Gap-loaded bunching space-frequency low-correlation coding array antenna

Abstract

The invention discloses a slit-loaded bunching space-frequency low-correlation coding array antenna. A uniform feed module is used for providing an excitation electric field with power uniformly distributed in a frequency dimension for a low-correlation coding module; the low-correlation coding module is used for performing low-correlation coding on the received electromagnetic signals to generate a large number of low-correlation electromagnetic signals on discrete frequency points; the slot array radiation module is used for radiating the excitation signal modulated by the low-correlation coding module into a space in a high-efficiency and high-gain manner, and can restrain the angle of signal radiation energy; the coherent array expansion module is composed of a plurality of identical bunching space-frequency low-correlation coding array antennas loaded by single slots, and electromagnetic wave radiation with higher gain is achieved in an array integration mode. The antenna can be used for detecting multiple targets at the same time, random noise and interference are effectively restrained, miniaturization and light weight of the whole detection system are guaranteed, and the performance of a microwave correlation detection system is greatly improved.

Description

Technical Field

[0001] This application relates to the field of microwave antenna technology, and in particular to a slot-loaded spot-loaded space-frequency low-correlation coded array antenna. Background Technology

[0002] In the field of microwave imaging and radar detection technology, active electromagnetic wave illumination is typically used to achieve spatial resolution and high-precision target perception, relying on antenna systems to generate directional radiation beams. Currently, the mainstream technical solutions are mainly based on two architectures: phased array antennas and leaky wave antennas. Phased array antennas achieve electronic scanning and spatial pointing control of the beam by introducing controllable phase shifters in multiple independent channels to adjust the feed phase of each array element, and are widely used in high-resolution imaging, military radar, and communication systems. Another type of technology employs a frequency scanning mechanism, utilizing the dispersion characteristics of leaky wave antennas to continuously deflect the direction of the radiation beam with changes in the operating frequency, thus achieving frequency scanning without phase shifters. Furthermore, some research attempts to spatially modulate electromagnetic waves using coded metasurfaces or modulation structures to simplify system complexity and enhance beam control capabilities.

[0003] However, the aforementioned existing technologies still face several key challenges in practical applications. Phased array-based systems require independent phase shifters and RF channels for each array element, resulting in complex hardware structures, high costs, and significant power consumption. Furthermore, system integration becomes significantly more difficult as the array size increases. While leaky-wave antennas do not require phase shifters, their scanning range is limited by the inherent contradiction between antenna bandwidth and physical size, making it difficult to simultaneously achieve wide bandwidth and large-angle scanning. They also exhibit low radiation efficiency and unstable main lobe gain with frequency variation. In addition, the detection modes generated by traditional methods have strong correlations and limited spatial degrees of freedom, making it difficult to meet the requirements of high-resolution correlated imaging for a large number of low-correlation excitation modes. Therefore, how to construct an antenna structure capable of generating a large number of low-correlation radiation modes over a wide bandwidth, possessing good beam-focusing characteristics and scalability, without relying on complex phase-shifting networks, has become a crucial technical challenge that urgently needs to be addressed to improve the performance of microwave imaging systems. Summary of the Invention

[0004] To address the problems of large detection systems, limited imaging speed, and high power consumption in existing technologies, this application provides a slot-loaded spot-loaded spatial frequency low-correlation coded array antenna. This antenna provides the required number of spatial codes and low correlation for spatial resolution, which can reduce the complexity of the detection system, improve imaging efficiency, and reduce radar detection costs.

[0005] To achieve the above objectives, this application adopts the following technical solution: This application provides a slot-loaded focused space-frequency low-correlation coded array antenna, including: a coherent array extension module for arranging multiple identical single slot-loaded antennas at a predetermined interval to form a coherent array; The uniform feeding module is used to excite the electromagnetic signal through a single-feed standing wave structure and distribute it evenly to the subsequent modules within the working frequency band through a slot array composed of coupling slots of various different lengths, ensuring power balance and impedance matching in the frequency dimension. The low-correlation coding module is disposed on the uniform power supply module and includes a symmetrically arranged multilayer metasurface substrate. Each substrate is provided with metasurface units of different geometric structures arranged randomly. By spatially modulating the electromagnetic field to destroy the inherent resonance characteristics of the cavity, the excitation of different discrete frequencies generates uncorrelated coding responses, thereby realizing low-correlation space-frequency coding in the frequency dimension. The slot array radiation module, located above the low correlation coding module, consists of non-uniformly distributed rectangular radiation slots of various lengths and double-sided rectangular grooves. It is used to efficiently radiate the encoded electromagnetic signal into free space, forming a large number of low correlation detection beams in the azimuth plane, and using the groove structure to perform angular beam focusing constraint on the radiation energy in the elevation plane. A coherent array extension module is used to arrange multiple identical single-slot loaded antennas at predetermined intervals to form a coherent array.

[0006] This antenna can achieve wideband, multi-mode, low-correlation space detection without the need for traditional phase shifters, significantly reducing system complexity and improving imaging efficiency and integration.

[0007] As a further improvement of this application, the uniform feeding module includes a single-feed-port standing wave structure, a coupled slot array structure, and a cavity end loading structure; the single-feed-port standing wave structure uniformly transmits the fed electromagnetic wave signal to slot elements of different lengths in the coupled slot array structure; the coupled slot array structure is distributed on the single-feed-port standing wave structure and uniformly transmits the electromagnetic wave signal to the low-correlation coding module; the cavity end loading structure is used to adjust the reflection characteristics of the fed signal at the cavity end.

[0008] As a further improvement of this application, the cavity end loading structure is a short metal surface, which is set at the tail of the uniform feeding module to form a standing wave field distribution and adjust the input impedance characteristics of the entire antenna structure in the operating frequency band.

[0009] As a further improvement of this application, the low correlation coding module includes symmetrically arranged multilayer metasurface substrates, each side including at least one transmissive metasurface substrate and one reflective metasurface substrate, and each substrate is composed of metasurface units with different geometric structures randomly arranged on a dielectric substrate. As a further improvement of this application, the metasurface units are arranged non-periodically through a stochastic optimization algorithm, so that the electromagnetic response modes generated under different frequency excitations have low cross-correlation, thereby generating a large number of independent space detection modes.

[0010] As a further improvement of this application, the slot array radiation module includes a variety of rectangular radiation slots of different lengths, which are non-uniformly arranged along the long side of the antenna, and each length of slot corresponds to the radiation characteristics of a specific frequency band.

[0011] As a further improvement to this application, the rectangular radial slit is a long strip structure with semi-circular transition design at both ends.

[0012] As a further improvement of this application, the slot array radiation module also includes a double-sided rectangular slot structure disposed on both sides of the radiation surface. The double-sided rectangular slot structure generates an induced current during the radiation process, and its spatial distribution is equivalent to a one-dimensional array.

[0013] As a further improvement of this application, the radiation pattern of the radiation slot itself has narrow beam characteristics, which, together with the slot line structure, achieves dual-plane beam focusing.

[0014] As a further improvement of this application, the coherent array extension module is composed of multiple identical single-slot loaded clustered space-frequency low-correlation coded array antennas arranged at predetermined intervals to form a linear array or area array structure.

[0015] As a further improvement of this application, the coherent array extension module adjusts the wavefront phase relationship after coherent superposition by optimizing the spacing between adjacent antenna elements and the loading position of the slots in each element.

[0016] As a further improvement to this application, the antenna operates in a frequency band of 32GHz to 36GHz, with a center frequency of 34GHz.

[0017] Compared with the prior art, this application has the following technical effects: This application presents a slot-loaded focused space-frequency low-correlation coded array antenna, comprising a uniform feeding module, a low-correlation coding module, a slot array radiation module, and a coherent array extension module. The uniform feeding module provides the low-correlation coding module with an excitation electric field whose power is uniformly distributed along the frequency dimension, ensuring that the low-correlation coding capability of the low-correlation coding module is largely unaffected by the electric field strength. The low-correlation coding module, through the introduction of metasurfaces, performs low-correlation coding on electromagnetic signals, generating a large number of low-correlation electromagnetic radiation signals at discrete frequency points. The slot array radiation module efficiently and with high gain radiates the modulated signal into free space, forming a low-correlation detection mode, and can constrain the radiation angle by changing the array slot and slot line structure. The coherent array extension module, by assembling multiple single-slot-loaded focused space-frequency low-correlation coded array antennas into a coherent array, achieves higher-gain electromagnetic wave radiation. This slot-loaded, focused-beam space-frequency low-correlation coded array antenna, designed with this structure, introduces a four-module collaborative architecture of "uniform feeding—frequency coding—slot radiation—coherent extension." For the first time, it combines space-frequency coding with waveguide slot antennas, achieving wideband low-correlation detection capabilities without phase shifters. The uniform feeding module ensures balanced energy distribution across frequency components, guaranteeing coding stability. The random metasurface in the low-correlation coding module breaks traditional resonance characteristics, enabling highly uncorrelated radiation modes from different frequency excitations, significantly improving spatial resolution potential. The slot array not only performs radiation but also achieves two-dimensional angle focusing in the azimuth and elevation planes through non-uniform slot design and a double-sided slotted structure, enhancing energy concentration. Coherent array extension further improves overall gain and directivity. This solution eliminates reliance on expensive phase shifters and large-scale arrays, offering advantages such as small size, low power consumption, fast imaging speed, and strong anti-interference capabilities. It is particularly suitable for applications requiring lightweight design and real-time performance, such as millimeter-wave imaging radar, security inspection systems, and UAV-based detection platforms. By illuminating the target with a large number of low-correlation detection beams and post-processing the echo signals, object information can be obtained quickly. Based on this, the imaging system has advantages such as small physical size, fast imaging speed, and adjustable beam angle. Attached Figure Description

[0018] Figure 1 A schematic diagram of a slot-loaded beamforming space-frequency low-correlation coded array antenna structure provided in this application embodiment; Figure 2 This is a diagram showing the power supply performance of an embodiment of this application within the operating frequency band; Figure 3 This is the radiation pattern of the E-plane (elevation plane) at the main frequency (34 GHz) according to an embodiment of this application; Figure 4 This is the radiation pattern of the H-plane (azimuth plane) at the main frequency (34 GHz) according to an embodiment of this application; Figure 5This is the average radiation pattern of the H-plane (azimuth plane) within the operating frequency band of the embodiments of this application; Among them, 1 is the uniform feeding module, 2 is the low correlation coding module, 3 is the slot array radiation module, and 4 is the coherent array extension module. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0020] like Figure 1 As shown, this application provides a slot-loaded focused space-frequency low-correlation coded array antenna, which is used to realize multi-mode, low-correlation electromagnetic wave transmission and space detection in a wide bandwidth; it includes: a uniform feed module 1, a low-correlation coding module 2, a slot array radiation module 3, and a coherent array extension module 4. The uniform feed module 1 is located below the low-correlation coding module 2, and the low-correlation coding module 2 is located below the slot array radiation module 3; the coherent array extension module 4 is located below the uniform feed module 1.

[0021] The uniform feeding module 1 is an elongated rectangular cavity with various rectangular slots of different lengths loaded on top. Each slot has different resonant characteristics and is used to uniformly transmit the fed electromagnetic wave signal to the low correlation coding module 2 in each frequency dimension. The rear of the cavity of the uniform feeding module 1 is short-circuited by a metal wall to adjust the overall matching characteristics of the randomly modulated antenna loaded with a strong dispersive medium. The uniform feeding module 1 is used to provide the low correlation coding module 2 with an excitation electric field whose power is uniformly distributed in the frequency dimension and to ensure that the slot-loaded focused space-frequency low correlation coding array antenna has good impedance matching in the operating frequency band.

[0022] The low-correlation coding module 2 includes a symmetrical 6-layer metasurface substrate. Multiple different metasurface units are etched on each substrate using a random optimization algorithm. By utilizing the different resonance characteristics of different units, the fed electromagnetic wave signal is encoded with low correlation to ensure the low correlation of the modulated electromagnetic wave signal. The low-correlation coding module 2 is located between the uniform feeding module and the slot array radiation module 3. The low-correlation coding module 2 is used to encode the received electromagnetic signal with low correlation in the frequency dimension, generating a large number of low-correlation electromagnetic radiation signals at discrete frequency points.

[0023] Among them, the slot array radiation module 3 is used to efficiently and with high gain radiate the electromagnetic wave signal modulated by the low correlation coding module 2 into space, forming a low correlation detection mode, and can focus the angle of the signal radiation energy; the slot array radiation module 3 is used to efficiently and with high gain radiate the excitation signal encoded by the low correlation coding module 2 into space, forming a low correlation detection mode, and can focus the angle of the randomly radiated signal energy; the coherent array extension module 4 is used to form a coherent array by combining the focusing space-frequency low correlation coded array antennas of multiple slot radiation units to achieve higher gain electromagnetic wave radiation.

[0024] Specifically, the coupling slot array structure of the uniform feed module and the rectangular radiating slot structure of the slot array radiating module 3 are multiple long rectangular slots of different lengths, with semi-circular transition structures at the corners. The coupling slot array structure of the uniform feed module includes slots of various lengths, each of which has good feeding capability in a specific frequency band. Arranging slots of different lengths on the feed aperture achieves uniform feeding within the operating frequency band.

[0025] The uniform feeding module comprises a single-port standing wave structure, a coupled slot array structure, and a cavity end loading structure. The single-port standing wave structure uniformly transmits the fed electromagnetic wave signal to slot elements of different lengths in the coupled slot array structure, ensuring good impedance matching. The coupled slot array structure, distributed above the single-port standing wave structure, uniformly transmits the electromagnetic wave signal to the low-correlation coding module 2. The cavity end loading structure is used to adjust the reflection characteristics of the fed signal at the cavity end. The specific composition and functional division of the uniform feeding module 1 ensure uniform power distribution and good system matching within a wide bandwidth, which is a prerequisite for achieving stable coded radiation.

[0026] A further improvement lies in the fact that the loading structure at the end of the cavity is a short-circuit metal surface, located at the tail of the uniform feed module 1. This serves to generate a standing wave field distribution and adjust the input impedance characteristics of the entire antenna structure within the operating frequency band. Achieving efficient energy reflection and standing wave excitation through end short-circuiting improves feed efficiency and enhances frequency response stability, representing a key optimization technique in feed design.

[0027] Furthermore, the low correlation coding module 2 includes a symmetrical multilayer metasurface substrate. Each substrate is composed of metasurface units with different structures randomly arranged on a medium with different structures. Each side includes a transmissive metasurface substrate and a reflective metasurface substrate. The introduction of the metasurface in the low correlation coding module 2 disrupts the inherent resonant mode of the cavity, so that different low correlation coding modes can be generated when the excitation source of different frequencies is excited, and low correlation coding is generated for the signal that varies with frequency.

[0028] A further improvement lies in the fact that the low-correlation coding module 2 includes symmetrically arranged multilayer metasurface substrates, with each side comprising at least one transmissive metasurface substrate and one reflective metasurface substrate. Each substrate is composed of metasurface units with different geometric structures randomly arranged on a dielectric substrate. The layered structure and functional type of the coding module reflect its ability to coordinate and control the forward and backward propagation characteristics of electromagnetic waves, and is the core component for realizing high-degree-of-freedom space-frequency coding.

[0029] A further improvement lies in the fact that the metasurface units are arranged non-periodically through a stochastic optimization algorithm, resulting in low cross-correlation of electromagnetic response modes generated under different frequency excitations, thereby generating a large number of independent space detection modes. "Random arrangement" is not only a physical layout feature, but also the essential mechanism for achieving low-correlation encoding, which is significantly different from traditional ordered metasurface or phased array designs.

[0030] Preferably, the slot array radiation module 3 consists of rectangular slots of various lengths arranged non-uniformly on the antenna surface, which uniformly radiate the electromagnetic wave signal after low correlation encoding into free space, generating a large number of low correlation detection modes at various frequency points. By adjusting the slots, the radiation angle of the azimuth plane (long end of the antenna) can be constrained, and by adjusting the loaded double-sided rectangular slot structure, the radiation angle of the elevation plane (short end of the antenna) can be constrained.

[0031] Furthermore, the slot array radiation module 3 includes an array structure with rectangular radiation slots of different lengths and a double-sided rectangular slot structure; the slot array structure is used to radiate the randomly modulated electromagnetic signal inside the waveguide cavity into free space, forming a large number of low-correlation detection modes at different discrete frequency points; the double-sided rectangular slot structure is used to constrain the energy of the radiated electromagnetic signal at an angle.

[0032] A further improvement is that the rectangular radiation slot structure of the slot array radiation module 3 includes slots of various lengths. Each length of slot has good radiation capability in a specific frequency band. Arranging slots of different lengths on the radiation aperture achieves energy radiation uniformity in the frequency coding dimension.

[0033] A further improvement lies in the fact that the double-sided rectangular slot structure of the slot array radiation module 3 generates induced currents when radiating energy through the slots. By changing the position of the slots, it can be fitted into a spatially distributed array arrangement, thereby constraining the radiation angle of the encoded electromagnetic signal. The radiation pattern of the radiating slots themselves in the slot array radiation module 3 can further enhance the radiation angle constraint capability of the encoded electromagnetic signal. The slot array radiation module 3 includes rectangular radiating slots of various lengths, non-uniformly arranged along the long side of the antenna. Each slot length corresponds to the efficient radiation characteristics of a specific frequency band, thereby achieving uniform energy radiation in the frequency dimension. By combining the diversity of slot lengths with the arrangement strategy, radiation consistency is extended in the frequency domain, ensuring the effective output of the encoded signal throughout the entire operating bandwidth.

[0034] The rectangular radiating slot is a long strip structure with semi-circular transitions at both ends to reduce electric field concentration, minimize local losses, and improve radiation efficiency. Optimizing the slot geometry improves edge field distribution and enhances overall antenna performance and reliability, representing a highly feasible structural improvement. The slot array radiating module 3 also includes bilateral rectangular slot structures on both sides of the radiating surface. These slots generate induced currents during radiation, and their spatial distribution is equivalent to a one-dimensional array, used to angularly constrain the radiated energy in the elevation (E-plane) to achieve a beam-focusing effect. Introducing the slot structure as an angle control element eliminates the need for additional active components, achieving beam narrowing in the elevation plane and simplifying system complexity. The radiating slot's own radiation pattern has narrow beam characteristics, further enhancing the energy concentration of the encoded electromagnetic signal in the azimuth (H-plane), achieving dual-plane beam focusing in conjunction with the slot structure. Utilizing the inherent directionality of the radiating elements, full-space energy focusing is achieved, improving main lobe gain and anti-interference capabilities.

[0035] Furthermore, the coherent array extension module 4 achieves a narrower coherent beam focusing effect through optimization of the spacing of the slot radiating elements and the slot loading position. The coherent array extension module 4 consists of multiple identical single-slot-loaded, clustered space-frequency low-correlation coded array antennas arranged at predetermined intervals, forming a linear or area array structure to achieve higher gain and stronger directivity coherent radiation. The specific array configuration supports system-level performance expansion and is suitable for long-range detection scenarios. By optimizing the spacing between adjacent antenna elements and the loading position of the slots in each element, the wavefront phase relationship after coherent superposition is adjusted, achieving a narrower main beamwidth and higher directivity gain. The key control parameters in coherent extension demonstrate that the system can achieve performance customization through structural optimization, enhancing its engineering practicality.

[0036] A further improvement lies in the antenna's operating frequency band of 32GHz–36GHz and a center frequency of 34GHz, making it suitable for high-resolution imaging and detection applications in the millimeter-wave band. The antenna's operating parameter range facilitates integration with specific application scenarios such as security checks and radar, enhancing the feasibility of technology implementation. In particular, the antenna's overall physical dimensions of 302mm × 144mm are miniaturized and lightweight, making it suitable for integration into mobile platforms or compact electronic systems. This application's advantages in volume control align with the integration requirements of modern microwave systems. The antenna can be applied in microwave correlation imaging systems, millimeter-wave security inspection equipment, UAV-borne detection platforms, or intelligent traffic monitoring radars to achieve rapid, low-noise, and high-resolution target detection and identification. The metasurface unit in the low-correlation coding module 2 can be replaced with artificial electromagnetic materials, frequency-selective surfaces (FSS), reconfigurable metasurfaces, or active tuning elements to achieve dynamically programmable space-frequency coding functionality.

[0037] The present application will be described in detail below with reference to specific embodiments and accompanying drawings.

[0038] like Figure 1 As shown, this application provides a slot-loaded focused space-frequency low-correlation coded array antenna, including: a uniform feeding module 1, a low-correlation coding module 2, a slot array radiation module 3, and a coherent array extension module 4.

[0039] Specifically, the uniform feeding module 1 provides an excitation electric field with uniformly distributed power in the frequency dimension for the low-correlation coding module 2, and ensures good impedance matching of the slot-loaded focused space-frequency low-correlation coded array antenna within its operating frequency band. The low-correlation coding module 2 is positioned between the uniform feeding module and the slot array radiation module 3. The low-correlation coding module 2 encodes the received electromagnetic signal in the frequency dimension to generate a large number of low-correlation electromagnetic radiation signals at discrete frequency points. The slot array radiation module 3 efficiently and with high gain radiates the excitation signal encoded by the low-correlation coding module 2 into space, forming a low-correlation detection mode, and can focus the angle of the radiated signal energy. The coherent array extension module 4 combines multiple single-slot-loaded focused space-frequency low-correlation coded array antennas into a coherent array to achieve higher-gain electromagnetic wave radiation.

[0040] In a preferred embodiment, the uniform feeding module includes a single-feed-port standing wave structure, a coupled slot array structure, and a cavity end loading structure. The single-feed-port standing wave structure uniformly transmits the fed electromagnetic wave signal to slot elements of different lengths in the coupled slot array structure, ensuring good impedance matching. The coupled slot array structure is distributed above the single-feed-port standing wave structure, uniformly transmitting the electromagnetic wave signal to the low-correlation coding module 2. The cavity end loading structure is used to adjust the reflection characteristics of the fed signal at the cavity end.

[0041] In a preferred embodiment, the low-correlation coding module 2 is a symmetrical 6-layer metasurface substrate. Each substrate is composed of metasurface units of different structures randomly arranged on a medium of different structures. Each side includes 2 transmissive metasurface substrates and 1 reflective metasurface substrate. The introduction of metasurfaces in the low-correlation coding module 2 disrupts the inherent resonant mode of the cavity, so that different low-correlation coding modes can be generated when excitation sources of different frequencies are used, and low-correlation coding that varies with frequency is generated for the signal.

[0042] In a preferred embodiment, the slot array radiation module 3 includes an array structure with rectangular radiation slots of different lengths and a double-sided rectangular slot structure; the slot array structure is used to radiate the randomly modulated electromagnetic signal inside the waveguide cavity into free space, forming a large number of low-correlation detection modes at different discrete frequency points; the double-sided rectangular slot structure is used to constrain the energy of the radiated random electromagnetic signal at an angle.

[0043] In a preferred embodiment, the coupling slot array structure of the uniform power supply module and the rectangular radiation slot structure of the slot array radiation module 3 are multiple long rectangular slot structures of different lengths, and the corners are semi-circular transition structures.

[0044] As a preferred embodiment, the coupling slot array structure of the uniform feeding module includes slots of various lengths. Each type of slot has good feeding capability in a specific frequency band. By arranging slots of different lengths on the feeding aperture, uniform feeding in the operating frequency band can be achieved.

[0045] As a preferred embodiment, the rectangular radiation slot structure of the slot array radiation module 3 includes slots of various lengths. Each length of slot has good radiation capability in a specific frequency band. Arranging slots of different lengths on the radiation aperture achieves energy radiation uniformity in the frequency coding dimension.

[0046] In a preferred embodiment, the double-sided rectangular slot structure of the slot array radiation module 3 generates an induced current when radiating energy through the slot. By changing the position of the slot, it can be fitted into a spatial distribution array arrangement to achieve the radiation angle constraint of the encoded electromagnetic signal.

[0047] As a preferred embodiment, the radiation pattern of the radiation slots of the slot array radiation module 3 itself can further enhance the radiation angle constraint capability of the encoded electromagnetic signal.

[0048] In a preferred embodiment, the coherent array extension module consists of 32 identical single-slot loaded clustered space-frequency low-correlation coded array antennas, which achieve higher gain electromagnetic wave radiation through array synthesis.

[0049] In this embodiment, the slot-loaded frequency division random modulation antenna has dimensions of 302mm × 144mm and a transmit signal bandwidth of 32~36GHz. Figure 2 As shown, the overall S-factor of the antenna is below -10dB within the operating frequency band, indicating that the surface antenna has good feeding performance and high energy utilization. Figure 3 and Figure 4 The images show the radiation patterns of the antenna in the E-plane (elevation) and H-plane (azimuth) at the main frequency of 34 GHz. It can be seen that the elevation plane radiation pattern achieves a 3 dB beamwidth constraint within ±30° through the loaded double-sided rectangular slot structure. The electromagnetic signal after passing through the low-correlation coding module 2 exhibits randomness, which manifests as multiple narrow beams with uniform energy in the azimuth plane radiation pattern. Figure 5 The average radiation pattern of the antenna in the H-plane (azimuth plane) within the operating frequency band shows that the 3dB beamwidth of the pattern is also around ±30°.

[0050] In existing technologies, microwave imaging systems generally rely on phased arrays or multi-channel phase shifters to achieve beam scanning and spatial resolution, resulting in complex hardware, high cost, and difficulty in miniaturization. To address these issues, this application proposes an integrated, phase-shift-free, wideband, low-correlation coded antenna architecture. This antenna comprises four functional modules: a uniform feed module 1 employing a single-feed standing wave structure, propagating the input electromagnetic wave longitudinally through a rectangular waveguide cavity, and featuring an array of coupling slots of varying lengths on its upper surface. Each slot length corresponds to a strong coupling response in a specific frequency band, thereby achieving uniform distribution of excitation energy across the entire operating frequency band (e.g., 32–36 GHz). The bottom of this module is enclosed by a metal short-circuit wall, creating a standing wave field environment, improving feed efficiency and impedance matching performance. The low-correlation coding module 2, located above the feed module, consists of six symmetrically arranged dielectric substrates. Each side includes two transmissive metasurface substrates and one reflective metasurface substrate. Each substrate is etched with metal patch units of different geometric shapes (such as "I," ring, and cross shapes) arranged using a random optimization algorithm. These units have different resonant frequencies and phase response characteristics. When electromagnetic waves pass through this module, their spatial distribution is randomly modulated, disrupting the periodic resonant modes of traditional waveguides. This results in highly uncorrelated far-field radiation patterns generated under different frequency excitations, achieving spatial frequency coding in the frequency dimension. The slot array radiation module 3, located at the top layer, contains a set of non-uniformly arranged rectangular radiation slots. Each slot has a different length, corresponding to the optimal radiation state at different frequencies, ensuring that the coded signal can be effectively radiated into free space across the entire frequency band. The corners at both ends of the slots are designed with semi-circular transition structures to reduce electric field concentration effects and improve the breakdown threshold and radiation efficiency. Furthermore, a double-sided rectangular slot structure is set on both sides of the radiating surface. This slot induces current during electromagnetic radiation, and its spatial distribution is equivalent to a one-dimensional array. This constrains the elevation (E-plane) radiation pattern, controlling the main lobe width within ±30°. The coherent array extension module 4 consists of 32 identical single antenna elements arranged in parallel at fixed intervals to form a linear array. The elements are synchronously excited via coaxial feed lines, utilizing the principle of coherent superposition to achieve overall gain enhancement and main beam narrowing. All modules are mechanically and electrically connected via screws or welding, resulting in a compact overall structure that is easy to manufacture and integrate.

[0051] During operation, the radio frequency signal is input from the bottom single-feed port to the uniformly fed module, forming a standing wave field within the waveguide cavity. Energy is extracted and transferred step-by-step to the upper low-correlation coding module through coupling slots of varying lengths. The multi-layered random metasurfaces in the coding module spatially non-uniformly modulate this energy, causing different frequency components to excite different scattering modes, generating numerous uncorrelated radiation patterns. These encoded signals are efficiently radiated into space via the top-layer non-uniform slot array, forming multiple independent narrow beams in the azimuth plane and achieving beam focusing in the elevation plane through a slotted line structure. When multiple such antenna elements form a coherent array, their radiation fields coherently superimpose in the far field, significantly enhancing the main lobe gain and directivity. The four-module integrated structure achieves wideband, low-correlation detection capability without phase shifters, significantly reducing system complexity and manufacturing costs. Through a frequency-driven spatial coding mechanism, a large number of independent observation modes can be generated under limited physical aperture, improving imaging resolution. The synergistic effect of double-sided slot lines and non-uniform gaps achieves full-plane angle constraints, enhancing energy utilization. The coherent extension structure supports flexible arraying, making it suitable for long-distance, high-gain applications.

[0052] In practical engineering applications, to achieve uniform excitation and stable matching across a wide frequency band, the feed structure requires meticulous design. This uniform feed module uses a rectangular metal waveguide as a single-feed standing wave structure, made of 6061 aluminum alloy with a thickness of 2.5 mm and internally filled with air. Its dimensions are compatible with the standard WR-28 waveguide interface (wide side approximately 7.1 mm). The feed port is located at the center of one end of the waveguide, while the other end is sealed by a short metal surface, forming a complete standing wave excitation environment. Multiple elongated rectangular coupling slots are formed on the upper surface of the waveguide, totaling 12 slot elements, divided into three groups. Each group contains four different lengths (6.8 mm, 7.2 mm, 7.6 mm, and 8.0 mm), corresponding to the strong coupling windows in the 32–33 GHz, 33–34 GHz, 34–35 GHz, and 35–36 GHz frequency bands, respectively. These slots are non-uniformly distributed along the waveguide length, densely arranged near the electric field peak region to maximize energy extraction efficiency. The slot corners are semi-circular transitions with R=0.5mm to prevent breakdown caused by local electric field concentration. The coupling slot array directly contacts the underlying dielectric substrate of the low-correlation coding module, achieving near-field coupling transmission. The loading structure at the end of the cavity is the metal short-circuit surface, and its distance from the last coupling slot is set to λg / 4 (approximately 2.8mm) through simulation optimization. This is used to adjust the phase of the residual reflected wave, making it cancel out with the forward wave, thereby widening the matching bandwidth. In practical applications, this waveguide structure can also be made of brass or stainless steel, and the number and length combination of coupling slots can be adjusted according to specific frequency band requirements. This application does not limit this. Through the synergistic effect of VSWR and multi-band coupling slots, this structure ensures that the energy output fluctuation of the input signal at each frequency in the 32–36GHz range is less than ±1.5dB, meeting the excitation uniformity requirements of subsequent coding modules. The end short-circuit design effectively suppresses impedance mismatch at the high-frequency end, ensuring that the S11 parameter is below -10dB throughout the entire operating frequency band, guaranteeing high energy utilization of the system. By combining multi-band coupling slots with standing wave structures, broadband uniform excitation under a single feed port is achieved, avoiding the size and loss problems caused by traditional multi-feed networks. The end reflection control mechanism improves the overall impedance matching performance, ensuring that the encoding process is not affected by excitation fluctuations, and improving the stability and repeatability of the radiation mode.

[0053] To achieve frequency-sensitive random electromagnetic control, the low-correlation coding module adopts a six-layer symmetrical stacked structure, with three layers on the top and three on the bottom. From front to back, each side consists of the following layers: The first layer is a transmissive metasurface substrate, made of Rogers RO4003C dielectric substrate with a thickness of 0.508mm (dielectric constant εr=3.55, loss tangent tanδ=0.0027). A metal pattern is etched on it, consisting of randomly arranged "H" and "I" shaped metal units with unit sizes varying between 1.8–2.4mm, mainly used to control the amplitude and phase of the transmitted wave; The second layer is also a transmissive metasurface, with the same dielectric material, but the metal pattern uses "L" shaped and square ring structures to further increase the freedom of phase control; The third layer is a reflective metasurface substrate, made of FR-4 epoxy fiberglass board with a thickness of 1.6mm (εr=4.4, tanδ=0.02). Its back is copper-grounded, and the front is printed with "+" and "X" shaped metal patches to reflect the electromagnetic energy that is not transmitted and to apply additional phase perturbation. The structure is completely symmetrical on both sides, with an air gap of approximately 1.0 mm in the middle, and a total height of approximately 5.2 mm. The positions of all metasurface units are randomly optimized using a genetic algorithm to ensure no periodic repetition, and the spacing between adjacent units is greater than half a wavelength to prevent strong coupling effects. The metal layer is copper foil with a thickness of 35 μm, fabricated using PCB photolithography. In practical applications, the dielectric material can also be high-frequency board material such as Taconic TLY-5 or Arlon AD255, and the metal pattern can be replaced with silver paste printing or laser direct writing structure; this application does not limit this. During operation, electromagnetic waves from below pass through the upper three metasurface structures sequentially. Each penetration is subject to spatially non-uniform amplitude attenuation and phase deflection. Due to the significant change in the resonant characteristics of each unit with frequency, the same physical location exhibits drastically different electromagnetic responses at different frequencies. This dynamic modulation effect breaks the deterministic propagation law of the original waveguide mode, forcing the system into a chaotic radiation state, thereby making the far-field patterns corresponding to each discrete frequency point highly uncorrelated (cross-correlation coefficient less than 0.1), achieving the purpose of low correlation coding in the spatial frequency domain. This multi-layered random metasurface structure effectively eliminates the dependence of traditional antennas on fixed modes, giving the antenna the ability to generate a massive number of independent detection modes in the frequency dimension; the symmetrical design balances the forward and backward radiation, improving energy utilization efficiency; the synergistic effect of the transmission and reflection structures enhances the modulation depth and coding freedom.

[0054] The coherent array extension module consists of 32 identical single-slot loaded antenna elements arranged horizontally in parallel, forming a linear array structure with a total width of approximately 302 mm. The center-to-center spacing between adjacent elements is 9.4 mm, slightly smaller than the free-space wavelength corresponding to the center frequency of 34 GHz (approximately 8.8 mm), to avoid grating lobes. The feed port of each element is excited by the same signal source through a 1-to-32 power divider network, ensuring phase consistency. By jointly simulating and optimizing the element spacing and the longitudinal position of the coupling slots within each antenna, the phase distribution of the radiation field of each element is adjusted to achieve maximum coherent superposition of the far-field main beam in the θ=0° direction. Test results show that the main lobe width of this coherent array is compressed from approximately 60° of a single antenna to approximately 8°, with a gain improvement of over 15 dB. In practical applications, the array can be expanded into a two-dimensional planar array, or a non-uniform spacing design can be used to suppress sidelobes; this embodiment does not limit this. This coherent extension structure combines multiple low-gain wide-beam elements into a high-gain narrow beam through the interference effect of the spatial array, significantly improving detection range and directional resolution. This represents an upgrade from unit-coded detection to large-scale coordinated radiation, significantly enhancing the system's practicality and detection performance.

[0055] The slot-loaded spot-band low-correlation coded array antenna of this application utilizes four different working modules to generate a large number of low-correlation detection modes over a wide frequency band. It can be used to detect multiple targets simultaneously, effectively suppressing random noise and interference, ensuring the overall miniaturization and lightweight of the detection system, and significantly improving the performance of microwave correlation detection systems.

[0056] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A slot-loaded focus-frequency low-correlation coded array antenna, characterized in that, include: The coherent array extension module (4) is used to arrange multiple identical single-slot loaded antennas at a predetermined interval to form a coherent array; The uniform feeding module (1) is used to uniformly distribute electromagnetic signals to subsequent modules in the working frequency band through a single-feed standing wave structure and a slot array composed of coupling slots of various different lengths, so as to ensure power balance and impedance matching in the frequency dimension. The low correlation coding module (2) is disposed on the uniform power supply module (1) and includes a symmetrically arranged multilayer metasurface substrate. Each substrate is provided with metasurface units of different geometric structures arranged randomly. By spatially modulating the electromagnetic field, the inherent resonance characteristics of the cavity are destroyed, so that excitations of different discrete frequencies generate uncorrelated coding responses, thereby realizing low correlation space frequency coding in the frequency dimension. The slot array radiation module (3), located above the low correlation coding module (2), is composed of non-uniformly distributed rectangular radiation slots of various lengths and double-sided rectangular slots. It is used to efficiently radiate the encoded electromagnetic signal into free space, form a large number of low correlation detection beams in the azimuth plane, and constrain the radiated energy of the elevation plane by angle through the slot structure. The coherent array extension module (4) is used to arrange multiple identical single-slot loaded antennas at a predetermined interval to form a coherent array.

2. The slot-loaded focus-space frequency low-correlation coded array antenna according to claim 1, characterized in that, The uniform feeding module (1) includes a single-feed-port standing wave structure, a coupled slot array structure, and a cavity end loading structure; the single-feed-port standing wave structure uniformly transmits the fed electromagnetic wave signal to slot units of different lengths in the coupled slot array structure; the coupled slot array structure is distributed on the single-feed-port standing wave structure and uniformly transmits the electromagnetic wave signal to the low-correlation coding module (2); the cavity end loading structure is used to adjust the reflection characteristics of the fed signal at the cavity end; The cavity end loading structure is a short metal surface, which is set at the tail of the uniform feed module (1) to form a standing wave field distribution and adjust the input impedance characteristics of the entire antenna structure in the working frequency band.

3. The slot-loaded focus-space frequency low-correlation coded array antenna according to claim 1, characterized in that, The low correlation coding module (2) includes a symmetrically arranged multilayer metasurface substrate, each side including at least one transmissive metasurface substrate and one reflective metasurface substrate, and each substrate is composed of metasurface units with different geometric structures randomly arranged on a dielectric substrate. The metasurface units are arranged non-periodically using a stochastic optimization algorithm, which results in low cross-correlation of electromagnetic response modes generated under different frequency excitations, thereby generating a large number of independent space detection modes.

4. The slot-loaded focus-space frequency low-correlation coded array antenna according to claim 1, characterized in that, The slot array radiation module (3) includes a variety of rectangular radiation slots of different lengths, which are non-uniformly arranged along the long side of the antenna. Each slot of length corresponds to the radiation characteristics of a specific frequency band.

5. The slot-loaded focus-space-frequency low-correlation coded array antenna according to claim 4, characterized in that, The rectangular radial slit has a long strip structure with semi-circular transitions at both ends.

6. The slot-loaded focus-space-frequency low-correlation coded array antenna according to claim 1, characterized in that, The slot array radiation module (3) also includes a double-sided rectangular slot structure disposed on both sides of the radiation surface. The double-sided rectangular slot structure generates induced current during the radiation process, and its spatial distribution is equivalent to a one-dimensional array.

7. The slot-loaded spot-loaded space-frequency low-correlation coded array antenna according to claim 1, characterized in that, The radiation pattern of the radiation slot itself has narrow beam characteristics, which, together with the slot line structure, achieves dual-plane beam focusing.

8. The slot-loaded focus-space frequency low-correlation coded array antenna according to claim 1, characterized in that, The coherent array extension module (4) is composed of multiple identical single-slot loaded clustered space-frequency low-correlation coded array antennas arranged at predetermined intervals to form a linear array or area array structure.

9. The slot-loaded focus-frequency low-correlation coded array antenna according to claim 1, characterized in that, The coherent array extension module (4) adjusts the wavefront phase relationship after coherent superposition by optimizing the spacing between adjacent antenna elements and the loading position of the gaps in each element.

10. A slot-loaded, clustered space-frequency low-correlation coded array antenna according to claim 1, characterized in that, The antenna operates in the frequency band of 32GHz to 36GHz, with a center frequency of 34GHz.

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