Receiver having gain control and narrowband interference detection

• US 6,804,501 B1
• Filed: 09/25/2000
• Issued: 10/12/2004
• Est. Priority Date: 09/25/2000
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Prairiecomm Inc. (NXP Semiconductors NV)
• Inventors: Bradley, Wayne H., Diehl, John W.
• Primary Examiner(s): CRAVER, CHARLES R
• Application Number:
  US09/669,015
• Time in Patent Office: 1,478 Days
• Field of Search: 455/226--22, 455/232.1, 455/234.1, 455/234.2, 455/240.1, 455/241.2, 455/245.1, 455/253.2, 455/67.11, 455/63.1, 455/251.1, 455/241.1, 455/138, 455/139
• US Class Current: 455/138
• CPC Class Codes: H03G 3/3036 in high-frequency amplifiers or in frequency-changers H03G3/3052, H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input
• CPC Class Codes: H04B 17/318 Received signal strength

Abstract

A receiver generates two metrics, one that is used to control the gain of an amplifier and the other that is used to determine the presence of narrowband interference, such as IMD. The two metrics may represent analog-to-digital converter (A/D) saturation and average signal strength, either of which may be used to control gain or to detect the presence of narrowband interference.

Claims

1. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal;

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the signal strength metric with a prior value of the signal strength metric to determine whether the first amplifier should be set to the fixed gain setting and is further adapted to set the first amplifier to the fixed gain setting when the current value of the signal strength metric is substantially equal to the prior value of the signal strength metric.

2. The automatic gain controller of claim 1, wherein the signal strength determiner processes the digital information by summing a number of absolute values of analog signal levels represented by the digital information and dividing the sum by the number of absolute values over which the sum was taken to produce the signal strength metric.

3. The automatic gain controller of claim 1, wherein the signal strength determiner processes the digital information by summing a number of squared values of analog signal levels represented by the digital information and dividing the sum by the number of squared values over which the sum was taken to produce the signal strength metric.

4. The automatic gain controller of claim 1, wherein the signal strength determiner processes the digital information by summing a number of squared absolute values of analog signal levels represented by the digital information and dividing the sum by the number of squared absolute values over which the sum was taken to produce the signal strength metric.

5. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the signal strength metric with a prior value of the signal strength metric to determine whether the first amplifier should be set to the fixed gain setting and is further adapted to set the first amplifier to the unity gain setting when the current value of the signal strength metric is not substantially equal to the prior value of the signal strength metric.

6. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal;

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the signal strength metric with a prior value of the signal strength metric to determine whether the first amplifier should be set to the fixed gain setting and wherein the prior value of the signal strength metric is determined when the first amplifier is set to the unity gain setting and the current value of the signal strength metric is determined when the first amplifier is set to the fixed gain setting.

7. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal;

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the signal strength metric with a prior value of the signal strength metric to determine whether the first amplifier should be set to the fixed gain setting and wherein the prior value of the signal strength metric is determined when the first amplifier is set to the fixed gain setting and the current value of the signal strength metric is determined when the first amplifier is set to the unity gain setting.

8. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal,

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the threshold satisfaction metric with a prior value of the threshold satisfaction metric to determine whether the first amplifier should be set to the fixed gain setting and wherein the gain adjuster is adapted to set the first amplifier to the fixed gain setting when the current value of the threshold satisfaction metric is substantially equal to the prior value of the threshold satisfaction metric.

9. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal;

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the threshold satisfaction metric with a prior value of the threshold satisfaction metric to determine whether the first amplifier should be set to the fixed gain setting and wherein the gain adjuster is adapted to set the first amplifier to the unity gain setting when the current value of the threshold satisfaction metric is not substantially equal to the prior value of the threshold satisfaction metric.

10. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal;

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the threshold satisfaction metric with a prior value of the threshold satisfaction metric to determine whether the first amplifier should be set to the fixed gain setting and wherein the prior value of the threshold satisfaction metric is determined when the first amplifier is set to unity gain and the current value of the threshold satisfaction metric is determined when the first amplifier is set to the fixed gain setting.

11. An automatic gain controller for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a signal strength determiner adapted to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal;

a threshold comparator adapted to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

an accumulator communicatively coupled to the threshold comparator and adapted to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a gain adjuster communicatively coupled to the signal strength determiner, the accumulator, the first amplifier and the second amplifier, the gain adjuster adapted to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the gain adjuster is adapted to compare a current value of the threshold satisfaction metric with a prior value of the threshold satisfaction metric to determine whether the first amplifier should be set to the fixed gain setting and wherein the prior value of the threshold satisfaction metric is determined when the first amplifier is set to the fixed gain setting and the current value of the threshold satisfaction metric is determined when the first amplifier is set to unity gain.

12. An automatic gain control method for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the method comprising the steps of:

producing a first metric representative of a signal strength of the broadcast signal;

producing an indicator signal representative of a magnitude of the digital information in comparison to a threshold;

processing the indicator signal to determine a historical probability that the digital information exceeds the threshold to produce a second metric representative of an average signal strength of the signal; and

selectively switching the first amplifier between the fixed gain setting and the unity gain setting and varying the gain of the second amplifier based on the first metric and the second metric, wherein comparing a current value of the first metric with a prior value of the first metric is performed to determine whether the first amplifier should be set to the fixed gain setting, wherein selectively switching comprises switching the first amplifier to the unity gain setting when the current value of the first metric is not substantially equal to the prior value of the first metric.

13. The method of claim 12, wherein the step of producing the first metric includes the step of calculating an average signal strength based on the digital information.

14. The method of claim 12, wherein the step of selectively switching includes the steps of:

storing a first value of the second metric;

switching the first amplifier between the unity gain setting and the fixed gain setting;

determining a second value of the second metric; and

comparing the first value of the second metric to the second value of the second metric.

15. The method of claim 12, wherein the step of selectively switching includes the steps of:

storing a first value of the first metric;

switching the first amplifier between the unity gain setting and the fixed gain setting;

determining a second value of the first metric; and

comparing the first value of the first metric to the second value of the first metric.

16. An automatic gain control method for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the method comprising the steps of:

producing a first metric representative of a signal strength of the broadcast signal;

producing an indicator signal representative of a magnitude of the digital information in comparison to a threshold;

processing the indicator signal to determine a historical probability that the digital information exceeds the threshold to produce a second metric representative of an average signal strength of the signal; and

selectively switching the first amplifier between the fixed gain setting and the unity gain setting and varying the gain of the second amplifier based on the first metric and the second metric, wherein comparing a current value of the first metric with a prior value of the first metric is performed to determine whether the first amplifier should be set to the fixed gain setting, wherein selectively switching comprises the step of switching the first amplifier to the fixed gain setting when the current value of the first metric is substantially equal to the prior value of the first metric.

17. An automatic gain control method for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the method comprising the steps of:

producing a first metric representative of a signal strength of the broadcast signal;

producing an indicator signal representative of a magnitude of the digital information in comparison to a threshold;

processing the indicator signal to determine a historical probability that the digital information exceeds the threshold to produce a second metric representative of an average signal strength of the signal; and

selectively switching the first amplifier between the fixed gain setting and the unity gain setting and varying the gain of the second amplifier based on the first metric and the second metric, wherein selectively switching comprises comparing a current value of the second metric with a prior value of the second metric to determine whether the first amplifier should be set to the fixed gain setting and wherein selectively switching comprises switching the first amplifier to the unity gain setting when the current value of the second metric is not substantially equal to the prior value of the first metric.

18. An automatic gain control method for use with a receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the method comprising the steps of:

producing a first metric representative of a signal strength of the broadcast signal;

producing an indicator signal representative of a magnitude of the digital information in comparison to a threshold;

processing the indicator signal to determine a historical probability that the digital information exceeds the threshold to produce a second metric representative of an average signal strength of the signal; and

selectively switching the first amplifier between the fixed gain setting and the unity gain setting and varying the gain of the second amplifier based on the first metric and the second metric, wherein selectively switching comprises comparing a current value of the second metric with a prior value of the second metric to determine whether the first amplifier should be set to the fixed gain setting and wherein selectively switching comprises switching the first amplifier to the fixed gain setting when the current value of the second metric is substantially equal to the prior value of the first metric.

19. An automatic gain controller for use with a receiver having a processor, the receiver adapted to receive a broadcast signal having digital information encoded therein, the receiver including a first amplifier having a fixed gain setting and a unity gain setting, a second amplifier cascaded with the first amplifier, the second amplifier having a variable gain, the automatic gain controller comprising:

a memory communicatively coupled to the processor;

a first routine stored on the memory for causing the processor to process the digital information to produce a signal strength metric representative of an average signal strength of the broadcast signal;

a second routine stored on the memory for causing the processor to process the digital information to produce a threshold satisfaction indication representative of a magnitude of the digital information in comparison to a threshold;

a third routine stored on the memory for causing the processor to process the threshold satisfaction indication to determine a historical probability that the digital information exceeds the threshold to produce a threshold satisfaction metric; and

a fourth routine stored on the memory for causing the processor to selectively switch the first amplifier between the fixed gain setting and the unity gain setting and to vary the gain of the second amplifier based on the signal strength metric and the threshold satisfaction metric, wherein the fourth routine, when executed, causes the processor to compare a current value of the signal strength metric with a prior value of the signal strength metric to determine whether the first amplifier should be set to the fixed gain setting and to set the first amplifier to the fixed gain setting when the current value of the signal strength metric is substantially equal to the prior value of the signal strength metric.

20. The gain controller of claim 19, wherein the fourth routine is further adapted to cause the processor to compare a current value of the second metric with a prior value of the second metric to determine whether the first amplifier should be set to the fixed gain setting.

21. The gain controller of claim 19, wherein the fourth routine is further adapted to cause the processor to store a first value of the second metric, to switch the first amplifier between the unity gain setting and the fixed gain setting, to determine second value of the second metric and to compare the first value of the second metric to the second value of the second metric.

22. The gain controller of claim 19, wherein the fourth routine is further adapted to cause the processor to store a first value of the first metric, to switch the first amplifier between the unity gain setting and the fixed gain setting, to determine second value of the first metric and to compare the first value of the first metric to the second value of the first metric.