A bandpass filtering phased electromagnetic surface unit with adjustable passband

Abstract

The present invention discloses a bandpass filtering phase-controlled electromagnetic surface unit with adjustable passband, comprising an excitation phase-shifting unit, a PIN diode, a second PIN diode, a varactor diode, a zero-order resonance unit and a short-circuit branch, wherein the excitation phase-shifting unit, the zero-order resonance unit and the short-circuit branch are connected to the ground above the second dielectric layer through a metal via in a first dielectric layer, and the excitation phase-shifting unit realizes a 180° phase difference by switching on and off the first PIN diode and the second PIN diode. The present invention enables the bandpass filtering phase-controlled electromagnetic surface unit to switch between stealth and communication functions without increasing the dielectric layer thickness of the original excitation unit, and can better balance the relationship between the profile of the phase-controlled electromagnetic surface, the working bandwidth and the radiation efficiency.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic waves, and in particular to a bandpass filtering phase-controlled electromagnetic surface unit with adjustable passband. Background Art

[0002] Traditional FSS with spatial filtering characteristics is usually used in radomes to improve the anti-interference and stealth performance of antenna systems. However, FSS cannot effectively suppress out-of-band electromagnetic interference and cannot flexibly switch between stealth and communication functions. Therefore, reconfigurable electromagnetic surfaces with filtering characteristics have attracted the attention of researchers at home and abroad. By integrating controllable components or tunable materials in electromagnetic units, the electromagnetic characteristics of electromagnetic surface units can be electrically adjusted. Among them, the performance, maturity, availability, integration, bias complexity, etc. of controllable components and tunable materials are crucial to the research on reconfigurable electromagnetic surfaces.

[0003] Compared with reconfigurable transmission arrays, the research on reconfigurable transmission arrays with bandpass filtering characteristics has just started, and the unit design process is difficult. Not only does it need to consider the transmission unit amplitude and transmission phase coverage, but also the unit's sensitivity to frequency changes, narrow bandwidth and out-of-band suppression, etc. The reconfigurable transmission array also faces problems such as poor scanning performance at large angles and large unit losses. Therefore, it is of great significance to study the key technologies between the working bandwidth, unit profile, radiation efficiency and out-of-band suppression of the reconfigurable transmission electromagnetic surface unit. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a bandpass filtering phased electromagnetic surface unit with adjustable passband, which can enable the bandpass filtering phased electromagnetic surface unit to switch between stealth and communication functions without increasing the thickness of the dielectric layer of the original excitation unit, and better balance the relationship between the profile of the phased electromagnetic surface, the working bandwidth and the radiation efficiency.

[0005] The objective of the present invention is achieved through the following technical scheme: a bandpass filtering phase-controlled electromagnetic surface unit with adjustable passband, comprising an excitation phase shifting unit, a first PIN diode, a second PIN diode, a varactor diode, a zero-order resonance unit and a short-circuit branch, wherein the excitation phase shifting unit, the zero-order resonance unit and the short-circuit branch are connected to the ground on the dielectric layer through metal vias in the dielectric layer, and the excitation phase shifting unit realizes a 180° phase difference by turning on and off the first PIN diode and the second PIN diode.

[0006] The beneficial effects of the present invention are as follows: the present invention enables the bandpass filtering phased electromagnetic surface unit to switch between stealth and communication functions without increasing the dielectric layer thickness of the original excitation unit, and better balances the relationship between the phased electromagnetic surface profile, working bandwidth and radiation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is the 8th order high pass Butterworth filter circuit diagram;

[0008] Figure 2 It is the circuit diagram of the composite left-handed and right-handed transmission line unit;

[0009] Figure 3 is a filter circuit diagram with high-pass filter characteristics;

[0010] Figure 4 It is the schematic diagram of a 1-bit phased electromagnetic surface unit with high-pass filtering characteristics;

[0011] Figure 5 It is the principle diagram of the bandpass filtering phased electromagnetic surface unit;

[0012] Figure 6 The schematic diagram of the bandpass filtering phased electromagnetic surface unit with adjustable passband;

[0013] Figure 7 This is a comparison of the directivity diagrams of the phased electromagnetic surface unit before and after the introduction of the transmission zero point;

[0014] Figure 8 It is a curve diagram of the gain G of the bandpass filter phased electromagnetic surface unit changing with the frequency f;

[0015] Fig. 9 A side view of a bandpass filtering phased electromagnetic surface unit with adjustable passband;

[0016] Fig.10 A top view of a bandpass filtering phased electromagnetic surface unit with adjustable passband;

[0017] Fig.11 The diode bias circuit diagram in the bandpass filter phase-controlled electromagnetic surface unit with adjustable passband;

[0018] Fig.12 The structural diagram of the connection between the passband adjustable bandpass filtering phased electromagnetic surface unit and the microstrip power division network in the phased electromagnetic surface;

[0019] In the figure, 1-first dielectric layer, 2-second dielectric layer, 3-fourth dielectric layer, 4-fourth metal via, 5-first metal via, 6.1-first zero-order resonant unit, 6.2-second zero-order resonant unit, 7.1-first excitation phase shift unit, 7.2-second excitation phase shift unit, 8-feeding point, 9-short-circuit branch, 10-first PIN diode, 11.1-first varactor diode, 11.2-second varactor diode, 12-bias circuit, 13-metal microstrip line, 14-second PIN diode, 15-third dielectric layer, 16-fifth dielectric layer, 17-first ground layer, 18-second ground layer, 19-third ground layer, 20-second metal via, 21-third metal via. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0021] The present invention takes the traditional high-order Butterworth low-pass filter circuit as the starting point, explores the working principle of the broadband filter circuit, and selects a 1-bit magnetic dipole phase shift unit as the excitation source. The E-plane radiation pattern of this phase shift unit is wider than the H-plane radiation pattern, which can improve the large-angle scanning loss of the reconfigurable transmission electromagnetic surface array. By symmetrically placing the linearly polarized mushroom-shaped electromagnetic bandgap structure (EBG) on both sides of the magnetic dipole unit, a resonant zero point is introduced to expand the working bandwidth of the transmission electromagnetic surface unit. At the same time, a transmission zero point is introduced at the low frequency point of 15.5GHz in the working frequency band, so that the reconfigurable transmission electromagnetic surface unit has high-pass filtering characteristics; in order to achieve high-frequency operation in the working frequency band, the resonant zero point is introduced at the low frequency point of 15.5GHz in the working frequency band. A transmission zero is also introduced at the frequency point, and a 0.25λ short-circuit patch is symmetrically placed in the polarization parallel direction of the 1-bit phase shifter unit. At this time, the reconfigurable transmission unit has a bandpass filtering characteristic. A variable capacitance diode Cv is placed in the phase shifter unit and the EBG unit structure. The unit passband bandwidth can be adjusted by adjusting the value of Cv, so that the bandpass filtering phased electromagnetic surface unit can be switched between stealth and communication functions, and the passband bandwidth can be adjusted. At the same time, the thickness of the dielectric layer of the original excitation unit is not increased, and the relationship between the profile of the phased electromagnetic surface, the working bandwidth and the radiation efficiency is well balanced, laying a foundation for subsequent research on integrated electromagnetic surface arrays applied to small aircraft.

[0022] The traditional high-pass filter network can increase the out-of-band rejection ratio of the filter circuit through a series resonant resonant circuit, such as Figure 1 The figure shows the schematic diagram of the 8th-order high-pass Butterworth filter circuit; based on the working principle of high-order high-pass filtering, by analyzing the following Figure 2It is found in the composite right-handed transmission line (CRLH TL) circuit diagram shown that, as long as reasonable excitation is applied, using the CRLH TL unit as a load can not only expand the working bandwidth of the excitation, but also obtain an electromagnetic surface unit with high-pass filtering characteristics.

[0023] If the phased electromagnetic surface is to achieve broadband conformality, the unit thickness should not increase with the increase of bandwidth. Figure 2 The unit circuit is designed in parallel with the excitation source. Figure 3 (a) shows a filter circuit with high-pass characteristics. Figure 3 (b) is the curve of the S parameter of the high-pass filter circuit changing with frequency. Figure 3 (b) It can be seen that a resonance zero point with a resonance frequency of f1 = 16.5 GHz is introduced near the source with a resonance frequency of f0 = 16.8 GHz, which extends the source working bandwidth and has a high-pass filtering characteristic.

[0024] according to Figure 3 The simulated circuit model is used to model the electromagnetic surface unit design. Figure 4 As shown in (a), a 1-bit magnetic dipole phase shift unit is used as the excitation source, the resonance frequency f0 = 16.4 GHz, the resonance frequency f1 = 15.9 GHz of the zero-order resonance unit, and a transmission zero point is introduced at the low frequency point 15.7 GHz of the transmission curve S21, so that the electromagnetic surface unit has a high-pass filtering characteristic. Figure 4 b is Figure 4 The amplitude response of a unit, in addition, by controlling the magnetic dipole two PIN diode switch states as Figure 4 (c) and Figure 4 As shown in (d), the two state currents of the magnetic dipole are deflected 180°, forming a 1-bit phase-controlled electromagnetic surface unit.

[0025] In order to introduce a transmission zero at the high frequency point of the working frequency band, a quarter-wavelength short-circuit branch is symmetrically placed in the direction parallel to the polarization of the 1-bit phase shift unit. Figure 5 It can be seen that a transmission zero point fr2 is introduced at the frequency of 17.5 GHz, so that the high-pass filtering phased electromagnetic surface unit has a band-pass filtering characteristic. Figure 5 (a) is a phased electromagnetic surface unit with bandpass filtering characteristics. Figure 5 (b) Yes Figure 5 (a) Magnitude response of the unit, Figure 5 (d) Yes Figure 5 (a) The phase response of the unit; given by Figure 5 (c) It can be seen that at the frequency point fr2 = 17.5 GHz, the short-circuit branch and Figure 4 The current directions of the phased electromagnetic surface units with high-pass filtering characteristics are opposite.

[0026] Depend on Figure 3 It can be seen from the filter circuit with high-pass filter characteristics that when the capacitance value of the series resonant capacitor C1 is changed, the Figure 2 The resonance point f1 of the series resonant circuit in Figure 5 A variable capacitor Cv is connected in parallel between the zero-order resonance unit and the phase shift unit, such as Figure 6 (a) As shown; by controlling the bias voltage of the variable capacitor and adjusting the value of Cv, the bandwidth BW of the passband can be changed as shown in Figure 6 As shown in (b), when the Cv value increases from 10fF to 20fF, fr1 shifts from 15.7GHz to 15GHz, and the bandwidth in the passband becomes wider.

[0027] In order to explore whether loading the transmission zero point only expands the bandwidth of the phase-shifting unit and does not affect the radiation characteristics of the phase-shifting unit, the changes in the radiation pattern of the phase-controlled electromagnetic surface unit before and after the introduction of the transmission zero point are simulated. Figure 7 shown. Figure 7 The red line is the E-plane radiation pattern, the blue line is the H-plane radiation pattern, the solid line is the unit radiation pattern after the transmission zero point is introduced, and the short line is before the transmission zero point is introduced. Figure 7 It can be seen that except for the smaller rear lobe of the phased electromagnetic surface unit after the introduction of the transmission zero point, the main lobe pattern of the unit basically remains unchanged.

[0028] when Figure 6 When the varactor diode Cv=10fF, the gain G of the bandpass filter phase-controlled electromagnetic surface unit with adjustable passband changes with frequency f as shown in the figure below: Figure 8 As shown by Figure 8 It can be seen that there are radiation zero points outside the passband at the low frequency fz1=15.9GHz and the high frequency fz2=17.4GHz.

[0029] like Figures 9 to 12 As shown, the bandpass filter phased electromagnetic surface unit with adjustable passband of the present application is symmetrical about the x-axis and the y-axis, and includes a metal surface, a first dielectric layer 1, a first grounding layer 17, a second dielectric layer 2, a bias circuit layer, a third dielectric layer 15, a second grounding layer 18, a fourth dielectric layer 3, a microstrip feeder layer, a fifth dielectric layer 16 and a third grounding layer 19 arranged in sequence from top to bottom;

[0030] The metal surface comprises a first zero-order resonance unit 6.1, a first excitation phase shift unit 7.1, a second excitation phase shift unit 7.2 and a second zero-order resonance unit 6.2 arranged in sequence from front to back, a feeding point 8 is arranged between the first excitation phase shift unit 7.1 and the second excitation phase shift unit 7.2, the feeding point 8 is connected to the first excitation phase shift unit 7.1 through a first PIN diode 10, the feeding point 8 is connected to the second excitation phase shift unit 7.2 through a second PIN diode 14, the first excitation phase shift unit 7.1 is connected to the first zero-order resonance unit 6.1 through a first variable capacitance diode 11.1; the second excitation phase shift unit 7.2 is connected to the second zero-order resonance unit 6.2 through a second variable capacitance diode 11.2; a short-circuit branch 9 is arranged on both sides of the first excitation phase shift unit 7.1 and the second excitation phase shift unit 7.2;

[0031] The bandpass filtering phased electromagnetic surface unit further includes a second metal via 20, one end of which is connected to the feeding point 8 of the metal surface, and the other end of which sequentially passes through the first dielectric layer 1, the first ground layer 17, the second dielectric layer 2, the bias circuit layer, the third dielectric layer 15, the second ground layer 18, the fourth dielectric layer 3 and is connected to the microstrip feeder layer;

[0032] The bandpass filter phased electromagnetic surface unit also includes a plurality of first metal vias 5, each of which sequentially penetrates the first ground layer 17, the second dielectric layer 2, the bias circuit layer, the third dielectric layer 15, the second ground layer 18, the fourth dielectric layer 3, the microstrip feed line layer, the fifth dielectric layer 16 and the third ground layer 19 to achieve connection between the three layers and simulate coaxial feeding with the second metal via 20;

[0033] The bandpass filter phased electromagnetic surface unit further includes a plurality of third metal vias 21, one end of each third metal via 21 is connected to the short-circuit branch 9, the first zero-order resonant unit 6.1 or the second zero-order resonant unit 6.2 in the metal surface, and the other end penetrates the first dielectric layer 1 and is connected to the first ground layer 17;

[0034] The first excitation phase shift unit 7 . 1 and the second excitation phase shift unit 7 . 2 achieve a phase difference of 180° by switching the first PIN diode 10 and the second PIN diode 14 on and off.

[0035] The first zero-order resonant unit 6.1, the first excitation phase shift unit 7.1, the second excitation phase shift unit 7.2, the second zero-order resonant unit 6.2 and the short-circuit branch 9 are all metal patches. The first zero-order resonant unit 6.1, the first excitation phase shift unit 7.1, the second excitation phase shift unit 7.2, the second zero-order resonant unit 6.2 and the short-circuit branch 9 are connected to the first grounding layer 17 through metal through holes to realize their functions.

[0036] In some embodiments, the number of the third metal vias 21 is 6, wherein each of the four third metal vias 21 corresponds to a short-circuit branch 9, and is used to connect the corresponding short-circuit branch to the first ground layer 17;

[0037] Of the remaining two third metal vias 21 , one third metal via 21 is connected to the first zero-order resonant unit 6 . 1 , and the other third metal via 21 is connected to the second zero-order resonant unit 6 . 2 .

[0038] In some other embodiments, the number of the third metal vias 21 may be greater than 6, and the first zero-order resonant unit 6.1, the second zero-order resonant unit 6.2 and each short-circuit branch may be connected to the first ground layer 17 through one or more third metal vias 21;

[0039] In the embodiment of the present application, the first grounding layer 17 , the second grounding layer 18 and the third grounding layer 19 are all grounding metal layers.

[0040] The bias circuit layer includes a fan-shaped metal patch and a serpentine metal line connected to the fan-shaped metal patch. The serpentine metal line is connected to the feeding point 8 through a fourth metal via 4. The on and off of the first PIN diode 10 and the second PIN diode 14 are controlled by feeding through the bias circuit layer.

[0041] The microstrip feed line layer includes a metal microstrip line, one end of which is connected to the feeding point 8 through a second metal via 20, and the other end of which is used for feeding.

[0042] In the embodiment of the present application, the excitation phase shifting unit (the first excitation phase shifting unit 7.1 and the second excitation phase shifting unit 7.2) realizes a 180° phase difference by switching on and off the PIN diodes (the first PIN diode 10 and the second PIN diode 14), such as Figure 4 As shown, when the first PIN diode 10 and the second PIN diode 14 are in the Onoff state, the current vector direction diagram of the unit is as follows: Figure 4 (c) Along the positive direction of the x-axis, the corresponding phase response curve is as follows Figure 4 Green curve in (e); when the first PIN diode 10 and the second PIN diode 14 are in the Off-state, the current vector direction diagram of the unit is as follows: Figure 4 (d) Along the negative direction of the x-axis, the corresponding phase response curve is as follows Figure 4(e) Red curve; The Onoff / Offon state of the first PIN diode 10 and the second PIN diode 14 is controlled by the bias circuit 12 through the fourth metal via 4, which is composed of a fan-shaped metal patch and a serpentine metal line. The metal microstrip line 13 is connected to the feeding point 8 through the second metal via 20 to realize the coupling feeding of the 1-bit phase shift unit (the 1-bit phase shift unit is composed of the first PIN diode 10 and the second PIN diode 14, the first excitation phase shift unit 7.1, the second excitation phase shift unit 7.2, the first ground layer 17 and the fourth metal via 4). The metal microstrip line is also connected to an external strip power division network for feeding. Figure 6 As shown, the passband bandwidth of the bandpass filtering phase-controlled electromagnetic surface unit can be adjusted by changing the value of the variable capacitor Cv (the first varactor diode and the second varactor diode).

[0043] The passband-adjustable bandpass filtering phased electromagnetic surface unit designed by the patent of the present invention takes the multi-layer cascaded high-order filtering circuit as the starting point. On the basis of not increasing the thickness of the excitation unit, by analyzing the working mechanism of the high-order high-pass filtering circuit and the zero-order resonance unit, the ZOR unit is loaded with 180° magnetic dipole phase shifting unit at both ends, the impedance matching bandwidth is extended, and a transmission zero point is introduced at the low frequency point of the working frequency band, so that the 1-bit broadband conformal electromagnetic surface unit has high-pass filtering characteristics; a quarter-wavelength short-circuit branch is symmetrically placed in the parallel direction of the polarization of the phase shifting unit, and a transmission zero point is introduced at the high frequency point to form a bandpass filtering phased electromagnetic surface unit, and a variable capacitor Cv is placed between the ZOR unit and the phase shifting unit, and the passband bandwidth can be controlled by adjusting the capacitor bias voltage. The radiation pattern of the bandpass filtered phased electromagnetic surface unit was simulated and analyzed. The introduction of the radiation zero-point unit does not affect the radiation characteristics of the original phase-shifting unit (the lobe width of the E-plane pattern is larger than that of the H-plane pattern). A good balance was achieved between the broadband characteristics, unit profile and radiation characteristics, laying the foundation for subsequent research on conformal phased electromagnetic surfaces for small aircraft.

Claims

1. A bandpass filtering phased electromagnetic surface unit with adjustable passband, characterized in that: It comprises, arranged in order from top to bottom, a metal surface, a first dielectric layer (1), a first grounding layer (17), a second dielectric layer (2), a bias circuit layer, a third dielectric layer (15), a second grounding layer (18), a fourth dielectric layer (3), a microstrip feeder layer, a fifth dielectric layer (16) and a third grounding layer (19); The metal surface comprises a first zero-order resonance unit (6.1), a first excitation phase shift unit (7.1), a second excitation phase shift unit (7.2) and a second zero-order resonance unit (6.2) which are arranged in sequence from front to back; a feeding point (8) is arranged between the first excitation phase shift unit (7.1) and the second excitation phase shift unit (7.2); the feeding point (8) is connected to the first excitation phase shift unit (7.1) via a first PIN diode (10); the feeding point (8) is connected to the second excitation phase shift unit (7.2) via a second PIN diode (14); the first excitation phase shift unit (7.1) is connected to the first zero-order resonance unit (6.1) via a first variable capacitance diode (11.1); the second excitation phase shift unit (7.2) is connected to the second zero-order resonance unit (6.2) via a second variable capacitance diode (11.2); and a short-circuit branch (9) is arranged on both sides of the first excitation phase shift unit (7.1) and the second excitation phase shift unit (7.2); The bandpass filtering phased electromagnetic surface unit further comprises a second metal via (20), one end of the second metal via (20) being connected to a feeding point (8) on the metal surface, and the other end of the second metal via (20) sequentially passing through the first dielectric layer (1), the first ground layer (17), the second dielectric layer (2), the bias circuit layer, the third dielectric layer (15), the second ground layer (18), and the fourth dielectric layer (3) to be connected to the microstrip feeder layer; The bandpass filtering phased electromagnetic surface unit further comprises a plurality of first metal vias (5), each of the first metal vias (5) sequentially penetrating the first ground layer (17), the second dielectric layer (2), the bias circuit layer, the third dielectric layer (15), the second ground layer (18), the fourth dielectric layer (3), the microstrip feed line layer, the fifth dielectric layer (16) and the third ground layer (19), thereby achieving connection between the three layers and simulating coaxial feeding with the second metal via (20); The bandpass filtering phase-controlled electromagnetic surface unit further comprises a plurality of third metal vias (21), one end of each third metal via (21) being connected to a short-circuit branch (9), a first zero-order resonant unit (6.1) or a second zero-order resonant unit (6.2) in the metal surface, and the other end of each third metal via (21) penetrating the first dielectric layer (1) and connected to the first ground layer (17); The first excitation phase shift unit (7.1) and the second excitation phase shift unit (7.2) achieve a phase difference of 180° by switching on and off the first PIN diode (10) and the second PIN diode (14).

2. The bandpass filtering phased electromagnetic surface unit with adjustable passband according to claim 1, characterized in that: The metal surface is symmetrical up and down.

3. The bandpass filtering phased electromagnetic surface unit with adjustable passband according to claim 1, characterized in that: The metal surface is bilaterally symmetrical.

4. The bandpass filtering phased electromagnetic surface unit with adjustable passband according to claim 1, characterized in that: The first zero-order resonance unit (6.1), the first excitation phase shift unit (7.1), the second excitation phase shift unit (7.2), the second zero-order resonance unit (6.2) and the short-circuit branch (9) are all metal patches.

5. The bandpass filtering phased electromagnetic surface unit with adjustable passband according to claim 1, characterized in that: The number of the third metal vias (21) is 6, wherein four third metal vias (21) each correspond to a short-circuit branch (9), and are used to connect the corresponding short-circuit branch to the first ground layer (17); Of the remaining two third metal vias (21), one third metal via (21) is connected to the first zero-order resonance unit (6.1), and the other third metal via (21) is connected to the second zero-order resonance unit (6.2).

6. The bandpass filtering phased electromagnetic surface unit with adjustable passband according to claim 1, characterized in that: The first grounding layer (17), the second grounding layer (18) and the third grounding layer (19) are all grounding metal layers.

7. The bandpass filtering phased electromagnetic surface unit with adjustable passband according to claim 1, characterized in that: The bias circuit layer is provided with a bias circuit (12), the bias circuit (12) comprising a fan-shaped metal patch and a serpentine metal line connected to the fan-shaped metal patch, the serpentine metal line being connected to the feeding point (8) via a fourth metal via (4), and feeding through the bias circuit layer to control the on and off of the first PIN diode (10) and the second PIN diode (14).

8. The bandpass filtering phased electromagnetic surface unit with adjustable passband according to claim 1, characterized in that: The microstrip feed line layer comprises a metal microstrip line (13), one end of the metal microstrip line (13) being connected to the feed point (8) via a second metal via (20).

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