LNA gain adjustment for intermodulation interference reduction

• US 20030181180A1
• Filed: 05/03/2002
• Published: 09/25/2003
• Est. Priority Date: 03/25/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Leete, John, Darabi, Hooman
• Granted Patent: US 6,961,552 B2
• Time in Patent Office: Days
• US Class Current: 455/234.1
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes

Abstract

The radio receiver includes a low noise amplifier that amplifies a received signal to one of three different gain settings. One gain setting is maximum amplification, a second gain setting is 6 dB below maximum amplification and a third gain setting is 32 dB below maximum amplification. In the case of the third setting, the low noise amplifier actually attenuates the received signal by 6 dB. The radio receiver includes a pair of received signal strength indicators that provide received signal strength indications to logic circuitry. Responsive to the received signal strength indications, the logic circuitry generates control commands to the low noise amplifier to prompt it to amplify at one of the three specified levels. Generally, if the received signal has a gain level that exceeds a specified threshold, the low noise amplifier actually attenuates the received signal; otherwise, the level of amplification that is actually provided is a function of the presence of intermodulation interference.

Claims

1. A receiver, comprising:

an input port for receiving wireless communication signals;

amplification circuitry coupled to receive the wireless communication signals from the input port, the amplification circuitry for amplifying the received signal, wherein the amplification circuitry is formed to;

amplify to a first amplification level if no interference signals are detected having a signal strength that exceeds a first threshold value and a desired signal gain for the received signal is below a second threshold value;

amplify to a second amplification level if an interference signal is detected having a signal strength that exceeds the first threshold value and the desired signal gain for the received signal is below the second threshold value;

amplify to a third amplification level if a desired signal gain for the received signal is above the second threshold value; and

down conversion circuitry for down converting the amplified wireless signal coupled to the amplifier circuitry.

2. The receiver of claim 1 wherein the first amplification level is full amplification.

3. The receiver of claim 1 wherein the first amplification level is equal to 26 dB.

4. The receiver of claim 1 wherein the second amplification level is equal to 6 dB less than full amplification.

5. The receiver of claim 1 wherein the second amplification level is equal to 20 dB.

6. The receiver of claim 1 wherein the third amplification level is equal to 32 dB less than full amplification.

7. The receiver of claim 1 wherein the third amplification level is equal to 6 dB of attenuation.

8. The receiver of claim 1 further including a pair of received signal strength indicator circuits (RSSIs) wherein a first RSSI is coupled to detect a combination of the desired signal and interference.

9. The receiver device of claim 2 wherein a second RSSI is coupled to detect a signal strength of the received communication signal.

10. A receiver, comprising:

a low noise amplifier (LNA) coupled to receive wireless communication signals from an antenna and also coupled to receive control signals that specify a corresponding gain level; and

logic circuitry coupled to produce the control signals to the LNA according to the signal strength of the received communication signals and interference in adjacent channels and also coupled to receive an indication of the signal strength of the received signals wherein;

the control signal is to prompt the LNA to provide maximum gain if the received signal strength indications from the first and second received signal strength indicators (RSSIs) are below a first and a second threshold, respectively;

the control signal is to prompt the LNA to provide less than maximum gain if the received signal strength indications from the first and second RSSIs are above the first threshold and below the second threshold, respectively, and

the control signal is to prompt the LNA to provide attenuation to the received signal if the received signal strength indications from the second RSSI is above the second threshold.

11. The receiver of claim 10 further including a first and a second received signal strength indicator (RSSI) coupled to produce received signal strength indications to the logic circuitry.

12. The receiver of claim 11 further including down conversion and oscillation circuitry for down converting the received signal to a base band frequency wherein the first RSSI is coupled to receive a wide band including the down converted signals in the baseband and signals that exist in neighboring channel bands.

13. The receiver of claim 12 further including a low pass filter that is also coupled to receive the down converted signals, the low pass filter defining a corner frequency located approximately at an upper end of the baseband communication channel for filtering signals whose frequency is above the corner.

14. The receiver of claim 13 wherein the second RSSI is coupled to received a low pass filtered output from the low pass filter wherein the second RSSI produces a signal strength indicator reflecting the signal strength for the received communication signals.

15. The receiver of claim 14 wherein the logic circuitry produces a command to prompt the LNA to reduce its gain from its maximal gain amount by 32 dB if the received signal strength indication from the second RSSI is greater than −

40 dBm.

16. The receiver of claim 14 wherein the logic circuitry produces a command to prompt the LNA to reduce its gain from its maximal gain amount by 6 dB if the received signal strength indication from the second RSSI is less than or equal to −

42 dBm and the received signal strength indication from the first RSSI is greater than −

40 dBm.

17. The receiver of claim 14 wherein the logic circuitry produces a command to prompt the LNA to amplify to its maximal gain amount if the received signal strength indication from the second RSSI is less than or equal to −

42 dBm and the received signal strength indication from the first RSSI is less than or equal to −

40 dBm.

18. A method for adjusting a gain level for a low noise amplifier at the front end of a receiver circuit formed on an integrated circuit, comprising:

determining if the gain of a received communication signal exceeds a first specified threshold; and

if the gain of the received communication signal exceeds the first specified threshold, attenuating the received communication signal by a first attenuated amount.

19. The method of claim 18 further including the step of determining if a combination of the received communication signal and any interference signals from neighboring communication channels exceeds a second threshold.

20. The method of claim 19 further including the step of amplifying the received signal a maximum amount only if the gain of the desired signal is below the first threshold and gain of the combination of the received communication signal and any interference signals from neighboring communication channels is equal to or less than a second threshold.

21. The method of claim 19 wherein the first threshold is equal to a minus 42 dBm.

22. The method of claim 19 wherein the second threshold is equal to a minus 40 dBm.

23. The method of claim 18 wherein the first attenuated amount is equal to 32 dBm of attenuation relative to full amplification.

24. The method of claim 18 further including the step of, if the gain of the received communication signal is less than the first threshold amount, determining whether to produce a signal having a second attenuation value relative to full amplification.

25. The method of claim 24 wherein the second attenuation value is equal to 6 dBm.