Apparatus and method for controlling the output phase of a VCO

• US 20110043289A1
• Filed: 08/19/2009
• Published: 02/24/2011
• Est. Priority Date: 08/19/2009
• Status: Active Grant

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: Xue, Quan, Wan, Kwun Chiu
• Granted Patent: US 8,138,841 B2
• Time in Patent Office: Days
• US Class Current: 331/25
• CPC Class Codes: H03L 7/081 provided with an additional controlled phase shifter H03L7/0998 takes precedence
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

A method and apparatus controlling the output phase of a VCO (Voltage Controlled Oscillator). The apparatus has a phase locked loop 20 having a first input 21 for receiving a reference signal and a second input 22 for receiving a feedback signal and the output for controlling of a VCO. A phase shifter 50 is provided on the feedback path between the VCO and the second input of the phase locked loop. The phase shifter is arranged for shifting the phase for feedback signal by controlled amount. The phase shifter may be a variable phase shifter for controlling and varying the amount by which the phase feedback signal is shifted.

Claims

1. An apparatus for controlling the output phase of a VCO, comprising:

a phase locked loop having a first input for receiving a reference signal, a second input for receiving a feedback signal and an output for controlling a VCO;

a VCO coupled to the output of the phase locked loop;

a feedback path coupling a feedback signal from the VCO to said second input of the phase locked loop;

a phase shifter on said feedback path between the VCO and said second input of the phase locked loop, the phase shifter being arranged for shifting the phase of the feedback signal by a controlled amount;

wherein the output phase of the VCO being controlled on the basis of said reference signal and said feedback signal which has been phase shifted by said phase shifter.

2. The apparatus according to claim 1 wherein said phase shifter is a variable phase shifter for controllably varying the amount by which the phase of the feedback signal is shifted.

3. The apparatus according to claim 1 wherein the phase locked loop comprises a phase comparator having a first input for receiving a reference signal and a second input for receiving a feedback signal.

4. The apparatus of claim 1 comprising a reference oscillator for generating a reference signal, said reference oscillator being coupled to said first input of the phase locked loop.

5. The apparatus according to claim 1 wherein the VCO has an output which is coupled to an amplifier.

6. The apparatus according to claim 1 wherein the phase shifter is tunable over a range of at least 360 degrees.

7. The apparatus according to claim 1 wherein the phase shifter comprises a high pass filter and a low pas filter.

8. The apparatus of claim 1 wherein the phase shifter is a high frequency phase shifter for shifting the phase of a high frequency signal.

9. An apparatus for controlling the output phases of a plurality of VCOs, comprising:

a plurality phased locked loops, each having a first input for receiving a reference signal, a second input for receiving a feedback signal and an output for controlling a VCO;

a plurality of VCOs, each VCO being associated with and coupled to the output of a respective phase locked loop;

a plurality of feedback paths, each feedback path being between a respective VCO and its associated phase locked loop;

each feedback path having a respective phase shifter for shifting the phase of a feedback signal by a controlled amount;

wherein the output phase of each VCO being controlled on the basis of a respective reference signal and a respective feedback signal which has been phase shifted by a respective phase shifter.

10. The apparatus of claim 9 wherein said respective phase shifters are variable phase shifters for controllably varying the amount by which the phase of the feedback signal is shifted.

11. The apparatus of claim 9 comprising a plurality of amplifiers, wherein each VCO has an output coupled to a respective amplifier.

12. The apparatus of claim 9 comprising a plurality of antennas and a plurality of mixers, each antenna being coupled to a respective mixer and each VCO being coupled to a respective mixer.

13. The apparatus of claim 12 wherein said antennas are coupled to first inputs of the mixers and each VCO has an output coupled to a second input of a respective mixer;

and

wherein each mixer has an output which is coupled to a combiner.

14. A method of controlling the output phase of a VCO comprising providing a phase locked loop having a first input for receiving a reference signal, a second input for receiving a feedback signal and an output coupled to the VCO;

providing a phase shifter on a feedback path between the VCO and the second input of the phase locked loop;

injecting a reference signal into the first input of the phase locked loop, directing a feedback signal from the output of the VCO to the second input of the phase locked loop via said feedback path, shifting the phase of the feedback signal by a controlled amount with the phase shifter before said feedback signal reaches the second input of the phase locked loop and controlling the output phase of the VCO on the basis of said reference signal and said feedback signal which has been phase shifted by said phase shifter.

15. The method of claim 14 wherein said phase shifter is a variable phase shifter and further comprising the step of controlling the variable phase shifter to adjust the amount by which the phase of the feedback signal is phase shifted.

16. The method of claim 14 wherein the phase locked loop comprises a phase comparator having a first input for receiving a reference signal and a second input for receiving a feedback signal.

17. The method of claim 14 wherein the reference signal is generated by a low frequency reference oscillator.

18. The method of claim 14 wherein the variable phase shifter on the feedback loop shifts the phase of a high frequency feedback signal.

19. A method of controlling an array of antennas, wherein each antenna in said array is coupled to the output of a respective VCO and the output phase of each VCO is controlled independently according to the method of claim 14.