Method and device to control the gain of a radio receiver
An automatic gain control (AGC) method and system for a radio receiver are proposed in which the ACG comprises two AGC loops; a first loop controlling signal gain in the analog portion of the radio receiver, a second loop controlling gain in the digital domain after digitization of the received signal. The analog AGC loop has a slower response time than the digital AGC loop. When applied to a multi-branch diversity receiver, each branch has its own digital AGC loop, but the analog gain can be common to all branches, based on measurement of the analog signal in each branch.
1. An Automatic Gain Control system for a radio receiver having at least one receiving signal path with an analogue and a digital portion, the Automatic Gain Control system comprising:
at least two Automatic Gain Control loops,
wherein at least one first Automatic Gain Control loop comprises a first AGC circuit and is configured to control the gain of at least one analogue signal amplifier located in the analogue portion of the receiver and wherein the first Automatic Gain Control loop has a first cycle time (t 1 ),
wherein at least one second Automatic Gain Control loop comprises a second AGC circuit and is configured to control signal amplification of at least one signal processing unit in the digital portion of the receiver and wherein the second Automatic Gain Control loop has a second cycle time (t 2 ); and
wherein the second cycle time (t 2 ) is shorter than the first cycle time (t 1 ); and
wherein the first AGC circuit controls the gain of the at least one analogue signal amplifier prior to the at least one second automatic gain control loop controlling the digital amplification of the at least one digital signal processing unit.
2. The system according to claim 1 ,
wherein the radio receiver is a multi-branch receiver having at least two parallel receiving signal paths, and
wherein each receiving signal path comprises at least one first Automatic Gain Control loop and at least one second Automatic Gain Control loop.
3. The system according to claim 2 ,
wherein in each receiving signal path the at least one first Automatic Gain Control loop is set by the same gain control signal.
4. The system according to claim 1 ,
wherein the system is located in a receiving signal path of a mobile communication device or a mobile station.
5. The system according to claim 4 ,
wherein the mobile communication device or station comprises a receiver for at least one of a wireless communication systems, wireless local loops, wireless LAN applications, and/or cellular systems in accordance with at least one of the following communication standards UMTS, WCDMA, UTRATDD, UTRAFDD, TDSCDMA, CDMA2000, and OFDMA.
6. The system according to claim 4 ,
wherein the mobile communication device or station is a device capable for High Speed Downlink Packet Access.
7. A method for Automatic Gain Control (AGC) in a radio receiver having at least one receiving signal path with an analogue and a digital portion, the method comprising:
at least one first analogue amplifying step, in which an analogue receiving signal is amplified in the analogue portion, wherein the analog portion comprises a first AGC circuit in a first feedback loop;
digitizing the amplified analogue receiving signal into a digitized receiving signal;
at least one second digital amplifying step, in which the digitized receiving signal is digitally amplified in the digital portion, wherein the digital portion comprises a second AGC circuit and a second feedback loop;
controlling a first gain for said first analogue amplifying step based on a first cycle time (t 1 ), and
controlling a second gain for said second digital amplifying step based on a second cycle time (t 2 ),
wherein the second cycle time (t 2 ) is shorter than first cycle time (t 1 ).
8. The method according to claim 7 ,
wherein the method comprises processing of several receiving signals in a multi-branch receiver having at least two parallel receiving signal paths, and
wherein the step of controlling the first gain comprises determining one common analogue gain control value in each branch.
9. A method according to claim 7 ,
wherein the second cycle time (t 2 ) is by orders of magnitude shorter than the first cycle time (t 1 ).
10. A method according to claim 7 ,
wherein the method further comprises controlling the first gain independently of the first cycle time (t 1 ) based on determining if there is a predetermined change in receiving conditions.
11. A nontransitory processor-readable storage medium comprising program instructions that, when performed on a programmable processor, cause the programmable processor to perform a method for Automatic Gain Control (AGC) in a radio receiver having at least one receiving signal path with an analogue and a digital portion, the method comprising:
at least one first analogue amplifying step, in which an analogue receiving signal is amplified in the analogue portion, wherein the analog portion comprises a first AGC circuit in a first feedback loop;
digitizing the amplified analogue receiving signal into a digitized receiving signal;
at least one second digital amplifying step, in which the digitized receiving signal is digitally amplified in the digital portion, wherein the digital portion comprises a second AGC circuit and a second feedback loop;
controlling a first gain for said first analogue amplifying step based on a first cycle time (t 1 ), and
controlling a second gain for said second digital amplifying step based on a second cycle time (t 2 ),
wherein the second cycle time (t 2 ) is shorter than first cycle time (t 1 ).