Split channel receiver with very low second order intermodulation

• US 8,073,078 B2
• Filed: 02/08/2008
• Issued: 12/06/2011
• Est. Priority Date: 02/08/2008
• Status: Expired due to Fees

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Kaczman, Daniel L., Shah, Manish N.
• Primary Examiner(s): Payne, David C.
• Assistant Examiner(s): Dsouza, Adolf
• Application Number:
  US12/028,623
• Publication Number:
  US 20090202022A1
• Time in Patent Office: 1,397 Days
• Field of Search: None
• US Class Current: 375/316
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal
• CPC Class Codes: H04L 27/3872 Compensation for phase rotation in the demodulated signal

Abstract

A high performance radio frequency receiver includes an isolated transconductance amplifier with large binary and stepped gain control range, controlled impedance, and enhanced blocker immunity, for amplifying and converting a radio frequency signal to multiple electrically isolated currents; a pulse generator for generating in-phase and quadrature pulses; a crossover correction circuit and pulse shaper for controlling a crossover threshold of the pulses and interaction between in-phase and quadrature mixers; and a double balanced mixer for combining the RF signal with the pulses to generate an intermediate frequency or baseband zero intermediate frequency current-mode signal. The intermediate frequency signal and second order harmonics may be filtered with a high frequency low pass filter and a current injected complex direct-coupled filter. IIP2 calibration of the in-phase and quadrature channels may be optimized using the isolated transconductance amplifier.

Claims

1. A radio frequency receiver, comprising:

a transconductance amplifier operable to amplify and convert a first received voltage of a first radio frequency signal to first and second currents that are electrically isolated;

a pulse generator operable to generate in-phase and quadrature pulses;

a mixer operable to combine the first current with the in-phase pulses to produce a third current comprising an in-phase signal; and

combine the second current with the quadrature pulses to produce a fourth current comprising a quadrature signal; and

a filter operable to filter the third and fourth currents to filtered voltage signals;

where the transconductance amplifier comprises separate cascode stages isolating the first and second currents.

2. The radio frequency receiver of claim 1, where the in-phase and quadrature pulses have a duty cycle of 35% or less.

3. The radio frequency receiver of claim 1, where a rise time and a fall time of the in-phase and quadrature pulses are adjusted to reduce the amount of time the in-phase and quadrature pulses are simultaneously active.

4. The radio frequency receiver of claim 1 where the mixer comprises a passive double balanced mixer and the filter comprises a direct coupled complex filter.

5. The radio frequency receiver of claim 1 where the transconductance amplifier is further operable to amplify and convert the first received voltage of the radio frequency signal to the amplified current using one or more of step weighting or binary weighting.

6. The radio frequency receiver of claim 1, further comprising a third digital-to-analog converter operable to convert a digital control signal to a DC offset correction signal, the DC offset correction signal operable to adjust a DC offset of the filtered voltage signals.

7. The radio frequency receiver of claim 1 where the amplifier is further operable to receive a calibration tone, the calibration tone usable to measure an IIP2 level of the receiver.

8. A radio frequency receiver, comprising:

a transconductance amplifier operable to amplify and convert a first received voltage of a first radio frequency signal to first and second currents that are electrically isolated;

a pulse generator operable to generate in-phase and quadrature pulses;

a mixer operable to combine the first current with the in-phase pulses to produce a third current comprising an in-phase signal; and

combine the second current with the quadrature pulses to produce a fourth current comprising a quadrature signal;

a filter operable to filter the third and fourth currents to filtered voltage signals;

a first digital-to-analog converter operable to convert a first digital control signal to an in-phase second order input intercept point (IIP2) calibration signal configured to adjust an in-phase IIP2 level; and

a second digital-to-analog converter operable to convert a second digital control signal to a quadrature IIP2 calibration signal configured to adjust a quadrature IIP2 level; and

where adjustment of the in-phase IIP2 level does not affect the quadrature IIP2 level, adjustment of the quadrature IIP2 level does not affect the in-phase IIP2 level, and the mixer is further operable to combine the first current with the in-phase pulses and the in-phase IIP2 calibration signal to produce the third current and combine the second current with the quadrature pulses and the quadrature IIP2 calibration signal to produce the fourth current.

9. The radio frequency receiver of claim 8, where the transconductance amplifier comprises separate cascode stages isolating the first and second currents.

10. A radio frequency receiver, comprising:

a transconductance amplifier operable to amplify and convert a first received voltage of a first radio frequency signal to first and second currents that are electrically isolated;

a pulse generator operable to generate in-phase and quadrature pulses;

a mixer operable to combine the first current with the in-phase pulses to produce a third current comprising an in-phase signal; and

combine the second current with the quadrature pulses to produce a fourth current comprising a quadrature signal;

a filter operable to filter the third and fourth currents to filtered voltage signals; and

a crossover correction circuit operable to control a crossover threshold of the in-phase and quadrature pulses and where the crossover threshold comprises a crossing point of an amplitude of the in-phase and quadrature pulses, the crossing point selected to reduce the amount of time the in-phase and quadrature pulses are simultaneously active, and where the double balanced mixer comprises transistors and the crossover correction circuit is operable to bias a control terminal voltage of the transistors to select the crossing point.

11. A radio frequency receiver, comprising:

a transconductance amplifier operable to amplify and convert a first received voltage of a first radio frequency signal to first and second currents that are electrically isolated;

a pulse generator operable to generate in-phase and quadrature pulses;

a mixer operable to combine the first current with the in-phase pulses to produce a third current comprising an in-phase signal; and

combine the second current with the quadrature pulses to produce a fourth current comprising a quadrature signal; and

a filter operable to filter the third and fourth currents to filtered voltage signals;

where the amplifier comprises;

a first transistor with a control terminal in communication with the first received voltage and a current terminal in communication with a first node;

a second transistor operable to generate the first current, and with a first current terminal in communication with the first node and a second current terminal in communication with a first load; and

a third transistor operable to generate the second current, and with a first current terminal in communication with the first node and a second current terminal in communication with a second load.

12. The radio frequency receiver of claim 11, where the first current is generated at the second current terminal of the second transistor, and the second current is generated at the second current terminal of the third transistor.

13. The radio frequency receiver of claim 11, where the amplifier is further operable to amplify and convert a second received voltage of a second radio frequency signal to the first and second currents, and where the amplifier further comprises a fourth transistor with a control terminal in communication with a second received voltage and a current terminal in communication with the first node.

14. The radio frequency receiver of claim 11, where the amplifier is further operable to amplify and convert a second received voltage of a second radio frequency signal to the first and second currents, and where the amplifier further comprises:

a fifth transistor with a control terminal in communication with the second received voltage and a current terminal in communication with a second node;

a sixth transistor operable to generate the first current, and with a first current terminal in communication with the second node and a second current terminal in communication with the first load; and

a seventh transistor operable to generate the second current, and with a first current terminal in communication with the second node and a second current terminal in communication with the second load.

15. The radio frequency receiver of claim 14, where the first current is generated at the second current terminal of the second transistor and the second current terminal of the sixth transistor, and the second current is generated at the second current terminal of the third transistor and the second current terminal of the seventh transistor.

16. A method of receiving a first radio frequency signal, comprising:

converting and amplifying a first voltage of the first radio frequency signal to an amplified current, the amplified current comprising a first current and a second current that are electrically isolated;

generating in-phase pulses and quadrature pulses;

mixing the first current with the in-phase pulses to produce an in-phase signal;

mixing the second current with the quadrature pulses to produce a quadrature signal;

where converting and amplifying the first voltage comprises splitting a current before separate cascode stages of a transconductance amplifier.

17. The method of claim 16, where the in-phase and quadrature pulses have a duty cycle of 35% or less.

18. The method of claim 16, further comprising adjusting a rise time and a fall time of the in-phase and quadrature pulses to reduce the amount of time the in-phase and quadrature pulses are simultaneously active.

19. The method of claim 16, further comprising selecting a crossing point of the in-phase pulses and the quadrature pulses to reduce the amount of time the in-phase pulses and quadrature pulses are simultaneously active.

20. The method of claim 16, further comprising step weighting and binary weighting the amplification of the voltage of the radio frequency signal to the amplified current.

21. A method of receiving a first radio frequency signal, comprising:

converting and amplifying a first voltage of the first radio frequency signal to an amplified current, the amplified current comprising a first current and a second current that are electrically isolated;

generating in-phase pulses and quadrature pulses;

mixing the first current with the in-phase pulses to produce an in-phase signal;

mixing the second current with the quadrature pulses to produce a quadrature signal;

converting a first digital control signal to an in-phase second order input intercept point (IIP2) calibration signal configured to adjust an in-phase IIP2 level;

converting a second digital control signal to a quadrature IIP2 calibration signal configured to adjust a quadrature IIP2 level;

mixing the first current with the in-phase pulses and the in-phase IIP2 calibration signal to produce the in-phase signal; and

mixing the second current with the quadrature pulses and the quadrature IIP2 calibration signal to produce the quadrature signal.

22. The method of claim 21, where adjusting the in-phase IIP2 level does not affect the quadrature IIP2 level, and adjusting the quadrature IIP2 level does not affect the in-phase IIP2 level.

23. The method of claim 21, where converting and amplifying the first voltage comprises splitting a current before separate cascode stages of a transconductance amplifier.

24. A radio frequency receiver, comprising:

a transconductance amplifier operable to amplify and convert a received voltage of a radio frequency signal to an amplified current, the amplified current comprising a first current and a second current that are electrically isolated, the amplifier configured to step weight and binary weight the amplification;

a pulse generator operable to generate in-phase and quadrature pulses based on a periodic signal, the in-phase and quadrature pulses having a duty cycle of 35% of less and comprising a first pulse zero degrees out of phase from the periodic signal, a second pulse one hundred eighty degrees out of phase from the periodic signal, a third pulse ninety degrees out of phase from the periodic signal, and a fourth pulse two hundred seventy degrees out of phase from the periodic signal;

a crossover correction circuit operable to control an amplitude crossover threshold of the in-phase and quadrature pulses, such that the in-phase and quadrature pulses are not active simultaneously; and

a mixer operable to combine the first current with the in-phase pulses to produce a third current comprising an in-phase signal; and

combine the second current with the quadrature pulses to produce a fourth current comprising a quadrature signal.