Polarization reconfigurable self-oscillating active antenna

Abstract

The invention discloses a polarization reconfigurable self-oscillating active antenna, comprising a dielectric substrate, a field effect tube, a microstrip line, a capacitor, a semi-ring microstrip antenna, a switching diode, a right-hand circular polarization monopole antenna, a left-hand circular polarization monopole antenna, a DC bias circuit and a metal grounding plate. The invention has a simple structure and a small volume, and can switch between linear polarization, right-hand circular polarization and left-hand circular polarization.

Description

Technical Field

[0001] The invention belongs to the technical field of active antennas, and in particular relates to a polarization reconfigurable self-oscillating active antenna. Background Art

[0002] In modern wireless communication systems, integrating multiple subsystems into one module is the key to making the system compact and portable. As the design and placement of antennas are getting closer to the active circuits on the chip or package, active integrated antennas that integrate antennas and active circuits have emerged as a new generation of antennas. The integrated design enables the system to have higher performance and more compact size, which makes active integrated antennas have great application potential in 5G systems. Self-oscillating active antennas are a widely used active integrated antenna that relies on an oscillating circuit to provide a non-modulated RF source and transmit signals through an integrated antenna. It can be used in broadcasting, wireless power transmission, and wireless charging applications. For applications that do not require locking the carrier frequency, self-oscillating active antennas provide a compact and low-cost solution that can be used for long-range wireless power transmission in multi-carrier RFID systems and Internet of Things systems.

[0003] Reconfigurable antennas can dynamically adjust their operating frequency or radiation characteristics according to system requirements and the surrounding environment, so that one or more of the antenna's parameters such as frequency, radiation pattern, polarization mode, etc. can be reconfigured. In order to achieve reconfigurability, the antenna needs to use some RF switching devices, such as PIN diodes, photoconductive switches, micro-electromechanical switches, etc. The research on reconfigurable self-oscillating active antennas is mainly concentrated in developed countries abroad. At present, most of the results are based on frequency reconfiguration, switching the oscillation frequency of the self-oscillating active antenna in a discrete or continuous form. Some studies combine frequency reconfiguration and radiation pattern reconfiguration to provide a two-dimensional reconfigurable function. Research on polarization reconfiguration is still very rare. Summary of the invention

[0004] The purpose of the present invention is to provide a polarization reconfigurable self-oscillating active antenna, which realizes switching of multiple polarization modes with a compact structure.

[0005] The technical solution for achieving the purpose of the present invention is: a polarization reconfigurable self-oscillating active antenna, comprising a dielectric substrate, a field effect transistor, a microstrip line, a capacitor, a semi-ring microstrip antenna, a switching diode, a right-hand circularly polarized monopole antenna, a left-hand circularly polarized monopole antenna, a DC bias circuit, and a metal ground plate;

[0006] The two sources of the field effect tube are connected to the two output ends of the DC bias circuit in one-to-one correspondence, and the gate and the drain are connected to the input end of a microstrip line respectively; the output end of each microstrip line is connected to the anode of a switching diode, the cathodes of the two switching diodes are connected to the other two output ends of the DC bias circuit, and are respectively connected to the right-hand circular polarization monopole antenna and the left-hand circular polarization monopole antenna; each microstrip line includes a first transmission line, a second transmission line, and a third transmission line connected in sequence, and the first transmission line and the second transmission line, as well as the second transmission line and the third transmission line are connected through a capacitor; the two ends of the semi-ring microstrip antenna are connected to the two second transmission lines in one-to-one correspondence, and the two first transmission lines are respectively vertically connected to the two output ends of the DC bias circuit.

[0007] Preferably, the two microstrip lines and the four capacitors are symmetrically structured with the two source lines of the field effect transistor as the axis, the input ends of the two first transmission lines are respectively connected to the gate and drain of the field effect transistor, and the output ends of the two third transmission lines are respectively connected to the anodes of the two switching diodes one by one.

[0008] Preferably, the DC bias circuit includes a field effect transistor drain pad, a gate pad, two switch diode anode pads, eight metallized through holes penetrating the dielectric substrate, two source pads, and six choke lines, which are disposed on the back of the dielectric substrate;

[0009] The drain pad, gate pad and anode pads of the field effect tube on the back of the dielectric substrate are all etched with rectangular gaps for isolating the DC voltage. They are respectively connected to the input ends of the four choke lines on the front of the dielectric substrate through the metallized through holes at the center, and the positions are symmetrical and the sizes are the same. The other ends of the choke lines are respectively connected to the two first transmission lines and the two third transmission lines. The two choke lines connected to the third transmission lines are bent to reduce the area. The input ends of the other two choke lines each have a metallized through hole at the center, and the output ends are respectively connected to the cathodes of the two switching diodes and are bent. The two source pads on the front of the dielectric substrate are respectively connected to the two sources of the field effect tube, and each has a metallized through hole at the center.

[0010] Preferably, the length of the choke line is 1 / 4 of the medium wavelength corresponding to the target design frequency.

[0011] Preferably, the left-hand circularly polarized monopole antenna comprises a monopole branch disposed on the front side of the dielectric substrate and an inverted L-shaped branch disposed on the back side of the dielectric substrate;

[0012] The left-handed circularly polarized monopole branch is connected to the cathode of a switching diode and vertically connected to a bent choke line, and the inverted L-shaped branch is connected to a metal ground plate.

[0013] Preferably, the right-hand circularly polarized monopole antenna has a bent structure, and its total length is 1 / 4 of the medium wavelength of the target design frequency.

[0014] Preferably, the total length of the left-hand circularly polarized monopole antenna is 1 / 4 of the medium wavelength corresponding to the target design frequency.

[0015] Preferably, the oscillation condition is satisfied:

[0016] |G BJT (jw0)| 2 ·|L ANT (jw0)| 2 ≥1 (1)

[0017] ∠|G BJT (jw0)·L ANT (jw0)|=2nπ,n=0,1,2... (2)

[0018] Among them, G BJT is the transistor voltage gain, L ANT is the antenna loss, w0 is the oscillation angular frequency.

[0019] Compared with the prior art, the present invention has the following significant advantages:

[0020] 1. The present invention provides switching of three polarization states, namely, linear polarization, left-hand circular polarization, and right-hand circular polarization, in the field of self-oscillating active antennas;

[0021] 2. In the present invention, the semi-loop microstrip antenna serves as a radiation element and a feedback path in different states, and has a compact structure;

[0022] 3. The present invention performs a bending process on the DC bias circuit to further reduce the overall area of ​​the circuit.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a top-level schematic diagram of the polarization reconfigurable self-oscillating active antenna of the present invention.

[0025] Figure 2 It is a bottom schematic diagram of the polarization reconfigurable self-oscillating active antenna of the present invention.

[0026] Figure 3 yes Figure 1 Schematic diagram of the dimensions of the top structure.

[0027] Figure 4 yes Figure 1 Schematic diagram of the dimensions of the mid- and bottom-layer structures.

[0028] Figure 5 It is the simulation result of the left-hand circular polarization pattern in the polarization reconfigurable self-oscillating active antenna of the present invention.

[0029] Figure 6 It is the simulation result of the linear polarization pattern of the polarization reconfigurable self-oscillating active antenna of the present invention.

[0030] Figure 7 It is the simulation result of the right-hand circular polarization pattern in the polarization reconfigurable self-oscillating active antenna of the present invention.

[0031] Figure 8 It is the test result of the left-hand circularly polarized oscillation output spectrum in the polarization reconfigurable self-oscillating active antenna of the present invention.

[0032] Fig. 9 It is the test result of the right-hand circularly polarized oscillation output spectrum in the polarization reconfigurable self-oscillating active antenna of the present invention.

[0033] Fig.10 It is the test result of the linear polarization oscillation output spectrum of the polarization reconfigurable self-oscillating active antenna of the present invention.

[0034] Fig.11 It is the test result of the left-hand circular polarization axis ratio in the polarization reconfigurable self-oscillating active antenna of the present invention.

[0035] Fig.12 It is the test result of the right-hand circular polarization axis ratio in the polarization reconfigurable self-oscillating active antenna of the present invention. DETAILED DESCRIPTION

[0036] like Figures 1-2 As shown, a polarization reconfigurable self-oscillating active antenna includes a dielectric substrate 1, a field effect tube 2, a microstrip line 3, a capacitor 4, a semi-ring microstrip antenna 5, a switching diode 6, a right-hand circularly polarized monopole antenna 7, a left-hand circularly polarized monopole antenna 8, a DC bias circuit 9, and a metal ground plane 10. The two sources of the field effect tube 2 are respectively connected to the two output ends of the DC bias circuit 9, the gate and the drain are respectively connected to the two input ends of the microstrip line 3, and the microstrip line 3 is respectively vertically connected to the other two output ends of the DC bias circuit 9. The four capacitors 4 are bridged with different connecting lines inside the microstrip line 3, one end of the semi-ring microstrip antenna 5 is connected between the two capacitors 4 on the gate side of the field effect tube 2, and the other end is connected between the two capacitors 4 on the drain side. The two output ends of the microstrip line 3 are respectively connected to the anodes of the two switching diodes 6, and the cathodes of the two switching diodes 6 are respectively connected to the other two output ends of the DC bias circuit 9, and are also respectively connected to the right-hand circularly polarized monopole antenna 7 and the left-hand circularly polarized monopole antenna 8.

[0037] like Figure 1As shown, in a further embodiment, the microstrip line 3 includes a first transmission line 31, a second transmission line 32, and a third transmission line 33;

[0038] The microstrip line 3 and the four capacitors 4 are symmetrically structured with the two source connection lines of the field effect tube 2 as the axis. The two first transmission lines 31 are respectively vertically connected to the two output ends of the DC bias circuit 9, and their input ends are respectively connected to the gate and drain of the field effect tube 2, and the output ends are respectively connected to one end of the two capacitors 4, and the other ends of the capacitors 4 are respectively connected to the input ends of the two second transmission lines 32, and the two ends of the semi-ring microstrip antenna 5 are connected to the second transmission lines 32. The output ends of the two second transmission lines 32 are respectively connected to one end of the other two capacitors 4, and the other ends of the capacitors 4 are respectively connected to the input ends of the two third transmission lines 33, and the output ends of the third transmission lines 33 are respectively connected to the anodes of the two switching diodes 6.

[0039] like Figures 1-2 As shown, in a further embodiment, the DC bias circuit 9 includes a field effect transistor drain pad 91, a gate pad 92, two switch diode anode pads 93, eight metallized through holes 94 penetrating the dielectric substrate 1, two source pads 95, and six choke lines 96 disposed on the front of the dielectric substrate 1;

[0040] The field effect tube drain pad 91, gate pad 92, and two switch diode anode pads 93 on the back of the dielectric substrate 1 are all etched with rectangular gaps on the periphery for isolating the DC voltage. They are respectively connected to the input ends of the four choke lines 96 on the front of the dielectric substrate 1 through the metallized through-holes (94) at the center, and the positions are symmetrical and the sizes are the same. The other ends of the choke lines 96 are respectively connected to the two first transmission lines 31 and the two third transmission lines 33. The two choke lines 96 connected to the third transmission lines 33 are bent to reduce the area. In addition, there is a metallized through-hole 94 at the center of the input end of each of the two choke lines 96, and the output ends are respectively connected to the cathodes of the two switch diodes 6, which are also bent. The two source pads 95 on the front of the dielectric substrate 1 are respectively connected to the two sources of the field effect tube 2, and there is a metallized through-hole 94 at the center of each.

[0041] like Figures 1-2 As shown, in a further embodiment, the left-hand circularly polarized monopole antenna 8 includes a monopole branch 81 disposed on the front surface of the dielectric substrate 1 and an inverted L-shaped branch 82 disposed on the back surface of the dielectric substrate 1;

[0042] The left-handed circularly polarized monopole branch 81 is connected to the cathode of a switching diode 6 and is vertically connected to a bent choke line 96 . The inverted L-shaped branch 82 is connected to the metal ground plate 10 .

[0043] Preferably, the length of the choke line (96) is approximately 1 / 4 of the medium wavelength corresponding to the target design frequency.

[0044] The size of the semi-ring microstrip antenna (5) is optimized using electromagnetic simulation software HFSS.

[0045] Preferably, the total length of the right-hand circularly polarized monopole antenna is approximately 1 / 4 of the medium wavelength of the target design frequency, the bent structure changes the feeding position, and the specific size is optimized and determined by electromagnetic simulation software HFSS.

[0046] Preferably, the total length of the left-hand circularly polarized monopole antenna is approximately 1 / 4 of the medium wavelength of the target design frequency, and the specific size is optimized and determined by electromagnetic simulation software HFSS.

[0047] The working principle of the present invention is as follows: the drain pad 91 of the field effect tube, the gate pad 92, and the two anode pads 93 of the switching diode are connected to the external power supply, the rectangular gap outside the pads realizes the isolation between different voltages, and the different power supply voltages are respectively transmitted to the field effect tube 2 and the switching diode 6 through the metallized through hole 94 for power supply, and the metal ground plate 10 is connected to the ground potential of the external power supply. The external voltage makes the field effect tube 2 at a suitable static working point, providing a certain gain to compensate the loss of the antenna. Controlling the switch diode 6 to be turned on or off can achieve different polarization states: when only one switch diode 6 connected to the left-hand circular polarization monopole antenna 8 is turned on, the entire structure presents a left-hand circular polarization characteristic, at which time the semi-ring microstrip antenna 5 mainly serves as a feedback path in the oscillator, and the left-hand circular polarization monopole antenna 8 serves as the main radiator; when only one switch diode 6 connected to the right-hand circular polarization monopole antenna 7 is turned on, the entire structure presents a right-hand circular polarization characteristic, at which time the semi-ring microstrip antenna 5 mainly serves as a feedback path in the oscillator, and the right-hand circular polarization monopole antenna 7 serves as the main radiator; when both switch diodes 6 are turned off, the entire structure presents a linear polarization characteristic, at which time the semi-ring microstrip antenna 5 serves as both a feedback path in the oscillator and a radiator to radiate oscillation signals outward. The right-hand circular polarization monopole antenna 7 and the left-hand circular polarization monopole antenna 8 respectively realize the rotation of the total current over time through the inverted L-shaped branch 82 and the bent antenna structure, and form right-hand and left-hand circular polarizations respectively according to different rotation directions. The dimensions of each part are optimized to achieve an overall loop gain magnitude equal to 1 and a phase that is an integer multiple of 360° to meet the oscillation conditions.

[0048] Example

[0049] As an embodiment, a polarization reconfigurable self-oscillating active antenna operating at 4.6 GHz is designed in the present invention.

[0050] Figure 3 is a schematic diagram of the dimensions of the top structure of an embodiment of the present invention, Figure 4 It is a schematic diagram of the dimensions of the underlying structure of an embodiment of the present invention.

[0051] like Figure 3 As shown, the dielectric substrate 1 has a length of l1 = 39 mm and a width of w1 = 39 mm. The metal grounding plate 10 is close to the upper left corner of the dielectric substrate 1 and has a length of l g =23mm, width w g =23mm, the center of the field effect tube 2 is laterally offset by x2=14.8mm from the lower left corner of the metal ground plate 10, and is longitudinally offset by y2=8.2mm.

[0052] The width of the microstrip line 3 is w3 = 1 mm, and the length of the first transmission line 31 is l 31 =1.2mm, the second transmission line 32 is l 32 =1.9mm, the third transmission line 33 is l 33 =1.9mm, the gap width d4 between the transmission lines for welding the capacitor 4 is 0.6mm, and the capacitance of the capacitor 4 is 120pF. The gap width d6 between the output end of the microstrip line 3 and the right-handed circularly polarized monopole antenna 7 and the left-handed circularly polarized monopole antenna 8 for welding the switching diode 6 is 1.2mm.

[0053] The semi-ring microstrip antenna 5 has the center of the field effect tube 2 as the center, with an inner radius r5 = 3.5 mm and a ring width w5 = 0.5 mm.

[0054] The right-hand circularly polarized monopole antenna 7 is bent upward from the connection with the switching diode 6 by a length l 71 =1mm, right bending length l 73 =4mm, width is w 71 =1mm, downward extension length l 72 =15mm, width is w 72 =0.5mm.

[0055] The monopole branch 81 in the left-hand circularly polarized monopole antenna 8 extends downward from the connection with the switching diode 6 by a length of l 81 =13.5mm, width is w 81 = 1 mm. The inverted L-shaped branch 82 is laterally offset from the lower left corner of the metal ground plate 10 by x 82 =17.5mm, downward extension length l i1 =8.6mm, rightward extension length l i2 =6mm, width is w 82 =0.6mm.

[0056] In the DC bias circuit 9, the drain pad 91, gate pad 92, two switch diode anode pads 93 and the source pad 95 of the field effect tube on the front side have the same size, the side length of the square pad is p = 1.2mm; the peripheral gap width of the back pad is c = 0.15mm; the diameter of the metallized through hole 94 is b = 0.4mm; the input end of the choke line 96 is a square with a side length of a = 1mm, connected to a total length of l 96 =10mm, width w 96 = 0.2mm narrow line. The choke line 96 is bent according to the size of the dielectric plate, and the DC connection can be guaranteed under the premise of ensuring the connection relationship. The specific position of the connection point does not affect the performance.

[0057] The drain pad 91 and the gate pad 92 of the field effect tube are respectively connected to the external voltage V D =1.6V, V G =-0.4V to power the field effect tube 4. When only the anode pad 93 of the switch diode on one side of the left-hand circular polarization monopole antenna 8 is connected to the external voltage V on =0.9V, the diode is turned on, and the left-hand circularly polarized monopole antenna 8 is connected to other structures by radio frequency. The directional diagram simulated in the electromagnetic simulation software HFSS is as follows Figure 5 As shown, in the two planes of phi = 0° and phi = 90°, the left-hand circular polarization component (LHCP) is higher than the right-hand circular polarization component (RHCP) near theta = 0°, showing a left-hand circular polarization characteristic; when only the anode pad 93 of the switch diode on one side of the right-hand circular polarization monopole antenna 7 is connected to the external voltage V on =0.9V, the diode is turned on, and the right-hand circularly polarized monopole antenna 7 is connected to other structures by radio frequency. The directional pattern simulated in the electromagnetic simulation software HFSS is as follows Figure 6 As shown, in the two planes of phi = 0° and phi = 90°, the right-hand circular polarization component (RHCP) is higher than the left-hand circular polarization component (LHCP) near theta = 0°, showing a right-hand circular polarization characteristic; when the anode pads 93 of the two switching diodes are not connected to the external voltage, the diodes are cut off, the left-hand circular polarization monopole antenna 8 and the right-hand circular polarization monopole antenna 7 are disconnected from other structures, and the directional diagram simulated in the electromagnetic simulation software HFSS is as follows: Figure 7 As shown, it exhibits linear polarization characteristics.

[0058] Figures 8 to 10 It is a test spectrum diagram of the structural oscillation signal of the present invention. Figure 8 is the spectrum of the output signal in the left-hand circular polarization state in the embodiment of the present invention, showing that the oscillation frequency is 4.68 GHz; Fig. 9 is the output signal spectrum in the right-hand circular polarization state in the embodiment of the present invention, showing that the oscillation frequency is 4.58 GHz; Fig.10It is the output signal spectrum of the embodiment of the present invention under the linear circular polarization state, showing that the oscillation frequency is 3.7GHz; the test results show that the embodiment of the present invention successfully oscillates under three states, and the oscillation frequency in the linear polarization state deviates far from the design target, which can be optimized by adjusting the size. Figures 11-12 They are the axial ratio test results of the left-hand circularly polarized and right-hand circularly polarized antennas in the embodiments of the present invention. In the two planes of phi=0° and phi=90°, the axial ratio near the main radiation direction (theta=0°) is less than 3dB, achieving circular polarization performance.

Claims

1. A polarization reconfigurable self-oscillating active antenna, characterized in that: It comprises a dielectric substrate (1), a field effect transistor (2), two microstrip lines (3), a capacitor (4), a semi-ring microstrip antenna (5), a switching diode (6), a right-hand circularly polarized monopole antenna (7), a left-hand circularly polarized monopole antenna (8), a DC bias circuit (9), and a metal grounding plate (10); The two sources of the field effect tube (2) are respectively connected to the two output ends of the DC bias circuit (9) in a one-to-one correspondence, and the gate and drain are respectively connected to the input end of a microstrip line (3); the cathodes of the two switching diodes (6) are respectively connected to the other two output ends of the DC bias circuit (9); the two third transmission lines (33) are respectively vertically connected to the last two output ends of the DC bias circuit (9), and are respectively connected to the right-hand circularly polarized monopole antenna (7) and the left-hand circularly polarized monopole antenna (8); each microstrip line (3) comprises a first transmission line (31), a second transmission line (32), and a third transmission line (33) which are connected in sequence, and the first transmission line (31) and the second transmission line (32) and the second transmission line (32) and the third transmission line (33) are connected via a capacitor (4); the gate and drain are respectively connected to the two first transmission lines (31); ), the output end of the third transmission line (33) of each microstrip line (3) is respectively connected to the anode of a switching diode (6); the two ends of the semi-ring microstrip antenna (5) are respectively connected to the two second transmission lines (32) in a one-to-one correspondence, and the two third transmission lines (33) are respectively vertically connected to the last two output ends of the DC bias circuit (9); The DC bias circuit (9) comprises a field effect transistor drain pad (91), a gate pad (92), two switch diode anode pads (93) arranged on the back of the dielectric substrate (1), eight metallized through holes (94) penetrating the dielectric substrate (1), two source pads (95) arranged on the front of the dielectric substrate (1), and six choke lines (96); The field effect tube drain pad (91), the gate pad (92), and the two switch diode anode pads (93) on the back side of the dielectric substrate (1) are all etched with rectangular gaps on the periphery for isolating the DC voltage. The metallized through-holes (94) at the center are respectively connected to the input ends of the four choke lines (96) on the front side of the dielectric substrate (1), and the positions are symmetrical and the sizes are the same. The other ends of the choke lines (96) are respectively connected to the two first transmission lines (31) and the two third transmission lines (33). The two choke lines (96) connected to the third transmission lines (33) are bent to reduce the area. The input ends of the other two choke lines (96) are each provided with a metallized through-hole (94) at the center. The output ends are respectively connected to the cathodes of the two switch diodes (6) and are bent. The two source pads (95) on the front side of the dielectric substrate (1) are respectively connected to the two source electrodes of the field effect tube (2), and each has a metallized through-hole (94) at the center. The left-hand circularly polarized monopole antenna (8) comprises a monopole branch (81) disposed on the front side of the dielectric substrate (1) and an inverted L-shaped branch (82) disposed on the back side of the dielectric substrate (1); The left-handed circularly polarized monopole branch (81) is connected to the cathode of a switching diode (6) and is also vertically connected to a bent choke line (96). The inverted L-shaped branch (82) is connected to a metal grounding plate (10).

2. The polarization reconfigurable self-oscillating active antenna according to claim 1, characterized in that: The two microstrip lines (3) and the four capacitors (4) are symmetrically structured with the two source connection lines of the field effect tube (2) as axes, the input ends of the two first transmission lines (31) are respectively connected to the gate and drain of the field effect tube (2), and the output ends of the two third transmission lines (33) are respectively connected to the anodes of the two switch diodes (6) in a one-to-one correspondence.

3. The polarization reconfigurable self-oscillating active antenna according to claim 1, characterized in that: The length of the choke line (96) is 1 / 4 of the medium wavelength corresponding to the target design frequency.

4. The polarization reconfigurable self-oscillating active antenna according to claim 1, characterized in that: The right-hand circularly polarized monopole antenna (7) has a bent structure, and its total length is 1 / 4 of the medium wavelength of the target design frequency.

5. The polarization reconfigurable self-oscillating active antenna according to claim 1, characterized in that: The total length of the left-hand circularly polarized monopole antenna (8) is 1 / 4 of the medium wavelength corresponding to the target design frequency.

6. The polarization reconfigurable self-oscillating active antenna according to claim 1, characterized in that: Satisfy the oscillation conditions: ， in, G BJT is the transistor voltage gain, L ANT is the antenna loss, w 0 is the oscillation angular frequency.

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