An ultra-wideband cross coupler and millimeter wave low-loss attenuator

Abstract

The present invention discloses an ultra-wideband cross-coupler and a millimeter-wave low-loss attenuator, which relate to millimeter-wave attenuators and belong to the technical field of basic electronic circuits. The ultra-wideband cross-coupler adopts a method of combining a cross-metal core part with an extended metal wire, and uses a metal wire cross structure to achieve a compact structure while reducing insertion loss. The extended metal wires are symmetrically connected based on the core part, and the dual resonant frequency points generated by the two layers of metal are adjusted to achieve ultra-wideband coupling. The millimeter-wave low-insertion-loss attenuator includes: an ultra-wideband cross-coupler, a first control transistor and a second control transistor, a first mismatch resistor and a second mismatch resistor. Thanks to the low insertion loss and compact structure of the ultra-wideband cross-coupler, a reflective attenuator with a large attenuation range, low insertion loss and a compact structure is achieved under broadband conditions, and has excellent scientific application value.

Description

Technical Field

[0001] The invention belongs to the technical field of basic electronic circuits, relates to a millimeter wave attenuator, and relates to an ultra-wideband cross-coupler and a millimeter wave low insertion loss attenuator. Background Art

[0002] Phased array technology is widely used in 5G communications, satellite communications, and active electronically scanned array radars because of its wide operating bandwidth and unique advantages in wide-angle scanning. As an amplitude control unit, the attenuator is a key component of phased array technology. Its main functions are twofold: first, to compensate for the amplitude error caused by the phase shifter; second, to suppress the sidelobe level of the phased array antenna to make the antenna more directional. The performance of the attenuator will directly affect the performance indicators of the phased array, so the performance of the attenuator is of decisive significance to the phased array technology.

[0003] In the millimeter wave frequency band and above, there is a significant loss in signal transmission. In the traditional millimeter wave attenuator structure, the reflective attenuation structure has become one of the better solutions because of its small insertion loss and return loss, large attenuation range and compact structure. However, this requires a large number of quarter-wave transmission lines, which will increase the electromagnetic coupling between transmission lines and deteriorate the parasitic phase modulation performance while introducing large losses. In addition, the transmission line will occupy a large chip area, resulting in high manufacturing costs. Another common method is to use lumped elements instead of transmission lines to achieve the miniaturization of the coupler, but lumped elements will introduce significant losses in the millimeter wave frequency band, and there is also the problem of limited working bandwidth. These defects and deficiencies greatly limit the performance improvement of the attenuator in the millimeter wave frequency band and above.

[0004] The inventor has previously proposed Chinese patent CN109904576A, a ground-coupled hybrid coupler and a millimeter-wave ultra-wideband single-pole single-throw switch. The principle of the coupler is to use an upper metal layer in the form of a microstrip line in the horizontal direction and a lower metal layer in the form of a ground-coupled defective ground plane. The upper metal layer is connected to the lower metal layer through a metal through hole opened in itself, and the lower metal layer (ground plane layer) is etched with a gap symmetrical along the vertical direction and a polygonal pattern symmetrical along the horizontal direction. Therefore, it must use a more complex ground plane, that is, the ground plane metal layer is etched with a complex polygonal pattern and a gap symmetrical along the vertical direction. In addition, the coupler is applied to millimeter-wave switches, mainly to solve the technical problem that existing millimeter-wave switches are difficult to achieve low insertion loss and high isolation at the same time. However, it is difficult to obtain good performance in millimeter wave attenuators by using the above coupler. This is because in addition to higher insertion loss performance requirements, millimeter wave attenuators also need to pay attention to attenuation accuracy and parasitic phase modulation performance. Since the upper metal layer of the above coupler is exchange-connected through metal through-holes and defective ground planes, the parasitic phase modulation performance and attenuation accuracy will be significantly deteriorated in millimeter wave attenuators. Therefore, the coupler proposed in CN109904576A is not suitable for the design of millimeter wave attenuators.

[0005] The present invention proposes that the upper metal layer exchanges with the lower metal layer through a vertical metal through hole instead of exchanging with the ground plane metal layer, so there is no etching requirement for the ground plane metal layer; the length of the transmission line (including the gap) is greater than or equal to one quarter wavelength of the central operating frequency. Summary of the invention

[0006] The first purpose of the present invention is to address the deficiencies in the above-mentioned background technology and provide an ultra-wideband cross-coupler that achieves excellent low insertion loss performance in a compact structure size, thereby solving the technical problems of large loss and large size of attenuators in traditional technical means in millimeter wave and above frequency bands.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0008] An ultra-wideband cross coupler is implemented based on a cross transmission line, comprising a ground plane metal layer M1, a lower dielectric layer M2, an intermediate dielectric layer M3, and an upper dielectric layer M4; a first metal wire (1) is embedded in the upper dielectric layer M4, a first coupling gap is etched in the middle of the first metal wire (1) to form two sections of mutually coupled metal wires; one end of the first metal wire (1) is a coupling end, and the other end is a through end; a second metal wire (3) is embedded in the lower dielectric layer M2, and the second metal wire (3 ) is etched with a second coupling gap in the middle to form two sections of mutually coupled metal wires; the lengths of the first metal wire (1) and the second metal wire (3) are greater than or equal to a quarter wavelength of the central operating frequency; one end of the second metal wire (3) is an input end, and the other end is an isolation end; the input end of the second metal wire (3) is connected to the through end of the first metal wire (1) through a metal via (2); and the coupling end of the first metal wire (1) is connected to the isolation end of the second metal wire (3) through a metal via (2).

[0009] Preferably, the first metal line (1) comprises a first vertical line, a first oblique line, a first horizontal line, a second horizontal line, a second oblique line, and a second vertical line; one end of the first vertical line serves as a coupling end, and the other end is connected to one end of the first oblique line, the other end of the first oblique line is connected to one end of the first horizontal line, a first coupling gap is provided between the other end of the first horizontal line and one end of the second horizontal line, the other end of the second horizontal line is connected to one end of the second oblique line, the other end of the second oblique line is connected to one end of the second vertical line, and the other end of the second vertical line serves as a through end; the first coupling gap is a Z-shaped structure rotated 90° counterclockwise; the Z-shaped structure comprises a first vertical gap, a horizontal gap, and a second vertical gap, and the two ends of the horizontal gap are respectively arranged perpendicularly to one end of the first vertical gap and one end of the second vertical gap;

[0010] Preferably, the second metal line (3) comprises a third horizontal line, a third vertical line, a third oblique line, a fourth horizontal line, a fifth horizontal line, a fourth oblique line, a fourth vertical line, and a sixth horizontal line; one end of the third horizontal line serves as an input end, and the other end is connected to one end of the third vertical line, the other end of the third vertical line is connected to one end of the third oblique line, the other end of the third oblique line is connected to one end of the fourth horizontal line, a second coupling gap is provided between the other end of the fourth horizontal line and one end of the fifth horizontal line, the other end of the fifth horizontal line is connected to one end of the fourth oblique line, the other end of the fourth oblique line is connected to one end of the fourth vertical line, the other end of the fourth vertical line is connected to one end of the sixth horizontal line, and the other end of the sixth horizontal line serves as an isolation end; the second coupling gap is a Z-shaped structure mirroring the first coupling gap;

[0011] Preferably, the first horizontal line is connected to the end of the fifth horizontal line facing the second coupling slot through a metal via (2); the second horizontal line is connected to the end of the fourth horizontal line facing the second coupling slot through a metal via (2);

[0012] Preferably, the line widths of the first horizontal line, the second horizontal line, the fourth horizontal line, and the fifth horizontal line are all w;

[0013] The first horizontal line facing the first coupling slot end, the second horizontal line facing the first coupling slot end, the fourth horizontal line facing the second coupling slot end, and the fifth horizontal line facing the second coupling slot end are all provided with end extension lines, and the line widths of the end extension lines are all less than 0.5w.

[0014] Preferably, a notch is provided at the center of the ground plane metal layer M1 to weaken electromagnetic coupling;

[0015] The projections of the first metal line (1), the metal via (2) and the second metal line (3) on the ground plane metal layer M1 completely fall within the notch and do not contact the ground plane metal layer M1.

[0016] Preferably, the bandwidth and insertion loss of the coupler are regulated by the sizes of the first coupling gap and the second coupling gap.

[0017] Preferably, the operating frequency point and phase change of the coupler are regulated by adjusting the metal line width, length and thickness of the first metal line (1) and the second metal line (3).

[0018] Working principle:

[0019] Under the action of a strong electromagnetic field, the metal lines on both sides of the first coupling slot and the second coupling slot form edge coupling capacitance at the etched slot, and the edge coupling capacitance and the equivalent inductance of the metal lines form a resonant path, thereby reducing insertion loss. By adjusting the length, width and thickness of the first coupling slot and the second coupling slot, the edge coupling capacitance at the etched slot is changed, thereby adjusting the resonant frequency point and insertion loss of the resonant path.

[0020] The projection of the first metal line (1) falling on the lower dielectric layer M2 overlaps with the second metal line (3), and the overlapping portion includes a first vertical line, a first oblique line, a first horizontal line, a second horizontal line, a second oblique line, and a second vertical line of the first metal line (1); and a third vertical line, a third oblique line, a fourth horizontal line, a fifth horizontal line, a fourth oblique line, and a fourth vertical line of the second metal line (3).

[0021] The equivalent inductances of the overlapping parts of the first metal wire (1) and the second metal wire (3) are coupled to each other, equivalent to a transformer, which is beneficial to reducing the insertion loss of the attenuator; at the same time, under the electromagnetic field coupling between the first metal wire (1) and the second metal wire (3), the edge coupling capacitance generated and the metal wire equivalent inductance form a resonant path, further reducing the insertion loss. By adjusting the length, width and thickness of the first metal wire (1) and the second metal wire (3), the edge coupling capacitance and equivalent inductance of the metal wire are changed, thereby adjusting the transformer effect between the metal wires, the resonant frequency point of the resonant path and the insertion loss.

[0022] The inverter is realized by the edge coupling effect of the metal via, the first coupling slot and the second coupling slot, and the phase change control of the coupler is realized by combining with the transmission line of the quarter wavelength of the working frequency. The signal from the input end to the isolation end first passes through the one-eighth transmission line of the second metal line (3), and the signal phase changes to -45 degrees, passes through the inverter and the phase changes to 135 degrees, and then passes through the one-eighth transmission line of the second metal line (3), and the signal phase changes to 90 degrees; the signal from the input end to the through end first passes through the one-eighth transmission line of the second metal line (3), and the signal phase changes to -45 degrees, passes through the inverter and the phase remains -45 degrees, and then passes through the one-eighth transmission line of the first metal line (1), and the signal phase changes to -90 degrees; the signal from the input end to the coupling end first passes through the one-eighth transmission line of the second metal line (3), and the signal phase changes to -45 degrees, passes through the inverter and the phase changes to 45 degrees, and then passes through the one-eighth transmission line of the first metal line (1), and the signal phase changes to 0 degrees. Finally, the phase difference between the through end and the coupled end is 90 degrees, realizing the orthogonal characteristics of the coupler.

[0023] The second object of the present invention is to provide a millimeter wave low-loss attenuator, including an ultra-wideband cross-coupler, a first control transistor, a second control transistor, and a first mismatch resistor and a second mismatch resistor. The input port and the isolation port of the ultra-wideband cross-coupler are used as a signal input port and an output port respectively; the drain of the first control transistor is connected to the coupling end, and the source is connected to one end of the first mismatch resistor; the drain of the second control transistor is connected to the through end, and the source is connected to one end of the second mismatch resistor; the other end of the first mismatch resistor and the second mismatch resistor is connected to the ground plane; the gate of the first control transistor and the gate of the second control transistor are both connected to the same control voltage. When the control voltage is low, the first control transistor and the second control transistor are turned off, the coupling end of the cross-coupler and the through end are completely mismatched, and the attenuator is in a reference state; when the control level is high, the first control transistor and the second control transistor are turned on, the coupling end of the cross-coupler and the through end are partially mismatched, and the attenuator is in an attenuation state.

[0024] The third object of the present invention is to provide an attenuation control method for the above-mentioned millimeter wave low-loss attenuator, characterized in that when the control voltage VC is at a low level, the attenuator is in a reference state, the first control transistor and the second control transistor are turned off, the ultra-wideband cross-coupler is completely mismatched at the coupling end and the through end, and the signal is completely reflected to the output port;

[0025] When the control level VC is at a high level, the attenuator is in an attenuation state, the first control transistor and the second control transistor are turned on, the ultra-wideband cross-coupler is connected to the first mismatched resistor at the coupling end through the first control transistor, and the resistance value of the first mismatched resistor is adjusted to control the matching degree of the coupling end; it is connected to the second mismatched resistor at the through end through the second control transistor, and the resistance value of the second mismatched resistor is adjusted to control the matching degree of the through end, thereby controlling the signal reflected to the output port, thereby achieving different attenuation amounts.

[0026] The above technical solution has the following beneficial effects:

[0027] (1) The present invention realizes an ultra-wideband cross-coupler by cross-coupling metal wires of different layers, reduces insertion loss by using the transformer structure of the inductance of the upper and lower metal transmission lines and the edge coupling capacitor, and adjusts the phase change by combining the transmission line structure and the inverter; two coupling capacitors with different capacitances generated by the strong electromagnetic field between the metal wires of the same layer form a resonant circuit with the transmission line inductance, generating two resonance points with different frequencies, thereby reducing insertion loss and significantly increasing the working bandwidth.

[0028] (2) The millimeter-wave low-loss attenuator including an ultra-wideband cross-coupler proposed in the present invention has a compact overall structure and a small circuit area. It achieves excellent insertion loss, phase shift accuracy and parasitic phase modulation performance within the millimeter-wave ultra-wideband frequency range. It has great advantages and scientific application value in millimeter-wave integrated circuit design and can be widely used in millimeter-wave wireless communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a three-dimensional view of the ultra-wideband cross-coupler of the present invention;

[0030] Figure 2 (a) is a top view of the core part of the ultra-wideband cross coupler of the present invention; (b) is a side view of the core part of the ultra-wideband cross coupler of the present invention; (c) is a top view of the upper metal layer of the core part of the ultra-wideband cross coupler of the present invention; (d) is a top view of the lower metal layer of the core part of the ultra-wideband cross coupler of the present invention;

[0031] Figure 3 It is the simulation result comparing the ultra-wideband cross-coupling and the transmission line insertion loss of the present invention;

[0032] Figure 4It is a schematic diagram of the millimeter wave low-loss attenuator of the present invention;

[0033] Figure 5 This is the insertion loss simulation result of the millimeter wave low-loss attenuator of the present invention;

[0034] Figure 6 It is the simulation result of the attenuation of the millimeter wave low-loss attenuator of the present invention;

[0035] In the figure, the numbers are as follows: 1 is the first metal line, 2 is the metal via, 3 is the second metal line, M1 is the ground plane metal layer, M2 is the lower dielectric layer, M3 is the middle dielectric layer, and M4 is the upper dielectric layer; H represents the distance between M1 and M2, L and W are the length and width of M1 respectively, L1 and W1 are the length and width of the gap of M1 respectively, W2, W4, W5, L2, and L4 constitute the coupling gap of the transmission line, W3 is the transmission line width, L3 is the via width, D1 is the thickness of the first metal line, D2 is the thickness of the second metal line, P1 is the input end of the ultra-wideband cross-coupler, P2 is the isolation end of the ultra-wideband cross-coupler, P3 is the coupling end of the ultra-wideband cross-coupler, P4 is the through end of the ultra-wideband cross-coupler, T1 is the first control transistor of the millimeter-wave low insertion loss attenuator, T2 is the second control transistor of the millimeter-wave low insertion loss attenuator, R1 is the first mismatch resistor of the millimeter-wave low insertion loss attenuator, and R2 is the second mismatch resistor of the millimeter-wave low insertion loss attenuator. DETAILED DESCRIPTION

[0036] The technical solution of the invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the embodiments described are only used to explain the invention and are not used to limit the invention. After reading the application documents of the invention, various equivalent modifications made by those skilled in the art to the invention fall within the scope defined by the claims of the invention. In addition, the invention provides examples of specific processes and materials, but those of ordinary skill in the art can be aware of the applicability of other processes and / or the use of other materials.

[0037] The ultra-wideband cross coupler of the present invention is as follows Figure 1 As shown, from bottom to top, they are ground plane metal layer M1, lower dielectric layer M2, middle dielectric layer M3 connecting upper and lower metal layers, and upper dielectric layer M4. Figure 1 The upper dielectric layer M4 shown in the figure has a metal line width W3 and a thickness D1 along the middle mirror image. In the middle of the horizontal part of the metal line, according to Figure 2 (c) shows the top view of the upper metal layer of the core part. A gap is formed by etching in the horizontal and vertical directions. The horizontal part of the etched gap has a width of W2 and a length of L2. The vertical part of the etched gap has a width of W4 and a length of W5. The two vertical parts of the etched gap have the same size. The etched gap divides the metal line on the M4 dielectric layer into two mutually coupled parts. Figure 1The lower dielectric layer M2 shown in the figure has a metal line width W3 and a thickness D2 along the middle mirror image. In the middle of the horizontal part of the metal line, according to Figure 2 (d) shows the top view of the lower metal layer of the core part. A gap is formed by etching in the horizontal and vertical directions. The horizontal part of the etched gap has a width of W2 and a length of L2. The vertical part of the etched gap has a width of W4 and a length of W5. The two vertical parts of the etched gap have the same size. The etched gap divides the metal line on the M2 dielectric layer into two mutually coupled parts. Figure 1 The M3 dielectric layer, Figure 2 (a) and Figure 2 As shown in (b), at the intersecting part of the etched gaps located in the M4 dielectric layer and the M2 dielectric layer, a metal via hole on the M3 dielectric layer is used for connection, and its width is W5 and its length is L3, and the two metal via holes have the same size. Figure 1 As shown in the M1 metal layer, a rectangular blank area is etched on the M1 metal layer directly below the M2 dielectric layer and the M4 dielectric layer as a defective ground plane.

[0038] The insertion loss of the ultra-wideband cross coupler is as follows Figure 3 As shown, the cross-coupler shows lower insertion loss than the transmission line in the range of 80 GHz to 200 GHz. The two resonance points generated by the upper metal and the lower metal are located at 0.29 dB @ 86.4 GHz and 0.73 dB @ 175 GHz. The two resonance points are close in frequency, which greatly reduces the insertion loss and expands the bandwidth of the coupler.

[0039] The millimeter wave low loss attenuator of the present invention is as follows Figure 4 As shown, it includes an ultra-wideband cross coupler, a first control transistor T1, a second control transistor T2, and a first mismatch resistor R1 and a second mismatch resistor R2. The input port P1 and the isolation port P2 of the ultra-wideband cross coupler are used as a signal input port and an output port respectively, the drain of the first control transistor is connected to the coupling end P3 of the ultra-wideband cross coupler, and the source is connected to the first mismatch resistor. The drain of the second control transistor is connected to the through end P4 of the ultra-wideband cross coupler, and the source is connected to the second mismatch resistor. The other ends of the first mismatch resistor and the second mismatch resistor are connected to the ground plane. The gates of the two control transistors are connected to the same control voltage VC.

[0040] When the control voltage VC is at a low level, such as 0V, the attenuator is in a reference state, the first control transistor T1 and the second control transistor T2 are turned off, the ultra-wideband cross coupler is completely mismatched at the coupling end P3 and the through end P4, the signal is completely reflected to the output port P2, and the insertion loss is minimal;

[0041] When the control level VC is at a high level, such as 1.2V, the attenuator is in an attenuation state, the first control transistor T1 and the second control transistor T2 are turned on, and the ultra-wideband cross-coupler is connected to the first mismatched resistor R1 through the first control transistor T1 at the coupling end P3, and the resistance value of the first mismatched resistor R1 is adjusted to control the matching degree of the coupling end P3; the through-end P4 is connected to the second mismatched resistor R2 through the second control transistor T2, and the resistance value of the second mismatched resistor R2 is adjusted to control the matching degree of the through-end P4, thereby controlling the signal reflected to the output port P2, thereby achieving different attenuation amounts.

[0042] In order to achieve better performance through a symmetrical structure, the first mismatch resistor R1 and the second mismatch resistor R2 have the same resistance value. Since the millimeter wave attenuator adopts an ultra-wideband cross-coupling structure, low insertion loss, low return loss and wide bandwidth are achieved.

[0043] Under the joint action of the two resonance points of the ultra-wideband cross coupler, the insertion loss between the resonance point frequencies is small, but due to the structure of the coupler, the frequency range of large attenuation is narrow. In order to better balance the relationship between small insertion loss and large attenuation range, 160GHz~200GHz is selected as the operating frequency of the attenuator, such as Figure 5 and Figure 6 As shown. Different attenuation amounts are achieved by changing the resistance values ​​of the mismatched resistors R1 and R2. When VC is 0V, the first control transistor T1 and the second control transistor T2 are turned off, and the attenuator is in the reference state. At this time, the insertion loss of the attenuator is minimum and both are less than 1.5dB; when VC is 1.2V, the first control transistor T1 and the second control transistor T2 are turned on, and the attenuator is in the attenuation state. By changing the resistance values ​​of the first mismatched resistor R1 and the second mismatched resistor R2, different attenuation states are achieved. When the resistance values ​​of the two mismatched resistors are both 9ohm, the insertion loss of the attenuator increases, and the attenuation amount relative to the reference state insertion loss is 2dB; when the resistance values ​​of the two mismatched resistors are both 18ohm, the insertion loss of the attenuator is further increased, and the attenuation amount relative to the reference state insertion loss is 4dB; when the resistance values ​​of the two mismatched resistors are both 36ohm, the insertion loss of the attenuator is further increased, and the attenuation amount relative to the reference state insertion loss is 8dB. It can be seen that the millimeter-wave low insertion loss attenuator has a large attenuation range in a wide bandwidth, and at the same time, the insertion loss is small.

[0044] Although the specific embodiments of the present invention are described above in conjunction with the accompanying drawings, it should be understood by those skilled in the art that these are only examples, and that various variations or modifications may be made to these embodiments without departing from the principles and essence of the present invention. The scope of the present invention is limited only by the appended claims.

Claims

1. An ultra-wideband cross coupler, characterized in that It includes a ground plane metal layer M1, a lower dielectric layer M2, a middle dielectric layer M3, and an upper dielectric layer M4; A first metal wire (1) is embedded in the upper dielectric layer M4, and a first coupling gap is etched in the middle of the first metal wire (1) to form two sections of mutually coupled metal wires; one end of the first metal wire (1) is a coupling end, and the other end is a through end; A second metal wire (3) is embedded in the lower dielectric layer M2, and a second coupling gap is etched in the middle of the second metal wire (3) to form two sections of mutually coupled metal wires; one end of the second metal wire (3) is an input end, and the other end is an isolation end; The input end of the second metal wire (3) is connected to the through end of the first metal wire (1) through a metal via (2); the coupling end of the first metal wire (1) is connected to the isolation end of the second metal wire (3) through a metal via (2); The lengths of the first metal wire (1) and the second metal wire (3) are greater than or equal to one quarter of the wavelength of the central operating frequency; The first metal line (1) comprises a first vertical line, a first oblique line, a first horizontal line, a second horizontal line, a second oblique line, and a second vertical line; one end of the first vertical line serves as a coupling end, and the other end is connected to one end of the first oblique line, the other end of the first oblique line is connected to one end of the first horizontal line, a first coupling gap is provided between the other end of the first horizontal line and one end of the second horizontal line, the other end of the second horizontal line is connected to one end of the second oblique line, the other end of the second oblique line is connected to one end of the second vertical line, and the other end of the second vertical line serves as a through end; the first coupling gap is a Z-shaped structure rotated 90° counterclockwise; the Z-shaped structure comprises a first vertical gap, a horizontal gap, and a second vertical gap, and the two ends of the horizontal gap are respectively arranged perpendicularly to one end of the first vertical gap and one end of the second vertical gap; The second metal line (3) comprises a third horizontal line, a third vertical line, a third oblique line, a fourth horizontal line, a fifth horizontal line, a fourth oblique line, a fourth vertical line, and a sixth horizontal line; one end of the third horizontal line serves as an input end, and the other end is connected to one end of the third vertical line, the other end of the third vertical line is connected to one end of the third oblique line, the other end of the third oblique line is connected to one end of the fourth horizontal line, a second coupling gap is provided between the other end of the fourth horizontal line and one end of the fifth horizontal line, the other end of the fifth horizontal line is connected to one end of the fourth oblique line, the other end of the fourth oblique line is connected to one end of the fourth vertical line, the other end of the fourth vertical line is connected to one end of the sixth horizontal line, and the other end of the sixth horizontal line serves as an isolation end; The second coupling slot is a Z-shaped structure that is mirror-imaged to the first coupling slot.

2. The ultra-wideband cross coupler according to claim 1, characterized in that The first coupling slot end of the first horizontal line is connected to the second coupling slot end of the fifth horizontal line through a metal via (2); the first coupling slot end of the second horizontal line is connected to the second coupling slot end of the fourth horizontal line through a metal via (2).

3. An ultra-wideband cross coupler according to claim 1 or 2, characterized in that The line widths of the first horizontal line, the second horizontal line, the fourth horizontal line and the fifth horizontal line are all w; The first horizontal line facing the first coupling slot end, the second horizontal line facing the first coupling slot end, the fourth horizontal line facing the second coupling slot end, and the fifth horizontal line facing the second coupling slot end are all provided with end extension lines, and the line widths of the end extension lines are all less than 0.5w.

4. The ultra-wideband cross coupler according to claim 1, characterized in that A notch is formed in the center of the ground plane metal layer M1 to weaken electromagnetic coupling; The projections of the first metal wire (1), the metal via (2) and the second metal wire (3) on the ground plane metal layer M1 completely fall within the notch and do not contact the ground plane metal layer M1.

5. The ultra-wideband cross coupler according to claim 1, characterized in that The bandwidth and insertion loss of the coupler are regulated by the sizes of the first coupling gap and the second coupling gap.

6. The ultra-wideband cross coupler according to claim 1, characterized in that The operating frequency point of the coupler is regulated by the metal line width, length and thickness of the first metal line (1) and the second metal line (3).

7. A millimeter wave low-loss attenuator, comprising a coupler, a first control transistor, a second control transistor, and a first mismatch resistor and a second mismatch resistor; the input port and the isolation port of the coupler are respectively used as a signal input port and an output port; the drain of the first control transistor is connected to the coupling end, and the source is connected to one end of the first mismatch resistor; the drain of the second control transistor is connected to the through end, and the source is connected to one end of the second mismatch resistor; the other ends of the first mismatch resistor and the second mismatch resistor are connected to the ground plane; the gate of the first control transistor and the gate of the second control transistor are both connected to the same control voltage; characterized in that, The coupler adopts the ultra-wideband cross coupler according to any one of claims 1 to 6; When the control voltage is at a low level, the first control transistor and the second control transistor are turned off, the coupling end and the through end of the cross coupler are completely mismatched, and the attenuator is in a reference state; when the control level is at a high level, the first control transistor and the second control transistor are turned on, the coupling end and the through end of the cross coupler are partially mismatched, and the attenuator is in an attenuation state.

8. The attenuation control method of the attenuator according to claim 7, characterized in that When the control voltage VC is at a low level, the attenuator is in a reference state, the first control transistor and the second control transistor are turned off, the ultra-wideband cross coupler is completely mismatched at the coupling end and the through end, and the signal is completely reflected to the output port; When the control level VC is at a high level, the attenuator is in an attenuation state, the first control transistor and the second control transistor are turned on, the ultra-wideband cross-coupler is connected to the first mismatch resistor at the coupling end through the first control transistor, and the resistance value of the first mismatch resistor is adjusted to control the matching degree of the coupling end; The through-end is connected to the second mismatch resistor through the second control transistor, and the resistance value of the second mismatch resistor is adjusted to control the matching degree of the through-end, thereby controlling the signal reflected to the output port, thereby achieving different attenuation amounts.

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