Antenna unit and radio base station therewith

• US 6,647,276 B1
• Filed: 08/30/2000
• Issued: 11/11/2003
• Est. Priority Date: 09/14/1999
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Inoue, Takashi, Kuwahara, Mikio, Doi, Nobukazu, Ishida, Yuji, Suzuki, Toshiro, Niida, Sumaru
• Primary Examiner(s): Vo, Nguyen T.
• Assistant Examiner(s): Nguyen, Huy D
• Application Number:
  US09/650,795
• Time in Patent Office: 1,168 Days
• Field of Search: 455/562, 455/277.1, 455/278.1, 455/279.1, 455/296, 455/277.2, 455/303, 455/304, 455/226.1, 455/67.1, 375/226
• US Class Current: 455/562.1
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/20 of receivers
• 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
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

Phase and amplitude deviations, which are generated, for example, by cables connecting an array antenna of a CDMA base station and the base station, are calibrated in the baseband.

The base station comprises: an antenna apparatus 1; couplers 2; an RF unit 3 that converts a receive signal to a baseband signal, converts a transmit signal to a radio frequency, and performs power control; an A/D converter 4 for converting a receive signal to a digital signal; a receive beam form unit 6 that multiplies the receive signal by semi-fixed weight; a despreader 7 for this signal input; a time-space demodulator 8 for demodulating user data; a despreader 9 for probe signal; a space modulator 14 for user data; a spreader 13 for user signal; a channel combiner 12; a Tx calibrater 11 for controlling calibration of a signal; a D/A converter 10; a unit 16 for calculation of correlation matrix for generating a probe signal used for controlling an Rx calibration system and a TX calibration system; a spreader 17 for probe signal; a power control unit 18; a D/A converter 19; an RF unit 20 for probe signal; an A/D converter 21 for signal from the couplers 2; and a despreader 22.

Claims

1. A radio base station apparatus provided with an array antenna having a plurality of antenna elements, wherein:

a receive signal calibration system of said radio base station apparatus comprises;

a receive probe signal spreading unit which spreads a specific code series with a specific spread code;

a power control unit which performs power control on an output signal of said receive probe signal spreading unit;

a D/A converting unit for the receive probe signal, for converting an output signal of said power control unit from a digital signal to an analog signal;

a probe signal RF unit which converts an output signal of said D/A converting unit to a radio frequency and performs power control on said radio frequency;

a coupling unit which adds said probe signal to receive signals received respectively by said plurality of antenna elements, so as to generate receive signals added with probe;

an RF unit which converts the receive signals added with probe, which are generated in said coupling unit, to baseband signals;

an A/D converting unit which converts the baseband signals generated in said RF unit to digital signals;

a receive probe signal despreading unit which outputs results of despreading the signals subjected to said A/D conversion with a spread code used for the probe signal, and which outputs results of despreading said signals intentionally with a spread code that has not been used;

a correlation matrix calculation unit that obtains correlation of receive probe signals between each pair of antenna elements from the output of said receive probe signal despreading unit, calculates a signal subspace from an obtained correlation matrix, and calculates phase rotation and amplitude calibration required for an eigen vector having a maximum eigen value of the signal subspace and a predetermined vector to have a specific relation with each other; and

a receive signal calibration unit which performs calibration of the output signals of the A/D converting unit, with said output signals being converted from said baseband signals by the A/D converting unit, and with said calibration corresponding to said phase rotation and said amplitude calibration calculated by said correlation matrix calculation unit; and

said power control unit controls power of said probe signal inputted, such that the power becomes a necessity minimum required for said correlation matrix calculation unit to calculate the correlation matrix.

2. The radio base station apparatus according to claim 1, wherein:

said RF unit has a function of converting the signal subjected to the D/A conversion to a radio frequency and of inputting the converted radio frequency to each antenna element;

said coupling unit has a function of extracting a part of a transmit signal inputted to each antenna element; and

said probe signal RF unit has a function of converting a signal from said coupling unit to a baseband signal.

3. The radio base station apparatus according to claim 2, wherein:

a transmit signal calibration system of said radio base station apparatus comprises;

a transmit probe signal spreading unit which spreads a specific code series with a specific spread code;

a transmit signal calibration unit which calibrates a transmit signal generated in a modulation unit, using signals from said correlation matrix calculation unit;

a transmit signal combining unit which selectively adds an output signal of said transmit probe signal spreading unit, only to a signal to be transmitted from one antenna element out of transmit signals generated in said calibration unit, so as to generate transmit signals added with probe;

a D/A converting unit which converts an output of said transmit signal combining unit from digital signals to analog signals and for inputting said analog signals to said RF unit that converts the receive signals to the baseband signals;

an A/D converting unit for probe signal, for converting an analog signal to a digital signal, said analog signal being the baseband signal converted in said probe signal RF unit from the signal from said coupling unit; and

a transmit probe signal despreading unit which despreads an output of said A/D converting unit for probe signal with the spread code of the transmit probe signal, and for inputting the depsread output to said correlation matrix calculation unit; and

said correlation matrix calculation unit obtains correlation of transmit probe signals between each pair of antenna elements from the output of the transmit probe signal despreading unit, and calculates phase rotation and amplitude calibration required for an eigen vector having a maximum eigen value of an obtained correlation matrix and a predetermined vector to have a specific relation with each other, so as to control calibration by said calibration unit.

4. The radio base station apparatus according to claim 3, wherein:

said receive signal calibration system and said treatment signal calibration system use a same local oscillator as an oscillation source to perform up-conversion and down-conversion respectively, and use a same local oscillator as an oscillation source to perform timing generation.

5. The radio base station apparatus according to claim 4, wherein:

said transmit probe signal is not added selectively to a specific antenna element, but a signal using a different spread code for each antenna element is added to a signal of each antenna element.

6. The radio base station apparatus according to claim 3, wherein:

said transmit probe signal is not added selectively to a specific antenna element, but a signal using a different spread code for each antenna element is added to a signal of each antenna element.

7. The radio base station apparatus according to claim 3, wherein:

said receive signal calibration unit and a beam form unit for the array antenna are formed within a same unit, and said transmit signal calibration unit and a beam form unit for the array antenna are formed within a same unit.