Intelligent control of receiver linearity based on interference

• US 6,311,048 B1
• Filed: 09/24/1998
• Issued: 10/30/2001
• Est. Priority Date: 09/24/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Conexant Systems Incorporated (Synaptics Incorporated)
• Inventors: Loke, Aravind
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): NGUYEN, DUC M
• Application Number:
  US09/160,613
• Time in Patent Office: 1,132 Days
• Field of Search: 455/136, 455/574, 455/38.3, 455/68, 455/69, 455/70, 455/245.1, 455/250.1, 455/343, 455/240.1, 455/522, 455/127, 455/76, 455/232.1, 455/246.1, 455/234.1, 330/149
• US Class Current: 455/245.1
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input

Abstract

A method and system for intelligently controlling the linearity of an RF receiver by selectively increasing the effective third-order intercept point (IP3) value of a low noise amplifier (LNA)/mixer channel only when needed. A control signal is generated based on mode of operation (receive mode); received signal strength information (RSSI); transmit channel output power, as indicated by a Tx automatic gain control (AGC) signal; and the true received signal strength, as indicated by the pilot signal-to-noise ratio in a CDMA system. The control signal is then used to selectively increase the bias current—and thus linearity—of the LNA/mixer channel, or to select one of several LNAs having differing IP3 values to effectively increase the linearity of the LNA/mixer channel.

Claims

1. A method for intelligently controlling the linearity of a receiver in a radio frequency transceiver, including the steps of:

(a) determining if the transceiver is in a receive mode, and if interference is present in the receiver, and if transmit power within the transceiver is high, and if receiver power within the transceiver is low; and

(b) controlling the effective third-order intercept point (IP3) value of a low noise amplifier (LNA)/mixer channel within the receiver in response to such determinations.

2. The method of claim 1, wherein determining if interference is present in the receiver includes the step of determining if a received signal strength information signal indicating the apparent strength of a signal received by the transceiver is significantly greater than the true received signal strength.

3. The method of claim 2, further including the step of determining the true received signal strength as a pilot signal-to-noise ratio.

4. The method of claim 1, wherein determining if transmit power within the transceiver is high includes the step of comparing a transmit channel automatic gain control signal within the transceiver to a selected threshold value.

5. The method of claim 1, wherein determining if receiver power within the transceiver is low includes the step of comparing a received signal strength information signal indicating the apparent strength of a signal received by the transceiver to a selected threshold value.

6. The method of claim 1, wherein determining if receiver power within the transceiver is low includes the step of comparing a pilot signal-to-noise ratio signal indicating the true strength of a signal received by the transceiver to a selected threshold value.

7. The method of claim 1, wherein the transceiver is a code division multiple access transceiver.

8. The method of claim 1, wherein controlling the effective IP3 value of the LNA/mixer channel includes increasing bias current to the LNA/mixer channel.

9. The method of claim 1, wherein controlling the effective IP3 value of the LNA/mixer channel includes selecting one of several LNAs having differing IP3 values.

10. A method for intelligently controlling the linearity of a receiver in a radio frequency transceiver, including the steps of:

(a) determining;

(1) if the transceiver is in a receive mode; and

(2) if interference is present in the receiver by determining if a received signal strength information signal indicating the apparent strength of a signal received by the transceiver is significantly greater than the true received signal strength;

(3) if transmit power within the transceiver is high by comparing a transmit channel automatic gain control signal within the transceiver to a selected threshold value;

(4) if receiver power within the transceiver is low by comparing a pilot signal-to-noise ratio signal to a selected threshold value;

(b) controlling the effective third-order intercept point (IP3) value of a low noise amplifier (LNA)/mixer channel within the receiver in response to such determinations.

11. The method of claim 10, further including the step of determining the true received signal strength as a pilot signal-to-noise ratio.

12. The method of claim 10, wherein the transceiver is a code division multiple access transceiver.

13. The method of claim 10, wherein controlling the effective IP3 value of the LNA/mixer channel includes increasing bias current to the LNA/mixer channel.

14. The method of claim 10, wherein controlling the effective IP3 value of the LNA/mixer channel includes selecting one of several LNAs having differing IP3 values.

15. A radio frequency transceiver, including a receiver having an associated low noise amplifier (LNA)/mixer channel and a transmitter, and having intelligent control of the linearity of the LNA/mixer channel, including:

(a) signal processing circuitry for indicating a receive mode for the transceiver, the apparent power of a received signal, the true power of the received signal, and the transmit power of the transceiver;

(b) decision logic, coupled to the signal processing circuitry, for determining if the transceiver is in a receive mode, and if interference is present in the receiver based upon the apparent power of the received signal and the true power of the received signal, and if transmit power within the transceiver is high, and if receiver power within the transceiver is low, and for generating a control signal in response to such determinations;

(c) means for controlling the effective third-order intercept point value of the LNA/mixer channel in response to the control signal.

16. The radio frequency transceiver of claim 15, wherein the decision logic determines if interference is present in the receiver by determining if the apparent power of the received signal is significantly greater than the true power of the received signal.

17. The radio frequency transceiver of claim 15, wherein the signal processing circuitry includes an output indicating the apparent power of a received signal as a received signal strength information signal.

18. The radio frequency transceiver of claim 17, wherein the decision logic determines if receiver power within the transceiver is low by comparing the received signal strength information signal to a selected threshold value.

19. The radio frequency transceiver of claim 15, wherein the signal processing circuitry includes an output indicating the true power of a received signal as a pilot signal-to-noise ratio signal.

20. The radio frequency transceiver of claim 19, wherein the decision logic determines if receiver power within the transceiver is low by comparing the pilot signal-to-noise ratio signal to a selected threshold value.

21. The radio frequency transceiver of claim 15, wherein the signal processing circuitry includes an output indicating the transmit power of the transceiver as a transmitter channel automatic gain control signal.

22. The radio frequency transceiver of claim 21, wherein the decision logic determines if transmit power within the transceiver is high by comparing the transmitter channel automatic gain control signal to a selected threshold value.

23. The radio frequency transceiver of claim 15, wherein the transceiver is a code division multiple access transceiver.

24. The radio frequency transceiver of claim 15, wherein the means for controlling the effective third-order intercept point value of the LNA/mixer channel in response to the control signal includes a circuit for increasing bias current to the LNA/mixer channel.

25. The radio frequency transceiver of claim 15, wherein the means for controlling the effective third-order intercept point value of the LNA/mixer channel in response to the control signal includes means for selecting one of several LNAs having differing IP3 values.

26. A radio frequency transceiver, including a receiver having an associated low noise amplifier (LNA)/mixer channel and a transmitter, and having intelligent control of the linearity of the LNA/mixer channel, including:

(a) signal processing circuitry for indicating a receive mode for the transceiver, the apparent power of a received signal as a received signal strength information signal, the true received signal strength of the received signal as a pilot signal-to-noise ratio signal, and the transmit power of the transceiver as a transmit channel automatic gain control signal;

(b) decision logic, coupled to the signal processing circuitry, for generating a control signal in response to determining;

(1) if the transceiver is in a receive mode; and

(2) if interference is present in the receiver by determining if a received signal strength information signal indicating the apparent strength of a signal received by the transceiver is significantly greater than the true received signal strength;

(3) if transmit power within the transceiver is high by comparing the transmit channel automatic gain control signal to a selected threshold value;

(4) if receiver power within the transceiver is low by comparing the pilot signal-to-noise ratio signal to a selected threshold value;

(c) means for controlling the effective third-order intercept point value of the LNA/mixer channel in response to the control signal.

27. The radio frequency transceiver of claim 26, wherein the transceiver is a code division multiple access transceiver.

28. The radio frequency transceiver of claim 26, wherein the means for controlling the effective third-order intercept point value of the LNA/mixer channel in response to the control signal includes a circuit for increasing bias current to the LNA/mixer channel.

29. The radio frequency transceiver of claim 26, wherein the means for controlling the effective third-order intercept point value of the LNA/mixer channel in response to the control signal includes means for selecting one of several LNAs having differing IP3 values.

30. A computer program, residing on a computer-readable medium, for intelligently controlling the linearity of a low noise amplifier (LNA)/mixer channel within a receiver in a radio frequency transceiver, the computer program comprising instructions for causing a processor within the transceiver to:

(a) determine if the transceiver is in a duplex communication mode, and if interference is present in the receiver, and if transmit power within the transceiver is high, and if receiver power within the transceiver is low;

(b) control the effective third-order intercept point (IP3) value of the LNA/mixer channel in response to such determination.