequency modulation process occurs within each time window, and this frequency modulation can firmly lock the main lobe of the beam. In terms of direction, it enables precise locking of energy at the target angle within a specific time window, achieving more accurate space-time control.

[0092] For reference time More specifically, The selection of [a specific parameter] directly controls the steepness of the frequency offset curve. When [a specific parameter] is selected, [the steepness of the curve is directly controlled]. When the frequency offset is increased, the instantaneous frequency offset amplitude required by each array element will decrease significantly because the denominator in the frequency offset design formula becomes larger. This means that increasing the frequency offset amplitude will significantly reduce the instantaneous frequency offset amplitude required by each array element. (To shift it towards a negative value, such as...) This can effectively reduce the requirements for the instantaneous bandwidth of the RF front end; The further away from the operating window, the gentler the frequency modulation slope. This reduces spectral broadening caused by frequency abrupt changes and improves the spectral purity of the signal.

[0093] In some specific embodiments of the present invention, and in the simulation verification described below, The value is 0.

[0094] In some embodiments, the beamforming method described above is verified through simulation.

[0095] Figure 1 The diagram shows the FDA beam direction and cross-section with a pointing angle of 30° within a time window of 5-15ns. Figure 2 The image shows a comparison of the FDA's time-domain directional beam optimization scheme, comparing the effects of using the optimization scheme and not using it, and intuitively demonstrating the feasibility of the optimization scheme. Figure 3 The study demonstrates the effect of the FDA's direction switching across different time windows, with the 30-40ns window, which was not optimized, showing a clear difference from other time windows.

[0096] The simulation results show that:

[0097] 1. Zero offset locking: Within a 10ns time window, the main lobe pointing standard deviation is zero through time-varying frequency offset design, successfully locking the beam at the target angle and avoiding the linear scanning target phenomenon common in fixed frequency offset design.

[0098] 2. Real-time controllable beam pointing: Through time-varying frequency modulation compensation, the directional control of the beam in different time windows was successfully realized, effectively verifying the correctness of the theory.

[0099] In summary, this invention proposes a theoretical design for FDA time-domain directional beamforming, dividing the observation time into several independent time-slice windows. By using theoretical formulas to back-calculate, the target pointing angle is accurately hit at the center of each time slice. Secondly, through the analysis of FDA beamforming theory, a target for precise control of FDA beam pointing at different time periods is proposed. Furthermore, through theoretical formula derivation, the frequency offset design formula required to achieve this target is obtained.

[0100] Through the aforementioned FDA time-domain directional beamforming theory design method, this invention solves the problem of the lack of flexible time-domain reconfiguration in beam pointing. This enables the system to adjust the beam in real time under complex battlefield environments or changing target detection requirements. Furthermore, the FDA time-domain directional beamforming theory design of this invention solves the problem of how to cancel accumulated phase differences in the time domain within any given time period to achieve high-precision steady-state beam pointing or on-demand dynamic guidance.

[0101] In practical applications, the FDA time-domain directional beam theory design of this invention enables rapid angle switching and programmable scanning of the radar system beam between different time windows, enhancing the multi-target monitoring capability of the radar system. Furthermore, by using fixed frequency offset compensation, it eliminates the phase deviation caused by the time dimension, ensuring that the beam is always locked at the target angle at a specific time point, thereby improving the detection gain.

[0102] Furthermore, this invention proposes an optimization of the FDA time-domain directional beamforming theory, specifically including:

[0103] Reference time margin design: By setting appropriate reference time points This avoids equivalent time. The problem of frequency offset numerical explosion caused when it approaches zero.

[0104] Adaptive Time-Varying Frequency Offset Strategy: A control method is proposed that makes the frequency offset vary with the reciprocal of time, i.e. This enables beam pointing lock-on throughout the entire time period.

[0105] Based on the above optimization method, this invention solves the numerical singularities that occur when calculating the frequency offset at the initial moment, and the problem of linear drift of the main lobe pointing direction over time caused by the fixed frequency offset in traditional FDA methods. This allows the beam to remain steady within a preset time period and overcomes the limitation of existing technologies that cannot perform real-time, dynamic directional control according to actual detection needs at any given time. Therefore, the optimization method of this invention has stable numerical solutions throughout the entire time period, facilitating the application of the algorithm on real-time processing platforms such as FPGAs. Simultaneously, through time-varying frequency offset compensation, it eliminates the phase accumulation deviation caused by the time dimension, ensuring that the beam is always locked at the target angle and improving detection gain.

[0106] Finally, this invention abandons the traditional one-way linear index (0 to 1). N - 1) Introduce a centered index m n This method defines the position and frequency offset weights of array elements, thereby solving the problem of excessive bandwidth pressure on RF front-end hardware (such as mixers and filters) caused by the excessive frequency offset of edge array elements. It also corrects the problem of uneven array phase distribution caused by the unidirectional frequency offset increase, thus significantly improving the system's working stability at the nanosecond scale and reducing the risk of beam distortion.

[0107] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0108] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A time-domain beam control method for a frequency diversity array, characterized in that, Includes the following steps: Obtain a launch time window and the target angle corresponding to the target beam pointing within that launch time window; During the duration of the transmission time window, based on the target angle, the frequency offset increment between each element in the frequency diversity array is dynamically determined, wherein the frequency offset increment is inversely proportional to the value of an equivalent time parameter. Based on the frequency offset increment, each element of the frequency diversity array is controlled to transmit a signal of the corresponding frequency so that the synthesized beam continuously points to the target beam within the transmission time window; The frequency offset increment Determined by the following formula: in, t The current time within the launch time window. The center carrier frequency, d For the spacing between array elements, For the target angle, c At the speed of light, The equivalent time parameter; The equivalent time parameter ; in, This is a preset reference time; The preset reference time The value is set to ensure that during the duration of the launch time window... The calculation result is not zero; The step of controlling each element of the frequency diversity array to transmit a signal of a corresponding frequency specifically includes: Use center-aligned index For the first n Each array element is assigned a frequency offset weight, where m n = n - ( N - 1) / 2, n For array element sequence number, N The total number of array elements; Based on the centering index and the frequency offset increment Determine the first n Each element in time t transmission frequency for: in The center carrier frequency.

2. The time-domain beam control method for frequency diversity arrays according to claim 1, characterized in that, It also includes the following steps: Obtain a second transmission time window and a second target beam pointing within the second transmission time window, wherein the second transmission time window does not overlap with the transmission time window and the second target beam pointing is different from the target beam pointing; During the duration of the second transmission time window, the steps of dynamically determining the frequency offset increment and controlling the transmission signals of each array element are repeated to ensure that the synthesized beam continuously points to the second target beam within the second transmission time window.

3. A time-domain beam control system for a frequency diversity array, characterized in that, include: The acquisition module is used to acquire a transmission time window and the target angle corresponding to the target beam pointing within the transmission time window; The determination module is used to dynamically determine the frequency offset increment between each element in the frequency diversity array based on the target angle during the duration of the transmission time window, wherein the frequency offset increment is inversely proportional to the value of an equivalent time parameter. And a control module, configured to control each element of the frequency diversity array to transmit a signal of a corresponding frequency based on a determined frequency offset increment, so that the synthesized beam continuously points towards the target beam within the transmission time window; The frequency offset increment Determined by the following formula: in, t The current time within the launch time window. The center carrier frequency, d For the spacing between array elements, For the target angle, c At the speed of light, The equivalent time parameter; The equivalent time parameter ; in, This is a preset reference time; The preset reference time The value is set to ensure that during the duration of the launch time window... The calculation result is not zero; The step of controlling each element of the frequency diversity array to transmit a signal of a corresponding frequency specifically includes: Use center-aligned index For the first n Each array element is assigned a frequency offset weight, where m n = n - ( N - 1) / 2, n For array element sequence number, N The total number of array elements; Based on the centering index and the frequency offset increment Determine the first n Each element in time t transmission frequency for: in The center carrier frequency.

4. The time-domain beam control system for frequency diversity arrays according to claim 3, characterized in that: The acquisition module is also used to acquire a second transmission time window and a second target beam pointing within the second transmission time window, wherein the second transmission time window does not overlap with the transmission time window and the second target beam pointing is different from the target beam pointing; The determining module is further configured to dynamically determine the second frequency offset increment based on the direction of the second target beam during the duration of the second transmission time window; The control module is further configured to control each element of the frequency diversity array to transmit a signal of a corresponding frequency based on the second frequency offset increment, so that the synthesized beam continuously points to the second target beam within the second transmission time window.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the time-domain beam control method for the frequency diversity array as described in any one of claims 1 or 2.

6. A radar device, characterized in that, The device is equipped with the computer-readable storage medium of claim 5, and a processor for executing a computer program stored in the computer-readable storage medium.

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