Polarization reconfigurable microstrip patch antenna system based on ferrite substrate

Abstract

The invention discloses a polarized reconfigurable microstrip patch antenna system based on a ferrite substrate. The system comprises an antenna body and a driving control unit, the antenna body comprises a ferrite substrate, a microstrip patch unit etched on the ferrite substrate and four groups of electromagnetic coils arranged around the edge of the ferrite substrate; and the driving control unit is used for generating a synthetic magnetic field in the ferrite substrate by controlling the current direction and magnitude of the four groups of coils, so that the equivalent impedance and surface current distribution of the microstrip patch are changed, and the polarization mode of the antenna is further changed. The system has the advantages of flexible polarization mode, low power consumption in operation, high integration level, strong anti-interference capability and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wireless communication antennas, and particularly relates to a polarization reconfigurable microstrip patch antenna system based on a ferrite substrate. BACKGROUND

[0002] Microstrip patch antennas are widely used due to their compact structure and easy integration, but the polarization direction (such as linear polarization and circular polarization) of traditional microstrip antennas is usually fixed, which is difficult to adapt to the signal transmission requirements in complex electromagnetic environments. For example, when there is multipath fading or target polarization characteristic change in the communication link, the gain and anti-interference ability of the fixed polarization antenna will be significantly reduced. The existing polarization reconfigurable technology and its defects are mainly as follows:

[0003] 1. Loading electronic switching devices: such as PIN diodes and varactor diodes, which change the antenna structure (such as slots and branches) by switching state, but have problems such as high power consumption (continuous power supply), narrow bandwidth (<5%), and low reliability;

[0004] 2. Mechanical adjustment structure: such as rotating antenna units, which have defects such as slow response speed (>10ms), large volume, and easy wear;

[0005] 3. New material regulation: ferrite material can change the electromagnetic response of the antenna through external magnetic field due to its magnetic control spin magnetic characteristics (magnetic permeability tensor can be adjusted), but its application in microstrip antennas faces the following challenges: uneven magnetic field distribution leads to insufficient polarization regulation accuracy; the impedance matching efficiency of traditional ferrite substrate and microstrip patch is low; and there is a lack of quantitative analysis of the coupling relationship between the magnetic permeability tensor and the polarization mode.

[0006] Therefore, there is an urgent need for a low-power, high-precision polarization reconfigurable microstrip patch antenna design method based on a ferrite substrate. SUMMARY

[0007] The purpose of the present application 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] The present application is implemented as follows: a polarization reconfigurable microstrip patch antenna system based on a ferrite substrate, the system comprising an antenna body and a driving control unit; the antenna body comprises a ferrite substrate, a microstrip patch unit etched on the ferrite substrate, and four groups of electromagnetic coils arranged around the edge of the ferrite substrate; the driving control unit is used to generate a combined 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.

[0009] Preferably, the magnetic 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 precession frequency (H0 is the bias magnetic field strength); ω is the operating angular frequency; μ is the transverse magnetic permeability component; μ z is the longitudinal magnetic permeability component (μ z ≈ 1 under saturation); κ is the gyromagnetic coupling coefficient, related to the bias field strength and material properties; j is the imaginary unit, embodying the complex form of magnetic permeability. If the bias magnetic field is located in the x-y plane, a coordinate rotation transformation is needed to adjust the tensor form.

[0014] Preferably, the microstrip patch unit is a square patch, a cross-shaped slot is etched on the center surface of the patch, the cross-shaped slot divides the patch into four symmetric sub-units, and a feed point is located at a set offset of the center to excite orthogonal modes and optimize orthogonal mode excitation efficiency.

[0015] Preferably, there is a spacing between adjacent electromagnetic coils for reducing mutual inductance; each group of electromagnetic coils corresponds to a magnetic field direction of 0°, 90°, 180° and 270°, respectively, and adopts reverse series winding to form a four-pole symmetric magnetic field distribution.

[0016] Preferably, the driving control unit comprises an STM32 microcontroller, an L298N type H-bridge driving chip and an HMC1021 magnetoresistance sensor; wherein the microcontroller generates a bidirectional pulse current through pulse width modulation, and a controllable magnetic field is generated through the H-bridge driving chip; the magnetoresistance sensor feeds back the magnetization state of the ferrite in real time.

[0017] Preferably, the polarization mode comprises a linear polarization mode, a circular polarization mode and a 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, improve the anti-multipath fading capability 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 mode is used to monitor the magnetization intensity in real time, dynamically adjust the coil current and ensure that the polarization direction is less than an error value.

[0021] Preferably, the switching condition of the linear polarization mode is that when Hx <H y >0, excite 0° linear polarization; when H x >0, excite 90° linear polarization; by adjusting the ratio of H y >H x >0, excite 90° linear polarization; by adjusting the ratio of H y >0, excite 90° linear polarization; by adjusting the ratio of H x and H y , realize linear polarization of any angle.

[0022] Preferably, the switching condition of the circular polarization mode is: when H x =H y and the phase difference is 90°, excite left-handed / right-handed circular polarization, and the ellipticity error is <0.8dB.

[0023] Preferably, the switching condition of the closed-loop feedback control algorithm mode is: using a PID control strategy, dynamically adjusting the electromagnetic coil current according to the magnetization M x and M y , to ensure that the polarization direction error is <1°; wherein M x and M y respectively represent the x-axis and y-axis magnetization measured by the magnetoresistance sensor, which is used for closed-loop feedback.

[0024] The present application overcomes the shortcomings of the prior art and provides a polarization reconfigurable microstrip patch system based on a ferrite substrate, which comprises an antenna body and a driving control unit; the antenna body comprises a ferrite substrate, a microstrip patch unit etched on the ferrite substrate, and four groups of electromagnetic coils arranged around the edges of the ferrite substrate; the driving control unit is used to generate a resultant 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.

[0025] In the present application, the permeability tensor dynamic adjustment principle is: the x-axis component H x of the resultant magnetic field and the y-axis component H y of the resultant magnetic field are controlled by the current difference of the four groups of electromagnetic coils, and the unit is A / m; by adjusting the current direction and size of the 0° and 180° coils and the 90° and 270° coils (for example, H x is determined by the current difference of the 0° and 180° coils, and H y is determined by the current difference of the 90° and 270° coils) through an STM32 microcontroller, a resultant magnetic field H is generated in the ferrite substrate. x wherein H x is determined by the current difference of the 0° and 180° coils, and H x is determined by the current difference of the 90° and 270° coils; when the ferrite substrate is biased by a static magnetic field, its permeability tensor exhibits gyrotropic characteristics, which is in the following form:

[0026]

[0027] where μ is the transverse permeability component; μ z is 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 jωt time harmonic convention). Therefore, the permeability tensor components μ and κ of the ferrite substrate vary with H x , H y , thereby changing the equivalent impedance of the microstrip patch and the surface current distribution.

[0028] Given that the synthetic magnetic field is in the x-y plane:

[0029] When the biasing main direction is the x-axis, the permeability tensor is transformed as:

[0030]

[0031] When the biasing main direction is the y-axis, the permeability tensor is transformed as:

[0032]

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

[0034] In the present application, the polarization mode logic of the antenna is specifically:

[0035] (1) Linear polarization mode switching

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

[0037] The switching condition is: when H x > H y and H x > 0, 0° linear polarization in the x-axis direction is excited (control mechanism: by adjusting the current difference of the four coils, different proportions of H x and H y are generated. For example: when H x > H y and H x > 0, 0° linear polarization in the x-axis direction is excited; when H y > H x and H y > 0, 90° linear polarization in the y-axis direction is excited. 0° linear polarization (x-axis direction); when H y > H x and H y> 0, excite 90° linear polarization (y-axis direction); by adjusting H x With the ratio of H y , any angle linear polarization (such as 45°, 135°) can be achieved.

[0038] (2) Circular polarization mode generation

[0039] Circular polarization can reduce polarization mismatch loss of signals in complex environments (such as multipath propagation, mobile communication), and improve the received signal-to-noise ratio. For example, left-handed / right-handed circular polarization can meet the needs of satellite communication or unmanned aerial vehicle link. The switching condition is that when H x = H y and the phase difference is 90° (achieved by alternating pulse timing), left-handed / right-handed circular polarization is excited, and the ellipticity error is < 0.8 dB.

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

[0041] The closed-loop feedback control algorithm mode is to monitor the magnetization M x and M y in real time, dynamically adjust the current of the electromagnetic coil, and ensure that the polarization direction error is less than 1°, thereby improving the control accuracy. The switching condition is that when the magnetic resistance sensor detects that the actual magnetization state deviates from the target value by more than a threshold value, the PID closed-loop control is automatically enabled. Specifically, a PID control strategy (the proportional coefficient K p of the PID control is 0.6, the integral time T i is 0.08s, and the differential time T d is 0.02s) is adopted, the coil current is dynamically adjusted according to the magnetization M x , M y measured by the magnetic resistance sensor, and the polarization direction error is ensured to be < 1°.

[0042] Compared with the shortcomings and deficiencies of the prior art, the present application has the following beneficial effects:

[0043] (1) Flexible polarization mode: supports 0°-360° linear polarization and left-handed / right-handed circular polarization, meeting the communication needs of multiple scenarios;

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

[0045] (3) High integration: the coil and the microstrip patch are designed on the same substrate, and the volume is reduced by 30% compared with traditional switch-type polarization antennas.

[0046] (4) Strong anti-interference ability: by dynamically matching the target polarization, the received signal-to-noise ratio is improved by 5-8 dB in multipath fading scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a structure diagram of a polarized reconfigurable microstrip patch antenna of the application;

[0048] Figure 2 is a circuit structure schematic diagram of a power module in a system drive control unit; wherein A is a 12V to 5V power circuit, used for powering a magnetic resistance sensor; B is a 12V to 3.3V power circuit, used for powering a main circuit (STM32 microcontroller) and an H-bridge circuit;

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

[0050] Figure 4 is a circuit structure schematic diagram of a coil H-bridge drive circuit. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the application more clear, the application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0052] The application discloses a polarized reconfigurable microstrip patch antenna system based on a ferrite substrate, which comprises an antenna body and a drive control unit.

[0053] In the embodiment of the application, the structure of the antenna body is as shown in Figure 1 The antenna body comprises a ferrite substrate, a microstrip patch unit etched on the ferrite substrate, and four groups of electromagnetic coils arranged around the edges of the ferrite substrate.

[0054] The ferrite substrate is prepared by a flow casting method. Specifically, high-aspect-ratio lithium ferrite (Li-MnFe2O2) is used as the material, the thickness h is 0.8 mm, the size is 30 mm x 30 mm x 0.8 mm, the loss tangent tanδ is 0.001, the dielectric constant ε r is 15, the saturation magnetization 4πM s is 2000Gs, and the permeability tensor is:

[0055]

[0056] wherein μ is a transverse permeability component; μ z is a longitudinal permeability component; κ represents a gyromagnetic coupling coefficient, which is related to the bias field strength and material properties; and j is an imaginary unit (corresponding to the e 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 to 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 the embodiments of the present application, the switching logic of the polarization mode of the antenna is specifically:

[0062] (1) Linear polarization mode switching

[0063] The linear polarization mode is used to match signals with different polarization characteristics by dynamically adjusting the linear polarization direction (such as 0°, 90°, 45°, etc.), so as to improve the anti-multipath fading ability and communication quality.

[0064] The switching condition is: when H x >H y and H x >0, 0° linear polarization (x-axis direction) is excited; when H y >H x and H y >0, 90° linear polarization (y-axis direction) is excited; by adjusting the ratio of H x and H y , any angle linear polarization (such as 45°, 135°) can be realized.

[0065] Control mechanism: by adjusting the current difference of the four groups of coils, different ratios of H x and H y are generated. For example: when H x >H y and H x >0, 0° linear polarization in the x-axis direction is excited; when H y >H x and H y >0, 90° linear polarization in the y-axis direction is excited.

[0066] (2) Circular polarization mode generation

[0067] The circular polarization mode can reduce the polarization mismatch loss of signals in complex environments (such as multipath propagation, mobile communication), and improve the received signal-to-noise ratio. For example, left-handed / right-handed circular polarization can meet the needs of satellite communication or unmanned aerial vehicle link.

[0068] The switching condition is: when H x = H y and the phase difference is 90° (realized by alternating pulse timing), left-handed / right-handed circular polarization is excited, and the ellipticity error is <0.8 dB.

[0069] Control mechanism: similar to the linear polarization mode, by adjusting the current difference of the four groups of coils, the combined magnetic field of H x = H y is generated, and by controlling the timing of the current pulse, a 90° phase difference between H x and H y components is generated, so as to excite circular polarization

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

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

[0072] The switching condition is that when the reluctance sensor detects that the actual magnetization state deviates from the target value by more than a threshold value, the PID closed-loop control is automatically enabled. Specifically, a PID control strategy (proportional coefficient K p = 0.6, integral time T i = 0.08s, and differential time T d = 0.02s) is used to dynamically adjust the coil current according to the magnetization M x and M y measured by the reluctance sensor, to ensure that the polarization direction error is less than 1°.

[0073] Control mechanism: Similar to the linear polarization mode, the current difference of the four groups of coils is adjusted to change H x and H y , but a closed-loop feedback link is added to correct the current in real time according to the sensor feedback, to accurately maintain the required H x and H y proportion and phase relationship, thereby stabilizing the polarization state of the antenna.

[0074] The system in the embodiment of the application is simulated and tested and verified, specifically as follows:

[0075] (1) Electromagnetic simulation

[0076] A model is established using CST Studio Suite, the ferrite permeability tensor parameters are set, and the antenna reflection coefficient (bandwidth with standing wave ratio < 2.0 > 10%), gain (linear polarization gain > 6dBi, circular polarization gain > 5dBi), and polarization isolation (orthogonal linear polarization isolation > 25dB) under different magnetic fields are simulated.

[0077] (2) Actual measurement results

[0078] The polarization switching time is < 2us, the steady-state power consumption is < 0.5mW (only sensor and MCU standby power consumption), and 0°, 90°, ±45° linear polarization and left-handed / right-handed circular polarization switching are realized in the 2.4GHz frequency band.

[0079] The theoretical isolation of the orthogonal polarization signals is about 20-30dB, which can suppress multipath interference. According to the formula: interference suppression gain ≈ 10log 10(1+orthogonal polarization isolation), thus deducing that the signal-to-noise ratio of the application is improved by about 5-8dB. In addition, the polarization reconfigurable antenna of the application has good dynamic matching advantage, and the polarization mismatch loss (typical value 3-6dB) is reduced by real-time switching of polarization (such as matching direct signal polarization).

[0080] The above merely describes preferred embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

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 the lossless approximation: 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 μ is the longitudinal permeability component 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, 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 any angle.

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.

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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