TWI715343B - Antenna device based on modified rotman lens - Google Patents

Abstract

An antenna device based on a modified Rotman lens is provided. The antenna device includes a dielectric substrate and a conductor layer. The conductor layer is disposed on a surface of the dielectric substrate, wherein the conductor layer includes an input port array, an output port array, and a cavity. The cavity connects the input port array to the output port array and includes a reflective structure, wherein the reflective structure forms a symmetry axis of the output port array and a virtual output port array, wherein the virtual output port array corresponds to an output port array of a conventional Rotman lens.

Description

Antenna device based on improved Rotman lens

The present invention relates to an antenna device, and more particularly to an antenna device based on an improved Rotman lens.

In response to the advent of the IoT era, the development of 5G technology will increase the transmission rate and reduce communication delays through greater bandwidth. Compared with the current LTE frequency band, 5G uses high-frequency spectrum for data transmission, and the path loss in the transmission process will reduce the cell coverage, so massive antenna systems and beamforming technology will be indispensable. Rotman lens (Rotman lens) beamforming network has considerable advantages over other beamforming technologies due to its wide impedance bandwidth and low antenna beam pointing deflection. Furthermore, since the Rotman lens can be implemented in combination with the substrate, the use of a large number of digital phase shifters can be avoided when designing a large number of antenna systems to reduce manufacturing costs. However, the working principle of the Rotman lens is based on the beamforming mechanism in the time domain. Compared with the phase-controlled circuit design in the frequency domain, the Rotman lens circuit often has the problem of huge structure size.

The present invention provides an antenna device based on an improved Rotman lens, which can significantly reduce the size of the cavity of the Rotman lens.

An antenna device based on an improved Rotman lens of the present invention includes a dielectric substrate and a conductor layer. The conductor layer is arranged on the surface of the dielectric substrate, and the conductor layer includes an input port array, an output port array and a cavity. The cavity connects the input port array and the output port array and includes a reflection structure. In design, the axis of the reflection structure will be regarded as the symmetry axis of the output port array and the virtual output port array. The virtual output port array corresponds to the traditional Roth The output port array of the Mann lens.

In an embodiment of the present invention, the first vertical line of the input port array is perpendicular to the second vertical line of the output port array.

In an embodiment of the present invention, the first included angle between the first vertical line of the input port array and the normal line of the reflective structure is 45 degrees, and the second vertical line of the output port array and the normal line of the reflective structure The second angle between them is 45 degrees.

In an embodiment of the present invention, the aforementioned conductive layer further includes dummy ports. The dummy port is connected to the cavity, wherein the first acute angle between the first vertical line of the dummy port and the reflective structure is smaller than the second acute angle between the second vertical line of the output ports of the output port array and the reflective structure.

In an embodiment of the present invention, the aforementioned conductor layer further includes a tapered line transformer. The tapered line converter connects the input port in the input port array or the output port in the output port array to the cavity.

In an embodiment of the present invention, the above-mentioned tapered line converter includes a first part directly connected to the input port or output port and a second part directly connected to the cavity Bit, the impedance of the first part is 50 ohms.

In an embodiment of the present invention, the aforementioned antenna device further includes a ground layer. The ground layer is provided on the second surface of the dielectric substrate opposite to the surface.

In an embodiment of the present invention, the aforementioned conductor layer is electrically coupled to the ground layer through the through hole, so that the reflective structure meets the boundary condition of total reflection.

In an embodiment of the present invention, the wavelength of the input signal of the aforementioned antenna device is configured so that the reflective structure meets the boundary condition of total reflection.

In an embodiment of the present invention, the aforementioned conductor layer is one of a metal waveguide and a printed circuit.

Based on the above, the antenna device of the present invention can use the reflective structure to change the path between the input port array and the output port array, thereby reducing the size of the Rotman lens.

1: Rotman lens

2: antenna array

3: line

10.310: Input port array

11, 12, 13, 14, 311, 312, 313, 314: input port

20, 330: output port array

21, 22, 23, 24, 25, 26, 331, 332, 333, 334, 335, 336: output port

30, 40: dummy port array

50, 350: cavity

100: Antenna device

210: Conductor layer

220: Dielectric substrate

230: Ground layer

240: Through hole

320: Virtual output port array

321, 322, 323, 324, 325, 326: virtual output port

340: Dummy Port

351: Virtual Cavity

360: reflective structure

600: gradient line converter

610: The first part of the gradient line converter

620: The second part of the gradient line converter

700, 800, 1000, 1100: perpendicular

900: Normal

θ1, θ2: included angle

θ3, θ4: acute angle

Figure 1 shows a schematic diagram of a Rotman lens and an antenna array.

Figure 2 shows a top view of a Rotman lens.

FIG. 3 illustrates a side view of an antenna device based on an improved Rotman lens according to an embodiment of the present invention.

FIG. 4 shows a top view of a conductive layer according to an embodiment of the present invention.

FIG. 5A is a schematic diagram showing the performance of the antenna device based on Rotman lens.

5B is a schematic diagram illustrating the performance of an antenna device based on an improved Rotman lens according to an embodiment of the present invention.

Fig. 6 illustrates a schematic diagram of a gradient line converter of a Rotman lens according to an embodiment of the present invention.

FIG. 1 shows a schematic diagram of a Rotman lens 1 and an antenna array 2. The Rotman lens 1 includes an input port array 10, an output port array 20 and a cavity 50. The output port array 20 is electrically coupled to the antenna array 2 through a plurality of lines 3, where the plurality of lines 3 are, for example, microstrip transmission lines or coaxial transmission lines. The length of each of the multiple lines 3 needs to be calculated according to Rotman's formula, rather than equal lengths. The beamforming mechanism of the Rotman lens 1 is shown in Fig. 1. When an input signal is input through one of the input ports in the input port array 10, the input signal enters the cavity 50 and propagates around in a form similar to a point wave source. The path length between the input port and each output port of the output port array 20 is not the same. This feature makes the signal received by each output port of the output port array 20 have a different phase. Then, when the output signal output by each output port of the output port array 20 passes through the multiple circuits 3 designed based on Rotman's formula, the phase of each output signal can be adjusted by the multiple circuits 3 to stimulate The weight of each antenna of the antenna array 2 is such that the energy radiated by the antenna array 2 can be focused in a specific direction, thereby achieving the effect of beamforming.

FIG. 2 shows a top view of the Rotman lens 1. As mentioned above, the Rotman lens 1 may include an input port array 10 having input ports (ie: input ports 11, 12, 13 and 14) and a plurality of output ports (ie: output ports 21, 22, 23, 24). , 25 And 26) the output port array 20. In addition, the Rotman lens 1 may further include a dummy port array 30 and a dummy port array 40 each having a plurality of dummy ports. The dummy port array 30 or the dummy port array 40 is used to absorb the energy propagated to both sides of the Rotman lens 1 to prevent the signal from being reflected multiple times in the cavity 50 to form a multipath signal, thereby reducing the effect of multiple signal paths on the antenna array 2 The influence of the weight of each antenna.

In addition, the Rotman lens 1 is designed based on the principle of true time delay. Therefore, the ratio of the propagation path length of the signal in the cavity 50 of the Rotman lens 1 to the wavelength of the signal will increase with the operating frequency. This feature allows the phase of the output of the Rotman lens 1 to be adjusted automatically as the operating frequency changes. Therefore, the beamforming signal generated by the modified Rotman lens 1 will not shift with the change of the operating frequency, and can always remain in a fixed direction.

It can be seen from FIG. 1 that the input port array 10 and the output port array 20 are respectively disposed at both ends of the cavity 50 of the Rotman lens 1, and the cavity 50 needs to be additionally provided with a dummy port array 30 and a dummy port array 40. Therefore, the Rotman lens 1 will occupy a considerable area. As electronic products on the market gradually move towards miniaturization, the application scenarios of the Rotman lens 1 will gradually be limited. In response to this, the present invention provides an antenna device based on an improved Rotman lens, which can reduce the size of the Rotman lens, thereby reducing the size of the antenna device.

FIG. 3 illustrates a side view of an antenna device 100 based on an improved Rotman lens according to an embodiment of the present invention. The antenna device 100 may include a conductive layer 210, a dielectric substrate 220, and a ground layer 230, wherein the conductive layer 210 is disposed on the dielectric substrate 220 The ground layer 230 is disposed on the other surface of the dielectric substrate 220. The conductor layer 210 is, for example, a metal waveguide (metal waveguide) or a printed circuit (printed circuit), and the present invention is not limited thereto. In this embodiment, the conductor layer 210 is an improved Rotman lens.

FIG. 4 shows a top view of the conductive layer 210 according to an embodiment of the present invention. The conductor layer 210 may include an input port array 310, an output port array 330, a dummy port 340, and a cavity 350. The input port array 310 may include input ports 311, 312, 313, and 314. The output port array 330 may include output ports 331, 332, 333, 334, 335, and 336.

The cavity 350 is connected to the input port array 310 and the output port array 330, and the cavity 350 includes a reflective structure 360.

FIG. 4 also shows the virtual cavity 351 and the virtual output port array 320 to facilitate the explanation of the principle of the conductor layer 210. The virtual output port array 320 corresponds to the output port array 20 of the Rotman lens 1 shown in FIG. 2, and includes virtual output ports 321, 322, 323, 324, 325, and 326, and the virtual cavity 351 corresponds to the output port array 20 shown in FIG. The cavity 50 of the Rotman lens 1 is shown. In order to reduce the area of the Rotman lens 1 shown in FIG. 2, a reflection structure 360 is provided in the cavity 50 of the Rotman lens 1 shown in FIG. 2 of the present invention. The reflection structure 360 divides the cavity 350 from the cavity 50, and the reflection structure 360 forms the symmetry axis of the output port array 330 and the virtual output port array 320. The vertical line 700 of the input port array 310 is perpendicular to the vertical line 800 of the output port array 330, the angle θ1 (that is, the incident angle) between the vertical line 700 and the normal 900 of the reflective structure 360 is 45 degrees, and the vertical line 800 is perpendicular to The included angle θ2 (ie, the reflection angle) between the normal lines 900 of the reflective structure 360 is 45 degrees.

The input signal of the antenna device 100 or the reflection structure 360 needs to be adjusted so that the reflection structure 360 meets the boundary condition of total reflection. For example, the wavelength of the input signal of the antenna device 100 can be configured so that the reflective structure 360 meets the boundary condition of total reflection. For another example, a via 240 as shown in FIG. 3 can be provided between the conductive layer 210 and the ground layer 230. The conductive layer 210 can be electrically coupled to the ground layer 230 through the via 240, so that the reflective structure 360 meets the boundary condition of total reflection.

When an input signal is sent from the input port array 310, the path length of the input signal transmitted through the virtual cavity 351 without the reflection structure 360 to the virtual output port array 320 will be the same as the input signal reflected by the reflection structure 360 and passed through the cavity. The length of the path from the body 350 to the output port array 330 is the same. For example, if the virtual output port 321 in the virtual output port array 320 corresponds to the output port 331 in the output port array 330, the path length between the input port 311 and the virtual output port 321 in the input port array 310 will be the same The length of the path between the input port 311 and the output port 331.

In an embodiment, the conductive layer 210 further includes a dummy port 340. The dummy port 340 is connected to the cavity 350, wherein the acute angle θ3 between the vertical line 1000 of the dummy port 340 and the reflective structure 360 is smaller than the acute angle between the vertical line of any output port of the output port array 330 and the reflective structure 360. For example, the acute angle θ3 between the vertical line 1000 of the dummy port 340 and the reflective structure 360 is smaller than the acute angle θ4 between the vertical line 1100 of the output port 336 of the output port array 330 and the reflective structure 360. The dummy port 340 can absorb most of the reflected signal in the cavity 350. Compared with the Rotman lens 1 shown in FIG. 2, the conductor layer 210 only needs to provide a single dummy port 340 to achieve the same effect as the Rotman lens 1 Similar effects of the dummy port arrays 30 and 40 are shown in Figures 5A and 5B.

FIG. 5A shows a schematic diagram of the performance of the antenna device based on the Rotman lens 1. 5B is a schematic diagram illustrating the performance of the antenna device 100 based on the modified Rotman lens according to an embodiment of the present invention. It can be seen from FIGS. 5A and 5B that the peak position (about 18 degrees) of the gain of the input port 11 and the corresponding input port 311 are similar. Similarly, the peak position of the gain of the input port 12 and the corresponding input port 312 (approximately 6 degrees) is close, the peak position of the gain of the input port 13 and the corresponding input port 313 (approximately -6 degrees) are close, and the input port 14 is close to the peak position (approximately -18 degrees) of the gain of the corresponding input port 314. In other words, the conductor layer 210 shown in FIG. 4 can use a smaller area to achieve a similar effect to the Rotman lens 1 shown in FIG. 2.

Each input port of the input port array 310 and each output port of the output port array 330 may be connected to the cavity 350 through tapered-line transformers having a tapered structure. FIG. 6 illustrates a schematic diagram of a gradient line converter 600 of a Rotman lens according to an embodiment of the present invention. Taking the input port 313 as an example, the input port 313 can be connected to the cavity 350 through the tapered line converter 600. The tapered line converter 600 may include a first part 610 directly connected to the input port or output port and a second part 620 directly connected to the cavity. The impedance of the first part 610 is, for example, 50 ohms.

In summary, the present invention provides an antenna device based on an improved Rotman lens, which can significantly reduce the size of the cavity of the Rotman lens. The Rotman lens of the present invention includes a reflective structure to divert the path between the input port array and the output port array, thereby reducing the length of the cavity by increasing the width of the cavity. Compared with a general Rotman lens, the Rotman lens of the present invention can minimize the number of dummy ports, and It effectively reduces the size of the Rotman lens while maintaining the transmission efficiency. In addition, the conductor layer of the antenna device can be electrically connected to the ground layer through the through hole, so that the reflective structure in the cavity of the Rotman lens meets the boundary condition of total reflection, thereby reducing the loss of signal transmission energy.

210: Conductor layer

310: Input port array

311, 312, 313, 314: input port

320: Virtual output port array

321, 322, 323, 324, 325, 326: virtual output port

330: output port array

331, 332, 333, 334, 335, 336: output port

340: Dummy Port

350: Cavity

351: Virtual Cavity

360: reflective structure

700, 800, 1000, 1100: perpendicular

900: Normal

θ1, θ2: included angle

θ3, θ4: acute angle

Claims (8)

An antenna device based on an improved Rotman lens, comprising: a dielectric substrate; and a conductor layer disposed on the surface of the dielectric substrate, wherein the conductor layer includes: an input port array; an output port array; and a cavity , Connecting the input port array and the output port array and including a reflective structure; wherein the first vertical line of the input port array is perpendicular to the second vertical line of the output port array; wherein the first vertical line of the input port array The first included angle between a vertical line and the normal line of the reflective structure is 45 degrees, and the second included angle between the second vertical line of the output port array and the normal line of the reflective structure is 45 degrees. degree. The antenna device according to claim 1, wherein the conductor layer further includes: a dummy port connected to the cavity, wherein the first vertical line between the first vertical line of the dummy port and the reflective structure The acute angle is smaller than the second acute angle between the second vertical line of the output ports of the output port array and the reflective structure. According to the antenna device described in claim 1, wherein the conductor layer further includes: a tapered line converter, which connects the input port in the input port array or the output port in the output port array to the Cavity. The antenna device according to item 3 of the scope of patent application, wherein the tapered line converter includes a first part directly connected to the input port or the output port and a second part directly connected to the cavity, The impedance of the first part is 50 ohms. The antenna device described in item 1 of the scope of patent application further includes: a ground layer disposed on a second surface of the dielectric substrate opposite to the surface. According to the antenna device described in item 5 of the scope of patent application, the conductor layer is electrically coupled to the ground layer through a through hole, so that the reflective structure meets the boundary condition of total reflection. The antenna device according to the first item of the scope of patent application, wherein the wavelength of the input signal of the antenna device is configured so that the reflection structure meets the boundary condition of total reflection. The antenna device according to the first item of the patent application, wherein the conductor layer is one of a metal waveguide and a printed circuit.

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