Receiver with automatic gain control
View Patent ↗An automatic gain control (AGC) system and corresponding method is configured to increase signal to noise which may be referred to as signal to noise ratio in a receiver. The AGC system includes: a signal level detector for determining a signal level for a desired signal; a wideband signal detector for determining a wideband signal level of a wideband signal, the wideband signal being indicative of an interfering signal being present; and a controller coupled to both detectors and configured to provide one or more AGC signals to the receiver to establish a gain setting for the receiver, wherein an initial AGC setting for the receiver is based on the signal level, and AGC adjustments, based e.g., on one or more of the signal level and the wideband signal level, are provided such that an adjusted AGC setting for the receiver increases the signal to noise.
1. A method of increasing signal to noise ratio in a receiver, the method comprising:
obtaining a first signal strength that is indicative of and based on a signal level for a desired signal;
establishing an initial automatic gain control (AGC) setting for the receiver based on the first signal strength;
obtaining a second signal strength that is based on a wideband signal and is indicative of a level of the wideband signal and indicative of an interfering signal being present, the wideband signal including the desired signal, the initial AGC setting is independent from the second signal strength as obtained; and
adjusting the initial AGC setting based on the second signal strength to provide an adjusted AGC setting for the receiver, the adjusted AGC setting will increase the signal to noise ratio of the desired signal relative to the signal to noise ratio resulting from the initial AGC setting.
2. The method of claim 1 wherein the adjusting the initial AGC setting further comprises cutting back the amount of AGC and thus increasing a receiver gain when the interfering signal is not present.
3. The method of claim 1 wherein the adjusting the initial AGC setting based on the second signal strength to provide an adjusted AGC setting for the receiver further comprises cutting back the amount of AGC by an amount that depends on the second signal strength for the wideband signal.
4. The method of claim 1 wherein the obtaining the second signal strength is responsive to the first signal strength.
5. The method of claim 4 wherein the obtaining the second signal strength is only undertaken when the first signal strength is within a predetermined range.
6. The method of claim 1 further comprising identifying a channel for the desired signal and storing the adjusted AGC setting and the channel in a memory and thereafter whenever the receiver is tuned to another channel and then is retuned to the channel, accessing the memory and applying the adjusted AGC setting to the receiver.
7. The method of claim 6 wherein the receiver is a frequency hopping receiver that is tuned to a multiplicity of channels and wherein a corresponding multiplicity of AGC settings are respectively stored together with the multiplicity of channels.
8. The method of claim 6 further comprising reverting to the initial AGC setting at any time the interfering signal is present.
9. The method of claim 6 further comprising progressively adjusting the initial AGC setting with incremental adjustments occurring as the receiver is repetitively retuned to the channel.
10. An automatic gain control (AGC) system configured to increase signal to noise ratio in a receiver, the AGC system comprising:
a signal level detector for determining a signal level for a desired signal;
a wideband signal detector for determining a wideband signal level of a wideband signal, the wideband signal including the desired signal and being indicative of an interfering signal being present; and
a controller coupled to the signal level detector and the wideband signal detector and configured to provide one or more AGC signals to the receiver to establish a gain setting for the receiver, wherein an initial AGC setting for the receiver is based on the signal level and independent from the wide band signal level, the controller further configured to adjust the initial AGC setting based on the wideband signal level to provide an adjusted AGC setting for the receiver, the adjusted AGC setting increasing the signal to noise ratio for the desired signal relative to the signal to noise ratio resulting from the initial AGC setting.
11. The AGC system of claim 10 wherein the controller is further configured to adjust the initial AGC setting by providing the AGC signals such that the gain of one or more amplifiers in the receiver is increased when the interfering signal is not present.
12. The AGC system of claim 10 wherein the controller is further configured to adjust the initial AGC setting based on the wideband signal level to provide an adjusted AGC setting for the receiver by providing the one or more AGC signals such that the gain of one or more amplifiers in the receiver is increased by an amount that depends on the wideband signal level.
13. The AGC system of claim 10 wherein the wideband signal detector is only operational when the signal strength is within a predetermined range.
14. The AGC system of claim 10 further comprising a memory and wherein the controller is coupled to the memory and configured to store the adjusted AGC setting in the memory and whenever the receiver is retuned to a channel corresponding to the desired signal, accessing the memory and applying the adjusted AGC setting to the receiver.
15. The AGC system of claim 14 wherein the receiver is a frequency hopping receiver that is tuned to a multiplicity of channels and wherein the controller is configured such that a corresponding multiplicity of AGC settings are stored in the memory and respectively associated with the multiplicity of channels.
16. The AGC system of claim 14 wherein the controller is further configured to revert to the initial AGC setting at any time the interfering signal detector determines that the interfering signal is present.
17. The AGC system of claim 10 wherein the controller is further configured to progressively adjust the initial AGC setting with incremental adjustments occurring as the receiver is repetitively retuned to a channel corresponding to the desired signal.
18. The AGC system of claim 17 wherein the controller is further configured to progressively adjust a backoff count as the receiver is repetitively retuned to a channel and use the backoff count to determine each of the incremental adjustments, wherein a given incremental adjustment is determined for a first tuning to the channel and is applied to provide the adjusted AGC setting for a subsequent tuning to the channel.
19. The AGC system of claim 18 wherein the controller is further configured to progressively adjust the backoff count by a step size that depends on the wideband signal level.
20. A receiver system configured for improved signal to noise ratio comprising:
a Global System for Mobile Enhanced Data Rate (EDGE) receiver including a plurality of variable gain amplifiers;
a signal level detector for determining a signal level for a desired signal;
a wideband signal detector for determining a wideband signal level that is indicative of whether an interfering signal is present; and
a controller coupled to the signal level detector and the wideband signal detector and configured to provide an AGC signal to each of the plurality of variable gain amplifiers to establish a gain setting for the receiver, wherein an initial AGC setting for the receiver is based on the signal level and is independent from the wideband signal level, and wherein the controller is further configured to adjust the initial AGC setting to provide an adjusted AGC setting for the receiver based on the wideband signal level if the signal level is within a predetermined range, the adjusted AGC setting increasing the signal to noise ratio for the desired signal relative to the signal to noise ratio resulting from the initial AGC setting in the EDGE receiver.
21. The receiver system of claim 20 further comprising a memory and wherein the EDGE receiver is operable to receive the desired signal in accordance with a frequency hopped protocol wherein an adjusted AGC setting corresponding to each of a plurality of frequencies is stored in the memory and used as the EDGE receiver is retuned to each of the plurality of frequencies.
22. The receiver system of claim 20 wherein the controller is further configured to provide a final AGC setting for a given operating frequency of the receiver by progressively adjusting, as the receiver is repetitively tuned to one or more other operating frequencies and then retuned to the given operating frequency, a present AGC setting through a series of adjustments to provide the final AGC setting.