Integrated voltage-controlled oscillator circuits

• US 8,031,019 B2
• Filed: 02/02/2009
• Issued: 10/04/2011
• Est. Priority Date: 02/02/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chawla, Vipul, Wang, Shen
• Primary Examiner(s): Gannon; Levi
• Application Number:
  US12/363,911
• Publication Number:
  US 20100194485A1
• Time in Patent Office: 974 Days
• Field of Search: 331/37, 331/40, 331/41, 331/117.FE, 331/117.R, 331/167, 331/177.V, 331/36.C, 455/118, 455/119, 455/258, 455/262, 455/313, 455/318, 455/319, 455/323, 455/325, 455/326, 455/333
• US Class Current: 331/117.0FE
• CPC Class Codes: H03B 5/1215 the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair
• CPC Class Codes: H03B 5/1218 the generator being of the balanced type
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes
• CPC Class Codes: H03B 5/1296 the feedback circuit comprising a transformer

Abstract

Techniques for providing voltage-controlled oscillator circuits having improved phase noise performance and lower power consumption. In an exemplary embodiment, a voltage controlled oscillator (VCO) is coupled to a mixer or a frequency divider such as a divide-by-two circuit. The VCO includes a transistor pair with magnetically cross-coupled inductors, and variable capacitance coupled to the gates of the transistor pair. In an exemplary embodiment, a frequency divider is configured to divide the frequency of the differential current flowing through the transistor pair to generate the LO output. In an alternative exemplary embodiment, a mixer is configured to mix the differential current flowing through the transistor pair with another signal. The VCO and mixer or frequency divider share common bias currents, thereby reducing power consumption. Various exemplary apparatuses and methods utilizing these techniques are disclosed.

Claims

1. An apparatus comprising a voltage controlled oscillator (VCO) coupled to a mixer, the VCO comprising:

a first transistor configured to be DC biased by a first bias current;

a second transistor configured to be DC biased by a second bias current;

at least one gate inductance coupling the gate of the first transistor to the gate of the second transistor;

a first drain inductance magnetically coupled to the at least one gate inductance, the first drain inductance coupled to the drain of the first transistor;

a second drain inductance magnetically coupled to the at least one gate inductance, the second drain inductance coupled to the drain of the second transistor; and

at least one variable capacitance coupling the gate of the first transistor to the gate of the second transistor,

the mixer comprising first and second input nodes coupled to the first and second drain inductances, respectively, the mixer configured to be biased by the first and second bias currents, the at least one gate inductance being formed by a primary coil, the first and second drain inductances being formed by two secondary coils, and the two secondary coils being laid out inside or stacked underneath the primary coil.

2. The apparatus of claim 1, the mixer configured to mix the differential current flowing through the first and second nodes with a second signal to generate a mixed output signal.

3. The apparatus of claim 2, the second signal comprising a baseband signal, the mixed output signal comprising an upconverted signal.

4. The apparatus of claim 2, the mixed output signal being a local oscillator signal.

5. The apparatus of claim 2, the first and second gate inductances and the first and second drain inductances being formed by a single transformer.

6. The apparatus of claim 2, the second signal comprising a received radio frequency (RF) signal.

7. The apparatus of claim 1, the at least one gate inductance comprising a first gate inductance and a second gate inductance, the first gate inductance coupling the gate of the first transistor to a DC voltage, the second gate inductance coupling the gate of the second transistor to the DC voltage, the first gate inductance magnetically coupled to the second drain inductance, the second gate inductance magnetically coupled to the first drain inductance.

8. The apparatus of claim 1, the at least one variable capacitance comprising a varactor.

9. The apparatus of claim 1, the at least one variable capacitance comprising a switchable capacitor bank.

10. A method for generating a mixed signal, the method comprising:

DC biasing a first transistor using a first bias current;

DC biasing a second transistor using a second bias current;

coupling the gate of the first transistor to the gate of the second transistor using at least one gate inductance;

magnetically coupling a first drain inductance to the at least one gate inductance, the first drain inductance coupled to the drain of the first transistor;

magnetically coupling a second drain inductance to the at least one gate inductance, the second drain inductance coupled to the drain of the second transistor;

selecting the capacitance of a variable capacitance element coupling the gate of the first transistor to the gate of the second transistor;

mixing the differential current flowing in the first and second drain inductances with another signal using a mixer to generate at least one mixed signal; and

biasing the mixer using the first and second bias currents,

wherein the at least one gate inductance is formed by a primary coil, wherein the first and second drain inductances are formed by two secondary coils, and wherein the two secondary coils are laid out inside or stacked underneath the primary coil.

11. The method of claim 10, the at least one gate inductance comprising a first gate inductance and a second gate inductance, the first gate inductance coupling the gate of the first transistor to a DC voltage, the second gate inductance coupling the gate of the second transistor to the DC voltage, the magnetically coupling the first drain inductance to a gate inductance comprising magnetically coupling the first drain inductance to the second gate inductance, the magnetically coupling the second drain inductance to a gate inductance comprising magnetically coupling the second drain inductance to the first gate inductance.

12. The method of claim 10, the selecting the capacitance comprising varying the voltage across a varactor.

13. The method of claim 10, the selecting the capacitance comprising switching capacitors in a capacitor bank.

14. The method of claim 10, the mixing comprising mixing the differential current flowing in the first and second drain inductances with a received radio-frequency (RF) signal.

15. The method of claim 10, the mixing comprising mixing the differential current flowing in the first and second drain inductances with a baseband signal, the generated mixed signal comprising an upconverted signal.

16. The method of claim 10, the generated mixed signal being a local oscillator signal.

17. An apparatus comprising:

means for generating a differential voltage controlled oscillator (VCO) output current having a voltage-controlled frequency, the means for generating comprising a VCO, the VCO configured to be biased by at least one bias current; and

means for mixing the VCO output current with another signal, wherein the means for mixing is configured to share the at least one bias current with the VCO, the VCO comprising;

a first transistor;

a second transistor;

at least one gate inductance coupling the gate of the first transistor to the gate of the second transistor;

a first drain inductance coupled to the drain of the first transistor; and

a second drain inductance coupled to the drain of the second transistor, wherein the at least one gate inductance is formed by a primary coil, wherein the first and second drain inductances are formed by two secondary coils, and wherein the two secondary coils are laid out inside or stacked underneath the primary coil.

18. A device for wireless communications, the device comprising a TX LO signal generator, at least one baseband TX amplifier, an upconverter coupled to the TX LO signal generator and the at least one baseband TX amplifier, a TX filter coupled to the output of the upconverter, a power amplifier (PA) coupled to the TX filter, an RX LO signal generator, an RX filter, a downconverter coupled to the RX LO signal generator and the RX filter, a low-noise amplifier (LNA) coupled to the RX filter, and a duplexer coupled to the PA and the LNA, the TX LO signal generator and upconverter comprising a voltage controlled oscillator (VCO) coupled to a mixer, the VCO comprising:

a first transistor configured to be DC biased by a first bias current;

a second transistor configured to be DC biased by a second bias current;

at least one gate inductance coupling the gate of the first transistor to the gate of the second transistor;

a first drain inductance magnetically coupled to the at least one gate inductance, the first drain inductance coupled to the drain of the first transistor;

a second drain inductance magnetically coupled to the at least one gate inductance, the second drain inductance coupled to the drain of the second transistor; and

at least one variable capacitance coupling the gate of the first transistor to the gate of the second transistor,

the mixer comprising first and second input nodes coupled to the first and second drain inductances, respectively, the mixer configured to be biased by the first and second bias currents, the at least one gate inductance being formed by a primary coil, the first and second drain inductances being formed by two secondary coils, and the two secondary coils being laid out inside or being stacked underneath the primary coil.

19. A device for wireless communications, the device comprising a TX LO signal generator, at least one baseband TX amplifier, an upconverter coupled to the TX LO signal generator and the at least one baseband TX amplifier, a TX filter coupled to the output of the upconverter, a power amplifier (PA) coupled to the TX filter, an RX LO signal generator, an RX filter, a downconverter coupled to the RX LO signal generator and the RX filter, a low-noise amplifier (LNA) coupled to the RX filter, and a duplexer coupled to the PA and the LNA, the RX LO signal generator and downconverter comprising a voltage controlled oscillator (VCO) coupled to a mixer, the VCO comprising:

a first transistor configured to be DC biased by a first bias current;

a second transistor configured to be DC biased by a second bias current;

at least one gate inductance coupling the gate of the first transistor to the gate of the second transistor;

a first drain inductance magnetically coupled to the at least one gate inductance, the first drain inductance coupled to the drain of the first transistor;

a second drain inductance magnetically coupled to the at least one gate inductance, the second drain inductance coupled to the drain of the second transistor; and

at least one variable capacitance coupling the gate of the first transistor to the gate of the second transistor,

the mixer comprising first and second input nodes coupled to the first and second drain inductances, respectively, the mixer configured to be biased by the first and second bias currents, the at least one gate inductance being formed by a primary coil, the first and second drain inductances being formed by two secondary coils, and the two secondary coils being laid out inside or being stacked underneath the primary coil.