A polarized reconfigurable microstrip patch antenna system based on ferrite substrate

Abstract

The application discloses a kind of polarized reconfigurable microstrip patch antenna systems based on ferrite substrate, system includes antenna body, drive control unit;The antenna body includes ferrite substrate, microstrip patch unit etched on ferrite substrate and four groups of electromagnetic coils arranged around the edge of ferrite substrate;The drive control unit is used to generate a synthetic magnetic field in the ferrite substrate by controlling the current direction and size of the four groups of coils, thereby changing the equivalent impedance and surface current distribution of the microstrip patch, and further changing the polarization mode of the antenna.The system has the advantages of flexible polarization mode, low power consumption, high integration, strong anti-interference ability, etc.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication antenna technology, and particularly relates to a polarization reconfigurable microstrip patch antenna system based on a ferrite substrate. Background Technology

[0002] Microstrip patch antennas are widely used due to their compact structure and ease of integration. However, the polarization direction (such as linear or circular polarization) of traditional microstrip antennas is usually fixed, making it difficult to adapt to signal transmission requirements in complex electromagnetic environments. For example, when multipath fading or changes in target polarization characteristics occur in the communication link, the gain and anti-interference capability of fixed-polarization antennas will significantly decrease. Existing polarization reconfigurable technologies and their shortcomings are mainly as follows:

[0003] 1. Adding electronic switching devices, such as PIN diodes and varactor diodes, to change the antenna structure (such as slots and branches) through switching states, but there are problems such as high power consumption (continuous power supply), narrow bandwidth (<5%), and low reliability.

[0004] 2. Mechanical adjustment structures: such as rotating antenna elements, have drawbacks such as slow response speed (>10ms), large size, and easy wear;

[0005] 3. Novel Material Control: Ferrite materials, due to their magneto-rotational magnetic properties (tunable permeability tensor), can alter the electromagnetic response of antennas through external magnetic fields. However, their application in microstrip antennas faces the following challenges: uneven magnetic field distribution leads to insufficient polarization control precision; traditional ferrite substrates and microstrip patches have low impedance matching efficiency; and there is a lack of quantitative analysis on the coupling relationship between permeability tensor and polarization modes.

[0006] Therefore, there is an urgent need for a design method for low-power, high-precision polarization reconfigurable microstrip patch antennas based on ferrite substrates. Summary of the Invention

[0007] The purpose of this invention is to provide a polarization-reconfigurable microstrip patch antenna system based on a ferrite substrate, which aims to solve the problems of slow polarization switching speed, high power consumption and complex structure in the prior art.

[0008] This invention is implemented as follows: a polarization-reconfigurable microstrip patch antenna system based on a ferrite substrate, the system comprising an antenna body and a drive control unit; the antenna body comprising a ferrite substrate, microstrip patch units etched on the ferrite substrate, and four sets of electromagnetic coils arranged around the edge of the ferrite substrate; the drive control unit is used to generate a synthetic magnetic field in the ferrite substrate by controlling the current direction and magnitude of the four sets of coils, thereby changing the equivalent impedance and surface current distribution of the microstrip patch, and thus changing the polarization mode of the antenna.

[0009] Preferably, the permeability tensor of the ferrite substrate is:

[0010]

[0011] Analytical expression under lossless approximation:

[0012]

[0013] Where, ω M =γM s ω0 = γμ0H0 is the Larmor pre-precession frequency (H0 is the bias magnetic field strength); ω is the operating angular frequency; μ is the transverse permeability component; μ z The longitudinal permeability component (μ under saturation) z ≈1); κ is the gyromagnetic coupling coefficient, which is related to the bias field strength and material properties; j is the imaginary unit, representing the complex form of the permeability. If the bias magnetic field is located in the xy plane, the tensor form needs to be adjusted through coordinate rotation transformation.

[0014] Preferably, the microstrip patch unit is a square patch with a cross-shaped slit etched on the center surface of the patch. The cross-shaped slit divides the patch into four symmetrical sub-units, and the power supply point is located at a set offset from the center to excite orthogonal modes and optimize the excitation efficiency of orthogonal modes.

[0015] Preferably, there is a spacing between adjacent electromagnetic coils to reduce mutual inductance; each group of electromagnetic coils corresponds to the magnetic field directions of 0°, 90°, 180°, and 270° respectively, and is wound in reverse series to form a four-pole symmetrical magnetic field distribution.

[0016] Preferably, the drive control unit includes an STM32 microcontroller, an L298N H-bridge driver chip, and an HMC1021 magnetoresistive sensor; wherein, the microcontroller generates a bidirectional pulse current through pulse width modulation, which generates a controllable magnetic field through the H-bridge driver chip; and the magnetoresistive sensor provides real-time feedback on the magnetization state of the ferrite.

[0017] Preferably, the polarization modes include linear polarization mode, circular polarization mode, and closed-loop feedback control algorithm mode; wherein,

[0018] The linear polarization mode is used to enable the antenna to match signals with different polarization characteristics, thereby improving the resistance to multipath fading and communication quality.

[0019] The circular polarization mode is used to reduce polarization mismatch loss of signals in complex environments and improve the received signal-to-noise ratio.

[0020] The closed-loop feedback control algorithm is used to monitor the magnetization intensity in real time and dynamically adjust the coil current to ensure that the polarization direction is less than the error value.

[0021] Preferably, the switching condition of the linear polarization mode is: when Hx >H y And H x When H > 0, 0° linear polarization is excited; when H y >H x And H y When H > 0, 90° linear polarization is excited; by adjusting H x With H y The ratio allows for linear polarization at any angle.

[0022] Preferably, the switching condition for the circular polarization mode is: when H x =H y Furthermore, with a phase difference of 90°, it excites left-handed / right-handed circular polarization with an ellipticity error of <0.8dB.

[0023] Preferably, the switching condition for the closed-loop feedback control algorithm mode is: adopting a PID control strategy, based on the magnetization M... x M y Dynamically adjust the electromagnetic coil current to ensure that the polarization direction error is <1°; where M x and M y These represent the x-axis and y-axis magnetization intensity measured by the magnetoresistive sensor, respectively, and are used for closed-loop feedback.

[0024] This invention overcomes the shortcomings of existing technologies and provides a polarization-reconfigurable microstrip patch system based on a ferrite substrate. The system includes an antenna body and a drive control unit. The antenna body includes a ferrite substrate, microstrip patch units etched on the ferrite substrate, and four sets of electromagnetic coils arranged around the edge of the ferrite substrate. The drive control unit is used to generate a synthetic magnetic field in the ferrite substrate by controlling the current direction and magnitude of the four sets of coils, thereby changing the equivalent impedance and surface current distribution of the microstrip patch, and thus changing the polarization mode of the antenna.

[0025] In this invention, the principle of dynamic adjustment of the permeability tensor is as follows: the resultant magnetic field component H along the x-axis x The combined magnetic field component H along the y-axis y Controlled by the current difference of four sets of electromagnetic coils, measured in A / m; the direction and magnitude of the current in the 0° and 180° coils, and the 90° and 270° coils are adjusted (e.g., H) via an STM32 microcontroller. x H is determined by the current difference between the 0° and 180° coils. y The combined magnetic field is generated in the ferrite substrate by the current difference between the 90° and 270° coils. Among them, H x Hy is determined by the current difference between the 0° and 180° coils, and Hy is determined by the current difference between the 90° and 270° coils. When the ferrite substrate is biased by a static magnetic field, its permeability tensor exhibits gyrotropic properties, as follows:

[0026]

[0027] Where μ is the transverse permeability component; μ z κ represents the longitudinal permeability component; κ represents the gyromagnetic coupling coefficient, which is related to the bias field strength and material properties; j is the imaginary unit (corresponding to e^(-j / kJ). jωt (Time harmonic convention). Therefore, the permeability tensor components μ and κ of the ferrite substrate change with H. x H y The changes alter the equivalent impedance and surface current distribution of the microstrip patch.

[0028] Given that the composite magnetic field lies in the xy plane:

[0029] When the principal bias direction is the x-axis, the permeability tensor transformation is:

[0030]

[0031] When the principal bias direction is the y-axis, the permeability tensor transformation is:

[0032]

[0033] This transformation matches the actual geometric configuration, enabling dynamic adjustment of the permeability tensor.

[0034] In this invention, the polarization mode logic of the antenna is specifically as follows:

[0035] (1) Linear polarization mode switching

[0036] This linear polarization mode is used to dynamically adjust the linear polarization direction (such as 0°, 90°, 45°, etc.) so that the antenna can match signals with different polarization characteristics, thereby improving the ability to resist multipath fading and the quality of communication.

[0037] The switching condition is: when H x >H y And H x When the current difference is greater than 0, the excitation (control mechanism: by adjusting the current difference of the four sets of coils, different proportions of H are generated) is activated. x and H y For example: when H x >H y And H x When H > 0, 0° linear polarization is excited in the x-axis direction; when H y >H x And H y When H > 0, a 90° linear polarization is excited in the y-axis direction. 0° linear polarization (x-axis direction); when H y >H x And H yWhen H > 0, 90° linear polarization (y-axis direction) is excited; by adjusting H x With H y The ratio allows for linear polarization at any angle (e.g., 45°, 135°).

[0038] (2) Generation of circular polarization mode

[0039] Circular polarization can reduce polarization mismatch loss in complex environments (such as multipath propagation and mobile communications), improving the received signal-to-noise ratio. For example, left-hand / right-hand circular polarization can meet the needs of satellite communications or UAV links. The switching condition is that when H... x =H y Furthermore, the phase difference is 90° (achieved through alternating pulse timing), which excites left-handed / right-handed circular polarization with an ellipticity error of <0.8dB.

[0040] (3) Closed-loop feedback control algorithm mode

[0041] The closed-loop feedback control algorithm mode monitors the magnetization intensity M in real time. x and M y The current in the electromagnetic coil is dynamically adjusted to ensure that the polarization direction error is less than 1°, thus improving the control accuracy. The switching condition is: when the magnetoresistive sensor detects that the deviation between the actual magnetization state and the target value exceeds a threshold, PID closed-loop control is automatically activated. Specifically, a PID control strategy is adopted (the proportional coefficient K of the PID control...). p =0.6, integration time T i = 0.08s, differential time T d =0.02s), based on the magnetization intensity M measured by the magnetoresistive sensor x M y Dynamically adjust the coil current to ensure that the polarization direction error is less than 1°.

[0042] Compared with the shortcomings and deficiencies of existing technologies, the present invention has the following beneficial effects:

[0043] (1) Flexible polarization modes: Supports 0°~360° linear polarization and left-hand / right-hand circular polarization to meet the communication needs of multiple scenarios;

[0044] (2) Low power consumption operation: After the pulse current is turned off, the polarization state is maintained by the residual magnetism of the ferrite, and the steady-state power consumption is reduced to the microwatt level.

[0045] (3) High integration: The coil and microstrip patch are designed on the same substrate, which reduces the volume by 30% compared with traditional switched polarized antennas.

[0046] (4) Strong anti-interference capability: By dynamically matching the target polarization, the received signal-to-noise ratio is improved by 5-8dB in multipath fading scenarios. Attached Figure Description

[0047] Figure 1 This is a structural diagram of the polarization reconfigurable microstrip patch antenna of the present invention;

[0048] Figure 2 This is a schematic diagram of the power supply module in the system drive control unit of the present invention; wherein, A is a 12V to 5V power supply circuit, used to power the magnetoresistive sensor; B is a 12V to 3.3V power supply circuit, used to power the active circuit (STM32 microcontroller) and the H-bridge circuit.

[0049] Figure 3 It is the main control module and the magnetic sensor signal modulation circuit;

[0050] Figure 4 This is a schematic diagram of the circuit structure of the coil H-bridge drive circuit. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] This invention discloses a polarization reconfigurable microstrip patch antenna system based on a ferrite substrate, the system comprising an antenna body and a drive control unit.

[0053] In this embodiment of the invention, the structure of the antenna body is as follows: Figure 1 As shown, the antenna body includes a ferrite substrate, a microstrip patch unit etched on the ferrite substrate, and four sets of electromagnetic coils arranged around the edge of the ferrite substrate.

[0054] The ferrite substrate was prepared by a casting method, specifically using high rectangularity ratio lithium ferrite (Li-MnFe2O2) as the material, with a thickness h = 0.8 mm, dimensions of 30 mm × 30 mm × 0.8 mm, a loss tangent tanδ = 0.001, and a dielectric constant ε. r =15, saturation magnetization 4πM s =2000Gs, the permeability tensor is:

[0055]

[0056] Where μ is the transverse permeability component; μ z κ represents the longitudinal permeability component; κ represents the gyromagnetic coupling coefficient, which is related to the bias field strength and material properties; j is the imaginary unit (corresponding to e^(-j / kJ). jωt (Time Harmonic Convention)

[0057] The microstrip patch unit is a square patch with a side length L = 15 mm, made of 0.035 mm thick copper foil. A cross-shaped slit with a width w = 0.5 mm and a depth d = 7 mm is etched on the surface, dividing the patch into four symmetrical sub-units. The patch is fed by a 50-ohm microstrip line at a point offset from the center at (x0, y0) = (2 mm, 2 mm), used to excite orthogonal modes and optimize the excitation efficiency of orthogonal modes. X and Y coordinates are plotted on the cross-shaped slit; the x-axis corresponds to the 0° and 180° magnetic field directions, and the y-axis corresponds to the 90° and 270° magnetic field directions.

[0058] The electromagnetic coil is wound with enameled wire, and the inductance of a single coil is L. c =60μH, DC resistance R c =4.5Ω, with a spacing of s=2mm to reduce mutual inductance. The four sets of electromagnetic coils are 1mm away from the edge of their adjacent substrates. Each set of electromagnetic coils corresponds to the magnetic field directions of 0°, 90°, 180°, and 270°, respectively. Each set of coils has N=80 turns and a wire diameter of 0.25mm. They are wound in reverse series to form a four-pole symmetrical magnetic field distribution.

[0059] In this embodiment of the invention, the drive control unit is used to generate a synthetic magnetic field in the ferrite substrate by controlling the current direction and magnitude of the four sets of coils, thereby changing the equivalent impedance and surface current distribution of the microstrip patch, and thus changing the polarization mode of the antenna.

[0060] Specifically, the drive control unit, such as Figures 2-4 As shown, the system includes an STM32 microcontroller, an L298N H-bridge driver chip, and an HMC1021 magnetoresistive sensor. The power supply module for this driver control unit is as follows: an input DC voltage of 12V, regulated by an LM7805 to supply 5V to the microcontroller; the H-bridge driver power supply directly uses 12V. The STM32 microcontroller is used for current control, outputting a 10kHz PWM signal (duty cycle 0-100%), which controls the coil current direction through the INA and INB pins of the L298N. OUT1 and OUT2 are connected to the two ends of the coil. The microcontroller generates a bidirectional pulse current (peak current I) through pulse width modulation (PWM). p =1.5A, pulse width T p =80μs), a controllable magnetic field is generated by the H-bridge driver chip. The HMC1021 magnetoresistive sensor is used for state monitoring and provides real-time feedback on the magnetization state of the ferrite. The HMC1021 magnetoresistive sensor is attached to the center of the ferrite substrate and transmits the magnetic field strength M in the x-axis direction in real time via the I2C interface. x Magnetic field strength M along the y-axis y The data.

[0061] In this embodiment of the invention, the switching logic for the antenna polarization mode is specifically as follows:

[0062] (1) Linear polarization mode switching

[0063] Linear polarization modes are used to dynamically adjust the linear polarization direction (such as 0°, 90°, 45°, etc.) so that the antenna can match signals with different polarization characteristics, thereby improving the ability to resist multipath fading and the quality of communication.

[0064] The switching condition is: when H x >H y And H x When H > 0, 0° linear polarization (x-axis direction) is excited; when H y >H x And H y When H > 0, 90° linear polarization (y-axis direction) is excited; by adjusting H x With H y The ratio allows for linear polarization at any angle (e.g., 45°, 135°).

[0065] Control mechanism: By adjusting the current difference of the four sets of coils, different proportions of H are generated. x and H y For example: when H x >H y And H x When H > 0, 0° linear polarization is excited in the x-axis direction; when H y >H x And H y When the value is greater than 0, 90° linear polarization is excited in the y-axis direction.

[0066] (2) Generation of circular polarization mode

[0067] Circular polarization can reduce polarization mismatch loss in complex environments (such as multipath propagation and mobile communications) and improve the received signal-to-noise ratio. For example, left-hand / right-hand circular polarization can meet the needs of satellite communications or UAV links.

[0068] The switching condition is: when H x =H y Furthermore, the phase difference is 90° (achieved through alternating pulse timing), which excites left-handed / right-handed circular polarization with an ellipticity error of <0.8dB.

[0069] Control mechanism: Similar to the linear polarization mode, H is generated by adjusting the current difference between the four sets of coils. x =H y The synthesized magnetic field, and by controlling the timing of the current pulses, makes H x and H y A 90° phase difference is generated between the components, thereby exciting circular polarization.

[0070] (3) Closed-loop feedback control algorithm mode switching

[0071] In the closed-loop feedback control algorithm mode, the magnetization intensity M is monitored in real time. x and M y The coil current is dynamically adjusted to ensure that the polarization direction error is less than 1°, thereby improving the control accuracy.

[0072] The switching condition is as follows: when the magnetoresistive sensor detects that the deviation between the actual magnetization state and the target value exceeds a threshold, PID closed-loop control is automatically activated. Specifically, a PID control strategy is adopted (proportional coefficient K). p =0.6, integration time T i = 0.08s, differential time T d =0.02s), based on the magnetization intensity M measured by the magnetoresistive sensor x M y Dynamically adjust the coil current to ensure that the polarization direction error is less than 1°.

[0073] Control mechanism: Similar to the linear polarization mode, H is changed by adjusting the current difference between the four sets of coils. x and H y However, a closed-loop feedback loop was added to adjust the current in real time based on sensor feedback, so as to precisely maintain the required H. x and H y The proportional and phase relationships are used to stabilize the polarization state of the antenna.

[0074] The system in the embodiments of the present invention is simulated and tested for verification, specifically as follows:

[0075] (1) Electromagnetic simulation

[0076] The model was built using CST Studio Suite, and the ferrite permeability tensor parameters were set to simulate the antenna reflection coefficient (bandwidth > 10% for VSWR < 2.0), gain (linear polarization gain > 6dBi, circular polarization gain > 5dBi), and polarization isolation (orthogonal linear polarization isolation > 25dB) under different magnetic fields.

[0077] (2) Measured results

[0078] Polarization switching time < 2µs, steady-state power consumption < 0.5mW (standby power consumption of sensor and MCU only), and realizes 0°, 90°, ±45° linear polarization and left-hand / right-hand circular polarization switching in the 2.4GHz band.

[0079] The theoretical isolation of orthogonally polarized signals is approximately 20–30 dB, which can suppress multipath interference. According to the formula: Interference suppression gain ≈ 10log 10(1 + orthogonal polarization isolation), thus it can be inferred that the signal-to-noise ratio of the present invention is improved by about 5 to 8 dB. In addition, the polarization reconfigurable antenna of the present invention has a good dynamic matching advantage, reducing polarization mismatch loss (typically 3 to 6 dB) by switching polarization in real time (such as matching the polarization of the direct signal).

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polarization-reconfigurable microstrip patch antenna system based on a ferrite substrate, characterized in that, The system includes an antenna body and a drive control unit. The antenna body includes a ferrite substrate, a microstrip patch unit etched on the ferrite substrate, and four sets of electromagnetic coils arranged around the edge of the ferrite substrate. The drive control unit is used to generate a synthetic magnetic field in the ferrite substrate by controlling the current direction and magnitude of the four sets of coils, thereby changing the equivalent impedance and surface current distribution of the microstrip patch, and thus changing the polarization mode of the antenna.

2. The system as described in claim 1, characterized in that, The permeability tensor expression of the ferrite substrate is as follows: Analytical expression under lossless approximation: in, This represents the characteristic angular frequency of magnetization determined by the saturation magnetization of the ferrite substrate. This represents the saturation magnetization intensity when the ferrite substrate reaches magnetic saturation. ω represents the gyromagnetic ratio. M =γM s ω0 = γμ0H0 is the Larmor pre-precession frequency, H0 is the bias magnetic field strength; ω is the operating angular frequency; μ is the transverse permeability component; μ z μ is the longitudinal permeability component in the saturation state. z ≈1; κ is the gyromagnetic coupling coefficient, which is related to the bias field strength and material properties; j is the imaginary unit, which reflects the complex form of the permeability. If the bias magnetic field is located in the xy plane, the tensor form is adjusted by coordinate rotation transformation.

3. The system as described in claim 1, characterized in that, The microstrip patch unit is a square patch with a cross-shaped slit etched on the center surface. The cross-shaped slit divides the patch into four symmetrical sub-units. The power supply point is located at a set offset from the center to excite orthogonal modes and optimize the excitation efficiency of orthogonal modes.

4. The system as described in claim 1, characterized in that, There is a spacing between adjacent electromagnetic coils to reduce mutual inductance; each group of electromagnetic coils corresponds to the magnetic field directions of 0°, 90°, 180° and 270° respectively, and is wound in reverse series to form a four-pole symmetrical magnetic field distribution.

5. The system as described in claim 1, characterized in that, The drive control unit includes an STM32 microcontroller, an L298N H-bridge driver chip, and an HMC1021 magnetoresistive sensor. The microcontroller generates a bidirectional pulse current through pulse width modulation, which is then used by the H-bridge driver chip to generate a controllable magnetic field. The magnetoresistive sensor provides real-time feedback on the magnetization state of the ferrite.

6. The system as described in claim 5, characterized in that, The polarization modes include linear polarization mode, circular polarization mode, and closed-loop feedback control algorithm mode; wherein... The linear polarization mode is used to enable the antenna to match signals with different polarization characteristics, thereby improving the resistance to multipath fading and communication quality. The circular polarization mode is used to reduce polarization mismatch loss of signals in complex environments and improve the received signal-to-noise ratio. The closed-loop feedback control algorithm is used to monitor the magnetization intensity in real time and dynamically adjust the coil current to ensure that the polarization direction is less than the error value.

7. The system as described in claim 6, characterized in that, The switching condition for the linear polarization mode is: when H x >H y And H x When H > 0, 0° linear polarization is excited; when H y >H x And H y When H > 0, 90° linear polarization is excited; by adjusting H x With H y The ratio allows for linear polarization at arbitrary angles; H x H represents the magnetic field strength component along the x-axis of the combined magnetic field formed by the four sets of electromagnetic coils in the ferrite substrate; y This represents the magnetic field strength component along the y-axis of the combined magnetic field formed by the four sets of electromagnetic coils in the ferrite substrate.

8. The system as described in claim 6, characterized in that, The switching condition for the circular polarization mode is: when H x = H y Furthermore, with a phase difference of 90°, it excites left-handed / right-handed circular polarization with an ellipticity error of <0.8dB; H x H represents the magnetic field strength component along the x-axis of the combined magnetic field formed by the four sets of electromagnetic coils in the ferrite substrate; y This represents the magnetic field strength component along the y-axis of the combined magnetic field formed by the four sets of electromagnetic coils in the ferrite substrate.

9. The system as described in claim 6, characterized in that, The switching condition for the closed-loop feedback control algorithm mode is as follows: A PID control strategy is adopted, based on the magnetization M... x M y Dynamically adjust the electromagnetic coil current to ensure that the polarization direction error is <1°; Among them, M x and M y These represent the x-axis and y-axis magnetization intensity measured by the magnetoresistive sensor, respectively, and are used for closed-loop feedback.

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