TWI489797B - Wireless transceiver, wireless communication system with mimo structure and method thereof - Google Patents

Description

Wireless transceiver, wireless communication system with multiple input and multiple output and method thereof

The present invention relates to a wireless communication system, and more particularly to a wireless communication system having multiple inputs and multiple outputs and a method thereof.

With the rapid development of mobile communications, the demand for communication services is increasing. How to effectively improve the efficiency of bandwidth usage and communication quality has become an important issue in communication systems. In the wireless communication system, according to the number of antennas of the receiver and the transmitter, it can be divided into a single input single output (SISO) system, a single input multiple output (SIMO) system, a multiple input single output (MISO) system, and multiple input and multiple output ( MIMO) system. In a SISO system, a transmitter includes an antenna to transmit an RF signal that is received by a single or multiple antennas in the receiver. When the receiver contains more than one antenna, the receiver will select one of them to receive the input signal. In a SIMO system, the receiver contains more than two antennas and more than two wireless channels. In a MIMO system, the transmitter and receiver individually contain more than two antennas and corresponding wireless channels. The transmitter utilizes spatial and temporal coding functions to process data in parallel and transmits multiple data signals based on multiple data streams with multiple antennas. After receiving the transmitted multiple data signals through multiple wireless channels, the receiver reacquires the data streams by using spatial and temporal decoding functions. Accordingly, MIMO systems provide higher transmission capacity and communication performance than single-input and/or single-out systems. In the wireless communication standard defined by the American Institute of Electrical and Electronics Engineers revised version 802.11n, which is modified by the American Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the standard uses the MIMO antenna structure as its core technology.

A MIMO system uses multiple transmit and receive antennas to provide multiple wireless channels. The plurality of transmit and receive antennas are designed to introduce diversity gain and array gain and to suppress interference generated during signal reception. In order to transmit maximum energy and power between the transmitting and receiving antennas, the transmitting antenna and the receiving antenna must have the same polarization direction to achieve matching between the antennas. Accordingly, it is necessary to propose a wireless communication system having a multi-input multi-output antenna and a method thereof to effectively improve the transmission efficiency of the system.

It is an object of the present invention to provide a wireless transceiver, a wireless communication system having multiple inputs and multiple outputs, and a method thereof.

One embodiment of the wireless transceiver of the present invention includes a first circularly polarized antenna and a first phase offset and power distribution circuit. The first phase offset and power distribution circuit is coupled to the first circularly polarized antenna.

One embodiment of the wireless communication system with multiple inputs and multiple outputs of the present invention includes a first transceiver and a second transceiver. The first transceiver device includes a first circularly polarized antenna and a first phase offset and power distribution circuit coupled to the first circularly polarized antenna. The second transceiver device includes a second circularly polarized antenna and a second phase offset and power distribution circuit coupled to the second circularly polarized antenna. The first circularly polarized antenna and the second circularly polarized antenna have the same circular polarization direction.

The method of the present invention for use in a multiple input multiple output wireless communication system includes the steps of: transmitting a first circularly polarized transmit signal to a first circularly polarized antenna at a first transceiver; and The first circularly polarized transmit signal is received by a second circularly polarized antenna to generate a first received signal. The first circularly polarized antenna and the second circularly polarized antenna have the same circular polarization direction.

1 shows a block diagram of a wireless transceiver 10 in accordance with an embodiment of the present invention. The wireless transceiver 10 includes a transceiver unit 12, a phase shift and power distribution circuit 14 and a circularly polarized antenna 16. The circularly polarized antenna 16 includes a vertical linearly polarized antenna 162 and a horizontally linearly polarized antenna 164. The vertical linearly polarized antenna 162 and the horizontal linearly polarized antenna 164 are oriented, that is, the direction in which they transmit or receive signals is 90 degrees from each other. The phase shifting and power distribution circuit 14 is coupled to the circularly polarized antenna 16 and configured to receive a radio frequency signal S ₁ output by the transceiver unit 12 and separate the radio frequency signal into two independent signals A ₁ and A ₂ , wherein A ₁ and A ₂ each have a power of half of the radio frequency signal S ₁ and a phase difference of 90 degrees from each other. The signals A ₁ and A _{2 are} then transmitted through the vertical linearly polarized antenna 162 and the horizontal linearly polarized antenna 164, respectively. The polarization direction of the circularly polarized antenna 16 can be obtained by adjusting the phase offset and the phase of the output signal of the power distribution circuit 14. In one embodiment, the phase shift and power distribution circuit 14 can be a quarter-wave delay circuit.

2 shows a block diagram of a wireless transceiver 20 in accordance with another embodiment of the present invention. The wireless transceiver 20 includes circularly polarized antennas 22, 24 and phase offset and power distribution circuits 26, 28. The circularly polarized antennas 22, 24 respectively comprise a vertical linearly polarized antenna and a horizontally linearly polarized antenna. The plurality of phase shift circuit 26, and power distribution lines coupled to the plurality of the circularly polarized antenna 22, which is provided to generate A _1, A _2, A ₃ and A signals having phase differences of 90 degrees respectively ₄ Transmitted through the vertical linearly polarized antennas and the horizontal linearly polarized antennas.

When designing the antenna configuration, according to the principle of polarization separation, when the polarization direction of the incident wave and the polarization direction of the receiving antenna are perpendicular to each other, the receiving antenna cannot receive the transmitted signal. Accordingly, the circular polarization direction of the circularly polarized antenna 22 is configured to be perpendicular to the circular polarization direction of the circularly polarized antenna 24, so that the two antennas located in the same wireless transceiver 20 do not receive signals transmitted from each other. . The polarization directions of the circularly polarized antennas can be obtained by adjusting the phases of the signals A ₁ , A ₂ , A ₃ and A ₄ as shown in the phase assignment table of FIG. 2 .

3 shows a block diagram of a wireless transceiver 30 in accordance with yet another embodiment of the present invention. The wireless transceiver 30 includes circularly polarized antennas 32, 34, a linearly polarized antenna 35, and phase offset and power distribution circuits 36,38. In contrast to Figures 1 and 2, the linearly polarized antenna 35 is configured to transmit or receive signals when the wireless transceiver 30 switches to the 802.11b mode.

4 shows a block diagram of a wireless communication system 40 having multiple inputs and multiple outputs in accordance with one embodiment of the present invention. The wireless communication system 40 includes a transceiver 42 and a transceiver 44. The transceiver 42, similar to FIG. 1, includes a circularly polarized antenna 426 and a phase offset and power distribution circuit 424 coupled to the circularly polarized antenna 426. The transceiver 44, similar to FIG. 1, includes a circularly polarized antenna 446 and a phase offset and power distribution circuit 444 coupled to the circularly polarized antenna 446. In the transceiver apparatus 42, a radio-frequency signals S ₁ by the phase shift circuit 424 and the power distribution separation into two independent signals A ₁ and A _2. Signals A ₁ and A _{2 are} transmitted to a vertical linearly polarized antenna and a horizontal linearly polarized antenna in the circularly polarized antenna 426 to emit a first circularly polarized wave. Similarly, another radio frequency signal S ₂ by the phase shift and power distribution circuit 444 is separated into two independent signals A ₃ and A _4. Signals A ₃ and A _{4 are} transmitted to a vertical linearly polarized antenna and a horizontal linearly polarized antenna in the circularly polarized antenna 446 to emit a second circularly polarized wave.

As previously mentioned, when designing the antenna configuration, adjacent antennas in the same transceiver should have high isolation to avoid receiving signals from each other. However, if the signal is transmitted between different transceivers, the polarization directions of the transmitting antenna and the receiving antenna should be the same in order to achieve the maximum amount of data transmission. Therefore, in the present embodiment, when the circularly polarized antenna 426 is designed as a right-hand circularly polarized antenna, the circularly polarized antenna 446 is preferably designed as a right-hand circularly polarized antenna, and when the circularly polarized antenna 426 is designed as When the left hand is circularly polarized, the circularly polarized antenna 446 is preferably designed as a left-hand circularly polarized antenna. The polarization directions of the circularly polarized antennas can be obtained by adjusting the phases of the signals A ₁ , A ₂ , A ₃ and A ₄ of FIG.

FIG. 5 shows a block diagram of a wireless communication system 50 having multiple inputs and multiple outputs in combination with an embodiment of the present invention. The wireless communication system 50 includes a transceiver 52 and a transceiver 54. The transceiver 52, similar to FIG. 3, includes circularly polarized antennas 524, 525, a linearly polarized antenna 526, and phase offset and power distribution circuits 522, 523 coupled to the circularly polarized antennas 524, 525. The transceiver 54, similar to FIG. 3, includes circularly polarized antennas 544, 545, a linearly polarized antenna 546, and phase offset and power distribution circuits 542, 543 coupled to the circularly polarized antennas 544, 545. According to the principle of polarization separation described above, when the circularly polarized antenna 524 is designed as a left-hand circularly polarized antenna, the circularly polarized antenna 525, the circularly polarized antenna 544, and the circularly polarized antenna 545 can be sequentially designed as right-handed Circularly polarized antenna, left-hand circularly polarized antenna, and right-hand circularly polarized antenna. Likewise, the linear polarization antenna 526 and the linearly polarized antenna 546 should have the same optimal linear polarization direction.

If the transceivers 52 and 54 are devices that conform to the 802.11n standard specified by the Institute of Electrical and Electronics Engineers (IEEE), they are compatible with the IEEE 802.11a/b/g standard. When transceivers 52 and 54 operate at low transmission rates, the system will switch to 802.11b mode to cover a larger transmission range. Referring to FIG. 5, when the transceiver 52 switches to the 802.11b mode, the linearly polarized antenna 526 is configured to transmit or receive signals, and when the transceiver 54 switches to the 802.11b mode, the linearly polarized antenna The 546 system is configured to transmit or receive signals. Similarly, one of the vertically linearly polarized antenna and one of the horizontally linearly polarized antennas constituting the circularly polarized antenna 426 of FIG. 4 is configured to be responsible for when the transceiver 42 switches to the 802.11b mode. Transmit or receive signals.

6 shows a block diagram of a wireless communication system 60 having multiple inputs and multiple outputs in accordance with one embodiment of the present invention. The wireless communication system 60 includes a transceiver 62 and a transceiver 44. The transceiver 62 includes a circularly polarized antenna 624, linearly polarized antennas 626, 628, and a phase offset and power distribution circuit 622 coupled to the circularly polarized antenna 624. The transceiver 64 includes a circularly polarized antenna 644, a linearly polarized antenna 646, 648, and a phase offset and power distribution circuit 642 coupled to the circularly polarized antenna 644. In the present embodiment, the linearly polarized antenna 626 is configured to transmit or receive signals when the transceiver device 62 is switched to the 802.11b mode, and the linearly polarized antenna 646 is configured to be used as the transceiver device. 64 is responsible for transmitting or receiving signals when switching to 802.11b mode. According to the principle of polarization separation described above, when the linearly polarized antenna 626 is designed as a horizontally linearly polarized antenna, the linearly polarized antenna 628, the linearly polarized antenna 646, and the linearly polarized antenna 648 can be designed to be vertical. Linearly polarized antennas, horizontally linearly polarized antennas, and vertically linearly polarized antennas. Further, the circularly polarized antenna 624 and the circularly polarized antenna 644 are disposed to have the same circular polarization direction. With the antenna configuration described above, the transmission efficiency between the antennas can be greatly increased regardless of whether the wireless communication system 60 operates at a low transmission rate or a high transmission rate.

7 shows a flow chart of a method for a multiple input multiple output wireless communication system in accordance with an embodiment of the present invention. In step S70, a first circularly polarized transmit signal is transmitted by a first transceiver at a first circularly polarized antenna. In step S72, the first circularly polarized transmitting signal is received by a second transceiver at a second circularly polarized antenna to generate a first received signal. The first circularly polarized antenna and the second circularly polarized antenna have the same circular polarization direction.

In step S70, a first signal to be transmitted is first separated into two signals having a phase difference of 90 degrees. Then, the two signals are respectively transmitted by a vertical linearly polarized antenna and a horizontal linearly polarized antenna to form the first circularly polarized transmission signal. In step S72, the first circularly polarized transmission signals are respectively received by a vertical linearly polarized antenna and a horizontal linearly polarized antenna. Then, signals from the vertical linearly polarized antenna and the horizontal linearly polarized antenna are combined to generate the first received signal.

In another embodiment of the present invention, in addition to steps S70 and S72, steps S80 and S82 shown in FIG. 8 may be further included. In step S80, a second circularly polarized transmit signal is transmitted by the first transceiver at a third circularly polarized antenna. In step S82, the second transceiver receives the second circularly polarized transmission signal by a fourth circularly polarized antenna to generate a second received signal. The third and fourth circularly polarized antennas have the same circular polarization direction, and the first and third circularly polarized antennas have different circular polarization directions, and the second and fourth circularly polarized antennas have Different circular polarization directions.

Similarly, in step S80, a second signal to be transmitted is first separated into two signals having a phase difference of 90 degrees. Then, the two signals are respectively transmitted by a vertical linearly polarized antenna and a horizontal linearly polarized antenna to form the second circularly polarized transmission signal. In step S82, the second circularly polarized transmission signals are respectively received by a vertical linearly polarized antenna and a horizontal linearly polarized antenna. The signals from the vertically linearly polarized antenna and the horizontally linearly polarized antenna are then combined to produce the second received signal.

In still another embodiment of the present invention, in addition to steps S70 and S72, steps S90 and S92 shown in FIG. 9 may be further included. In step S90, a linearly polarized signal is transmitted from the first transceiver at a first linearly polarized antenna. In step S92, the linearly polarized signal is received by the second transceiver at a second linearly polarized antenna.

The technical and technical features of the present invention have been disclosed as above, and those skilled in the art can still make various substitutions and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the present invention is not to be construed as being limited by the scope of the invention, and

10. . . Wireless transceiver

12. . . Transceiver unit

14. . . Phase shift and power distribution circuit

16. . . Circularly polarized antenna

20. . . Wireless transmitter

22~24. . . Circularly polarized antenna

26~28. . . Phase shift and power distribution circuit

30. . . Wireless transmitter

32~34. . . Circularly polarized antenna

35. . . Linearly polarized antenna

36~38. . . Phase shift and power distribution circuit

40. . . Wireless communication system

42~44. . . Transceiver

422. . . Transceiver unit

424. . . Phase shift and power distribution circuit

426. . . Circularly polarized antenna

442. . . Transceiver unit

444. . . Phase shift and power distribution circuit

446. . . Circularly polarized antenna

50. . . Wireless communication system

52. . . Transceiver

54. . . Transceiver

522~523. . . Phase shift and power distribution circuit

524~525. . . Circularly polarized antenna

526. . . Linearly polarized antenna

542~543. . . Phase shift and power distribution circuit

544~545. . . Circularly polarized antenna

546. . . Linearly polarized antenna

60. . . Wireless communication system

62. . . Transceiver

64. . . Transceiver

622. . . Phase shift and power distribution circuit

624. . . Circularly polarized antenna

626~628. . . Linearly polarized antenna

642. . . Phase shift and power distribution circuit

644. . . Circularly polarized antenna

646~648. . . Linearly polarized antenna

S70~S72. . . step

S80~S82. . . step

S90~S92. . . step

1 shows a schematic structural diagram of a wireless transceiver in combination with an embodiment of the present invention;

2 is a schematic diagram showing the architecture of a wireless transceiver in combination with another embodiment of the present invention;

3 is a block diagram showing the architecture of a wireless transceiver in accordance with still another embodiment of the present invention;

4 is a block diagram showing the architecture of a wireless communication system having multiple inputs and multiple outputs in combination with an embodiment of the present invention;

5 is a block diagram showing the architecture of a wireless communication system having multiple inputs and multiple outputs in combination with an embodiment of the present invention;

6 is a block diagram showing the architecture of a wireless communication system having multiple inputs and multiple outputs in combination with an embodiment of the present invention;

7 shows a flow chart of a method for a multiple input multiple output wireless communication system in accordance with an embodiment of the present invention;

8 shows a flow chart of a method for a multiple input multiple output wireless communication system in accordance with another embodiment of the present invention; and

9 shows a flow chart of a method for a multiple input multiple output wireless communication system in accordance with yet another embodiment of the present invention;

20. . . Wireless transmitter

22~24. . . Circularly polarized antenna

26~28. . . Phase shift and power distribution circuit

Claims (26)

A wireless transceiver comprising: a first circularly polarized antenna; a first phase offset and power distribution circuit coupled to the first circularly polarized antenna; a second circularly polarized antenna; and a second phase An offset and power distribution circuit coupled to the second circularly polarized antenna; wherein a circular polarization direction of the second circularly polarized antenna is perpendicular to a circular polarization direction of the first circularly polarized antenna, the first circle The vertically linearly polarized antenna included in the polarized antenna and the vertically linearly polarized antenna included in the second circularly polarized antenna respectively have a phase difference of 90 degrees, and the horizontal line included in the first circularly polarized antenna The polarized antenna has a phase difference of 90 degrees between the signals transmitted by the horizontally linearly polarized antennas included in the second circularly polarized antenna. The wireless transceiver of claim 1, wherein the first circularly polarized antenna comprises a first vertical linearly polarized antenna and a first horizontal linearly polarized antenna, the first phase offset and power distribution circuit generating 90 degrees Two signals of the phase difference are transmitted through the first vertical linearly polarized antenna and the first horizontal linearly polarized antenna, respectively. The wireless transceiver of claim 2, wherein one of the first vertical linearly polarized antenna or the first horizontal linearly polarized antenna is configured to be responsible for transmitting or when the wireless transceiver switches to the 802.11b mode receive signal. The wireless transceiver of claim 1, wherein the first circularly polarized antenna The direction can be obtained by adjusting the phase offset and the phase of the output signal of the power distribution circuit. The wireless transceiver of claim 1, wherein the second circularly polarized antenna comprises a second vertical linearly polarized antenna and a second horizontal linearly polarized antenna, and the second phase offset and power distribution circuit generates 90 Two signals of phase difference are transmitted through the second vertical linear polarization antenna and the second horizontal linear polarization antenna, respectively. The wireless transceiver of claim 5, further comprising a linearly polarized antenna. The wireless transceiver of claim 6, wherein the linearly polarized antenna is configured to transmit or receive a signal when the wireless transceiver switches to the 802.11b mode. The wireless transceiver of claim 1, further comprising a horizontally linearly polarized antenna and a vertically polarized antenna. The wireless transceiver of claim 8, wherein one of the vertical linearly polarized antenna or the horizontally linearly polarized antenna is configured to transmit or receive a signal when the wireless transceiver switches to the 802.11b mode. A wireless communication system having multiple inputs and multiple outputs, comprising: a first transceiver device comprising a first circularly polarized antenna and a first phase offset and power distribution circuit coupled to the first circularly polarized antenna; A second transceiver device includes a second circularly polarized antenna and a second phase shifting and power distribution circuit coupled to the second circularly polarized antenna; wherein the first circularly polarized antenna and the second circular pole The antenna has the same circular polarization direction, that is, the first circularly polarized antenna and the second circularly polarized antenna At the same time, it is designed as a right-hand circularly polarized antenna, or the first circularly polarized antenna and the second circularly polarized antenna are simultaneously designed as a left-hand circularly polarized antenna. The wireless communication system of claim 10, wherein the first circularly polarized antenna comprises a first vertical linearly polarized antenna and a first horizontal linearly polarized antenna, and the second circularly polarized antenna comprises a second vertical linear An antenna and a second horizontal linearly polarized antenna, the first phase shifting and power distribution circuit generating two signals having a phase difference of 90 degrees, respectively passing through the first vertical linearly polarized antenna and the first horizontal linear pole The antenna is transmitted, and the second phase shifting and power distribution circuit generates two signals having a phase difference of 90 degrees, respectively transmitted through the second vertical linearly polarized antenna and the second horizontal linearly polarized antenna. The wireless communication system of claim 11, wherein one of the first vertical linearly polarized antenna or the first horizontal linearly polarized antenna is configured to be responsible for transmitting when the first transceiver is switched to the 802.11b mode Or receiving a signal, and one of the second vertical linearly polarized antenna or the second horizontal linearly polarized antenna is configured to transmit or receive a signal when the second transceiver switches to the 802.11b mode. The wireless communication system of claim 10, wherein the polarization directions of the first and second circularly polarized antennas are obtained by adjusting phases of the output signals of the first and second phase offsets and power distribution circuits. The wireless communication system of claim 10, wherein the first transceiver further comprises a third circularly polarized antenna and a third phase offset and power distribution circuit coupled to the third circularly polarized antenna, the second transceiver The device further includes a fourth circularly polarized antenna and a fourth coupled to the fourth circularly polarized antenna a phase shifting and power distribution circuit, wherein a circular polarization direction of the third circularly polarized antenna is different from the first circularly polarized antenna, and a circular polarization direction of the fourth circularly polarized antenna and the second circular polarization The antennas are different, and the third circularly polarized antenna and the fourth circularly polarized antenna have the same circular polarization direction. The wireless communication system of claim 14, wherein the third circularly polarized antenna comprises a third vertical linearly polarized antenna and a third horizontal linearly polarized antenna, the fourth circularly polarized antenna comprising a fourth vertical linear pole An antenna and a fourth horizontal linearly polarized antenna, the third phase shifting and power distribution circuit generating two signals having a phase difference of 90 degrees, respectively passing through the third vertical linearly polarized antenna and the third horizontal linear pole The antenna is transmitted, and the fourth phase shift and power distribution circuit generates two signals having a phase difference of 90 degrees, respectively transmitted through the fourth vertical linearly polarized antenna and the fourth horizontal linearly polarized antenna. The wireless communication system of claim 15, wherein the first transceiver further comprises a first linearly polarized antenna, and the second transceiver further comprises a second linearly polarized antenna, and the first linear polarization The antenna and the second linearly polarized antenna have the same circular polarization direction. The wireless communication system of claim 16, wherein the first linearly polarized antenna is configured to transmit or receive a signal when the first transceiver is switched to the 802.11b mode, and the second linearly polarized antenna system The setting is for transmitting or receiving a signal when the second transceiver switches to the 802.11b mode. The wireless communication system of claim 10, wherein the first transceiver further comprises a fifth horizontal linear polarization antenna and a fifth vertical polarization day And the second transceiver further includes a sixth horizontal linearly polarized antenna and a sixth vertically polarized antenna, wherein the sixth horizontal linearly polarized antenna is responsible for transmitting or receiving the signal of the fifth horizontal linearly polarized antenna, And the sixth vertical linearly polarized antenna is responsible for transmitting or receiving the signal of the fifth vertical linearly polarized antenna. A wireless communication system according to claim 18, wherein one of the fifth vertical linearly polarized antenna or the fifth horizontal linearly polarized antenna is configured to be responsible for transmitting when the first transceiver is switched to the 802.11b mode Or receiving a signal, and one of the sixth vertical linearly polarized antenna or the sixth horizontal linearly polarized antenna is configured to transmit or receive a signal when the second transceiver is switched to the 802.11b mode. A method for a wireless communication system for multiple input multiple output, comprising the steps of: transmitting a first circularly polarized transmit signal to a first circularly polarized antenna at a first transceiver; and Receiving, by the second circularly polarized antenna, the first circularly polarized transmitting signal to generate a first received signal; wherein the first circularly polarized antenna and the second circularly polarized antenna have the same circular polarization direction, that is, The first circularly polarized antenna and the second circularly polarized antenna are simultaneously designed as a right-hand circularly polarized antenna, or the first circularly polarized antenna and the second circularly polarized antenna are simultaneously designed as a left-hand circularly polarized antenna. The method of claim 20, wherein the transmitting, by the first transceiver, the first circularly polarized transmission signal by the first circularly polarized antenna comprises: separating a first to-be-transmitted signal into two phases having a 90 degree phase Bad letter And transmitting the two signals by a vertical linearly polarized antenna and a horizontal linearly polarized antenna, respectively, to form the first circularly polarized transmit signal. The method of claim 21, wherein the step of receiving, by the second transceiver, the first circularly polarized transmit signal by the second circularly polarized antenna comprises: respectively: a vertical linearly polarized antenna and a horizontally linearly polarized antenna Receiving the first circularly polarized transmit signal; and combining signals from the vertical linearly polarized antenna and the horizontal linearly polarized antenna to generate the first received signal. The method of claim 20, further comprising the steps of: transmitting, by the first transceiver, a second circularly polarized transmit signal by a third circularly polarized antenna; and applying a fourth circular pole to the second transceiver Receiving the second circularly polarized transmit signal to generate a second received signal; wherein the third and fourth circularly polarized antennas have the same circular polarization direction, and the first and the third circular polarization The antennas have different circular polarization directions, and the second and fourth circularly polarized antennas have different circular polarization directions. The method of claim 23, wherein the step of transmitting the second circularly polarized transmission signal by the first transceiver with the third circularly polarized antenna comprises: separating a second to-be-transmitted signal into two phases having a 90 degree phase a difference signal; and transmitting the two signals by a vertical linearly polarized antenna and a horizontal linearly polarized antenna, respectively, to form the second circularly polarized transmit signal. The method of claim 23, wherein the step of receiving, by the second transceiver, the second circularly polarized transmit signal by the fourth circularly polarized antenna comprises: Receiving the second circularly polarized transmit signal with a vertical linearly polarized antenna and a horizontal linearly polarized antenna, respectively; and combining signals from the vertical linearly polarized antenna and the horizontal linearly polarized antenna to generate the second received signal . The method of claim 20, further comprising the steps of: transmitting, by the first transceiver, a linearly polarized signal with a first linearly polarized antenna; and the second transceiver with a second linearly polarized antenna The linearly polarized signal is received.