Beam forming apparatus and method for an array antenna system

• US 20050271016A1
• Filed: 05/06/2005
• Published: 12/08/2005
• Est. Priority Date: 05/07/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Scholand, Tobias, H.A., Ar Jang, Jung, Peter, Seebens, Achim, Kim, Byoung-Yun, Kim, Song-Hun, Daniel, Katz Marcos, Park, Seong-Ill
• Granted Patent: US 7,352,721 B2
• Time in Patent Office: Days
• US Class Current: 370/332
• CPC Class Codes: H01Q 1/1257 using the received signal strength
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming

Abstract

A joint channel and Direction of Arrival (DOA) estimation apparatus and method simplified to efficiently estimate a channel impulse response associated with a spatially selective transmission channel occurring in a mobile radio channel are provided. To uniformly process all directions, angles associated with a beam are predetermined according to a preset method. This selection calculates a linear system model with regular spatial sampling using regular spatial separation of beam angles. The novel beam forming compensates for a difference between an adaptive array antenna and a sector type antenna using appropriate beam steering according to the calculated linear system model, thereby improving performance and facilitating implementation.

Claims

1. A beam forming apparatus for an antenna diversity system with an array antenna having a plurality of antenna elements, the apparatus comprising:

an interference and noise calculator for estimating interference power R_DOA and spectral noise density N₀ of a radio channel using a signal received through the radio channel, and calculating total noise power of the radio channel according to the interference power and the spectral noise density;

a channel estimator for calculating a phase matrix including phase factors associated with a predetermined number of direction-of-arrival (DOA) values and a directional channel impulse response matrix using the total noise power, and calculating a combined channel impulse response by combining the phase matrix with the directional channel impulse response matrix; and

a beam former for performing beam forming for transmission and reception through the array antenna using the combined channel impulse response.

2. The beam forming apparatus of claim 1, wherein the number of the DOA values is set to a maximum integer not exceeding a product (2π

B) of a possible maximum spatial bandwidth (B) of the array antenna and a double circle ratio (2π

).

3. The beam forming apparatus of claim 1, wherein the number of DOA values is equal to the number of the antenna elements comprising the array antenna when the array antenna has a uniform circular array (UCA) geometry.

4. The beam forming apparatus of claim 1, wherein each of the DOA values is determined by

5. The beam forming apparatus of claim 4, wherein the β

₀ has a value between 0 and π

/N_b radian.

6. The beam forming apparatus of claim 1, wherein the interference power is expressed with a Hermitian matrix of which diagonal elements are defined in the following equation and the other elements are all zeros (0s),

7. The beam forming apparatus of claim 1, wherein the channel estimator evaluates channel estimation values of the directional channel impulse response for each direction for each user, calculates a modified directional channel impulse response by maintaining only a direction showing the maximum channel estimation value and setting channel estimation values for all the other directions to zero.

8. The beam forming apparatus of claim 1, wherein the beam former determines a spatial channel and a DOA of a desired optimal signal using the beam forming.

9. A beam forming method for an antenna diversity system with an array antenna having a plurality of antenna elements, the method comprising the steps of:

estimating interference power R_DOA and spectral noise density N₀ of a radio channel using a signal received through the radio channel, and calculating total noise power of the radio channel according to the interference power and the spectral noise density;

calculating a phase matrix including phase factors associated with a predetermined number of direction-of-arrival (DOA) values and a directional channel impulse response matrix using the total noise power, and calculating a combined channel impulse response by combining the phase matrix with the directional channel impulse response matrix; and

performing beam forming for transmission and reception through the array antenna using the combined channel impulse response.

10. The beam forming method of claim 9, wherein the number of the DOA values is set to a maximum integer not exceeding a product (2π

B) of a possible maximum spatial bandwidth (B) of the array antenna and a double circle ratio (2π

).

11. The beam forming method of claim 9, wherein the number of DOA values is equal to the number of the antenna elements comprising the array antenna when the array antenna has a uniform circular array (UCA) geometry.

12. The beam forming method of claim 9, wherein each of the DOA values is determined by

13. The beam forming method of claim 12, wherein the β

₀ has a value between 0 and π

/N_b radian.

14. The beam forming method of claim 9, wherein the interference power is expressed with a Hermitian matrix of which diagonal elements are defined in the following equation and the other elements are all zeros (0s),

15. The beam forming method of claim 9, wherein the step of calculating a combined channel impulse response comprises the step of evaluating channel estimation values of the directional channel impulse response for each direction for each user, calculating a modified directional channel impulse response by maintaining only a direction showing the maximum channel estimation value and setting channel estimation values for all the other directions to zero.

16. The beam forming method of claim 9, further comprising the steps of determining a spatial channel and a DOA of a desired optimal signal using the beam forming.