Calibration method for smart antenna arrays

• US 20070069945A1
• Filed: 09/08/2006
• Published: 03/29/2007
• Est. Priority Date: 09/28/2005
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Weese, Kurt
• Granted Patent: US 7,593,826 B2
• Time in Patent Office: Days
• US Class Current: 342/174
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

The invention relates to a method of calibrating the reception path and the transmit path of an antenna array which comprises at least three antennas and which is connected to a digital signal processor. For calibrating the reception path a signal of known amplitude and known phase is transmitted by a single antenna, whereby this signal is received by the other n−1 antennas, whereby a phase difference and an amplitude difference between each of the n−1 transmitted signals is evaluated. The last two steps are repeated with a new transmit antenna until every antenna has been used as a transmit antenna. In the last step the phase differences and their associated amplitude differences are set to the factory-said values. For calibrating the transmits path of an antenna array 1 comprising at least three antennas and being connected to a digital signal processor, a method comprises the step transmitting a signal of a known amplitude and known phase by n−1 antennas and receiving these signal by the n antenna, evaluating a phase difference and an amplitude difference between each of the n−1 transmitted signals, repeating the last two steps with a new receiving antenna until every antenna has been used as a receiving antenna, compensating the phase differences and their associated amplitude differences to the factory-set values.

Claims

1. A method of calibrating a reception path of an antenna array, the antenna array being connected to a digital signal processor and comprising n≧

3 antennas, the method comprising the steps of

a) transmitting an electromagnetic signal of known amplitude and known phase by a single antenna (transmit antenna), and receiving this signal by the other n−

1 antennas (receiving antennas) of the antenna array,

b) evaluating a phase difference and an amplitude difference between each of the n−

1 received signals,

c) repeating the last two steps with a new transmit antenna until every antenna of the antenna array has been used as a transmit antenna,

d) compensating the phase differences and their associated amplitude difference to their factory-set values.

6. The method according to claim 1,

wherein it is at least partially carried out by means of a computer program.

7. The method according to claim 2,

wherein it is carried out after carrying out the method according to claim 1.

8. A computer program product, the computer program product comprising a computer readable medium, having thereon computer program code means, when said program is loaded, to make the computer executable for executing the method according to claim 1.

2. The method of calibrating a transmit path of an antenna array, the antenna array being connected to a digital signal processor and comprising n≧

3 antennas, the method comprising the steps of

a) transmitting an electromagnetic signal of known amplitude and known phase by n−

1 antennas (transmit antennas), and receiving the signals by the n-th antenna (receiving antenna),

b) evaluating a phase difference and an amplitude difference between each of the n−

1 transmitted signals,

c) repeating the last two steps with a new receiving antenna until every antenna of the antenna array has been used as a receiving antenna,

d) compensating the phase differences and their associated amplitude difference to their factory-set values.

3. The method according to claim 2,

wherein the transmit antennas are transmitting simultaneously, and that the signals of the transmit antennas are individually modulated or individually encoded.

4. The method according to claim 2,

wherein the signals transmitted by the transmit antennas are sub-carriers of an OFDM signal, and that the sub-carriers are different from each other.

5. The method according to claim 4,

wherein the sub-carriers are distributed over the whole channel bandwidth.

9. An antenna array for a wireless communication system, the antenna array being connected to a digital signal processor and comprising n≧

3 antenna, the digital signal processor having

a) means for evaluating a phase difference and an amplitude difference between a digitized signal transmitted by a first antenna of said antenna array and the same signal as transmitted by a second antenna or said antenna array, and/or means for evaluating a phase difference and an amplitude difference between a digitized signal received by a first antenna of said antenna array and the same signal as received by a second antenna or said antenna array

b) means for compensating for a phase difference and an amplitude difference as evaluated in step a) to its corresponding factory-set value.

10. The antenna array according of claim 9,

wherein it is adapted to transmit OFDM signals, in particular OFDM signals on a TDM basis.

11. The antenna array according of claim 9,

wherein the evaluation means and the compensation means are implemented in hardware or as computer programme modules.