Method and apparatus for calibrating a smart antenna array

• US 6,236,839 B1
• Filed: 12/16/1999
• Issued: 05/22/2001
• Est. Priority Date: 09/10/1999
• Status: Expired due to Fees

• Current Assignee: UTStarcom Incorporated (UTStarcom Holdings Corp.)
• Original Assignee: UTStarcom Incorporated (UTStarcom Holdings Corp.)
• Inventors: Li, Shiping, Gu, Yucong, Yang, Zhang Ping
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): Woldetatios, Yemane
• Application Number:
  US09/464,933
• Time in Patent Office: 523 Days
• Field of Search: 455/561, 455/562, 455/129, 455/277.1, 455/277.2, 455/67.1, 455/425, 342/359, 342/360, 342/361, 342/363, 342/364, 342/365, 342/366, 342/367, 342/368, 342/369, 342/380, 342/381, 342/382, 342/384
• US Class Current: 455/67.14
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H04W 88/00 Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices

Abstract

A smart antenna system includes: an antenna array including a plurality of antenna elements, and at least one calibration element; a plurality of transceiver units each having a port coupled with an associated one of the antenna elements, a receive port, and a transmit port; a transceiver calibration unit including a port coupled with the calibration element via a coaxial cable, a receive port, and a transmit port; and signal processing means communicatively coupled with each of the receive ports and the transmit ports of each of the transceiver units, and coupled with the calibration receive port and the calibration transmit port of the calibration unit. A transmitter calibration path associated with each antenna element extends from the transmit port of the associated transceiver unit to the associated antenna element, from the associated antenna element to the calibration element, and from the calibration element to the receive port of the calibration unit. A receiver calibration path associated with each antenna element extends from the transmit port of the calibration unit to the calibration element, from the calibration element to the associated antenna element, and from the associated antenna element to the receive port of the associated transceiver unit. The signal processing means is responsive to transmit mode resultant signals developed as a result of reference signals propagating through associated transmitter calibration paths. The signal processing means is also responsive to receive mode resultant signals developed as a result of reference signals propagating through associated receiver calibration paths.

Claims

1. A smart antenna system comprising:

an antenna array including a plurality of antenna elements, and at least one antenna calibration element for radiating and receiving radiated signals to and from each of said antenna elements;

a plurality of antenna element coupling means;

a plurality of transceiver units each including an input/output port communicatively coupled with an associated one of said antenna elements via an associated one of said antenna coupling means, a receive port, and a transmit port;

a transceiver calibration unit including a calibration input/output port communicatively coupled with said calibration element, a calibration receive port, and a calibration transmit port; and

signal processing means communicatively coupled with each of said receive ports and said transmit ports of each of said transceiver units, and communicatively coupled with said calibration receive port said calibration transmit port of said calibration unit;

wherein a transmitter calibration path associated with each one of said antenna elements extends from said transmit port of said associated transceiver unit to said associated antenna element, from said associated antenna element to said calibration element, and from said calibration element to said calibration receive port of said calibration unit;

wherein a receiver calibration path associated with each one of said antenna elements extends from said calibration transmit port of said calibration unit to said calibration element, from said calibration element to said associated antenna element, and from said associated antenna element to said receive port of said associated transceiver unit;

said signal processing means being operative in a transmit calibration mode to provide a transmit mode reference signal to said transmit port of each of said transceiver units, and being responsive to transmit mode resultant signals developed as a result of associated ones of said transmit reference signals propagating through associated ones of said transmitter calibration paths, said signal processing means also being operative to determine a transmit mode calibration vector by determining amplitude differences and phase shifts between said transmit mode reference signals and said associated transmit mode resultant signals;

said signal processing means also being operative in a receive calibration mode to provide receive mode reference signals to said calibration transmit port of said calibration unit, and being responsive to receive mode resultant signals developed as a result of associated ones of said receive mode reference signals propagating through associated ones of said receiver calibration paths, said signal processing means being further operative to determine a receive mode calibration vector by determining amplitude differences and phase shifts between said receive mode reference signals and said associated receive mode resultant signals.

2. A smart antenna system as recited in claim 1 wherein said antenna elements are disposed in a generally circular array, and wherein said calibration element is disposed proximate a center point of said array.

3. A smart antenna system as recited in claim 1 wherein said input/output port of said calibration unit is communicatively coupled with said calibration element via a coaxial cable.

4. A smart antenna system as recited in claim 1 wherein each of said antenna coupling means comprises a coaxial cable.

5. A smart antenna system as recited in claim 1 wherein each of said transceiver units further comprises:

a duplexer having a first port communicatively coupled with said input/output port of said transceiver, a receive path port, and a transmit path port;

a receive processor having an input port communicatively coupled with said receive path port of said duplexer, and an output port communicatively coupled with said receive port of said transceiver unit; and

a transmit processor having an input port communicatively coupled with said transmit port of said transceiver unit, and an output port communicatively coupled with said transmit path port of said duplexer.

6. A smart antenna system as recited in claim 1 wherein said calibration unit comprises:

a duplexer having a first port communicatively coupled with said input/output port of said calibration unit, a receive path port, and a transmit path port;

a calibration receive processor having an input port communicatively coupled with said receive path port of said duplexer, and an output port communicatively coupled with said calibration receive port of said calibration unit; and

a calibration transmit processor having an input port communicatively coupled with said calibration transmit port of said calibration unit, and an output port communicatively coupled with said transmit path port of said duplexer.

7. A smart antenna system as recited in claim 6 wherein said signal processing means and each of said transceiver units are operative to transmit and receive signals carrying a plurality of channels, and wherein each of said receive mode reference signals and each of said transmit mode reference signals carries a plurality of channels.

8. A smart antenna system as recited in claim 7 wherein said calibration transmit processor further comprises:

a first digital up-converter having an input port for receiving a first portion of said channels of said receive mode reference signals from said signal processing means, and an output port; and

a second digital up-converter having a first input for receiving a second portion of said channels of said receive mode reference signals from said signal processing means, a second input port communicatively coupled with said output port of said first up-converter, and an output port;

a digital to analog converter having an input port communicatively coupled with said output port of said second up-converter, and an output port for providing analog reference signals;

a band pass filter having an input port for receiving said analog reference signals, and an output port for providing band-pass filtered signals;

a transmitter mixer having a first input port for receiving said band-pass filtered signals, a second input port for receiving a calibration reference signal, and an output port for providing a mixed signal;

a reference signal generator for providing said calibration reference signal to said second input port of said mixer, and

a preamplifier having an input port for receiving said mixed signal, and an output port communicatively coupled with said transmit path port of said duplexer.

9. A smart antenna system as recited in claim 7 wherein said calibration receive processor further comprises:

a preamplifier having an input port coupled with said receive path port of said duplexer, and an output port;

a receiver mixer having a first input port communicatively coupled with said output port of said preamplifier, a second input port for receiving a calibration reference signal, and an output port for providing a mixed signal;

a reference signal generator for providing said calibration reference signal to said second port of said mixer;

a band-pass filter having an input port for receiving said mixed signal, and an output port for providing a band-pass filtered signal; and

an analog-to-digital converter having an input port for receiving said filtered signal from said band-pass filter, and an output port providing a digital signal having a plurality of channels;

a first digital down-converter having an input port responsive to a first portion of said channels of said digital signal provided at said output port of said analog to digital converter, and an output port communicatively coupled with said signal processing means; and

a second digital down-converter having an input port responsive to a second portion of said channels of said digital signal provided at said output port of said analog to digital converter, and an output port communicatively coupled with said signal processing means.

10. A smart antenna system as recited in claim 1 wherein said signal processing means comprises:

a control processing unit having a plurality of ports communicatively coupled with said receive ports and said transmit ports of each of said transceiver units; and

a calibration processing unit communicatively coupled with said calibration receive port and said calibration transmit port of said calibration unit, and also being communicatively coupled with said control processing unit.

11. A smart antenna system as recited in claim 10 wherein said calibration processing unit and said calibration unit are enclosed in a shielded enclosure.

12. A smart antenna system comprising:

an antenna array including a plurality of antenna elements, and at least one antenna calibration element for radiating and receiving radiated signals to and from each of said antenna elements;

a plurality of antenna element coupling means;

a plurality of transceiver units each including an input/output port communicatively coupled with an associated one of said antenna elements via an associated one of said antenna coupling means, a receive port, and a transmit port;

a transceiver calibration unit including a calibration input/output port communicatively coupled with said calibration element, a calibration receive port, and a calibration transmit port; and

signal processing means communicatively coupled with each of said receive ports and said transmit ports of each of said transceiver units, and communicatively coupled with said calibration receive port and said calibration transmit port of said calibration unit;

wherein a transmitter calibration path associated with each one of said antenna elements extends from said transmit port of said associated transceiver unit to said associated antenna element, from said associated antenna element to said calibration element, and from said calibration element to said calibration receive port of said calibration unit;

said signal processing means being operative in a transmit calibration mode to provide a transmit mode reference signal to said transmit port of each of said transceiver units, and being responsive to transmit mode resultant signals developed as a result of associated ones of said transmit reference signals propagating through associated ones of said transmitter calibration paths, said signal processing means also being operative to determine a transmit mode calibration vector by determining amplitude differences and phase shifts between said transmit mode reference signals and said associated transmit mode resultant signals.

13. A smart antenna system as recited in claim 12 wherein said antenna elements are disposed in a generally circular array, and wherein said calibration element is disposed proximate a center point of said array.

14. A smart antenna system as recited in claim 12 wherein said input/output port of said calibration unit is communicatively coupled with said calibration element via a coaxial cable.

15. A smart antenna system as recited in claim 12 wherein each of said antenna coupling means comprises a coaxial cable.

16. A smart antenna system comprising:

an antenna array including a plurality of antenna elements, and at least one antenna calibration element for radiating and receiving radiated signals to and from each of said antenna elements;

a plurality of antenna element coupling means;

a plurality of transceiver units each including an input/output port communicatively coupled with an associated one of said antenna elements via an associated one of said antenna coupling means, a receive port, and a transmit port;

a transceiver calibration unit including a calibration input/output port communicatively coupled with said calibration element, a calibration receive port, and a calibration transmit port; and

signal processing means communicatively coupled with each of said receive ports and said transmit ports of each of said transceiver units, and communicatively coupled with said calibration receive port and said calibration transmit port of said calibration unit;

wherein a receiver calibration path associated with each one of said antenna elements extends from said calibration transmit port of said calibration unit to said calibration element, from said calibration element to said associated antenna element, and from said associated antenna element to said receive port of said associated transceiver unit;

said signal processing means being operative in a receive calibration mode to provide receive mode reference signals to said calibration unit port of said calibration unit, and being responsive to receive mode resultant signals developed as a result of associated ones of said receive mode reference signals propagating through associated ones of said receiver calibration paths, said signal processing means being further operative to determine a receive mode calibration vector by determining amplitude differences and phase shifts between said receive mode reference signals and said associated receive mode resultant signals.

17. A smart antenna system as recited in claim 16 wherein said antenna elements are disposed in a generally circular array, and wherein said calibration element is disposed proximate a center point of said array.

18. A smart antenna system as recited in claim 16 wherein said input/output port of said calibration unit is communicatively coupled with said calibration element via a coaxial cable.

19. A smart antenna system as recited in claim 16 wherein each of said antenna coupling means comprises a coaxial cable.