阅读说明：本技术 一种基于pin二极管的x波段超宽带电控有源频率选择表面及其加工测试方法 (X-waveband ultra-wideband electronic control active frequency selection surface based on PIN diode and processing and testing method thereof ) 是由 傅佳辉 赵宇霖 王哲飞 陈晚 张群豪 吕博 于 2020-10-30 设计创作，主要内容包括：本发明公开了一种基于PIN二极管的X波段超宽带电控有源频率选择表面及其加工测试方法。所述3层金属板单元和2层介质板单元间隔设置,中间层金属板单元的中心设置圆形缝隙,上层金属板单元贴合上层介质板单元,底层金属板单元贴合下层介质板单元,所述上层金属板单元的横向设置贴片缝隙,所述上层金属板单元的竖向设置交指电容缝隙,所述上层金属板单元的中心设置方形缝隙；所述上层金属板单元与底层金属板单元结构相同,所述底层金属板单元相对于上层金属板单元旋转90度；所述贴片缝隙上垂直设置PIN二极管。能够根据天线系统的工作状态实时调整自身性能。(The invention discloses an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode and a processing and testing method thereof. The three-layer metal plate unit comprises a 3-layer metal plate unit, a 2-layer dielectric plate unit, an upper-layer metal plate unit, a lower-layer dielectric plate unit, a patch gap, an interdigital capacitor gap and a square gap, wherein the 3-layer metal plate unit and the 2-layer dielectric plate unit are arranged at intervals; the upper layer metal plate unit and the bottom layer metal plate unit have the same structure, and the bottom layer metal plate unit rotates 90 degrees relative to the upper layer metal plate unit; and a PIN diode is vertically arranged on the patch gap. The performance of the antenna system can be adjusted in real time according to the working state of the antenna system.)

1. An X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode is characterized in that an electronic control active frequency selection surface unit comprises 3 layers of metal plate units and 2 layers of dielectric plate units, the 3 layers of metal plate units and the 2 layers of dielectric plate units are arranged at intervals, a circular gap is arranged in the center of a middle layer of metal plate unit, an upper layer of metal plate unit is attached to an upper layer of dielectric plate unit, a lower layer of metal plate unit is attached to a lower layer of dielectric plate unit, a patch gap is transversely arranged on the upper layer of metal plate unit, an interdigital capacitor gap is vertically arranged on the upper layer of metal plate unit, and a square gap is arranged in the center of the upper layer of metal plate unit;

the upper layer metal plate unit and the bottom layer metal plate unit have the same structure, and the bottom layer metal plate unit rotates 90 degrees relative to the upper layer metal plate unit;

and a PIN diode is vertically arranged on the patch gap.

2. The PIN diode-based X-band ultra-wideband electrically controlled active frequency selective surface according to claim 1, wherein the metal plate element has a length equal to the width, the length a of the metal plate element is 6.0mm, and the width g of the patch slot is equal to the width of the patch slot₁0.15mm, length a from the width edge of the patch slot to the edge of the metal plate unit₂The/2 is 5.85/2mm, and the width of the square gap is the finger length w + g of the interdigital capacitor₁0.6+ 0.15-0.75 mm, the length a from the edge of the width of the square slit to the edge of the sheet metal element₁Per 2 is 5.3/2mm, and the width a of the patch without interdigital capacitor₃The thickness of the film is 1.13mm,

the interdigital capacitor gap is communicated with the n-type capacitor gap in a U-type mode, and the interdigital capacitor gap has the transverse width g₂Is 0.1mm, and the longitudinal width s of the interdigital capacitor gap₂Is 0.1mm, and the finger width s of the interdigital capacitor₁Is 0.1mm, and the finger length w of the interdigital capacitor is 0.6 mm.

3. An X-band ultra-wideband electrically controlled active frequency selective surface based on PIN diodes according to claim 1, characterized in that the diameter of the circular slot is 2X r.

4. The PIN diode-based X-band ultra-wideband electrically controlled active frequency selective surface according to claim 1, wherein the upper dielectric slab unit and the lower dielectric slab unit both have a thickness h of 0.508 mm.

5. The method for processing an X-waveband ultra-wideband electrically-controlled active frequency selection surface based on a PIN diode as claimed in claim 1, wherein the processing method comprises the following steps:

step 1: arranging and combining the electric control active frequency selection surface units according to actual needs, and then processing the electric control active frequency selection surface units, wherein the upper edge and the lower edge of the combined whole structure are respectively welded with a radio frequency inductor and a direct current feeder;

step 2: a PIN diode is vertically welded between every two electric control active frequency selection surface units;

and step 3: the PIN diodes on the front face of the AFSS and the anodes of the direct current feeder lines are welded to the uppermost side of each row of PIN diodes; the cathode of the direct current feeder is welded on the lowest side of each row of PIN diodes;

and 4, step 4: in the step 3, each row of PIN diodes is connected with a resistor in series and then connected in parallel;

and 5: in the step 3, each row of PIN diodes shares the same cathode feeder line;

step 6: detecting each welded element to ensure that all PIN diodes, radio frequency inductors and resistors are not in cold joint and can normally work, meanwhile, conducting test needs to be carried out on each row of PIN diodes, and each PIN diode on the AFSS can be conducted when a direct current power supply supplies power;

and 7: fixing an AFSS piece to be tested in a hole in the middle of the metal reflecting plate;

and 8: covering the periphery of the AFSS part with a copper foil adhesive tape to ensure that the periphery of the AFSS part is a metal reflecting plate;

and step 9: an ultra-wideband horn with a working frequency band of 1-18GHz is respectively arranged in front of and behind the metal reflecting plate and is used as a transmitting antenna and a receiving antenna;

step 10: the two loudspeakers in the step 9 are connected with two ports of the vector network analyzer through coaxial lines;

step 11: the direct current feeders on the front side and the back side of the AFSS part are connected with a direct current power supply;

step 12: and finishing the processing.

6. The method for testing the X-band ultra-wideband electrically controlled active frequency selective surface based on the PIN diode as claimed in claim 5, wherein the method comprises the following steps:

the method comprises the following steps: setting a test frequency band to be 2-18 GHz;

step two: respectively testing the transmission coefficients of the no-load metal reflecting plate and the metal reflecting plate loaded with the AFSS part;

step three: the transmission coefficient of the actual AFSS part is obtained through comparison.

Technical Field

The invention belongs to the field of radar; in particular to an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode and a processing and testing method thereof.

Background

With the continuous development of the technology in the fields of military, industry, communication and the like in China, the antenna housing taking the conventional passive Frequency Selective Surface (FSS) as a material cannot adapt to various flexible application scenes due to single function and non-adjustable working state. Compared with an electrically controlled Active Frequency Selection Surface (AFSS) designed in the present invention, the conventional passive Frequency selection Surface scheme has the following defects: (1) the working state is fixed, and the function is single; (2) the transmission bandwidth is narrow, and the ultra-wideband application cannot be met; (3) the oblique incidence stability is poor, and the normal work under the large-angle oblique incidence cannot be ensured; (4) the polarization stability is poor, and dual polarization work cannot be realized.

Disclosure of Invention

The invention provides an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode and a processing and testing method thereof, which can adjust the performance of an antenna system in real time according to the working state of the antenna system, keep the transmission state when the antenna system works, and allow electromagnetic waves in the frequency band of one party to normally come in and go out; when the antenna system is closed, the shielding state is kept, and enemies and interference electromagnetic waves are prohibited from entering, so that the normal work of the communication system is ensured.

The invention is realized by the following technical scheme:

an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode is disclosed, wherein the electronic control active frequency selection surface unit comprises 3 layers of metal plate units and 2 layers of dielectric plate units, the 3 layers of metal plate units and the 2 layers of dielectric plate units are arranged at intervals, a circular gap is arranged in the center of the middle layer of metal plate unit, the upper layer of metal plate unit is attached to the upper layer of dielectric plate unit, the bottom layer of metal plate unit is attached to the lower layer of dielectric plate unit, a patch gap is transversely arranged on the upper layer of metal plate unit, an interdigital capacitor gap is vertically arranged on the upper layer of metal plate unit, and a square gap is arranged in the center of the upper layer of metal plate unit;

the upper layer metal plate unit and the bottom layer metal plate unit have the same structure, and the bottom layer metal plate unit rotates 90 degrees relative to the upper layer metal plate unit;

and a PIN diode is vertically arranged on the patch gap.

Further, the length and the width of the metal plate unit are equal, the length a of the metal plate unit is 6.0mm, and the width g of the patch gap₁0.15mm, length a from the width edge of the patch slot to the edge of the metal plate unit₂The/2 is 5.85/2mm, and the width of the square gap is the finger length w + g of the interdigital capacitor₁0.6+ 0.15-0.75 mm, the length a from the edge of the width of the square slit to the edge of the sheet metal element₁Per 2 is 5.3/2mm, and the width a of the patch without interdigital capacitor₃The thickness of the film is 1.13mm,

the interdigital capacitor gap is communicated with the n-type capacitor gap in a U-type mode, and the interdigital capacitor gap has the transverse width g₂Is 0.1mm, and the longitudinal width s of the interdigital capacitor gap₂Is 0.1mm, and the finger width s of the interdigital capacitor₁Is 0.1mm, and the finger length w of the interdigital capacitor is 0.6 mm.

Further, the diameter of the circular slit is 2 x r.

Furthermore, the thickness h of the upper-layer dielectric slab unit and the lower-layer dielectric slab unit is 0.508 mm.

A processing method of an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode comprises the following steps:

step 1: arranging and combining the electric control active frequency selection surface units according to actual needs, and then processing the electric control active frequency selection surface units, wherein the upper edge and the lower edge of the combined whole structure are respectively welded with a radio frequency inductor and a direct current feeder;

step 2: a PIN diode is vertically welded between every two electric control active frequency selection surface units;

and step 3: the PIN diodes on the front face of the AFSS and the anodes of the direct current feeder lines are welded to the uppermost side of each row of PIN diodes; the cathode of the direct current feeder is welded on the lowest side of each row of PIN diodes;

and 4, step 4: in the step 3, after a resistor is connected in series with each row of PIN diodes, the PIN diodes in each row are connected in parallel;

and 5: in the step 3, each row of PIN diodes shares the same cathode feeder line;

step 6: detecting each welded element to ensure that all PIN diodes, radio frequency inductors and resistors are not in cold joint and can normally work, meanwhile, conducting test needs to be carried out on each row of PIN diodes, and each PIN diode on the AFSS can be conducted when a direct current power supply supplies power;

and 7: fixing an AFSS piece to be tested in a hole in the middle of the metal reflecting plate;

and 8: covering the periphery of the AFSS part with a copper foil adhesive tape to ensure that the periphery of the AFSS part is a metal reflecting plate;

and step 9: an ultra-wideband horn with a working frequency band of 1-18GHz is respectively arranged in front of and behind the metal reflecting plate and is used as a transmitting antenna and a receiving antenna;

step 10: the two loudspeakers in the step 9 are connected with two ports of the vector network analyzer through coaxial lines;

step 11: the direct current feeders on the front side and the back side of the AFSS part are connected with a direct current power supply;

step 12: and finishing the processing.

A test method of an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode comprises the following steps:

the method comprises the following steps: setting a test frequency band to be 2-18 GHz;

step two: respectively testing the transmission coefficients of the no-load metal reflecting plate and the metal reflecting plate loaded with the AFSS part;

step three: the transmission coefficient of the actual AFSS part is obtained through comparison.

The invention has the beneficial effects that:

1. the invention realizes the adjustability of functions, can switch between a transmission state and a shielding state, and breaks the limitation of single function in the prior art.

2. The invention realizes the ultra-wideband transmission of the X wave band, the high-efficiency transmission bandwidth reaches 2.32GHz and is far beyond the existing electric control active frequency selection surface of the X wave band.

3. The oblique incidence surface has good stability, can ensure good working performance for oblique incidence electromagnetic waves within 30 degrees, and is superior to the existing electric control active frequency selection surface.

4. The invention has good polarization stability, can ensure normal work for TE and TM polarized electromagnetic waves, and is superior to the existing electric control active frequency selection surface.

5. The equivalent circuit model of the PIN diode is corrected, a transmission line element is introduced into the original model, and the corrected equivalent circuit model can fit not only an S-parameter amplitude curve of the PIN diode but also an S-parameter phase curve which cannot be fitted by the original model.

6. The invention greatly widens the transmission bandwidth of the electric control active frequency selection surface by utilizing the coupling effect between the metal layers on the premise of not increasing the thickness of the whole structure.

7. The invention uses serial feed and upper and lower layers of orthogonal feed for loaded PIN diodes, reduces the number of PIN diodes by half, and simplifies the direct current feed structure.

Drawings

Fig. 1 is a schematic structural view of the present invention, wherein (a) is a perspective view of an electrically controlled active frequency selective surface unit and (b) is a side view of the electrically controlled active frequency selective surface unit.

Fig. 2 is a schematic structural diagram of each layer of metal of the present invention, wherein (a) an electrically controlled active frequency selective surface upper layer metal plate, (b) an electrically controlled active frequency selective surface middle layer metal plate, and (c) an electrically controlled active frequency selective surface bottom layer metal plate.

FIG. 3 is an equivalent circuit diagram of the PIN diode of the present invention, wherein (a) the equivalent circuit model circuit diagram is in a forward bias state, and (b) the equivalent circuit model circuit diagram is in a reverse bias state.

FIG. 4 is a schematic diagram of the welding and feeding mode of the PIN diode of the invention.

FIG. 5 is a graphical representation of AFSS performance at TE polarization (vertical polarization) incidence obtained by numerical simulation of the present invention.

FIG. 6 is a graphical representation of AFSS performance at TM polarization (horizontal polarization) incidence obtained from numerical simulation of the present invention.

FIG. 7 is a welded AFSS prototype of the invention.

Fig. 8 shows a power supply board for dc feeding of the present invention.

FIG. 9 is a diagram showing the transmission coefficient of AFSS samples in TE polarization obtained by the test of the present invention.

FIG. 10 is a diagram showing the transmission coefficient of AFSS samples in TM polarization obtained by the test of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

An X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode is disclosed, wherein the electronic control active frequency selection surface unit comprises 3 layers of metal plate units and 2 layers of dielectric plate units, the 3 layers of metal plate units and the 2 layers of dielectric plate units are arranged at intervals, a circular gap is arranged in the center of the middle layer of metal plate unit, the upper layer of metal plate unit is attached to the upper layer of dielectric plate unit, the bottom layer of metal plate unit is attached to the lower layer of dielectric plate unit, a patch gap is arranged vertically on the upper layer of metal plate unit, an interdigital capacitor gap is arranged horizontally on the upper layer of metal plate unit, and a square gap is arranged in the center of the upper layer of metal plate unit;

the upper layer metal plate unit and the bottom layer metal plate unit have the same structure, and the bottom layer metal plate unit rotates 90 degrees relative to the upper layer metal plate unit;

and a PIN diode is vertically arranged on the patch gap.

Further, the length and the width of the metal plate unit are equal, the length a of the metal plate unit is 6.0mm, and the width g of the patch gap₁0.15mm, said patchLength a from the edge of the slit width to the edge of the sheet metal unit₂The/2 is 5.85/2mm, and the width of the square gap is the finger length w + g of the interdigital capacitor₁0.6+ 0.15-0.75 mm, the length a from the edge of the width of the square slit to the edge of the sheet metal element₁The/2 is 5.3mm/2, the width a of the patch without interdigital capacitor₃The thickness of the film is 1.13mm,

the interdigital capacitor gap is communicated with the n-type capacitor gap in a U-type mode, and the interdigital capacitor gap has the transverse width g₂Is 0.1mm, and the longitudinal width s of the interdigital capacitor gap₂Is 0.1mm, and the finger width s of the interdigital capacitor₁Is 0.1mm, and the finger length w of the interdigital capacitor is 0.6 mm.

Further, the diameter of the circular slit is 2 x r.

Furthermore, the thickness h of the upper-layer dielectric slab unit and the lower-layer dielectric slab unit is 0.508 mm.

Furthermore, the upper layer metal plate unit and the bottom layer metal plate unit are made of copper, and the thickness t of the upper layer metal plate unit and the bottom layer metal plate unit is 18 micrometers. A processing method of an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode comprises the following steps:

step 1: arranging and combining the electric control active frequency selection surface units according to actual needs, and then processing the electric control active frequency selection surface units, wherein the upper edge and the lower edge of the combined whole structure are respectively welded with a radio frequency inductor and a direct current feeder;

step 2: a PIN diode is vertically welded between every two electric control active frequency selection surface units;

and step 3: the PIN diodes on the front face of the AFSS and the anodes of the direct current feeder lines are welded to the uppermost side of each row of PIN diodes; the cathode of the direct current feeder is welded on the lowest side of each row of PIN diodes;

and 4, step 4: in the step 3, after a resistor is connected in series with each row of PIN diodes, the PIN diodes in each row are connected in parallel;

and 5: in the step 3, each row of PIN diodes shares the same cathode feeder line;

step 6: detecting each welded element to ensure that all PIN diodes, radio frequency inductors and resistors are not in cold joint and can normally work, meanwhile, conducting test needs to be carried out on each row of PIN diodes, and each PIN diode on the AFSS can be conducted when a direct current power supply supplies power;

and 7: fixing an AFSS piece to be tested in a hole in the middle of the metal reflecting plate;

and 8: covering the periphery of the AFSS part with a copper foil adhesive tape to ensure that the periphery of the AFSS part is a metal reflecting plate;

and step 9: an ultra-wideband horn with a working frequency band of 1-18GHz is respectively arranged in front of and behind the metal reflecting plate and is used as a transmitting antenna and a receiving antenna;

step 10: the two loudspeakers in the step 9 are connected with two ports of the vector network analyzer through coaxial lines;

step 11: the direct current feeders on the front side and the back side of the AFSS part are connected with a direct current power supply;

step 12: and finishing the processing.

A test method of an X-waveband ultra-wideband electronic control active frequency selection surface based on a PIN diode comprises the following steps:

the method comprises the following steps: setting a test frequency band to be 2-18 GHz;

step two: respectively testing the transmission coefficients of the no-load metal reflecting plate and the metal reflecting plate loaded with the AFSS part;

step three: the transmission coefficient of the actual AFSS part is obtained through comparison.

Example 2

The structure of the electric control active frequency selection surface unit is shown in figure 1, the structure is composed of 3 layers of metal and 2 layers of medium, the upper layer and the lower layer of metal are mainly square patch structures, the middle layer of metal is a circular gap structure, the medium plate material is Rogers RT5880, and the relative dielectric constant epsilon_rIs 2.2, and the thickness h of each dielectric plate is 0.508 mm. The structure of each layer of metal unit is shown in fig. 2, the structures of the metal units of the top layer and the bottom layer are completely the same, but are rotated by 90 degrees, the directions of the PIN diodes loaded on the top layer and the bottom layer are perpendicular to each other, and the values of various parameters in the figure are shown in table 1.

Table 1 structural parameters of electrically controlled active frequency selective surface unit

Selecting a PIN diode special for radio frequency, putting an equivalent circuit model of the PIN diode into a simulation model of an electronic control active frequency selection surface unit, and performing simulation optimization to obtain the optimal performance, wherein the equivalent circuit model of the PIN diode is shown in figure 3, and element value parameters in the model are shown in table 2.

TABLE 2 component value parameters in PIN diode equivalent circuit model

The manner of soldering and feeding the PIN diode will be described next, as shown in fig. 4. All units in the same direction on the upper layer metal are completely connected by the PIN diodes, so that during actual processing, each row of PIN diodes can be fed in series at the edge through a group of direct current feeders connected with the positive electrode and the negative electrode of a direct current power supply. The feeder line on the lower layer metal is completely the same as the upper layer structure, and the direction is rotated by 90 degrees. As can be seen from fig. 4, for the same column, each diode has a series relationship, and each row is connected in parallel, and since the actually processed AFSS has a boundary, feeder lines respectively connected to the positive and negative electrodes of the voltage source are added on both sides of the boundary, so that simultaneous feeding of all diodes is realized.

Through numerical simulation, the overall performance of the coupled broadband AFSS under TE polarization (vertical polarization) incidence is shown in fig. 5, and the overall performance of the coupled broadband AFSS under TM polarization (horizontal polarization) incidence is shown in fig. 6. In the figure, the | S21|, i.e. the transmission coefficient, of the coupled broadband AFSS is shown when the incident angles are 0 °, 10 °, 20 °, and 30 ° respectively in two states of "transmission" (zero-bias or reverse-bias PIN diode) and "shielding" (forward-bias PIN diode).

As can be seen from fig. 5 and 6, in the coupled broadband AFSS designed in this section, in the "transmission" state, the transmission bandwidth (| S21| ≧ 1dB) is 8.38-10.7GHz (absolute bandwidth 2.32GHz, relative bandwidth 24.3%), and the maximum insertion loss in the transmission band is 1dB (corresponding to 80% transmittance); under the shielding state, the shielding bandwidth (| S21| ≦ -10dB) is 2-18 GHz. And under two polarization states (vertical polarization and horizontal polarization), the maximum incident angle can reach about 30 degrees.

And (4) carrying out physical processing and testing based on the designed AFSS unit structure. The PIN diode, the radio frequency inductor, the direct current feeder and the like are welded to the coupled broadband AFSS, and the welded AFSS sample is shown in fig. 7. For the PIN diodes on the front face of the AFSS, the anode of the direct current feeder is welded on the uppermost side of each row of PIN diodes and is represented by red lines; the negative pole of direct current feeder welds the downside at every row PIN diode, and 13 rows PIN diodes share same negative pole feeder, show with the black line. Considering that all current flows through the path with the smallest resistance when the semiconductor devices are connected in parallel, the 13 rows of PIN diodes cannot be directly connected in parallel, but a resistor is connected in series with each row of PIN diodes and then connected in parallel, so that the current can be uniformly distributed in each path, and therefore, a power panel for direct current feeding is additionally designed, as shown in fig. 8.

For each polarization mode and each oblique incidence angle, the | S21| parameter of the PIN diode in zero bias (off) state and positive bias (on) state needs to be tested. When the PIN diode is in zero bias, the AFSS sample piece is in a transmission state; when the PIN diode is reversely biased, the AFSS sample piece is in a shielding state. The transmission and shielding performance of the obtained AFSS samples are shown in FIGS. 9 and 10. As can be seen from fig. 9 and 10, for both TE (vertical polarization) and TM (horizontal polarization), in the transmission state (OFF-state) of the AFSS sample, the transmission bandwidth with the transmittance higher than 80% is about 2GHz, and substantially covers 8-10 GHz; in the shielding state (ON-state), the shielding bandwidth covers 2-18 GHz. In addition, the AFSS sample piece has good oblique incidence stability, and the oblique incidence angle can reach about 30 degrees. In summary, the test results of the AFSS sample substantially match the simulation results.

Detection of the welded component:

for the AFSS sample piece, after welding is completed, each welded element needs to be detected, all PIN diodes, radio frequency inductors and resistors are guaranteed to be free of cold solder joint and capable of working normally, meanwhile, conducting test needs to be conducted on each row of PIN diodes, and it is guaranteed that each PIN diode on the AFSS can be conducted when a direct current power supply supplies power in the subsequent testing process. During feeding, a positive feeder line and a negative feeder line on the power panel are respectively connected to a positive electrode and a negative electrode of the direct-current power supply, then the output voltage of the direct-current power supply is set to be 15V, the highest output current is set to be 30mA, 13 rows of 2 surfaces are 780mA, and thus 30mA current can be guaranteed to flow on each row of PIN diodes.

The testing and working process comprises the following steps:

fixing the AFSS sample to be tested in the middle of a metal reflecting plate of 1.5m by 1.5m, digging a hole of 200mm by 200mm in the middle of the metal reflecting plate, and covering the periphery of the AFSS sample by using copper foil adhesive tape to ensure that the periphery of the AFSS sample is all provided with the metal reflecting plate. An ultra-wideband horn with a working frequency band of 1-18GHz is respectively placed before and after metal reflection to serve as a transmitting antenna and a receiving antenna, the two horns are dual-polarized horns and can generate vertically polarized waves and horizontally polarized waves, and the two horns are connected with two ports of a vector network analyzer through coaxial lines. Direct current feeder lines on the front surface and the back surface of the AFSS sample piece are connected with a direct current power supply, and meanwhile, in order to prevent the plate from deforming due to overhigh temperature when the PIN diode is forward biased, the AFSS sample piece is cooled by the aid of an electric fan.

During testing, the testing frequency band of the vector network analyzer is set to be 2-18GHz, which is the same as that during numerical simulation. In order to obtain the transmission coefficient of the AFSS sample, it is necessary to test the | S21| parameters of the two cases of no-load (no AFSS sample is placed in the middle of the metal reflector) and loading the AFSS sample, and then obtain the actual transmission coefficient of the AFSS sample by comparison.

For each polarization mode and each oblique incidence angle, the | S21| parameter of the PIN diode in zero bias (off) state and positive bias (on) state needs to be tested. When the PIN diode is in zero bias, the AFSS sample piece is in a transmission state; when the PIN diode is reversely biased, the AFSS sample piece is in a shielding state.