PHASED ARRAY ANTENNA AND ITS PHASE CALIBRATION METHOD

• US 20120146841A1
• Filed: 12/08/2011
• Published: 06/14/2012
• Est. Priority Date: 12/09/2010
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ookawa, Kunihiko
• Granted Patent: US 8,593,337 B2
• Time in Patent Office: Days
• US Class Current: 342/174
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H01Q 3/36 with variable phase-shifters

Abstract

A phased array antenna includes an oscillator, a plurality of antenna elements, a phase shifter, a distributor, a receiver, and a control processor. The control processor performs a first calibration process to calibrate a phase of the phase shifter connected to a pair of antenna elements that is selected from the antenna elements and are located at a pair of positions symmetric with respect to a central axis of an array formed by the phased array antenna, and a second calibration process to calibrate a phase of the phase shifter connected to a pair of target antenna elements with respect to a phase of the phase shifter connected to a reference antenna elements located at a central portion of the array. The pair of target antenna elements are located at a pair of positions that are symmetric with respect to the central axis of the array.

Claims

1. A phased array antenna, comprising:

an oscillator that generates radio waves;

a plurality of antenna elements that radiates radio waves;

a phase shifter that is connected to each of the plurality of antenna elements and changes a phase of radio waves radiated by the plurality of antenna elements;

a distributor that distributes radio waves generated by the oscillator to the plurality of antenna elements via the phase shifter;

a receiving unit that receives radio waves radiated by the plurality of antenna elements; and

a control processor that performs

a first calibration process to calibrate a phase of the phase shifter connected to a pair of antenna elements that is selected from the plurality of antenna elements and is located at a pair of positions symmetric with respect to a central axis of an array formed by the phased array antenna, and

a second calibration process to calibrate a phase of the phase shifter connected to a pair of target antenna elements with respect to a phase of the phase shifter connected to a reference antenna elements located at a central portion of the array, the pair of target antenna elements being located at a pair of positions that are symmetric with respect to the central axis of the array.

2. A phased array antenna according to claim 1, wherein

the control processor performs the second calibration process to:

select, from the plurality of antenna elements, a reference antenna element located at a position on the central axis of the array and a pair of target antenna elements that are selected from the plurality of antenna elements and are located at positions symmetric with respect to the central axis of the array to allow the radio waves generated by the oscillator to be provided for the reference antenna element and the pair of target antenna elements via the distributor;

obtain a directivity pattern formed by the reference antenna element and the pair of target antenna elements from a distribution in a received power of radio waves received at the receiving unit along a horizontal direction with respect to an array direction of the plurality of antenna elements, when a phase of the phase shifter connected to the reference antenna element is fixed and a phase of the phase shifter connected to the pair of target antenna elements is changed;

extract, from the directivity pattern obtained, a phase of the phase shifter connected to the pair of target antenna elements at which a level of side lobes, which occurs in the directivity pattern obtained, becomes a predetermined value; and

set the phase obtained to a phase value for the phase of the phase shifter connected to the pair of target antenna elements with respect to the phase of the phase shifter connected to the reference antenna element.

3. The phased array antenna according to claim 2, wherein

the control processor repeats the second calibration process while changing the pair of target antenna elements until the phase values for all of the pair of target antenna elements are set.

4. The phased array antenna according to claim 3, wherein

the number of antenna elements that form the array of the phased array antenna is odd, and

the reference antenna element is an antenna element located at a position on the center of the array.

5. The phased array antenna according to claim 3, wherein

the number of antenna elements that form the array of the phased array antenna is even, and

the reference antenna element is a pair of antenna elements located at a pair of positions that are the nearest to the central axis among a pair of positions symmetric with respect to the center axis of the array.

6. The phased array antenna according to claim 2, wherein

the control processor performs the first calibration process to:

select, from the plurality of antenna elements, the pair of antenna elements located at the pair of positions that are symmetric with respect to a central axis of an array formed by the phased array antenna to allow the radio waves generated by the oscillator to be provided for the pair of antenna elements;

obtain a pattern of a change in a received power of radio waves received at the receiving unit, while a phase of the phase shifter connected to one of the pair of antenna element is fixed and a phase of the phase shifter connected to the other of the pair of antenna elements is changed;

detect, from the pattern obtained, a phase difference between phases of the phase shifter at a null point where a null occurs in the pattern; and

calibrate the phase of the phase shifter based on the phase difference detected.

7. A phase calibration method for a phased array antenna that comprises an oscillator that generates radio waves, a plurality of antenna elements that radiates radio waves, a phase shifter that is connected to each of the plurality of antenna elements and changes a phase of radio waves radiated by the plurality of antenna elements, a distributor that distributes radio waves generated by the oscillator to the plurality of antenna elements via the phase shifter, a receiving unit that receives radio waves radiated by the plurality of antenna elements, and a control processor that performs a calibration process for the phased array antenna, the phase calibration method comprising:

at the control processor,

performing a first calibration process to calibrate a phase of the phase shifter connected to a pair of antenna elements that is selected from the plurality of antenna elements and is located at a pair of positions symmetric with respect to a central axis of an array formed by the phased array antenna, and

performing a second calibration process to calibrate a phase of the phase shifter connected to a pair of target antenna elements with respect to a phase of the phase shifter connected to a reference antenna elements located at a central portion of the array, the pair of target antenna elements being located at a pair of positions that are symmetric with respect to the central axis of the array.

8. The phase calibration method according to claim 7, wherein

the second calibration process includes:

selecting, from the plurality of antenna elements, a reference antenna element located at a position of the central axis of the array and a pair of target antenna elements that are selected from the plurality of antenna elements and are located at positions symmetric with respect to the central axis of the array to allow the radio waves generated by the oscillator to be provided for the reference antenna element and the pair of target antenna elements via the distributor;

obtaining a directivity pattern formed by the reference antenna element and the pair of target antenna elements from a distribution in a received power of the radio waves received at the receiving unit along a horizontal direction with respect to an array direction of the plurality of antenna elements, when a phase of the phase shifter connected to the reference antenna element is fixed and a phase of the phase shifter connected to the pair of target antenna elements is changed;

extracting, from the directivity pattern obtained, a phase of the phase shifter connected to the pair of target antenna elements at which a level of side lobes, which occur in the directivity pattern obtained, becomes a predetermined value;

setting the phase obtained to a phase value for the phase of the phase shifter connected to the pair of target antenna elements with respect to the phase of the phase shifter connected to the reference antenna element.

9. The phase calibration method according to claim 8, further comprising:

repeating, at the control processor, the second calibration process while changing the pair of target antenna elements until the phase values for all of the pair of target antenna elements are set.

10. The phase calibration method according to claim 9, wherein

the number of antenna elements that form the array of the phased array antenna is odd, and

the reference antenna element is an antenna element located at a position on the central of the array.

11. The phase calibration method according to claim 9, wherein

the number of antenna elements that form the array of the phased array antenna is even, and

the reference antenna element is a pair of antenna elements located at a pair of positions that are the nearest to the central axis among a pair of positions symmetric with respect to the center axis of the array.

12. The phase calibration method according to claim 8, wherein

the control processor performs the first calibration process to:

select, from the plurality of antenna elements, the pair of antenna elements located at the pair of positions that are symmetric with respect to a central axis of an array formed by the phased array antenna to allow the radio waves generated by the oscillator to be provided for the pair of antenna elements,

obtain a pattern of a change in a received power of the radio waves received at the receiving unit, when a phase of the phase shifter connected to one of the pair of antenna element is fixed and a phase of the phase shifter connected to the other of the pair of antenna elements is changed,

detect, from the pattern obtained, a phase difference between phases of the phase shifter at a null point where a null occurs in the pattern, and

calibrate the phase of the phase shifter based on the phase difference detected.