Phase Shifter

• US 20080032639A1
• Filed: 06/29/2007
• Published: 02/07/2008
• Est. Priority Date: 08/04/2006
• Status: Active Grant

• Current Assignee: Axiom Microdevices Incorporated (Skyworks Solutions Incorporated)
• Original Assignee: Axiom Microdevices Incorporated (Skyworks Solutions Incorporated)
• Inventors: Aoki, Ichiro, Kee, Scott D., Feng, Weifeng
• Granted Patent: US 7,756,491 B2
• Time in Patent Office: Days
• US Class Current: 455/110
• CPC Class Codes: H03F 1/3282 Acting on the phase and the amplitude of the input signal
• CPC Class Codes: H03F 2203/45228 A transformer being added at the output or the load circuit of the dif amp
• CPC Class Codes: H03F 2203/45731 the LC comprising a transformer
• CPC Class Codes: H03H 11/20 Two-port phase shifters providing an adjustable phase shift
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00

Abstract

A phase shifter includes a plurality of variable gain elements, each variable gain element configured to receive one of a plurality of input signals, each input signal having a phase that is shifted with respect to each other input signal; and a control signal supplied to each variable gain element, where the control signals define a phase shift.

Claims

1. A phase shifter, comprising:

a plurality of variable gain elements, each variable gain element configured to receive one of a plurality of input signals, each input signal having a phase that is shifted with respect to each other input signal; and

a control signal supplied to each variable gain element, the control signals defining a phase shift.

2. The phase shifter of claim 1, further comprising a polyphase filter configured to generate the plurality of input signals as quadrature input signals.

3. The phase shifter of claim 1, further comprising a frequency divider configured to generate the plurality of input signals as quadrature input signals.

4. The phase shifter of claim 1, in which each of the variable gain elements provides positive gain.

5. The phase shifter of claim 4, in which each variable gain element further comprises:

a switching transistor;

a gain control transistor coupled to the switching transistor, the gain control transistor also configured to receive the control signal; and

wherein the gain control transistor controls the amount of current flowing through the gain control transistor when the switching transistor is active as a function of the gate-source voltage of the gain control transistor.

6. The phase shifter of claim 4, in which each variable gain element further comprises:

an amplifying transistor;

an input signal coupled to the amplifying transistor through a capacitor; and

a gain control signal coupled to the amplifying transistor and configured to adjust the gain of the input signal through the amplifying transistor while preserving amplitude modulation of the input signal.

7. The phase shifter of claim 5, in which each variable gain element is configured to operate on differential input signals.

8. The phase shifter of claim 7, in which each variable gain element further comprises:

a pair of differential amplifying transistors;

an input signal coupled to the amplifying transistors through a respective capacitor; and

a gain control signal coupled to the amplifying transistors and configured to adjust the gain of the input signal through the amplifying transistors while preserving amplitude modulation of the input signal.

9. The phase shifter of claim 1, further comprising a control circuit configured to supply the control signal, the control circuit comprising:

a plurality of differential pair transistors configured to receive differential components of a control voltage signal (vctrl) and configured to provide differential components of the control signal.

10. A method for altering the phase of a signal, comprising:

providing quadrature components of a phase signal to a respective plurality of variable gain elements,

providing a control signal to each of the variable gain elements, each control signal corresponding to a quadrature-phase of the quadrature component provided to the variable gain element; and

altering an amplitude of each quadrature component based on the value of the control signal.

11. The method of claim 10, further comprising generating the quadrature components of the phase signal using a polyphase filter.

12. The method of claim 10, further comprising generating the quadrature components of the phase signal using a frequency divider.

13. The method of claim 10, further comprising controlling a gain of the variable gain amplifier by controlling current flow through a gain control transistor when a switching transistor is active as a function of the gate-source voltage of the gain control transistor.

14. The method of claim 10, further comprising implementing a resistive-capacitive filter at the input of the variable gain element to preserve amplitude modulation at an input to the variable gain amplifier.

15. A portable transceiver having a phase shifter, comprising:

a transmitter coupled to a receiver;

a power amplifier associated with the transmitter, the power amplifier having a linear control characteristic, the power amplifier configured to amplify a phase-modulated (PM) signal according to the amplitude of an amplitude-modulated (AM) signal;

a feedback signal taken from the power amplifier;

a limiter configured to receive the feedback signal;

a phase shifter comprising;

a plurality of variable gain elements, each variable gain element configured to receive one of a plurality of input signals, each input signal having a phase that is shifted with respect to each other input signal; and

a control signal supplied to each variable gain element, the control signals defining a phase shift.

16. The portable transceiver of claim 15, in which each of the variable gain elements provides positive gain.

17. The portable transceiver of claim 16, in which each variable gain element further comprises:

a switching transistor;

a gain control transistor coupled to the switching transistor, the gain control transistor also configured to receive the control signal; and

wherein the gain control transistor controls the amount of current flowing through the gain control transistor when the switching transistor is active as a function of the gate-source voltage of the gain control transistor.

18. The portable transceiver of claim 17, in which each variable gain element further comprises:

an amplifying transistor;

an input signal coupled to the amplifying transistor through a capacitor; and

a gain control signal coupled to the amplifying transistor and configured to adjust the gain of the input signal through the amplifying transistor while preserving amplitude modulation of the input signal.

19. The portable transceiver of claim 18, in which each variable gain element is configured to operate on differential input signals.

20. The portable transceiver of claim 15, further comprising a control circuit configured to supply the control signal, the control circuit comprising:

a plurality of differential pair transistors configured to receive differential components of a control voltage signal (vctrl) and configured to provide differential components of the control signal.