Wireless transmission system, wireless communication device and wireless transmission method

• US 20110075747A1
• Filed: 08/23/2010
• Published: 03/31/2011
• Est. Priority Date: 09/29/2009
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Mihota, Norihito
• Granted Patent: US 8,687,725 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• 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 transmission system, comprising:

a plurality of antenna pairs each including a combination of a transmission antenna and a reception antenna corresponding to each other and disposed such that a radio signal radiated from the transmission antenna of a first one of the antenna pairs directly arrives as a desired wave at the reception antenna of the first antenna pair while a radio signal radiated from the transmission antenna of a second one of the antenna pairs different from the first antenna pair directly arrives as an unnecessary wave at the reception antenna of the first antenna pair;

a modulation functional unit provided for each of the antenna pairs and adapted to modulate a carrier signal with a transmission subject signal and transmit the modulated carrier signal from the transmission antenna of the corresponding antenna pair, the modulation functional units of all channels of a plurality of transmission subject signals adopting a method which modulates only the amplitude;

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

a transmission characteristic correction unit adapted to carry out correction calculation based on transmission characteristics of transmission spaces between the transmission antennas and the reception antennas based on demodulation signals demodulated by said demodulation functional unit and individually corresponding to the reception antennas to acquire output signals corresponding to the transmission subject signals.

2. The wireless transmission system according to claim 1, wherein said transmission characteristic correction unit carries out, for each of channels of the plural reception antennas, correction calculation regarding the real number term corresponding to a desired signal and correction calculation regarding the real number term corresponding to a unnecessary signal for demodulation components demodulated by said demodulation functional unit, and adds a corrected signal regarding the real number term corresponding to the desired signal and a corrected signal regarding the real number term corresponding to the unnecessary signal regarding the channel of the different reception antenna to acquire an output signal corresponding to the transmission subject signal.

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

4. The wireless transmission system according to claim 1, wherein, where a wavelength of a carrier signal used in said demodulation functional unit is represented by λ

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

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

5. The wireless transmission system according to claim 4, wherein the parameter 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.

6. The wireless transmission system according to claim 4, wherein the parameter 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, and

a wireless communication device on the transmission side sets a modulation degree so that phase reversal may not occur with a composite signal of the desired wave and the unnecessary wave.

7. The wireless transmission system according to claim 4, wherein, where a radiation angle of the desired wave from the transmission antenna of the first antenna pair and an incidence angle of the desired wave to the reception antenna of the first antenna pair is represented by θ

1;

a radiation angle of the unnecessary wave from the transmission antenna of the second antenna pair and an incidence angle of the unnecessary wave to the reception antenna of the first antenna pair is represented by θ

2; and

phase characteristics which rely upon the directivity of the transmission antennas and the reception antenna 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.

8. The wireless transmission system according to claim 1, wherein carrier signals used by the modulation functional units and the demodulation functional units have a common frequency to all channels.

9. A wireless communication device for a system which includes a plurality of antenna pairs each including a combination of a transmission antenna and a reception antenna corresponding to each other and disposed such that a radio signal radiated from the transmission antenna of a first one of the antenna pairs directly arrives as a desired wave at the reception antenna of the first antenna pair while a radio signal radiated from the transmission antenna of a second one of the antenna pairs different from the first antenna pair directly arrives as an unnecessary wave at the reception antenna of the first antenna pair, said wireless communication device comprising:

a demodulation functional unit provided corresponding to each of the reception antennas and adapted to use envelope detection or square-law detection to detect a received modulation signal wherein only the amplitude of a carrier signal is modulated; and

a transmission characteristic correction unit adapted to carry out correction calculation based on transmission characteristics of transmission spaces between the transmission antennas and the reception antennas based on demodulation signals demodulated by said demodulation functional unit and individually corresponding to the reception antennas to acquire output signals corresponding to the transmission subject signals.

10. The wireless transmission device according to claim 9, wherein said transmission characteristic correction unit carries out, for each of channels of the plural reception antennas, correction calculation regarding the real number term corresponding to the desired wave and correction calculation regarding the real number term corresponding to the unnecessary wave for demodulation components demodulated by said demodulation functional unit, and adds a corrected signal regarding the real number term corresponding to the desired wave and a corrected signal regarding the real number term corresponding to the unnecessary wave regarding the channel of the different reception antenna to acquire an output signal corresponding to the transmission subject signal.

11. A wireless transmission method for a system which includes a plurality of antenna pairs each including a combination of a transmission antenna and a reception antenna corresponding to each other and disposed such that a radio signal radiated from the transmission antenna of one of the antenna pairs directly arrives as a desired wave at the reception antenna of the one antenna pair while a radio signal radiated from the transmission antenna of another one of the antenna pairs different from the one antenna pair directly arrives as an unnecessary wave at the reception antenna of the one antenna pair, the wireless transmission method comprising the steps of:

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

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

carried out by the wireless communication device on the reception side, carrying out correction calculation based on transmission characteristics of transmission spaces between the transmission antennas and the reception antennas based on the demodulation signals individually corresponding to the reception antennas to acquire output signals corresponding to the transmission subject signals.