Wireless transmission system, wireless communication device and wireless transmission method

• US 8,687,725 B2
• Filed: 08/23/2010
• Issued: 04/01/2014
• Est. Priority Date: 09/29/2009
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Mihoto, Norihito
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US12/805,875
• Publication Number:
  US 20110075747A1
• Time in Patent Office: 1,317 Days
• Field of Search: 375/259, 375/260, 375/267, 370/277, 370/278, 370280-282, 370/310, 455/17, 455/22, 455/24, 455/25, 455/500, 455/63.4, 455/88, 455/553.1
• US Class Current: 375/267
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04B 7/0413 MIMO systems

Abstract

Disclosed herein is a wireless transmission system. Transmission antennas are provided on a first communication apparatus while reception antennas individually corresponding to the transmission antennas are provided on a corresponding second communication apparatus. Each reception antenna receives a desired wave from a corresponding transmission antenna as a direct wave and receives an unnecessary wave from a different transmission antenna as a direct wave. The first communication apparatus modulates only the amplitude of a carrier signal for all channels. The second communication apparatus demodulates composite waves of desired waves and unnecessary waves received by the reception antennas by envelope detection or square-law detection and carries out correction operation for the demodulation signals based on transmission characteristics of transmission spaces between the transmission and reception antennas to acquire transmission subject signals.

Claims

1. A wireless communication system, comprising:

antenna pairs, a radio signal radiated from a transmission antenna of a first one of the antenna pairs arriving as a desired signal at a reception antenna of the first one of the antenna pairs while a radio signal radiated from a transmission antenna of a second one of the antenna pairs different from the first one of the antenna pairs arriving as an unnecessary signal at the reception antenna of the first one of the antenna pairs;

a modulation functional unit associated with each of the antenna pairs, the modulation functional unit being configured to generate a modulated carrier signal by modulating a carrier signal with a desired transmission subject signal, the modulation functional unit being configured to transmit the modulated carrier signal from a transmission antenna of a corresponding one of the antenna pairs, the modulation functional unit adopting amplitude modulation;

a demodulation functional unit configured to use envelope detection or square-law detection to detect modulation signals received with regard to all channels of transmission subject signals; and

a transmission characteristic correction unit configured to carry out correction calculation based on a transmission characteristic of a transmission space between a transmission antenna from a particular one of the antenna pairs and a reception antenna from any of the antenna pairs based on a demodulation signal demodulated by said demodulation functional unit, the demodulation signal corresponding to the reception antenna from any of the antenna pairs to acquire an output signal corresponding to one of the transmission subject signals,

wherein, where a wavelength of a demodulation carrier signal used in said demodulation functional unit is represented by λ

c and a phase characteristic which relies upon directivity of the antenna pairs is represented by zero, a path difference which is a difference between an inter-antenna distance of the desired signal and an inter-antenna distance of the unnecessary signal is set to (n/2)λ

c, n being a positive integer equal to or higher than 1.

2. The wireless communication system according to claim 1, wherein said transmission characteristic correction unit carries out the correction calculation regarding a real number term corresponding to the desired signal and the correction calculation regarding a different real number term corresponding to the unnecessary signal for demodulation components demodulated by said demodulation functional unit, said transmission characteristic correction unit adding a corrected signal regarding the real number term and a corrected signal regarding the different real number term regarding one of the channels between the transmission antenna from the particular one of the antenna pairs and the reception antenna from any of the antenna pairs to acquire an output signal corresponding to the desired transmission subject signal.

3. The wireless communication system according to claim 1, wherein path differences each of which is a difference between an inter-antenna distance of the desired signal and an inter-antenna distance of the unnecessary signal is set such that each of elements of the desired signal of a matrix which defines the transmission characteristic can be represented only by a real number term corresponding to the desired signal while each of elements of the unnecessary signal of the matrix which defines the transmission characteristic can be represented only by a different real number term corresponding to the unnecessary signal.

4. The wireless communication system according to claim 1, wherein n is an even number and the path difference is set to mλ

c where m is a positive integer equal to or greater than 1.

5. The wireless communication system according to claim 1, wherein n is an odd number and the path difference is set to (m−

½

)λ

c where m is a positive integer equal to or greater than 1.

6. The wireless communication system according to claim 1, wherein, where a radiation angle of the desired signal from the transmission antenna of the first one of the antenna pairs and an incidence angle of the desired signal to the reception antenna of the first one of the antenna pairs are represented by θ

1;

a radiation angle of the unnecessary signal from the transmission antenna of the second one of the antenna pairs and an incidence angle of the unnecessary signal to the reception antenna of the first one of the antenna pairs are represented by θ

2; and

phase characteristics which rely upon a directivity of the transmission antenna of the first one of the antenna pairs and the reception antenna of the first one of the antenna pairs are represented by φ

a(θ

1) and φ

a(θ

2), respectively, the path difference is corrected by −

(φ

a(θ

2) −

φ

a(θ

1))/Π

)λ

c.

7. The wireless communication system according to claim 1, wherein carrier signals used by the modulation functional unit and carrier signals used by the demodulation functional unit have a common frequency to all of the channels.

8. A wireless communication system which includes antenna pairs, a radio signal radiated from a transmission antenna of a first one of the antenna pairs arriving as a desired signal at a reception antenna of the first one of the antenna pairs while a radio signal radiated from a transmission antenna of a second one of the antenna pairs different from the first one of the antenna pairs arriving as an unnecessary signal at the reception antenna of the first one of the antenna pairs, said wireless communication system comprising:

a demodulation functional unit corresponding to the reception antenna of the first one of the antenna pairs, the demodulation functional unit being configured to use envelope detection or square-law detection to detect a received modulation signal wherein only an amplitude of a carrier signal is modulated for all channels of transmission subject signals; and

a transmission characteristic correction unit configured to carry out correction calculation based on a transmission characteristic of a transmission space between a transmission antenna from a particular one of the antenna pairs and a reception antenna from any of the antenna pairs based on a demodulation signal demodulated by said demodulation functional unit, said demodulation functional unit corresponding to the reception antenna from any of the antenna pairs to acquire an output signal corresponding to a transmission subject signal,

wherein a path difference is a difference between an inter-antenna distance of the desired signal and an inter-antenna distance of the unnecessary signal between the transmission antenna from the particular one of the antenna pairs and the reception antenna from any of the antenna pairs is set such that each of elements of the desired signal of a matrix which defines the transmission characteristic can be represented only by a real number term corresponding to the desired signal while each of elements of the unnecessary signal of the matrix which defines the transmission characteristic can be represented only by a different real number term corresponding to the unnecessary signal.

9. The wireless transmission system according to claim 8, wherein said transmission characteristic correction unit carries out the correction calculation regarding the real number term and the correction calculation regarding the different real number term, and adds a corrected signal regarding the real number term and a corrected signal regarding the different real number term regarding a channel of a different reception antenna to acquire an output signal corresponding to a desired transmission subject signal.

10. The wireless communication system according to claim 8, wherein, where a wavelength of a demodulation carrier signal used in said demodulation functional unit is represented by λ

c and a phase characteristic which relies upon directivity of the antenna pairs is represented by zero, a path difference which is a difference between an inter-antenna distance of the desired signal and an inter-antenna distance of the unnecessary signal is set to (n/2)λ

c, n being a positive integer equal to or higher than 1.

11. The wireless communication system according to claim 10, wherein n is an even number and the path difference is set to mλ

c where m is a positive integer equal to or greater than 1.

12. The wireless communication system according to claim 10, wherein n is an odd number and the path difference is set to (m−

½

)λ

c where m is a positive integer equal to or greater than 1.

13. The wireless communication system according to claim 10, wherein, where a radiation angle of the desired signal from the transmission antenna of the first one of the antenna pairs and an incidence angle of the desired signal to the reception antenna of the first one of the antenna pairs are represented by θ

1;

a radiation angle of the unnecessary signal from the transmission antenna of the second one of the antenna pairs and an incidence angle of the unnecessary signal to the reception antenna of the first one of the antenna pairs are represented by θ

2; and

phase characteristics which rely upon a directivity of the transmission antenna of the first one of the antenna pairs and the reception antenna of the first one of the antenna pairs are represented by φ

a(θ

1) and φ

a(θ

2), respectively, the path difference is corrected by −

(φ

a(θ

2)−

φ

a(θ

1))/Π

)λ

c.

14. The wireless communication system according to claim 8, further comprising:

a modulation functional unit associated with each of the antenna pairs, the modulation functional unit being configured to generate a modulated carrier signal by modulating a carrier signal with a desired transmission subject signal,

wherein carrier signals used by the modulation functional unit and carrier signals used by the demodulation functional unit have a common frequency to all of the channels.

15. A communication method for a wireless communication system which includes antenna pairs, a radio signal radiated from a transmission antenna of a first one of the antenna pairs arriving as a desired signal at a reception antenna of the first one of the antenna pairs while a radio signal radiated from a transmission antenna of another one of the antenna pairs different from the first one of the antenna pairs arriving as an unnecessary signal at the reception antenna of the first one of the antenna pairs, the wireless communication method comprising the steps of:

modulating, by a wireless communication device on a transmission side, only an amplitude of a carrier signal for all channels of transmission subject signals and transmitting modulated carrier signals by space division multiplexing by wireless;

using, by a wireless communication device on a reception side, envelope detection or square-law detection for the modulated carrier signals received for all the channels to acquire demodulation signals;

performing, by the wireless communication device on the reception side, correction calculation based on a transmission characteristic of a transmission space among the transmission antennas and reception antennas based on the demodulation signals individually corresponding to the reception antennas to acquire output signals corresponding to the transmission subject signals;

performing, for each of the channels respectively of the reception antennas, correction calculation regarding a real number term corresponding to the desired signal and correction calculation regarding a different real number term corresponding to the unnecessary signal for demodulation components; and

adding a corrected signal regarding the real number term and a corrected signal regarding the different real number term regarding a channel of a different reception antenna to acquire an output signal corresponding to a desired transmission subject signal.

16. The wireless communication method according to claim 15, wherein path differences each of which is a difference between an inter-antenna distance of the desired signal and an inter-antenna distance of the unnecessary signal is set such that each of elements of the desired signal of a matrix which defines the transmission characteristic can be represented only by the real number term while each of elements of the unnecessary signal of the matrix which defines the transmission characteristic can be represented only by the different real number term.

17. The wireless communication method according to claim 15, wherein, where a wavelength of a demodulation carrier signal is represented by λ

c and a phase characteristic which relies upon directivity of the antenna pairs is represented by zero, a path difference which is a difference between an inter-antenna distance of the desired signal and an inter-antenna distance of the unnecessary signal is set to (n/2)λ

c, n being a positive integer equal to or higher than 1.