A frequency selective absorbing device with a controllable highly selective transparent wave window

Abstract

The present invention discloses a frequency selective absorbing device with a controllable high-selection and transparent wave window, which includes an absorption layer and a transmission layer. The absorption layer and the transmission layer are fixed by non-metal columns, thereby forming an air layer (1) between the absorption layer and the transmission layer. The absorption layer includes a first dielectric plate (3), a first metal layer (2) disposed on the upper surface of the first dielectric plate (3), and a second metal layer (4) disposed between the lower surface of the first dielectric plate (3) and the air layer (1). The transmission layer includes a third metal layer (5), a second dielectric plate (6), a fourth metal layer (7), a third dielectric plate (8), and a fifth metal layer (9) arranged in sequence from top to bottom. The third metal layer (5) is adjacent to the air layer (1) and is located below the air layer (1). For interference signals outside the broadband, the present invention realizes shielding in a fully absorbing manner. When an in-band interference signal is detected, by closing the wave-transparent window, the in-band interference signal can be fully absorbed, thereby avoiding the influence of the interference signal on the radio frequency receiver.

Description

Technical Field

[0001] The present invention belongs to the field of antennas and electromagnetic waves, and particularly relates to a frequency selective absorbing device with a controllable highly selective transparent wave window. Background Art

[0002] Modern radio frequency systems are developing towards the direction of integration and comprehensiveness. Single antennas have more and more transmitting or receiving frequency bands, which makes it easier for radio frequency receivers to receive interference signals in unknown frequency bands coupled by antennas. Therefore, the "front door" protection of receivers is crucial. Frequency selective surfaces can reflect out-of-band interference signals and ensure good transmission of in-band signals, so they can be used in the front door protection design of equipment. However, shielding incoming waves in the form of reflection may cause secondary emission of interference and become a new interference source. At the same time, since the in-band transmission state is maintained, there is no protection against possible in-band interference signals. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a frequency selective absorbing device with a controllable highly selective transparent wave window. For interference signals outside the broadband, shielding is achieved by means of full absorption. When in-band interference signals are detected, by closing the wave transmission window, in-band interference signals can be fully absorbed, thus avoiding the influence of interference signals on radio frequency receivers.

[0004] The purpose of the present invention is achieved through the following technical solutions: A frequency selective absorbing device with a controllable highly selective transparent wave window, comprising an absorption layer and a transmission layer. The absorption layer and the transmission layer are fixed by non-metallic columns, thereby forming an air layer between the absorption layer and the transmission layer;

[0005] The absorption layer includes a first dielectric plate, a first metal layer disposed on the upper surface of the first dielectric plate, and a second metal layer disposed between the lower surface of the first dielectric plate and the air layer;

[0006] The transmission layer includes a third metal layer, a second dielectric plate, a fourth metal layer, a third dielectric plate, and a fifth metal layer disposed in sequence from top to bottom. The third metal layer is adjacent to the air layer and is located below the air layer.

[0007] Wherein, the first metal layer includes two symmetric resonant units, namely a first resonant unit and a second resonant unit;

[0008] Each resonant unit includes a U-shaped metal strip, and a first resistor, a first inductor, and a second resistor are sequentially embedded along the U-shaped metal strip; one end of the first resistor is connected to a first capacitor through a first metal strip line, the other end of the first resistor is connected to a first PIN diode through a second metal strip line, and a third metal strip line is connected between the first capacitor and the first PIN diode;

[0009] A first choke coil is also connected to the second metal strip line, and a second choke coil is also connected to the third metal strip line.

[0010] The first inductor is a lumped inductor or a planar printed inductor; the first capacitor is a lumped capacitor or a planar printed capacitor.

[0011] The second metal layer includes two metal strip lines. The first metal strip line is respectively connected to the first choke coils of the first resonant unit and the second resonant unit through two symmetric first metal vias;

[0012] The second metal strip line is respectively connected to the second choke coils of the first resonant unit and the second resonant unit through two symmetric second metal vias.

[0013] The third metal layer and the fifth metal layer include the same resonant structure for generating the resonance required to construct a passband. The resonant structure includes a second PIN diode and a planar printed capacitor. One end of the second PIN diode is connected to the first end of the planar printed capacitor, and the other end of the second PIN diode is connected to the second end of the planar printed capacitor.

[0014] The fourth metal layer includes two parallel bias strip lines. The first bias strip line is respectively connected to the first ends of the planar printed capacitors in the third metal layer and the fifth metal layer through third metal vias penetrating the entire transmission layer; the second bias strip line is respectively connected to the second ends of the planar printed capacitors in the third metal layer and the fifth metal layer through fourth metal vias penetrating the entire transmission layer.

[0015] The beneficial effects of the present invention are as follows: The present invention constructs an embedded resonator through lumped devices, realizes embedding a passband into a wide absorption band or a reflection band, adopts planar printed devices, and independently replaces the lumped devices, which can achieve the purpose of reducing the number of loaded lumped devices. Finally, the devices loaded on the surface of the structure are lumped resistors, PIN diodes, and choke coils, and there are no longer coupling capacitors and inductors for generating resonance, which can reduce the cost to a certain extent and improve the reliability of the structure. The embedded resonator can be used for flexible design of the passband. By independently adjusting the embedded capacitor or inductor, flexible design of the passband position and bandwidth can be realized to meet the application requirements of different frequencies and bandwidths in different scenarios. By integrating a PIN diode in the embedded resonant loop, dynamic regulation of the passband can be realized, and the passband can be dynamically switched according to the requirements of the application scenario to achieve more flexible front-door protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the present invention;

[0017] Figure 2 is a schematic structural diagram of the first metal layer based on a lumped inductor and a lumped capacitor;

[0018] Figure 3 Schematic diagram of the first metal layer structure based on planar printed inductors and planar printed capacitors;

[0019] Figure 4 Schematic diagram of the structure of the second metal layer

[0020] Figure 5 Schematic diagram of the passband regulation result of the absorption layer based on embedded resonators;

[0021] Figure 6 Schematic diagram of the structures of the third metal layer and the fifth metal layer;

[0022] Figure 7 Schematic diagram of the structure of the diode unit;

[0023] Figure 8 Schematic diagram of the S-parameter simulation result of the frequency selective absorber with a controllable high-selectivity transmission window;

[0024] Figure 9 Absorption rate simulation result of the frequency selective absorber with a controllable high-selectivity transmission window;

[0025] In the figure, 1 - air layer, 2 - first metal layer, 3 - first dielectric plate, 4 - second metal layer, 5 - third metal layer, 6 - second dielectric plate, 7 - fourth metal layer, 8 - third dielectric plate, 9 - fifth metal layer, 10 - second PIN diode, 11 - first vertical metal strip line, 12 - second vertical metal strip line, 13 - first vertical metal strip line, 14 - diode unit. Detailed implementation manners

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0027] The frequency selective absorber with a controllable high-selectivity transmission window proposed by the present invention is composed of three layers: an absorption layer, an air layer, and a transmission layer. The electromagnetic working state of the frequency selective absorption state is regulated by controlling the bias voltages on the absorption layer and the transmission layer.

[0028] By controlling the bias voltages, when the PIN diode loaded on the absorption layer is turned on and the PIN diode loaded on the transmission layer is turned off, the frequency selective absorber exhibits a state of high-selectivity transmission within the working band and absorption outside the band. Absorption bands exist at both ends of the transmission band (passband), and the transmission band is defined as the transmission window. The transmission band has a good steep drop outside the band, rolling off to the absorption band outside the narrow passband, and has good frequency selection characteristics.

[0029] Control the bias voltage. When the PIN diode on the absorption layer is cutoff and the PIN diode on the transmission layer is conducting, the frequency selective absorbing device presents an all-band absorbing state. At this time, the device no longer has an intermediate transmission band, so the transmission window is closed.

[0030] As Figure 1 shown, a frequency selective absorbing device with a controllable high-selective transmission window includes an absorption layer and a transmission layer. The absorption layer and the transmission layer are fixed by non-metal columns, so as to form an air layer 1 between the absorption layer and the transmission layer;

[0031] The absorption layer includes a first dielectric plate 3, a first metal layer 2 disposed on the upper surface of the first dielectric plate 3, and a second metal layer 4 disposed between the lower surface of the first dielectric plate 3 and the air layer 1;

[0032] The transmission layer includes a third metal layer 5, a second dielectric plate 6, a fourth metal layer 7, a third dielectric plate 8, and a fifth metal layer 9 arranged in sequence from top to bottom. The third metal layer 5 is adjacent to the air layer 1 and is located below the air layer 1.

[0033] In the embodiments of the present application; wherein, PIN diodes are loaded on the surfaces of both the absorption layer and the transmission layer to control the opening and closing of the transmission window. For the absorption layer, when the PIN diode is turned on, the passband is opened and the out-of-band presents an absorption state; for the transmission layer, when the PIN is turned off, the passband is opened and the out-of-band presents a reflection state, providing an equivalent metal floor for the absorption layer.

[0034] The absorption layer unit is composed of metal patterns printed on both sides of a dielectric substrate, that is, the first metal layer and the second metal layer. It is printed on both sides of an F4B dielectric substrate (the first dielectric layer) with a dielectric constant of 3. Among them, the first metal layer prints a periodic unit structure that generates passband and absorption band resonances. The second metal layer uses parallel metal lines to provide bias for the PIN diodes loaded on the first metal layer and is connected to the first metal layer through metal vias. Specifically:

[0035] As Figures 2 - 3 shown, the first metal layer 2 includes two symmetric resonant units, namely the first resonant unit and the second resonant unit;

[0036] Each resonant unit includes a U-shaped metal strip 2.1, and a first resistor 2.2, a first inductor 2.3, and a second resistor 2.4 are sequentially embedded along the U-shaped metal strip 2.1; one end of the first resistor 2.2 is connected to a first capacitor 2.5 through a first metal strip line, and the other end of the first resistor 2.2 is connected to a first PIN diode 2.7 through a second metal strip line. A third metal strip line is connected between the first capacitor 2.5 and the first PIN diode 2.7;

[0037] A first choke coil 2.8 is also connected to the second metal strip line, and a second choke coil 2.6 is also connected to the third metal strip line.

[0038] The first inductor 2.3 is a lumped inductor or a planar printed inductor; the first capacitor 2.5 is a lumped capacitor or a planar printed capacitor.

[0039] As Figure 4 shown, the second metal layer 4 includes two metal strip lines. The first metal strip line is respectively connected to the first choke coils 2.8 of the first resonant unit and the second resonant unit through two symmetric first metal vias 3.0

[0040] The second metal strip line is respectively connected to the second choke coils 2.6 of the first resonant unit and the second resonant unit through two symmetric second metal vias 2.9.

[0041] According to the frequency selective surface theory, a periodic metal strip array can be equivalent to a spatial band-stop filter. The first metal layer selects a metal strip unit with a folded end, and absorbs the resonant current excited by the incoming wave by loading a lumped resistor, so as to realize the loss of the incident wave. In order to insert a controllable transmission band into the absorbing band, the present invention proposes a design method of an embedded resonator. By connecting an embedded parallel resonator composed of an embedded inductor (the first inductor), an embedded capacitor (the first capacitor) and an RF switch PIN diode in series into a bent metal strip loaded with a lumped resistor. The PIN diode is used to control the on / off of the embedded resonator. When the PIN diode is off, the structure can be regarded as a metal strip unit loaded with a lumped resistor, and presents an absorption state for a wide frequency band; when the PIN diode is on, in the frequency band that satisfies the parallel resonance condition of the embedded inductor (the first inductor) and the embedded capacitor (the first capacitor), a pass band is generated, presenting the effect of out-of-band absorption and in-band transmission. The choke coil is used for AC-DC isolation and provides a bias voltage for the PIN diode.

[0042] Design process of the absorption layer:

[0043] 1. First, optimize the bent metal strip loaded with a lumped resistor to achieve broadband absorption.

[0044] 2. Further, perform an inlay design of the transmission window. As Figure 2 shown, use a lumped capacitor (the first capacitor), a lumped inductor (the first inductor) and the first PIN diode to build an embedded resonator, and the transmission frequency is determined by the lumped capacitor and the lumped inductor. The design method of the embedded resonator can be used for flexible design of the pass band width. By adjusting the equivalent values of the embedded capacitor (the first capacitor) or the inductor (the first inductor), flexible design of the pass band width and pass band position can be realized. As Figure 5As shown, when tuning the passband from 2.05 GHz to 2.35 GHz, if the embedded capacitance is reduced, the passband moves upward and the bandwidth increases (1 dB bandwidth: 4.3% - 5.4% - 7.7%); if the embedded inductance is reduced, the passband moves upward and the bandwidth decreases (1 dB bandwidth: 7.3% - 5.5% - 4.1%).

[0045] Planar printed devices can also be used to replace lumped embedded inductors and embedded capacitors. Among them, the meander line inductor is used to equivalent the embedded inductor, and the interdigital capacitor is used to equivalent the embedded capacitor. By adjusting the length or width of the meander line, the corresponding change of the inductor can be realized. By adjusting the depth or width of the interdigital structure of the interdigital capacitor, the corresponding change of the capacitor can be realized. Therefore, the design concept of the embedded resonator proposed by the present invention can be used for the flexible regulation design of the passband position and the passband width.

[0046] In order to achieve the high selectivity characteristic of the structural passband in this application, a frequency selective surface structure with a controllable high selectivity passband is proposed as the transmission layer. The structure is composed of three metal layers and two dielectric substrates laminated together. Among them, the middle metal layer is used to provide a bias voltage for the diode. The upper and lower metal layers have the same structure and are selected as a metal strip array with series-connected interdigital capacitors. The PIN diode is connected in parallel with the interdigital capacitor.

[0047] According to electromagnetic theory, when the polarization direction of the incident wave is consistent with the direction of the metal strip grating, the metal strip grating presents a total reflection state to the incident wave, while the design requirement of the transmission layer is to insert a controllable transmission band in the wide reflection band. Therefore, based on the idea of the embedded resonator, the planar printed capacitor connected in parallel with the PIN diode is inserted into the metal strip grating. When the PIN diode is turned on, the transmission layer can be equivalent to a metal strip array and presents a reflection state to the incoming wave. When the PIN is cut off, the planar printed capacitor and the strip grating inductor form a parallel resonator, thus realizing the insertion of a controllable passband in the reflection band.

[0048] In order to make the controllable passband have high selectivity characteristics, the upper and lower two metal structures (the third metal layer and the fifth metal layer) are adopted, and a second-order embedded resonator is constructed by the method of cascading through the intermediate dielectric layer. Therefore, the frequency selectivity of the passband is fully improved. Specifically:

[0049] As Figures 6 - 7 shown, the third metal layer 5 and the fifth metal layer 9 include the same resonant structure, which is used to generate the resonance required for constructing the passband. The resonant structure includes a first vertical metal strip line 11, and second vertical metal strip lines 12 and third vertical metal strip lines 13 that are symmetric to each other and located on both sides of the first vertical metal strip line 11;

[0050] The first vertical metal strip line 11 is provided with a first opening and a second opening from top to bottom, dividing the first vertical metal strip line 11 into an upper metal strip line, a middle metal strip line and a lower metal strip line; a diode unit 14 is arranged in each opening, and the diode unit 14 includes a second PIN diode 10 and a planar printed capacitor. One end of the second PIN diode 10 is connected to the first end of the planar printed capacitor, and the other end of the second PIN diode 10 is connected to the second end of the planar printed capacitor.

[0051] The first end of the planar printed capacitor in the first opening is further connected to the upper metal strip line, and the second end of the planar printed capacitor in the first opening is further connected to the middle metal strip line; the first end of the planar printed capacitor in the second opening is further connected to the middle metal strip line, and the second end of the planar printed capacitor in the second opening is further connected to the lower metal strip line.

[0052] The fourth metal layer 7 includes three parallel bias strip lines. The first bias strip line connects the upper metal strip lines in the third metal layer and the fifth metal layer together through a third metal via penetrating the entire transmission layer; the second bias strip line connects the middle metal strip lines in the third metal layer and the fifth metal layer together through a fourth metal via penetrating the entire transmission layer; the third bias strip line connects the lower metal strip lines in the third metal layer and the fifth metal layer together through a fifth metal via penetrating the entire transmission layer.

[0053] The absorption layer and the transmission layer are cascaded through an air matching layer to form the frequency selective absorbing device with a controllable high-selectivity transparent wave window of the present invention. Through simulation verification, by switching the bias states of the PIN diodes loaded on the absorption layer and the transmission layer, the switching between out-of-band absorption, in-band transparent wave mode and full-band absorption mode can be realized. Figures 8 - 9 This is the full-wave simulation result. Among them Figure 8 This is the S-parameter simulation result. (T represents the on state of the passband, and A represents the off state of the passband). By switching the working states of the PIN diodes loaded on the absorption layer and the transmission layer, the switching of the transparent wave window at 2 GHz can be realized. When the passband is on (T state), efficient transmission at 2 GHz (S21 transmission coefficient within -1 dB); when the passband is off (A state), the transmission coefficient is lower than -30 dB in the full frequency band. In both states, the reflection coefficient (S11) is suppressed in the full frequency band (S11 < -10 dB). Figure 9 This is the absorption rate simulation result. It can be seen that by switching the state, an absorption zero point (i.e., a transmission window) can be constructed within a wide absorption band to meet the front door protection requirements of the device.

[0054] The above are the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein, and should not be regarded as excluding other embodiments. Instead, it can be used in other combinations, modifications, and environments, and can be changed within the scope of the concept described herein through the above teachings or the techniques or knowledge in related fields. Any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A frequency selective absorbing device with a controllable highly selective transparent wave window, characterized in that: It includes an absorption layer and a transmission layer. The absorption layer and the transmission layer are fixed by non-metal columns, thereby forming an air layer (1) between the absorption layer and the transmission layer; The absorption layer includes a first dielectric plate (3), a first metal layer (2) disposed on the upper surface of the first dielectric plate (3), and a second metal layer (4) disposed between the lower surface of the first dielectric plate (3) and the air layer (1); The transmission layer includes a third metal layer (5), a second dielectric plate (6), a fourth metal layer (7), a third dielectric plate (8) and a fifth metal layer (9) arranged in sequence from top to bottom. The third metal layer (5) is adjacent to the air layer (1) and is located below the air layer (1); The first metal layer (2) includes two symmetric resonant units, namely a first resonant unit and a second resonant unit; Each resonant unit includes a U-shaped metal strip (2.1), and a first resistor (2.2), a first inductor (2.3) and a second resistor (2.4) are sequentially embedded along the U-shaped metal strip (2.1); one end of the first inductor (2.3) is connected to a first capacitor (2.5) through a first metal strip line, and the other end of the first inductor (2.3) is connected to a first PIN diode (2.7) through a second metal strip line. A third metal strip line is connected between the first capacitor (2.5) and the first PIN diode (2.7); A first choke coil (2.8) is also connected to the second metal strip line, and a second choke coil (2.6) is also connected to the third metal strip line.

2. The frequency selective absorbing device with a controllable high-selection transparent wave window according to claim 1, characterized in that: The first inductor (2.3) is a lumped inductor or a planar printed inductor; the first capacitor (2.5) is a lumped capacitor or a planar printed capacitor.

3. The frequency selective absorbing device with a controllable high-selection and transparent wave window according to claim 1, characterized in that: The second metal layer (4) includes two metal strip lines. The first metal strip line is connected to the first choke coils (2.8) of the first resonant unit and the second resonant unit respectively through two symmetric first metal vias (3.0); The second metal strip line is connected to the second choke coils (2.6) of the first resonant unit and the second resonant unit respectively through two symmetric second metal vias (2.9).

4. The frequency selective absorbing device with a controllable high-selection and transparent wave window according to claim 1, characterized in that: The third metal layer (5) and the fifth metal layer (9) have the same resonant structure for generating the resonance required to construct a passband. The resonant structure includes a first vertical metal strip line (11), and second vertical metal strip lines (12) and third vertical metal strip lines (13) that are symmetrically located on both sides of the first vertical metal strip line (11); The first vertical metal strip line (11) is provided with a first opening and a second opening from top to bottom, dividing the first vertical metal strip line (11) into an upper metal strip line, a middle metal strip line and a lower metal strip line; a diode unit (14) is disposed in each opening. The diode unit (14) includes a second PIN diode (10) and a planar printed capacitor. One end of the second PIN diode (10) is connected to the first end of the planar printed capacitor, and the other end of the second PIN diode (10) is connected to the second end of the planar printed capacitor; The first end of the planar printed capacitor in the first opening is also connected to the upper metal strip line, and the second end of the planar printed capacitor in the first opening is also connected to the middle metal strip line; the first end of the planar printed capacitor in the second opening is also connected to the middle metal strip line, and the second end of the planar printed capacitor in the second opening is also connected to the lower metal strip line.

5. The frequency selective absorbing device with a controllable high-selection and transparent wave window according to claim 4, characterized in that: The fourth metal layer (7) includes three parallel offset strip lines. The first offset strip line connects the upper metal strip lines in the third metal layer and the fifth metal layer together through a third metal via hole penetrating the entire transmission layer; the second offset strip line connects the middle metal strip lines in the third metal layer and the fifth metal layer together through a fourth metal via hole penetrating the entire transmission layer, and the third offset strip line connects the lower metal strip lines in the third metal layer and the fifth metal layer together through a fifth metal via hole penetrating the entire transmission layer.

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