High-precision hybrid polarization microwave imaging antenna system

Abstract

The invention, which relates to the antenna field, discloses a high-precision hybrid polarization microwave imaging antenna system comprising an H / V polarization independent radio frequency isolation network and a dielectric laminated orthogonal feed architecture. The H / V polarization independent radio frequency isolation network realizes isolation between H polarization and V polarization in the phased-array antenna and amplitude-phase consistency; the dielectric laminated orthogonal feed architecture is used for regulating and controlling near-field coupling energy distribution, so that H / V polarization field distribution is orthogonal to each other and shares the same phase center. According to the invention, an H / V polarization independent radio frequency isolation link and dielectric lamination orthogonal feed architecture is provided, the H / V polarization high isolation degree of a radio frequency link is guaranteed at a hardware level, and crosstalk among different polarization signals is effectively reduced; and meanwhile, through the flexible control time sequence design of hybrid polarization simultaneous emission, the high-efficiency integrated low-error delay T / R assembly and the common-caliber same-phase center antenna design, the amplitude and phase height consistency of H / V polarization signals is realized, and the imaging problem caused by amplitude and phase difference is avoided.

Description

Technical Field

[0001] The present invention relates to the field of antennas, and in particular, to a high-precision hybrid polarization microwave imaging antenna system. Background Art

[0002] The hybrid polarization microwave imaging antenna system can obtain the complete polarization scattering matrix of the target through the flexible switching and collaborative work of multiple polarization modes such as horizontal (H) and vertical (V). Its advantage lies in providing multi-dimensional polarization information, finely describing the scattering characteristics of the target, significantly improving the accuracy of target classification and recognition, and being applicable to complex scene detection and parameter inversion. However, the system needs to meet the core indicators that the polarization isolation is better than 25 dB and the channel amplitude-phase consistency is better than 0.5 dB / 10°, otherwise it will cause target polarization decomposition deviation and polarization classification errors.

[0003] The existing implementation methods of hybrid polarization microwave imaging antenna systems mainly have the following limitations: ① The separated feeding structure is complex: The traditional multi-channel design adopts a separated feed design to achieve high isolation, but the completely separated feeding network structure is complex and bulky. When the number of antenna channels is large or the antenna spatial layout is relatively complex, the radio frequency transceiver links are intertwined, and it is difficult to achieve the optimal design of isolation. The instability of the phase center will also cause the deviation of the main pattern; ② Polarization crosstalk of antenna elements: The antenna elements adopt a dual-polarization feeding design, and there is a lack of corresponding isolation measures between the feeding ports of the two polarizations, resulting in a certain degree of polarization crosstalk; ③ Channel inconsistency: The inconsistency between the components of each channel will lead to different transfer coefficients for each. The traditional timing control method ignores the amplitude and phase coefficient inconsistencies of the multi-channel echo data of the hybrid polarization antenna system, increasing the parameter estimation error. In addition, limited by the strict space size constraints and complex working environment of the carrier platform, it is difficult to efficiently implement the isolation optimization and channel amplitude-phase calibration strategies of the existing separated feeding structure, further exacerbating the difficulty of achieving the high isolation and amplitude-phase consistency indicators. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a high-precision hybrid polarization microwave imaging antenna system, and the specific technical solution is as follows:

[0005] A high-precision hybrid polarization microwave imaging antenna system, characterized in that it includes: an H / V polarization independent radio frequency isolation network and a dielectric laminate orthogonal feeding architecture;

[0006] Among them, the H / V polarization independent radio frequency isolation network realizes the isolation and amplitude-phase consistency between the H polarization link and the V polarization link in the phased array antenna;

[0007] The H / V polarization-independent RF isolation link includes: an H-polarization feeding network, a V-polarization feeding network, an H-polarization feeding port, a V-polarization feeding port, and a central electronic device; each antenna element of the phased array antenna integrates an H-polarization feeding port and a V-polarization feeding port, and H or V polarization signals are fed into the antenna element from the H-polarization feeding port and the V-polarization feeding port. The H-polarization feeding port and the V-polarization feeding port are respectively used to excite the antenna element to generate H-polarization and V-polarization electromagnetic waves, and are connected to the central electronic device through independent H-polarization and V-polarization feeding networks;

[0008] The dielectric stack orthogonal feeding architecture is used to regulate the near-field coupling energy distribution of the antenna element, make the H / V polarization field distributions orthogonal to each other, and share the same phase center;

[0009] The dielectric stack orthogonal feeding architecture includes an H-polarization feeding strip line, a V-polarization feeding strip line, an H-shaped slot, and a double-layer radiation patch. Corresponding polarization signals are respectively input into the H-polarization feeding strip line and the V-polarization feeding strip line through the H-polarization feeding port and the V-polarization feeding port. The H-polarization feeding strip line and the V-polarization feeding strip line are orthogonally arranged with the H-shaped slot to generate electromagnetic coupling, and the energy is excited to the double-layer radiation patch to realize the radiation of H-polarization or V-polarization electromagnetic waves.

[0010] The present invention has the following beneficial effects:

[0011] The present invention proposes an H / V polarization-independent RF isolation link and a dielectric stack orthogonal feeding architecture, which ensure high H / V polarization isolation of the entire RF link at the hardware level and effectively reduce the crosstalk between different polarization signals; at the same time, through the flexible control timing design of simultaneous transmission of mixed polarizations, a highly efficient integrated low-error delay T / R component, and a co-aperture and co-phase center antenna design, the H / V polarization signals are made highly consistent in amplitude and phase characteristics, avoiding imaging problems caused by amplitude-phase differences. This method optimizes the entire link from signal transmission to reception, successfully solves the polarization ambiguity problem, significantly improves the imaging performance of the spaceborne SAR system, enables the system to achieve a wider imaging swath while maintaining good imaging quality, and effectively improves the comprehensive efficiency of the spaceborne SAR system. Description of the Drawings

[0012] Figure 1 It is a schematic diagram of the H / V polarization-independent RF isolation link;

[0013] Figure 2 It is a schematic diagram of the measured result of the isolation degree of the polarization-independent RF isolation link;

[0014] Figure 3 It is a distribution diagram of the H / V polarization field of the double-layer radiation patch;

[0015] Figure 4Schematic diagram of H / V polarization independent resonant cavity and low cross-polarization performance;

[0016] Figure 5 Working timing diagram of H / V polarization alternating / simultaneous transmission;

[0017] Figure 6 Design link diagram of high-efficiency integrated low-error delay T / R module;

[0018] Figure 7 Measured transmit power schematic diagram of high-efficiency integrated low-error delay T / R module;

[0019] Figure 8 Schematic diagram of the co-phase center design and simulation results of the antenna element;

[0020] Figure 9 Hybrid polarization classification framework diagram;

[0021] Figure 10 Comparison diagram of the observation results of a certain area in the alternating transmission full polarization mode and the simultaneous transmission hybrid polarization mode of the on-orbit satellite antenna system adopting the system of the present invention. Detailed implementation mode

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] According to an embodiment of the present invention, a high-precision hybrid polarization microwave imaging antenna system includes: an H / V polarization independent radio frequency isolation network and a dielectric stack orthogonal feeding architecture, which realizes high isolation of the H polarization / V polarization link in a hybrid polarization spaceborne large phased array antenna, and takes into account the entire radio frequency link, further regulating the near-field coupling energy distribution of the antenna to make the H / V polarization field distributions orthogonal to each other.

[0024] The H / V polarization independent radio frequency isolation link includes: a feeding network, a feeding port, and a central electronic device;

[0025] Each antenna element of the phased array antenna on the radiation array surface is integrated with an H polarization feeding port and a V polarization feeding port. The H / V polarization signals are fed into the antenna element from the H polarization feeding port and the V polarization feeding port. The H polarization feeding port and the V polarization feeding port are respectively used to excite the antenna to generate electromagnetic waves of H and V polarizations, and are connected to the central electronic device through independent H polarization and V polarization feeding networks. Among them, the H polarization and V polarization feeding networks are composed of delay T / R modules and radio frequency power distribution networks. Schematic diagrams of the complete links of H polarization and V polarization are asFigure 1 As shown. For each antenna element of the high-isolation hybrid polarization radiation array, the H-polarization and V-polarization feed ports are respectively connected to the H-polarization feed network and the V-polarization feed network. The delay T / R module realizes the delay control and transmit / receive switching of signals, and the RF power distribution network completes the signal distribution and synthesis. The design of the H-polarization and V-polarization feed networks follows the principle of complete isolation. Except for the shared power supply system, calibration, and control network, different feed networks are independently configured to ensure the high reliability of signal transmission. The central electronic device uniformly regulates the transmit, receive, calibration, and control functions of H-polarization and V-polarization. Each delay T / R module has 2 transceiver channels, and the 2 channels of a single delay T / R module only receive signals of the same polarization (H-polarization or V-polarization). Electromagnetic shielding between H / V polarizations is achieved through a metal cavity, and physical isolation design is used to suppress cross-talk. At the same time, the H / V polarization RF cables are routed in an isolated layout to minimize the coupling between signal links and ensure the high isolation index requirements of the system. The proposed RF isolation link achieves an isolation better than 40 dB, as Figure 2 shown.

[0026] The dielectric stack orthogonal feeding architecture is specifically as follows:

[0027] The H-polarization feeding strip line, V-polarization feeding strip line, and H-shaped slot are located inside the antenna element. The H / V polarization feed ports of the antenna element input the corresponding polarization signals to the independent H-polarization feeding strip line and V-polarization feeding strip line respectively. The H-polarization feeding strip line, V-polarization feeding strip line, and H-shaped slot are orthogonally arranged to generate electromagnetic coupling, and the energy is excited to the double-layer radiation patch to realize the radiation of H-polarization or V-polarization electromagnetic waves. The H-shaped slot provides broadband coupling ability, and the double-layer radiation patch forms a parasitic element structure, which can flexibly optimize the impedance matching and radiation characteristics of the antenna. The H / V polarization feeding strip line and the H-shaped slot are orthogonally arranged and surrounded by metal shielding posts to form an independent feeding resonant cavity, realizing polarization isolation under high-density integration. An additional layer of metal shielding posts is added to the periphery of the V-polarization feeding resonant cavity and H-polarization feeding resonant cavity antenna elements to effectively suppress the leakage of electric field energy and improve the radiation efficiency. By optimizing the feeding structure and cavity parameters, the near-field coupling energy distribution of the antenna is accurately regulated, so that the H / V polarization field distributions are orthogonal to each other, as Figure 3 shown. Compared with the traditional probe feeding method, this symmetric coupling slot feeding design significantly improves the polarization purity. After actual measurement, the cross-polarization in the normal direction of the antenna is lower than -40 dB, as Figure 4 shown, meeting the application requirements of the high-isolation and low-cross-polarization hybrid polarization SAR system.

[0028] To achieve high amplitude and phase consistency of H polarization / V polarization in a hybrid polarization spaceborne large phased array antenna, taking into account the entire RF link, a design of flexible control timing for simultaneous transmission of hybrid polarization, an integrated low-error delay T / R component with high efficiency, and a common aperture and co-phase center antenna is proposed;

[0029] The in-cabin wave control sub-unit generates the working timing according to the SAR working mode and transmits it to the wave control unit. The wave control unit distributes the working timing signal to each delay T / R component to achieve switching control of the receiving, transmitting, and load three working states. At the same time, the delay, phase shift, and attenuation parameters required for antenna pattern scanning and shaping are configured through the beam control code. The system sets three control timing signals, namely TR1, TR 2_H , TR 2_V . Among them, TR1 is the common control pulse for the H / V receiving channels, and TR 2_H , TR 2_V are the independent control pulses for the H / V transmitting channels respectively.

[0030] In the receiving mode, when TR1 is at a high level, the delay T / R component enters the receiving state; if single-polarization reception is required, by loading the load state control code of the other polarization channel, the non-working polarization channel is in the load state. In the transmitting mode, when TR1 is at a low level, if one of TR 2_H and TR 2_V is at a low level and the other is at a high level, single-polarization transmission is achieved; if both are at a low level, the dual-polarization simultaneous transmission state is triggered. This scheme realizes flexible switching of the working mode of the delay T / R component through the coordinated control of the timing signal and the control code, meeting the multi-polarization working requirements of the SAR system. The working timing diagram of H / V alternating / simultaneous transmission is as shown in Figure 5 .

[0031] The present invention integrates the traditional T / R component and the delay amplification component into one design architecture. Through the dual-channel integration technology, each delay T / R component has 2 transceiver channels built-in, and the 2 channels of a single component only receive signals of the same polarization (H polarization or V polarization). Combining the LTCC multi-layer substrate process, ceramics and metal conductor pastes are stacked alternately and co-fired at a low temperature to form an integrated multi-layer ceramic substrate, realizing the integration of three-dimensional solid circuits and achieving lightweight under the premise of ensuring performance indicators. The design link of the delay T / R component is as shown in Figure 6As shown in the figure, a 4 / 2 / 1 multiple wavelength selectable delay line is connected to a bidirectional amplifier with power modulation, then connected to a digital phase shifter, and then connected to the receive and transmit paths or a load through a radio frequency switch. When the antenna is in the transmit state, the radio frequency signal transmission path includes an adjustable phase shifter, a driver amplifier, and a power amplifier; when the antenna is in the receive state, the radio frequency signal transmission path includes a limiter amplifier, a temperature compensated attenuator, a digital attenuator, an adjustable attenuator, and an adjustable phase shifter. Among them, the driver amplifier, power amplifier, and limiter amplifier are equipped with power modulation, and a thermistor is connected in parallel to the power amplifier to compensate for the influence of temperature on signal attenuation. The receive and transmit paths are connected to the antenna through a circulator, and the wave control circuit is connected to each module to coordinate the operation of each component. In addition, a calibration port is provided to calibrate the amplitude and phase characteristics of the component channels. This component realizes the integration of the delay line and the T / R component, meeting the requirements of system miniaturization and low error.

[0032] This component adopts a GaN solid-state emission scheme, supports high-power emission of 45W and a duty cycle of up to 20%, and the energy conversion efficiency reaches 48%, significantly improving the system power utilization efficiency. Aiming at the strict requirements of hybrid polarization imaging for the amplitude consistency of H / V polarization emission, through strict control and screening of the consistency between channels, the emission power error of each channel is controlled within 0.5dB, as Figure 7 shown, ensuring that the amplitude consistency of the dual-polarization signal meets the system index.

[0033] Aiming at the strict requirements of hybrid polarization imaging for the phase center consistency of H / V polarization, based on the dielectric stack orthogonal feeding architecture, a symmetric antenna H / V polarization feeding layout is constructed. Two groups of H-polarization and V-polarization feeding resonant cavities formed by feeding strip lines, "H"-shaped slots, and metal shielding posts are symmetric to each other and share a double-layer radiation patch, laying the foundation for phase center symmetry from the physical architecture. The metal shielding posts physically isolate the feeding strip line and the "H"-shaped slot, forming independent feeding cavities to suppress the cross-interference of different polarization signals. In addition to using metal shielding posts to achieve physical isolation of the feeding ports, through the symmetric layout design of the "H"-shaped slots, the spatial symmetry of the radiation patch aperture field distribution and the phase center is ensured. The symmetric "H"-shaped slot structure enables the electromagnetic energy excited by H / V polarization to form a mirror-symmetric field distribution on the radiation patch, effectively suppressing the phase center offset and ensuring the phase stability of the dual-polarization signal during radiation. The H / V polarization aperture field distribution and phase pattern are as Figure 8 shown.

[0034] The present invention applies the physical constraint model of high isolation and high amplitude-phase consistency of hybrid polarization for spaceborne large phased array antennas to the on-orbit satellite antenna system, obtains the ground object scattering characteristics, and proposes a hybrid polarization classification framework, as Figure 9As shown in the figure, the hybrid polarization classification framework consists of three parts: "input data", "spatial information extraction", and "classification". After the input data is processed by spatial information extraction, it is output to the classification module, and the model training and class label acquisition are completed in sequence to form a complete hybrid polarization classification framework. The specific steps and relationships are as follows: The input data includes ground truth data, full polarization data, and hybrid polarization data, which are input as the basic data for subsequent processing; Spatial information extraction first calculates the similarity parameter, then randomly samples to calculate the median of the distance metric, and then truncates the similarity parameter to generate polarization data containing neighborhood spatial information; In the classification part, the model parameters are first initialized according to the observed data, and then parameter estimation is performed through iterative optimization. In the E step (expectation step), the algorithm calculates the expected value of the latent variable based on the current model parameters and observed data; In the M step (maximization step), the estimated latent variable and observed data are used to re-optimize the model parameters. This process is iteratively executed until convergence, and finally stable parameter estimation is obtained.

[0035] To simplify the training process, the present invention pre-sets a relatively large number of subclasses in the hybrid model training and merges the subclasses with small inter-class distances after the training is completed, so as to improve the calculation efficiency while ensuring the flexibility of the model.

[0036] Embodiment 1

[0037] The embodiment is an on-orbit satellite antenna system designed based on a hybrid polarization high isolation and high amplitude-phase consistency physical constraint model. The radar isolation is better than 36 dB, and the amplitude-phase consistency of the entire transceiver full link and full bandwidth is controlled within 0.13 dB / 1.6°, realizing the on-orbit application of multi-channel hybrid polarization imaging.

[0038] Embodiment 2

[0039] Adopting the above-mentioned hybrid polarization high isolation and high amplitude-phase consistency physical constraint model can improve the performance of the spaceborne SAR system. Figure 10 For the comparison of the observation results of an area when the on-orbit satellite antenna system alternately transmits the full polarization mode (left) and simultaneously transmits the hybrid polarization mode (right), it can be seen that the ambiguity of the hybrid polarization mode is reduced. In addition, in the full polarization working mode, the imaging swath of this system is 30 km, the resolution is 6 m×6 m, and the incident angle range is 13° to 21°; In the hybrid polarization working mode, the imaging swath is 50 km, the resolution is 3 m×3 m, and the incident angle range is 9° to 60°. A hybrid polarization classification framework based on iterative optimization of the EM algorithm is proposed. The E step calculates the expected value of the latent variable, and the M step optimizes the model parameters. A relatively large number of subclasses are preset in advance, and the subclasses with small inter-class distances are merged after training to balance the flexibility of the model and the calculation efficiency. The obtained hybrid polarization classification accuracy is 96.81%. It shows that the present invention has significant advantages in reducing the polarization ambiguity of the spaceborne SAR system, increasing the swath, and improving the classification accuracy.

Claims

1. A high-precision hybrid polarization microwave imaging antenna system, characterized in that, Including: H / V polarization-independent RF isolation network and dielectric stacked orthogonal feeding architecture; Among them, the H / V polarization-independent RF isolation network realizes isolation and amplitude consistency between the H-polarization link and the V-polarization link in the phased array antenna; The H / V polarization-independent RF isolation link includes: an H-polarization feeding network and a V-polarization feeding network, an H-polarization feeding port and a V-polarization feeding port, and a central electronic device; among them, each antenna unit of the phased array antenna integrates an H-polarization feeding port and a V-polarization feeding port, and the H or V polarization signal is fed into the antenna unit from the H-polarization feeding port and the V-polarization feeding port. The H-polarization feeding port and the V-polarization feeding port are respectively used to excite the antenna unit to generate H-polarization and V-polarization electromagnetic waves, and are connected to the central electronic device through independent H-polarization feeding network and V-polarization feeding network; The dielectric stacked orthogonal feeding architecture is used to regulate the near-field coupling energy distribution of the antenna unit, make the H / V polarization field distributions orthogonal to each other, and share the same phase center; The dielectric stacked orthogonal feeding architecture includes an H-polarization feeding strip line, a V-polarization feeding strip line, an H-shaped slot, and a double-layer radiation patch. The corresponding polarization signals are respectively input into the H-polarization feeding strip line and the V-polarization feeding strip line through the H-polarization feeding port and the V-polarization feeding port. The H-polarization feeding strip line and the V-polarization feeding strip line are orthogonally arranged with the H-shaped slot to generate electromagnetic coupling, and the energy is excited to the double-layer radiation patch to realize the radiation of H-polarization or V-polarization electromagnetic waves.

2. A high-precision hybrid polarization microwave imaging antenna system according to claim 1, characterized in that, Among them, The H-polarization and V-polarization feeding networks are composed of delay T / R components and RF power distribution networks; the H-polarization and V-polarization feeding ports are respectively connected to the H-polarization feeding network and the V-polarization feeding network. The delay T / R components realize the delay control and transmit / receive switching of signals, and the RF power distribution network completes the distribution and synthesis of signals.

3. A high-precision hybrid polarization microwave imaging antenna system according to claim 2, wherein Each delay T / R component has 2 transceiver channels built-in, and the 2 channels of a single delay T / R component only receive the same polarization signal, and the electromagnetic shielding between the H and V polarization links is realized through a metal cavity.

4. A high-precision hybrid polarization microwave imaging antenna system according to claim 1, characterized in that After the H-polarization and V-polarization feeding strip lines are orthogonally arranged with the H-shaped slot, independent V-polarization feeding resonant cavities and H-polarization feeding resonant cavities are formed by surrounding with metal shielding columns.

5. A high-precision hybrid polarization microwave imaging antenna system according to claim 4, wherein A metal shielding column is additionally arranged outside the V-polarization feeding resonant cavity, the H-polarization feeding resonant cavity and the antenna unit.

6. The high-precision hybrid polarization microwave imaging antenna system according to claim 3, wherein The delay T / R component adopts an integrated design of a T / R component and a delay amplification component. Through the integration of two channels, combined with the LTCC multi-layer substrate process, ceramics and metal conductor pastes are alternately stacked and co-fired at low temperature to form an integrated multi-layer ceramic substrate.

7. A high-precision hybrid polarization microwave imaging antenna system according to claim 3, characterized in that, The working timing signal is distributed to the delay T / R component to achieve the switching control of the three working states of reception, transmission, and load, and TR1 and TR are set. 2_H and TR 2_V Three working timing signals, where TR1 is the common control pulse for the H / V reception channels, and TR 2_H and TR 2_V are the independent control pulses for the H / V transmission channels respectively; in the reception mode, when TR1 is at a high level, the delay T / R component enters the reception state; in the transmission mode, when TR1 is at a low level, if TR 2_H and TR 2_V one of them is at a low level and the other is at a high level, single-polarization transmission is achieved; if both are at a low level, the dual-polarization simultaneous transmission state is triggered.

8. The high-precision hybrid polarization microwave imaging antenna system according to claim 3, characterized in that, The design link of the delay T / R component is specifically as follows: A 4 / 2 / 1 - wavelength - selectable device delay line is connected to a two - way amplifier with power modulation, then connected to a digital phase shifter, and then two paths of receive and transmit are connected. The two paths of receive and transmit are specifically as follows: The RF signal transmission path in the antenna transmission state includes an adjustable phase shifter, a driver amplifier, and a power amplifier; The RF signal transmission path in the antenna reception state includes a limiter amplifier, a temperature - compensated attenuator, a digital attenuator, an adjustable attenuator, and an adjustable phase shifter.

9. A high-precision hybrid polarization microwave imaging antenna system according to claim 8, characterized in that, The driver amplifier, power amplifier, and limiter amplifier are equipped with power modulation. A thermistor is connected in parallel to the power amplifier to compensate for the influence of temperature on signal attenuation. The two paths of receive and transmit are connected to the antenna through a circulator.

10. A high-precision spaceborne multi-channel hybrid polarization imaging system according to claim 5, characterized in that Two groups of H - polarization and V - polarization feed resonant cavities formed by surrounding the feed strip line, H - shaped slot, and metal shielding posts are symmetrical to each other and share a double - layer radiation patch.

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