AUTOMATIC GAIN CONTROL METHOD FOR HIGHLY INTEGRATED COMMUNICATION RECEIVER

• US 20020142745A1
• Filed: 08/29/2001
• Published: 10/03/2002
• Est. Priority Date: 03/28/2001
• Status: Active Grant

• Current Assignee: GCT Semiconductor Incorporated
• Original Assignee: GCT Semiconductor Incorporated
• Inventors: Lee, Jeong-Woo, Park, Joonbae, Kang, Suwon
• Granted Patent: US 6,498,927 B2
• Time in Patent Office: Days
• US Class Current: 455/232.1
• CPC Class Codes: H03G 3/3068 Circuits generating control signals for both R.F. and I.F. stages

Abstract

A wireless or wired communication system and method is provided including a transmitter and a receiver. A RF communication system in accordance with the present invention includes an apparatus and gain control method between RF receiver and baseband modem in case of a plurality of gain stages inside a receiver. The gain of each stage can be controlled by an integrated gain controller. The gain controller monitors the signal level of each gain stage to place its gain to optimal value. The gain control apparatus and method can be implemented in a digital AGC system. The gain controller accepts a signal implementing gain control and thus there is no stability issue. When distributed gain stages are present inside a related art receiver and separate gain control loops are used, stability issues can arise. In a preferred embodiment of an apparatus and method, the baseband modem decides the amount of gain control and adjusts the gain of certain gain stages by the proper amount.

Claims

1. A direct conversion communication system, comprising:

a first gain stage that amplifies selected signals among received signals having a carrier frequency;

a demodulation-mixer that mixes the received amplified carrier frequency selected signals and outputs baseband selected signals;

a baseband amplification circuit that includes a plurality of gain stages that receive the baseband selected signals and selectively amplify in-channel signals to a prescribed amplitude; and

a gain controller coupled to receive outputs of the gain stages and to control each of the gain stages, wherein the gain controller controls distributed gain among the gain stages to achieve a prescribed total gain.

2. The communications system of claim 1, wherein the gain controller operates said each of the gain stages in a corresponding linearity range.

3. The communications system of claim 1, wherein an adjacent channel in the baseband selected signals has a greater power level than the in-channel signals upon input to the plurality of gain stages.

4. The communications system of claim 1, wherein the total gain is controlled by a baseband modem and the gain controller to increase a SNR of the system.

5. The communications system of claim 1, further comprising:

an A/D converting unit that converts the selected in-channel signals from the last gain stage of the plurality of gain stages into digital signals; and

a modem gain control circuit that monitors gain of the digital signals received from the AGC and outputs a control signal to the gain controller.

6. The communication system of claim 5, wherein a preset distributed gain level is compared to an actual gain of the digital signals to determine a process error in the gain stages.

7. The communication system of claim 5, wherein the gain controller receives the control signal to change the total gain, and wherein the gain controller distributes the change in the total gain over the gain stages.

8. The communication system of claim 7, wherein the gain controller implements the change in the total gain by adjusting at least one gain stage of the gain stages into a linearity range.

9. The communication system of claim 7, wherein the gain controller implements the change in the total gain by adjusting one of a gain stage closest to an antenna and an initial gain stage of the plurality of gain stages by a prescribed gain step.

10. The communication system of claim 1, wherein the gain controller implements a two tiered gain control, wherein the first tier is implemented in a selected gain stage only once in a prescribed time interval, and wherein the second tier is implemented independent of the prescribed time interval.

11. The communication system of claim 1, further comprising:

an antenna that receives the signals having the carrier frequency;

a RF filter coupled to the antenna that filters the received selected signals;

an A/D converting unit that converts the selected signals from a last gain stage of the plurality of gain stages into digital signals; and

a discrete-time signal processing unit that receives the digital signals.

13. The method of claim 12, wherein the second amplifying comprises sequentially amplifying the selected signals not less than twice, and wherein the first and second output levels are power levels.

14. The method of claim 12, wherein the controlling the gain comprises implementing a gain control of one of the first amplifying and the second amplifying by a single prescribed amount.

15. The method of claim 14, wherein the prescribed amount is one of an increase and a decrease implemented as early as possible prior to digitizing.

16. The method of claim 12, wherein the second amplifying comprises sequentially amplifying the selected signals in a plurality of gain stages, wherein the controlling the gain comprises implementing a gain control of one of the first amplifying and a selected one of the sequentially amplifying the selected signals that is out of an assigned corresponding range of amplification.

17. The method of claim 16, further comprising:

filtering the received selected signals;

low pass filtering each output of the sequentially amplifying steps except for a final sequentially amplifying step;

A/D converting the sequentially amplified selected signals into digital signals; and

discrete-time signal processing the digital signals.

18. The method of claim 12, wherein the communication system is one of a cellular phone, a personal digital assistant, an internet appliance, and remote control device and a laptop computer.

12. A method of operating a communication system, comprising:

receiving signals including selected signals having a carrier frequency;

first amplifying the received selected signals;

detecting a first output level of the first amplified selected signals;

mixing the first amplified selected signals to output demodulated selected signals having a frequency reduced from the carrier frequency;

second amplifying the demodulated selected signals until the selected signals reach a prescribed criteria;

detecting a second output level of the second amplified selected signals;

digitizing the second amplified selected signals;

determining an amplification amount of the digitized selected signals and generating a gain control signal responsive thereto; and

controlling a gain distributed among the first and second amplifying according to the gain control signal and the first and second output levels.