Antenna system

An antenna system for receiving and transmitting wireless signals includes a first complex antenna including a first dielectric layer, a first metal grounding sheet, first to fourth antenna arrays and a first transmission line device for transmitting radio-frequency signals to the first to fourth antenna arrays, a second complex antenna including a second dielectric layer, a second metal grounding sheet, fifth to eighth antenna arrays and a second transmission line device for transmitting radio-frequency signals to the fifth to eighth antenna arrays, and a feeding device, for alternatively outputting radio-frequency signals to the first complex antenna and the second complex antenna via the first and second transmission line devices, and switching phases of the radio-frequency signals outputted to the first to eighth antenna arrays.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an antenna system, and more particularly, to an antenna system with adaptive beam alignment capability, high antenna gain value and beam coverage rate, low cost and small volume.

2. Description of the Prior Art

An electronic product with wireless communication functions emits or receives radio waves via an antenna to transmit or transfer wireless signals to access a wireless network. With the advance of wireless communication technology, the demand for transmission capacity and wireless network performance also rises. Therefore, many wireless communication systems have supported Multi-input Multi-output (MIMO) communication technology, which can greatly increase the data throughput and transmission distance of the system without increasing the bandwidth or total transmit power expenditure, so as to effectively enhance the spectrum efficiency and transmission rate of the wireless communication system and improve communication quality.

There are many types of antennas that support MIMO communication technology. A panel-type antenna has a less complex structure and is rather inexpensive. However, the beamwidth of the panel-type antenna in the horizontal plane is narrow, meaning that the beam coverage rate is low, such that it is hard to mount the panel-type antenna precisely. Moreover, the panel-type antenna lacks adaptive beam alignment capabilities. If a driving motor is applied to align the panel-type antenna in the direction with the best signal receiving quality, the drawbacks of the panel-type antenna may be compensated. However, adding the driving motor increases the manufacturing cost, involves restrictions on the installation, and is unable to meet the trend for compact electronic products. Although a complex antenna of cylindrical radome requires no driving motor, it has a larger volume and lower antenna gain value.

Therefore, how to increase the antenna gain value and the beam coverage rate under the limited volume and cost while taking adaptive beam alignment capability into account has become a goal in the industry.

SUMMARY OF THE INVENTION

Therefore, the present application primarily provides an antenna system with adaptive beam alignment capability, high antenna gain value and beam coverage rate, low cost and smaller size.

An antenna system for receiving and transmitting wireless signals includes a first complex antenna, a second complex antenna, and a feeding device. The first complex antenna includes a first dielectric layer; a first metal grounding sheet, fixed to the first dielectric layer, and spaced apart from the first dielectric layer by a first gap to form a first air dielectric layer; a first, a second, a third and a fourth antenna arrays, arranged in a 4×4 array manner, fixed to the first metal grounding sheet, and spaced apart from the first metal grounding sheet by a second gap to form a second air dielectric layer; and a first transmission line device, formed on a side of the first dielectric layer facing the first metal grounding sheet, for transmitting radio-frequency signals to the first to fourth antenna arrays. The second complex antenna fixed with respect to the first complex antenna at an included angle includes a second dielectric layer; a second metal grounding sheet, fixed to the second dielectric layer, and spaced apart from the second dielectric layer by a third gap to form a third air dielectric layer; a fifth, a sixth, a seventh and an eighth antenna arrays, arranged in the 4×4 array manner, fixed to the second metal grounding sheet, and spaced apart from the second metal grounding sheet by a fourth gap to form a fourth air dielectric layer; and a second transmission line device, formed on a side of the second dielectric layer facing the second metal grounding sheet, for transmitting radio-frequency signals to the fifth to eighth antenna arrays. The feeding device, coupled between the first transmission line device and the second transmission line device, wherein the feeding device is configured for alternately outputting radio-frequency signals to the first complex antenna and the second complex antenna so as to emit wireless signals via the first complex antenna and the second complex antenna, and for switching phases of radio-frequency signals outputted to the first to eighth antenna arrays so as to change characteristics of beam generated by the first to eighth antenna arrays.

DETAILED DESCRIPTION

Please refer toFIG. 1A,FIG. 1BandFIG. 1C.FIG. 1Ais a perspective view diagram of an antenna system10according to an embodiment of the present invention.FIG. 1Bis a top view diagram of the antenna system10.FIG. 1Cis a rear side view diagram of the antenna system10. An x-y-z coordinate system is shown inFIGS. 1A, 1B, 1Cand subsequent figures to present the spatial relationship of the antenna system10. The antenna system10is utilized to receive and transmit wireless signals, and is capable of providing a 4×4 MIMO function. The antenna system10includes a first complex antenna12, a second complex antenna14, and a feeding device16(not shown inFIGS. 1A, 1B and 1C). The first complex antenna12includes a dielectric layer120, a metal grounding sheet122, a transmission line device124, a reflection sheet126and antenna arrays ANT_1to ANT_4. The second complex antenna14includes a dielectric layer140, a metal grounding sheet142, a transmission line device144, a reflection sheet146and antenna arrays ANT_5to ANT_8. The first complex antenna12and the second complex antenna14are fixed on one side, and an included angle therebetween is ANG. In other words, the first complex antenna12is fixed with respect to the second complex antenna14at the included angle ANG. The included angle ANG is in a range of 70 degrees to 150 degrees, and is primarily related to gain value and beam coverage rate of the antenna system10. The included angle ANG may be 120 degrees. If the included angle ANG increases, the gain value may increase but the beam coverage rate may decrease. Conversely, if the included angle ANG is reduced, the gain value decrease but the beam coverage rate may be improved. Each of the antenna arrays ANT_1to ANT_8is a 1×2 antenna array. Namely, each of the antenna arrays ANT_1to ANT_8includes two unit antennas U arranged vertically (for example, from top to bottom, or from bottom to top), and the two unit antennas U have identical structures and sizes.

The structure of the first complex antenna12is similar to that of the second complex antenna14, wherein the reflection sheets126,146, the dielectric layers120,140, the transmission line devices124,144, the metal grounding sheets122,142and the antenna arrays ANT_1to ANT_8are sequentially arranged from bottom to top (from back surface to top surface). The antenna arrays ANT_1to ANT_8are arranged in a 4×4 array manner (i.e., a 4 by 4 array having 4 rows and 4 columns) and are fixed to the metal grounding sheets122,142. The detailed structures of the first complex antenna12and the second complex antenna14are described as follows by taking the antenna array ANT_1of the first complex antenna12as an example. Please refer toFIGS. 2A to 2D.FIG. 2Ais a cross-section view diagram of the antenna array ANT_1.FIG. 2Bis a schematic diagram of the antenna array ANT_1in appearance.FIG. 2Cis a diagram of the antenna array ANT_1without the unit antennas U.FIG. 2Dis a diagram of the antenna array ANT_1without the unit antennas U and the metal grounding sheet122. In the antenna system10, each of the unit antennas U is a dual-polarized microstrip antenna; that is to say, it is able to generate vertically polarized radiation pattern and horizontally polarized radiation pattern. In this case, a composite feeding approach (that is, direct feeding and coupling feeding are used to transmit radio-frequency signals to the unit antennas U) is adopted to ensure reliable operation of the unit antenna U. As shown inFIGS. 2A to 2D, the transmission line device124is formed on/above the dielectric layer120. AlthoughFIGS. 2B to 2Dmerely show a transmission line module TXM corresponding to the antenna array ANT_1, the transmission line device124includes four transmission line modules TXM, which correspond to the antenna arrays ANT_1to ANT_4respectively. Each of the transmission line modules TXM is constituted by transmission lines TL_1, TL_2. Each of the transmission line modules TXM is electrically connected to the feeding device16(not shown inFIGS. 2A to 2D), and is configured to feed radio-frequency signals to the unit antenna U. The transmission line TL_1corresponds to vertically polarized operation. Instead of electrically connected to the unit antenna U, the transmission line TL_1together with a slot SL of the metal grounding sheet122(as shown inFIG. 2C) transmit radio-frequency signals to the unit antenna U by means of coupling feeding. The transmission line TL_2corresponds to horizontally polarized operation. The transmission line TL_2has a feeding element PB electrically connected to the unit antenna U (as shown inFIGS. 2A, 2C, and 2D) in order to transmit radio-frequency signals to the unit antenna U by means of direct feeding. The metal grounding sheet122further includes a slot corresponding to the feeding element PB. The feeding element PB penetrates the metal grounding sheet122by passing through the slot. In addition, as shown inFIG. 2A, the metal grounding sheets122is spaced apart from the dielectric layer120by a gap G1to form an air dielectric layer ARL_1, which aims to reduce energy loss of transmission line. The metal grounding sheets122is spaced apart from the unit antenna U by a gap G2to form an air dielectric layer ARL_2, which also aims to reduce energy loss of transmission line. Furthermore, please refer toFIGS. 3A and 3B.FIGS. 3A and 3Bare schematic diagrams illustrating locally enlarged views from different angles of the first complex antenna12, whereby the relative relationship of the components may be clarified.

Next, please refer toFIG. 4, which is a functional block diagram of the feeding device16in the antenna system10. The feeding device16, which is electrically connected to the transmission line devices124and144, is able to alternately output radio-frequency signals to the first complex antenna12and the second complex antenna14via the transmission line devices124and144. The feeding device16is able to have only one complex antenna being turned on and the other complex antenna being turned off at a time. Furthermore, the four antenna arrays in the same complex antenna are turned on simultaneously or turned off simultaneously. Because the unit antenna U is a dual-polarized antenna, and because of mechanism of the feeding device16, the antenna system10is able to provide 4×4 MIMO functions. Besides, the feeding device16is able to switch phases of radio-frequency signals outputted to the antenna arrays ANT_1to ANT_8so as to change characteristics of beam generated by the antenna arrays ANT_1to ANT_8, thereby increasing beam coverage on the horizontal plane (i.e., the x-y plane).

Specifically, the feeding device16includes feeding modules400,402,404, and406. Each of the feeding modules400,402,404,406corresponds to two horizontally adjacent antenna arrays of the antenna arrays ANT_1to ANT_8. That is to say, the feeding module400outputs radio-frequency signals to the antenna arrays ANT_1and ANT_2, which are horizontally adjacent to each other, via (two transmission line modules TXM of) the transmission line device124. The feeding module402outputs radio-frequency signals to the antenna arrays ANT_3and ANT_4, which are horizontally adjacent to each other, via (two transmission line modules TXM of) the transmission line device124. The feeding module404outputs radio-frequency signals to the antenna arrays ANT_5and ANT_6, which are horizontally adjacent to each other, via (two transmission line modules TXM of) the transmission line device144. The feeding module406outputs radio-frequency signals to the antenna arrays ANT_7and ANT_8, which are horizontally adjacent to each other, via (two transmission line modules TXM of) the transmission line device144. In this case, the horizontally adjacent antenna arrays ANT_1, ANT_2may form a first group of beamforming, the horizontally adjacent antenna arrays ANT_3, ANT_4may form a second group of beamforming, the horizontally adjacent antenna arrays ANT_5, ANT_6may form a third group of beamforming, and horizontally adjacent antenna arrays ANT_7, ANT_8may form a fourth group of beamforming, thereby increasing beam coverage. Moreover, the feeding modules400,402,404,406is able to switch phases of radio-frequency signals outputted to the antenna arrays ANT_1to ANT_8so as to change characteristics of beam generated by the antenna arrays ANT_1to ANT_8, thereby increasing beam coverage on the horizontal plane.

Structures of the feeding modules400,402,404, and406are identical, and are detailed as follows by taking the feeding module400as an example. Please refer toFIG. 5A, which is a functional block diagram of the feeding module400according to an embodiment of the present invention. In this embodiment, the feeding module400includes a power divider (or power splitter)500and phase shifters502,504. The power divider500is a one-to-two power divider; in other words, the power divider500includes an input terminal and two output terminals. The power divider500receives signals of a signal source from the input terminal and distributes radio-frequency signals generated by the signal source to the two output terminals. The radio-frequency signals are transmitted to the phase shifters502,504, and then output to the horizontally adjacent antenna arrays ANT_1, ANT_2via (the two transmission line modules TXM of) the transmission line device124. To achieve only one complex antenna being turned on at a time, in an embodiment, a switch circuit may be added between the signal source and the power divider500, and connection between the signal source and the power divider500is controlled by the switch circuit. However, the present invention is not limited thereto, and any manner (in which only one complex antenna is turned on at a time while the other complex antenna is turned off) may be adopted in the present invention. In addition, the signal source merely serves to illustrate output signals of a radio-frequency processing circuit, and signal sources connected to the feeding modules400,402,404,406may be integrated into the same signal source or a plurality of signal sources. The phase shifters502,504may be switched between different phase shift modes so as to switch phases of radio-frequency signals outputted to transmission line module TXM; accordingly, radio-frequency signals outputted from the power divider500may be transmitted to the unit antennas U in a plurality of phase states. In a phase state, there is no phase difference between radio-frequency signals outputted by the phase shifters502,504. In the other phase states, there may be phase difference(s) between radio-frequency signals outputted by the phase shifters502,504. In this way, by means of the different phase states, radio-frequency signals received by the antenna arrays ANT_1to ANT_8may have no phase difference or have (different) phase difference(s), and may form leftward-bent, rightward-bent, or undeflected beams in horizontal plane, thereby increasing beam coverage on the horizontal plane.

For example, suppose that the phase shifter502has a phase shift mode of 0 degrees and a phase shift mode of 110 degrees, and suppose that radio-frequency signals outputted from the phase shifter502is transmitted to the antenna array ANT_1via the transmission line module TXM. Similarly, suppose that the phase shifter504has a phase shift mode of 0 degrees and a phase shift mode of 110 degrees, and suppose that radio-frequency signals outputted from the phase shifter504is transmitted to the antenna array ANT_2via the transmission line module TXM. In a first phase state, both the phase shifters502,504are operated in the 0 degree phase shift mode; that is to say, radio-frequency signals outputted from the phase shifters502,504have no phase difference, such that radio-frequency signals received by the antenna arrays ANT_1, ANT_2are continuous phase inputs with 0 degree difference. In a second phase state, the phase shifter502is operated in the 0 degree phase shift mode, and the phase shifter504is operated in the 110 degree phase shift mode. Therefore, radio-frequency signals received by the antenna arrays ANT_1, ANT_2are continuous phase inputs with +110 degree difference. In a third phase state, the phase shifter502is operated in the 110 degree phase shift mode, and the phase shifter504is operated in the 0 degree phase shift mode. Therefore, radio-frequency signals received by the antenna arrays ANT_1, ANT_2are continuous phase inputs with −110 degree difference. In other words, in the first phase state, the second phase state, and the third phase state, input phase values of the antenna arrays ANT_1, ANT_2are respectively 0 degree difference continuous input of undeflected beam, +110 degree difference continuous input of rightward-bent beam (or rightward deflecting beam), and −110 degree difference continuous input of leftward-bent beam, such that three types of beams are formed to increase beam coverage on the horizontal plane. Therefore, as long as the phase shift modes of the phase shifter502are appropriately switched or adjusted, the antenna arrays ANT_1, ANT_2may have phase inputs of different angles, thereby generating different beams to increase beam coverage on the horizontal plane.

To achieve the phase shifter502of two phase shift modes, in an embodiment, a combination of a switch and a delay unit may be utilized. For example, please refer toFIG. 5B, which is a schematic diagram of an embodiment of the phase shifter502according to an embodiment of the present invention. In this embodiment, the phase shifter502includes a switch508, a delay unit510, and an output line512. The switch508is coupled to the power divider500. The switch508is able to output radio-frequency signals provided by the power divider500to the delay unit510or the output line512according to different phase states. In this embodiment, the delay unit510corresponds to the 110 degree phase shift mode, and phases of radio-frequency signals may be delayed 110 degrees by the delay unit510. The output line512corresponds to the 0 degree phase shift mode, meaning that phases of radio-frequency signals are unchanged. In this way, it is possible to have a phase difference of 110 degrees or 0 degrees with the switch508, which switches the output of radio-frequency signals to either the delay unit510or the output line512.

As can be seen above, there is no need for the antenna system10to form a cyclic or an annular structure so that the cost and the size may be decreased, the external form or appearance is close to a flat shape (or a sheet-like shape), and the antenna system10is suitable for hanging on a wall. In terms of antenna structure, the unit antennas U are dual-polarized microstrip antennas, and a composite feeding approach is adopted to implement the direct feeding and the coupling feeding. Accordingly, vertically polarized antenna characteristics and horizontally polarized antenna characteristics, which include resonance bandwidth and front-to-back (F/B) ratio, are effectively improved. Furthermore, any two horizontally adjacent antenna arrays of the antenna arrays ANT_1to ANT_8may be used together to perform beamforming so that two sets of beamforming antennas are provided in one complex antenna. The feeding device16turns on merely one complex antenna at a time and turns off the other complex antenna. Therefore, beam coverage of the antenna system on the horizontal plane may increase by means of beam switching, thereby achieving half-plane beam coverage and offering 4×4 MIMO functions. Besides, the feeding device16alters phase arrangement(s) of radio-frequency signals received by the antenna arrays ANT_1to ANT_8to change beam direction during/after beamforming, thereby increasing beam coverage of each complex antenna on the horizontal plane.

In order to verify functionality of the antenna system10, an HFSS simulation software is first applied to calculate and obtain a schematic diagram of resonance characteristics and isolation of the antenna array ANT_1in the antenna system10as shown inFIG. 6, wherein the resonance characteristics (S-parameter) of the vertically and horizontally polarized antennas are presented by a thick solid curve and a thin solid curve respectively. It is shown that S11of the antenna array ANT_1is less than −10.9 dB and meet frequency band requirements of band48in the LTE wireless communication system—for example, region B48shown inFIG. 6. Meanwhile, the isolation (S-parameter) between the vertically polarized antenna and the horizontally polarized antenna inside the antenna array ANT_1is presented by a dashed curve inFIG. 6. It is shown that the isolation between the vertically polarized antenna and the horizontally polarized antenna is greater than 24.2 dB. The other antenna arrays have similar characteristics and hence are not detailed redundantly.

FIG. 7Ais a gain value field pattern of the vertically polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the vertical plane (i.e., the x-z plane) after beam combination of the two vertically polarized antennas with 0 degree phase difference, wherein the gain value field patterns corresponding to different polarization directions on the vertical plane—that is, the gain value field patterns of common polarization (Co-pol) and cross polarization (Cx-pol)—are presented by a dashed curve and a solid curve respectively. It is shown that 3 dB beamwidth is substantially 41 degrees, which meets wireless communication requirements.FIG. 7Bis a gain value field pattern of the horizontally polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the vertical plane after beam combination, wherein the gain value field patterns corresponding to different polarization directions on the vertical plane—that is, the gain value field patterns of Co-pol and Cx-pol—are presented by a solid curve and a dashed curve respectively. It is shown that 3 dB beamwidth is substantially 43 degrees, which also meets wireless communication requirements. In other words, the vertically polarized antennas and the horizontally polarized antennas of the antenna arrays ANT_1, ANT_2have sufficient beamwidth on the vertical plane after beam combination.

As set forth above, the feeding device16may change the phase arrangement(s) of radio-frequency signals received by the antenna arrays ANT_1to ANT_8, and hence leftward-bent, rightward-bent, or undeflected beams are generated on the horizontal plane, thereby forming three beams to increase beam coverage. First, when the antenna arrays ANT_1, ANT_2are required to output an undeflected beam, the phase shifters502,504inFIG. 5Aare operated in the 0 degree phase shift mode, the corresponding gain value field patterns on the horizontal plane are shown inFIGS. 8A and 8B.FIG. 8Ais a gain value field pattern of the vertically polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the horizontal plane after beam combination, wherein the gain value field patterns corresponding to different polarization directions on the horizontal plane—that is, the gain value field patterns of Co-pol and Cx-pol—are presented by a dashed curve and a solid curve respectively. It is shown that 3 dB beamwidth is substantially 44 degrees.FIG. 8Bis a gain value field pattern of the horizontally polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the horizontal plane after beam combination, wherein the gain value field patterns corresponding to different polarization directions on the horizontal plane—that is, the gain value field patterns of Co-pol and Cx-pol—are presented by a solid curve and a dashed curve respectively. It is shown that 3 dB beamwidth is substantially 38 degrees. As shown inFIGS. 8A and 8B, 3 dB beamwidths of the antenna arrays ANT_1, ANT_2are less than 60 degrees after beam combination, which fails to meet specific wireless communication requirements (for example, 120 degrees in beam coverage).

Next, when the phase shifter502is operated in the 0 degree phase shift mode and the phase shifter504is operated in the 110 degree phase shift mode, radio-frequency signals received by the antenna arrays ANT_1, ANT_2are continuous phase inputs with +110 degree difference, and the corresponding gain value field patterns on the horizontal plane are shown inFIGS. 9A and 9B.FIG. 9Ais a gain value field pattern of the vertically polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the horizontal plane after beam combination, wherein the gain value field patterns corresponding to different polarization directions on the horizontal plane—that is, the gain value field patterns of Co-pol and Cx-pol—are presented by a dashed curve and a solid curve respectively.FIG. 9Bis a gain value field pattern of the horizontally polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the horizontal plane after beam combination, wherein the gain value field patterns corresponding to different polarization directions on the horizontal plane—that is, the gain value field patterns of Co-pol and Cx-pol—are presented by a solid curve and a dashed curve respectively. As shown inFIGS. 9A and 9B, when the phase shifter502is operated in the 0 degree phase shift mode and the phase shifter504is operated in the 110 degree phase shift mode, field patterns deflected to the right may be formed on the horizontal plane after beam combination of the antenna arrays ANT_1, ANT_2.

Finally, when the phase shifter502is operated in the 110 degree phase shift mode and the phase shifter504is operated in the 0 degree phase shift mode, radio-frequency signals received by the antenna arrays ANT_1, ANT_2are continuous phase inputs with −110 degree difference, and the corresponding gain value field patterns on the horizontal plane are shown inFIGS. 10A and 10B.FIG. 10Ais a gain value field pattern of the vertically polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the horizontal plane after beam combination, wherein the gain value field patterns corresponding to different polarization directions on the horizontal plane—that is, the gain value field patterns of Co-pol and Cx-pol—are presented by a dashed curve and a solid curve respectively.FIG. 10Bis a gain value field pattern of the horizontally polarized antennas of the antenna arrays ANT_1, ANT_2at 3550 MHz on the horizontal plane after beam combination, wherein the gain value field patterns corresponding to different polarization directions on the horizontal plane—that is, the gain value field patterns of Co-pol and Cx-pol—are presented by a solid curve and a dashed curve respectively. As shown inFIGS. 10A and 10B, when the phase shifter502is operated in the 110 degree phase shift mode and the phase shifter504is operated in the 0 degree phase shift mode, field patterns deflected to the left may be formed on the horizontal plane after beam combination of the antenna arrays ANT_1, ANT_2.

According toFIGS. 8A to 10B, by adjusting the phase shift modes of the phase shifters502and504, three types of beams may be formed on the horizontal plane after beam combination of the antenna arrays ANT_1, ANT_2, and may be combined/merged into field pattern beam coverage as shown inFIGS. 11A and 11B.FIG. 11Ais a beam coverage diagram of the vertically polarized antennas of the antenna arrays ANT_1, ANT_2of the first complex antenna12and the vertically polarized antennas of the antenna arrays ANT_5, ANT_6of the second complex antenna14on the horizontal plane. Within beam coverage of 120 degrees, antenna gain value is substantially in a range of 11.6 to 12.8 dBi, and its maximum value is close to 13 dBi.FIG. 11Bis a beam coverage diagram of the horizontally polarized antennas of the antenna arrays ANT_1, ANT_2of the first complex antenna12and the horizontally polarized antennas of the antenna arrays ANT_5, ANT_6of the second complex antenna14on the horizontal plane. Within beam coverage of 120 degrees, antenna gain value is substantially in a range of 11.2 to 12.7 dBi, and its maximum value is close to 13 dBi as well. Consequently, with the feeding device16, the antenna system10attains half-plane beam covered (or half-plane beam coverage), the beam coverage is at least 120 degrees, and antenna gain value is ensured.

The antenna system10is an exemplary embodiment of the present invention, and those skilled in the art may readily make different alternations and modifications. For example, the first complex antenna12and the second complex antenna14of the antenna system10may be mutually fixed because they are connected on one side; alternatively, a connection hinge connects the first complex antenna12and the second complex antenna14of the antenna system10; alternatively, the first complex antenna12and the second complex antenna14of the antenna system10may be secured on a base without electrical connection. In addition, the first complex antenna12and the second complex antenna14are relatively fixed according to a specific included angle ANG. Nevertheless, a dedicated mechanical design may allow the included angle ANG between the first complex antenna12and the second complex antenna14to vary within a range of tolerance to facilitate flexibility in signal transmission and reception and to ensure ease of disposition and facility of utilization, which is also within the scope of the present invention. In addition, the transmission line devices124and144are configured to transmit radio-frequency signals. Shapes, positions, extension lengths, and so on of the transmission lines TL_1and TL_2may be appropriately adjusted. Feeding approaches are not limited to the combination of direct feeding and coupling feeding. As long as antenna performance is maintained, it may adopt either entirely direct feeding or entirely coupling feeding. The dielectric layer120may be FR4, a plastic substrate, and the like, but not limited thereto. The reflection sheets126,146aim to reflect electromagnetic waves of back radiation so as to improve front-to-back ratio of antenna radiation pattern. Shapes, positions, materials, and so on of the reflection sheets126,146may be adjusted according to system requirements in different applications; alternatively, the reflection sheets126,146may be removed from the antenna system10. The gap G1between the grounding metal plate122and the dielectric layer120and the gap G2between the grounding metal plate122and the unit antenna U are used to form the air dielectric layers ARL_1and ARL_2so as to reduce energy loss of transmission line. The gaps G1and G2may be appropriately modified according to different applications. Moreover, the feeding device16turns on only one complex antenna at a time to achieve 4×4 MIMO functions, and alters the beam forming method by changing phase arrangement (s). The present invention is not limited thereto, and any method which can achieve the same function is suitable for the present invention.

In summary, the antenna system of the present invention has an appearance close to a sheet-like shape, occupies smaller volume (to be compact), can effectively improve gain value, isolation and operation bandwidth, can provide 4×4 MIMO functions, and can effectively improve beam coverage in vertical plane and in horizontal plane.